Document Columbiacountyga_doc_b58f83a89a_1

iii 2016 Edition MANUAL FOR EROSION AND SEDIMENT CONTROL IN GEORGIA 2016 Edition Georgia Soil and Water Conservation Commission P.O. Box 8024 4310 Lexington Rd Athens, GA 30603 [PHONE REDACTED] [PHONE REDACTED] fax ---PAGE BREAK--- iv 2016 Edition The preparation of this Manual was financed in part through a grant from the U.S. Environmental Protec­ tion Agency to the Environmental Protection Division of the Georgia Department of Natural Resources under Provisions of Section 319(h) of the Federal Water Pollution Control Act, as amended. All programs and services of the federal, state and local agencies listed above are avaiable on a nondis­ criminatory basis without regard to race, color, national origin, religion, sex, age, marital status, handicap or disability. If you need this document in an alternative format, call [PHONE REDACTED]. ---PAGE BREAK--- v 2016 Edition PREFACE TO THE 2016 EDITION The 2016 Edition of the “Manual for Erosion and Sediment Control in Georgia” has been revised with a focus on erosion control. Implementation of newly researched practices has been incorporated to expand on the traditional erosion and sediment control practices which are included in the 2016 Edition. These new practices have been proven to aid in controlling erosion and subsequent sedimentation in a cost-effective manner. It is important that this publication is used as a guideline and that “creativity” must be utilized when necessary to fully protect a site from erosion and subsequent sedimentation. What is required on erosion and sediment control plans has been modified and includes the current plan review checklists with guidance documents. The 2016 Edition includes new BMPs and a process for Alternative BMPs to be included on the Equivalent BMP list. This application and removal process is found in Appendix A-2. The Manual has also been revised to include an updated Erosion and Sedimentation Control Plan. It is hoped that users of this Manual will realize the significant changes and recognize that technology changes rapidly in the erosion and sediment control arena. The Commission is dedicated to providing the State of Georgia with the latest “proven” erosion and sediment control practices. The Commission is appreciative of all of the help and guidance received during the revision of the Manual. Many thanks go to the Georgia Department of Transportation, Natural Resources Conservation Service, DNR Environmental Protection Division, DNR Wildlife and Fisheries. A special thanks to the Overview Council: Terry England, Chair of Overview Council, State Repre­ sentative for the 116th House District; Robert Brant Lane, Hodges, Harbin, Newberry and Tribble, Inc.; Bert M. Brantley, State Road and Tollway Authority; John B. Harrison, Jr., Baldwin Paving Co., Inc,; Ronny Just, Georgia Power; Marc Mastronardi, GA DOT; Tom McCall, State Representative for the 33rd House District; Mary Walker, GA EPD; and the Carl Vinson Institute of Government at the University of Georgia. Technical Editors: Benton Ruzowicz, J. Guerry Thomas, Lauren and Brady Hart. ---PAGE BREAK--- vi 2016 Edition ---PAGE BREAK--- vii 2016 Edition Perhaps the most harmful damage to Georgia’s land and water resources is incurred through unchecked and uncorrected erosion and sediment deposition. Years of work have done much to remedy the situation. There has also been created an awareness that efforts must continue to further reduce the volume of the sediment pollution in all the state’s waters. While ongoing work in soil and water conservation has been of considerable success, it was recognized that some state regulation of land-disturbing activities could add a needed dimension to the overall control effort. The General Assembly responded to this need, and in 1975, the Erosion and Sedimentation Act (O.C.G.A. § 12-7-1 et seq.) was passed. The Act has been amended several times since then. The Act requires counties and municipalities to have erosion and sediment control ordinances or be cov­ ered under state regulations. While the Soil and Water Conservation Districts provide assistance in this at the local level, the State Soil and Water Conservation Commission provides expert, step-by-step guidance for activities under such ordinances through a comprehensive publication of reference information. Thus the “Manual for Erosion and Sediment Control in Georgia” can serve as a technical guide in formulating plans for land-disturbing activities. In preparing the manual, the State Conservation Commission is indebted to the many hundreds of researchers, engineers, farmers, conservationists and others who, over the years, made possible the accumulation of information on modern conservation. The criteria, standards and specifications contained in Chapter 6 must be incorporated into all local ero­ sion and sediment control programs. The remaining chapters and sections of this Manual contain guidelines and support materials to assist users in the implementation of best management practices in accordance with the provisions of the Erosion and Sedimentation Act. FOREWORD ---PAGE BREAK--- viii 2016 Edition ---PAGE BREAK--- ix 2016 Edition TABLE OF CONTENTS Page PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v FOREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii CHAPTER 1 The Erosion and Sedimentation Act of 1975. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 CHAPTER 2 Sediment and Erosion Control Processes, Principles and Practices. . . . . . . . . . . 2-1 CHAPTER 3 Planning and Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 CHAPTER 4 Local Programs: Principles and Processes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 CHAPTER 5 Sources of Assistance and Resource Information. . . . . . . . . . . . . . . . . . . . . . . . . 5-1 CHAPTER 6 BMP Standards and Specifications for General Land-Disturbing Activities. . . . . . 6-1 APPENDIX A-1 Estimating Runoff from Urban Areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1 APPENDIX A-2 Joining the Equivalent BMP List: Application and Removal Process. . . . . . . . . . . A-2 APPENDIX B-1 Soil Series Interpretations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1-1 APPENDIX B-2 Soil Loss Predictions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-2-1 APPENDIX C Construction Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1 APPENDIX D Model Soil Erosion and Sedimentation Control Ordinance. . . . . . . . . . . . . . . . . . D-1 APPENDIX E Conversion Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-1 APPENDIX F Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-1 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G-1 ---PAGE BREAK--- x 2016 Edition ---PAGE BREAK--- 2016 Edition 1-1 On April 24, 1975, the Honorable George Bus­ bee, Governor of the State of Georgia, signed into law as Act 599, the Erosion and Sedimentation (E&S) Act of 1975 (O.C.G.A. § 12-7-1 et. seq.) This landmark legislation was the result of over five years of exhausting work, debate and legislative compromise. With the passage of the Act, Georgia joined the few far-sighted states adopting legislation specifi­ cally designed to protect soil and water resources. Georgia’s E&S Act shows great concern for local implementation and local enforcement. There ex­ ists in Georgia a mechanism whereby local decision makers can do something about the abuses of soil and water resources. O.C.G.A. § 12-7-2 states: “It is found that soil erosion and sediment deposition onto lands and into waters within the watersheds of this state are occurring as a result of widespread failure to apply proper soil erosion and sedimentation control prac­ tices in land clearing, soil movement and construc­ tion activities, and that such erosion and sediment deposition result in pollution of state waters and damage to domestic, agricultural, recreational, fish and wildlife, and other resource uses. It is, there­ fore, declared to be the policy of this state and the intent of this chapter to strengthen and extend the present erosion and sediment control activities and programs of this state and to provide for the establishment and implementation of a state-wide comprehensive soil erosion and sediment control program to conserve and protect land, water, air and other resources of this state.” Sediment in Georgia comes from many sources including agricultural operations, forestry practices, construction projects and other activities that con­ vert land from one use to another. Historically, farm land has been the greatest source of sediment. The trend was reversed around the midpoint of the century with much idle land or land in row crops planted to perennial grasses or trees. In 2007, the Annual Natural Resources CHAPTER 1 THE EROSION AND SEDIMENTATION ACT OF 1975 Figure 1.1 - Advanced gully erosion on an abandoned construction site. Inventory, conducted by the Natural Resources Conservation Service (NRCS), showed a continu­ ing trend in reduced soil erosion of croplands. Between 1982 and 2007, soil erosion from wind and water on U.S. cropland (on non-Federal land) decreased 43%. In 1982, the total was 3.06 billion tons and in 2007, the total was 1.73 billion tons. Urban development is now a major source of sedimentation and pollutants into waters of the State. The increased impervious cover due to de­ velopments also increases runoff and stream flows which cause stream bank erosion, and increases the elevation of the floodplain. Erosion damage is costly to repair, often requir­ ing regrading or replacement of eroded soil and re­ placement of damaged pavements and structures. Sediment damages are not only unnecessary, but extremely costly. Georgia’s Soil and Water Conservation Districts (SWCD) have been charged with performing a vital role in the implementation of Act 599. Since their formation beginning in 1937, the districts have worked toward treating each acre of land in accordance with its capabilities. The Districts, and the District Supervisors for each county in Geor­ gia can be found on the Georgia Soil and Water Conservation Commission website at The Manual for Erosion and Sediment Control in Georgia deals primarily with land-disturbing ac­ tivities in urban and urbanizing areas. It should be remembered that the same methodology and ex­ pertise is required in planning for the conservation of soil and water on any lands. The Manual for Best Management Practices for Georgia Agriculture is ---PAGE BREAK--- 2016 Edition 1-2 available on the website, and the Manual for Forestry BMPs is available from the Georgia Forestry Commission. PROVISIONS UNDER ACT 599 Act 599 requires that governing authorities of Georgia’s 159 counties and more than 550 incorporated municipalities adopt comprehen­ sive ordinances governing land-disturbing activi­ ties within their boundaries. The ordinances must contain technical principles as provided in the law and procedures for issuance of permits. All Erosion, Sedimentation & Pollution Control Ordinances must be reviewed and approved by the Environmental Protect Division (GA EPD) of the Georgia Department of Natural Resources (DNR). A model ES&PC Ordinance can be found on both the and GA EPD websites, and http://epd.georgia.gov/. Local ordinances must meet or exceed the standards, requirements, and provisions of the E&S Act and the state general permit (NPDES). The ordinance may not exceed the NPDES permit requirements for monitoring, reporting, inspections, design standards, turbidity standards, education and training, and project size thresholds with regard to education and training requirements. The law could have a significant impact on any area’s natural resource base because it requires detailed planning before land-disturbing activities are undertaken. The law requires that erosion and sediment control plans for each non-exempt activ­ ity be prepared and submitted with application to the Local Issuing Authority (LIA) for a permit. The plans will then be forwarded to the appropriate Soil and Water Conservation District. The District shall have 35 days to approve or deny the plan with the reason for denial. With each resubmittal of the plan, the 35 days for review starts again. The plan review would bypass District approval if the LIA demonstrates that it possesses the capability and expertise to conduct erosion and sediment control plan reviews and enters into an agreement with the District. After a thorough analysis of the plans, they will be returned to the issuing authority with the District’s recommendations upon which the issu­ ing authority will issue or deny permits. Should a permit be denied because of a discrepancy in the plans, such discrepancies must be made apparent to the applicant. The law requires that a permit be issued or denied within a period not to exceed 45 days after the plan and applications are submitted. If a permit is denied there are appeal procedures provided for in the Act. Municipalities and counties failing to have ad­ opted an E&S Ordinance will be subject to rules and regulations developed by the GA EPD. GA EPD does not issue Land Disturbance Per­ mits. The terms of the NPDES permit will apply and be enforced by GA EPD. Coverage under the state general permit will begin fourteen days after submitting a Notice of Intent (NOI), and the required fees to the appropriate GA EPD office. It is recom­ mended that the applicant reads and understands the appropriate NPDES permit. In 2003, the E&S Act was amended requiring all persons involved in land development design, review, permitting, construction, monitoring, or in­ Figure 1.2 - Maintaining outlet protection due to BMP failures higher in the drainage basin. Figure 1.3 - If unchecked, sediment would gradually fill up this lake. ---PAGE BREAK--- 2016 Edition 1-3 spection or any land-disturbing activity to meet the education and training certification requirements developed by the To meet the requirements of O.C.G.A. § 12-7-19, has developed the following four levels of certification: 1 Level I Awareness Seminar, a two hour class which is for sub-contractors. 2 Level IA Fundamentals Seminar, an eight hour class for persons installing and/or inspecting BMPs. 3 Level IB Advanced Fundamentals Seminar, a sixteen-hour class for regulatory inspectors and non-regulatory personnel contracted to conduct regulatory work. 4 Level II Introduction to Design Seminar, a sixteen hour class for persons designing and/or reviewing ES&PC plans. LAND-DISTURBING ACTIVITY: Any activity which may result in soil erosion from water or wind and the movement of sedi­ ments into state waters or onto lands within the state, including, but not limited to: 1. clearing 2. dredging 3. grading 4. excavating 5. transporting 6. filling ---PAGE BREAK--- 2016 Edition 1-4 EXEMPTIONS FROM THE ACT O.G.C.A. § 12-7-17 LAND DISTURBING ACTIVITY DOES NOT INCLUDE: 1. Surface mining, as the same as defined in Code Section 12-4-72 2. Granite quarrying and land clearing for such quarrying. 3. Minor land-disturbing activities, such as home gardens and individual home landscaping, repairs, maintenance work, fences, and other related activities which result in minor soil erosion* 4. The construction of single-family resi­ dences, when such construction disturbs less than one acre and is not a part of a larger common plan of development or sale with a planned disturbance of equal to or greater than one acre and not otherwise exempted under this paragraph; provided, however, that construction of any such residence shall conform to the minimum requirements as set forth in subsection of Code Section 12-7-6 and this para­ graph. For single-family residence construction covered by the provisions of this para­ graph, there shall be a buffer zone between the residence and any state waters classi­ fied as trout streams pursuant to Article 2 of Chapter 5 of this title. In any such buffer zone, no land-disturbing activity shall be constructed between the residence and the point where vegetation has been wrested by normal stream flow or wave action from the banks of the trout waters. For primary trout waters, the buffer zone shall be at least 50 horizontal feet, and no variance to a smaller buffer shall be granted. For secondary trout waters, the buffer zone shall be at least 50 horizontal feet, but the director may grant variances to no less than 25 feet. Regardless of whether a trout stream is primary or secondary, for first order trout waters, which are streams into which no other streams flow except for springs, the buffer shall be at least 25 horizontal feet, and no variance to a smaller buffer shall be granted. The minimum re­ quirements of subsection of Code Sec­ tion 12-7-6 and the buffer zones provided by this paragraph shall be enforced by the issuing authority 5. Agricultural operations as defined in Code Section 1-3-3 to include those prac­ tices involving the establishment, cultiva­ tion, or harvesting of products of the field or orchard; the preparation and planting of pasture land; farm ponds; dairy opera­ tions; livestock and poultry management practices; and the construction of farm buildings 6. Forestry land management practices, including harvesting; provided, however, that when such exempt forestry practices cause or result in land-disturbing or other activities otherwise prohibited in a buffer, as established in paragraphs (15) and (16) of subsection of Code Section 12-7-6, no other land-disturbing activities, except for normal forest management practices, shall be allowed on the entire property upon which the forestry practices were conducted for a period of three years after the completion of such forestry practices 7. Any project carried out under the technical supervision of the Natural Resources Conservation Service of the United States Department of Agriculture 8. Any project involving less than one acre of disturbed area; provided, how­ ever, that this exemption shall not apply to any land-disturbing activity within a larger common plan of development or sale with a planned disturbance of equal to or greater than one acre or within 200 feet of the bank of any state waters, and for purposes of this paragraph, “state waters” excludes channels and drainage­ ways which have water in them only dur­ ing and immediately after rainfall events and intermittent streams which do not have water in them year round; provided, however, that any person responsible ---PAGE BREAK--- 2016 Edition 1-5 for a project which involves less than one acre, which involves land-disturbing activity, and which is within 200 feet of any such excluded channel or drainage­ way must prevent sediment from moving beyond the boundaries of the property on which such project is located and provided, further, that nothing contained in this chapter shall prevent a city or county which is a Local Issuing Authority from regulating any such project which is not specifically exempted by paragraph or (10) of this Code section; 9. Construction or maintenance proj­ ects, or both, undertaken or financed in whole or in part, or both, by the De­ partment of Transportation, the Geor­ gia Highway Authority, or the State Road and Tollway Authority; or any road construction or maintenance proj­ ect, or both, undertaken by any county or municipality; provided, however, that construction or maintenance projects of the Department of Transportation or the State Road and Tollway Authority which disturb one or more contiguous acres of land shall be subject to the provisions of Code Section 12-7-7.1; except where the Department of Transportation, the Georgia Highway Authority, or the State Road and Tollway Authority is a second­ ary permittee for a project located within a larger common plan of development or sale under the state general permit, in which case a copy of a Notice of Intent under the state general permit shall be submitted to the Local Issuing Authority, the Local Issuing Authority shall enforce compliance with the minimum require­ ments set forth in Code Section 12-7-6 as if a permit had been issued, and viola­ tions shall be subject to the same penal­ ties as violations by permit holders**. 10. Any land-disturbing activities conduct­ ed by any electric membership corpora­ tion or municipal electrical system or any public utility under the regulatory jurisdiction of the Public Service Com­ mission, any utility under the regulatory ju­ risdiction of the Federal Energy Regulatory Commission, any cable television system as defined in Code Section 36-18-1, or any agency or instrumentality of the United States engaged in the generation, trans­ mission, or distribution of power; except where an electric membership corporation or municipal electrical system or any public utility under the regulatory jurisdiction of the Public Service Commission, any util­ ity under the regulatory jurisdiction of the Federal Energy Regulatory Commission, any cable television system as defined in Code Section 36-18-1, or any agency or in­ strumentality of the United States engaged in the generation, transmission, or distribu­ tion of power is a secondary permittee for a project located within a larger common plan of development or sale under the state general permit, in which case the Local Issuing Authority shall enforce compliance with the minimum requirements set forth in Code Section 12-7-6 as if a permit had been issued, and violations shall be sub­ ject to the same penalties as violations by permit holders**. 11. Public water system reservoirs. *Minor land-disturbing guidance document can be found at the GA EPD website http://epd. georgia.gov/. **Coverage under the NPDES permit is not re­ quired for discharges of storm water associated with infrastructure construction projects that consist solely of routine maintenance for the original purpose of the facility that is performed to maintain the original line and grade and the hydraulic capacity, as applicable. For eligiblty requirements for this exemption please refer to GAR 100002 Part I.C.1.c. considers maintenance to be the work of keeping something in proper condition; or upkeep. Abandoned sites may exist within the jurisdiction of an LIA where land disturbance has previously taken place on permitted construction projects. Due to various reasons, work on the projects may ---PAGE BREAK--- 2016 Edition 1-6 THE MANUAL This Manual has been assembled to provide guidance in the implementation of Act 599. It was written for four specific audiences. 1. The land disturbers: landowners, developers and their consultants, architects, engineers, land surveyors, planners, etc. 2. The enforcers: officials and employees of local units of government charged with responsibil­ ity of administering and enforcing the law on a local level and the Georgia Environmental Protection Division when it is the issuing au­ thority. 3. The plan reviewers: the Georgia Soil and Wa­ ter Conservation Districts and Local Issuing Authorities. 4. The design professionals. have permanently stopped without the site hav­ ing undergone final stabilization. The LIA or the owner of such property should contact GA EPD for the latest regulatory guidance to help ensure the sites are stabilized in compliance with the Act and the NPDES Permits. The LIA or owner of such property should contact for technical guidance on implementing the correct BMPs. Common BMP’s on such sites include, but are not limited to, sediment barriers (perim­ eter control), sediment storage, temporary and permanent vegetation. ---PAGE BREAK--- 2-1 2016 Edition Erosion is the process by which the land surface is worn away by the action of wind, water, ice or gravity. Natural, or geologic, erosion has been occurring at a relatively slow rate since the earth was formed and is a tremendous factor in creating the earth as we know it today. The picturesque mountains of the north, the fertile farmlands of the Piedmont and the productive estuaries of the coastal zone are all products of geologic erosion and sedimentation in Georgia. Excepting some cases of shore and stream channel erosion, natural erosion occurs at a very slow and uniform rate and remains a vital factor in maintaining environmental balance. Human alteration of the earth’s surface can lead to “accelerated erosion.” This is a classic example of environmental abuse and is normally the result of poor planning and unorganized construction. Erosion by water is a process of breaking loose and transporting soil particles. The energy of raindrops falling on denuded or exposed soils is the key element. The annual impact energy of raindrops, for instance, has been estimated to average approximately 30 billion foot-pounds or the equivalent of 10 thousand tons of dynamite per square mile. Water flowing over exposed soil picks up detached soil particles. As the velocity of flowing water increases, additional soil particles are detached and transported. Water flows have a tendency to concentrate. This first creates small channels or rills and eventually gullies of varying widths and depths. As the volume and velocity of runoff increases in unprotected streams and chan­ nels, additional erosion occurs on stream banks and bottoms. Sedimentation is the process where soil particles settle out of suspension as the velocity of water decreases. The heavier particles, gravel and sand, settle out more rapidly than fine silt and clay par­ ticles. The characteristic reddish color of Georgia’s streams in the Piedmont results from suspended microscopic clay particles. Unfortunately, these particles are easily transported and settle out very slowly. It is difficult and perhaps impossible to totally eliminate the transportation of these fine particles, even with the most effective erosion control programs. Figure 2.1 - Energy of falling raindrops has detached and transported soil particles from unprotected areas. FACTORS INFLUENCING EROSION The erosion process is influenced primarily by climate, topography, soils, and vegetative cover. Climate. The frequency, intensity and duration of rainfall and temperature extremes are principle factors influencing the volume of runoff from a given area. As the volume and intensity of rainfall increases, the ability of water to detach and trans­ port soil particles increases. When storms are fre­ quent, intense, and of long duration, the potential for erosion of bare soils is high. Temperature has a major influence on soil erosion. Frozen soils are relatively erosion resistant. However, soils with high moisture content are subject to “spew,” or uplift by freezing action, and are usually very easily eroded upon thawing. Topography. The size, shape and slope charac­ teristics of a watershed influence the amount and duration of runoff. The greater the slope length and gradient, the greater the potential for both runoff and erosion. Velocities of water will increase as the distance from the top of the slope or the grade of the slope increases. CHAPTER 2 SEDIMENT AND EROSION CONTROL PROCESSES, PRINCIPLES AND PRACTICES ---PAGE BREAK--- 2-2 2016 Edition Soils. The soil type will determine its vulnerability to erosion. Properties determining the erodibility of a soil are texture, structure, organic matter content and permeability. Soil containing high percentages of fine sands and silt are normally the most erodible. As the clay and organic matter content of these soils increases, the erodibility decreases. Clays act as a binder to soil particles thus reducing erodibility. But, while clays have a tendency to resist erosion, they are easily transported by water once eroded. Soils high in organic matter resist rain drop impact and the organic matter also increases the binding characteristics of the soil. Clearly, well-graded and well-drained gravels are usually the least erodible soils. The high infiltration rates and permeabilities either prevent or delay runoff. Vegetative Cover. Vegetative cover is an ex­ tremely important factor in reducing erosion from a site. It will: a. Absorb energy of rain drops. b. Bind soil particles. c. Slow velocity of runoff water. d. Increase the ability of a soil to absorb water. e. Remove subsurface water between rainfalls through the process of evapotranspiration. By limiting the amount of vegetation disturbed and the exposure of soils to erosive elements, soil erosion can be greatly reduced. GENERAL DESIGN PRINCIPLES For an erosion and sedimentation control Figure 2.2 60 50 40 30 20 10 2.5 1.5 0.5 JAN. FEB. MAR. APR. MAY JUN. JUL. AUG. SEP. OCT. NOV. DEC. 0 1 2 3 4 5 6 2.0 1.0 0 1940 1945 1950 YEARS * Soil Loss Varies Annually * Soil Loss Varies Seasonally *Information taken from: Barnett, A.P. and B.H. Hendrickson, "Erosion on Piedmont Soils," Soil Conservation Magazine, USDA, Soil Conservation Service, Volume XXVI, No. 2 Sept. 1960 INCHES & TONS / ACRES NUMBER TONS PER ACRE 1955 1959 RAINFALL SOIL LOSS THUNDERSTORMS SOIL LOSS ---PAGE BREAK--- 2-3 2016 Edition program to be effective, it is imperative that pro­ visions for sediment control measures be made in the planning stage. These planned measures, when conscientiously and expeditiously applied during construction, will result in orderly develop­ ment without adverse environmental degrada­ tion. From the previous discussion on erosion and sediment control processes and factors affecting erosion, basic technical principles can be formu­ lated to assist the project planner or designer in providing for effective sediment control. It is felt that these certain key principles must be utilized to the maximum extent possible on all projects. Fit the Activity to the Topography and Soils. Detailed planning should be employed to assure that roadways, buildings and other per­ manent features of the activity conform to the natural characteristics of the site. Large graded areas should be located on the most level por­ tion of the site. Areas subject to flooding should be avoided. Areas of steep slopes, erodible soils with severe limitations for the intended uses should not be utilized without overcoming the limitations through sound engineering practices. Erosion control, development and maintenance costs can be minimized if a site is selected for a specific activity rather than attempting to modify the site to conform to the proposed activity. The Disturbed Area and the Duration of Exposure to Erosion Elements Should be Minimized. Clearing of natural vegetation should be limited to only those areas of the site to be developed at a given time. Natural vegeta­ Figure 2.3 - Permanent facilities for this development were planned to fit the topography and soil type. Figure 2.4 - Unstable soil conditions, as on this roadbank, should be avoided. Figure 2.6 - Vegetation on this road bank will reduce erosion to a minimum. Figure 2.5 N EL=845.92 PARKING PARKING GYM ELEV. 847.00 SCHOOL FIN. FLOOR ELEV. 847.00 840 850 860 EL=864.41 860 FOOTBALL FIELD ELEV. 858.00 EL=855.33 850 840 830 820 810 915.01' S80º33'00" 200.00 S9º'27'00"E 810 PLAYGROUND AREA ELEV. 812.00 800 790 S 7º53'10"E 407.22' 406.52 S 80º33'00"W 206.10' N 41 16'00"E 1088.09' 830 820 820 820 R=1361.31" 787.31' 810 800 790 810 S 50º04'56"E 50.01' 810 Co St Ds3 Cd Di Cd Cd Cd Di Di Di Ds2 Ds3 Mb Di Dn2 St Cr Sd2 Ds2 Ds3 Sd1 SEDIMENT FENCE Lv Di Di Ds2 Ds3 Sd1 BRUSH BARRIER Tp Lv Mb Wt St Sd3 Tp Sd3 S41 16 00"W 300.26' EL=808.91 800 294.40 N7º23'00"W 100 100 200 50 SCALE, IN FEET VEGETATIVE PLAN LOCATION Football Field & Playground Hulled Common Bermudagrass Hulled Common Bermudagrass & Virgata Lespedeza Sod Common Bermudagrass Ryegrass Roadside April '92 April '91 April '91 Oct. '91 Waterway School SPECIES DATE 0 TOTAL AREA = 21.34 ACRES ACTIVITY SCHEDULE Activity Month 1 Month 2 Month 3 Month 4 Initial Perimeter and Sediment Storage BMPs Clearing & Grubbing Erosion Control Devices Grading Temporary Vegetation Infrastructure Construction (Incl. Utilities) Base Paving Fine Grading ---PAGE BREAK--- 2-4 2016 Edition tion should be retained, protected and supple­ mented with construction scheduling employed to limit the duration of soil exposure. Major land clearing and grading operations should be scheduled during seasons of low potential runoff. Stabilize Disturbed Areas Immediately. Permanent structures, temporary or permanent vegetation, and mulch, or a combination of these measures, should be employed as quickly as possible after the land is disturbed. Temporary vegetation and mulches can be most effective on areas where it is not practical to establish Figure 2.7 - Hydroseeding equipment can efficiently and quickly establish disturbed areas. Figure 2.8 - Matting can assist in rapid establishment of vegetation. permanent vegetation. These temporary mea­ sures should be employed immediately after rough grading is completed, if a delay is antici­ pated in obtaining finished grade. The finished slope of a cut or fill should be stable and ease of maintenance considered in the design. Stabilize all roadways, parking areas, and paved areas with a gravel subbase, temporary vegetation or mulch. Retain or Accommodate Runoff. Runoff from the development should be safely conveyed to a stable outlet using storm drains, diversions, stable waterways or similar measures. Consideration should also be given to the installation of storm water detention structures to prevent flooding and damage to facilities resulting from increased runoff from the site. The LIA should be consulted for their requirements. Temporary or permanent facilities for conveyance of storm water Figure 2.10 - Storm water detention structures will reduce storm water runoff from developed areas. Figure 2.9- This vegetated waterway will safely convey storm water away. Figure 2.11 - This temporary sediment basin effectively trapped sediment from upstream erosion. ---PAGE BREAK--- 2016 Edition 2-5 Figure 2-12. - A temporary sediment basin converted to a permanent pond enhances landscape. Figure 2.14 - Temporary bridges or culverts should be employed when construction equipment is required to cross natural or constructed channels Figure 2.13 - Offsite impact from a neighboring construction site. should be designed to withstand the velocities of projected peak discharges. These facilities should be operational as soon as possible after the start of construction. Retain Sediment. Sediment basins, sediment barriers and related structures should be installed to filter or trap sediment on the site to be disturbed. The most effective method of controlling sedi­ ment, however is to control erosion at its source. Sediment retention structures should be planned to retain sediment when erosion control methods are not practical, are insufficient, in the process of being installed, or have failed due to some unfore­ seen factor. Do Not Encroach Upon Watercourses. Perma­ nent buildings should not be subjected to flooding, sediment damages or erosion hazards. Earth fills should not be constructed in flood-prone areas so as to adversely obstruct water flows or increase velocity of water flows. When neces­ sary to span a flood-prone area or watercourse, bridge and culvert openings should be sized to permit passage of peak discharges without causing undue restrictions in water flows or without creating excessive velocities. Uses of flood- prone areas should be limited to activities which would not suffer excessive damages from flooding, scour and sediment. Temporary bridges or culverts should be employed when construction equipment is required to cross natural or constructed channels. EROSION AND SEDIMENTATION CONTROL PRACTICES Severe erosion on lands undergoing land-dis­ turbing activities can be reduced if proper control measures are implemented. The timely applica­ tion of Best Management Practices (BMPs) will minimize the time that the soils are exposed, control runoff, shield the soil from erosive forces, and bind the soils. A most effective tool in controlling erosion is good site planning which includes planning and installa­ tion of BMPs. In Chapter 6, of this Manual are stan­ dards and specifications for such practices which can be utilized on areas undergoing land-disturbing activities. These standards were developed to es­ tablish statewide uniformity in selection, design, review, approval, installation and maintenance of conservation practices. They establish minimum requirements for planning, designing and installing the practices on disturbed areas. For effective erosion control, a combination of BMPs must be employed. Alternative BMPs may be approved for individual erosion and sediment control plans. An Alternative BMP Guidance Docu­ ---PAGE BREAK--- 2-6 2016 Edition ment can be found on the website. In general, they fall into the rather broad categories of structural practices and vegetative measures. VEGETATIVE CONSERVATION MEASURES Vegetative practices may be applied singu­ larly or in combination with other conservation measures. They may be either short lived or of a permanent nature. Sub-soils, mixtures of soils and soils with varying organic matter content, will be encountered when soil surfaces are disturbed. Unfavorable growth conditions such as acidity, low fertility, compaction and adverse moisture contents are often prevalent. These conditions are difficult to overcome but must be eliminated if adequate plant growth is to be obtained. A soil test will be essential to determining soil char­ acteristics detrimental to plant growth. Steep gradients and long slopes are often present on areas to be vegetated. These areas are subject to erosive forces from rainfall impact and flowing water, and will require special techniques and grasses which will resist erosion. Establishing vegetation is possible with techniques and plants developed over the years. Temporary Vegetation. In many instances, grading of areas is completed at a time when it is not practical to try to establish permanent vegeta­ tion. These areas can be stabilized by planting instead a variety of temporary annual grasses such as rye grass, rye, small grains and similar species. These temporary grasses will provide a rapid cover that can later be worked into the soil to provide organic matter when permanent vegeta­ tion is established. Every effort should be made to select temporary plants that will be compatible with the final permanent vegetation. Permanent Vegetation. A wide selection of various grasses, legumes, ground cover, trees and shrubs can be used for permanent vegetation. If a high level of management is possible, an even wider range of plants can be used. It is imperative that the final selection of plants be based on the adaptability of those plants to the topography and climate. Ease of establishment, life expectancy, maintenance requirements, aes­ thetics and any other special qualities should be considered. It is desirable to select plants requiring little maintenance. Many plants can be used to im­ prove the aesthetics of a site and still be effective soil stabilizers. Special attention should be given to steep cut and fill slopes where plants requiring little maintenance must be utilized. Mulching. Due to time constraints, it may be impractical to stabilize an area with vegetation. Excellent temporary soil stabilization can be other­ wise achieved using straw, hay, mulch with tackifier, rolled erosion control blankets (RECPs), hydrau­ lically-applied erosion control products (HECPs) and fibers. Areas where final grade has been reached can be stabilized with mulch and over seeded at the proper time for permanent grasses. Mulches allow for greater infiltration of water into soil; reduce the amount of runoff; retain seeds, fer­ tilizer and soil amendments in place; and improve soil moisture and temperature conditions. Mulch is essential in establishing good stands of grasses and legumes on disturbed areas. In order to prevent movement by wind or water, it is important that it be anchored to the soil. Following are examples of vegetative practices suitable for utilization on disturbed land. A map code has been assigned to each practice and ap­ pears at the beginning of the title of each practice. Bf - BUFFER ZONE A strip of undisturbed original vegetation, enhanced or restored existing vegetation, or the re-establishment of vegetation surrounding an area of disturbance or bordering streams, ponds, wetlands, lakes, and coastal waters. Cs - COASTAL DUNE STABILIZATION (WITH VEGETATION) Planting vegetation on dunes that are denud­ ed, artificially constructed, or re-nourished. Ds1 - DISTURBED AREA STABILIZATION (WITH MULCHING ONLY) Using plant residues or other suitable ma­ terials on the soil surface to reduce runoff and erosion, conserve moisture, prevent soil compac­ tion and crusting, control undesirable vegetation, modify soil temperature and to increase biologi­ cal activity in the soil. This practice is applicable where stabilizing disturbed or denuded areas is not practical utilizing seeding or planting. ---PAGE BREAK--- 2-7 2016 Edition EFFECTIVENESS OF GROUND COVER ON EROSION AND SEDIMENT CONTROL ON CONSTRUCTION SITES % Soil Loss Ground Cover Type Compared to Bare Soil Permanent grasses 99 Ryegrass (perennials) 95 Ryegrass (annuals) 90 Small grain 95 Millet or sudangrass 95 Grass sod 99 Hay (2 tons/acre) 98 Small grain straw 98 (2 tons/acre) Corn stalks (4 tons/acre) 98 Woodchips (6 tons/acre)2 94 Wood cellulose fiber 90 (1 3/4 tons/acre)2 Other kinds of mulches that may be used are gravel, stones, temporary erosion control blanket, fibermatting, and excelsior. Reference: USDA, Agricultural Research Service. Ds2 - DISTURBED AREA STABILIZATION (WITH TEMPORARY SEEDING) A temporary vegetative cover with fast grow­ ing seedings for disturbed or denuded areas. This practice is applicable for up to six months or until permanent vegetative cover can be in­ stalled. It should be coordinated with permanent measures to assure economical and effective stabilization. Techniques for establishing tempo­ rary cover utilizing both conventional and hydrau­ lic seeding equipment are included. Ds3 - DISTURBED AREA STABILIZATION (WITH PERMANENT VEGETATION) A permanent vegetative cover such as trees, shrubs, vines, grasses and legumes on disturbed or denuded areas. It will apply on cut and fill slopes, earth spillways, borrow areas, spoil areas and severely eroded or gullied lands. Techniques utilizing both conventional and hydraulic seeding equipment are discussed. Ds4 - DISTURBED AREA STABILIZATION (WITH SODDING) A permanent vegetative cover using sods on highly erodible or critically eroded lands. Sods provide immediate ground cover and help filter sediments and nutrients. Du - DUST CONTROL ON DISTURBED AREAS Controlling the surface and air movements of dust on construction sites, roadways and similar sites. Methods and materials which can be used include mulches, vegetative cover, spray-on adhesives, mechanical manipulation of existing soil surfaces, irrigation, barriers, chemicals, and stone surface covers. Fl-Co - FLOCCULANTS/COAGULANTS Flocculants and Coagulants are formulated to assist in the solids/liquid separation of sus­ pended particles in solution. Such particles are characteristically very small and the suspended stability of such particles (colloidal complex) is due to both their small size and to the electrical charge between particles. Conditioning a solution to promote the removal of suspended particles requires chemical coagulation and/or floccula­ tion. Sb - STREAMBANK STABILIZATION (USING PERMANENT VEGETATION) The use of readily available native plant mate­ rials to maintain and enhance streambanks, or to prevent, or restore and repair small streambank erosion problems. Ss - Slope Stabilization A protective covering used to prevent erosion and establish temporary or permanent vegetation on steep slopes, shore lines, or channels. Tac -TACKIFIERS Substances used to anchor straw or hay mulch by causing the organic material to bind together. Hay or straw will drift downslope unless anchored in place with tackifiers and binders. Tackifiers and binders reduce runoff and erosion as well as conserve moisture and prevent sur­ face compaction. ---PAGE BREAK--- 2-8 2016 Edition STRUCTURAL CONSERVATION PRACTICES In some instances, vegetative cover and mulches alone will not provide sufficient protec­ tion from the erosive forces of water. In such cases, alternate structural practices can be used to curb erosion and sedimentation during land- disturbing activities. These practices should be planned and employed in a practicable combina­ tion with vegetative and mulching measures. Structural practices must be adequately de­ signed and properly installed to accomplish the desired objective. Design should be based on the appropriate storm discharge and velocities. Consideration should be given to the damage po­ tential, safety hazards, planned life and required maintenance of each individual structural practice. Following is an overview of standards and specifications for structural practices contained in Chapter 6 of this Manual. Cd - CHECKDAM A dam constructed across a swale or drain­ age ditch. This is applicable for use in small channels which drain five acres or less (not to be used in a live stream) in order to reduce erosion by slowing the velocity of concentrated storm water flows. Ch - CHANNEL STABILIZATION Improving, constructing or stabilizing a natural or artificial channel for conveying water flows. In certain instances on selected development, it will be found that existing channels will not be adequate to convey desired discharges. New channels may be required to eliminate flooding. In many cases, existing channels cannot be con­ sidered stable. Therefore, this practice may be employed to assist in stabilizing these channels Co - CONSTRUCTION EXIT A stone-stabilized pad located at any point where vehicular traffic will be leaving a site onto a public right-of-way, street, roadway, or park­ ing area. Its purpose is to reduce or eliminate transportation of soil (by motor vehicles) from the construction area onto public rights-of-way. Cr - CONSTRUCTION ROAD STABILIZATION Roads, parking areas, and other transporta­ tion routes that are stabilized with coarse ag­ gregate between the time of initial grading and final stabilization. This travelway provides a fixed route for travel for construction traffic, reduces erosion, and subsequent regrading of permanent roadbeds, and provides a stable base for paving. Dc - STREAM DIVERSION CHANNEL A temporary channel that diverts a stream around a construction site to protect the stream­ bed from erosion and allow work “in the dry”. This diversion is used when in-stream work is unavoidable, as with linear projects such as utilities or roads that frequently cross and impact live streams and create a potential for excessive sediment loss by both the disturbance of the ap­ proach areas and by the work within the stream­ bed and banks. Di - DIVERSION An earth channel with a compacted support­ ing ridge on the lower side, constructed above, across, or below a slope. The purpose of this practice is to reduce slope break-up concentrations of runoff, and move water to stable outlets at non-erosive velocities. Diver­ sions should be designed to discharge water into established disposal areas. Dn1 - TEMPORARY DOWNDRAIN STRUCTURE A flexible conduit of heavy-duty plastic or other material used as a temporary structure to convey concentrations of stormwater down the face of a cut or fill slope. Flexible downdrains are used on slopes where concentrations of storm­ water would cause substantial erosion. They are removed once the permanent water disposal system is installed. Dn2 - PERMANENT DOWNDRAIN STRUCTURE A paved chute, pipe or a sectional conduit of prefabricated material designed to safely con­ duct surface runoff from the top to the bottom of a slope. Downdrain structures are to be used where concentrated water will cause excessive erosion of cut and fill slopes. Fr - FILTER RING A temporary stone barrier used in conjunction with other sediment control measures and con­ structed to reduce flow velocities and filter sedi­ ---PAGE BREAK--- 2-9 2016 Edition ment. A filter ring can be installed at or around devices such as inlet sediment traps, temporary downdrain inlets, and detention pond retrofits to provide additional sediment filtering capacity. Ga - GABION Large, rock-filled baskets wired together to form flexible monolithic building blocks. They are used in channels, retaining walls, abutments, check dams, etc., to prevent erosion and sedi­ ment damage to a specific structure. Gr - GRADE STABILIZATION STRUCTURE Structures of concrete, rock masonry, steel, aluminum, treated wood, etc. They are installed to stabilize the grade in natural or artificial chan­ nels and to prevent the formation or advance of gullies and to reduce erosion and sediment pollution. Lv - LEVEL SPREADER A storm flow outlet device constructed at zero grade across the slope whereby concentrated runoff may be discharged at a non-erosive veloc­ ity onto undisturbed areas stabilized by existing vegetation. Concentrated flow of stormwater is converted to sheet flow at the level spreader. Rd - ROCK FILTER DAM A temporary stone filter dam installed across drainageways or in conjunction with a temporary sediment trap. This structure is installed to serve as a sediment-filtering device and to reduce storm water flow velocities. This practice may require a US Army Corps of Engineers permit. Re - RETAINING WALL A constructed wall of concrete, masonry, reinforced concrete, cribbing, treated timbers, gabions, stone dry wall, riprap or other durable material. They are installed to stabilize cut or fill slopes where maximum permissible slopes of earth are not obtainable. Each situation will require a specific design by a design engineer. Rt - RETROFITTING The physical modification of a storm water management outlet structure, using a half round corrugated metal pipe or similar device, to trap sediment contained in runoff water. Sd1 - SEDIMENT BARRIER A temporary structure constructed of silt fence, brush piles, mulch berms, compost filter socks or other filtering material. They are in­ stalled to minimize and prevent sediment from leaving the site and entering natural drainage ways or storm drainage systems. They are not to be used on high-risk areas or where there will be a possibility of failure. Silt fence shall not be installed across streams, waterways, or other concentrated flow areas. Formal design is nor­ mally not required for sediment barriers. Sd2 - INLET SEDIMENT TRAP A temporary protective device formed at or around an inlet to a storm drain to trap sediment. They are employed to trap sediment in runoff water from small, disturbed areas. Clean out of these facilities is normally required after each heavy rainfall. Sd3 - TEMPORARY SEDIMENT BASIN A basin created by an embankment or dam containing a principal spillway pipe and an emergency spillway. These structures are nor­ mally situated within natural drainageways and at the lowest point on a construction site and are used to trap sediment contained in runoff water. Excavated basins may be employed where sites for embankment do not exist. Sediment basins serve only during the construction phase and are removed from the site when the disturbed area has been permanently stabilized. Structure size will vary depending on the size of the drainage area, volume of sediments to be trapped, rainfall, structure location, etc. These structures can be regarded as being hazardous if constructed in areas of dense population. In these cases, it is advisable to protect them from trespassing. Permanent sediment basins are designed to fit into the overall plan of the completed development. They may be converted to storm water retention facilities to reduce storm water discharges. This specification does not apply to the design of permanent sediment basins. Sd4 - TEMPORARY SEDIMENT TRAP A small temporary pond that drains a dis­ turbed area so that sediment can settle out. The ---PAGE BREAK--- 2-10 2016 Edition principle feature distinguishing a temporary sedi­ ment trap from a temporary sediment basin is the lack of a pipe or riser. Sk - FLOATING SURFACE SKIMMER A floating surface skimmer is a buoyant de­ vice that releases/drains water from the surface of sediment ponds, traps or basins at a con­ trolled rate of flow. It “skims”, or dewaters, from the water surface where sediment concentrations are at a minimum in the water column instead of draining from the bottom where sediment con­ centrations are their highest. SpB - SEEP BERM A seep berm is a linear control device con­ structed as a diversion perpendicular to the direction of the runoff to enhance dissipation and infiltration of runoff, while creating multiple sedimentation chambers with the employment of intermediate dikes. Sr - TEMPORARY STREAM CROSSING A temporary structure installed across a flow­ ing stream or watercourse for use by construc­ tion equipment. The structure may consist of a pipe, bridge, or other suitable device permitting vehicular traffic without damaging stream banks and beds. St - STORM DRAIN OUTLET PROTECTION A paved or short section of riprap channel placed at the outlet of a storm drain system. The purpose is to reduce the velocity of water flows below storm drain outlets, and to prevent erosion from concentrated flow. Su - SURFACE ROUGHENING Providing a rough soil surface with horizontal depressions created by operating a tillage or other suitable implement on the contour, or by leaving slopes in a roughened condition by not fine grading them. This aids in the establishment of vegetation, reduction of runoff, and reduction of sediment. Tc -TURBIDITY CURTAIN A floating or staked barrier installed within the water. (It may also be referred to as a floating boom, silt barrier or silt curtain). Tp - TOPSOILING Topsoiling areas to be vegetated by utilizing a suitable quality soil. The purpose is to provide a suitable soil medium for vegetative growth on areas where desired stands of vegetation are dif­ ficult to establish and maintain. Tr - TREE PROTECTION To protect desirable trees from injury during construction activity. Wt - VEGETATED WATERWAY OR STORMWATER CONVEYANCE CHANNEL Outlets for diversions, terraces, berms, or other structures. They may be natural or con­ structed, shaped to required dimensions, and paved or vegetated for disposal of storm water runoff. They may be of three general cross sec­ tions: parabolic, triangular, or trapezoidal. Para­ bolic waterways are the most commonly used. For waterways to be successful, it is essential that a protective cover of vegetation or other ero­ sion protective measures be implemented. Flow velocities must be selected that will produce non- erosive flows within the waterway during peak discharges. CONSTRUCTION TECHNIQUES Other construction techniques may be em­ ployed by field personnel to assist in implement­ ing an effective erosion control program. A few of these are discussed below. a. Leave Exposed Soil Surfaces Rough. Smooth soil surfaces will erode more readily than rough ones. Therefore, cut or fill slopes should not be “dressed” or smoothed until time to establish vegetation. Cut or fill slopes may be scarified or serrated using conven­ tional earth moving equipment to provide this roughening effect. The cleated tracks of bulldozers are effective in compacting as well as roughening cut or fill slopes. b. Selective Fill Placement. Fills over culverts and conduits can be left in a condition to drain rain water to the upstream side of the culvert. This operation can be performed at the end of each construction day and will assist in retaining sediment on the site. c. Selective Clearing. Clearing operations should be confined to the removal of timber and heavy brush only. Ground covers consist­ ing of small plants, weeds and organic matter should be retained until the start of the grading ---PAGE BREAK--- 2-11 2016 Edition operation. d. Retain Natural Sediment Traps. Small de­ pressions in the land surface, natural creek berms and other natural sediment traps may be preserved in a natural state until such time as building sequences will require their altera­ tion. e. Retention of Natural Vegetation. Natural Vegetation on disturbed area perimeters and adjacent to stream channels should be retained. UNIFORM CODING SYSTEM The following coding system chart has been developed to provide statewide uniformity for erosion and sediment control plans. A code has been assigned to each practice. This code should appear at the desired location on the plan. In some instances, more than one code will appear. For example, an area planted in tem­ porary vegetation will eventually be established to permanent seeding. Therefore, both codes should appear on the plans at the appropriate lo­ cation. A symbol also has been assigned to most practices. For certain practices it will be neces­ sary to place both the symbol and code letter on the plans. To assist the user, a small detail drawing and a brief description of the major characteristics of the practice have been included on the coding system chart. To increase the efficiency for all the agencies in erosion and sediment control and for the develop­ ment community, this Manual includes a process for Alternative BMPs that are repeatedly used and approved under Guidance to be placed on an Equivalent BMP List. This List is similar to the 5th Edition of the Manual’s recognition of materials approved by the Georgia Department of Transpor­ tation (GDOT) that appear on GDOT’s Qualified Products List (QPL). Refer to Appendix A-2 for information about joining the Equivalent BMP List. ---PAGE BREAK--- 2-12 2016 Edition FOR SOIL EROSION AND SEDIMENTATION CONTROL PRACTICES Cd A storm flow outlet device constructed at zero grade across the slope whereby concentrated runoff may be discharged at a non-erosive veloci­ty onto undisturbed areas stabilized by existing vegetation. A temporary stone filter dam installed across drainageways or in conjunction with a temporary sediment trap. A temporary protective device formed at or around an inlet to a storm drain to trap sediment. A barrier to prevent sediment from leaving the construction site. It may be sandbags, bales of straw or hay, brush, logs and poles, or a silt fence SpB ---PAGE BREAK--- 2016 Edition 3-1 SECTION I - PLANNING Planning is the critical process by which land- disturbing activities are formulated. The planning process for activities governed by Act 599 can be broken down into the following four progressive stages: 1. preliminary site investigations 2. preliminary design 3. subsurface investigation 4. final design For many small land-disturbing activities, steps one and two are sometimes combined but planning for major developments normally follows these four steps. To be successful, a plan must include mea­ sures for efficient scheduling and coordination of construction activities and provisions for the maintenance of conservation practices. Stormwater management facilities should be included to reduce the impact of stormwater runoff to on-site facilities both during and after construction is completed. It is desirable to include stormwater retention struc­ tures. Land-disturbing activities normally will result in an increase in runoff from the site. Stormwater management structures will reduce the impact of damages on facilities resulting from an increase in runoff. Many of the Local Issuing Authorities in the State have a Stormwater Ordinance. The design profes­ sional should consult with the LIA before designing the construction plans. The Georgia Stormwater Management Manual is available for download at www.georgiastormwater.com. PLANNING STAGES Preliminary Site Investigation Stage. The first consideration in the preliminary site inves­ tigation stage should be the assimilation of all available resource information. This information will assist the planners in identifying critical phys­ ical features of the site which would have sig­ nificant impact on erosion and sediment control. Delineation of flood-prone areas and areas which would have a high aesthetic value if protected CHAPTER 3 PLANNING AND PLANS can be identified. Sources of resource informa­ tion are included in Chapter 5 of this Manual. A conservation planning base map should be prepared utilizing all information available. The final step would be a detailed on-site inspection. At this time, base maps should be thoroughly checked for accuracy. O.C.G.A. § 12-7-9, requires certification stat­ ing that the plan preparer or the designee thereof visited the site prior to creation of the plan or that such a visit was not required in accordance with rules and regulations established by the board. GA EPD Rule 391-3-7-.10 Site Visit Required. All applications shall contain certification stating that the plan preparer or his or her designee has visited the site prior to creation of the plan. plans submitted shall contain the following certification: “I certify under penalty of law that this Plan was prepared after a site visit to the location described herein by myself or my authorized agent, under my direct supervision.” Preliminary Design Stage. In the preliminary design stage, a thorough analysis of the information assembled during the preliminary site investigation stage should be accomplished. The objective of the analysis is to determine how the proposed site can be best utilized as intended without causing undue harm to the environment. Areas particularly vulnerable to erosion and sedimentation because of existing topography, soils, vegetation or drainage should be identified. The planner is encouraged to use available soils information in his site analysis. A discussion of the use of soils information in site planning follows in this chapter. Subsurface Investigation Stage. A subsurface investigation should be accomplished to determine the geological features and the nature and prop­ erties of the soils present on the site. A detailed on-site soils investigation will be necessary for the design of complex buildings, roadways, and other engineering structures. Facilities that will be serviced by septic tanks will require on-site testing. The stability of slopes should be determined based on soils analysis. Groundwater problems should ---PAGE BREAK--- 3-2 2016 Edition Soil maps and supporting data provide informa­ tion about important soil properties, including the following: Flood Hazards - Soil surveys show areas that are subject to flooding. Although this information is not a substitute for hydrologic surveys, which determine the limits of flooding on the basis of the severest flood expected once in 10, 25, 50 or 100 years, it does provide a good first approximation of the flood-prone areas. Wetness - Soil surveys show if the soil is well drained, poorly drained, or seasonally waterlogged, and if the water table is seasonally high. The rating of the permeability of soils is also included. Bearing Capacity - Soil surveys provide test data and estimates of the physical properties of soils that enable engineers to make sound judg­ ments about bearing capacities for shallow founda­ tions. Major soil layers to a depth of about 5 feet are classified in both the United and the AASHTO systems. Data is also given on grain-size distribu­ tion and expansiveness for each soil layer. Depth to Rock - Soil surveys show locations where bedrock is at depths of less than 5 or 6 feet and describe the geologic material that underlies the soil. Shrink-swell and Slippage - Soil properties that result in high swelling pressures, mainly the kind and amount of clay, are given in soil surveys. Soil surveys also indicate soil properties that make soils unstable and susceptible to slippage. THE REVISED UNIVERSAL SOIL LOSS EQUATION RUSLE1 was first released for widespread use in late 1992 as version 1.02. Improved versions of RUSLE were periodically released to cover errors and to give RUSLE increased capability. Previous versions of RUSLE were available for a fee from the Soil and Water Con­ servation Society (SWCS) through a Cooperative Research and Development Agreement with the Agricultural Research Service (ARS) of the United States Department of Agriculture (USDA) that gave the SWCS a copyright on RUSLE1. That agreement expired in 1996. The last ver­ sion of RUSLE1 covered by that agreement was RUSLE1.05. Version 1.06c is not covered by be identified at this time. Soils subject to water flows should be analyzed for permissible veloci­ ties. Soils to be established in vegetation should be examined for pH, nutrient levels and ease of establishing vegetation. Methods of overcoming soils limitations should be explored. Final Design Stage. Final designs should be based on detailed engineering surveys, subsurface investigations and sound conservation and engi­ neering principles. Permanent buildings, roadways and engineering structures should be fitted to the topography and soil types. Efficient, durable and easily maintained erosion control measures should be employed. Sediment basins, barriers and traps should be designed to trap sediment which would be transported from the site. All stormwater facilities should be of adequate capacity and have the ability to withstand peak velocities. Filling or development within flood-prone areas should be avoided except those activities necessary to promote public health and welfare. If, for example, roadway crossings are made, openings must be sized to eliminate undue restriction in water flows and excessive down­ stream velocities. Natural vegetation and open space should be provided. Finally, rigid construction scheduling should be employed. SOILS INFORMATION AND SITE PLANNING An invaluable tool in planning for land dis­ turbing activities is soils information available through USDA Natural Resources Conservation Service (NRCS). Soil scientists study, evaluate, classify and map soils in counties throughout Georgia and publish soil surveys with maps and descriptions. Published soil surveys have been digitized and can be accessed through the Web Soil Survey. The Web Soil Survey is an interactive, internet based application that contains soil maps and associated attribute data from soil surveys produced by the Na­ tional Cooperative Soil Survey. Spatial and attribute data are available on the Web Soil Survey for all Georgia counties that have a completed, correlated soil survey, which currently includes most, but not all Georgia counties. Further information about how to use the Web Soil Survey and the information it contains is in Appendix B-1 of the Manual. A status map of Georgia counties with spatial data available can be found on the Soil Data Mart, http://soildat­ amart.nrcs.usda.gov/Statusmap.aspx. ---PAGE BREAK--- 2016 Edition 3-3 the copyright and can be freely downloaded by anyone who wishes to use it. NRCS is now implementing RUSLE2 in its field offices as a replacement for RUSLE1. RUSLE2 uses physically meaningful input values that are widely available in existing databases or can be easily obtained. It is believed to be the best avail­ able practical erosion prediction technology that can be easily applied at the local office level. RUSLE2 computes net detachment each day using a variation of the familiar RUSLE factors: a = r k l S c p Where: a = net detachment (mass/unit area) r = erosivity factor k = oil erodibility factor l = slope length factor S = slope steepness factor c = cover-management factor p = supporting practices factor The lower case symbols represent daily val­ ues. Upper case symbols used in the USLE and RUSLE1 represent annual values. Each factor, except the slope steepness factor S, in the above equation change daily and as cover-management conditions change with specific events, like soil- disturbing operations. Although the values used for each factor are daily values, they represent long-term average conditions for that day. The key element in this equation is the product of rk, which produces a daily sediment production estimate for unit-plot conditions. The variables r and k have units so that the product rk has absolute units of mass/area. The other variables in this equation adjust the unit-plot sediment production value to reflect differences between unit-plot condi­ tions and site-specific field conditions. The factors l,S, c, and p are ratios of sediment production from the given field condition to unit-plot conditions and do not have units. RUSLE1.06c and RUSLE2 can both be freely accessed at: http://www.ars.usda.gov/Research/ docs.htm?docid=5971. Design professionals of land disturbing activi­ ties should specify that the estimated erodibility of subsurface soil be obtained during site borings, because of the natural range and variability of soil properties. Additional information about soils and their properties, use, and interpretation can be found in the Web Soil Survey, as described in Appendix B-1. SECTION II - PLANS Sample erosion control plans are avail­ able for review on the website at It should be emphasized that the methodology utilized in this example is only one of many avail­ able to the designer or planner. Many other practi­ cal combinations of erosion control measures could have been employed to effectively reduce erosion on this site. LAND DISTURBING ACTIVITY PLAN Any land disturbing activity which disturbs one acre or greater, is not a part of a larger common plan of development, and is not exempt from the Act as listed on page 1-3 in Chapter 1 of this Manual, must have an Erosion and Sedi­ ment Control (E&SC) Plan. Any land disturbing activity which disturbs less than one acre, and is within 200’ of a perennial stream must also have an E&SC Plan. The State of Georgia also requires most land disturbing activities disturbing one acre or greater to obtain coverage under the National Pollutant Discharge Elimination System (NPDES) Permits. There are currently three NPDES Permits for con­ struction projects in Georgia: 1. GAR100001 For Stand Alone Projects 2. GAR100002 For Infrastructure Projects 3. GAR100003 For Common Developments The NPDES Permits require the permittee to have an Erosion, Sedimentation and Pollution Con­ trol (ES&PC) Plan. The and the GA EPD have compiled a plan review checklist for each of the three permits that list all the requirements for all plans to be in compliance with the Act and the NPDES Permits. Projects that disturb less than one acre and are within 200’ of a perennial stream are not exempt from the Act, but are exempt from NPDES. Items ---PAGE BREAK--- 3-4 2016 Edition on the Stand Alone and Infrastructure checklists that do not apply when NPDES is not applicable are indicated on the checklists. All ES&PC Plans must be prepared by a design professional licensed by the State of Georgia in the field of engineering, architecture, landscape architecture, forestry, geology, or land survey­ ing; or a person that is a Certified Professional in Erosion and Sediment Control (CPESC) with a cur­ rent certification by Certified Professional in Erosion and Sediment Control Inc*. All design professionals and plan reviewers of an ES&PC Plan must have a current Level II certification issued by the NPDES Permits and Fee Schedule, Notice of Intent (NOI) for all permittees, and Notice of Termi­ nation (NOT) for all permittees can be downloaded from the EPD or the website. Certification criteria and classes can be found on the website. *A CPESC certification is offered by EnviroCert International, for additional information please visit www.cpesc.org. ---PAGE BREAK--- ---PAGE BREAK--- 0 60 120 GRAPHIC SCALE SCALE: 60' A. DUNLOP OWNER HARRY HIGHBALL CONSULTING ENGINEERS COUNTY, STATE 336 LAND LOT 6th LAND DISTRICT MARCH 4, 2013 DATE JAN JACOBY DRAWN BY BARGAIN BUYS STORES DEVELOPMENT TIFT, GEORGIA REVISION NUMBER REQUESTED BY DATE SOIL INFORMATION OnA An SOIL SYMBOL SOIL TYPE SLOPE % ALAPAHA URBAN LAND COMPLEX OCILLA-URBAN LAND COMPLEX K LIMITATION SYMBOL REASONS FOR LIMITATION 0 - 2 0 - 2 0.10 0.10 VERY LIMITED SOMEWHAT LIMITED FLOODING, DEPTH TO SATURATED ZONE DEPTH TO SATURATED ZONE DRAWING 1 SOILS, VEGETATION AND DRAINAGE SEAL - VEGETATION - SOIL SYMBOL - PROPERTY LINE - SOIL BOUNDARY - IMPAIRED CREEK OnA TYPE LEGEND EROSION CONTROL CERTIFICATION I CERTIFY UNDER PENALTY OF LAW THAT THIS PLAN WAS PREPARED AFTER A SITE VISIT TO THE LOCATIONS DESCRIBED HEREIN BY MYSELF OR MY AUTHORIZED AGENT, UNDER MY SUPERVISION. BY HARRY HIGHBALL REGISTERED GEORGIA ENGINEER No. PE123456 LEVEL II CERTIFIED DESIGN PROFESSIONAL - CERTIFICATION NUMBER [PHONE REDACTED] 3-6 2016 Edition ---PAGE BREAK--- 0 60 120 GRAPHIC SCALE SCALE: 60' A. DUNLOP OWNER HARRY HIGHBALL CONSULTING ENGINEERS COUNTY, STATE 336 LAND LOT 6th LAND DISTRICT MARCH 4, 2013 DATE JAN JACOBY DRAWN BY BARGAIN BUYS STORES DEVELOPMENT TIFT, GEORGIA REVISION NUMBER REQUESTED BY DATE DRAWING 2 DETAILED BOUNDARY LINE AND TOPOGRAPHIC SURVEY WITH FIXED IMPROVEMENTS - SANITARY SEWER LINE - PROPERTY LINE - POWER LINE - WATER LINE LEGEND - IRON PIN SET - IRON PIN FOUND OH SS - CONTOUR LINE, EXISTING - CONTOUR LINE, FINISH W SEAL EROSION CONTROL CERTIFICATION I CERTIFY UNDER PENALTY OF LAW THAT THIS PLAN WAS PREPARED AFTER A SITE VISIT TO THE LOCATIONS DESCRIBED HEREIN BY MYSELF OR MY AUTHORIZED AGENT, UNDER MY SUPERVISION. BY HARRY HIGHBALL REGISTERED GEORGIA ENGINEER No. PE123456 LEVEL II CERTIFIED DESIGN PROFESSIONAL - CERTIFICATION NUMBER [PHONE REDACTED] 3-7 2016 Edition ---PAGE BREAK--- 3-8 2016 Edition ---PAGE BREAK--- 3-9 2016 Edition ---PAGE BREAK--- A. DUNLOP OWNER HARRY HIGHBALL CONSULTING ENGINEERS COUNTY, STATE 336 LAND LOT 6th LAND DISTRICT MARCH 4, 2013 DATE JAN JACOBY DRAWN BY BARGAIN BUYS STORES DEVELOPMENT TIFT, GEORGIA REVISION NUMBER REQUESTED BY DATE DRAWING 5 EROSION AND SEDIMENT CONTROL PLAN FINAL PHASE MAY 2013 APR 2013 CLEARING & GRUBBING GRADING BASE PAVING EROSION CONTROL DEVICES FINE GRADING & LANDSCAPING REMOVE TEMP. EROSION CONTROL PERMANENT VEGETATION TEMPORARY VEGETATION INFRASTRUCTURE CONSTRUCTION (INCL. UTILITIES) ACTIVITY CONSTRUCTION SCHEDULE INITIAL PERIMETER AND SEDIMENT STORAGE BMP's JUN 2013 AUG 2013 JUL 2013 MAINTENANCE OF BMP'S IMPAIRED STREAM SEGMENT NOTE. BEING LOCATED ADJACENT TO, AND DISCHARGING STORM WATER INTO AN IMPAIRED STREAM SEGMENT, THIS PROJECT SHALL COMPLY WITH THE FOLLOWING CLAUSE: NPDES PERMIT NO. GAR100003, PART III, SECTION C. 2. IN ORDER TO ENSURE THAT THE PERMITTEE'S DISCHARGES DO NOT CAUSE OR CONTRIBUTE TO A VIOLATION OF STATE WATER QUALITY STANDARDS, THE PLAN MUST INCLUDE THE FOLLOWING BEST MANAGEMENT PRACTICES (BMPS) FOR THOSE AREAS OF THE SITE WHICH DISCHARGE TO THE IMPAIRED STREAM SEGMENT: c. USE BAFFLES IN THE TEMPORARY SEDIMENT BASIN TO AT LEAST DOUBLE THE CONVENTIONAL FLOW PATH LENGTH TO THE OUTLET STRUCTURE. d. PLACE A LARGE SIGN (MINIMUM 4 FEET X 8 FEET) ON THE SITE VISIBLE FROM THE ROADWAY IDENTIFYING THE CONSTRUCTION SITE, THE PERMITTEE(S), AND THE CONTACT PERSON(S) AND TELEPHONE NUMBER(S). h. LIMIT THE TOTAL PLANNED SITE DISTURBANCE TO LESS THAN 50% IMPERVIOUS SURFACES (EXCLUDING ANY STATE MANDATED BUFFER AREAS FROM SUCH CALCULATIONS). p. INSTALL SOD FOR A MINIMUM 20 FOOT WIDTH, IN LIEU OF SEEDING, ALONG THE SITE PERIMETER WHEREVER STORM WATER MAY BE DISCHARGED. 0 60 120 GRAPHIC SCALE SCALE: 60' - SANITARY SEWER LINE - PROPERTY LINE - POWER LINE - WATER LINE LEGEND - IRON PIN SET - IRON PIN FOUND OH SS - CONTOUR LINE, EXISTING - CONTOUR LINE, FINISH W - CLEARING LIMIT LINE SEAL EROSION CONTROL CERTIFICATION I CERTIFY UNDER PENALTY OF LAW THAT THIS PLAN WAS PREPARED AFTER A SITE VISIT TO THE LOCATIONS DESCRIBED HEREIN BY MYSELF OR MY AUTHORIZED AGENT, UNDER MY SUPERVISION. BY HARRY HIGHBALL REGISTERED GEORGIA ENGINEER No. PE123456 LEVEL II CERTIFIED DESIGN PROFESSIONAL - CERTIFICATION NUMBER [PHONE REDACTED] FERTILIZER REQUIREMENTS TYPE OF SPECIES YEAR ANALYSIS OR EQUIVALENT N-P-K RATE N TOP DRESSING RATE COOL SEASON GRASSES FIRST SECOND MAINTENANCE 6-12-12 6-12-12 10-10-10 1500 lbs./ac. 1000 lbs./ac. 400 lbs./ac. 50-100 lbs./ac. *1,*2 - 30 lbs./ac. WARM SEASON GRASSES FIRST SECOND MAINTENANCE 6-12-12 6-12-12 10-10-10 1500 lbs./ac. 800 lbs./ac. 400 lbs./ac. 50-100 lbs./ac. *2,*6 50-100 lbs./ac. *2 30 lbs./ac. *1 APPLY IN SPRING FOLLOWING SEEDING. *2 APPLY IN SPLIT APPLICATIONS WHEN HIGH RATES ARE USED. *6 APPLY WHEN PLANTS GROW TO A HEIGHT OF 2 TO 4 INCHES. 3-10 2016 Edition ---PAGE BREAK--- A. DUNLOP OWNER HARRY HIGHBALL CONSULTING ENGINEERS COUNTY, STATE 336 LAND LOT 6th LAND DISTRICT MARCH 4, 2013 DATE JAN JACOBY DRAWN BY BARGAIN BUYS STORES DEVELOPMENT TIFT, GEORGIA REVISION NUMBER REQUESTED BY DATE DRAWING 6 EROSION AND SEDIMENT CONTROL NOTES SHEET #1 SEAL EROSION CONTROL CERTIFICATION I CERTIFY UNDER PENALTY OF LAW THAT THIS PLAN WAS PREPARED AFTER A SITE VISIT TO THE LOCATIONS DESCRIBED HEREIN BY MYSELF OR MY AUTHORIZED AGENT, UNDER MY SUPERVISION. BY HARRY HIGHBALL REGISTERED GEORGIA ENGINEER No. PE123456 LEVEL II CERTIFIED DESIGN PROFESSIONAL - CERTIFICATION NUMBER [PHONE REDACTED] 3-11 2016 Edition ---PAGE BREAK--- A. DUNLOP OWNER HARRY HIGHBALL CONSULTING ENGINEERS COUNTY, STATE 336 LAND LOT 6th LAND DISTRICT MARCH 4, 2013 DATE JAN JACOBY DRAWN BY BARGAIN BUYS STORES DEVELOPMENT TIFT, GEORGIA REVISION NUMBER REQUESTED BY DATE DRAWING 7 EROSION AND SEDIMENT CONTROL NOTES SHEET #2 SEAL EROSION CONTROL CERTIFICATION I CERTIFY UNDER PENALTY OF LAW THAT THIS PLAN WAS PREPARED AFTER A SITE VISIT TO THE LOCATIONS DESCRIBED HEREIN BY MYSELF OR MY AUTHORIZED AGENT, UNDER MY SUPERVISION. BY HARRY HIGHBALL REGISTERED GEORGIA ENGINEER No. PE123456 LEVEL II CERTIFIED DESIGN PROFESSIONAL - CERTIFICATION NUMBER [PHONE REDACTED] 3-12 2016 Edition ---PAGE BREAK--- A. DUNLOP OWNER HARRY HIGHBALL CONSULTING ENGINEERS COUNTY, STATE 336 LAND LOT 6th LAND DISTRICT MARCH 4, 2013 DATE JAN JACOBY DRAWN BY BARGAIN BUYS STORES DEVELOPMENT TIFT, GEORGIA REVISION NUMBER REQUESTED BY DATE DRAWING 8 EROSION AND SEDIMENT CONTROL NOTES SHEET #3 SEAL EROSION CONTROL CERTIFICATION I CERTIFY UNDER PENALTY OF LAW THAT THIS PLAN WAS PREPARED AFTER A SITE VISIT TO THE LOCATIONS DESCRIBED HEREIN BY MYSELF OR MY AUTHORIZED AGENT, UNDER MY SUPERVISION. BY HARRY HIGHBALL REGISTERED GEORGIA ENGINEER No. PE123456 LEVEL II CERTIFIED DESIGN PROFESSIONAL - CERTIFICATION NUMBER [PHONE REDACTED] 3-13 2016 Edition ---PAGE BREAK--- A. DUNLOP OWNER HARRY HIGHBALL CONSULTING ENGINEERS COUNTY, STATE 336 LAND LOT 6th LAND DISTRICT MARCH 4, 2013 DATE JAN JACOBY DRAWN BY BARGAIN BUYS STORES DEVELOPMENT TIFT, GEORGIA REVISION NUMBER REQUESTED BY DATE DRAWING 9 EROSION AND SEDIMENT CONTROL DETAILS SHEET #1 Co NOTES: 1. Avoid locating on steep slopes or at curves on public roads. 2. Remove all vegetation and other unsuitable material from the foundation area, grade, and crown for positive drainage. 3. Aggregate size shall be in accordance with National Stone Association R-2 (1.5"-3.5" Stone). 4. Gravel pad shall have a minimum thickness of 5. Pad width shall be equal full width at all points of vehicular egress, but no less than 20'. 6. A diversion ridge should be constructed when grade toward paved area is greater than 7. Install pipe under the entrance if needed to maintain drainage ditches. 8. When washing is required, it should be done on an area stabilized with crushed stone that drains into an approved sediment trap or sediment basin (divert all surface runoff and drainage from the entrance to a sediment control device). 9. Washracks and/or tire washers may be required depending on scale and circumstance. If necessary, washrack design may consist of any material suitable for truck traffic that remove mud and dirt. 10. Maintain area in a way that prevents tracking and/or flow of mud onto public rights-of-ways. This may require top dressing, repair and/or cleanout of any measures used to trap sediment. EXIT DIAGRAM 6" MIN. 6" MIN. FLOW FLOW ENTRANCE ELEVATION (IF NEEDED) DEFINITION Improving, constructing or stabilizing an open channel for water conveyance. CONDITIONS This standard applies to the improvement, construction or stabilization of open channels and existing ditches with drainage areas less than one square mile. This standard applies only to channels conveying intermittent flow, not to channels conveying a continuous, live stream. An adequate outlet for the modified channel length must be available for discharge by gravity flow. Construction or other improvements of the channel should not adversely affect the environmental integrity of the area and must not cause significant erosion upstream or flooding and/or sediment deposition CHANNEL LININGS AND STRUCTURAL MEASURES Where channel velocities exceed safe velocities for vegetated lining due to increased grade or a change in channel cross-section, or where durability of vegetative lining is adversely affected by seasonal changes, channel linings of rock, concrete or other durable material may be needed. Grade stabilization structures may also be needed. Channels may be stabilized by using one or more of the following methods: Vegetated Lining Vegetated lining shall be designed to resist erosion when the channel is flowing at the bankfull discharge or 25-year frequency discharge, whichever is the lesser. Temporary erosion control blankets or sod shall be used on all channels and concentrated flow areas to aid in the establishment of the vegetated lining. If a vegetated lining is desired in a channel with velocities between 5-10 ft/sec, permanent soil Ch Ch-1 Ch-2 Ch-3 reinforcement matting shall be used. Refer to specifications Ds3 - Disturbed Area Stabilization (With Permanent Vegetation), Ds4 - Disturbed Area Stabilization (With Sodding), and Mb - Matting and Blankets. Rock Riprap Lining Rock riprap shall be designed to resist displacement when the channel is flowing at the bankfull discharge or 25-year frequency discharge, whichever is the lesser. Rock riprap lining should be used when channel velocities are between 5 and 10 ft/sec. Dumped and machine placed riprap should not be installed on slopes steeper than 1-1/2 horizontal to 1 vertical. Rock shall be dense, resistant to the action of air and water, and suitable in all other respects for the purpose intended. Rock shall be installed according to standards specified in Riprap, Appendix C. A filter blanket layer consisting of an appropriately designed graded filter sand and/or gravel or geotextile material shall be placed between the riprap and base material. The gradation of the filter blanket material shall be designed to create a graded filter between the base material and the riprap. A geotextile can be used as a substitution for a layer of sand in a graded filter or as the filter blanket. Criteria for selecting an appropriate geotextile and guidance for recommended drop heights and stone weights are found in AASH-TO M288-96 Section 7.5, Permanent Erosion Control Specifications. Concrete Lining If a channel has velocities high enough to require a concrete lining (when channel velocities exceed 10 ft/sec), methods should be utilized to reduce the velocity of the runoff and reduce erosion at the outlet - a common problem created by the smooth, concrete lining. Refer to specification St - Storm Drain Outlet Protection for information regarding energy dissipators. If a concrete lining is chosen, it shall be designed according to currently accepted guides for structural and hydraulic adequacy. It must be designed to carry the required discharge and to withstand the loading imposed by site conditions. A separation geotextile should be placed under concrete linings to prevent undermining in the event of stress cracks due to settlement of the base material. The separation geotextile will keep the base material soils in place and minimize the likelihood of a system failure. Grade Stabilization Structures Grade stabilization structures are used to reduce or prevent excessive erosion by reduction of velocities in the watercourse or by providing structures that can withstand and reduce the higher velocities. They may be constructed of concrete, rock, masonry, steel, aluminum, or treated wood. These structures are constructed where the capability of earth and vegetative measures is exceeded in the safe handling of water at permissible velocities, where excessive grades or overall conditions are encountered or where water is to be lowered structurally from one elevation to another. These structures should generally be planned and installed along with or as a part of other erosion control practices. The structures shall be designed hydraulically to adequately carry the channel discharge and structurally to withstand loadings imposed by the site conditions. The structure shall meet requirements of Gr - Grade Stabilization Structure. SPECIFICATIONS 1. Where needed, all trees, brush, stumps and other objectionable materials shall be removed so they will not interfere with the construction or proper functioning of the channel. 2. Where possible, trees will be left standing, and stumps will not be removed. 3. Excavation shall be at the locations and grades shown on the drawings. The lining shall not compromise the capacity of the channel, e.g. the emergency spillway shall be over-excavated so that the lining will be flush with the slope surface. 4. The geotextile shall be placed on a smooth graded surface. The geotextile shall be placed in such a manner that it will not excessively stretch or tear upon placement of the overlying materials. Care should be taken to place the geotextile in intimate contact with the soil such that no void spaces exist between the underlying soil and the geotextile. 5. Construction plans will specifically detail the location and handling of spoils. Spoil material resulting from clearing, grubbing and channel excavation shall be disposed of in a manner which will: a. not cause an increase in flood stage, b. minimize overbank wash, c. not cause an adverse effect on the environmental integrity of the area, d. provide for the free flow of water between the channel and flood plain unless the valley routing and water surface profile are based on continuous dikes being installed, e. leave the right-of-way in the best condition feasible, and f. improve the aesthetic appearance of the site to the extent feasible. 6. Channel linings shall be established or installed immediately after construction or as soon as weather conditions permit. 7. Structures shall be installed according to lines and grades shown on the plan. The foundation for structures shall be cleared of all undesirable materials prior to the installation of the structures. 8. Materials used in construction shall be of permanency commensurate with the design frequency and life expectancy of the facility. 9. Earthfill, when used as a part of the structures, shall be placed according to the installation requirements for sediment basin embankments. 10. Construction operations shall be carried out in such a manner that erosion and air and water pollution will be minimized. State and local laws concerning pollution abatement shall be complied with. 11. Vegetation shall be established on all disturbed areas immediately after construction. If weather conditions cause a delay in establishing vegetation, the area shall be mulched in accordance with the standard for mulching. Refer to specification Ds1 - Disturbed Area Stabilization (With Mulching Only). Seeding, fertilizing and mulching shall conform to the standard for permanent vegetative cover. Refer to specification Ds3-Disturbed Area Stabilization (With Permanent Vegetation). 12. All temporary access roads or travelways shall be appropriately closed to exclude traffic. 13. Trees and other fallen natural vegetation not causing a deterrent to stream flow should be left for the purpose of habitat. Ds1 2. Wood waste (chips, sawdust or bark) shall be applied at a depth of 2 to 3 inches. Organic material from the clearing stage of development should remain on site, be chipped, and applied as mulch. This method of mulching can greatly reduce erosion control costs. 3. Cutback asphalt (slow curing) shall be applied at 1200 gallons per acre (or 1/4 gallon per sq.yd.). 4. Polyethylene film shall be secured over banks or stockpiled soil material for temporary protection. This material can be salvaged and reused. Applying Mulch When mulch is used without seeding, mulch shall be applied to provide full coverage of the exposed area. 1. Dry straw or hay mulch and wood chips shall be applied uniformly by hand or by mechanicalequipment. 2. If the area will eventually be covered with perennial vegetation, 20-30 pounds of nitrogen per acre in addition to the normal amount shall be applied to offset the uptake of nitrogen caused by the decomposition of the organic mulches. 3. Cutback asphalt shall be applied uniformly. Care should be taken in areas of pedestrian traffic due to problems of 'tracking in” or damage to shoes, clothing, etc. 4. Apply polyethylene film on exposed areas. Anchoring Mulch 1. Straw or hay mulch can be pressed into the soil with a disk harrow with the disk set straight or with a special “packer disk.” Disks may be smooth or serrated and should be 20 inches or more in diameter and 8 to 12 inches apart. The edges of the disk should be dull enough not to cut the mulch but to press it into the soil leaving much of it in an erect position. Straw or hay mulch shall be anchored immediately after application. Straw or hay mulch spread with special blower-type equipment may be anchored with emulsified asphalt (Grade AE-5 or SS-1). The asphalt emulsion shall be sprayed onto the mulch as it is ejected from the machine. Use 100 gallons of emulsified asphalt and 100 gallons of water per ton of mulch. Tackifers and binders can be substituted for emulsified asphalt. Please refer to specification Tb -Tackifers and Binders. Plastic mesh or netting with mesh no larger than one inch by one inch shall be installed according to manufacturer's specifications. 2. Netting of the appropriate size shall be used to anchor wood waste. Openings of the netting shall not be larger than the average size of the wood waste chips. 3. Polyethylene film shall be anchor trenched at the top as well as incrementally as necessary. DEFINITION Applying plant residues or other suitable materials, produced on the site if possible, to the soil surface. CONDITIONS Mulch or temporary grassing shall be applied to all exposed areas within 14 days of disturbance. Mulch can be used as a singular erosion control device for up to six months, but it shall be applied at the appropriate depth, depending on the material used, anchored, and have a continuous 90% cover or greater of the soil surface. Maintenance shall be required to maintain appropriate depth and 90% cover. Temporary vegetation may be employed instead of mulch if the area will remain undisturbed for less than six months. If an area will remain undisturbed for greater than six months, permanent vegetative techniques shall be employed. SPECIFICATIONS MULCHING WITHOUT SEEDING This standard applies to grades or cleared areas where seedings may not have a suitable growing season to produce an erosion retardant cover, but can be stabilized with a mulch cover. Site Preparation 1. Grade to permit the use of equipment for applying and anchoring mulch. 2. Install needed erosion control measures as required such as dikes, diversions, berms, terraces and sediment barriers. 3. Loosen compact soil to a minimum depth of 3 inches. Mulching Materials Select one of the following materials and apply at the depth indicated: 1. Dry straw or hay shall be applied at a depth of 2 to 4 inches providing complete soil coverage. One advantage of this material is easy application. SEAL EROSION CONTROL CERTIFICATION I CERTIFY UNDER PENALTY OF LAW THAT THIS PLAN WAS PREPARED AFTER A SITE VISIT TO THE LOCATIONS DESCRIBED HEREIN BY MYSELF OR MY AUTHORIZED AGENT, UNDER MY SUPERVISION. BY HARRY HIGHBALL REGISTERED GEORGIA ENGINEER No. PE123456 LEVEL II CERTIFIED DESIGN PROFESSIONAL - CERTIFICATION NUMBER [PHONE REDACTED] DEFINITION Small temporary barrier, grade control structure, or dam constructed across a swale, drainage ditch, or area of concentrated flow. CONDITIONS This practice is applicable for use in small open channels and is not to be used in a live stream. Specific applications include: 1. Temporary or permanent swales or ditches in need of protection during establishment of grass linings. 2. Temporary or permanent swales or ditches which, due to their short length of service or other reasons, cannot receive a permanent non-erodible lining for an extended period of time. 3. Other locations where small localized erosion and resulting sedimentation problems exist. SPECIFICATIONS The following types of check dams are used for this standard: Haybale Check Dams Staked and embedded hay-bales may be used as temporary check dams in concentrated flow areas while vegetation is becoming established. They should not be used where the drainage area exceeds one acre. Haybales should be embedded a minimum of 4 inches. (See Figure 6-10.3) Cd-Hb TYPICAL STRAW BALE CHECK DAM PLAN MIN. 18" MIN. 6" B B A SECTION A-A SECTION B-B SEE DETAIL FOR PLACEMENT OF BALE D C C Flow Flow Flow NOTES: 1. Bales should be bound with wire or nylon string and should be placed in rows with bale ends abutting the adjacent bales. 2. Remove #4 rebar after straw bales are no longer in place. 3. Point C of SECTION B-B should always be higher than Point D. 3-14 2016 Edition ---PAGE BREAK--- A. DUNLOP OWNER HARRY HIGHBALL CONSULTING ENGINEERS COUNTY, STATE 336 LAND LOT 6th LAND DISTRICT MARCH 4, 2013 DATE JAN JACOBY DRAWN BY BARGAIN BUYS STORES DEVELOPMENT TIFT, GEORGIA REVISION NUMBER REQUESTED BY DATE DRAWING 10 EROSION AND SEDIMENT CONTROL DETAILS SHEET #2 4. On slopes too steep for the safe operation of tillage equipment, the soil surface shall be pitted or trenched across the slope with appropriate hand tools to provide two places 6 to 8 inches apart in which seed may lodge and germinate. Hydraulic seeding may also be used. Individual Plants 1. Where individual plants are to be set, the soil shall be prepared by excavating holes, opening furrows, or dibble planting. 2. For nursery stock plants, holes shall be large enough to accommodate roots without crowding. 3. Where pine seedlings are to be planted, subsoil under the row 36 inches deep on the contour four to six months prior to planting. Subsoiling should be done when the soil is dry, preferably in August or September. Planting Hydraulic Seeding Mix the seed (innoculated if needed), fertilizer, and wood cellulose or wood pulp fiber mulch with water and apply in a slurry uniformly over the area to be treated. Apply within one hour after the mixture is made. Conventional Seeding Seeding will be done on a freshly prepared and firmed seedbed. For broadcast planting, use a cultipacker seeder, drill, rotary seeder, other mechanical seeder, or hand seeding to distribute the seed uniformly over the area to be treated. Cover the seed with 1/8 to 1/4 inch of soil for small seed and 1/2 to 1 inch for large seed when using a cultipacker or other suitable equipment. No-Till Seeding No-till seeding is permissible into annual cover crops when planting is done following maturity of the cover crop or if the temporary cover stand is sparse enough to allow adequate growth of the permanent (perennial) species. No-till seeding shall be done with appropriate no-till seeding equipment. The seed must be uniformly distributed and planted at the proper depth. Individual Plants Shrubs, vines and sprigs may be planted with appropriate planters or hand tools. Pine trees shall be planted manually in the subsoil furrow. Each plant shall be set in a manner that will avoid crowding the roots. Nursery stock plants shall be planted at the same depth or deeper than they grew at the nursery. The tips of vines and sprigs must be at or above the ground surface. Where individual holes are dug, fertilizer shall be placed in the bottom of the hole, two inches of soil shall be added and the plant shall be set in the hole. Ds3 2/1-6/15 3/15-6/1 1/1-12/31 4 LBS. 40 LBS. 75 LBS. 1.7 POUNDS 0.1 POUND 0.9 POUND SWITCH GRASS LESPEDEZA LOVE GRASS WEEPING 4/1-7/1 1/1-12/31 2/15-7/1 BLOCK SOD ONLY 60 LBS. 10 LBS. ONLY 1.4 POUNDS BLOCK SOD 0.2 POUND BAHIA BERMUDA CENTIPEDE SEEDING RATES FOR PERMANENT SEEDING * Unusual site conditions may require heavier seeding rates Seeding dates may need to be altered to fit temperature variations and conditions. SPECIES RATE Per RATE Per 1,000 sq.ft. Acre * PLANTING DATES DEFINITION The planting of perennial vegetation such as trees, shrubs, vines, grasses, or legumes on exposed areas for final permanent stabilization. Permanent perennial vegetation shall be used to achieve final stabilization.. CONDITIONS Permanent perennial vegetation is used to provide a protective cover for exposed areas including cuts, fills, dams, and other denuded areas. SPECIFICATIONS Grading and Shaping Grading and shaping may not be required where hydraulic seeding and fertilizing equipment is to be used. Vertical banks shall be sloped to enable plant establishment. When conventional seeding and fertilizing are to be done, grade and shape where feasible and practical, so that equipment can be used safely and efficiently during seedbed preparation, seeding, mulching and maintenance of the vegetation. oncentrations of water that will cause excessive soil erosion shall be diverted to a safe outlet. Diversions and other treatment practices shall conform with the appropriate standards and specifications. Seedbed Preparation Seedbed preparation may not be required where hydraulic seeding and fertilizing equipment is to be used. When conventional seeding is to be used, seedbed preparation will be done as follows: Broadcast plantings 1. Tillage at a minimum, shall adequately loosen the soil to a depth of 4 to 6 inches; alleviate compaction; incorporate lime and fertilizer; smooth and firm the soil; allow for the proper placement of seed, sprigs, or plants; and allow for the anchoring of straw or hay mulch if a disk is to be used. 2. Tillage may be done with any suitable equipment. 3. Tillage should be done on the contour where feasible. Mulching Mulch is required for all permanent vegetation applications. Mulch applied to seeded areas shall achieve 75% soil cover. Select the mulching material from the following and apply as indicated: 1. Dry straw or dry hay of good quality and free of weed seeds can be used. Dry straw shall be applied at the rate of 2 tons per acre. Dry hay shall be applied at a rate of 2 1/2 tons per acre. 2. Wood cellulose mulch or wood pulp fiber shall be used with hydraulic seeding. It shall be applied at the rate of 500 pounds per acre. or dry hay shall be applied (at the rate indicated above) after hydraulic seeding. 3. One thousand pounds of wood cellulose or wood pulp fiber, which includes a tackifier, shall be used with hydraulic seeding on slopes 3/4:1 or steeper. 4. Sericea lespedeza hay containing mature seed shall be applied at a rate of three tons per acre. 5. Pine straw or pine bark shall be applied at a thickness of 3 inches for bedding purposes. Other suitable materials in sufficient quantity may be used where ornamentals or other ground covers are planted. This is not appropriate for seeded areas. 6. When using temporary erosion control blankets or block sod, mulch is not required. 7. Bituminous treated roving may be applied on planted areas on slopes, in ditches or dry waterways to prevent erosion. Bituminous treated roving shall be applied within 24 hours after an area has been planted. Application rates and materials must meet Georgia Department of Transportation specifications. Wood cellulose and wood pulp fibers shall not contain germination or growth inhibiting factors. They shall be evenly dispersed when agitated in water. The fibers shall contain a dye to allow visual metering and aid in uniform application during seeding. Applying Mulch Straw or hay mulch will be spread uniformly within 24 hours after seeding and/or planting. The mulch may be spread by blower-type spreading equipment, other spreading equipment or by hand. Mulch shall be applied to cover 75% of the soil surface. Wood cellulose or wood fiber mulch shall be applied uniformly with hydraulic seeding equipment. Anchoring Mulch Anchor straw or hay mulch immediately after application by one of the following methods: 1. Emulsified asphalt can be sprayed uniformly onto the mulch as it is ejected from the blower machine or sprayed on the mulch immediately following mulch application when straw or hay is spread by methods other than special blower equipment. The combination of asphalt emulsion and water shall consist of a homogeneous mixture satisfactory for spraying. The mixture shall consist of 100 gallons of grade SS-1h or CSS-1h emulsified asphalt and 100 gallons of water per ton of mulch. Care shall be taken at all times to protect state waters, the public, adjacent property, pavements, curbs, sidewalks, and all other structures from asphalt discoloration. 2. Hay and straw mulch shall be pressed into the soil immediately after the mulch is spread. A special “packer disk”' or disk harrow with the disks set straight may be used. The disks may be smooth or serrated and should be 20 inches or more in diameter and 8 to 12 inches apart. The edges of the disks shall be dull enough to press the mulch into the ground without cutting it, leaving much of it in an erect position. Mulch shall not be plowed into the soil. 3. tackifiers or binders approved by GDOT shall be applied in conjunction with or immediately after the mulch is spread. tackifiers shall be mixed and applied according to manufacturer's specifications. Refer to Tb - Tackifiers and Binders. 4. Rye or wheat can be included with Fall and Winter plantings to stabilize the mulch. They shall be applied at a rate of one-quarter to one half bushel per acre. 5. Plastic mesh or netting with mesh no larger than one inch by one inch may be needed to anchor straw or hay mulch on unstable soils and concentrated flow areas. These materials shall be installed and anchored according to manufacturer's specifications. Irrigation Irrigation shall be applied at a rate that will not cause runoff. SPECIFICATIONS Grading and Shaping Excessive water run-off shall be reduced by properly designed and installed erosion control practices such as closed drains, ditches, dikes, diversions, sediment barriers and others. No shaping or grading is required if slopes can be stabilized by hand-seeded vegetation or if hydraulic seeding equipment is to be used. Seedbed Preparation When a hydraulic seeder is used, seedbed preparation is not required. When using conventional or handseeding, seedbed preparation is not required if the soil material is loose and not sealed by rainfall. When soil has been sealed by rainfall or consists of smooth cut slopes, the soil shall be pitted, trenched or otherwise scarified to provide a place for seed to lodge and germinate. Lime and Fertilizer Agricultural lime is required unless soil tests indicate otherwise. Apply agricultural lime at a rate of one ton per acre. Graded areas require lime application. Soils can be tested to determine if fertilizer is needed. On reasonably fertile soils or soil material, fertilizer is not required. For soils with very low fertility, 500 to 700 pounds of 10-10-10 fertilizer or the equivalent per acre (12-16 lbs./1,000 sq. ft.) shall be applied. Fertilizer should be applied before land preparation and incorporated with a disk, ripper or chisel. Seeding Select a grass or grass-legume mixture suitable to the area and season of the year. Seed shall be applied uniformly by hand, cyclone seeder, drill, cultipacker seeder, or hydraulic seeder (slurry including seed and fertilizer). Drill or cultipacker seeders should normally place seed one-quarter to one-half inch deep. Appropriate depth of planting is ten times the seed diameter. Soil should be “raked” to cover seed with soil if seeded by hand. Mulching Temporary vegetation can, in most cases, be established without the use of mulch. Mulch without seeding should be considered for short term protection. Refer to Ds1 - Disturbed Area Stabilization (With Mulching Only). Irrigation During times of drought, water shall be applied at a rate not causing runoff and erosion. The soil shall be thoroughly wetted to a depth that will insure germination of the seed. Subsequent applications should be made when needed. DEFINITION The establishment of temporary vegetative cover with fast growing seedings for seasonal protection on disturbed or denuded areas. CONDITIONS Temporary grassing, instead of mulch, can be applied to rough graded areas that will be exposed for less than six months. Temporary vegetative measures should be coordinated with permanent measures to assure economical and effective stabilization. Most types of temporary vegetation are ideal to use as companion crops until the permanent vegetation is established. eeded. Ds2 SEEDING RATES FOR TEMPORARY SEEDING SPECIES 4/1-7/15 3/1-8/1 RATE Per 4.1 pounds Wheat 9/15-2/1 3 bu. 3.9 pounds 1.4 pounds Rye Sudangrass Ryegrass 0.9 pound 0.1 pound 0.9 pound 0.9 pound 9/1-3/1 4/1-7/15 2/15-6/15 3/1-8/1 8/15-4/1 1/15-3/15 3 bu. 40 lbs. 60 lbs. 4 lbs. 40 lbs. 40 lbs. Weeping Lovegrass Annual Lespedeza Browntop Millet RATE Per 1,000 sq.ft. Acre * PLANTING DATES * Unusual site conditions may require heavier seeding rates Seeding dates may need to be altered to fit temperture variations and conditions. MATERIALS - Sod selected should be certified. Sod grown in the general area of the project is desirable. - Sod should be machine cut and contain 3/4" ±1/4" of soil, not including shoots or thatch. - Sod should be cut to the desired size within Torn or uneven pads should be rejected. - Sod should be cut and installed within 36 hours of digging. - Avoid planting when subject to frost heave or hot weather if irrigation is not available. - The sod type should be shown on the plans or installed according to Table 6-6.2. See Figure 6-4.1 for your Resource Area. Ds4 Table 6-6.2. Sod Planting Requirements MAINTENANCE • Re-sod areas where an adequate stand of sod is not obtained. • New sod should be mowed sparingly. Grass height should not be cut less than 2"-3" or as specified. • Apply one ton of agricultural lime as indicated by soil test or every 4-6 years. • Fertilize grasses in accordance with soil tests or Table 6-6.3. Table 6-6.3. Fertilizer Requirements for Sod Fertilizer Type (lbs./acre) Fertilizer Rate (lbs./acre) Fertilizer Rate Season 10-10-10 1000 .025 Fall Grass Varieties Resource Area Growing Season Bermudagrass Common Tifway Tifgreen Tiflawn M-L,P,C P,C P,C P,C Warm Weather Bahiagrass Pensacola P,C Warm Weather Centipede - P,C Warm Weather St. Augustine Common Bitterblue Raleigh C Warm Weather Zoysia Emerald Myer P,C Warm Weather Tall Fescue Kentucky M-L,P Cool Weather Types of Species Planting Year Fertilizer (N-P-K) Rate (lbs./acre) First Second Maintenance Cool Season Grasses 6-12-12 6-12-12 10-10-10 1500 1000 400 Nitrogen Top Dressing Rate (lbs./acre) 50-100 - 30 First Second Maintenance Warm Season Grasses 6-12-12 6-12-12 10-10-10 1500 800 400 50-100 50-100 30 DEFINITION A permanent vegetation using sods on highly erodible or critically eroded lands. CONDITIONS This application is appropriate for areas which require immediate vegetative covers, drop inlets, grass swales, and waterways with intermittent flow . CONSTRUCTION SPECIFICATIONS INSTALLATION Soil Preparation - Bring soil surface to final grade. Clear surface of trash, woody debris, stones and clods larger than Apply sod to soil surfaces only and not frozen surfaces, or gravel type soils. - Topsoil properly applied will help guarantee stand. Don’t use topsoil recently treated with herbicides or soil sterilants. - Mix fertilizer into soil surface. Fertilize based on soil tests or Table 6-6.1. For fall planting of warm season species, half the fertilizer should be applied at planting and the other half in the spring. Table 6-6.1. Fertilizer Requirements for Soil Surface Application - Agricultural lime should be applied based on soil tests or at a rate of 1 to 2 tons per acre. Installation - Lay sod with tight joints and in straight lines. Don’t overlap joints. Stagger joints and do not stretch sod. - On slopes steeper than 3:1, sod should be anchored with wooden or biodegradable pins or other approved methods. - Installed sod should be rolled or tamped to provide good contact between sod and soil. - Irrigate sod and soil to a depth of 4" immediately after installation. - Sod should not be cut or spread in extremely wet or dry weather. - Irrigation should be used to supplement rainfall for a minimum of 2-3 weeks. DEFINITION Controlling surface and air movement of dust on construction sites, roads, and demolition sites. CONDITIONS This practice is applicable to areas subject to surface and air movement of dust where on and off-site damage may occur without treatment. METHOD AND MATERIALS A. TEMPORARY METHODS Mulches. See standard Ds1 - Disturbed Area Stabilization (With Mulching Only). resins may be used instead of asphalt to bind mulch material. Refer to standard Tb-Tackifiers and Binders. Resins such as Curasol or Terratack should be used according to manufacturer's recommendations. Vegetative Cover. See standard Ds2 - Disturbed Area Stabilization (With Temporary Seeding). Spray-on Adhesives. These are used on mineral soils (not effective on muck soils). Keep traffic off these areas. Refer to standard Tb-Tackifiers and Binders. Tillage. This practice is designed to roughen and bring clods to the surface. It is an emergency measure which should be used before wind erosion starts. Begin plowing on windward side of site. Chisel-type plows spaced about 12 inches apart, spring-toothed harrows, and similar plows are examples of equipment which may produce the desired effect. Irrigation. This is generally done as an emergency treatment. Site is sprinkled with water until the surface is wet. Repeat as needed. Barriers. Solid board fences, snow fences, burlap fences, crate walls, bales of hay and similar material can be used to control air currents and soil blowing. Barriers placed at right angles to prevailing currents at intervals of about 15 times their height are effective in controlling wind erosion. Calcium Chloride. Apply at rate that will keep surface moist. May need retreatment. B. PERMANENT METHODS Permanent Vegetation. See standard Ds3 -Disturbed Area Stabilization (With Permanent Vegetation). Existing trees and large shrubs may afford valuable protection if left in place. Topsoiling. This entails covering the surface with less erosive soil material. See standard Tp - Topsoiling. Stone. Cover surface with crushed stone or coarse gravel. See standard Cr-Construction Road Stabilization. Du SEAL EROSION CONTROL CERTIFICATION I CERTIFY UNDER PENALTY OF LAW THAT THIS PLAN WAS PREPARED AFTER A SITE VISIT TO THE LOCATIONS DESCRIBED HEREIN BY MYSELF OR MY AUTHORIZED AGENT, UNDER MY SUPERVISION. BY HARRY HIGHBALL REGISTERED GEORGIA ENGINEER No. PE123456 LEVEL II CERTIFIED DESIGN PROFESSIONAL - CERTIFICATION NUMBER [PHONE REDACTED] 3-15 2016 Edition ---PAGE BREAK--- A. DUNLOP OWNER HARRY HIGHBALL CONSULTING ENGINEERS COUNTY, STATE 336 LAND LOT 6th LAND DISTRICT MARCH 4, 2013 DATE JAN JACOBY DRAWN BY BARGAIN BUYS STORES DEVELOPMENT TIFT, GEORGIA REVISION NUMBER REQUESTED BY DATE DRAWING 11 EROSION AND SEDIMENT CONTROL DETAILS SHEET #3 Sd3 Inflow Normal pool D d D/2 d/2 2 1 L L Riser A. B. Le = L Riser (outlet) L Inflow Examples: Plan Views - not to scale SEDIMENT BASIN BAFFLES Figure 6-22.2 Temporary Sediment Basin Baffle Details C. 1 L 2 L d/2 d D D/2 3' line Ground 6" 4' 8' o/c 4' x 8' x 1/2"exterior plywood or equivalent d/2 d Inflow 2a L 2b L 1b L 1a L D. Inflow Baffle Normal Pool Normal Pool Riser Riser = e L + 1a L = 2a L 2b L + 1b L Le = Total distance from the point of inflow around the baffle to the riser Le = L1 + L2 Le = L1 + L2 Posts - 4" square or 5" round minimum. Riser crest elevation DEFINITION A basin created by the construction of a barrier or dam across a concentrated flow area or by excavating a basin or by a combination of both. A sediment basin typically consists of a dam, a pipe outlet, and an emergency spillway. The size of the structure will depend upon the location, size of the drainage area, soil type, and rainfall pattern. CONDITIONS This practice applies to critical areas where physical site conditions, construction schedules, or other restrictions preclude the installation or establishment of erosion control practices to satisfactorily reduce runoff, erosion, and sedimentation. The structure may be used in combination with other practices and should remain in effect until the sediment-producing area is permanently stabilized. This standard applies to the installation of temporary (to be removed within 18 months) sediment basins on sites where: failure of the structure would not result in loss of life or interruption of use or service of public utilities, and the drainage area does not exceed 150 acres. SPECIFICATIONS Site Preparation Areas under the embankment and under structural works shall be cleared, grubbed, and stripped of topsoil. All trees, vegetation, roots and other objectionable material shall be removed and disposed of by approved methods. In order to facilitate clean-out or restoration, the pool area (measured at the top of the pipe spillway) will be cleared of all brush and trees. Cut-off Trench A cut-off trench will be excavated along the centerline of earth fill embankments. The minimum depth shall be 2 feet. The cut-off trench shall extend up both abutments to the riser crest elevation. The minimum bottom width shall be 4 feet, but wide enough to permit operation of compaction Sd3 PLAN VIEW BASIN SEDIMENT EMBANKMENT TOP OF TRASH RACK RISER WITH Rock Rip-Rap Outlet Spillway Principal SPILLWAY EMERGENCY 10.0 ft 8.0 ft 10 feet to 15 ft less than 10 ft CROSS SECTION block 3" - 4" stone holes with gravel 1/2" drainage for principal Riser pipe Trash rack Flood pool 1' min. and compacted placed in layers Anti-flotation Selected fill pipe spillway spillway Principal 1:1 2' deep, min. Cut-off trench collar Anti-seep outlet Stabilized with vegetation Embankment stabilized 2.5:1 or flatter Freeboard - 1' min. Emergency spillway crest Fill Height Minimum Top Width NOTES: 1. The emergency spillway shall be installed in undisturbed ground. 2. The emergency spillway must be constructed within a tolerance of 0.2 feet. BASIC COMPONENTS OF A TEMPORARY SEDIMENT BASIN equipment. The side slopes shall be no steeper than 1:1. Compaction requirements shall be the same as those for the embankment. The trench shall be drained during the backfilling and compaction operations. Embankment The fill material shall be taken from approved areas shown on the plans. It shall be clean mineral soil free of roots, woody vegetation, oversized stones, rocks or other objectionable material. Relatively pervious materials such as sand or gravel (Unified Soil Classes GW, GP, SW & SP) shall be placed in the section of the embankment. Areas on which fills are to be placed shall be scarified prior to placement of fill. The fill material shall contain sufficient moisture so that it can be formed by hand into a ball without crumbling. If water can be squeezed out of the ball, it is too wet for proper compaction. Fill material shall be placed in six-inch to eight-inch thick continuous layers over the entire length of the fill. Compaction shall be obtained by routing and hauling the construction equipment over the fill so that the entire surface of the fill is traversed by at least one wheel or tread track of the equipment or by the use of a compactor. The embankment shall be constructed to an elevation 5 percent higher than the design height to allow for settlement. Principal Spillway The riser shall be securely attached to the pipe or pipe stub by welding the full circumference making a watertight structural connection. The pipe stub must be attached to the riser at the same percent (angle) of grade as the outlet conduit. The connection between the riser and the riser base shall be watertight. All connections between pipe sections must be achieved by approved watertight band assemblies. The pipe and riser shall be placed on a firm, smooth foundation of impervious soil as the embankment is constructed. Breaching the embankment is unacceptable. Pervious materials such as sand, gravel, or crushed stone shall not be used as backfill around the pipe or anti-seep collar. The fill material around the pipe spillway shall be placed in four inch layers and compacted under and around the pipe to at least the same density as the adjacent embankment. Care must be taken not to raise the pipe from firm contact with its foundation when compacting under the pipe haunches. A minimum depth of two feet of hand compacted backfill shall be placed over the pipe spillway before crossing it with construction equipment. Emergency Spillway The emergency spillway shall be installed in undisturbed ground. The achievement of planned elevations, grades, design width, entrance and exit channel slopes are critical to the successful operation of the emergency spillway and must be constructed within a tolerance of ± 0.2 feet. If the emergency spillway requires erosion protection other than vegetation, the lining shall not compromise the capacity of the emergency spillway, e.g. the emergency spillway shall be over-excavated so that the lining will be flush with the slope surface. Vegetative Treatment Stabilize the embankment and all other disturbed areas in accordance with the appropriate permanent vegetative measure, Ds3, immediately following construction. In no case shall the embankment remain unstabilized for more than seven days. Refer to specifications Ds2, Ds3, and Ds4 - Disturbed Area Stabilization (Temporary Seeding, Permanent Vegetation and Sodding) respectively. Erosion and Pollution Control Construction operations will be carried out in such a manner that erosion and water pollution will be minimized. State and local law concerning pollution abatement shall be complied with. Safety State and local requirements shall be met concerning fencing and signs warning the public of hazards of soft sediment and floodwater. FINAL DISPOSAL When temporary structures have served their intended purpose and the contributing drainage area has been properly stabilized, the embankment and resulting sediment deposits are to be leveled or otherwise disposed of in accordance with approved sediment control plan. The proposed use of a sediment basin site will often dictate final disposition of the basin and any sediment contained therein. If the site is scheduled for future construction, then the embankment and trapped sediment must be removed, safely disposed of, and backfilled with a structural fill. When the basin area is to remain open space, the pond may be pumped dry, graded and backfilled. SEAL EROSION CONTROL CERTIFICATION I CERTIFY UNDER PENALTY OF LAW THAT THIS PLAN WAS PREPARED AFTER A SITE VISIT TO THE LOCATIONS DESCRIBED HEREIN BY MYSELF OR MY AUTHORIZED AGENT, UNDER MY SUPERVISION. BY HARRY HIGHBALL REGISTERED GEORGIA ENGINEER No. PE123456 LEVEL II CERTIFIED DESIGN PROFESSIONAL - CERTIFICATION NUMBER [PHONE REDACTED] Sd1-NS 18" Min 30" Min. 6" 2" 6' Max. o.c. Fabric Trench 6" NOTES: 1. Use steel or wood posts or as specified by the EROSION, SEDIMENTATION, AND POLLUTION CONTROL PLAN. 2. Height is to be shown on the EROSION, SEDIMENTATION, AND POLLUTION CONTROL PLAN. 18" Min 30" Min. Sd1-S 6" 2" 4' MAX. O.C. Fabric (Woven Wire Fence Backing) Trench 6" NOTES: 1. Use steel or wood posts or as specified by the EROSION, SEDIMENTATION, AND POLLUTION CONTROL PLAN. 2. Height is to be shown on the EROSION, SEDIMENTATION, AND POLLUTION CONTROL PLAN. 18" Min 30" Min. 18" Min 30" Min. 3-16 2016 Edition ---PAGE BREAK--- A. DUNLOP OWNER HARRY HIGHBALL CONSULTING ENGINEERS COUNTY, STATE 336 LAND LOT 6th LAND DISTRICT MARCH 4, 2013 DATE JAN JACOBY DRAWN BY BARGAIN BUYS STORES DEVELOPMENT TIFT, GEORGIA REVISION NUMBER REQUESTED BY DATE DRAWING 12 EROSION AND SEDIMENT CONTROL DETAILS SHEET #4 0.10' Spillway Flow Depth 1.00' Freeboard 4' Bottom Width ss 1 : 1 2' Deep, Core Trench x Antiseep Collar 353.25' Elev. 12" Dia. PVC Pipe 0.44' 5' ss ss Emergency Spillway Width 3 : 1 3 : 1 Storage 2 - No. 6 Steel Rebars Long x 18" 24" Concrete Antiflotation Block 18" 24" 3" - 4" Stone 48" 18" Figure 6-22.8 - Temporary Sediment Basin Cross-Sectional Detail 48" x Sd3 Rock Rip-Rap Outlet (Show dimensions and rock sizes) 54' 354.41' Elev. 31 Cu. Yd. 352.95' Elev. 25" 357.10' Elev. 1,225 Cu. Yd. 357.54' Elev. Emergency Spillway Crest Elevation 8' Perforate the entire riser with 1/2" holes Volume when Sediment Removal is Required Max. Volume of Basin Top of Dam Constructed Elev. = 358.64' Top of Dam Settled Elev. = 358.64' Profile Along Centerline of Emergency Spillway Grass Lining Cross-Sectional Detail of Emergency Spillway Figure 6-22.9 - Cross-Sectional Detail of Emergency Spillway Top of Dam Elev. = 358.64 ft Emergency Spillway Crest Elev. = 357.54 ft Freeboad= 1.00 ft (1ft. minimum) Hp = 0.10 ft Slope = 3:1 Bottom width = 8 ft Exit Channel Length = 10.00 ft Hp = 0.10 ft Length = 5.00 ft So = 33.33% Se = 33.33% Grass Lining SEAL EROSION CONTROL CERTIFICATION I CERTIFY UNDER PENALTY OF LAW THAT THIS PLAN WAS PREPARED AFTER A SITE VISIT TO THE LOCATIONS DESCRIBED HEREIN BY MYSELF OR MY AUTHORIZED AGENT, UNDER MY SUPERVISION. BY HARRY HIGHBALL REGISTERED GEORGIA ENGINEER No. PE123456 LEVEL II CERTIFIED DESIGN PROFESSIONAL - CERTIFICATION NUMBER [PHONE REDACTED] Sd3 Figure 6-22.5 C.S. Pipe t D Figure 6-22.6 Corrugated metal riser Pipe Flow B = 24" Square Base Drain (optional) Angle of stub to be shown Angle based on barrel grade 3 at 120° - 3/8" Stud with Nut and 2" O.D. Washer Removable Top - 10 Ga. Expanded Metal (Supports)-Use 5 Support Rods and Jam Nuts for Diameters 54" and Larger 3 at 120° - 1/2" Nut, Weld to C.S. Pipe 1/2" Jam Nut, 1/2" Bolt CONCRETE RISER BASE DETAIL Base Thickness = 18" 3 at 120° -5/8" Ø Rods 90° 2-#6 (min.) Bars placed at right angles and projecting into sides of riser to help anchor riser to concrete base TYPICAL TRASH RACK Sd3 0.3 Vo = V(So/S) LC LC LC 1. For Q, V, S relationship see the chart on the following page. NOTES: Exit Slope Entry Slope Flattest Slope in allowable for Channel below Control Section. (Table 6-22.4) Total Discharge, in cfs. Bottom Width of Earth Spillway at the Control Section, in feet. (Table 6-22.4) = = = = = = = So Se S V Q b Hp LEGEND: b 3 1 (So) S Exit Channel L Se Hp Water Surface Embankment Wing Dike Exit Channel Inlet Channel Exit Channel Berm (Note: Use care to keep all machinery and traffic out of the spillway discharge area to protect sod.) Optional with sod or riprap on wing dike (Note: Neither the location nor the alignment of the level portion has to coincide with the center line of dam.) Level Portion Figure 6-22.7 PROFILE ALONG CENTERLINE CROSS-SECTION OF CONTROL SECTION Level Control Section Level Control Section Embankment Excavated Earth Spillway Difference in Elevation between Crest of Earth Spillway at the Control Section and Water Surface in resevoir, in feet. Velocity, in feet per second, that will exist in Channel below Control Section, at Design Q, if constructed to slope that is shown (Table 6-22.4) 2. For a given Hp, a decrease in the exit slope as given in the table decreases spillway discharge, but increasing the exit slope from S does not increase discharge. If an exit slope (So) is steeper than S is used, then velocity (Vo) in the exit channel will increase according to the following relationship: Inlet Channel PLAN VIEW OF EARTH SPILLWAYS St blanket Filter Channel Pipe Outlet to Well-defined D Section AA A Plan A No Well-defined Channel Pipe Outlet to Flat Area- A a L Plan A d 3d Section AA blanket Filter D a L Sk 8" 15" SKIMMER SIDE SECTION VIEW SKIMMER FRONTAL SECTION VIEW SKIMMER PERSPECTIVE NOTE SKIMMER CONFIGURATION SHOWN IS TYPICAL. THE DESIGNER/ENGINEER MAY SUBMIT AN ALTERNATE SKIMMER DETAIL FOR REVIEW. PCV PIPE WITH HOLES IN UNDERSIDE. PVC END CAP PVC TEE PVC PIPE WATER SURFACE PVC PIPE HOLE IN ORIFICE PLATE FLEXIBLE HOSE TEMPORARY SEDIMENT POND SUPPLEMENT 3-17 2016 Edition ---PAGE BREAK--- A. DUNLOP OWNER HARRY HIGHBALL CONSULTING ENGINEERS COUNTY, STATE 336 LAND LOT 6th LAND DISTRICT MARCH 4, 2013 DATE JAN JACOBY DRAWN BY BARGAIN BUYS STORES DEVELOPMENT TIFT, GEORGIA REVISION NUMBER REQUESTED BY DATE DRAWING 13 EROSION AND SEDIMENT CONTROL DETAILS SHEET #5 A permanent vegetative cover using sods on highly erodable or critically eroded lands. Controlling surface and air movement of dust on construction site, roadways and similar sites. Establishing a permanent vegetative cover such as trees, shrubs, vines, grasses, or legumes on disturbed areas. Establishing a temporary vegetative cover with fast growing seedings on disturbed areas. Establishing temporary protection for disturbed areas where seedlings may not have a suitable growing season to produce an erosion retarding cover. Ds1 Ds3 Ds4 Ds1 Ds3 Ds4 DISTURBED AREA STABILIZATION (WITH MULCHING ONLY) DISTURBED AREA STABILIZATION (WITH PERM SEEDING) DISTURBED AREA STABILIZATION (SODDING) DUST CONTROL ON DISTURBED AREAS DISTURBED AREA STABILIZATION (WITH TEMP SEEDING) Ds2 Ds2 Du Du GEORGIA FOR SOIL EROSION AND SEDIMENT CONTROL PRACTICES UNIFORM CODING SYSTEM GEORGIA SOIL AND WATER CONSERVATION COMMISSION STRUCTURAL PRACTICES A barrier to prevent sediment from leaving the construction site. It may be sandbags, bales of straw or hay, brush, logs and poles, gravel, or a silt fence. A basin created by excavation or a dam across a waterway. The surface water runoff is temporarily stored allowing the bulk of the sediment to drop out. A crushed stone pad located at the construction site exit to provide a place for removing mud from tires thereby protecting public streets. Improving, constructing or stabilizing an open channel, existing stream, or ditch. A small temporary barrier or dam constructed across a swale, drainage ditch or area of concentrated flow. Ch Co Sd1 Sd3 CHANNEL STABILIZATION CONSTRUCTION EXIT SEDIMENT BARRIER TEMPORARY SEDIMENT BASIN Co Sd3 A paved or short section of riprap channel at the outlet of a storm drain system preventing erosion from the concentrated runoff. St STORMDRAIN OUTLET PROTECTION St CODE PRACTICE DETAIL DESCRIPTION MAP SYMBOL CODE PRACTICE DETAIL DESCRIPTION MAP SYMBOL VEGETATIVE PRACTICES Cd CHECKDAM Sk A buoyant device that releases/drains water from the surface of sediment ponds, traps, or basins at a controlled rate of flow. FLOATING SURFACE SKIMMER Sk SEAL EROSION CONTROL CERTIFICATION I CERTIFY UNDER PENALTY OF LAW THAT THIS PLAN WAS PREPARED AFTER A SITE VISIT TO THE LOCATIONS DESCRIBED HEREIN BY MYSELF OR MY AUTHORIZED AGENT, UNDER MY SUPERVISION. BY HARRY HIGHBALL REGISTERED GEORGIA ENGINEER No. PE123456 LEVEL II CERTIFIED DESIGN PROFESSIONAL - CERTIFICATION NUMBER [PHONE REDACTED] 3-18 2016 Edition ---PAGE BREAK--- 2016 Edition 3-33 POST-CONSTRUCTION STORMWATER: The term post-construction stormwater is used to distinguish stormwater practices used during the active construction phase (sometimes referred to as “construction stormwater”) from those that are used on a permanent basis to con­ trol runoff once construction is complete (“post- construction stormwater”). Post-construction stormwater includes site planning and structural and non-structural prac­ tices that intercept, treat, and often reduce the volume of runoff from land development sites. Collectively, these practices are referred to as “post-construction BMPs (Best management practice).” As with construction, other permits may apply, such as MS4 minimum measure Recent trends in post-construction stormwater management that make ES&PC Plan coordina­ tion all the more important include: •The use of better site design and green infrastructure techniques to help satisfy post-construction stormwater requirements. hese approaches involve the use of open space, vegetated areas, impervious cover disconnection, and other site planning and design techniques. For the ES&PC Plan, this can mean more “do not disturb” zones and the need to avoid disturbing and com­ pacting soils in dispersed areas around a development site. •The use of small-scale, distributed (low- impact development) practices that treat runoff closer to its source. Many of these practices rely on the underlying soil to infil­ trate at least part of the runoff. Some may be on individual lots, within community open space, or within drainage easements. For the ES&PC Plan, this means a finer level of control for the limits of disturbance so that the performance of the ultimate post- construction practices is not compromised during the construction phase. •More elaborate design parameters for stormwater ponds and wetlands that may begin their lives as ES&PC basins. Often, the post-construction configuration will involve pretreatment forebays, flowpath and Introduction It is essential to coordinate post-construc­ tion stormwater planning with the design and implementation of Erosion Sedimentation and Pollution Control (ES&PC) Plans. This chapter provides general guidance on this coordination. Post-construction stormwater management in Georgia is largely governed by: •The Georgia Stormwater Management Manual (Volumes 1 and 2, 2001) •The Georgia Coastal Stormwater Supplement (2009) However, it is crucial for plan preparers to also check local requirements for local adaptations to post-construction stormwater requirements. Before proceeding, it may be helpful to pro­ vide some simple definitions in order to distin­ guish what is meant by “erosion and sediment control” and “post-construction stormwater” in the context of this section: EROSION & SEDIMENTATION CONTROL (ES&PC) PLANS: The application of planning approaches and practices during the construction phase in accor­ dance with Act 599 and the Manual for Erosion and Sediment Control in Georgia. These practic­ es generally apply during the active construction phase of a land disturbing activity, including land clearing, filling, excavation, soil movement, con­ struction, and other activities defined in the Act. It should be noted that construction phase plans and practices must also be coordinated with other applicable permits, such as the NPDES General Permits for Discharge from Construction Activities and, for MS4 communities, minimum measure Coordinating Erosion and Sediment Control With Post-Construction Stormwater Management ---PAGE BREAK--- 2016 Edition 3-34 geometry requirements, multi-stage riser structures, and other features that the designer must consider when designing the initial ES&PC basin. A detailed conversion plan is needed for the practice to succesfully meet both ES&PC and post-construction needs. All of these trends make it essential for a higher level of coordination during site planning and implementation of ES&PC Plans in the field. There are several key principles that apply to the coordination between ES&PC and post-con­ struction stormwater, as outlined below: Principle Limits on the Limits of Disturbance (LOD): The LOD on the ES&PC Plan must respect natural areas, open spaces, undisturbed vegetat­ ed areas, and the footprints of certain BMPs that are part of the post-construction stormwater plan. LODs that make sense for only the construction phase can compromise the integrity of the post- construction approach. Also, LOD boundaries may need more careful fencing, signage, and monitoring during construction. Principle Soil Structure as a Post-Construction Stormwater Tool: Many post-construction practices rely on the underlying soil structure to allow the BMPs to function as designed. This is obviously true for practices designed to infiltrate runoff, but also ap­ plies to post-construction BMPs that have an un­ derdrain some bioretention, dry swale, and porous pavement designs). Care must be taken during the construction phase to avoid compact­ ing soils in the vicinity of post-construction BMP installations. Principle Diversions: In many cases, construction runoff can seri­ ously compromise post-construction BMPs, even before they are installed. Sediment-laden construction runoff can damage soils intended for infiltration or filtration and can clog rock and other materials intended for use in the post-con­ struction BMP. As such, the ES&PC Plan should include diversions to prevent construction runoff from entering certain areas associated with post- construction BMP implementation. Principle Conversion Details: In many cases, ES&PC and post-construction practices can be co-located. This has advan­ tages in terms of the efficiency of the design, and can also help the post-construction BMP be­ cause the conversion cannot take place until the erosion control function is complete (thus avoid­ ing premature installation of the post-construc­ tion features). However, given the increasingly sophisticated nature of post-construction BMP design, a detailed conversion plan is needed as part of the ES&PC Plan to make sure that post-construction volumes, BMP geometry, riser configuration, access, and other features are adhered to. The conversion plan should also be very specific about the timing and sequencing of conversion activities with ongoing land distur­ bance and stabilization. Principle Communication & Coordination: In order to coordinate erosion and sediment control with post-construction stormwater, a local program should strive to integrate activities such as plan review, site inspections, administration of performance bonds, adoption of technical stan­ dards and policies, and training and communica­ tion for the regulatory community. ---PAGE BREAK--- 2016 Edition 3-35 Figure 1 shows several typical points of coordination between ES&PC and post-construction stormwater. From: Managing Stormwater in Your Community, EPA Publication No.: 833-R-08-001 (CWP, 2008) ---PAGE BREAK--- 2016 Edition 3-36 Erosion & Sediment Control Considerations When Using Post-Construction Practices From Georgia’s Stormwater Manuals Tables 1 and 2 provide more specific guidance on ES&PC considerations for practices and BMPs con­ tained in both the Georgia Stormwater Management Manual (GSMM) and Georgia Coastal Stormwater Supplement (CSS): Table 1 Provides ES&PC considerations for post-construction practices related to natural resources protection, better site design, and other site planning practices that are authorized or used to obtain post- construction credits in the GSMM and CSS. Table 2 Lists similar considerations for structural post-construction BMPs, such as bioretention, porous pavement, vegetated swales, infiltration trenches, and stormwater ponds and wetlands. Table 1. ES&PC Considerations for Specific Natural Resource Protection & Site Planning Practices in the GSMM & CSS Natural Resource or Site Planning Practice Reference to the GSMM & CSS ES&PC Considerations Natural Area Conservation: Protect floodplains, slopes, porous/erodible soils, aquatic resources, groundwater recharge zones GSMM: Volume 1: Section 4.5.2 Volume 2: Sections 1.4.1 & 1.4.2 (various practices) CSS : Section 7.6.1 & 7.6.2 •Clearly identify all natural resources area boundaries on ES&PC Plans as being outside of the LOD. •Specify use of temporary construction fencing at LOD. •Diversions or other mea­ sures may be needed to divert construction runoff away from the area. •Install temporary fencing and signage at the beginning of land disturbing activities. •Monitor construction activities to ensure that heavy equipment does not enter natural resource areas. Stream/Riparian Buffers: Protect or restore vegetated area adjacent to streams and aquatic resources GSMM: Volume 1: Section 4.5.3 Volume 2: Section 1.4.2 (Practice CSS : Section 7.6.1 & 7.6.2 •Clearly identify all stream buffer boundaries on ES&PC Plans as being outside of the LOD. •See above for other guidelines under “Natural Area Conservation.” ---PAGE BREAK--- 2016 Edition 3-37 Table 1. ES&PC Considerations for Specific Natural Resource Protection & Site Planning Prac­ tices in the GSMM & CSS (continued) Natural Resource or Site Planning Practice Reference to the GSMM & CSS ES&PC Considerations Disconnection of post-con­ struction Impervious Cover: direct impervious cover to downgradient pervious areas as sheet flow or over­ land flow filter paths GSMM: Volume 1: Section 4.5.5 Volume 2: Section 1.4.2 (Practices #17, 20) ; Section 3.3.1 (Filter Strip) CSS : Sections 7.8.5 & 7.8.6 •Identify on ES&PC Plans all pervious ar­ eas that will receive runoff from upgradient impervious or developed areas. •Avoid compaction of pervious areas with heavy equipment during construction; use temporary fencing as necessary. •Diversions or other measures may be needed to divert construction runoff away from the pervious areas. •Make sure that all subcontractors know about the areas. •It is acknowledged that it may not be practi­ cal to prevent disturbance or compaction of ALL of these pervious receiving areas on a site small areas on individual lots). Pervious receiving areas that ARE compacted during construction should be restored by tilling and adding compost, as per Section 7.8.1 of the CSS or similar guidance. Grass/Vegetated Channels: direct runoff from developed areas to vegetated chan­ nels instead of storm sewer systems GSMM: Volume 1: Section 4.5.4 Volume 2: Section 1.4.2 (Practice #18, 19) ; Section 3.3.2 (Grass Channel) CSS: Section 7.8.7 •Similar to Impervious Cover Disconnection, vegetated/grass channels and drainageways should be identified on ES&PC Plans and marked in the field to avoid disturbance and compaction. •Of course, roadside channels will be disturbed during construction; soil restoration should fol­ low post-construction plans. Other Better Site Design Practices that Reduce Site Grading & Disturbance: reduce limits of clearing, reduce impervious cover, more compact development design GSMM: Volume 1: Section 4.3 Volume 2: Section 1.4 CSS : Section 7.7 •Ensure that reduced development footprint translates to ES&PC Plan by matching limits of disturbance with post-construction design and layout. •Clearly mark limits of disturbance; use tempo­ rary construction fencing as necessary. ---PAGE BREAK--- 2016 Edition 3-38 Table 2. ES&PC Considerations for Specific Structural Post-Construction BMPs in the GSMM & CSS Post-Construction BMP Reference to the GSMM & CSS ES&PC Considerations Bioretention, Infiltration, Porous Pavement WITHOUT an underdrain system (designed for infiltration into underyling soils) GSMM Volume 2: Sections 3.2.3 (Bioretention), 3.2.5 (Infiltration), 3.3.7 (Porous Concrete), 3.3.8 (Modular Porous Pavement System) CSS : Sections 7.8.4 (Permeable Pavements), 7.8.9 (Rain Gardens), 7.8.11 (Dry Wells), 7.8.13 (Bioretention), 7.8.14 (Infiltration), 8.6.6 (Swales) •Clearly show post-construction practice foot­ prints on ES&PC Plan. Usually, these areas should be outside of the LOD (with the excep­ tion of porous pavement), unless they are used as small, temporary sediment traps as per the guidelines in Table 3. •Mark practice footprint areas in the field with temporary fencing and signage. •Monitor construction activities to ensure that heavy equipment does not enter practice foot­ print areas. •All contributing drainage areas (CDAs) to the practice MUST be fully stabilized and vegetated prior to installation of post-construction BMP. •In addition, runoff from the CDA can be diverted around the post-construction BMP footprint and supplemental ES&PC measures silt fence/ barriers around the perimeter of the practice) can be used to prevent erosion into the practice from the CDA or practice side slopes as they are being graded. Bioretention, Dry Swale, Infiltration, Porous Pave­ ment WITH an underd­ rain system (designed for underdrain to discharge to storm sewer) GSMM Volume 2: Sections 3.2.3 (Bioretention), 3.2.6 (Enhanced Swales) CSS: Sections 7.8.4 (Permeable Pavements), 7.8.13 (Bioretention), 7.8.10 (Stormwater Planters), 7.8.15 (Dry Swales) •Clearly show post-construction practice foot­ prints on ES&PC Plan. Usually, these areas should be outside of the LOD (with the excep­ tion of porous pavement), unless they are used as small, temporary sediment traps as per the guidelines in Table 3. •If outside of the LOD, mark practice footprint areas in the field with temporary fencing and signage. •Monitor construction activities to ensure that heavy equipment does not enter practice foot­ print areas. •Similar to practices without underdrains, the CDA must be stabilized and supplemen­ tal ES&PC measures silt fence/barriers around the perimeter of the practice) can be used to prevent sediment from entering the post- construction BMP. ---PAGE BREAK--- 2016 Edition 3-39 Table 2. ES&PC Considerations for Specific Structural Post-Construction BMPs in the GSMM & CSS (Continued) Post-Construction BMP Reference to the GSMM & CSS ES&PC Considerations Conversions from temporary ES&PC practice to post-construction BMP GSMM Volume 2: Sections 3.2.1 (Stormwater Ponds) 3.2.2 (Stormwater Wetlands) CSS: Sections 8.6.1 (Stormwater Ponds) 8.62 (Stormwater Wetlands) •For post-construction stormwater designs that in­ clude stormwater ponds or wetlands, it is likely that the practice will be installed initially as a temporary ES&PC basin. •ES&PC Plans should incorporate the design considerations outlined in the following section on co-locating and converting ES&PC practices to post-construction BMPs. •The timing of conversion from temporary to permanent practices depends on exposed areas and continued land disturbance in the CDA. The ES&PC Plan should have a detailed phasing plan that clearly explains this sequence. Co-Locating & Converting ES&PC Practices to Post-Construction BMPs Previous sections discuss the prospect of co-locating ES&PC and post-construction prac­ tices. While this cannot be done in all cases, it is an acceptable approach as long as certain guidelines are followed to ensure the integrity of the post-construction BMP. In addition, there are some notable advantages to co-locating practic­ es, the chief one being that the post-construction conversion cannot take place until the construc­ tion-phase ES&PC function is complete. This is important because one of the chief causes of failure for post-construction BMPs is premature installation and the introduction of construction sediments into the practice. There are many bio­ retention, infiltration, and other practices where this has been a serious concern. See Figure 2 for examples. The other advantage for co-location is that it is straight-forward, can be implemented easily by the contractor, and may lead to cost savings. Given these advantages to co-location, there are circumstances where it should not be done, including: • Post-construction BMPs that have too small of a drainage area and/or are in a location that is not conducive for an ES&PC trap. •Post-construction BMPs where the local plan reviewer deems that construction activity will compact and damage underlying soils to an extent that performance of the post-con struction BMP will be compromised. •Post-construction BMPs where timing and sequencing of construction phases will not allow the conversion to take place in the proper sequence so that the practice cannot fulfill its post-construction treatment objectives. •Other situations where the local authority, plan reviewer, designer, and/or contractor believes that co-location will compromise the ES&PC and/or post-construction plan implementation. Where co-location is a viable option, there are generally two types of practices where conver­ sion from ES&PC to post-construction can take place: 1. Smaller-scale sediment traps (generally with drainage areas less than 3 acres) that can be converted to bioretention, dry swales, or surface sand filter BMPs. See Table 3 for specific conversion guidance. ---PAGE BREAK--- 2016 Edition 3-40 2. Larger-scale sediment basins with larger drainage areas that can be converted to post-construction stormwater ponds or wetlands. See Table 4. Figure 2 shows examples of ES&PC practice conversions to post-construction BMPs. Table 3. Conversion of Smaller-Scale Sediment Traps (generally with drainage areas less than 3 acres) to Bioretention, Dry Swales, or Surface Sand Filter BMPs. Topic Conversion Guidance Drainage Areas Drainage areas should be limited by the appropriate post-construction BMP design specifications, even if construction phase drainage areas could be larger. This means that sites may have to be divided into smaller drainage areas with use of multiple ES&PC traps and other ES&PC measures. Grading to Blend Into Topography Some temporary ES&PC practices are graded onto slopes, have steep embank­ ments or side slopes, and otherwise don’t blend into the surrounding topography. These types of practices are not good candidates to convert to post-construction BMPs, unless regrading is part of the conversion plan. A sounder approach is to design the temporary ES&PC practice so that this type of regrading is not neces­ sary, which may include changing the footprint, grading, slopes, and other features of the ES&PC practice. Stabilizing the Drainage Area Make sure the contributing drainage area (CDA) is stabilized prior to conversion. This is a good thing about using ES&PC traps, since they cannot be taken out until their erosion control function is complete. Therefore, the tendency to prematurely install post-construction practices is lessened. The conversion can proceed when site inspectors indicate that the CDA is properly stabilized. In addition to CDA sta­ bilization, other supplemental ES&PC measures may be warranted, such as divert­ ing flow around the practice during the conversion process and using silt fence or matting/sod on side slopes of the practice. Remove Construction Sediments All construction sediments should be removed as the first step in the conversion process. This may also involve dewatering the ES&PC practice using an approved dewatering and sediment capture method dirt bags, sediment traps). Excavate Below the ES&PC Practice Bottom Elevation The bottom of the post-construction practice should be at least one foot lower than the temporary ES&PC bottom elevation. This is so that the bottom of the post- construction BMP will be in undisturbed soils that are not impacted by construction activities. During excavation to the post-construction design elevation, scarify or rip the underlying soil to promote infiltration. Installing Underdrains If the post-construction practice design has an underdrain, decide when to install the underdrain. Usually this will be done as part of the conversion (after the con­ struction phase). However, if the underdrain goes through an impounding structure or berm that will stay in place with the post-construction BMP, it may be best to install the underdrain with the initial ES&PC practice, cover it with heavy gage plas­ tic, and then fill on top to reach the desired bottom elevation of the ES&PC prac­ tice. This will prevent having to breach the impounding structure or berm to install an underdrain system during the conversion process. At the time of conversion, the overlying soil and plastic can be removed, exposing the underdrain system, at which point the desired soil or filter layers can be placed on top of the underdrain. ---PAGE BREAK--- 3-41 2016 Edition Table 3. Conversion of Smaller-Scale Sediment Traps (generally with drainage areas less than 3 acres) to Bioretention, Dry Swales, or Surface Sand Filter BMPs. (continued) Topic Conversion Guidance Proceed to Install Post-Construction BMP Install the practice as per the approved post-construction plans. Some minor grading or adjustments to the footprint may be needed to meet the post-con­ struction design. Be Aware of Easement and Post-Construction Practice Location If the post-construction BMP is supposed to be located within a drainage ease­ ment or in another specific location common area in a subdivision), it is very important to make sure that the final practice is within the specified area in order to avoid costly relocation of the practice. Table 4. Conversion of Larger Scale ES&PC Sediment Basins to Post-Construction Stormwater Ponds and Wetlands Topic Conversion Guidance Timing/Sequencing Generally, ES&PC basins cannot be converted to a post-construction configura­ tion until the contributing drainage area (CDA) is fully developed and stabilized. However, phasing plans can incorporate additional upgradient ES&PC practices if certain portions of the CDA will be disturbed subsequent to the conversion. This is likely the case with multi-phase development projects, commercial subdi­ visions, etc. Sediment Removal Construction sediment will have to be removed from the basin before conver­ sion to a post-construction BMP. Additional grading may be needed to meet the design standards for the post-construction configuration. Volume & Design Elevations Sizing rules are different for ES&PC basins and post-construction BMPs. The ES&PC basin may be larger or smaller than the post-construction practice, so additional grading is likely needed for the conversion. A common problem with conversions is that not all of the construction sediment is removed so that the post-construction elevations are incorrect. Contractors should always check de­ sign elevations for the post-construction BMP. Pond Geometry Compared to an ES&PC basin, a post-construction practice may have a lon­ ger flow path (3:1 recommended), multiple cells, larger surface area, shallower side slopes 3:1), deeper or shallower pool depths, safety benches around permanent pools, and other design features. The ES&PC basin should at least consider the overall footprint and general depth of the post-construction pond so that major grading can be avoided in the conversion process. Pre-Treatment Most post-construction ponds will incorporate one or more forebays for pretreat­ ment. The forebays can be constructed as part of the ES&PC basin, but it may be preferable to install them as part of the conversion to avoid the cost of clean­ ing them out, repairing or replacing rock spillways, etc. In either case, the foot­ print of the forebay should be incorporated into the ES&PC basin footprint. ---PAGE BREAK--- 3-42 2016 Edition Table 4. Conversion of Larger Scale ES&PC Sediment Basins to Post-Construction Stormwater Ponds and Wetlands (continued) Topic Conversion Guidance Risers & Spillways The post-construction practice design will adhere to certain safety features and riser designs (likely multi-stage risers to address water quality, channel protec­ tion, and flood protection). The designer should consider constructing the post- construction design as part of the ES&PC basin, and then modifying it for the construction phase. For instance, risers can be perforated during construction, and then the perforations plugged as part of the conversion. Certain orifices will likely need to be temporarily plugged during construction. In addition, the spill­ way and freeboard requirements may be different for the post-construction pond, and relevant design elevations should be used for the temporary ES&PC basin, unless this is specifically addressed otherwise in the conversion plan. Dewatering Drains Certain post-construction pond or wetland designs may call for dewatering drains so that pools can be drained to remove sediment or for maintenance. With regard to constructability, it may be best to install drains with the original ES&PC basin, and make sure they do not get clogged during construction. Rock Weirs, Spillways, Outlet Protection Rock features may be part of the ES&PC and/or post-construction practice. However, it is likely that they will get filled with sediment during construction, so will have to be replaced or rebuilt as part of the conversion. Maintenance Access While temporary ES&PC basins only need to be accessed during the construc­ tion phase, post-construction ponds require permanent maintenance access, so this should be planned for during construction. Landscaping Most post-construction ponds will have a landscaping plan. Obviously, the landscaping should be installed during the conversion, and not during the active construction phase. ---PAGE BREAK--- 3-43 2016 Edition Figure 2. Typical ES&PC to Post-Construction Conversions as well as Common Pitfall Conversion of a small-scale sediment trap to bioretention. The photos shows adding an underd­ rain system. Conversion of a sediment basin to a bioretention area. The original riser acts as the overflow structure for the bioretention practice. Post-construction conversion called for the creation of sediment forebay in this larger scale pond. A major issue with conversions is timing. Premature installation of the post-construction practice can result in damage from construction sediments. Conclusion Increasingly, it is important to coordinate ES&PC planning and implementation with post- construction stormwater plans. A coordinated plan will help both phases (construction and post-construction) to proceed in a logical, well thought-out way that avoids costly redesigns and work delays. The principles of adjusting the limits of distur­ bance, protecting soil structure associated with post-construction BMPs, diverting construction runoff around important post-construction areas, developing detailed conversion plans for ES&PC to post-construction BMPs, and coordination and communication among plan reviewers, design professionals, inspectors, and contractors, will help achieve this integration of ES&PC and post- construction stormwater. ---PAGE BREAK--- 3-44 2016 Edition Low Impact Development (LID) What is low impact development (LID)? LID includes a variety of practices that mimic or preserve natural drainage processes to manage stormwater. LID practices typically retain rain water and encourage it to soak into the ground rather than allowing it to run off into ditches and storm drains where it would other­ wise contribute to flooding and pollution prob­ lems (see www.epa.gov/nps/lid). Excerpt from US EPA Low Impact Development (LID) a Literature Review Introduction Low impact development (LID) is a relatively new concept in stormwater management. LID techniques were pioneered by Prince George’s County, Maryland, in the early 1990's, and sev­ eral projects have been implemented within the state. Some LID principles are now being applied in other parts of the country, however, the use of LID is infrequent and opportunities are often not investigated. LID is a site design strategy with a goal of maintaining or replicating the pre-development hydrologic regime through the use of design techniques to create a functionally equivalent hy­ drologic landscape. Hydrologic functions of stor­ age, infiltration, and ground water recharge, as well as the volume and frequency of discharges, are maintained through the use of integrated and distributed micro-scale stormwater retention and detention areas, reduction of impervious surfac­ es, and the lengthening of flow paths and runoff time (Coffman, 2000). Other strategies include the preservation/protection of environmentally sensitive site features such as riparian buffers, wetlands, steep slopes, valuable (mature) trees, flood plains, woodlands and highly permeable soils. LID principles are based on controlling storm­ water at the source by the use of micro-scale controls that are distributed throughout the site. This is unlike conventional approaches that typi­ cally convey and manage runoff in large facilities located at the base of drainage areas. These multifunctional site designs incorporate alterna­ tive stormwater management practices such as functional landscape that act as stormwater facilities, flatter grades, depression storage and open drainage swales. This system of controls can reduce or eliminate the need for a central­ ized Best Management Practice (BMP) facility for the control of stormwater runoff. Although tradi­ tional stormwater control measures have been documented to effectively remove pollutants, the natural hydrology is still negatively affected (inadequate base flow, thermal fluxes or flashy hydrology), which can have detrimental effects on ecosystems, even when water quality is not compromised (Coffman, 2000). LID practices offer an additional benefit in that they can be in­ tegrated into the infrastructure and are more cost effective and aesthetically pleasing than tradition­ al, structural stormwater conveyance systems. Conventional stormwater conveyance sys­ tems are designed to collect, convey and dis­ charge runoff as efficiently as possible. The intent is to create a highly efficient drainage system, which will prevent on lot flooding, pro­ mote good drainage and quickly convey runoff to a BMP or stream. This runoff control system decreases groundwater recharge, increases runoff volume and changes the timing, frequency and rate of discharge. These changes can cause flooding, water quality degradation, stream ero­ sion and the need to construct end of pipe BMPs. Discharge rates using traditional BMPs may be set only to match the predevelopment peak rate for a specific design year. This approach only controls the rate of runoff allowing significant in­ creases in runoff volume, frequency and duration of runoff from the predevelopment conditions and ---PAGE BREAK--- 3-45 2016 Edition provides the mechanisms for further degradation of receiving waters (Figure LID has often been compared to other inno­ vative practices, such as Conservation Design, which uses similar approaches in reducing the impacts of development, such as reduction of impervious surfaces and conservation of natural features. Although the goals of Conservation Design protect natural flow paths and existing vegetative features, stormwater is not treated directly at the source. Conservation Design protects large areas adjacent to the development site and stormwater is directed to these common areas. Although this approach protects trees and does reduce runoff, there is still potentially a significant amount of connected impervious area and centralized stormwater facilities that may contribute to stream degradation through storm­ water volume, frequency and thermal impacts. Therefore, the hydrologic and hydraulic impacts of this approach on receiving waters may still be significant, although the volume and flows will be less than without the conservation design. The stormwater control measures used in Conser­ vation Design are off-site and therefore not the individual property owner’s responsibility. How­ ever, maintenance is generally provided by the homeowners association and financed through association fees. Figure 1: Changes in Stormwater Hydrology as a Result of Urbanization, Schueler, 1992 Benefits and Limitations The use of LID practices offers both economi­ cal and environmental benefits. LID measures result in less disturbance of the development area, conservation of natural features and can be less cost intensive than traditional stormwater control mechanisms. Cost savings for control mechanisms are not only for construction, but also for long-term maintenance and life cycle cost considerations. For example, an alternative LID stormwater control design for a new 270 unit apartment complex in Aberdeen, NC will save the developer approximately 72% or $175,000 of the stormwater construction costs. On this project, almost all of the subsurface collection systems associated with curb and gutter projects have been eliminated. Strategically located bioreten­ tion areas, compact weir outfalls, depressions, grass channels, wetland swales and specially designed storm water basins are some of the LID techniques used. These design features allow for longer flow paths, reduce the amount of polluted runoff and filter pollutants from stormwater runoff (Blue Land, Water and Infrastructure, 2000). Today many states are facing the issue of urban sprawl, a form of development that consumes green space, promotes auto dependency and widens urban fringes, which puts pressure on environmentally sensitive areas. “Smart growth” strategies are designed to reconfigure develop­ ment in a more eco-efficient and community oriented style. LID addresses many of the envi­ ---PAGE BREAK--- 3-46 2016 Edition ronmental practices that are essential to smart growth strategies including the conservation of open green space. LID does not address the subject of availability of public transportation. LID provides many opportunities to retrofit existing highly urbanized areas with pollution controls, as well as address environmental is­ sues in newly developed areas. LID techniques such as rooftop retention, permeable pavements, bioretention and disconnecting rooftop rain gut­ ter spouts are valuable tools that can be used in urban areas. For example, stormwater flows can easily be directed into rain barrels, cisterns or across vegetated areas in high-density urban areas. Further opportunities exist to implement bioretention systems in parking lots with little or no reduction in parking space. The use of veg­ etated rooftops and permeable pavements are 2 ways to reduce impervious surfaces in highly urbanized areas. LID techniques can be applied to a range of lot sizes. The use of LID, however, may neces­ sitate the use of structural BMPs in conjunction with LID techniques in order to achieve water­ shed objectives. The appropriateness of LID practices is dependent on site conditions, and is not based strictly on spatial limitations. Evalu­ ation of soil permeability, slope and water table depth must be considered in order to effectively use LID practices. Another obstacle is that many communities have development rules that may restrict innovative practices that would reduce impervious cover. These “rules” refer to a mix of subdivision codes, zoning regulations, parking and street standards and other local ordinances that determine how development happens (Center for Watershed Protection, 1998). These rules are responsible for wide streets, expan­ sive parking lots and large-lot subdivisions that reduce open space and natural features. These obstacles are often difficult to overcome. Additionally, community perception of LID may prevent its implementation. Many homeowners want large-lots and wide streets and view reduc­ tion of these features as undesirable and even unsafe. Furthermore, many people believe that without conventional controls, such as curbs and gutters and end of pipe BMPs, they will be required to contend with basement flooding and subsurface structural damage. Low Impact Development Practices LID measures provide a means to address both pollutant removal and the protection of pre­ development hydrological functions. Some basic LID principles include conservation of natural features, minimization of impervious surfaces, hydraulic disconnects, disbursement of runoff and phytoremediation. LID practices such as bio­ retention facilities or rain gardens, grass swales and channels, vegetated rooftops, rain barrels, cisterns, vegetated filter strips and permeable pavements perform both runoff volume reduction and pollutant filtering functions. Bioretention Bioretention systems are designed based on soil types, site conditions and land uses. A bioretention area can be composed of a mix of functional components with each performing dif­ ferent functions in the removal of pollutants and attenuation of stormwater runoff. Grass Swales Grass swales or channels are adaptable to a variety of site conditions, are flexible in design and layout, and are relatively inexpensive (US­ DOT, 1996). Generally open channel systems are most appropriate for smaller drainage areas with mildly sloping topography (Center for Wa­ tershed Protection, 1998). Their application is primarily along residential streets and highways. They function as a mechanism to reduce run­ off velocity and as filtration/infiltration devices. Sedimentation is the primary pollutant removal mechanism, with additional secondary mecha­ nisms of infiltration and absorption. In general grass channels are most effective when the flow depth is minimized and detention time is maxi­ mized. The stability of the channel or overland flow is dependant on the erodibility of the soils in which the channel is constructed (USDOT, 1996). Decreasing the slope or providing dense cover will aid in both stability and pollutant removal ef­ fectiveness. Vegetated Roof Covers Vegetative roof covers or green roofs are an effective means of reducing urban stormwater runoff by reducing the percentage of impervi­ ous surfaces in urban areas. They are especially effective in older urban areas with chronic Com­ bined Sewer Overflow (CSO) problems, due to the high level of imperviousness. The green roof ---PAGE BREAK--- 3-47 2016 Edition is a multilayered constructed material consist­ ing of a vegetative layer, media, a geotextile layer and a drain layer. Vegetated roof covers in urban areas offer a variety of benefits, such as extending the life of roofs, reducing energy costs and conserving valuable land that would otherwise be required for stormwater run­ off controls. Green roofs have been used exten­ sively in Europe to accomplish these objectives. Many opportunities are available to apply this LID measure in older U.S. cities with stormwater infrastructures that have reached their capacities. Permeable Pavements The use of permeable pavements is an ef­ fective means of reducing the percent of imper­ viousness in a drainage basin. More than thirty different studies have documented that stream, lake and wetland quality is reduced sharply when impervious cover in an upstream watershed is greater than 10%. Porous pavements are best suited for low traffic areas, such as parking lots and sidewalks. The most successful installations of alternative pavements are found in coastal areas with sandy soils and flatter slopes (Center for Watershed Protection, 1998). Permeable pavements allow stormwater to infiltrate into underlying soils promoting pollutant treatment and recharge, as opposed to produc­ ing large volumes of rainfall runoff requiring con­ veyance and treatment. Costs for paving blocks and stones range from $2 to whereas asphalt costs $0.50 to $1 (Center for Watershed Protec­ tion, 1998). Other LID Strategies Another strategy to minimize the impacts of development is the implementation of rain gut­ ter disconnects. This practice involves redirect­ ing rooftop runoff conveyed in rain gutters out of storm sewers, and into grass swales, biore­ tention systems and other functional landscape devices. Redirecting runoff from rooftops into functional landscape areas can significantly reduce runoff flow to surface waters and reduce the number of CSO events in urban areas. As long as the stormwater is transported well away from foundations, concerns of structural dam­ age and basement flooding can be alleviated. As an alternative to redirection of stormwater to functional landscape, rain gutter flows can be directed into rain barrels or cisterns for later use in irrigating lawns and gardens. Disconnections of rain gutters can effectively be implemented on existing properties with little change to present site designs. For the complete literature review visit:http:// water.epa.gov/polwaste/green/lidlit.cfm Links for additional information: Center for Watershed Protection -http://www.cwp.org/ City of Atlanta - http://www.atlantawatershed.org/greeninfrastructure/ City of Roswell - http://www.roswellgov.com/index.aspx?NID=1586 Georgia Department of Natural Resources - Coastal Resources Division http://coastalgadnr.org/cm/green/guide http://coastalgadnr.org/cm/green/demo Georgia Institute of Technology, Office of Environmental Stewardship http://www.stewardship.gatech.edu/stormwater.php US Environmental Protection Agency - http://water.epa.gov/polwaste/green/ ---PAGE BREAK--- 3-48 2016 Edition ---PAGE BREAK--- 2016 Edition 4-1 The Erosion and Sedimentation Act of 1975 states that the governing authority of each county and municipality shall adopt a comprehensive ordinance establishing procedures governing land- disturbing activities conducted within their respec­ tive boundaries. The emphasis of the law is truly on implementation of local erosion and sediment control programs. If counties and municipalities have failed to have in effect an ordinance conforming to the provisions of the law, then the State Board of Natural Re­ sources will adopt appropriate rules and regulations governing activities within those areas. PRINCIPLES For any erosion and sediment control pro­ gram to become effective, there are certain principles that should be applied for maximum effectiveness. 1. Erosion and sediment control should become a stated policy of all concerned, including public and private agencies operating in or having jurisdiction within the boundaries of the unit of government. 2. The appropriate certification of per­ sons involved in land development design, review, permitting, construction, monitoring, or inspection of any land-disturbing activity. 3. Competent technical personnel knowledge­ able in local soil and climatic conditions, workable procedures, and inspections are necessary for successful erosion and sedi­ ment control. 4. To be effective, provisions for erosion and sediment control must be made in the plan­ ning stage. Practical combinations of the basic design principles contained in Chapter 2 should be skillfully planned and applied in a timely manner. 5. Research observations and evaluations should be conducted to provide needed information for improvement of the erosion and sediment control program. The Soil and Water Conservation Districts and/or the are required by the Act to semi- annually review the erosion and sediment control programs for effectiveness of the cities and counties that have been certified as a Local Issuing Authority (LIA). PROCESSES An erosion and sediment control program may be subdivided into four basic processes: a. ordinance development and implementation b. plan preparation and review c. inspection and enforcement d. information, education and training ORDINANCE DEVELOPMENT AND IMPLEMENTATION Local officials have a working knowledge of local conditions and problems. It is they who can best implement ordinances that take local needs into account. In the past, the cost of correcting expensive sedi­ ment damages has often been the responsibility of local units of government. Therefore, it is advisable that local governments have direct control over the enforcement of laws pertaining to erosion. The LIA may require the permit applicant to post a bond of up to $3,000.00 per acre of the proposed land- disturbing activity, prior to issuing the permit. If the applicant fails to comply with the conditions of the permit after issuance, the LIA may call the bond and use the proceeds to hire a contractor to stabilize the project site and bring it into compliance. Although the direct responsibility for drafting ordinances falls on local officials, citizen participa­ tion should be encouraged to insure that the final product will reflect their needs and wishes. A model ordinance has been developed by the and the GA EPD for use by officials in municipalities and counties. The model is intended primarily to provide guidelines for control of urban soil erosion and sediment pollution. It is designed to meet state requirements for establishing programs as required in Act 599, as well as compliance with the NPDES Permits. A copy of the model is con­ CHAPTER 4 LOCAL PROGRAMS: PRINCIPLES AND PROCESSES ---PAGE BREAK--- 2016 Edition 4-2 tained in Appendix D of this Manual, and can be found on the and GA EPD websites. Preceeding the body of the model ordinance is a brief explanation of the contents. This explanation is intended to clarify certain sections or phrases contained in the model. Opinions expressed therein are not necessarily requirements to be fulfilled. Local authorities may wish to develop individual ordinances from the wealth of comprehensive ma­ terial available for this, or they may utilize another of the models available. Regardless of the method used, the contents of the model ordinance must be incorporated into the ordinance adopted by the LIA. However, the LIA’s ordinance may exceed the standards, requirements and provisions of the Act and NPDES except for those involving monitoring, reporting, inspections, design standards, turbidity standards, education and training, and project size thresholds with regard to education and training re­ quirements. A review of the final draft by the county or city attorney should be mandatory. An LIA must review, revise, or amend its ordi­ nances within twelve months of any amendment to the E&SC Act. Any land-disturbing activities by an LIA shall be subject to the same requirements of the ordinances of the LIA as are applied to private persons, and the GA EPD shall enforce such requirements upon the LIA. The adoption of an ordinance should be con­ sidered as only the first step toward a sound soil erosion and sedimentation control program. It is essential that sufficient lead time be provided for education of the public and technical training of persons directly involved in its full implementation. PLAN PREPARATION AND REVIEW PROCESS All parties involved in the plan development and review process must realize without excep­ tion that there is more than one approach to minimizing erosion and sedimentation damages. Flexibility without compromising the primary objective must be encouraged to arrive at a com­ mon solution to erosion and sediment control problems on any given site. All available resourc­ es should be explored. Local officials should plan to provide assistance to the developer and his consulting planners and engineers prior to plan submission before plan processing can be effective. Assistance from federal and state agencies having expertise in the field of soil and water conservation should be provided to the developer and his consultant. Developers may benefit by entering into an agreement for assis­ tance through their Soil and Water Conservation District. Technical expertise can then be provided by federal and state agencies. The erosion and sediment control plan should be submitted as early in the planning stage as pos­ sible. The plan itself should embrace all aspects of the requirements of the basic design principles as specified in Chapter 2 of this Manual. In addition, practical combinations of vegetative and struc­ tural conservation practices should be designed in accordance with the minimum requirements of the Standards and Specifications contained in Chapter 6. It is recommended that the plan review process be broken down into the preliminary planning phase and the final design phase to reduce costly engi­ neering fees. Such fees are normally considerably higher than preliminary planning fees. Costs for changes to engineering drawings and specifica­ tions can be prohibitive. An early, or first phase, submission of erosion and sediment control plans will promote general agreement and cooperation and provide for changes with minimum delay to the development process. The responsibility for plan reviews has been delegated by Act 599 to the Soil and Water Con­ servation Districts; however, this does not relieve the county or municipality from a responsibility to assure that plans conform to other local regulations and ordinances. When an LIA has entered into a memorandum of agreement with the district to re­ view erosion and sediment control plans, the LIA has forty-five days to approve or deny the plans. The LIA must state the reasons for denial, and a resubmittal of revised plans must be approved or denied within thirty-five days. For each resubmittal the thirty-five day period restarts. PLAN PROCESSING The following is a recommended procedure for preparation and processing of an erosion and sediment control plan: 1. The owner, developer, or the authorized ---PAGE BREAK--- 2016 Edition 4-3 agent for either the owner or the developer, prepares the erosion and sediment control plan. The plan is prepared in accordance with the minimum requirements and recommen­ dations contained in the Manual for Erosion and Sediment Control. (The Manual should be incorporated by reference in the local ero­ sion and sediment control ordinance.) Plans should be prepared only after consultation with the LIA. 2. The owner, developer, or the authorized agent for the owner or developer, submits the plans to the local permit-issuing authority after completing an application for a permit. (Local officials should determine the number of copies of plans and applications to be submitted by the owner, etc. It is suggested that a minimum of three copies of the plan be submitted.) If an application form has not been developed by the local unit of govern­ ment, a letter of transmittal containing the following information should accompany the plans. a. The name, address and phone number of the applicant. b. The name, address and phone number of the land owner of record. c. The name, address and phone number of the person responsible for carrying out the plan. d. The name, address and phone number of the person preparing the plan. e. The location of the activity including land lot and tax map page numbers. f. Any other information as determined by the local unit of government. The local unit of government may require that a preliminary erosion and sediment control plan be submitted along with a preliminary site plan. The preliminary erosion control plan should not be clut­ tered with detailed erosion and sediment measures but should include the following information: a. Soil boundaries of all major soil series. b. Approximate limits of grading. c. Tentative measures for sediment and ero­ sion control. d. Phasing of development to minimize area and duration of exposure of soils to ero­ sive elements. It is suggested that the issuing authority of the county or municipality delegate the authority for receiving applications and processing permits to the county engineer, director of public works or other qualified individuals knowledgeable in the processing of site development plans. If in the ordinance the responsibilities of the issuing author­ ity are delegated to the constitutional or statutory local planning and zoning commission, then it is suggested that the plans and applications be pro­ cessed by the director of the planning and zoning commission. 3. Two copies of the erosion and sediment control plan shall be forwarded as soon as possible to the local Soil and Water Conser­ vation District, or its delegated authority, for review. In determining the adequacy of the plan, the district officials (Supervisors) will be guided by the requirements and recommen­ dations contained in the local manual. District Supervisors may request the assistance from the erosion and sediment control specialist with the State Soil and Water Conservation Commission, specialists from the District or technical personnel of the Natural Resources Conservation Service. The District Supervi­ sor, after consultation with the district board, will forward the plans and recommendations to the permit-issuing authority of the mu­ nicipality or county. These recommendations should include measures necessary to meet requirements and recommendations outlined in the Manual. A copy of the recommenda­ tions of the district’s technical advisor may be forwarded to the permit-issuing authority. 4. The permit-issuing authority of the local unit of government, after consultation with the governing board, and after a thorough review of the plan for compliance with other resolutions or ordinances, rules and regula­ tions, should then issue or deny a permit. If a plan is not approved, the modifications necessary to permit approval of the plan should be specified in writing. Plan Revisions An approved plan may be revised if inspec­ ---PAGE BREAK--- 2016 Edition 4-4 tions reveal that the erosion and sediment control plan is inadequate in accomplishing the objec­ tives of the law. If so, modifications to correct the deficiencies must have the concurrence of the plan-reviewing authority. Revision may also be required when the person responsible for carrying out the approved plan finds that, because of changed conditions or other rea­ sons, the approved plan cannot be effectively car­ ried out. Minor changes made in the field must be noted on the approved set of plans on site and the site must match the approved plans. Any changes made to the approved plans that have a significant effect on BMP’s with a hydraulic component must be certified by the design professional, and resub­ mitted to the LIA/District for approval. Checklist of Plan Preparation and Review Some of the issues that the plan preparers and plan reviewers need to consider are: 1. Does the proposed plan contain information reflecting actual existing site conditions? 2. Will the roadways, buildings and other permanent features conform to the natural topography of the site? 3. Will the limitations of soils and steep slopes be overcome by sound engineering prac­ tices? 4. Will clearing be limited to only those areas of the site to be developed? 5. Will natural vegetation be retained and provisions made for protection of existing vegetation and for supplemental planting? 6. Will major land clearing and grading opera­ tions be scheduled during seasons of low potential sediment runoff? 7. Will the time of exposure of land clearing and grading be kept to a minimum? 8. Will permanent structures, temporary or per­ manent vegetation or mulch be scheduled for installation as quickly as possible after the land is disturbed? 9. Will all storm water management facilities, temporary or permanent, be designed to safely convey water to a stable outlet? 10. Will sediment basins, sediment barriers, and related devices be planned to filter or trap sediment on the site? Can these structures be easily maintained? 11. Will proposed vegetation be suitable for the intended use? 12. Do potential pollution hazards, including off- site sediment, noise and dust exist? 13. Are proposed permanent facilities subjected to flood or sediment damages? 14. Do subsurface conditions exist that could lead to pollution of ground water or aquifer recharge areas? 15. Is the construction schedule adequate? 16. Will erosion and sediment control measures be in place before extensive grading and clearing begins? 17. Have areas been designated for storage of salvaged topsoil? 18. Can all soil erosion and sediment control measures be adequately maintained? For the plan to meet all requirements of the Act and the NPDES General Permits, the and the GA EPD have created plan review checklists. There is a separate checklist and guidance docu­ ment for each of the permits; Stand Alone Construc­ tion Projects, Infrastructure Construction Projects, and Common Developments. The appropriate checklist must be completed and submitted with the ES&PC Plan for the plan to be reviewed. All checklists and guidance documents can be found on the and the GA EPD websites. INSPECTION AND ENFORCEMENT PROCESS OF LOCAL ISSUING AUTHORITY With regard to the inspection and enforce­ ment process, it should be noted that it is not the purpose of this Manual to support or promulgate specific courses of action by local authorities in these areas. Except as provided by Act 599, the local authorities are expected to exercise autono­ my in determining the extent of any enforcement and inspection processes. The information pro­ vided here, as elsewhere in the Manual, is only ---PAGE BREAK--- 2016 Edition 4-5 in keeping with the responsibility of a publication such as this to offer, for informational purposes, the alternatives available and in no way repre­ sents official opinion or recommendation. These responsibilities begin after the issuance of a permit for a land-disturbing activity. A crucial ele­ ment in any sediment and erosion control program is adequate field inspection for evaluating compli­ ance to the approved erosion and sediment control plan. These inspections might be effectively incor­ porated in other existing local inspection programs. Although Act 599 specifies that the actual re­ sponsibility for inspection is that of the governing authority, on-site inspection may be assigned to a building inspector or another person employed by the Local Issuing Authority. The inspector, whether a soils engineer, civil engineer, soil conservationist, or technician, should have some knowledge in the field of soil and water conservation. To assure that the enforcing agency and the permit applicant are in agreement about the con­ trol procedures to be followed, a pre-construction conference would be desirable. This conference should be held prior to beginning the land disturbing activity. All facets of the proposed work should be discussed at this meeting and anticipated problems reviewed. The need for installing initial sediment storage requirements and perimeter control BMPs prior to actual clearing and grading operations should be emphasized. The individual responsible for carrying out the plan should also be informed of local inspection policies and schedules. The institution of both scheduled and random inspections would be appropriate. The former would be a routine inspection related directly to construction operations and carried out on a rigid schedule. Random or impromptu site inspections would assure continuing compliance and the proper maintenance of erosion and sediment control mea­ sures. The LIA should inspect each project site for compliance at least once every seven calendar days and within 24 hours of each significant rainfall event. The implementation of a record keeping system would insure coordination of the inspection process with other departments and local agencies. The record system should contain a detailed filing sys­ tem for all land-disturbing activities. This file should contain a record including the date of each inspec­ tion, the date land-disturbing activities commenced, and pertinent comments concerning compliance or noncompliance with the erosion and sediment control plan. In cases of noncompliance, the report should contain statements of the conservation measures needed for compliance and the recom­ mended time in which such measures should be installed. Inspection reports should be immediately forwarded to the Local Issuing Authority. In the event that inspections indicate a violation exists, some type of system for notifying the violator would probably be necessary. An effective system often utilized by authorities involves a written “No­ tice to Comply.” If proper action is not taken within five days, the Local Issuing Authority shall issue a stop work order requiring all land-disturbing activi­ ties be stopped until corrective action and mitigation have been taken. The county engineer, building inspector, etc., would represent the issuing authority in handling complaints about missing or ineffective erosion control measures. When it is determined that ineffective erosion control measures are being followed, but those measures comply with the approved erosion control plan, the city engineer, building inspector, etc., should notify the local Soil and Water Conservation District. Checklist of Site Inspection The process of inspecting construction opera­ tions requires knowledge of the basic principles and control measures in Chapter 2. A thorough understanding of the erosion and sediment control plan is absolutely essential. The follow­ ing checklist is supplied to assist the inspector in fulfilling his responsibilities. 1. Are all erosion and sediment control mea­ sures in place, adequate and properly con­ structed? 2. Have clearing operations been confined within the limits as shown on the plan? 3. Is vegetation outside of the clearing area protected? Supplemented? 4. Is sediment being transported from the site onto public right-of-way by vehicular traffic? 5. Are erosion problems present in the vicin­ ity of temporary or permanent storm water management facilities? ---PAGE BREAK--- 2016 Edition 4-6 6. Are sediment basins, sediment barriers and related devices effective in retaining sedi­ ment on the site? 7. Is appropriate vegetation being established as needed on the specified area? 8. Is work progressing in accordance with the proposed schedule? 9. Is the contractor following the plan and con­ struction sequence? 10. Have temporary stream channel crossings been installed and maintained? 11. Are embankment slopes and permanent structures installed in areas subject to flood or sediment damage? 12. Has topsoil been salvaged and stored in the area designated by the plans? 13. Do severe fire hazards exist that would result in brush or grass fires? 14. Are all erosion and sediment control mea­ sures properly maintained? 15. Is excessive sediment leaving the site for any reason? 16. Have all buffers adjacent to “state waters” been honored? To comply with the inspection and monitoring re­ quirements of the NPDES permits sample inspec­ tion forms can be found on the GA EPD and the websites. The NPDES General Permits - Stormwater Discharges from Construc­ tion Activities Forms include the following forms: 1. Daily Inspections 2. Daily Rainfall Log 3. Site Inspection Report 4. Inspection Summary 5. Weekly Inspection Report 6. Inspection Report 7. Storm Water Discharge Data 8. Storm Water Monitoring Records ---PAGE BREAK--- 2016 Edition 4-7 Enforcement, Penalties, and Incentives For each proposed land-disturbing activity, a decision should be made on precautions insuring that conservation measures are installed. These precautions may include a cash bond, cash es­ crow, letter of credit, or any combination thereof. The purpose is to insure that the planned conser­ vation measures are installed at the applicant’s expense if he fails to do it within the specified time. If a cash incentive is used, it should be required prior to commencing the land disturbing activity. In the event that the requirements of the erosion and sediment control plans are not being fulfilled, one alternative the local units of government may consider is withholding future permits such as addi­ tional grading, building, etc., involving the particular land-disturbing site. Local authorities may consider assessing fees for erosion and sediment control plan processing. The cost of inspection services could be recouped, if desired, by levying permit fees. INFORMATION,EDUCATION AND TRAINING PROCESS One of the most important processes in any erosion and sediment control program is an ef­ fective information and education effort. A local program must have the acceptance and the sup­ port of those persons most affected... the devel­ opers, engineers, planners, and architects, as well as the general public. Without their support, effective sediment and erosion control will not take place. It is very important that the “conser­ vation pays” ethic be adopted by these groups. Each municipality and county must formulate plans for an information/education program. Con­ sideration should be given to: 1. Informing the developer and others affected by the requirements of the local program and of the assistance which will be made avail­ able to them. 2. Training seminars, conferences and edu­ cational material for the developer, his consultants, contractors and other support personnel of the developers. 3. Training seminars for the local government personnel authorized to perform the func­ tions of inspections and enforcement and administrative duties within the local erosion and sediment control program. An initial training program for new employees, or personnel such as building inspectors who will have an added duty of inspection for erosion control, is mandatory. Annual refresher courses or training programs should be planned. Assistance in planning and conducting local training programs may be obtained through the Soil and Water Conservation Districts. ---PAGE BREAK--- 2016 Edition 5-1 ASSISTANCE Act 599 emphasizes local erosion and sedi­ mentation control programs. Policies governing permit issuance, inspection and enforcement may therefore vary between each municipality or county. The individual contemplating a land- disturbing activity should contact the governing authority of the county or municipality having jurisdiction over the proposed land change. Con­ tacts should be made during the earliest phases of planning to avoid costly changes or delays. Act 599 specifies that the plan review process will be accomplished by the local Soil and Water Conservation District or its delegated authority. To insure that the erosion and sediment control plan will conform to local requirements, the developers should contact a District Supervisor in the county in which the land-disturbing activity will take place early in the planning stage. RESOURCE INFORMATION A wealth of resource data exists in various agencies which will assist in planning for land- disturbing activities and in the preparation of ero­ sion and sediment control plans. The agencies and websites listed below will provide relevant information. The following pages also provide websites for the agencies’ local offices through­ out the state. Please visit their websites for the most up-to-date contact information. Soils Information USDA Natural Resources Conservation Service (NRCS), Soils http://www.nrcs.usda.gov/wps/portal/nrcs/site/ soils/home/ USDA NRCS, Georgia http://www.nrcs.usda.gov/wps/portal/nrcs/site/ga/ home/ Georgia Soil and Water Conservation Commission CHAPTER 5 SOURCES OF ASSISTANCE AND RESOURCE INFORMATION Topographic and Geologic Information United States Geological Survey (USGS) http://www.usgs.gov/ USGS South Atlantic Water Science Center, Georgia http://ga.water.usgs.gov/ Non-Point Source Pollution Control Georgia Department of Natural Resources (DNR) Environmental Protection Division (EPD) Watershed Protection Branch (WPB) Non-Point Source Pollution Control Program http://epd.georgia.gov/watershed-protection- branch Fisheries Management Georgia DNR Wildlife Resources Division Fisheries Management Section http://www.georgiawildlife.com/fishing/fisheries- management Stream Flow Information USGS National Streamflow Information Program http://water.usgs.gov/nsip/ Flood Hazard, Wetlands and 404 Permit Information U.S. Army Corps of Engineers (USACE) http://www.usace.army.mil/ USACE, Savannah District http://www.sas.usace.army.mil/Missions/Regula­ tory/Permitting.aspx Georgia DNR, EPD, WPB Floodplain Management http://epd.georgia.gov/floodplain-management USDA NRCS http://www.nrcs.usda.gov/wps/portal/nrcs/main/ national/programs/landscape/wfpo/ http://www.nrcs.usda.gov/wps/portal/nrcs/main/ national/water/wetlands/ Agriculture Information USDA NRCS http://www.nrcs.usda.gov/wps/portal/nrcs/site/ national/home/ Forestry Information Georgia Forestry Commission http://www.gatrees.org/ ---PAGE BREAK--- 2016 Edition 5-2 ^ ^ ^ ^ ^ Ware Burke Clinch Hall Early Laurens Worth Lee Floyd Wayne Bulloch Charlton Coffee Tift Fulton Long Screven Decatur Harris Liberty Emanuel Troup Irwin Carroll Dodge Bryan Grady Telfair Colquitt Wilkes Polk Brooks Camden Dooly Tattnall Appling Sumter Thomas Mitchell Bartow Jones Talbot Gilmer Walker Cobb Elbert Berrien Taylor Echols Stewart Hart Macon Baker Coweta Washington Wilcox Jefferson Fannin Rabun Lowndes Bibb Union Jasper Terrell Hancock Brantley Henry Greene Pierce Crisp Marion Miller Monroe Twiggs Upson Pike Murray Heard Gwinnett Clay Chatham Gordon Effingham Walton Wilkinson Toombs Putnam Morgan Jenkins Meriwether Houston Randolph Bacon Cherokee Cook Turner McIntosh White Jackson Atkinson Oglethorpe Warren Banks Butts DeKalb Newton Lincoln Paulding Johnson Wheeler Crawford Pulaski Jeff Davis Baldwin Calhoun Whitfield Madison Lumpkin Franklin Ben Hill Dade Richmond Columbia Dougherty Lanier Candler Haralson Chattooga Evans Pickens Lamar Seminole Towns Fayette Dawson Bleckley Schley Treutlen Douglas Peach Barrow Spalding Muscogee Taliaferro Catoosa Stephens Clarke McDuffie Webster Habersham Oconee Montgomery Quitman Clayton Chattahoochee Glascock Rockdale Chatham McIntosh Camden Georgia Soil and Water Conservation Commission Conservation Regions Legend Region 1 Region 2 Region 3 Region 4 Region 5 ^ Regional Offices 8 0 30 60 15 Miles Region I Calhoun, GA http://gaswcc.georgia.gov/ region-i Region II Athens, GA region-ii-conservation-district Region III Statesboro, GA region-iii Region IV Milledgeville, GA http://gaswcc.georgia.gov/ region-iv Region V Dawson, GA http://gaswcc.georgia.gov/ region-v http://gaswcc.georgia.gov/soil-water-conservation-districts ---PAGE BREAK--- 5-3 2016 Edition Satilla River Flint River Alapaha Piedmont Coosa River Altamaha Central Georgia Broad River Brier Creek Towaliga Ocmulgee River Ogeechee River Middle South Georgia Coastal Georgia West Georgia Ohoopee River Pine Mountain Lower Chattahoochee River Limestone Valley Roosevelt Blue Ridge Mountain Oconee River Upper Chattahoochee River Fulton County Hall County Upper Ocmulgee River Gwinnett County Cobb County Henry County Walton County Warren County DeKalb County Columbia County Lincoln County McDufie County Lamar County Stephens County Catoosa County Clayton County Rockdale County Georgia Soil and Water Conservation Commission Conservation Districts with their corresponding Regions 8 0 50 100 25 Miles 1 2 3 4 5 Legend Conservation Regions County_LayerBasin_Clip SWCC Disticts Alapaha Altamaha Blue Ridge Mountain Brier Creek Broad River Catoosa County Central Georgia Clayton County Coastal Georgia Cobb County Columbia County Coosa River DeKalb County Flint River Fulton County Gwinnett County Hall County Henry County Lamar County Limestone Valley Lincoln County Lower Chattahoochee River McDufie County Middle South Georgia Ocmulgee River Oconee River Ogeechee River Ohoopee River Piedmont Pine Mountain Rockdale County Roosevelt Satilla River Stephens County Towaliga Upper Chattahoochee River Upper Ocmulgee River Walton County Warren County West Georgia ---PAGE BREAK--- 5-4 2016 Edition Georgia Department of Natural Resources Environmental Protection Division http://epd.georgia.gov Coastal District Brunswick, GA East Central District Augusta, GA Mountain District Atlanta, GA Cartersville, GA Northeast District Athens, GA Southwest District Albany, GA West Central District Macon, GA http://epd.georgia.gov/district-office-locations ---PAGE BREAK--- 5-5 2016 Edition Region 1 Gainesville, GA http://www.georgiawildlife. com/node/792 Region 2 Fort Valley, GA http://www.georgiawildlife.com/ Contact/FisheriesRegion2 Region 3 Albany, GA http://www.georgiawildlife.com/ Contact/FisheriesRegion3 Region 4 Waycross, GA http://www.georgiawildlife.com/ Contact/FisheriesRegion4 Region 5 Richmond Hill, GA http://www.georgiawildlife.com/ Contact/FisheriesRegion5 Georgia Department of Natural Resources Wildlife Resource Division Fisheries Management Section www.georgiawildlife.com http://www.georgiawildlife.com/fishing/fisheries-management ---PAGE BREAK--- 5-6 2016 Edition Georgia Department of Transporation District Offices www.dot.ga.gov District One Gainesville, GA District Two Tennille, GA District Three Thomaston, GA District Four Tifton, GA District Five Jesup, GA District Six Cartersville, GA District Seven Chamblee, GA http://www.dot.ga.gov/AboutGDOT/Districts ---PAGE BREAK--- 5-7 2016 Edition Georgia Forestry Commission Water Quality Districts Coosa District -1 Gainesville, GA Rome, GA Flint District - 2 Camilla, GA Americus, GA Satilla District - 5 Waycross, GA Ogeechee District - 6 Helena, GA Statesboro, GA www.gfc.state.ga.us http://www.gfc.state.ga.us/about-us/contact-us/district-offices/index.cfm Oconnee District -3 Milledgeville, GA Washington, GA Chattahoochee District- 4 Newnan, GA ---PAGE BREAK--- 5-8 2016 Edition United States Army Corps of Engineers Georgia Area Sections South Atlantic Division Atlanta, GA http://www.sad.usace.army.mil/ Savannah District, Regulatory Division Savannah, GA http://www.sas.usace.army.mil/ Savannah, GA http://www.sas.usace.army.mil/Mis­ sions/Regulatory/Contacts.aspx Morrow, GA http://www.sas.usace.army.mil/Mis­ sions/Regulatory/Contacts.aspx United States Army Corps of Engineers South Atlantic Division Georgia ---PAGE BREAK--- 5-9 2016 Edition Georgia Natural Resource Conservation Service Area Offices Area 1 Griffin, Georgia Area 2 Athens, Georgia Area 3 Americus, Georgia Area 4 Waycross, Georgia http://www.nrcs.usda.gov/wps/portal/nrcs/main/ga/contact/state/ Area 1 Area 2 Area 3 Area 4 ---PAGE BREAK--- 6-1 2016 Edition CHAPTER 6 BMP STANDARDS AND SPECIFICATIONS FOR GENERAL LAND-DISTURBING ACTIVITIES This chapter contains standards and specifica­ tions for planning, design and installation of erosion and sediment control measures. They are intended to provide minimum criteria for use at the state and local level. The many variations in climate, soils, topography, physical features and planned land use may require modifications at the local level. Local officials will assure that standards and specifica­ tions are implemented in harmony with existing ordinances, rules and regulations. Variations of these standards have been in use since late the 1930’s, when Soil and Water Con­ servation Districts were first established. Continu­ ing progress through experience and research will require periodic updating. The construction specifications contained herein are not intended to be complete. Detailed construction specifications should be prepared for each land-disturbing activity. Information has been included on geotextiles based on the American Association of State High­ way Transportation Officials (AASHTO). Informa­ tion on Forestry Best Management Practices can be found in the Georgia Forestry Commission’s publication entitled Georgia’s Best Management Practices for Forestry. Erosion control is of primary importance during land-disturbing activities, but sediment storage must be available on the site. Temporary sedi­ ment basins and retrofitted detention ponds most commonly achieve the required 67 cubic yards per acre of disturbed area of storage. Some situations may call for the use of practices other than those mentioned above. Appropriate sediment storage and perimeter control BMPs must be installed on the site PRIOR to any land-disturbing activities. It is imperative that creative engineering practices are used to ensure that erosion and sediment control BMP’s are appropriate for the situation and activity. Linear projects pose special treatment concerning erosion and sediment control. Shall or Will, Should, and May are used in these specifications with the following definitions: Shall or Will - A mandatory condition. When certain requirements are described with the “shall” or “will” stipulations, it is mandatory that the require­ ments be met. Should - An advisory condition. Considered to be recommended but not mandatory. May - A permissive condition. No requirement is intended. Section I contains standards providing general instructions for the preparation of erosion and sediment control plans for land-disturbing activities. Section II contains standards and specifications for vegetative type measures for general land- disturbing activities. Section III contains standards for structural practices and provides instructions for the prepa­ ration of erosion and sediment control plans for land-disturbing activities. Section IV contains tables for design of veg­ etated diversion, waterway or stormwater convey­ ance practices. Waters of the United States and Erosion and Sediment Control Wetlands are defined as areas that are inundated by surface or ground water for a long enough period of time that the area supports the growth of vegetation that can perpetuate in satu­ rated soil. Wetlands are a valuable resource, and it is imperative that these areas are protected from damage caused by adjacent erosion and subsequent sedimentation. While state law does not necessarily require buffers adjacent to wet­ lands, these areas are still considered valuable, and all efforts must be made to protect these areas during land disturbing activities. Obviously, the best and most effective method for protect­ ing wetlands is maintaining a buffer between any land-disturbing activity and the wetland. If this is not possible, standard erosion and sediment control devices can be utilized to protect these areas. As always, it is imperative that these de­ vices be designed, installed, and properly main­ tained. ---PAGE BREAK--- 6-2 2016 Edition The Georgia Erosion and Sedimentation (E&S) Act requires that land-disturbing activities in Geor­ gia are protected from erosion and subsequent sedimentation up to and including a 25-year storm. Few realize that activities that impact Waters of the United States can mean stricter Federal require­ ments for erosion and sediment control. Waters of the United States are navigable waters as well as adjacent wetlands and tributaries to navigable waters. Discharge of dredged or fill material into Waters of the United States is regulated by the United States Army Corps of Engineers under Sec­ tion 404 of the Clean Water Act (33 U.S.C. 1344). While State Law requires erosion and sediment control protection for a 25-year storm, Federal Law requires that adequate erosion, sediment and pollution control must be implemented during land- disturbing activities where a section 404 permit (usually known as a wetland permit) is required. Few realize that minor activities of filling and dredging, while not requiring U.S. Army Corps of Engineers notification, still must meet the Federal requirement of “adequate erosion and sediment control” as if a permit had been issued. According to Federal Law, “adequate equates to “no failures tolerated.” In short, when filling or dredging activity impacts any Waters of the United States, adequate erosion control must occur at the site. Therefore, during land-disturbing activities regulated by the state, erosion and sediment control regulations fall under stricter Federal guidelines as well as the standard State guidelines if Waters of the United States are impacted. To get more information concerning discharge of dredged or fill material into Waters of the United States, permitting for these activities, and stipula­ tions for permitting please visit the website of the United States Army Corps of Engineers, Savannah District, Regulatory branch, http://www.sas.usace. army.mil. ---PAGE BREAK--- 6-3 2016 Edition SECTION I: LAND-DISTURBING ACTIVITY PLAN LAND-DISTURBING SECTION II: VEGETATIVE MEASURES BUFFER COASTAL DUNE DISTURBED AREA STABILIZATION (WITH MULCHING DISTURBED AREA STABILIZATION (WITH TEMPORARY DISTURBED AREA STABILIZATION (WITH PERMANENT VEGETATION).................6-35 DISTURBED AREA STABILIZATION (WITH DUST CONTROL ON DISTURBED FLOCCULANTS AND STREAMBANK STABILIZATION (USING PERMANENT SLOPE SECTION III: STRUCTURAL PRACTICES CHANNEL CONSTRUCTION STANDARDS AND SPECIFICATIONS Page Bf Du Cs Ss Ds1 Ds4 Ds3 Fl-Co Sb Tac Ds2 Cd Ch Co ---PAGE BREAK--- 6-4 2016 Edition Ga Gr Rd Lv Re Rt Sd1 Sd2 Dn1 Di Fr Dn2 Dc Cr CONSTRUCTION ROAD STREAM DIVERSION TEMPORARY DOWNDRAIN PERMANENT DOWNDRAIN FILTER GRADE STABILIZATION LEVEL ROCK FILTER RETAINING SEDIMENT INLET SEDIMENT TEMPORARY SEDIMENT TEMPORARY SEDIMENT FLOATING SURFACE SEEP 6-197 TEMPORARY STREAM Sk Sd3 Sd4 SpB Sr ---PAGE BREAK--- 6-5 2016 Edition STORM DRAIN OUTLET SURFACE TURBIDITY TREE VEGETATED WATERWAY OR STORMWATER CONVEYANCE SECTION IV: TABLES FOR DESIGN OF VEGETATED DIVERSION, WATERWAY OR STORMWATER CONVEYENCE PRACTICES TABLE 6-39.1 TABLE 6-39.2 TABLE 6-39.3 TABLE 6-39.4 Su Wt Tc St Tr Tp ---PAGE BREAK--- 6-6 2016 Edition ---PAGE BREAK--- 6-7 2016 Edition SECTION I: LAND-DISTURBING ACTIVITY PLAN ---PAGE BREAK--- 6-8 2016 Edition ---PAGE BREAK--- 6-9 2016 Edition DEFINITION A plan that has been properly designed for the control of erosion, sedimentation and pollution resulting from a land-disturbing activity. PURPOSE The proper design of a detailed plan that is in compliance with the Georgia E&S Act, and/or all requirements of the NPDES Permits for construc­ tion activities. CONDITION An erosion, sediment and pollution control (ES&PC) plan is required for any land-disturbing activity that is not exempt in O.C.G.A § 12-7-17. Compliance with the NPDES Permits is required for all land-disturbing activities that result in a disturbance equal to or greater than one acre, and all land-disturbing activities that result in less than one acre disturbed when the project is part of a larger common plan of development. Many land-disturbing activities will require compliance with both the Act and NPDES, some will require compliance with the Act but are ex­ empt from NPDES, some may be exempt from the Act but require compliance with NPDES, and others may be exempt from both the Act and NP­ DES. The certified design professional preparing the ES&PC Plan should be familiar with all the appropriate requirements. PLANNING CRITERIA The ES&PC Plan shall be designed based upon adequate surveys and resource data, and a site visit by the design professional. Best Man­ agement Practices (BMPs) shall be designed in accordance with the applicable standards pro­ vided within this Chapter. Practical combinations of the following principles shall be utilized, as a minimum, in planning for any land-disturbing activity. 1.Fit the Activity to the Topography and Soils. Detailed planning should be employed to as­ sure that roadways, buildings and other perma­ nent features of the activity conform to the natu­ ral characteristics of the site. Large graded areas should be located on the most level portion of the site. Areas subject to flooding should be avoided. Areas of steep slopes, erodible soils and soils with severe limitations for the intended uses should not be utilized without overcoming the limitations through sound engineering practices. Erosion control, development and maintenance costs can be minimized if a site is selected for a specific activity. 2.The Disturbed Area and the Duration of Exposure to Erosion Elements Should Be Minimized. Clearing of natural vegetation should be lim­ ited to only those areas of the site to be devel­ oped at a given time. Natural vegetation should be retained, protected and supplemented with construction scheduling employed to limit the du­ ration of soil exposure. Major land clearing and grading operations should be scheduled during seasons of low potential runoff. 3.Stabilize Disturbed Areas Immediately. Permanent structures, temporary or perma­ nent vegetation, and mulch, or a combination of these measures, should be employed as quickly as possible after the land is disturbed. Temporary vegetation and mulches can be most effective on areas where it is not practical to establish permanent vegetation. These temporary mea­ sures should be employed immediately after rough grading is completed if a delay is antici­ pated in obtaining finished grade. The finished slope of a cut or fill should be stable and ease of maintenance considered in the design. Stabilize all roadways, parking areas, and paved areas with the gravel subbase, temporary vegeta­ tion or mulch. Mulch, temporary vegetation, or permanent vegetation shall be completed on all exposed areas within 14 days after disturbance. Mulch and/or temporary grassing may be used up to six months; permanent vegetation shall be planted if the area is to be left undisturbed for greater than six months. 4.Retain or Accommodate Runoff. Runoff from the development should be safely conveyed to a stable outlet using storm drains, diversions, stable waterways or similar conser­ vation measures. Consideration should also be given to the installation of storm water retention structures to prevent flooding and damage to facilities resulting from increased runoff from the site. Temporary or permanent facilities for conveyance of storm water should LAND-DISTURBING ACTIVITY PLAN ---PAGE BREAK--- 6-10 2016 Edition be designed to withstand the velocities of pro­ jected peak discharges. These facilities should be operational as soon as possible after the start of construction, and if possible before the distur­ bance of the surrounding areas. 5.Retain Sediment. Appropriate sediment storage providing 67 cubic yards of storage per acre drained for each common drainage location shall be provided until final stabilization of the site. The appropriate initial BMPs must be installed on the site PRIOR to any land-disturbing activities. 6.Do Not Encroach Upon Watercourses. Permanent buildings should not be subjected to flooding, sediment damages or erosion haz­ ards. Earth fills should not be constructed in flood-prone areas so as to adversely obstruct water flows or increase velocity of water flows. When necessary to span a flood prone area or watercourse, bridge or culvert openings should be sized to permit passage of peak discharges without causing undue restric­ tions in water flows or without creating excessive velocities. Uses of flood prone ar­ eas should be limited to activities that would not suffer excessive damages from flooding, scour, and sediment damages. Temporary bridges or culverts should be employed when construction equipment is required to cross natural or con­ structed channels. PLAN REQUIREMENTS The ES&PC Plan shall be designed by a “Design Professional,” as defined in the NPDES Permits, who must have successfully completed the Level II Introduction to Design Seminar, ap­ proved by the The signature, seal, and level II certification number of the design professional who prepared the plan must be on each sheet of the ES&PC Plan. The provides checklists containing the minimum requirements to be shown on the ES&PC Plans to ensure the plans are in compli­ ance with the E&S Act and the NPDES Permits. The appropriate checklist must be properly com­ pleted and included with the ES&PC Plan when plans are submitted for review. Current check­ lists and guidance documents can be found at ---PAGE BREAK--- 6-11 2016 Edition SECTION II: VEGETATIVE MEASURES ---PAGE BREAK--- 6-12 2016 Edition ---PAGE BREAK--- 6-13 2016 Edition Vegetative Measures Erosion control should be addressed in the planning stages of all proposed land-disturbing activities. While erosion is difficult to control completely, methods to reduce it are practical, affordable, and cost effective. Erosion control techniques shall be used on all areas exposed for a prolonged period of time, including areas that will be paved or built upon in the future. Various types of vegetative practices are used for erosion control. The time-line for the implementation of various vegetative practices is as follows: Mulch, temporary vegetation, or permanent (perennial) vegetation shall be completed on all exposed areas within 14 days after distur­ bance. Ds1 - Disturbed Area Stabilization (With Mulching Only) Mulching can be used as a sin­ gular erosion control method on areas at rough grade. Mulch can be an option for up to six months provided that the mulch is applied at the appro­ priate depth (depending on type of mulch used), anchored, and has a continuous 90% cover or greater of the soil surface. Maintenance shall be required to maintain appropriate depth, anchorage, and 90% cover. If an area will remain undisturbed for greater than six months, permanent (perennial) vegetation shall be used. Ds2 - Disturbed Area Stabilization (With Tem­ porary Seeding) Temporary vegetation may be employed instead of mulch if the area will remain undisturbed for less than six months. Ds3 - Disturbed Area Stabilization (With Permanent Vegetation) Permanent (perennial) vegetation or sod shall be used immediately on areas at final grade. Permanent (perennial) veg­ etation shall be used on rough graded areas that will be undisturbed for more than six months. Ds4 - Disturbed Area Stabilization (With Sodding) may be used in place of Ds3. “Stabilization” of an area is accomplished when 70 % of the surface area is covered in a uni­ form, vegetative cover (permanent or temporary) or anchored mulch of the appropriate thickness with 90% coverage. “Final stabilization” means that all soil disturbing activities at the site have been completed, and that for unpaved areas and areas not covered by permanent structures and areas located outside the waste disposal limits of a landfill cell that has been certified by the GA EPD for waste disposal, 100% of the soil surface is uniformly covered in permanent vegetation with a density of 70% or greater, or landscaped according to the Plan (uniformly covered with landscaping ma­ terials in planned landscaped areas), or equivalent permanent stabilization measures. Permanent (perennial) vegetation shall consist of: planted trees, shrubs, perennial vines; a crop of perennial vegetation appropriate for the time of year and region; or a crop of annual vegetation and a seeding of target crop perennials appropriate for the region, such that within the growing season a 70% coverage by perennial vegetation shall be achieved. For linear construction projects on land used for agricultural or silvicultural purposes, final sta­ bilization may be accomplished by stabilizing the disturbed land for its agricultural or silvicultural use. For the purposes of this publication, permanent vegetation is used synonymously with perennial vegetation. Perennial vegetation is plant material that lives continuously from year to year although it may have a dormant season when the leaves and possibly the stems “die back” to the ground. No vegetative planting can technically be considered permanent. Annual vegetation is plant material that lives for only one growing season. This type of vegetation is typically used for temporary establish­ ment due to its quick germination. Some perennial vegetation can be used for temporary stabilization. ---PAGE BREAK--- 6-14 2016 Edition ---PAGE BREAK--- 6-15 2016 Edition DEFINITION A strip of undisturbed, original vegetation, enhanced or restored existing vegetation or the re-establishment of vegetation surrounding an area of disturbance or bordering streams, ponds, wetlands, lakes and coastal waters. PURPOSE To provide a buffer zone serving one or more of the following purposes: • Reduce storm runoff velocities • Act as screen for “visual pollution” • Reduce construction noise • Improve aesthetics on the disturbed land • Filtering and infiltrating runoff • Cooling rivers and streams by creating shade provide food and cover for wildlife and aquatic organisms • Flood protection • Protect channel banks from scour and erosion CONDITIONS A natural strip of vegetation should be pre­ served and, if needed, supplemented to form the buffer zone. There are two types of buffer zones. General Buffers A strip of undisturbed, original land surround­ ing the disturbed site. It can be useful not only to filter and infiltrate runoff, but also to act as a screen for “visual pollution” and reduce construc­ tion noise. General buffers may be enhanced to achieve desired goals. Vegetated Stream Buffers Buffers bordering streams are critical due to the invaluable protection of streams from sedimentation. Stream buffers are also useful in cooling rivers and providing food and cover for wildlife. Refer to the minimum requirements in Act 599 (O.C.G.A. 1-7-1, et. seq.) and Chapters 16 and 18 of the NRCS Engineering Field Hand­ book. In most cases, the buffer zone will be incorpo­ rated into the permanent vegetative cover. Refer to specification Ds3 - Disturbed Area Stabilization (With Permanent Vegetation). DESIGN SPECIFICATIONS Important design factors such as slope, hy­ drology, width and structure shall be considered. While Georgia’s Environmental Protection Divi­ sion enforces minimum stream buffer require­ ments, expanding the stream buffer width is always encouraged. If any land-disturbing activ­ ity, including exempt and non-exempt practices, occurs within the GA EPD mandated stream buf­ fers, cut and fills within the buffer shall be stabi­ lized with appropriate matting or blanket. General Buffers A width should be selected to permit the zone to serve the purpose(s) as listed above. Supple­ mental plantings may be used to increase the effectiveness of the buffer zone. Vegetated Stream Buffers The structure of vegetated stream buffers should be considered to determine if the buf­ fer must be enhanced to achieve the necessary goals. The size of the stream as well as the topography of the area must be considered to determine the appropriate width of the vegetated stream buffer. A vegetated stream buffer of 50 feet or greater can protect waters from excess sedimentation. The buffer should be increased 2 feet in width for every 1% slope (measured along a line perpendicular to the stream bank). Surface water pollution can be reduced with a 100 foot or wider vegetative buffer. Buffer Zone Bf ---PAGE BREAK--- 6-16 2016 Edition Figure 6-1.1 - Range of Minimum Width for Meeting Specific Buffer Objectives (Palone and Todd, draft) A general multipurpose riparian buffer consists of three zones. 1. Zone 1 The first 20 feet nearest the stream should consist of trees spaced 6-10 feet apart. 2. Zone 2 The next 10 feet should consist of managed forest. 3. Zone 3 The following 20 feet should be com­ prised of grasses. This general multipurpose design contains trees and shrubs that help to stabilize stream banks and grasses that spread and reduce the flow from adjacent areas as well as increase settling and in­ filtration. See Tables 6-1.1 and 6-1.2 for suggested plant species. If the ideal vegetated buffer width cannot be achieved; narrower buffers can still be used to obtain the goals concerning forest structure and riparian habitat. If this is the case, several design principles should be considered: 1. Sheet flow should be encouraged at the edge of the vegetated stream buffer. 2. The structure of the buffer should consist of under-story and canopy species. 3. The width should be proportional to the watershed area and slope. 4. Native and non-invasive plant species should be used. 5. Density must be considered to determine if the existing buffer must be enhanced to achieve the necessary goals. Vegetation must be dense enough to filter sediment and provide detrital nutrients for aquatic organisms. Streambank stabilization techniques may be required if steep slopes and hydrologic patterns deem it necessary. Refer to specification Sb - Streambank Stabilization (Using Permanent Vegetation). Vegetated stream buffers on steep slopes may need to be wider to effectively filter overland flow. Corridors subject to intense flooding may require additional streambank stabilization measures. PLANTING TECHNIQUES Plantings for buffer re-establishment and enhancement can consist of bare root seedlings, container-grown seedlings, container-grown plants, and balled and burlapped plants. Refer to Tables 6-1.1 and 6-1.2, and Wildlife Plantings in Ds3 - Disturbed Area Stabilization (With Per­ manent Vegetation). Standard permanent ero­ 0 25 50 75 100 150 200 250 Wildlife Habitat Flood Control Streambanks Stabilization and Aquatic Food Web Sediment Control Nutrient Removal Water Temperature Moderation Buffer Width in Feet ---PAGE BREAK--- 6-17 2016 Edition sion control grasses and legumes may be used in denuded areas for quick stabilization. Refer to specification Ds3 - Disturbed Area Stabilization (With Permanent Vegetation). Availability, cost, associated risk, equipment, planting procedures, and planting density must be considered when choosing planting types. Soil preparation and maintenance are essential for the establishment of planted vegetation. Soil fertility, weed control, herbaceous cover, as well as additional associated products may be required. OPERATIONS AND MAINTENANCE Areas closest to the stream should be main­ tained with minimal impact. Watering During periods of drought as well as during the initial year, watering may be necessary in all buffer areas planted for enhancement. Weed Control Weeds can be removed by hand or with careful spraying. Replanting It is imperative that the structure of the vegetated stream buffer be maintained. If the buffer has been planted, it is suggested that the area be monitored to determine if plant material must be replaced. See Tables 6-1.1 and 6-1.2 for suggested plant species. Provisions for the protection of new plantings from destruction or damage from beavers shall be incorporated into the plan. Fertilizer If appropriate vegetation is chosen, it is un­ likely that fertilizer will be necessary. Local Contacts: USDA Natural Resources Conservation Service Georgia Forestry Commission ---PAGE BREAK--- 6-18 2016 Edition Legend Tolerance to Flooding, Drought, Deposition, and Shade : Region: H = High C = Coastal M = Medium P = Piedmont L = Low M =Mountain Rooting of all species will be improved if nearby vegetation is pruned to increase sunlight penetration. Whenever possible, harvest hardwood cuttings as close to the repair site as possible. Many of the above grow naturally along streams, in adjacent wetlands, along sewer and power line easements, and where streams enter lakes and along lake shores. Willows generally grow profusely in stormwater detention ponds in urban areas. ALWAYS OBTAIN PERMISSION FROM THE PROPERTY OWNER BEFORE HARVESTING PLANTS! Adapted from the USDA/NRCS Engineering Field Handbook, Chapter 18 Table 6-1.1 - Unrooted Hardwood Cuttings ---PAGE BREAK--- 6-19 2016 Edition Table 6-1.2 - Native Plant Guide NATIVE PLANT GUIDE FOR STREAMBANK PLANTING ROOTED STOCK ---PAGE BREAK--- 6-20 2016 Edition Table 6-1.2 - Native Plant Guide - continued ---PAGE BREAK--- 6-21 2016 Edition Table 6-1.2 - Native Plant Guide - continued Legend Region: M = Mountains P = Piedmont C = Coastal Plain ---PAGE BREAK--- 6-22 2016 Edition Table 6-1.2 - Native Plant Guide - continued Plant List Sources: Brown, Claude L. & Kirkman, Katherine L. 1990. Trees of Georgia and Adjacent States. Foote, Leonard E. & Jones, Samuel Jr. 1989. Native Shrubs and Woody Vines of the Southeast. Georgia Cooperative Extension Service. Native Plants for Georgia Gardens. Gary L. 1988. Native Trees, Shrubs and Vines for Urban & Rural America. USDA Natural Resources Conservation Service. 1973. Seacoast Plants of the Carolinas. USDA Natural Resources Conservation Service, Engineering Field Handbook, Chapter 18, Soil Bioengineering for Upland Slope Protection and Erosion Reduction. ---PAGE BREAK--- 6-23 2016 Edition DEFINITION Planting vegetation on dunes that are denuded, artificially constructed, or renourished. PURPOSE •To stabilize soil on dunes allowing them to become more resistant to wind and waves. •To allow development of dunes in areas where they have been damaged or destroyed. CONDITIONS On bare or sparsely vegetated dunes or areas where dune development is desired. PLANNING CONSIDERATIONS Coastal beaches are subject to regulation from a variety of Federal, State, and local agen­ cies. Permits must be requested and granted by all appropriate jurisdictions before work is per­ formed. Coastal areas are affected by many dynamic systems. Detailed studies are often required to determine the possible effects that may result from dune modifications. Environmental assess­ ments are generally required including public review and comment. Protection of dunes from human and vehicu­ lar traffic is essential if vegetation is to succeed. Crosswalks or crossover structures should be planned to provide beach access. Plant species that are native to coastal areas should be used whenever possible. An irrigation system will be required during the first growing season in order to obtain good survival. Common Commercially Available Plants Marshhay cordgrass (Spartina patens) “Fla­ geo” variety (or native collections) is a perennial grass that occurs on dunes throughout the South Atlantic and Gulf region and in Puerto Rico. It is the dominant plant on dunes composed of bro­ ken shale and coquina rock along the northern Florida coast. The grass is especially tolerant of salt. Stems are slender and grow two to three feet tall. Leaves are rolled inward and resemble rushes. Seed heads are composed of two to several compressed spikes attached at about 90 de­ grees to the culm. Plants spread by means of a network of slender rhizomes. Plantings of vegetative material in early spring are most successful. Bare root or potted planting stock is recommended for large plantings. Stems rooted at the base can be planted at a depth of four to five inches deep. Plants that have devel­ oped rhizomes are preferred for planting stock. Bitter panicum (Panicum amarum) is a peren­ nial grass found on dunes throughout the South Atlantic and Gulf regions. It is most common in South Florida and Texas. Plants grow to an average height of three to four feet tall. Leaves are smooth and bluish green in color. Seed heads are narrow, com­ pressed, and generally are sparsely seeded. Plants spread from a very aggressive, scattered system of rhizomes, but stands are rather open. Bitter panicum produces few viable seed but is easier to transplant than sea oats. They can be propagated from a stem with part of the rhizome attached or from rhizomes that are eight to twelve inches long. Plant rhizomes about four inches deep in early spring. Plants may be propagated by removing all of the stem from robust plants and placing them in the dune at an angle of about 45 degrees. Sev­ Coastal Dune Stabilization (With Vegetation) Cs ---PAGE BREAK--- 6-24 2016 Edition eral nodes should be buried. Spacing should be no more than six feet apart. Coastal Panicgrass (Panicum amarum v. ama­ ralum) is a somewhat dense, upright perennial found on coastal dunes throughout the South Atlantic and Gulf area. It is the domi­ nant plant at many locations in West Florida, Alabama, and Texas. The stems are coarse, straight, stiff, and up to four feet tall. Partially compressed seed heads produce moderate amounts of viable seed each fall. The crowns enlarge slowly from short, al­ most vertical tillers. Plant seed one to three inches deep in the spring and mulch the area. Seedling survival depends on moisture after germination. Clumps of coastal panicgrass can be dug, divided and planted during rainy seasons or when irrigation is available. line, a single line of fence may be constructed at least 140 feet from the mean high tide. Construct short sections of fence (approximately 30 feet long) parallel to the prevailing wind and approximately perpendicular to the original fence. Place these fences opposite the water side and space these fences about 40 feet apart. As sand collects over the fence, additional fence can be constructed over the original fence until the desired height is obtained. Old dunes may be widened by constructing sand fence about 15 feet to the seaward side of the base of the old dune. Vegetation must be established following de­ velopment of dunes, or allowed to develop from existing stands as dunes develop. SPECIFICATIONS Sand Fence Specifications Should use standard commercial 4-foot high snow fence that consists of wooden slats wired together with spaces between the slats. Distance between slats should be approximately equal to the slat width, or generally 1 1/4 inches. Slats should be made from grade A or better spruce. Slats should be woven between five two-wire cables of copper-bearing, galvanized wire. Slats should be dipped in a red oxide, weather re­ sistant stain. The fence must be sound, free of decay, broken wire or missing or broken slats. Fence should be supported by black locust, red cedar, or white cedar posts. Other wood of equal life or strength may be used. Posts should be a minimum of 7 feet with a minimum diameter of three inches. Posts should be spaced no farther than 10 feet apart. Figure 6-2.1 - Sand Fence and Native Plants Sand Fence Use In Building Dunes Sand fence may be used to build sand dunes when sand is available. Costs are usually higher but dune development is faster when compared to vegetation alone and generally less expensive than building dunes with machinery. To form a barrier dune, construct sand fences a minimum of 100 feet from the mean high tide line. Two or more parallel fences spaced from 30 to 40 feet apart are needed. Locate fences as near as possible to a 90 degree angle with the prevailing winds, but as near parallel to the water line as possible. Where winds are generally parallel with the water ---PAGE BREAK--- 6-25 2016 Edition Four wire ties should be used to fasten fence to posts. Weave fence between posts so that ev­ ery other post should be attached on the ocean side of posts. Tie wires should be no smaller than 12-gauge galvanized wire. Posts should be set in holes at least three feet deep. Three or four rows of fence should be used if sufficient land area and sand are available. MAINTENANCE Maintaining Dunes A strong, uniform dune line must be main­ tained to provide maximum protection from wind and water. Blowouts, wash pits, or other natural or man-made damage must be repaired quickly to prevent weakening of the entire system. Blow- outs in a dune system can be repaired by placing sand fence between existing dunes. One or more fences may be required. It is essential to tie the ends of the fence into the existing dune to keep the wind from slipping around the ends. Maintain fences, and erect additional fences if needed, until the eroding area is replenished to the de­ sired height and permanently stabilized. Foot and vehicular traffic must be controlled or prohibited on dunes to maintain vegetation and pre­ vent excessive sand movement. Elevated walks, semi-permanent paved paths, and portable roll-up walkways are satisfactory. Walkways should be curved to reduce wind movement. Both inland and secondary dunes must be protected from traffic. Vegetative Maintenance Plantings are maintained with applications of fertilizer to keep desired density of plants. Annual application of about 50 pounds of nitrogen per acre should be applied. Where vegetation has been destroyed, replanting should be consid­ ered. ---PAGE BREAK--- 6-26 2016 Edition Figure 6-2.2 - Sand Fence Installation Requirements Ground 10' max. spacing level Black Locust, Red or White Cedar or 4 12-gauge galvanized wires 3" minimum 7' min. length 3' min. post diameter similarly durable wood ---PAGE BREAK--- 6-27 2016 Edition DEFINITION Applying plant residues or other suitable materials, produced on the site if possible, to the soil surface. PURPOSE •To reduce runoff and erosion •To conserve moisture •To prevent surface compaction or crusting •To control undesirable vegetation •To modify soil temperature •To increase biological activity in the soil REQUIREMENT FOR REGULATORY COMPLIANCE Mulch or temporary grassing shall be applied to all exposed areas within 14 days of distur­ bance. Mulch can be used as a singular erosion control device for up to six months, but it shall be applied at the appropriate depth, depending on the material used, anchored and have a continu­ ous 90% cover or greater of the soil surface. Maintenance shall be required to maintain appropriate depth and 90% cover. Temporary vegetation may be employed instead of mulch if the area will remain undisturbed for less than six months. If any area will remain undisturbed for greater than six months, permanent vegetative tech­ niques shall be employed. Refer to Ds2 -Dis­ turbed Area Stabilization (With Temporary Seeding), Ds3 - Disturbed Area Stabilization (With Permanent Seeding), and Ds4 - Dis­ turbed Area Stabilization (With Sodding). SPECIFICATIONS Mulching Without Seeding This standard applies to graded or cleared areas where seedings may not have a suitable growing season to produce an erosion retardant cover, but can be stabilized with a mulch cover. Site Preparation 1. Grade to permit the use of equipment for applying and anchoring mulch. 2. Install needed erosion control measures as required such as dikes, diversions, berms, terraces and sediment barriers. 3. Loosen compact soil to a minimum depth of 3 inches. Mulching Materials Select one of the following materials and apply at the depth indicated: 1. Dry straw or hay shall be applied at a depth of 2 to 4 inches providing complete soil cover­ age. One advantage of this material is easy application. 2. Wood waste (chips, sawdust or bark) shall be applied at a depth of 2 to 3 inches. Organic material from the clearing stage of develop­ ment should remain on site, be chipped, and applied as mulch. This method of mulching can greatly reduce erosion control costs. 3. Polyethylene film shall be secured over banks or stockpiled soil material for tem­ porary protection. This material can be sal­ vaged and re-used. Applying Mulch When mulch is used without seeding, mulch shall be applied to provide full coverage of the exposed area. 1. Dry straw or hay mulch and wood chips shall be applied uniformly by hand or by mechanical equipment. Disturbed Area Stabilization (With Mulching Only) Ds1 ---PAGE BREAK--- 6-28 2016 Edition 2. If the area will eventually be covered with perennial vegetation, 20-30 pounds of ni­ trogen per acre in addition to the normal amount shall be applied to offset the uptake of nitrogen caused by the decomposition of the organic mulches. 3. Apply polyethylene film on exposed areas. Anchoring Mulch 1. Straw or hay mulch can be pressed into the soil with a disk harrow with the disk set straight or with a special “packer disk.” Disks may be smooth or serrated and should be 20 inches or more in diameter and 8 to 12 inches apart. The edges of the disk should be dull enough not to cut the mulch but to press it into the soil leaving much of it in an erect position. Straw or hay mulch shall be anchored immediately after application. Straw or hay mulch spread with special blower-type equipment may be anchored. Tackifers, binders and hydraulic mulch with tackifier specifically desgined for tacking straw can be substituted for emulsified asphalt. Please refer to specification Tac- Tackifers. Plastic mesh or netting with mesh no larger than one inch by one inch shall be installed according to manufacturer’s speci­ fications. 2. Netting of the appropriate size shall be used to anchor wood waste. Openings of the net­ ting shall not be larger than the average size of the wood waste chips. 3. Polyethylene film shall be anchor trenched at the top as well as incrementally as necessary. ---PAGE BREAK--- 6-29 2016 Edition DEFINITION The establishment of temporary vegetative cover with fast growing seedings for seasonal protection on disturbed or denuded areas. PURPOSE •To reduce runoff and sediment damage of down stream resources •To protect the soil surface from erosion • To improve wildlife habitat • To improve aesthetics •To improve tilth, infiltration and aeration as well as organic matter for permanent plantings REQUIREMENT FOR REGULATORY COMPLIANCE Mulch or temporary grassing shall be applied to all exposed areas within 14 days of distur­ bance. Temporary grassing, instead of mulch, can be applied to rough graded areas that will be exposed for less than six months. If an area is expected to be undisturbed for longer than six months, permanent perennial vegetation shall be used. If optimum planting conditions for tempo­ rary grassing is lacking, mulch can be used as a singular erosion control device for up to six months but it shall be applied at the appropriate depth, anchored, and have a continuous 90% cover or greater of the soil surface. Refer to specification Ds1-Disturbed Area Stabilization (With Temporary Seeding). CONDITIONS Temporary vegetative measures should be coordinated with permanent measures to assure economical and effective stabilization. Most types of temporary vegetation are ideal to use as companion crops until the permanent vegetation is established. Note: Some species of temporary vegetation are not appropriate for companion crop plantings because of their po­ tential to out-compete the desired species (e.g. annual ryegrass). Contact NRCS or the local SWCD for more information. SPECIFICATIONS Grading and Shaping Excessive water run-off shall be reduced by properly designed and installed erosion control practices such as closed drains, ditches, dikes, diversions, sediment barriers and others. No shaping or grading is required if slopes can be stabilized by hand-seeded vegetation or if hy­ draulic seeding equipment is to be used. Seedbed Preparation When a hydraulic seeder is used, seedbed preparation is not required. When using conven­ tional or hand-seeding, seedbed preparation is not required if the soil material is loose and not sealed by rainfall. When soil has been sealed by rainfall or con­ sists of smooth cut slopes, the soil shall be pitted, trenched or otherwise scarified to provide a place for seed to lodge and germinate. Lime and Fertilizer Agricultural lime is required unless soil tests indicate otherwise. Apply agricultural lime at a rate determined by soil test for pH. Quick acting lime should be incorporated to modify pH during the germination period. Bio stimulants should also be considered when there is less than 3% organic matter in the soil. Graded areas require lime application. Soils must be tested to deter­ mine required amounts of fertilizer and amend­ ments. Fertilizer should be applied before land preparation and incorporated with a disk, ripper, or chisel. On slopes too steep for, or inacces­ sible to equipment, fertilizer shall be hydraulically applied, preferably in the first pass with seed and some hydraulic mulch, then topped with the remaining required application rate. Disturbed Area Stabilization (With Temporary Seeding) Ds2 ---PAGE BREAK--- 6-30 2016 Edition Seeding Select a grass or grass-legume mixture suit­ able to the area and season of the year. Seed shall be applied uniformly by hand, cyclone seeder, drill, culti-packer-seeder, or hydraulic seeder (slurry including seed and fertilizer). Drill or cultipacker seeders should normally place seed one-quarter to one-half inch deep. Appropriate depth of planting is ten times the seed diameter. Soil should be “raked” to cover seed with soil if seeded by hand. See Table 6-4.1 Mulching Temporary vegetation can, in most cases, be established without the use of mulch, provided there is little to no erosion potential. However, the use of mulch can often accelerate and enhance germination and vegetation establishment. Mulch without seeding should be considered for short term protection. Refer to Ds1 - Disturbed Area Stabilization (With Mulching Only). Irrigation During times of drought, water shall be applied at a rate not causing runoff and erosion. The soil shall be thoroughly wetted to a depth that will insure germination of the seed. Subsequent applications should be made when needed. ---PAGE BREAK--- Table 6-4.1 - Temporary Cover or Companion Cover Crops PLANT, PLANTING RATE, AND PLANTING DATE FOR TEMPORARY COVER OR COMPANION CROPS 1 Species Broadcast Rates Resource Area3 Planting Dates by Resource Area Remarks Solid lines indicate optimum dates, dotted lines indicate permissible but marginal dates. Rate Per Acre2 Pure Live Seed (PLS) Per 1000 sqft J F M A M J J A S O N D BARLEY Hordeum vulagre alone 3 bu. (144 lbs) 3.3 lbs M-L 14,000 seed per pound. Winter hardy. Use on productive soils. in mixture 1/2 bu. (24lbs) 0.6 lb P C LESPEDEZA, ANNUAL Lespedeza striata alone 40 lbs 0.9 lb M-L 200,000 seed per pound. May volunteer for sev- eral years. Use inoculant EL. in mixture 10 lbs 0.2 lb P C LOVEGRASS, WEEPING Eragrostis curvula alone 4 lbs 0.1 lb M-L 1,500,000 seed per pound. May last for several years. Mix with Sericea lespedeza. in mixture 2 lbs 0.05 lb P C MILLET, BROWNTOP Panicum fasciculatum alone 40 lbs 0.9 lb M-L 137,000 seed per pound. Quick dense cover. Will provide excessive competion in mixtures if seeded at high rate. in mixture 10 lbs 0.2 lb P C ---PAGE BREAK--- Species Broadcast Rates Resource Area3 Planting Dates by Resource Area Remarks Solid lines indicate optimum dates, dotted lines indicate permissible but marginal dates. Rate Per Acre2 Pure Live Seed (PLS) Per 1000 sqft J F M A M J J A S O N D MILLET, PEARL Pennesetum glaucum alone 50 lbs 1.1 lbs M-L 88,000 seed per pound. Quick dense cover. May reach 5 feet in height. Not recommended for mixtures. P C OATS Avena sativa alone 4 bu. (128 lbs) 2.9 lbs M-L 13,000 seed per pound. Use on productive soils. Not as a winter hardy as rye or barley. in mixture 1 bu. (32 lbs) 0.7 lb P C RYE Secale cereale alone 3 bu. (168 lbs) 3.9 lbs M-L 18,000 seed per pound. Quick cover. Drought tolerant and winter hardy. in mixture 1/2 bu. (28 lbs) 0.6 lb P C RYEGRASS, ANNUAL Lolium temulentum alone 40 lbs 0.9 lb M-L 227,000 seed per pound. Dense cover. Very com- petitive and is not to be used in mixtures. P C SUDANGRASS Sorghum sudanese alone 60 lbs 1.4 lbs M-L 55,000 seed per pound. Good on droughty sites. Not recommended for mixtures. P C ---PAGE BREAK--- Species Broadcast Rates Resource Area3 Planting Dates by Resource Area Remarks Solid lines indicate optimum dates, dotted lines indicate permissible but marginal dates. Rate Per Acre2 Pure Live Seed (PLS) Per 1000 sqft J F M A M J J A S O N D TRITICALE X-Triticosecale alone 3 bu. (144 lbs) 3.3 lbs C Use on lower part of Southern Coastal Plain and in Atlantic Coastal Flatwoods only. in mixture 1/2 bu. (24 lbs) 0.6 lb WHEAT Triticum aestivum alone 3 bu. (180 lbs) 4.1 lbs M-L 15,000 seed per pound. Winter hardy. in mixture 1/2 bu. (30 lbs) 0.7 lb P C 1Temporary cover crops are very competitive and will crowd out perennials if seeded too heavily 2Reduce seeding rates by 50% when drilled. 3M-L represents the Mountain; Blue Ridge; and Ridges and Valleys MLRAs P represents the Southern Piedmont MLRA C represents Southern Coastal Plan; Sand Hills; Black Lands; and Atlantic Coast Flatwoods MLRAs (see Figure 6-4.1, p. 6-40) ---PAGE BREAK--- 6-34 2016 Edition Figure 6-4.1 ---PAGE BREAK--- 6-35 2016 Edition DEFINITION The planting of perennial vegetation such as trees, shrubs, vines, grasses, or legumes on exposed areas for final permanent stabilization. Permanent perennial vegetation shall be used to achieve final stabilization. PURPOSE •To protect the soil surface from erosion •To reduce damage from sediment and runoff to down-stream areas •To improve wildlife habitat and visual resources •To improve aesthetics REQUIREMENT FOR REGULATORY COMPLIANCE This practice shall be applied immediately to rough graded areas that will be undisturbed for longer than six months. This practice or sodding shall be applied immediately to all areas at final grade. Final Stabilization means that all soil disturbing activities at the site have been com­ pleted, and that for unpaved areas and areas not covered by permanent structures and areas located outside the waste disposal limits of a landfill cell that has been certified by the GA EPD for waste disposal, 100% of the soil surface is in permanent vegetation with a density of 70% or greater, or landscaped ac­ cording to the Plan (uniformly covered with land­ scaping materials in planned landscaped areas), or equivalent permanent stabilization measures. Permanent vegetation shall consist of, planted trees, shrubs, perennial vines; or a crop of peren­ nial vegetation appropriate for the region, such that within the growing season a 70% coverage by perennial vegetation shall be achieved. Final stabilization applies to each phase of construc­ tion. For linear construction projects on land used for agricultural or silvicultural purposes, final stabilization may be accomplished by sta­ bilizing the disturbed land for its agricultural or silvicultural use. Until this standard is satisfied and permanent control measures and facilities are operational, interim stabilization measures and temporary erosion and sedimentation control measures shall not be removed. CONDITIONS Permanent perennial vegetation is used to provide a protective cover for exposed areas including cuts, fills, dams, and other denuded areas. PLANNING CONSIDERATIONS 1. Use conventional planting methods where possible. 2. When mixed plantings are done during mar­ ginal planting periods, companion crops shall be used. 3. No-till planting is effective when planting is done following a summer or winter annual cover crop. Sericea lespedeza planted no-till into stands of rye is an excellent procedure. 4. Block sod provides immediate cover. It is especially effective in controlling erosion adjacent to concrete flumes and other struc­ tures. Refer to Specification Ds4-Disturbed Area Stabilization (With Sodding). 5. Irrigation should be used when the soil is dry or when summer plantings are done. 6. Low maintenance plants, as well as natives, should be used to ensure long-lasting ero­ sion control. 7. Mowing should not be performed during the quail nesting season (May to September). 8. Wildlife plantings should be included in critical area plantings. Disturbed Area Stabilization (With Permanent Vegetation) Ds3 ---PAGE BREAK--- 6-36 2016 Edition Wildlife Plantings Commercially available plants beneficial to wildlife species include the following: Mast Bearing Trees Beech, Black Cherry, Blackgum, Chestnut, Chinkapin, Hackberry, Hickory, Honey Locust, Native Oak, Persimmon, Sawtooth Oak and Sweetgum. All trees that produce nuts or fruits are favored by many game species. Hickory provides nuts used mainly by squirrels and bear. Shrubs and Small Trees Bayberry, Bicolor Lespedeza, Crabapple, Dog­ wood, Huckleberry or Native Blueberry, Mountain Laurel, Native Holly, Red Cedar, Red Mulberry, Sumac, Wax Wild Plum and Blackberry. Plant in patches without tall trees to develop stable shrub communities. All produce fruits used by many kinds of wildlife, except for lespedeza that produces seeds used by quail and songbirds. Grasses, Legumes, Vines and Temporary Cover Bahiagrass, Bermudagrass, Grass-Legume mixtures, Partridge Pea, Annual Lespedeza, Or­ chardgrass (for mountains), Browntop Millet (for temporary cover), and Native grapes. Provides herbaceous cover in clearings for a game bird brood-rearing habitat. Appropriate le­ gumes such as vetches, clovers, and lespedezas may be mixed with grass, but they may die out after a few years. CONSTRUCTION SPECIFICATIONS Grading and Shaping Grading and shaping may not be required where hydraulic seeding and fertilizing equip­ ment is to be used. Vertical banks shall be sloped to enable plant establishment. When conventional seeding and fertilizing are to be done, grade and shape where feasible and practical, so that equipment can be used safely and efficiently during seedbed preparation, seed­ ing, mulching and maintenance of the vegetation. Concentrations of water that will cause excessive soil erosion shall be diverted to a safe outlet. Diver­ sions and other treatment practices shall conform with the appropriate standards and specifications. Lime and Fertilizer Rates and Analysis Agricultural lime is required at the rate of one to two tons per acre unless soil tests indicate otherwise. Graded areas require lime application. If lime is applied within six months of planting permanent perennial vegetation, additional lime is not required. Agricultural lime shall be within the specifications of the Georgia Department of Agriculture. Lime spread by conventional equipment shall be “ground limestone.” Ground limestone is calcitic or dolomitic limestone ground so that 90 percent of the material will pass through a 10-mesh sieve, not less than 50 percent will pass through a 50-mesh sieve and not less than 25 percent will pass through a 100-mesh sieve. Fast-acting lime spread by hydraulic seeding equipment should be “finely ground limestone” spanning from the 180 micron size to the 5 micron size. Finely ground limestone is calcitic or dolomitic limestone ground so that 95 percent of the material will pass through a 100-mesh sieve. It is desirable to use dolomitic limestone in the Sand Hills, Southern Coastal Plain and Atlantic Coast Flatwoods MLRAs. (See Figure 6-4.1) Agricultural lime is generally not required where only trees are planted. Initial fertilization, nitrogen, topdressing, and maintenance fertilizer requirements for each spe­ cies or combination of species are listed in Table 6-5.1. Lime and Fertilizer Application When hydraulic seeding equipment is used, the initial fertilizer shall be mixed with seed, innoculant (if needed), and wood cellulose or wood pulp fiber mulch and applied in a slurry. The innoculant, if needed, shall be mixed with the seed prior to being placed into the hydraulic seeder. The slurry mixture will be agitated during application to keep the ingredients thoroughly mixed. The mixture will be spread uniformly over the area within one hour after being placed in the ---PAGE BREAK--- 6-37 2016 Edition hydroseeder. Finely ground limestone can be applied in the mulch slurry or in combination with the top dressing. When conventional planting is to be done, lime and fertilizer shall be applied uniformly in one of the following ways: 1. Apply before land preparation so that it will be mixed with the soil during seedbed prepara­ tion. 2. Mix with the soil used to fill the holes, distrib­ ute in furrows. 3. Broadcast after steep surfaces are scarified, pitted or trenched. 4. A fertilizer pellet shall be placed at root depth in the closing hole beside each pine tree seedling. Plant Selection Refer to Tables 6-4.1, 6-5.2, 6-5.3 and 6-5.4 for approved species. Species not listed shall be approved by the State Resource Conservationist of the Natural Resources Conservation Service before they are used. Plants shall be selected on the basis of species characteristics, site and soil conditions, planned use and maintenance of the area; time of year of planting, method of planting; and the needs and desires of the land user. Some perennial species are easily established and can be planted alone. Examples of these are Common Bermuda, Tall Fescue, and Weeping Lovegrass. Other perennials, such as Bahia Grass and Seri­ cea Lespedeza, are slow to become established and should be planted with another perennial spe­ cies. The additional species will provide quick cover and ample soil protection until the target perennial species become established. For example, Com­ mon seeding combinations are 1) Weeping Loveg­ rass with Sericea Lespedeza (scarified) and 2) Tall Fescue with Sericea Lespedeza (unscarified). Plant selection may also include annual compan­ ion crops. Annual companion crops should be used only when the perennial species are not planted during their optimum planting period. A common mixture is Brown Top Millet with Common Bermuda in mid-summer. Care should be taken in select­ ing companion crop species and seeding rates because annual crops will compete with perennial species for water, nutrients, and growing space. A high seeding rate of the companion crop may prevent the establishment of perennial species. Ryegrass shall not be used in any seeding mixtures containing perennial species due to its ability to out-compete desired species chosen for permanent perennial cover. Seed Quality The term “pure live seed” is used to express the quality of seed and is not shown on the label. Pure live seed, PLS, is expressed as a percent­ age of the seeds that are pure and will germi­ nate. Information on percent germination and purity can be found on seed tags. PLS is deter­ mined by multiplying the percent of pure seed with the percent of germination; i.e., (PLS = % germination x % purity) EXAMPLE: Common Bermuda seed 70% germination, 80% purity PLS = 70% germination x 80% purity PLS = 56% The percent of PLS helps you determine the amount of seed you need. If the seeding rate is 10 pounds PLS and the bulk seed is 56 % PLS, the bulk seeding rate is: 10 lbs. PLS/acre = 17.9 lbs/acre 56% PLS You would need to plant 17.9 lbs/acre to provide 10 lbs/acre of pure live seed. Seedbed Preparation Seedbed preparation may not be required where hydraulic seeding and fertilizing equip­ ment is to be used (but is strongly recommended for any seeding process, when possible). When conventional seeding is to be used, seedbed preparation will be done as follows: Broadcast plantings 1. Tillage, at a minimum, shall adequately ---PAGE BREAK--- 6-38 2016 Edition loosen the soil to a depth of 4 to 6 inches; alleviate compaction; incorporate lime and fertilizer; smooth and firm the soil; allow for the proper placement of seed, sprigs, or plants; and allow for the anchoring of straw or hay mulch if a disk is to be used. 2. Tillage may be done with any suitable equipment. 3. Tillage should be done on the contour where feasible. 4. On slopes too steep for the safe operation of tillage equipment, the soil surface shall be pitted or trenched across the slope with appropriate hand tools to provide two places 6 to 8 inches apart in which seed may lodge and germinate. Hydraulic seeding may also be used. Individual Plants 1. Where individual plants are to be set, the soil shall be prepared by excavating holes, opening furrows, or dibble planting. 2. For nursery stock plants, holes shall be large enough to accommodate roots without crowding. 3. Where pine seedlings are to be planted, subsoil under the row 36 inches deep on the contour four to six months prior to planting. Subsoiling should be done when the soil is dry, preferably in August or September. Inoculants All legume seed shall be inoculated with ap- propriate nitrogen-fixing bacteria. The inoculant shall be a pure culture prepared specifically for the seed species and used within the dates on the container. A mixing medium recommended by the manu- facturer shall be used to bond the inoculant to the seed. For conventional seeding, use twice the amount of inoculant recommended by the manufacturer. For hydraulic seeding, four times the amount of inoculant recommended by the manufacturer shall be used. All inoculated seed shall be protected from the sun and high temperatures and shall be planted ­ ---PAGE BREAK--- 6-39 2016 Edition tion establishment enhancement, and erosion control effectiveness. Select the mulching mate­ rial from the following and apply as indicated: 1. Dry straw or dry hay of good quality and free of weed seeds can be used. Dry straw shall be applied at the rate of 2 tons per acre. Dry hay shall be applied at a rate of 2 1/2 tons per acre. 2. Wood cellulose mulch or wood pulp fiber shall be used with hydraulic seeding. It shall be applied at the rate of 500 pounds per acre. Dry straw or dry hay shall be applied (at the rate indicated above) after hydraulic seeding. 3. One thousand pounds of wood cellulose or wood pulp fiber, which includes a tackifier, shall be used with hydraulic seeding on slopes 3/4:1 or steeper. 4. Sericea Lespedeza hay containing mature seed shall be applied at a rate of three tons per acre. 5. Pine straw or pine bark shall be applied at a thickness of 3 inches for bedding purposes. Other suitable materials in sufficient quantity may be used where ornamentals or other ground covers are planted. This is not ap­ propriate for seeded areas. 6. When using temporary erosion control blan­ kets or block sod, mulch is not required. 7. Bituminous treated roving may be applied on planted areas, slopes, in ditches or dry water­ ways to prevent erosion. Bituminous treated roving shall be applied within 24 hours after an area has been planted. Application rates and materials must meet Georgia Depart­ ment of Transportation specifications. Wood cellulose and wood pulp fibers shall not contain germination or growth inhibiting factors. They shall be evenly dispersed when agitated in water. The fibers shall contain a dye to allow visual metering and aid in uniform application during seeding. Applying Mulch Straw or hay mulch will be spread uniformly within 24 hours after seeding and/or plant­ ing. The mulch may be spread by blower-type spreading equipment, other spreading equipment or by hand. Mulch shall be applied to cover 75% of the soil surface. Wood cellulose or wood fiber mulch shall be ap­ plied uniformly with hydraulic seeding equipment. Anchoring Mulch Anchor straw or hay mulch immediately after application by one of the following methods: 1. Hay and straw mulch shall be pressed into the soil immediately after the mulch is spread. A special “packer disk”’ or disk har­ row with the disks set straight may be used. The disks may be smooth or serrated and should be 20 inches or more in diameter and 8 to 12 inches apart. The edges of the disks shall be dull enough to press the mulch into the ground without cutting it, leaving much of it in an erect position. Mulch shall not be plowed into the soil. 2. tackifiers, binders or hydraulic mulch specifically designed to tack straw, shall be applied in conjunction with or im­ mediately after the mulch is spread. Syn­ thetic tackifiers shall be mixed and applied according to manufacturer’s specifications. All tackifiers, binders or hydraulic mulch specifically designed to tack straw should be verified nontoxic through EPA 2021.0 testing. Refer to Tackifiers-Tac 3. Rye or wheat can be included with Fall and Winter plantings to stabilize the mulch. They shall be applied at a rate of one-quarter to one-half bushel per acre. 4. Plastic mesh or netting with mesh no larger than one inch by one inch may be needed to anchor straw or hay mulch on unstable soils and concentrated flow areas. These materials shall be installed and anchored according to manufacturer’s specifications. Bedding Material Mulch is used as a bedding material to con­ serve moisture and control weeds in nurseries, ornamental beds, around shrubs, and on bare areas on lawns. ---PAGE BREAK--- 6-40 2016 Edition Material Depth Grain straw 4” to 6” Grass Hay 4” to 6” Pine needles 3” to 5” Wood waste 4” to 6” Irrigation Irrigation will be applied at a rate that will not cause runoff. Topdressing Topdressing will be applied on all temporary and permanent (perennial) species planted alone or in mixtures with other species. Recommended rates of application are listed in Table 6-5.1. Second Year and Maintenance Fertilization Second year fertilizer rates and maintenance fertilizer rates are listed in Table 6-5.1. Lime Maintenance Application Apply one ton of agricultural lime every 4 to 6 years or as indicated by soil tests. Soil tests can be conducted to determine more accurate requirements, if desired. Use and Management Mow Sericea Lespedeza only after frost to ensure that the seeds are mature. Mow between November and March. Bermudagrass, Bahiagrass and Tall Fescue may be mowed as desired. Maintain at least 6 inches of top growth under any use and management. Moderate use of top growth is beneficial after es­ tablishment. Exclude traffic until the plants are well estab­ lished. Because of the quail nesting season, mowing should not take place between May and September. ---PAGE BREAK--- 6-41 2016 Edition Table 6-5.1. Fertilizer Requirements ANALYSIS OR N TYPE OF SPECIES YEAR EQUIVALENT RATE TOP DRESSING N-P-K RATE 1. Cool season First 6-12-12 1500 lbs./ac. 50-100 lbs./ac. 1/2/ grasses Second 6-12-12 1000 lbs./ac. Maintenance 10-10-10 400 lbs./ac. 30 2. Cool season First 6-12-12 1500 lbs./ac. 0-50 lbs./ac. 1/ grasses and Second 0-10-10 1000 lbs./ac. legumes Maintenance 0-10-10 400 lbs./ac. 3. Ground covers First 10-10-10 1300 lbs./ac. 3/ Second 10-10-10 1300 lbs./ac. 3/ Maintenance 10-10-10 1100 lbs./ac. 4. Pine seedlings First 20-10-5 one 21-gram pellet per seedling placed in the closing hole 5. Shrub Lespedeza First 0-10-10 700 lbs./ac. Maintenance 0-10-10 700 lbs./ac. 4/ 6. Temporary First 10-10-10 500 lbs./ac. 30 lbs./ac. 5/ cover crops seeded alone 7. Warm season First 6-12-12 1500 lbs./ac. 50-100 lbs./ac. 2/6/ grasses Second 6-12-12 800 lbs./ac. 50-100 lbs./ac. 2/ Maintenance 10-10-10 400 lbs./ac. 30 lbs./ac. 8. Warm season First 6-12-12 1500 lbs./ac. 50 lbs./ac./6/ grasses and Second 0-10-10 1000 lbs./ac. legumes Maintenance 0-10-10 400 lbs./ac. 1/ Apply in spring following seeding. 2/ Apply in split applications when high rates are used. 3/ Apply in 3 split applications. 4/ Apply when plants are pruned. 5/ Apply to grass species only. 6/ Apply when plants grow to a height of 2 to 4 inches. ---PAGE BREAK--- 6-42 2016 Edition Table 6-5.2- Permanent Cover Crops PLANT, PLANTING RATE, AND PLANTING DATE FOR PERMANENT COVER 1 Species Broadcast Rates Resource Area3 Planting Dates by Resource Area Remarks Solid lines indicate optimum dates, dotted lines indicate permissible but marginal dates. Rate Per Acre2 Pure Live Seed (PLS) Per 1000 sqft J F M A M J J A S O N D BAHIA, PENSACOLA Paspalum notatum alone or with temporary cover 60 lbs 1.4 lbs P C 166,000 seed per pound. Low growing. Sod forming. Slow to establish. Plant with a companion crop. Will spread nto bermuda pastures and awns. Mix with Sericea lespe- deza or weeping lovegrass. with other perennials 30 lbs 0.7 lb BAHIA, WILMINGTON Paspalum notatum alone or with temporary cover 60 lbs 1.4 lb M-L Same as above. with other perennials 30 lbs 0.7 lb P BERMUDA, COMMON Cynodon dactylon Hulled seed P 1,787,000 seed per pound. Quick cover. Low growing and sod forming. Full sun. *RRGIRUDWKOHWLF¿OHGV alone 10 lbs 0.2 lb C with other perennials 6 lbs 0.7 lb BERMUDA, COMMON Cynodon dactylon Unhulled seed P C Plant with winter annuals. Plant with Tall Fescue with temporary cover 10 lbs 0.2 lb with other perennials 6 lbs 0.1 lb ---PAGE BREAK--- 6-43 2016 Edition Table 6-5.2- Permanent Cover Crops PLANT, PLANTING RATE, AND PLANTING DATE FOR PERMANENT COVER 1 Species Broadcast Rates Resource Area3 Planting Dates by Resource Area Remarks Solid lines indicate optimum dates, dotted lines indicate permissible but marginal dates. Rate Per Acre2 Pure Live Seed (PLS) Per 1000 sqft J F M A M J J A S O N D BERMUDA SPRIGS Cynodon dactylon Coastal, Common, Midland, or Tift 44 40 cu ft 0.9 cu ft or sod plugs 3’ x3’ M-L A cubic foot contains approximately 650 sprigs. A bushel contains 1.25 cubic feet or approximately 800 springs. Same as above. Southern Coastal Plain only Coastal, Common, of Tift 44 P C Tift 78 C CENTIPEDE Eremochloa ophuiroides Block sod only P C Drought tolerant. Full sun or partial shade. Effective adjacent to concrete and in con- until fully established. Do not plant near pastures. Winterhardy as far as north Athens and Atlanta CROWNVETECH Coronilla varia with winter annuals or cool season grasses 15 lbs 0.3 lb M-L P 100,000 seed per pound. Dense growth. rose, pink and white blossoms spring to late fall. Mix with 30 pounds of Tall fescue or 15 pounds of rye. Inoculate see with M inocu- lant. Use from North Atlanta and Northward. ---PAGE BREAK--- 6-44 2016 Edition Table 6-5.2- Permanent Cover Crops PLANT, PLANTING RATE, AND PLANTING DATE FOR PERMANENT COVER 1 Species Broadcast Rates Resource Area3 Planting Dates by Resource Area Remarks Solid lines indicate optimum dates, dotted lines indicate permissible but marginal dates. Rate Per Acre2 Pure Live Seed (PLS) Per 1000 sqft J F M A M J J A S O N D FESCUE, TALL Festuca arundinacea alone 50 lbs 1.1 lb M-L P 227,000 seed per pound. Use alone only on better sites. Mix with perennial lespededza or Crownvetch. Apply topdressing in spring following fall plantings. Not for heavy use DUHDVRUDWKOHWLF¿HOGV with other perennials 30 lbs 0.7 lb KUDZU Pueraria thumbergiana Plants or crowns 3’ - 7’ apart ALL Rapid and vigorous growth. Excellent in gully erosion control. Will climb. Good livestock forage. LESPEDEZA SERICEA Lespedeza cuneata VFDUL¿HG 60 lbs 1.4 lb M-L P C 350,000 seed per pound. Widely adapted. Low maintenace. Mix with Weeping loveg- rass, Common bermuda, bahia, or tall fescue. Takes 2 to 3 years to become fully established. Excellent on roadbanks. Inocu- late seed with EL inoculant. Mix with Tall fesue or winter annuals. Cut when seed mixture is mature, but be- fore, it shatters. Add Tall fescue or winter annuals. 75 lbs 1.7 lb M-L P C seed- bearing hay 3 tons 1338 lbs M-L P C ---PAGE BREAK--- 6-45 2016 Edition Table 6-5.2- Permanent Cover Crops PLANT, PLANTING RATE, AND PLANTING DATE FOR PERMANENT COVER 1 Species Broadcast Rates Resource Area3 Planting Dates by Resource Area Remarks Solid lines indicate optimum dates, dotted lines indicate permissible but marginal dates. Rate Per Acre2 Pure Live Seed (PLS) Per 1000 sqft J F M A M J J A S O N D LESPEDEZA Ambro virgata Lespedeza virgata DC or Appalow Lespedeza cuneata (Dumont) G. Don) VFDUL¿HG 60 lbs 1.4 lb M-L P C M-L P C 300,000 seed per pound. Height of growth is 18 to 24 inches. Advantageous in urban ar- eas. Spreading-type growth. New growth has bronze coloration. Mix with weeping loveg- rass, common bermuda, bahia, tall fescue or winter annuals. Do not mix with Sericea lespedeza. Slow to develop solid stands. Inoculate seed with EL inoculant. 75 lbs 1.7 lb LESPEDEZA, SHRUB Lespedeza bicolor Lespedeza thumbergii plants 3’ x3’ M-L P C Provide wildlife food and cover. LOVEGRASS, WEEPING Eragrostis curvula alone 4 lbs 0.1 lb M-L P C 1,500,000 seed per pound. Quick cover. Drought tolerant. Grows well with Sericea lespedeza on roadbanks. with other perennials 2 lbs 0.05 lb ---PAGE BREAK--- 6-46 2016 Edition Table 6-5.2- Permanent Cover Crops PLANT, PLANTING RATE, AND PLANTING DATE FOR PERMANENT COVER 1 Species Broadcast Rates Resource Area3 Planting Dates by Resource Area Remarks Solid lines indicate optimum dates, dotted lines indicate permissible but marginal dates. Rate Per Acre2 Pure Live Seed (PLS) Per 1000 sqft J F M A M J J A S O N D MAIDENCANE Panicum hemitomon sprigs 2’ x 3’ spacing ALL For very wet sites. May clog channels. Dig sprigs from local sources. Use along river banks and shorelines. PANICGRASS, ATLANTIC COASTAL Panicum amarum var amarukum 20 lbs 0.5 lb P C Grows well on coastal sand dunes, borrow areas, and gravel pits. Provides winter cover for wildlife. Mix with Sericea lespedeza except on sand dunes. REED CANARY GRASS Phalaris arundinacea alone 50 lbs 1.1 lb M-L Grows similar to Tall fescue with other perrenials 30 lbs 0.7 lb P SUNFLOWER, ‘AZTEC’ MAXIMILLIAN Helianthus maximiliani 10 lbs 0.2 lb M-L P C 227,000 seed per pound. Mix with Weeping lovegrass or other low-grwoing grasses or legumes. 1 Reduce seeding rates by 50% when drilled 3 M-L represents to Mountain; Blue Ridge; and Ridges and Valleys MLRAs P represents the Southern Piedmont MLRA C represents the Souther Coastal Plain;Sand Hills;Black Lands;and Atlantic Coast Flatwoods MLRAs. See Figure 6-4.1 ---PAGE BREAK--- 6-47 2016 Edition Table 6-5.3. Durable Shrubs and Ground Covers for Permanent Cover Ground covers include a wide range of low-growing plants planted together in considerable numbers to cover large areas of the landscape. Ground covers grow slower than grasses. Weeds are likely to compete, especially the first year. Maintenance is needed to insure survival. These ground covers will not be used unless proper maintenance is planned. Maintain mulch at three-inch thickness until plants provide adequate cover. Fall planting is encouraged because the need for constant watering is reduced and plants have time to establish new roots before hot weather. ---PAGE BREAK--- 6-48 2016 Edition Table 6-5.3. Durable Shrubs and Ground Covers for Permanent Cover ---PAGE BREAK--- 6-49 2016 Edition Table 6-5.3. Durable Shrubs and Ground Covers for Permanent Cover ---PAGE BREAK--- 6-50 2016 Edition Table 6-5.4. Trees for Erosion Control 1 Other trees and shrubs listed on Table 6-25.3 may be interplanted with the pines for improved wildlife benefits. 2 Type of Planting Tree Spacing No. of Trees Per Acre Trees alone 4 ft. x 4 ft. 2722 Trees in combination with grasses and/or other plants 6 ft. x 6 ft. 1210 3 M-L represents the Mountains; Blue Ridge; and Ridges and Vallevs MLRAs P represents the Southern Piedmont MLRA C represents the Southern Coastal Plain; Sand Hills; Black Lands; and Atlantic Coast Flatwoods ML RAs (See Figure 6-4.1). 4 Fertilization of companion crop is ample for this species. SITE SOIL MATERIAL COMMON SOILS PLANTING TREE SPECIES1 SPACING PLANTING DATES3 Borrow areas, graded areas, and spoil material Sandy Loamy Clay Lakeland, Troup Orangeburg, Tifton Cecil, Facevillle Loblolly pine (Pinus taeda) Longleaf pine (Pinus palustris) Loblolly pine Slash pine Loblolly pine Slash pine Virginia pine (Pinus virginiana) 2 2 2 M-L,P 12/1-3/15 C 12/1-3/1 M-L,P 12/1-3/15 C 12/1-3/1 M-L,P 12/1-3/15 C 12/1-3/1 Streambanks Willows4 (Salix speciecs) 2 ft x 2 ft ALL ---PAGE BREAK--- 6-51 2016 Edition DEFINITION A permanent vegetative cover using sods on highly erodible or critically eroded lands. PURPOSE • Establish immediate ground cover. • Reduce runoff and erosion. • Improve aesthetics and land value. • Reduce dust and sediments. • Stabilize waterways, critical areas. • Filter sediments, nutrients and bugs. • Reduce complaints. • Reduce likelihood of legal action. • Reduce likelihood of work stoppage due to legal action. • Increase “good neighbor” benefits. CONDITIONS This application is appropriate for areas that require immediate vegetative covers, drop inlets, grass swales, and waterways with intermittent flow. PLANNING CONSIDERATIONS Sodding can initially be more costly than seeding, but the advantages justify the increased initial costs: 1. Immediate erosion control, green surface, and quick use. 2. Reduced failure as compared to seed as well as the lack of weeds. 3. Can be established nearly year-round. Sodding is preferable to seed in waterways and swales because of the immediate protection of the channel after application. Sodding must be staked in concentrated flow areas (See Figure 6-6.1). Consider using sod framed around drop inlets to reduce sediments and maintaining the grade. CONSTRUCTION SPECIFICATIONS Soil Preparation Bring soil surface to final grade. Clear surface of trash, woody debris, stones and clods larger than Apply sod to soil surfaces only and not frozen surfaces, or gravel type soils. Topsoil properly applied will help guarantee a stand. Don’t use topsoil recently treated with her­ bicides or soil sterilants. Mix fertilizer into soil surface. Fertilize based on soil tests or Table 6-6.1. Agricultural lime should be applied based on soil tests or at a rate of 1 to 2 tons per acre. Installation Lay sod with tight joints and in straight lines. Don’t overlap joints. Stagger joints and do not stretch sod (See Figure 6-6.2) On slopes steeper than 3:1, sod should be anchored with pins or other approved methods. Installed sod should be rolled or tamped to provide good contact between sod and soil. DISTURBED AREA STABILIZATION (WITH SODDING) Ds4 Table 6-6.1. Fertilizer Requirements for Soil Surface Application Fertilizer Type Fertilizer Rate (lbs/acre) Fertilizer Rate (lbs/sq ft) Season 10-10-10 1000 .025 Fall ---PAGE BREAK--- 6-52 2016 Edition Irrigate sod and soil to a depth of 4” immediately after installation. Sod should not be cut or spread in extremely wet or dry weather. Irrigation should be used to supplement rainfall for a minimum of 2-3 weeks. MATERIALS Sod selected should be certified. Sod grown in the general area of the project is desirable. 1. Sod should be machine cut and contain 3/4” or of soil, not including shoots or thatch. 2. Sod should be cut to the desired size within + or Torn or uneven pads should be rejected. 3. Sod should be cut and installed within 36 hours of digging. 4. Avoid planting when subject to frost heave or hot weather, if irrigation is not available. 5. The sod type should be shown on the plans or installed according to Table 6-6.2. See Figure 6-4.1 for your Resource Area. MAINTENANCE Re-sod areas where an adequate stand of sod is not obtained. New sod should be mowed sparingly. Grass height should not be cut less than 2”-3” or as specified (See Figure 6-6.2). Apply one ton of agricultural lime as indicated by soil test or every 4-6 years. Fertilize grasses in accordance with soil tests or Table 6-6.3. Table 6-6.2 Sod Planting Requirements Grass Varieties Resource Area Growing Season Bermudagrass Common Tifway Tifgreen Tiflawn M-L,P,C P,C P,C P,C warm weather Bahiagrass Pensacola P,C warm weather Centipede _ P,C warm weather St. Augustine Common Bitterblue Raleigh C warm weather Zoysia Emerald Myer P,C warm weather Tall Fescue Kentucky M-L,P cool weather Table 6-6.3 Fertilizer Requirements for Sod Types of Species Planting Year Fertilizer (N-P-K) Rate (lbs./acre) Nitrogen Top Dressing Rate (lbs./acre) cool season grasses first second maintenance 6-12-12 6-12-12 10-10-10 1500 1000 400 50-100 - 30 warm season grasses first second maintenance 6-12-12 6-12-12 10-10-10 1500 800 400 50-100 50-100 30 ---PAGE BREAK--- 6-53 2016 Edition Figure 6-6.1 Source: Va. DSWC ---PAGE BREAK--- 6-54 2016 Edition Source: Va. DSWC Figure 6-6.2 ---PAGE BREAK--- 6-55 2016 Edition DEFINITION Controlling surface and air movement of dust on construction sites, roads, and demolition sites. PURPOSE •To prevent surface and air movement of dust from exposed soil surfaces. •To reduce the presence of airborne substances that may be harmful or injurious to human health, welfare, or safety, or to animals or plant life. CONDITIONS This practice is applicable to areas subject to surface and air movement of dust where on and off-site damage may occur without treatment. METHOD AND MATERIALS A. Temporary Methods Mulches. See standard Ds1 - Disturbed Area Stabilization (With Mulching Only). resins may be used instead of asphalt to bind mulch material. Refer to specification Tac - Tackifiers. Resins should be used according to manufacturer’s recommendations. Vegetative Cover. See specification Ds2 - Disturbed Area Stabilization (With Temporary Seeding). Spray-on Adhesives. These are used on miner­ al soils (not effective on muck soils). Keep traffic off these areas. Refer to specification Tac - Tackifiers. Tillage. This practice is designed to roughen and bring clods to the surface. It is an emergency measure that should be used before wind ero­ sion starts. Begin plowing on windward side of site. Chisel-type plows spaced about 12 inches apart, spring-toothed harrows, and similar plows are examples of equipment that may produce the desired effect. Irrigation. This is generally done as an emer­ gency treatment. Site is sprinkled with water until the surface is wet. Repeat as needed. Barriers. Solid board fences, snowfences, burlap fences, crate walls, bales of hay and similar material can be used to control air currents and soil blowing. Barriers placed at right angles to prevailing currents at intervals of about 15 times their height are effective in controlling wind erosion. Calcium Chloride. Apply at rate that will keep surface moist. May need retreatment. B. Permanent Methods Permanent Vegetation. See specification Ds3 -Disturbed Area Stabilization (With Permanent Vegetation). Existing trees and large shrubs may afford valuable protection if left in place. Topsoiling. This entails covering the surface with less erosive soil material. See specification Tp - Topsoiling. Stone. Cover surface with crushed stone or coarse gravel. See specification Cr-Construction Road Stabilization. Dust Control on Disturbed Areas Du ---PAGE BREAK--- 6-56 2016 Edition ---PAGE BREAK--- 6-57 2016 Edition Flocculants Coagulants DEFINITION Flocculants and Coagulants (Fl-Co) are formu­ lated to assist in the solids/liquid separation of suspended particles in solution. Such particles are characteristically very small and the sus­ pended stability of such particles (colloidal com­ plex) is due to both their small size and to the electrical charge between particles. Conditioning a solution to promote the removal of suspended particles requires chemical coagulation and/or flocculation. A coagulant is required to help give body to the water. Coagulants neutralize the repulsive elec­ trical charges (typically negative) surrounding particles allowing them to “stick together” creat­ ing clumps or flocs that form a small to mid-size particles (sometimes called a pin-floc). Once the pin-floc has formed, a second chemical called a flocculent is required to make even larger par­ ticles. Flocculants facilitate the agglomeration or aggregation of the coagulated particles to form larger floccules and acts as a net where it gath­ ers up the smaller coagulated particles making a larger particle. This larger particle will slowly drop to the bottom of the container (vessel), forming a sludge. Coagulation and Flocculation occur in succes­ sive order. the forces stabilizing suspend­ ed particles are neutralized allowing particles to meet (coagulate) and secondly, to form larger, heavier flocs (flocculants). PURPOSE To settle suspended sediment, heavy metals and hydrocarbons (TSS) in runoff water from Fl-Co construction sites for water clarification. CONDITIONS Water clarification and the removal of turbid­ ity will usually require the addition of flocculants, polymers, polyacrylamides (PAM), chitosan and other chemicals that cause soil particles to bind together, become heavy and settle to the bottom of a sediment trap, sediment basin or become entrapped in other BMPs. This practice is not intended for application to surface waters of the state. It is intended for ap­ plication within construction storm water ditches and storm drainages that feed into pre-construct­ ed ponds or basins or other BMPs. Federal and Local Laws Fl-Co applications shall comply with all federal, local laws, rules or regulations governing Fl-Co. The operator is responsible for securing appli­ cable required permits, if needed. This standard does not contain the text of the federal or local laws governing Flocculants/Coagulants. Planning Considerations Since settling of flocculated soil particles requires very slow moving (still) water, chemi­ cal additives should never be introduced into an outfall BMP where water leaves the property or enters state waters. In all cases where chemical additives are used to reduce turbidity, it is es­ sential to include a sediment basin or sediment trap unless using a “pump and treat” treatment system. CRITERIA Application rates shall conform to manufac­ turer’s guidelines for application. Only anionic forms of Fl-Co shall be used. Following are examples of Fl-Co applications within construction storm water ditches or drain­ ageways that feed into sediment basins or other BMPs: •Fl-Co Bags or Socs that are installed directly in a ditch, pipe or culvert. •Fl-Co treated ditch checks (i.e. fiber rolls, wattles, or compost logs inoculated or used in conjunction with Fl-Co •Granulated Fl-Co treated rock ditch checks. ---PAGE BREAK--- 6-58 2016 Edition •Ditch checks with attached Fl-Co Bags or Socs. •Addition of granular Fl-Co directly into a ditch. •Erosion control blankets and turf reinforce- ment mats that have been inoculated with a Fl-Co . •“Pump and Treat” systems that use mechani- cal mixing with a chemical treatment of a Fl-Co. Operation and Maintenance Application rates shall conform to manufactur­ er’s guidelines for application. Maintenance shall consist of reapplying Fl-Co via one of means above when turbidity levels are no longer met or the Fl-Co is used up. Bricks, blocks, socks,logs and bags shall be maintained when sediment sediment accumulates on the products. ---PAGE BREAK--- 6-59 2016 Edition DEFINITION The use of readily available native plant mate­ rials to maintain and enhance streambanks, or to prevent, or restore and repair small streambank erosion problems. PURPOSE •Lessen the impact of rain directly on the soil. •Trap sediment from adjacent land. •Form a root mat to stabilize and reinforce the soil on the streambank. •Provide wildlife habitat. •Enhance the appearance of the stream. •Lower summertime water temperatures for a healthy aquatic population. NOTE: Careful thought, planning and ex­ ecution is required to assure that the streambank stabilization project is done efficiently and cor­ rectly. Please refer to the guidance document,STREAMBANK AND SHORELINE STABILIZATION. Preferred Practices: Live Staking Live stakes are living, woody plant cuttings capable of rooted when inserted into the banks. These stakes, commonly willow species, can root and grow into shrubs that overtime will stabilize thestreambank or shoreline and provide riparian habitat. STREAMBANK STABILIZATION (USING PERMANENT VEGETATION) Live Fascines Live facines are bound bundles of live branch cuttings that are buried onto the bank and staked into place along the slope contour. Willow branches are the most commonly used for this method. Branchpacking Branchpacking is the process of incorporating alternating layers of live branch cuttings and compacted soils into a hole, gully or slump. This method is used to fill in depressions along the streambank or shoreline. Vegetated Geogrid Vegetated geogrids are similar to branchpacking except that natural or geotextile materi­ als are wrapped around each soil lift between the layers of live branch cuttings. Brushmattress A brushmattress system consists of live branch cuttings, live stakes, and live fascines installed to cover and stabilize the entire streambank/ shoreline and secured in place. This method is installed above the normal stream flow and pro­ vides immediate protective coverage of the bank. Coconut Fiber Roll A coconut fiber roll is a flexible “log” made from coconut hull fibers, staked at the toe of the bank. The technique is often used in conjunction with native plants to trap sediment and encourage plant growth. Dormant Post Plantings (Live Posts) Dormant post plantings form a permeable revet­ ment that is constructed from rootable vegetative material placed along streambanks in a square or triangular pattern. Acceptable Practices Joint Planting Joint planting or vegetated riprap involves tamping live stakes into joints or open spaces in rocks that have been placed on a slope. Vegeta­ tion, especially deep rooting species, planted above and immediately behind the rock will greatly increase the stability of the slope Live Cribwall A live cribwall is a box-like structure with a Sb ---PAGE BREAK--- 6-60 2016 Edition framework of logs or timbers, rock and live cut­ tings that can protect eroding streambanks or shorelines. Once live cuttings become estab­ lished, mature vegetation gradually takes over the structural functions of the logs or timbers. Vegetated Gabion Baskets Gabion baskets are rectangular containers fabricated from a heavily galvanized steel wire or riple twisted hexagonal mesh. These empty gabions are placed in position, wired to adjoining gabions, filled with stones, and then wired shut. Vegetation is incorporated into rock gabions by placing live branches on each consecutive layer between the rock filled baskets. Tree Revetments Tree revetments are rows of cut trees anchored to the toe of the bank. This is a low cost method, often used for toe protection with other bioengineering techniques. Log Rootwad and Boulder Revetments These revetments are systems composed of logs, rootwads, and boulders selectively placed in and on streambanks. Discouraged Practices Rock Riprap Riprap stabilization designs should include appropriate bank slope and rock size to protect the bank from wave and current action and to prolong the life of the embankment. A final slope ratio of at least 1:2 (vertical to horizontal) is rec­ ommended, and a more stable 1:3 slope should be used where possible. A layer of gravel, small stone, or filter cloth placed under and/or behind the rock helps prevent failure. In many cases, only the toe of the slope may need rock reinforcement; the re­ mainder can be planted with native vegetation. Rock Gabions Rock gabions with vegetation are a more acceptable stabilization practice. Bulkheads and Seawalls Bulkheads and seawalls are not encouraged and generally are not approved. These structures (typically sheet steel, concrete or wood) produce a sterile, vertical, flat-faced object that is of little use to aquatic organisms and other wildlife. They also tend to reflect wave energy rather than dissipate it, usually resulting in erosion problems in front of the “fix” and elsewhere. ---PAGE BREAK--- 6-61 2016 Edition Table 6-9.1 Streambank Erosion Protection Measures Relative Costs and Complexity Measure Relative Cost Relative Complexity Live Stake Low Simple Joint Planting Low* Simple* Live Fascine Moderate Moderate Bushmatress Moderate Moderate to Complex Live Cribwall High Complex Branchpacking Moderate Moderate to Complex Conventional Vegetation Low to Moderate Simple to Moderate Converntional bank amoring (rip rap) Moderate to High Moderate to Complex *Assumes rock is in place ---PAGE BREAK--- 6-62 2016 Edition Figure 6-9.1 Illustration of a Live Stake ---PAGE BREAK--- 6-63 2016 Edition Figure 6-9.2 Illustration of a Live Fascine ---PAGE BREAK--- 6-64 2016 Edition Figure 6-9.3 Illustration of a Branchpacking ---PAGE BREAK--- 6-65 2016 Edition Figure 6-9.4 Illustration of a Brushmattress ---PAGE BREAK--- 6-66 2016 Edition Figure 6-9.5 Illustration of Joint Planting ---PAGE BREAK--- 6-67 2016 Edition Figure 6-9.6 Illustration of a Live Cribwall ---PAGE BREAK--- 6-68 2016 Edition ---PAGE BREAK--- 6-69 2016 Edition DEFINITION A protective covering used to prevent erosion and establish temporary or permanent vegetation on steep slopes, shore lines, or channels. PURPOSE To provide a cover layer that stabilizes the soil and acts as a rain drop impact dissipater while providing a microclimate that protects young veg­ etation and promotes its establishment. If using slope stabilization to reinforce channels, please refer to specification, Ch- Channel Stablization. CONDITIONS Slope stabilization can be applied to flat areas or slopes where the erosion hazard is high and slope protection is needed during the establish­ ment of vegetation. PLANNING CONSIDERATIONS Care must be taken to choose the type of slope stabilization product that is most appro­ priate for the specific needs of a project. Two general types of slope stabilization products are discussed within this specification. Rolled Erosion Control Products (RECP) A natural fiber blanket with single or double photodegradable or biodegradable nets. Hydraulic Erosion Control Products (HECP) HECP shall utilize straw, cotton, wood or other natural based fibers held together by a soil binding agent that works to stabilize soil parti­ cles. Paper mulch should not be used for erosion control. Slope Stabilization CRITERIA Rolled Erosion Control Products (RECPs) and Hydraulic Erosion Control Products (HECPs): •Installation and stapling of RECPs and application rates for the HECPs shall conform to manufacturer’s guidelines for application •Short-Term RECPs as a minimum shall be used to stabilize concentrated flow areas with a velocity less than 5ft/sec on slopes 3:1 or greater with a height of 10 feet or greater. Materials – HECP Hydraulic erosion control products shall be prepackaged from the manufacturer. Field mix­ ing of performance enhancing additives will not be allowed. Fiberous components should be all natural or biodegradable. Products shall be determined to be non-toxic in accordance with EPA-821-R-02-012. Materials – RECP Blankets shall be nontoxic to vegetation, seed, or wildlife. Products shall be determined to be non-toxic in accordance with EPA- 821-R-02-012. At minimum, the plastic or biode­ gradable netting shall be stitched to the fibrous matrix to maximize strength and provide for ease of handling. RECPs are categorized as follows: a. Short-Term (functional longevity 12 mo.) i. Photodegradable Straw blankets with a top and bottom side photo degradable net. The maximum size of the mesh should be openings of ½” X The blan­ ket should be sewn together on 1.5” centers with degradable thread. Minimum thickness should be 0.35” and minimum density should be 0.5 lbs per square yard. ii. Biodegradable Straw blanket with a top and bottom side biodegradable jute net. The top side net should consist of machine direction strands that are Ss ---PAGE BREAK--- 6-70 2016 Edition twisted together and then interwoven with cross direction strands (leno weave). The bottom net may be leno weave or otherwise to meet re­ quirements. The approximate size of the mesh should be openings of 0.5” X 1.0”. The blanket should be sewn together on 1.5” centers with degradable thread. Minimum thickness should be 0.25” and minimum density should be 0.5 lbs per square yard. b. Extended-Term (functional longevity 24 mo.) i.Photodegradable Blankets that consist of 70% straw and 30% coconut with a top and bottom side photodegrad­ able net. The top net should have ultraviolet additives to delay breakdown. The maximum size of the mesh should be openings of 0.65” X 0.65”. The blanket should be sewn together on 1.5” centers with degradable thread. Minimum thickness should be 0.35” and minimum density should be 0.6 lbs per square yard. ii.Biodegradable Blankets that consist of 70% straw and 30% coconut with a top and bottom side biodegrad­ able jute net. The top side net should consist of machine direction strands that are twisted to­ gether and then interwoven with cross direction strands (leno weave). The bottom net may be leno weave or otherwise to meet requirements. The approximate size of the mesh should be openings of 0.5” X 1.0”. The blanket should be sewn together on 1.5” centers with degradable thread. Minimum thickness should be 0.25” and minimum density should be 0.65 lbs per square yard. c. Long-Term (functional longevity 36 mo.) i. Photodegradable Blankets that consist of 100% coconut with a top and bottom side photodegradable net. Each net should have ultraviolet additives to delay breakdown. The maximum size of the mesh should be openings of 0.65” X 0.65”. The blanket should be sewn together on 1.5” centers with degradable thread. Minimum thickness should be 0.3” and minimum density should be 0.5 lbs per square yard. iii. Biodegradable Blankets that consist of 100% coconut with a top and bottom side biodegradable jute net. The top side net should consist of machine direction strands that are twisted together and then inter­ woven with cross direction strands (leno weave). The bottom net may be leno weave or otherwise to meet requirements. The approximate size of the mesh should be openings of 0.5” X 1.0”. The blanket should be sewn together on 1.5” cen­ ters with degradable thread. Minimum thickness should be 0.25” and minimum density should be 0.5 lbs per square yard. NOTES It is the intention of this section to allow inter­ changeable use of RECPs and HECPs for ero­ sion protection on slopes. The project engineer should select the type of erosion control product that best fits the need of the particular site. Site Preparation After the site has been shaped and graded to the approved design, prepare a friable seedbed relatively free from clods and rocks more than one inch in diameter, and any foreign material that will prevent contact of the soil stabiliza­ tion mat with the soil surface. Surface must be smooth to ensure proper contact of blankets or matting to the soil surface. If necessary, redirect any runoff from the ditch or slope during installa­ tion. MAINTENANCE All erosion control blankets and matting should be inspected periodically following instal­ lation, particularly after rainstorms to check for erosion and undermining. Any dislocation or fail­ ure should be repaired immediately. If washouts or breakage occurs, reinstall the material after repairing damage to the slope or ditch. Continue to monitor these areas until they become perma­ nently stabilized. ---PAGE BREAK--- 6-71 2016 Edition Figure 6-10.1 - Typical Installation Guidelines for Matting and Blankets ---PAGE BREAK--- 6-72 2016 Edition ---PAGE BREAK--- 6-73 2016 Edition DEFINITION Tackifiers are used as a tie-down for soil, compost, seed, straw, hay or mulch. Tackifiers hydrate in water and readily blend with other slurry materials to form a homogenous slurry. PURPOSE To reduce soil erosion from wind and water on construction sites. Other benefits include soil infiltration, soil fertility, enhanced seed germi­ nation, increased soil cohesion, enhanced soil stabilization, reduced stormwater runoff turbidity and reduction in loss of topsoil. CONDITIONS This practice is intended for direct soil surface application to sites where the timely establish­ ment of vegetation may not be feasible or where vegetation cover is absent or inadequate. Such areas include construction areas, where plant residues are inadequate to protect the soil sur­ face and where land disturbing activities prevent the establishment or maintenance of a vegetative cover. CRITERIA Type I Tackifiers: Polymers •Application rates shall conform to manufacturer’s guidelines for application. •Only anionic forms of PAM shall be used. Anionic PAMs shall be no more than 0.05% acrylamide monomer by weight, as TACKIFIERS Tac-1 Tac-2 Tac established by the Food and Drug Administration and the Environmental Protect- tion Agency. •Not harmful to plants, animals and aquatic life. •Contain no growth or germination inhibiting materials. •Shall not reduce infiltration rates. Type II Tackifiers: Organic Polymers Such as guar gum, polysaccharides, and starches •Application rates shall conform to manufacturer’s guidelines for application. •Derived from natural plant sources. •Not harmful to plants, animals and aquatic life. •Contain no growth or germination inhibiting materials. •Shall not reduce infiltration rates. Type III Tackifiers: Blends •Application rates shall conform to manufacturer’s guidelines for application. •Only anionic forms of PAM shall be used in the blend, and shall be no more than 0.05% acrylamide monomer by weight. •Organic material must be derived from natural plant sources. •Not harmful to plants, animals and aquatic life. •Contain no growth or germination inhibiting materials. •Shall not reduce infiltration rates. Tac-3 ---PAGE BREAK--- 6-74 2016 Edition Tac-5 Type IV Tackifiers: Organic Tackifiers with Fibers •Application rates shall conform to manufac- turer’s guidelines for application. •Organic material must be derived from natural plant sources. •Not harmful to plants, animals and aquatic life. •Contain no growth or germination inhibiting materials. •Shall not reduce infiltration rates. fibers shall be of nylon or polyester blends. Type V Tackifiers: Blends with Fibers •Application rates shall conform to manufact- urer’s guidelines for application. •Only anionic forms of PAM shall be used in the blend, and shall be no more than 0.05% acrylamide monomer by weight. •Organic material must be derived from natural plant sources. •Not harmful to plants, animals and aquatic life. •Contain no growth or germination inhibiting materials. •Shall not reduce infiltration rate. fibers shall be of nylon or polyester blends. MAINTENANCE Tackified areas should be checked after every rain event. Periodic inspections and required maintenance must be provided per manufactur­ er’s recommendations. Tac-4 ---PAGE BREAK--- 6-75 2016 Edition SECTION III: STRUCTURAL PRACTICES ---PAGE BREAK--- 6-76 2016 Edition ---PAGE BREAK--- 6-77 2016 Edition The E&S Act, O.C.G.A. § 12-7-6 and the state general permits (NPDES) Part IV., require an ES&PC Plan to be properly designed, installed and maintained using BMPs that are consistent with, and no less stringent than practices contained in this Manual. The following structural BMPs in this Manual require worksheets or specifications to be shown on, and/or with the ES&PC Plan: Check Dam (Cd), Channel Stabilization (Ch), Diversion (Di), Tempo­ rary Downdrain Structure (Dn1), Rock Filter Dam (Rd), Retofitting (Rt), Sediment Barrier (Sd1), Inlet Sediment Trap (Sd2) when excavated to provide sediment storage, Temporary Sediment Basin (Sd3), Temporary Sediment Trap (Sd4), Floating Surface Skimmer (Sk), Temporary Stream Cross­ ing (Sr), Storm Drain Outlet Protection (St), and Vegetated Waterway or Stormwater Conveyence Channel (WT). Most of the structural BMPs provide the mainte­ nance requirements, and a figure showing proper installation procedures and specifications. When the design professional has chosen to use alter­ native BMPs that are not included in the Manual, a detail and maintenance requirements must be provided by the manufacturer or the design profes­ sional, and shown on the ES&PC Plan. O.C.G.A. § 12-7-8 requires a local issuing authority (LIA) to enact an ordinance that meets or exceeds the standards, requirements, and provi­ sions of the Act and the NPDES permits. However, the ordinance that the LIA enacts may not exceed the NPDES permit requirements for monitoring, reporting, inspections, design standards, turbid­ ity standards, education and training, and project size thresholds with regard to education and train­ ing. Inspections are an important part of insuring that structural BMPs are properly maintained. For complete inspection and retention of records re­ quirements please refer to the appropriate NPDES Permit. ---PAGE BREAK--- 6-78 2016 Edition ---PAGE BREAK--- 6-79 2016 Edition Check Dam Cd DEFINITION A temporary grade control structure, or dam constructed across a swale, drainage ditch, or area of concentrated flow. PURPOSE To minimize the erosion rate by reducing the velocity of the storm water in areas of concen­ trated flow. CONDITIONS This practice is applicable for use in small open channels and is not to be used in a live stream. Specific applications include: 1.Temporary or permanent swales or ditches in need of protection during establishment of grass linings. 2.Temporary or permanent swales or ditches that, due to their short length of service or other reasons, cannot receive a permanent non-erodible lining for an extended period of time. 3.Other locations where small localized erosion and resulting sedimentation prob lems exist. DESIGN CRITERIA Check dams should be designed using 2.0 cfs. For any flows exceeding 2.0 cfs, check dams may be used in conjunction with other BMPs in the channel. Dam height should be 24 inches maximum measured to the center of the check dam. Drainage Area For stone check dams, the drainage area shall not exceed two acres. For straw-bale check dams and compost filter socks, the drainage area shall not exceed one acre. Side Slopes Side slopes shall be 2:1 or flatter. Spacing Two or more check dams in a series shall be used for drainage areas greater than one acre. Maximum spacing between dams should be such that the toe of the upstream dam is at the same elevation as the top of the dam. (See Figure 6-12.1) Geotextiles A geotextile should be used as a separator between the graded stone and the soil base and abutments. The geotextile will prevent the migra­ tion of soil particles from the subgrade into the graded stone. The geotextile shall be selected/ specified in accordance with AASHTO M288-06 Section 7.3, Separation Requirements, Table 3. Geotextiles shall be “set” into the subgrade soils. The geotextile shall be placed immediately adjacent to the subgrade without any voids and extend five feet beyond the toe of the dam to prevent scour. CONSTRUCTION SPECIFICATIONS Stone Check Dams Stone check dams should be constructed of graded size 2-10 inch stone. Mechanical or hand placement shall be required to insure compete coverage of the entire width of the ditch or swale and that the center of the dam is lower than the edges. The center of the check dam must be at least 9 inches lower than the outer edges. (See Figure 6-12.2) Straw-bale Check Dams Staked and embedded straw-bales may be used as temporary check dams in concentrated flow areas while vegetation is becoming estab­ lished. They shall not be used where the drain­ age area exceeds one acre. Straw-bales should be installed per Figure 6-12.3. Cd-S Cd-Hb ---PAGE BREAK--- 6-80 2016 Edition Installation Bales should be bound with wire or nylon string. Twine bound bales are less durable. The bales should be placed in rows with bale ends abutting the adjacent bales. Row (Refer to Figure 6-12.3) Dig a trench across the small channel, wide enough and deep enough so that the top of the row of bales placed on their long, wide side is level with the ground. The tops of bales across the center of the channel should all be level and set at the same elevation. Place the bales in position and stake them according to the instruc­ tions below. Upstream Row Dig another trench across the small channel, upstream and immediately adjacent to the first row of bales. The trench should be wide enough to accommodate a row of bales set vertically on their long edge. The trench should be deep enough so that at least 6 inches of each bale is below ground starting with the bale in the chan­ nel bottom. The trench should be as level as possible so that the tops of the bales across the center of the channel are level and water can flow evenly across them. Continue this trench up the side slopes of the small channel to a point where the unburied bottom line of the highest bale (Point Figure 6-12.3) is higher than the top of the bales that are in the center of the channel (Point Figure 6-12.3). Anchorage Drive standard 2 x 2 stakes or #4 rebar through the bales and into the ground 1 1/2 to 2 feet for anchorage. The first stake in each bale should be driven toward a previously laid bale to force the bales together (See Figure 6-12.3). Reference: Colorado NRCS Straw Bale Check Dam Compost Filter Sock The filter sock should be staked in the center. If the compost fi lter sock is to be left as a perma­ nent filter or part of the natural landscape, it may be seeded at time of installation for establish­ ment of permanent vegetation. Compost filter media used for compost filter sock filler material shall be weed free and derived from a well-decomposed source of organic matter. The compost shall be produced using an aerobic composting process meeting CFR 503 regula­ tions including time and temperature data. The compost shall be free of any refuse, contam­ inants or other materials toxic to plant growth. Non-composted products will not be accepted. Test methods for the items below should follow US Composting Council Test Methods for the Examination of Composting and Compost guide­ lines for laboratory procedures: A. pH – 5.0-8.0 in accordance with TMECC 04.11-A, “Electrometric pH Determinations for Compost”. B. Particle size – 99% passing a 2-inch (50 mm) sieve and a maximum of 40% pass­ ing a 3/8-inch 9.5 mm) sieve, in ac­ cordance with TMECC 02.02-B, “Sample Sieving for Aggregate Size Classification”. (Note - In the field, product commonly is between ½ and 2 inches (12.5 and 50 mm) particle size). C. Moisture content of less than 60% in ac­ cordance with standardized test methods for moisture determination. D. Material shall be relatively free by dry weight) of inert or foreign manmade materials. E. Sock containment system for compost filter media shall be a photodegradable or biodegradable knitted mesh material and should have 1/8 to 3/8 inch (3.2 to 9.5 mm) openings. MAINTENANCE Periodic inspection and required maintenance must be provided. Sediment shall be removed when it reaches a depth of one-half the original dam height or before. If the area is to be mowed, check dams shall be removed once final stabi­ lization has occurred. Otherwise check dams may remain in place permanently. After removal, the area beneath the dam shall be seeded and mulched immediately. Cd-Fs ---PAGE BREAK--- 6-81 2016 Edition TO BE SHOWN ON THE EROSION AND SEDIMENT CONTROL PLAN 1.cfs in the channel/ditch that the check dam is being used 2. Above 2.0 cfs: 3. If Yes, list BMP being used in conjunction with check Figure 6-12.1 ---PAGE BREAK--- 6-82 2016 Edition Figure 6-12.2 ---PAGE BREAK--- 6-83 2016 Edition Figure 6-12.3 4. STRAW-BALE CHECK DAMS SHALL NOT BE USED WHERE THE DRAINAGE AREA EXCEEDS ONE ACRE. ---PAGE BREAK--- 6-84 2016 Edition ---PAGE BREAK--- 6-85 2016 Edition DEFINITION Improving, constructing or stabilizing an open channel for water conveyance. PURPOSE Open channels are constructed or stabilized to be non-erosive, with no sediment deposition and to provide adequate capacity for flood water, drainage, other water management practices, or any combination thereof. CONDITIONS This standard applies to the improvement, construction or stabilization of open channels and existing ditches with drainage areas less than one square mile. This standard applies only to channels conveying intermittent flow, not to channels conveying a continuous, live stream. An adequate outlet for the modified channel length must be available for discharge by gravity flow. Construction or other improvements of the channel should not adversely affect the environ­ mental integrity of the area and must not cause significant erosion upstream or flooding and/or sediment deposition DESIGN CRITERIA Planning The alignment and design of channels shall give careful consideration to the preservation of valuable fish and wildlife habitat and trees of significant value for wildlife food or shelter or for aesthetic purposes. Where channel construction will adversely af­ fect significant fish or wildlife habitat, mitigation measures should be included in the plan. Mitigation measures may include pools, riffles, flats, cascades or other similar provisions. As many trees as possible are to be left inside channel rights-of-way considering the requirements of construction, operation, and maintenance. Unusually large or attractive trees shall be pre­ served. Realignment The realignment of channels shall be kept to an absolute minimum and should be permitted only to correct an adverse environmental condi­ tion. Channel Capacity The capacity for open channels shall be de­ termined by procedures applicable to the pur­ poses to be served. Hydraulic Requirements Manning’s formula shall be used to determine velocities in channels. The values for use in this formula shall be estimated using currently accepted guides along with knowledge and experience regarding the conditions. Acceptable guides can be found in hydrology textbooks. Channel Cross-Section The required channel cross-section and grade are determined by the design capacity, the ma­ terials in which the channel is to be constructed, and the requirements for maintenance. A mini­ mum depth may be required to provide adequate outlets for subsurface drains and tributary chan­ nels. Channel Stability All channel construction, improvement and modification shall be in accordance with a design expected to result in a stable channel that can be maintained. Characteristics of a Stable Channel 1. Aggradation or degradation does not inter­ fere with the function of the channel or affect adjacent areas. Channel Stabilization Ch ---PAGE BREAK--- 6-86 2016 Edition 2. The channel banks do not erode to the extent that the channel cross-section is changed appreciably. 3. Excessive sediment bars do not develop. 4. Excessive erosion does not occur around culverts, bridges or elsewhere. 5. Gullies do not form or enlarge due to the entry of uncontrolled surface flow to the channel. 6. The determination of channel stability consid­ ers “bankfull” flow. Bankfull flow is defined as flow in the channel that creates a water surface that is at or near normal ground el­ evation for a significant length of a channel reach. Excessive channel depth created by cutting through high ground should not be considered in determinations of bankfull flow. CHANNEL LININGS AND STRUCTURAL MEASURES Where channel velocities exceed safe velocities for vegetated lining due to increased grade or a change in channel cross-section, or where dura­ bility of vegetative lining is adversely affected by seasonal changes, channel linings of rock, concrete or other durable material may be needed. Grade stabilization structures may also be needed. The following categories for flow velocities shall apply when selecting the channel lining: Category 1 (less than 5 ft/sec*) Vegetated Lining A vegetated lining may be used to stabilize chan­ nels with a velocity of less than five ft/s temporary erosion control blankets or sod shall be used on all channels and concentrated flow areas to aid in the establishment of the vegetated lining. Refer to specifications Ds3 - Disturbed Area Stabilization (With Permanent Vegetation), Ds4 - Disturbed Area Stabilization (With Sodding), and Ss – Slope Stabilization, Hydraulic Erosion Control Products (HECPs) are not intended to be applied in channels, swales or other areas where concen­ trated flows are anticipated, unless installed in conjunction with Rolled Erosion Control Products (RECPs). Category 2 (greater than or equal to 5 ft/sec* but less than 10 ft/sec*) Turf Reinforcement Matting Turf Reinforcement Matting (TRM) shall be used, if a vegetated lining is used in channels with velocities greater than or equal to 5 feet/ sec but less than 10 ft/sec. TRM is permanent erosion control matting that is used in channels to stabilize the soil while permanent vegetation is rooting, and to provide additional long-term protection. Velocities in channels when flowing at the bankfull discharge or the 25-year frequency discharge, whichever is the greater, shall be used in determining the appropriate TRM for stabilization of the channels. Rock Riprap Lining Rock riprap shall be designed to resist dis­ placement when the channel is flowing at the bankfull discharge or 25-year frequency dis­ charge, whichever is the greater. Rock riprap lining should be used when channel velocities are greater than or equal to 5 ft/sec but less than 10 ft/sec. Dumped and machine placed riprap should not be installed on slopes steeper than 1-1/2 horizontal to 1 vertical. Rock shall be dense, resistant to the action of air and water, and suitable in all other respects for the purpose intended. Rock shall be installed according to standards specified in Riprap, Appendix C. A filter blanket layer consisting of an appropri­ ately designed graded filter sand and/or gravel or geotextile material shall be placed between the riprap and base material. The gradation of the filter blanket material shall be designed to create a graded filter between the base material and the riprap. A geotextile can be used as a substitu­ tion for a layer of sand in a graded filter or as the filter blanket. Criteria for selecting an appropriate geotextile and guidance for recommended drop heights and stone weights are found in AASH-TO M288-96 Section 7.5, Permanent Erosion Control Specifications. Ch-1 Ch-2 ---PAGE BREAK--- 6-87 2016 Edition Category 3 (greater than or equal to 10 ft/sec*) Concrete Lining If a channel has velocities high enough to re­ quire a concrete lining (when channel velocities exceed 10 ft/sec), methods should be utilized to reduce the velocity of the runoff and reduce ero­ sion at the outlet - a common problem created by the smooth, concrete lining. Refer to specifi­ cation St - Storm Drain Outlet Protection for information regarding energy dissipators. If a concrete lining is chosen, it shall be designed according to currently accepted guides for struc­ tural and hydraulic adequacy. It must be designed to carry the required discharge and to withstand the loading imposed by site conditions. A separation geotextile should be placed under concrete linings to prevent undermining in the event of stress cracks due to settlement of the base material. The separation geotextile will keep the base material soils in place and mini­ mize the likelihood of a system failure. Grade Stabilization Structures Grade stabilization structures are used to reduce or prevent excessive erosion by reduc­ tion of velocities in the watercourse or by pro­ viding structures that can withstand and reduce the higher velocities. They may be constructed of concrete, rock, masonry, steel, aluminum, or treated wood. These structures are constructed where the capability of earth and vegetative measures is exceeded in the safe handling of water at permis­ sible velocities, where excessive grades or overall conditions are encountered or where water is to be lowered structurally from one elevation to another. These structures should generally be planned and installed along with or as a part of other erosion control practices. The structures shall be designed hydraulically to adequately carry the channel discharge and struc­ turally to withstand loadings imposed by the site conditions. The structure shall meet requirements of Gr - Grade Stabilization Structure. * The equivalent shear stress may also be used to determine the appropriate measure. TO BE SHOWN ON THE EROSION AND SEDIMENT CONTROL PLAN 1. The velocity in the channel, in ft/sec, for when the channel is flowing at the bank-full discharge or 25-year frequency discharge, whichever is the greater. 2. The type of lining to be used to stabilize the channel, i.e. vegetation (Ch-1): indicate type of veg­ etation and matting or blanket to be used), riprap (Ch-2): indicate average stone size), or concrete (Ch-3). Ch-3 ---PAGE BREAK--- 6-88 2016 Edition ---PAGE BREAK--- 6-89 2016 Edition DEFINITION A stone stabilized pad located at any point where traffic will be leaving a construction site to a public right-of-way, street, alley, sidewalk or parking area or any other area where there is a transition from bare soil to a paved area. PURPOSE To reduce or eliminate the transport of mud from the construction area onto public rights-of- way by motor vehicles or by runoff. CONDITIONS This practice is applied at appropriate points of construction egress. Geotextile underliners are required to stabilize and support the pad aggre­ gates. DESIGN CRITERIA Formal design is not required. The following standards shall be used: Aggregate Size Stone will be in accordance with National Stone Association R-2 (1.5 to 3.5 inch stone). Pad Thickness The gravel pad shall have a minimum thickness of 6 inches. Pad Width At a minimum, the width should equal full width of all points of vehicular egress, but not less than 20 feet wide. Pad Length The gravel pad shall have a minimum length of 50 feet. When the construction is less than 50’ from the paved access, the length shall be from the edge of existing pavement to the permitted building being constructed. Washing If the action of the vehicle traveling over the gravel pad does not sufficiently remove the mud, the tires should be washed prior to entrance onto public rights-of-way. When washing is required, it shall be done on an area stabilized with crushed stone and provisions that intercept the sediment- laden runoff and direct it into an approved sedi­ ment trap or sediment basin. Location The exit shall be located or protected to pre­ vent sediment from leaving the site. CONSTRUCTION SPECIFICATIONS It is recommended that the egress area be excavated to a depth of 3 inches and be cleared of all vegetation and roots. Diversion Ridge On sites where the grade toward the paved area is greater than a diversion ridge 6 to 8 inches high with 3:1 side slopes shall be con­ structed across the foundation approximately 15 feet above the road. Geotextile The geotextile underliner must be placed the full length and width of the entrance. Geotextile selection shall be based on AASHTO M288-06 specification: 1. For subgrades with a CBR greater than or equal to 3 or shear strength greater than 90 kPa, geotextile must meet requirements of section AASHTO M288-06 Section 7.3, Separation Requirements. 2. For subgrades with a CBR between 1 and 3 or sheer strength between 30 and 90 kPa, geotextile must meet requirements of section AASHTO M288-06 Section 8, Geotextile Property Requirements for Sub­ surface Drainage, Separation, Stabilization, and Permanent Erosion Control (Geotextile Property Requirements).. Construction Exit Co ---PAGE BREAK--- 6-90 2016 Edition MAINTENANCE The exit shall be maintained in a condition that will prevent tracking or flow of mud onto pub­ lic rights-of-way. This may require periodic top dressing with 1.5-3.5 inch stone, as conditions demand, and repair and/or cleanout of any structures to trap sediment. All materials spilled, Figure 6-14.1 dropped, washed, or tracked from vehicles or site onto roadways or into storm drains must be removed immediately. ---PAGE BREAK--- 6-91 2016 Edition DEFINITION A travelway constructed as part of a construc­ tion plan including access roads, subdivision roads, parking areas, and other on-site vehicle transportation routes. PURPOSE To provide a fixed travel route for construc­ tion traffic and reduce erosion and subsequent regrading of permanent roadbeds between time of initial grading and final stabilization. CONDITIONS This practice is applicable where travelways are needed in a planned land use area or wher­ ever stone-base roads or parking areas are constructed, whether permanent or temporary, for use by construction traffic. PLANNING CONSIDERATIONS Areas graded for construction vehicle trans­ port and parking purposes are especially suscep­ tible to erosion. The exposed soil is continuously disturbed, eliminating the possibility of stabiliza­ tion with vegetation. The prolonged exposure of the roads and parking areas to surface runoff can create severe rilling and muddying of the areas, requiring regrading before paving. The soil removed during this process may enter streams and other waters of the state via storm­ water management systems, compromising the water quality. Also, because the roads become so unstable during wet weather, they are virtually unusable, limiting access, and causing delays in construction. DESIGN CRITERIA Temporary Roads and Parking Areas The type of vehicle or equipment, speed, loads, climatic, and other conditions under which vehicles and equipment are expected to operate shall be considered. Location Temporary roads shall be located to serve the purpose intended, facilitate the control and disposal of water, control or reduce erosion, and make the best use of topographic features. Temporary roads shall follow the contour of the natural terrain to minimize disturbance of drainage patterns. If a temporary road must cross a stream, the crossing must be designed, installed and main­ tained according to specification Sr - Temporary Stream Crossing. Temporary parking areas should be located on naturally flat areas to minimize grading. Grade and Alignment The gradient and vertical and horizontal align­ ment shall be adapted to the intensity of use, mode of travel, and level of development. Grades for temporary roads should not exceed 10 percent except for very short (200 feet or less), but maximum grades of 20 percent or more may be used if necessary for special uses. Frequent grade changes generally cause fewer erosion problems than long continuous gradients. Curves and switchbacks must be of sufficient radius for trucks and other large vehicles to negoti­ ate easily. On temporary roads, the radius should be no less than 35 feet for standard vehicles and 50 feet for tractor-trailers. Grades for temporary parking areas should be sufficient to provide drainage but should not exceed 4 percent. Width Temporary roadbeds shall be at least 14 feet wide for one-way traffic and 20 feet wide for two- way traffic. The width for two-way traffic shall be increased approximately 4 feet for trailer traffic. A minimum shoulder width shall be 2 feet on each side. Where turnouts are used, road width shall be increased to a minimum of 20 feet for a Construction Road Stabilization Cr ---PAGE BREAK--- 6-92 2016 Edition distance of 30 feet. Side Slopes All cuts and fills shall have side slopes de­ signed to be stable for the particular site condi­ tions and soil materials involved. All cut and fills shall be 2:1 or flatter to the extent possible. When maintenance by machine mowing is planned, side slopes shall be no steeper than 3:1. Drainage The type of drainage structure used will depend on the type of enterprise and runoff conditions. The capacity and design shall be consistent with sound engineering principles and shall be adequate for the class of vehicle, type of road, development, or use. Structures should be designed to withstand flows from a 25-year, 24-hour frequency storm or the storm specified in Title 12-7-1 of the Official Code of Georgia Annotated. Channels shall be designed to be on stable grades or protected with structures or lin­ ings for stability. Water breaks or bars may be used to control surface runoff on low-intensity use roads. Stabilization Geotextile should be applied to the roadbed for additional stability. Geotextile selection shall be based on AASHTO M288-06 specification: 1. For subgrades with a CBR greater than or equal to 3 or shear strength greater than 90 kPa, geotextile must meet requirements of section AASHTO M288-06 Section 7.3, Separation Requirements. 2. For subgrades with a CBR between 1 and 3 or sheer strength between 30 and 90 kPa, geotextile must meet requirements of sec­ tion AASHTO M288-06 Section 8, Geotextile Property Requirements. A 6-inch course of coarse aggregate shall be applied immediately after grading or the comple­ tion of utility installation within the right-of-way. In areas experiencing “heavy duty” traffic situations, stone should be placed at an 8 to 10 inch depth to avoid excessive dissipation or maintenance needs. All roadside ditches, cuts, fills, and disturbed areas adjacent to parking areas and roads shall be stabilized with appropriate temporary or perma­ nent vegetation according to specification in Ds2 - Disturbed Area Stabilization (With Temporary Seeding) and Ds3 -Disturbed Area Stabilization (With Permanent Vegetation). PERMANENT ROADS AND PARKING AREAS Permanent roads and parking areas shall be designed and constructed according to criteria established by the Georgia Department of Trans­ portation or local authority. Permanent roads and parking areas shall be stabilized in accordance with this specification, applying an initial base course of gravel immediately following grading. CONSTRUCTION SPECIFICATIONS 1. Trees, stumps, roots, brush, weeds, and other objectionable materials shall be removed from the work area. 2. Unsuitable material shall be removed from the roadbed and parking areas. 3. Grading, subgrade preparation, and compac­ tion shall be done as needed. Fill material shall be deposited in layers not to exceed 9 inches and compacted with the controlled movement of compacting and earth moving equipment. 4. The roadbed and parking area shall be graded to the required elevation. Subgrade preparation and placement of the surface course shall be in accordance with sound highway construction practice. 5. Structures such as culverts, pipe drops, or bridges shall be installed to the lines and grades shown on the plans or as staked in the field. Pipe conduits shall be placed on a firm foundation. Selected backfill material shall be placed around the conduit in layers not to exceed 6 inches. Each layer shall be properly compacted. 6. Roads shall be planned and laid out ac­ cording to good landscape management principles. ---PAGE BREAK--- 6-93 2016 Edition MAINTENANCE Roads and parking areas may require a periodic top dressing of gravel to maintain the gravel depth at 6 inches. Vegetated areas should be checked periodically to ensure a good stand of vegetation is maintained. Remove any silt or other debris causing clogging of roadside ditches or other drainage structure. ---PAGE BREAK--- 6-94 2016 Edition ---PAGE BREAK--- 6-95 2016 Edition DEFINITION A temporary channel constructed to convey flow around a construction site while a perma­ nent structure is being constructed in the stream channel. PURPOSE To protect the streambed from erosion and allow work “in the dry”. CONDITIONS Temporary stream diversion channels shall be used only on flowing streams with a drain­ age area less than one square mile. Structures or methodology for crossing streams with larger drainage areas should be designed by methods that more accurately define the actual hydrologic and hydraulic parameters that will affect the functioning of the structure. A Stream Buffer Vari­ ance from the GA EPD may be required, unless specifically exempt from the Act and all other appropriate agencies, including the U.S. Army Corps of Engineers, must be contacted to ensure compliance with other laws. PLANNING CONSIDERATIONS Linear projects, such as utilities or roads, frequently cross and impact live streams creat­ ing a potential for excessive sediment loss into a stream by both the disturbance of the approach areas and by the work within the streambed and banks. In cases where in-stream work is unavoidable, the amount of encroachment and time spent working in the channel shall be minimized. If con­ struction in the streambed will take an extended period of time, substantial in-stream controls or stream diversion channel should be considered to prevent excessive sedimentation damage. To limit land-disturbance, overland pumping of the stream should be considered in low-flow conditions. Clear­ ing of the streambed and banks shall be kept to a minimum. DESIGN CRITERIA Drainage Area Temporary stream diversion channels shall should not be used on streams with drainage areas greater than one square mile. Size The bottom width of the stream diversion shall be a minimum of six feet or equal to the bottom width of the existing streambed, whichever is greater. Stream Diversion Channel Dc Table 6-16.1. STREAM DIVERSION CHANNEL LININGS Lining Materials Symbol Acceptable Velocity Range Geotextile, polyethylene film,or sod 0 -2.5 fps Geotextile alone 2.5 -9.0 fps Class I riprap and geotextile 9.0 -13.0 fps Dc-B Dc-A Dc-C ---PAGE BREAK--- 6-96 2016 Edition Side Slopes Side slopes of the stream diversion channel shall be no steeper than 2:1. Depth and Grade Depth and grade may be variable, dependent on site conditions, but shall be sufficient to en­ sure continuous flow of water in the diversion. Channel Lining A stream diversion channel shall be lined to prevent erosion of the channel and sedimenta­ tion in the stream. The lining is selected based upon the expected velocity of bankfull flow. Table 6-16.1 shows the selection of channel linings that may be used. Refer to specification Ss- Slope Stablization. Geotextile Geotextiles should be used as a protective cover for soil or, if the channel is to be lined with rip-rap, as a separator between graded stone and the soil base. The geotextile will prevent ero­ sion of the channel and the migration of soil par­ ticles from the subgrade into the graded stone. The geotextile shall be specified in accordance with AASHTO M288-06 Section 8, Geotextile Property Requirements. The geotextile should be placed immediately adjacent to the subgrade without any voids. CONSTRUCTION SPECIFICATIONS 1. The channel shall be excavated, constructing plugs at both ends. Plugs can be constructed of compacted soil, riprap, sandbags or sheet piling. 2. Sediment barrier or a berm shall be placed along the sides of the channel to prevent un­ filtered runoff from entering the stream. The berm can be constructed using the material excavated for the stream diversion. 3. The channel surface shall be smooth (to prevent tearing of the liner) and lined with the material specified in the plans. The outer edges of the geotextile shall be secured at the top of the channel with compacted soil. 4. The plugs are removed when the liner instal­ lation is complete, removing the plug first. 5. As soon as construction in the streambed is complete, the diversion shall be replugged and backfilled. The liner should be inspected for damage and salvaged if possible. 6. Upon removal of the lining, the stream shall immediately be restored and properly stabi­ lized. MAINTENANCE The stream diversion channel shall be in­ spected at the end of each day to make sure that the construction materials are positioned secure­ ly. This will ensure that the work area stays dry and that no construction materials float down­ stream. All repairs shall be made immediately. ---PAGE BREAK--- 6-97 2016 Edition Figure 6-16.1. Stream Diversion Channel (perspective view) ---PAGE BREAK--- 6-98 2016 Edition Figure 6-16.2. Stream Diversion Channel Linings ---PAGE BREAK--- 6-99 2016 Edition DEFINITION A ridge of compacted soil, constructed above, across or below a slope. PURPOSE To reduce the erosion of steep, or otherwise highly erodible areas by reducing slope intercepting storm runoff and diverting it to a stable outlet at a non-erosive velocity. CONDITIONS Diversions are applicable when: 1. Runoff from higher areas is or has potential for damaging property, causing erosion, con­ tributing to pollution, flooding, interfering with or preventing the establishment of vegetation on lower areas. 2. Surface and/or shallow subsurface flow is damaging sloping upland. 3. The length of slope needs to be reduced so that soil loss will be reduced to a minimum. This standard applies to temporary and perma­ nent diversions in developments involving land- disturbing activities. DESIGN CRITERIA Location Diversion location shall be determined by considering outlet conditions, topography, land use, soil type, length of slope, seep planes (when seepage is a problem), and the develop­ ment layout. Diversions should be tailored to fit the conditions for a particular field and local soil type(s). A diversion consists of two components that must be designed - the ridge and the channel. Ridge Design The ridge shall be compacted and designed to have stable side slopes, which shall not be steeper than 2:1. The ridge shall be a minimum width of four feet at the design water elevation after settlement. Its design shall allow ten per­ cent for settlement. Channel Design Land slope must be taken into consideration when choosing channel dimensions. On the steeper slopes, narrow and deep channels may be required. On the more gentle slopes, broad, shallow channels usually are applicable. The wide, shallow section will be easier to maintain. Since sediment deposition is often a problem in diversions, the designed flow velocity should be kept as high as the channel lining will permit. Table 6-17.1 indicates the storm frequency required for the design of the diversion. The re­ quired storm frequency is based on the purpose of the diversion. The storm frequency is used to determine the required channel capacity, Q (peak rate of runoff). The channel portion of the diversion may have a parabolic or trapezoidal cross-section. Detailed information for the design of these channels is provided in the specification Wt - Stormwater Conveyance Channel. Outlets Each diversion must have an adequate outlet. The outlet may be a constructed or natu­ ral waterway, a stabilized vegetated area or a stabilized open channel. In all cases, the outlet must discharge in such a manner as to not cause an erosion problem. Protected outlets shall be constructed and stabilized prior to construction of the diversion. Stabilization Channels shall be stabilized in accordance with item 5 of the construction specifications. Diversions For Roads and Utility Rights - of Way A detailed design is not required for this type of diversion. Diversions installed to divert water Diversion Di ---PAGE BREAK--- 6-100 2016 Edition off a road or right-of-way shall consist of a series of compacted ridges of soil running diagonally across the road at a 30° angle. Ridges are con­ structed by excavating a channel up-stream for this type of diversion. The compacted ridge height shall be 8-12” above the original road surface; the channel depth shall be 8-12” below the original road surface. Channel bottoms and ridge tops shall be smooth enough to be crossed by vehicular traffic. The maximum spac­ ing between diversions shall be as follows: Stable outlets shall be provided for each diversion. CONSTRUCTION SPECIFICATIONS 1. All trees, brush, stumps, obstructions, and other objectionable material shall be re­ moved and disposed of so as not to interfere with the proper functioning of the diversion. 2. The diversion shall be excavated or shaped to line, grade, and cross section as required to meet the criteria specified herein and free of irregularities that will impede normal flow. 3. All fills shall be machine compacted as needed to prevent unequal settlement that would cause damage in the completed diversion. 4. All earth removed and not needed in construction shall be spread or disposed of so that it will not interfere with the functioning of the diversion. 5. Diversion channel shall be stabilized in accordance with specification Ch - Channel Stabilization. Figure 6-17.1 Road Grade (Percent) Distance Between Diversions (Feet) 1 2 5 10 15 20 400 250 125 80 60 50 ---PAGE BREAK--- 6-101 2016 Edition Table 6-17.1. Diversion Design Criteria Diversion Type Land or Improvement Protected Storm Frequency1 Freeboard Minimum Top Width Temporary Construction areas Building sites 10 yrs2 0.3’ 4’ Permanent Landscaped, recreation and similar areas. 25 yrs 0.3’ 4 ‘ Dwellings, schools, commercial and similar installations 50 yrs 0.5’ 4‘ 1 Use 24-hr storm duration 2 Use 10 yrs or the storm for the storm frequency specified in Title 12 of the Official Code of Georgia Annotated ---PAGE BREAK--- 6-102 2016 Edition WIDTH DRAWING FLOW = FT WIDTH WIDTH Figure 6-17.2 ---PAGE BREAK--- 6-103 2016 Edition DEFINITION A temporary structure used to convey con­ centrated storm water down the face of cut or fill slopes. PURPOSE To safely conduct storm runoff from one el­ evation to another without causing slope erosion and allowing the establishment of vegetation on the slope. CONDITIONS Temporary downdrains are used on slopes where a concentration of storm water could cause erosion damage. These structures are removed once the permanent stormwater disposal system is installed. DESIGN CRITERIA Formal design is not required. The following standards shall be used: Placement The temporary downdrain shall be located on undisturbed soil or well-compacted fill. Diameter The diameter of the temporary downdrain shall provide sufficient capacity required to con­ vey the maximum runoff expected during the life of the drain. Refer to Table 6-18.1 for selecting pipe sizes. Downdrain Inlet and Outlet Diversions are used to route runoff to the downdrain’s Tee or inlet at the top of the slope. Slope the entrance 1/2” per foot toward the outlet. Thoroughly compact selected soil around the inlet section to prevent the pipe from being washed out by seepage or piping. A stone filter ring or check dam may be placed at the inlet for added sediment filtering capacity. Refer to Cd - Check Dam and Fr - Stone Filter Ring. These sediment filtering devices should be removed if flooding or bank overwash occurs. Rock riprap shall be placed at the outlet for en­ ergy dissipation. A Tee outlet, flared end section, or other suitable device may be used in conjunction with the riprap for additional protection. See Figure 6-18.1. Refer to specification St - Storm Drain Outlet Protection. Pipe Material Design the slope drain using heavy-duty, flex­ ible materials such as non-perforated, corrugated plastic pipe or specially designed flexible tubing. Use reinforced, hold-down grommets or stakes to anchor the pipe at intervals not to exceed 10 feet with the outlet end securely fastened in place. The pipe must extend beyond the toe of the slope. CONSTRUCTION SPECIFICATIONS A common failure of slope drains is caused by water saturating the soil and seeping along the pipe. This creates voids from consolidation and causes washouts. Proper back-filling around and under the pipe “haunches” with stable soil mate­ rial and hand compacting in 6-inch lifts to achieve firm contact between the pipe and the soil at all points will eliminate this type of failure. 1. Place slope drains on undisturbed soil or well-compacted fill at locations and eleva­ tions shown on the plan. 2. slope the section of pipe under the dike toward its outlet. Temporary Downdrain Structure Table 6-18.1. Pipe Diameter for Temporary Downdrain Structure Maximum Drainage Area Pipe Diameter Per Pipe (acre) (inches) 0.3 10 0.5 12 1.0 18 Dn1 ---PAGE BREAK--- 6-104 2016 Edition 3. Hand tamp the soil under and around the en­ trance section in lifts not to exceed 6 inches. 4. Ensure that fill over the drain at the top of the slope has minimum dimensions of 1.5 ft. depth, 4 ft. top width, and 3:1 side slopes. 5. Ensure that all slope drain connections are watertight. 6. Ensure that all fill material is well-compacted. Securely fasten the exposed section of the drain with grommets or stakes spaced no more than 10 feet apart. 7. For slopes steeper than 2:1, slope drains should be placed diagonally across the slope, extending the drain beyond the toe of the slope. Curve the outlet uphill and ad­ equately protect the outlet from erosion. 8. If the drain is conveying sediment-laden runoff, direct all flows into a sediment trap or sediment basin. 9. Make the settled, compacted dike ridge no less than one foot above the top of the pipe at every point. 10. Immediately stabilize all disturbed areas fol­ lowing construction. MAINTENANCE Inspect the slope drain and supporting di­ version after every rainfall and make necessary repairs. When the protected area has been permanently stabilized and the permanent stormwater disposal system is fully functional, temporary measures may be removed, materials disposed of properly, and all disturbed areas sta­ bilized appropriately. Refer to specifications Ds3 and Ds4 - Disturbed Area Stabilization (With Permanent Vegetation and Sodding), respec­ tively, and Ss - Slope Stabilization. TO BE SHOWN ON THE EROSION AND SEDIMENT CONTROL PLAN 1. The drainage area for each downdrain, in acres. 2. The diameter of each downdrain, in inches, based on Table 6-18.1. 3. The dimensions of the outlet protection, including flow rate, velocity, and apron length, upstream and widths, average stone diameter and depth. ---PAGE BREAK--- 6-105 2016 Edition Figure 6-18.1 ---PAGE BREAK--- 6-106 2016 Edition ---PAGE BREAK--- 6-107 2016 Edition DEFINITION A permanent structure to safely convey sur­ face runoff from the top of a slope to the bottom of the slope. PURPOSE The purpose of this standard is to convey storm runoff safely down cut or fill slopes to mini­ mize erosion. CONDITIONS Several types of structures may be used as a permanent downdrain. All structures shall satisfy the standards and specification set forth by the Georgia Department of Transportation. The fol­ lowing types of structures may be used: Paved Flume The paved flume may have a parabolic, rect­ angular or trapezoidal cross-section. Pipe The pipe may be constructed of materials including steel, plastic, etc. Sectional A prefabricated sectional conduit of half round or third round pipe may be used. Downdrain structures are to be used where concentrated water will cause excessive erosion on cut and fill slopes. DESIGN CRITERIA Permanent downdrain structures should be designed by professionals familiar with these structures. Capacity Flumes shall be adequately designed to safely convey runoff water concentrations down steep slopes based on a minimum 25-year, 24-hour storm in accordance with criteria in Appendix A of this Manual. Slope The slope shall be sufficient to prevent the deposition of sediment. Outlet Stabilization Outlets must be stabilized using criteria in St - Storm Drain Outlet Protection. MAINTENANCE Inspect for damage after each rainfall. Permanent Downdrain Structure Dn2 ---PAGE BREAK--- 6-108 2016 Edition ---PAGE BREAK--- 6-109 2016 Edition DEFINITION A temporary stone barrier constructed at storm drain inlets and pond outlets. PURPOSE This structure reduces flow velocities, pre­ venting the failure of other sediment control de­ vices. It also helps prevent sediment from leav­ ing the site or entering drainage systems, prior to permanent stabilization of the disturbed area. CONDITIONS Filter rings shall be used in conjunction with other sediment control measures, except where other practices defined in this Manual are not appropriate (such as inlets to concrete flumes). They can be installed at or around devices such as inlet sediment traps, temporary downdrain inlets, and detention pond retrofits to provide additional sediment filtering capacity. DESIGN CRITERIA Formal design is not required. The following standards shall be used: Location The filter ring shall surround all sides of the structure receiving runoff from disturbed areas. It should be placed a minimum of four feet from the structure. The ring is not intended to substantially impound water, causing flooding or damage to adjacent areas. The filter ring may also be placed below storm drains discharging into detention ponds, creating a centralized area, or “forebay”, for sediment ac­ cumulation. This provides for easier, more localized clean-out of the pond. If utilized above a retrofit structure, it should be a minimum of 8 to 10 feet from the retrofit. Stone Size When utilized at inlets with diameters less than 12 inches, the filter ring shall be constructed of stone no smaller than 3-5 inches (15 - 30 lbs.). When utilized at pipes with diameters greater than 12 inches, the filter ring shall be constructed of stone no smaller than 10-15 inches (50 - 100 lbs.). The larger stone can be faced with smaller filter stone on the upstream side for added sediment filtering capabilities. However, the smaller filter stone is more prone to clogging, requiring higher maintenance. Height The filter ring shall be constructed at a height no less than two feet from grade. CONSTRUCTION SPECIFICATIONS Mechanical or hand placement of stone shall be required to uniformly surround the structure to be supplemented. Refer to Appendix C for rock riprap specifications. The filter ring may be constructed on natural ground surface, on an excavated surface, or on machine compacted fill. A common failure of a filter ring is caused by placing it too close to or too high above the struc­ ture it is enhancing. When utilized below a storm drain outlet, it shall be placed such that it does not create a condition causing water to back-up into the storm drain and inhibit the function of the storm drain system. MAINTENANCE The filter ring must be kept clear of trash and debris. This will require continuous monitor­ ing and maintenance, which includes sediment removal when one-half full. Structures are tem­ porary and should be removed when the land- disturbing project has been stabilized. Filter Ring Fr ---PAGE BREAK--- 6-110 2016 Edition Figure 6-20.1 ---PAGE BREAK--- 6-111 2016 Edition DEFINITION Gabions are large, multi-celled, welded wire or rectangular wire mesh boxes, used in channel revetments, retaining walls, abutments, check dams, etc. PURPOSE Rock-filled baskets, properly wired together, form flexible monolithic building blocks used for construction of erosion control structures. Gabi­ ons are used to stabilize steep or highly erosive slopes. DESIGN CRITERIA Construction plans and drawings should be prepared by professionals familiar with the use of gabions. Erosion and sediment control con­ struction design should ensure that foundations are properly prepared to receive gabions, that the gabion structure is securely “keyed” into the foundations and abutment surfaces, and that rock used is durable and adequately sized to be retained in the baskets. CONSTRUCTION SPECIFICATIONS How the Gabion is Filled The gabion is usually filled with 4 - 8 inch pieces of stone, preferably placed by hand, but sometimes dumped mechanically, into the bas­ ket. Hand-packing allows the complete filling of the basket; allowing the basket to gain strength and maintain its integrity. The filled gabion then becomes a large, flexible, and permeable build­ ing block from which a broad range of structures may be built. This is done by setting and wiring individual units together in courses and filling them in place. Details are provided by the manu­ facturer. Geotextiles It is recommended that geotextiles be used behind all gabion structures. Geotextiles shall be specified in accordance with AASHTO M288-06 Section 8, Geotextile Property Requirements. If there is seepage flow or unidirectional flow from the protected soil mass, the appropriate geo­ textile should be selected based on an appropriate filter design to prevent the build-up of hydrostatic pressure behind the geotextile. Corrosion Resistance of Gabions The wire mesh or welded wire used in gabi­ ons is heavily galvanized. For highly corrosive conditions, a PVC (polyvinyl chloride) coating must be used over the galvanizing. Such treat­ ment is an economical solution to deterioration of the wire near the ocean, in some industrial areas, in polluted streams, and in soils such as muck and peat. However, extra care should be taken during construction and installation be­ cause the corrosion resistance of the baskets is compromised if the PVC coating is chipped-off. Also, baskets manufactured completely of plastic are available. Flexibility An outstanding advantage of the gabion is its flexibility of application. This property is espe­ cially important when a structure is on unstable ground or in areas where scour from waves or currents can undermine it. Durability Gabions are durable because they support plant growth that develops a living coating for the wire mesh and stones. After the first few years, the strength of the structure may be enhanced by the soil, silt, and roots that fill the voids between the individual stones. Strength Steel wire baskets have the strength and flex­ ibility to withstand forces generated by water and earth masses. Also, the pervious nature of the gabion allows it to absorb and dissipate much of the energy developed. This is particularly so on coast protection installations where a compact gabion structure often remains long after a mas­ sive rigid structure fails. Gabion Ga ---PAGE BREAK--- 6-112 2016 Edition Permeability Hydrostatic heads do not develop behind a gabion wall. The wall is pervious to water and stabilizes a slope by the combined action of draining and retaining. Drainage is accomplished by gravity and by evaporation as the porous structure permits active air circulation through it. Moreover, as plant growth invades the structure, transpiration further assists in removing moisture from the backfill. This system is much more effi­ cient than weep holes in standard masonry walls. Economy Gabion installations are more economical than rigid or semi-rigid structures for a number of reasons. The following are among the more important ones. • Little maintenance is required. • Gabion construction is simple and does not require skilled labor. • Preliminary foundation preparation is un­ necessary; the surface needs only to be reasonably level and smooth. • No costly drainage provision is required because of the gabion’s porosity. Landscaping Because gabions permit the growth of natural vegetation and maintain the natural environment of the area, they provide attractive and natural building blocks for decorative landscaping. They can be used effectively and economically in parks, along highways, including use as a sound barrier, and around bridge approaches to create walkways, rock gardens, patios, and terraces, to beautify the banks of lakes and ponds, to accent trees and other plantings. In fact, their application to decorative landscap­ ing is limited only by the ingenuity of the landscaper. Typical Installations •Flood control: Gabion aprons Counterforts Longitudinal works Training walls Drop structures or weirs Revetments Spurs, spur dikes, or groins Bank paving •Channel linings •Retaining walls •Bridge abutments and wings •Marinas and boat ramps •Culvert headwalls and outlet aprons •Shore and beach protection MAINTENANCE Periodic inspection should be performed for signs of undercutting or excessive erosion at transition areas. Source: National Crushed Stone Association ---PAGE BREAK--- 6-113 2016 Edition DEFINITION A structure to stabilize the grade in natural or artificial channels. PURPOSE Grade stabilization structures are installed to stabilize the grade in natural or artificial chan­ nels, prevent the formation or advance of gullies, and reduce erosion and sediment pollution. CONDITIONS This standard applies to sites where struc­ tures are needed to stabilize channel grades but does not apply to sites where water is to be impounded. DESIGN CRITERIA Structures Structures constructed of concrete, rock, masonry, steel, aluminum or treated wood or by soil bioengineering methods shall be designed in accordance with sound engineering practices. Design data for small reinforced concrete drop spillways and formless concrete chute spillways are contained herein. Geotextile should be placed under stabilization structures such as revetment mats and riprap as part of a permanent erosion control system. The geotextile should be selected/specified in accor­ dance with AASHTO M288-06 Section 8, Geotextile Property Requirements. Capacity The condition of adjacent areas is considered when determining the storm frequency used to design the grade stabilization structure. Struc­ tures shall be designed to protect areas from overbank flow damage up to and including storm frequencies specified in Table 6-22.1. Grade Stabilization Structure Embankment Earthfill embankments shall have a minimum top width of 10 feet and side slopes of 3:1 or flatter. Keyway A keyway no less than 8 feet wide and 2 feet deep shall be constructed along the centerline of the structure and embankment. Outlet All structures shall discharge into stable outlets. CONSTRUCTION SPECIFICATIONS Excavations shall be dewatered prior to filling. Structures shall be placed on compacted earth­ fill. Earthfill material shall be moderately to slowly permeable with the most plastic being used in the center of the embankment and adjacent to struc­ tures. Materials shall be constructed in 6 - 8 inch horizontal lifts and compacted to approximately 95% of standard density. The embankment shall be overbuilt 10% in height to allow for settlement. Embankment surfaces shall be completed to the required lines and grades. Protective cover shall be applied immediately Gr Table 6-22.1 Adjacent Area Storm Frequency Residences, commercial buildings, recreational buildings, etc. 100 - year, 24 - hour storm Recreation and landscaped areas 25 - year2, 24 - hour storm1 Agricultural land 25 - year2, 24 - hour storm1 1 50 percent of peak flood flow may be carried around island-type structures provided overbank flow damage from erosion and flooding can be tolerated. Peak flood flow will be determined by methods contained in Appendix A. 2 Or the storm frequency specified in Title 12 of the Official Code of Georgia Annotated. ---PAGE BREAK--- 6-114 2016 Edition after completion of the structure. Refer to specifi­ cations Ds3 and Ds4 - Disturbed Area Stabiliza­ tion (With Permanent Vegetation and Sodding), respectively, and Ss - Slope Stabilization. Figure 6-22.1 Drop spillways or Drop spillways CONTROLLED HEAD (feet) Pipe drop inlet spillways Note: Chart shows most economical structure as related to discharge and controlled head providing site conditions are adequate. 10 4 8 12 16 20 25 30 40 80 25 50 100 150 200 [PHONE REDACTED] Hooded inlet spillways Hooded inlet or drop inlet Drop or chute Monolithic spillways spillways DISCHARGE (cfs) spillways Chute Pipe drop inlet spillways ---PAGE BREAK--- 6-115 2016 Edition Figure 6-22.2 Planning and design of straight drop spillways normally require the assistance of an engineer. Local personnel may be trained to plan and install small drop spillway structures when standard plans are available. Measurement locations for symbols F (overfall in feet), h (depth of weir in feet), s (depth of stilling pool in feet), and L (length of weir in feet) are shown in Figure 6-16.3 Figure 6-22.3 - Symbols For Straight Drop Spillway Weir capacities for low-overall straight drop spillways can be determined from figure 6-23.4 for various combinations of F, h, and L. ---PAGE BREAK--- 6-116 2016 Edition Figure 6-22.4 700 600 500 400 300 200 100 0 700 600 500 h=3'-0" h=3'-0" h=3'-6" h=4'-0" h=2'-6" h=2'-6" h=2'-0" h=2'-0" h=3'-0" h=3'-6" h=4'-0" h=4'-6" h=5'-0" h=2'-6" h=2'-0" h=3'-0" h=3'-6" h=4'-0" h=4'-6" h=5'-0" h=2'-6" h=2'-0" 400 300 200 100 0 700 800 900 600 500 400 300 200 100 0 700 800 900 600 500 400 300 200 100 0 6 8 10 12 14 Length of weir, L, in ft. Length of weir, L, in ft. F = 6 ft. F = 5 ft. F = 4 ft. F = 3 ft. Discharge capacity, Q, in cfs. Discharge capacity, Q, in cfs. Discharge capacity, Q, in cfs. Discharge capacity, Q, in cfs. 16 18 20 22 24 26 28 30 6 8 10 12 14 Length of weir, L, in ft. Note: h = total depth of weir, in feet (including freeboard) c = net drop from crest to top of transverse sill, in feet (For type B drops keep h F less than 0.75) 16 18 20 22 24 26 28 30 6 8 10 12 14 Length of weir, L, in ft. 16 18 20 22 24 26 28 30 6 8 10 12 14 16 18 20 22 24 26 28 30 WEIR CAPACITY FOR STRAIGHT DROP SPILLWAYS Q = (1.10 + 0.01 F) 3.1 L h 3 2 ---PAGE BREAK--- 6-117 2016 Edition Figure 6-22.5 Drop Inlet Spillway Figure 6-22.6 Box Drop Inlet Spillway ---PAGE BREAK--- 6-118 2016 Edition Figure 6-22.7 Chute Spillway ---PAGE BREAK--- 6-119 2016 Edition Figure 6-22.8 Typical Plan - Formless Concrete Chute ---PAGE BREAK--- 6-120 2016 Edition Figure 6-22.10 Sheet Piling Headwall with Sand -Cement Bag Sidewalls and Apron SMALL, LOW COST WATER CONTROL STRUCTURES Figure 6-22.9 Prefabricated Metal Structure ---PAGE BREAK--- 6-121 2016 Edition DEFINITION A storm flow outlet device constructed at zero grade across the slope whereby concentrated runoff may be discharged at non-erosive veloci­ ties onto undisturbed areas stabilized by existing vegetation. PURPOSE To dissipate storm flow energy at the outlet by converting storm runoff into sheet flow and to discharge it onto areas stabilized by existing vegetation without causing erosion. CONDITIONS Where sediment-free storm runoff is inter­ cepted and diverted onto undisturbed stabilized areas at diversion outlets, etc.). This prac­ tice applies only in those situations where the spreader can be constructed on undisturbed soil and where the area directly below the level lip is stabilized by existing vegetation. The water must not be allowed to reconcentrate below the point of discharge. DESIGN CRITERIA Length A specific design for level spreaders will not be required. However, spreader length will be de­ termined by estimating the peak stormflow from the 10-year, 24-hour storm or the storm specified in Title 12 of the Official Code of Georgia Anno­ tated and selecting the appropriate length from Table 6-23.1. Outlets Final discharge will be over the level lip onto an undisturbed, stabilized area. The outlet shall be generally smooth to create uniform sheet flow. CONSTRUCTION SPECIFICATIONS The minimum acceptable width shall be 6 feet. The depth of the level spreader as mea­ sured from the lip shall be at least 6 inches and the depth shall be uniform across the entire length of the measure. The grade of the channel for the last 15 feet of the dike or diversion entering the level spreader shall be less than or equal to The level lip shall be constructed on zero percent grade to insure uniform spreading of storm runoff (converting channel flow to sheet flow). For calcu­ lation purposes, a grade of 0.1% may be needed, however, the level spreader shall be installed at zero percent grade. Level spreaders must be constructed on undisturbed soil (not on fill). The entrance to spreader shall be graded in a manner to insure that runoff enters directly onto the zero percent graded channel. Storm runoff converted to sheet flow must dis­ charge onto undisturbed stabilized areas. All disturbed areas shall be vegetated imme­ diately after construction is completed. Refer to specifications Ds3 and Ds4 - Disturbed Area Sta­ bilization (With Permanent Vegetation and Sod­ ding), respectively and Ss - Slope Stabilization. MAINTENANCE Periodic inspection and maintenance must be provided. Level Spreader Table 6-23.1 Designed Q10/24 (cfs) Minimum Length (feet) up to 10 11 to 20 21 to 30 31 to 40 41 to 50 10 20 30 40 50 Lv ---PAGE BREAK--- 6-122 2016 Edition Figure 6-23.1 ---PAGE BREAK--- 6-123 2016 Edition DEFINITION A temporary stone filter dam installed across drainageways or in conjunction with a temporary sediment trap. PURPOSE This structure is installed to serve as a sedi­ ment filtering device in drainageways or outlets for sediment traps (See Temporary Sediment Trap - Sd4). In some cases, it may also reduce the velocity of stormwater flow through a chan­ nel. This structure is not intended to substantially impound water. CONDITIONS This practice is applicable for use in small channels that drain 50 acres or less. The rock filter dam must be used in conjunction with other appropriate sediment control measures to reduce the amount of sediment leaving the channel. DESIGN CRITERIA The following standards shall be followed: Drainage Area The drainage area to the dam shall not exceed 50 acres. Height The dam should not be higher than the chan­ nel banks or exceed the elevation of the up­ stream property line. The center of the rock dam should be at least nine inches lower than the outer edges of the dam at the channel banks. Side Slopes The side slopes shall be 2:1 or flatter. Location The dam shall be located as close to the source of sediment as possible and so that it will not cause water to back up on upstream adjacent property or into state waters. Stone Size The stone size shall be determined by the design criteria established in Riprap - Appendix C. The rock dam can be faced with smaller stone on the upstream side for additional filtering effect. However, this may make the dam more prone to clogging. Top Width The width accross the top of the dam should be no less than six feet. Geotextile Geotextiles should be used as a separator between the graded stone, the soil base, and the abutments. The geotextile will prevent the migra­ tion of soil particles from the subgrade into the graded stone. The geotextile shall be specified in accordance with AASHTO M288-06 Section 8, Geotextile Property Requirements. The geo­ textile should be placed immediately adjacent to the subgrade without any voids and extend five feet beyond the toe of the dam to prevent scour. CONSTRUCTION SPECIFICATIONS Mechanical or hand placement will be re­ quired to insure that the rock dam extends completely across the channel and securely ties into both channel banks. The center of the dam must be no less than nine inches lower than the lowest side, to serve as a type of weir. Gabions can be installed to serve as rock filter dams, but should follow recommended sizing and instal­ lation specifications. Refer to specification Ga - Gabion. See Figure 6-24.1 MAINTENANCE Rock dams should be removed once dis­ turbed areas have been stabilized. Periodic inspection and required maintenance must be provided. Sediment shall be removed when it reaches a depth of one-half of the original height of the dam. Rock Filter Dam Rd ---PAGE BREAK--- 6-124 2016 Edition TO BE SHOWN ON THE EROSION AND SEDIMENT CONTROL PLAN 1. Figure 6-24.1, noting rock size as specified in Appendix C. 2. Top and bottom widths. ---PAGE BREAK--- 6-125 2016 Edition Figure 6-24.1 ---PAGE BREAK--- 6-126 2016 Edition ---PAGE BREAK--- 6-127 2016 Edition DEFINITION A wall constructed of one or more of the fol­ lowing: concrete masonry, reinforced concrete cribbing, treated timbers, steel pilings, gabions, stone drywall, rock riprap, etc. PURPOSE To assist in the stabilization of cut or fill slopes where stable slopes are not attainable without the use of the wall. CONDITIONS Use in conjunction with cut or fill slopes that, because of space limitations or unstable mate­ rial, do not allow the stable slope criteria listed above, e.g. cuts into steep hillsides on small lots or cuts into hillsides behind shopping centers to provide loading space. DESIGN CRITERIA General The design of a retaining wall is a complicated process. Many factors must be taken into ac­ count such as: stresses and forces outside and within the wall, allowable height and minimum thickness. Other considerations are: foundation design with respect to loadings, bearing values of soils and footing dimensions. Additional design factors are safety hazards, subsurface and sur­ face drainage and appearance. Each situation requires a specific design that is within the capabilities of the design professional. Consideration should be given to all of the alter­ native methods with regard to construction of the wall. Some methods are: 1. Concrete masonry 2. Concrete cribbing 3. Gabions 4. Steel piling 5. Stone drywall 6. Rock riprap, etc. 7. Treated timbers 8. Geotextile wrapped-face wall 9. Geotextile reinforced steep slopes Retaining Wall Re ---PAGE BREAK--- 6-128 2016 Edition ---PAGE BREAK--- 6-129 2016 Edition DEFINITION A device or structure placed in front of a permanent stormwater detention pond outlet or roadway drainage structure to serve as a tempo­ rary sediment filter. PURPOSE Allows permanent stormwater detention basin structures to function as temporary sediment retention basins for land-disturbing projects, and allow roadway drainage to be used for temporary sediment storage. CONDITIONS This standard applies under the following conditions: 1. Shall not be used in basins on live streams or in basins with a total contributing drainage area of 100 acres or more. 2. Shall only be used in basins large enough to store 67 cubic yards of sediment per acre of disturbed area in the project. 3. Shall be considered a temporary structure and will be removed as soon as project is permanently stabilized. All accumulated sediment shall be removed, and the pond or basin shall be brought to final grade (if possible), prior to the removal of the retrofit. DESIGN CRITERIA 1. The height of the retrofit should be approxi­ mately one-half the height of the structure. 2. A retrofitted dention pond must be ca­ pable of storing the required volume of sediment in addition to the required stormwater volume. The required sedi­ ment storage volume shall be achieved by either excavating the basin or raising the outlet structure’s invert to achieve 67 cubic yards per acre of sediment storage. Remove sediment when one-third of the sediment storage capacity, not total pond capacity, is lost to sediment accumulation. This volume shall be marked on the riser or by setting a marked post near the riser. 3. For effective trapping efficiency, the sediment delivery inlets should be at the upper end of the basin. 4. For effective trapping efficiency, the length- width ratio of the basin shall be at least 2:1. If the length-width ratio is not at least 2:1, the flow length shall be increased with the use of baffles installed within the basin. CONSTRUCTION SPECIFICATIONS The following types of structures are accept­ able under the designated conditions: Perforated Half-Round Pipe with Stone Filter (See Figure 6-26.1) a. Should be used only in detention ponds with less than 30 acre total drainage area. b. Never to be used on exposed pipe end or winged headwall. c. Diameter of half-round pipe should be 1.5 times the diameter of the principal pipe outlet or wider than the greatest width of the con­ crete weir. d. Perforations and stone sizes are shown in Figure 6-26.1. e. Shall be affixed by specified means (bolts, etc) to concrete outlet structure. Retrofitting Rt Rt -P ---PAGE BREAK--- 6-130 2016 Edition Slotted Board Dam with Stone or Filter Fabric (See Figure 6-26.3) a. Can be used in detention ponds with drain­ age areas up to 100 acres, and on roadway­ drainage structures with drainage areas less than 30 acres. b. Can be used with open end pipe outlets, winged headwalls, or concrete weir outlets. c. Should be installed with minimum size 4x4 inch posts. d. Boards should have 0.5-1.0 inch space be­ tween them. e. Minimum size 3-4 inch stone filter or ap­ proved filter fabric shall be installed around the upstream side of the board dam. Example of Slotted Board Dam Silt Control Gate (See figure 6-26.3, 6-26.4, 6-26.5) The silt control gate may be used for temporary sediment storage on linear construc­ tion projects including roadway construction or maintenance, and utility line installation. The fol­ lowing specifications shall apply: a. Shall only be used on roadway drainage structures with the following inlets: winged headwalls, tapered headwalls, straight head­ walls, open end pipes, or flared end sections. b. Drainage area to the silt control gate shall not exceed 50 acres, and the disturbed area of the basin shall not exceed 5 acres. c. Post shall be 4”x4” treated lumber, and face boards shall be 2”x6” treated lumber with no Rt -B spacing allowed between the boards. d. An approved silt fence fabric shall be se­ curely fastened to the front of the structure using staples or nails. e. Sediment shall be removed and properly disposed of when it reaches one-third the height of the silt gate. Filter fabric shall be replaced when damaged or deteriorated. f. Silt control gates should not be used as perimeter control alone, but instead be part of a treatment train that allows the drainage structure to discharge through another bar­ rier before leaving the project. All disturbed areas shall be vegetated immedi­ ately after construction with permanent vegetation. Refer to Ds3 and Ds4 - Disturbed Area Stabiliza­ tion (With Permanent Vegetation) and Disturbed Area Stabilization (With Sodding) and Ss- Slope Stablization. MAINTENANCE Retrofit structures shall be kept clear of trash and debris. This will require continuous monitor­ ing and maintenance, which includes sediment removal when one-third of the sediment storage capacity has been lost. Structures are tempo­ rary and shall be removed when disturbed areas have been permanently stabilized. Rt -Sg ---PAGE BREAK--- 6-131 2016 Edition TO BE SHOWN ON THE EROSION AND SEDIMENT CONTROL PLAN Storage Calculations 1. Required stormwater storage = cy (as determined by local ordinance) 2. Required sediment storage = cy (67 cy/ac * ac disturbed area) 3. Total required storage = + = cy 4. Available storage = cy 5. Is the available storage greater than the total required storage yes no 6. If “no”, the sediment storage capacity of the pond must be increased. Choose the method to be used: Raise the invert of the outlet structure inches Undercut the pond feet Other 7. Clean-out elevation (Elevation corresponding to 22 cy/ac disturbed area) 8. Is the length-width ratio 2:1 or greater? yes no 9. If “no”, the length of flow must be increased. Choose the method to be used: Baffles (Type of baffle: ) Other Note the CMP diameter and height if a half-round CMP retrofit is to be used. Diameter =______inches Height ---PAGE BREAK--- 6-132 2016 Edition Figure 6-26.1 Perforated Half- Round Pipe with Stone Filter ---PAGE BREAK--- 6-133 2016 Edition Figure 6-26.2 Stone Filter Ring ---PAGE BREAK--- 6-134 2016 Edition Figure 6-26.3 Slotted Board Dam with Stone or Filter Fabric ---PAGE BREAK--- 6-135 2016 Edition Figure 6-26.4 Silt Control Gate ---PAGE BREAK--- 6-136 2016 Edition Figure 6-26.5 Silt Control Gate ---PAGE BREAK--- 6-137 2016 Edition DEFINITION Sediment Barriers are temporary structures made up of a porous material typically supported by steel or wood posts. Types of sediment bar­ riers may include silt fence, brush piles, mulch berms, compost filter socks or other filtering material. PURPOSE To minimize and prevent sediment carried by sheet flow from leaving the site and entering natural drainage ways or storm drainage sys- tems by slowing storm water runoff and causing the deposition and/or filtration of sediment at the structure. The barriers retain the soil on the dis­ turbed land until the activities disturbing the land are completed and vegetation is established. CONDITIONS Barriers should be installed where runoff can be stored behind the barrier without damaging the submerged area behind the barrier or the structure itself. Sediment barriers shall not be installed across streams, ditches, waterways, or other concentrated flow areas. DESIGN CRITERIA Sediment barriers are designed to retain sedi- ment transported by sheet flow from disturbed areas. It is important for the design professional to take into account the profile of the product for use on the site. Sediment Barriers should also provide a riprap splash pad or other outlet protection device for any point where flow may overtop the sediment barrier. Ensure that the maximum height of the barrier at a protected, reinforced outlet does not exceed 1 foot and that the support spacing does not exceed 4 feet. Where all runoff is to be stored behind the sediment barrier (where no storm water disposal system is present), maximum continuous slope length behind a sediment barrier shall not ex­ ceed those shown in Table 6-27.1. For longer slope slope interrupters must be used. The drainage area shall not exceed ¼ acre for every 100 feet of sediment barrier. Table 6-27.1 Criteria for Sediment Barrier Land Slope Maximum Slope Length Above Fence Percent Feet < 2 2 to 5 5 to 10 10 to 20 >20* 100 75 50 25 15 *In areas where the slope is greater than 20%, a flat area length of 10 feet between the toe of slope to the barrier should be provided. Placement The type of sediment barrier depends on whether the area is sensitive or nonsensitive. Sensitive areas can be defined as any area that needs additional protection, these areas include but are not limited to, state waters, wetlands, or any area the design professional designates as sensitive. When using multiple types of sediment barri­ ers on a site in a single run, the barriers must be overlapped 18 inches or as specified by design professional. See Figure 6-27.5 CONSTRUCTION SPECIFICATIONS Non-sensitive Areas * Sediment barriers being used as Type NS shall have a support spacing of no greater than 6 feet on center, with each being driven into the ground a minimum of 18 inches. Sediment Barrier Sd1 Sd1-NS ---PAGE BREAK--- 6-138 2016 Edition Sensitive Areas* Sediment barriers being used as Type S shall have a support spacing of no greater than 4 feet on center, with each being driven into the ground a minimum of 18 inches. *As of January 1 2016, in the existing Georgia Department of Transportation Qualified Products list #36 (QPL- 36), Type A, B, or C will fall under sensitive and non-sensitive applications. Type C will be classified as sensitive and Type A and B as non-sensitive. Refer to Appendix A-2 and the Equivalent BMP List. PRACTICE CLASSIFICATIONS For silt fence Type A, B, or C, refer to Table 6-27.4. Type A Silt Fence This 36-inch wide filter fabric shall be used on developments where the life of the project is great than or equal to six months. Type A is classified as non-sensitive application. Type B Silt Fence Though only 22-inches wide, this filter fabric allows the same flow rate as Type A silt fence. Type B silt fence shall be limited to use on minor projects, such as residential home sites or small commercial developments where permanent stabilization will be achieved in less than six months. Type B is classified as non-sensitive application. Type C Silt Fence Type C fence is 36-inches wide with wire rein­ forcement or equivalent. The wire reinforcement is necessary because this fabric allows almost three times the flow rate as Type A silt fence. Type C silt fence shall be used where runoff flows or velocities are particularly high or where slopes exceed a vertical height of 10 feet. Type C is classified as sensitive application. Filter Media Sock Specifications Compost filter media used for sediment bar­ rier filler material shall be weed free and derived from a well-decomposed source of organic mat­ ter. Filter Media Sock is classified as a Type B, non-sensitive application. The compost shall be produced using an aerobic composting process meeting CFR 503 regulations including time and temperature data. The compost shall be free of any refuse, contaminants or other materi­ als toxic to plant growth. Non-composted prod­ ucts will not be accepted without applicable water quality test results. Test methods for the items below should follow US Composting Council Test Methods for the Examination of Composting and Compost guidelines for laboratory procedures: A. pH – 5.0-8.0 in accordance with TMECC 04.11-A, “Electrometric pH Determinations for Compost” B. Particle size – 99% passing a 2 inch (50mm) sieve and a maximum of 40% passing a 3/8 inche (9.5mm) sieve, in accordance with TMECC 02.02-B, “Sample Sieving for Aggregate Size Classification”. (Note: In the field, product commonly is between ½ in./12.5mm and 2 in./50 mm in particle size.) C. Moisture content of less than 60% in accordance with standardized test methods for moisture determination. D. Material shall be relatively free by dry weight) of inert or foreign manmade materials. E. Sock containment system for compost filter media shall be a photodegradable or biode- gradable knitted mesh material and should have 1/8 in. to 3/8 in., openings. Brush Barrier (Only during timber clearing operations) Brush obtained from clearing and grubbing operations may be piled in a row along the pe- rimeter of disturbance at the time of clearing and grubbing. Brush barriers should not be used in developed areas or locations where aesthetics are a concern. Brush should be wind-rowed on the contour as nearly as possible and may require compaction. Construction equipment may be utilized to satisfy this requirement. The minimum base width of the brush barrier shall be 5 feet and should be no wider 10 feet. The height of the brush barrier should be be- tween 3 and 5 feet tall. Sd1-S Sd1-BB ---PAGE BREAK--- 6-139 2016 Edition A brush barrier is a good tool to use in develop­ ing pasture in an agricultural situation to prevent sediment from leaving the site until the pasture is stabilized. If greater filtering capacity is required, a com­ mercially available sediment barrier may be placed on the side of the brush barrier receiving the sediment-laden runoff. The lower edge of the fabric must be buried in a 6-inch deep trench im­ mediately uphill from the barrier. The upper edge must be stapled, tied or otherwise fastened to the brush barrier. Edges of adjacent fabric pieces must overlap each other. See Figure 6-27.5. Installation Sediment barriers should be installed along the contour. Temporary sediment barriers shall be installed according to the following specifications as shown on the plans or as directed by the design professional. For installation of the barriers, See Figures 6-27.1, 6-27.2, 6-27.3 and 6-27.4, respectively. It is important to remember that not all sediment barriers need to be trenched into the ground but most taller sediment barriers do. Post installation shall start at the center of a low point (if applicable) with the remaining posts spaced no greater than 6 feet apart for Type NS sediment barriers and no greater than 4 feet apart for Type C sediment barriers. For post size requirements, see Table 6-27.2. Fasteners for wood posts are listed in Table 6-27.3. Static Slicing Method The static slicing machine pulls a narrow blade through the ground to create a slit 12” deep, and simultaneously inserts the silt fence fabric into this slit behind the blade. The blade is designed to disrupt soil upward next to the slit and to minimize horizontal compac­ tion, thereby creating an optimum condition for compacting the soil vertically on both sides of the fabric. Compaction is achieved by rolling a tractor wheel along both sides of the slit in the ground 2 to 4 times to achieve nearly the same or greater compaction as the original undisturbed soil. This vertical compaction reduces the air spaces between soil particles, which minimizes infiltration. Without this compaction infiltration can saturate the soil, and water may find a path­ way under the fence. When a silt fence is hold­ ing back several tons of accumulated water and sediment, it needs to be supported by posts that are driven 18 inches into the soil. Driving in the posts and attaching the fabric to them completes the installation. Trenching Method Trenching machines have been used for over twenty-five years to dig a trench for burying part of the filter fabric underground. Usually the trench is about 2-”6” wide with a 6” excavation. Post setting and fabric installation often precede compaction, which make effective compaction more difficult to achieve. EPA supported an inde­ pendent technology evaluation (ASCE 2001), which compared three progressively better varia­ tions of the trenching method with static slicing method. The static slicing method performed better than two lower performance levels of the trenching method, and was as good as or better than the trenching method’s highest performance level. The best trenching method typically re­ quired nearly triple the time and effort to achieve results comparable to the static slicing method. Along all state waters and other sensitive areas, two rows of Type S sediment barriers shall be used. The two rows of Type S should be placed a minimum of 36 inches apart. MAINTENANCE Sediment shall be removed once it has accumulated to one-half the original height of the barrier. Sediment barriers shall be replaced whenever they have deteriorated to such an extent that the effectiveness of the product is reduced (approxi­ mately six months) or the height of the product is not maintaining 80% of its properly installed height. Temporary sediment barriers shall remain in place until disturbed areas have been perma­ nently stabilized. All sediment accumulated at the barrier shall be removed and properly dis­ posed of before the barrier is removed. TO BE SHOWN ON THE EROSION, SEDIMENTATION, AND POLLUTION CONTROL PLAN When a SEDIMENT BARRIER is used, show the product height in inches for each barrier being used on site. ---PAGE BREAK--- 6-140 2016 Edition REFERENCES: ASCE 2001. Environmental Technology Verification Report for Installation of Silt Fence Using the Tommy Static Slicing Method, CERF Report #40565. Washington, DC: American Society of Civil Engineers. www.epa.gov/etv/pubs/08_vs_tommy.pdf ASTM 2003. Standard Practice for Silt Fence Installation, D 6462-03(2008). West Conshohocken, PA: American Society of Testing Materials International. www.astm.org/SEARCH/search-reskin. Carpenter, Thomas 2000. Silt Fence That Works. Ankey, Iowa: Thomas Carpenter. www.tommy-sfm.com/ pages/resources/ Silt%20Fence%20That%20Works%20Manual.pdf Fifield, Jerald S. 2011. Designing and Reviewing Effective Sediment and Erosion Control Plans, 3rd Edi­ tion. Santa Barbara, CA: Forester Press. U.S. Environmental Protection Agency 2007. Developing Your Stormwater Pollution Prevention Plan, EPA 833-R-06-004. Washington: EPA. Available from EPA hardcopy [PHONE REDACTED] or www.epa.gov/npdes/ ---PAGE BREAK--- 6-141 2016 Edition Figure 6-27.1 SILT FENCE - TYPE A and B ---PAGE BREAK--- 6-142 2016 Edition Figure 6-27.2 SILT FENCE - TYPE C FABRIC (WOVEN WIRE FENCE OR ALTERNATIVE BACKING) ---PAGE BREAK--- 6-143 2016 Edition NOTE: FILTER SOCK SIZED TO SUIT CONDITIONS AND AT LEAST 18” DIA (SEE EQUIVALENT LIST) 2’ *HEIGHT IS TO BE SHOWN ON THE EROSION, SEDIMENTATION AND POLLUTION CONTROL PLAN * Figure 6-27.3 TYPE B COMPOST FILTER SOCK ---PAGE BREAK--- 6-144 2016 Edition Figure 6-27.4 ---PAGE BREAK--- 6-145 2016 Edition Table 6-27.2 Post Size Type Min Length Type of Post Size of Post NS 4’ Soft wood Oak Steel 3”dia or 2x4 1.5” x1.5” 1.15lb./ft. min S 4’ Steel Oak 1.15-1.25 lb./ ft. min 2”x2” Table 6-27.3 Fasteners for Wood Posts Gauge Crown Legs Staples / Post Wire Staples 17 min. 3/4” wide 1/2” long 5 min. Gauge Length Button Heads Nail/ Post Nails 14 min. 1” 3/4” 4 min. Note: Filter Fabric may also be attached to the post by wire, cords, and pockets. Figure 6-27.5 . ---PAGE BREAK--- 6-146 2016 Edition TYPE FENCE A B C Tensile Strength (Lbs. Min.) Warp - 120 Warp - 120 Warp - 260 (ASTM D-4632) Fill - 100 Fill - 100 Fill - 180 Elongation Max.) (ASTM D-4632) 40 40 40 AOS (Apparent Opening Size) (Max. Sieve Size) (ASTM D-4751) #30 #30 #30 Flow Rate (Gal/Min/Sq. Ft.) (GDT-87) 25 25 70 Ultraviolet Stability (ASTM D-4632 after 300 hours weathering in accordance with 80 80 80 ASTM D-4355) Bursting Strength (PSI Min.) (ASTM D-3786 Diaphragm Bursting 175 175 175 Strength Tester) Minimum Fabric Width (Inches) 36 22 36 Minimum roll average of five specimens. Percent of required initial minimum tensile strength. Table 6-27.4 ---PAGE BREAK--- 6-147 2016 Edition Inlet Sediment Trap Sd2 Sd2 -F filter ring may be used on the up slope side of the inlet to slow runoff and filter larger soil par­ ticles. Refer to Fr-Stone Filter Ring. CONSTRUCTION SPECIFICATIONS Excavated Inlet Sediment Trap An excavation may be created around the inlet sediment trap to provide additional sediment storage. The trap shall be sized to provide a minimum storage capacity calculated at the rate of 67 cubic yards per acre of drainage area. A minimum depth of 1.5 feet for sediment storage should be provided. Side slopes shall not be steeper than 2:1. Sediment traps may be constructed on natu­ ral ground surface, on an excavated surface, or on machine compacted fill, provided they have a non-erodible outlet. Filter Fabric with Supporting Frame This method of inlet protection is applicable where the inlet drains a relatively flat area (slope no greater than and shall not apply to inlets receiving concentrated flows, such as in street or highway medians. As shown in Figure 6-28.1, Type S silt fence supported by steel posts should be used. The stakes shall be spaced evenly around the perimeter of the inlet a maximum of 3 feet apart, and securely driven into the ground, approximately 18 inches deep. The fabric shall be 36 inches tall and entrenched 12 inches and backfilled with crushed stone or compacted soil. Fabric and wire shall be securely fastened to the posts, and fabric ends must be overlapped a minimum of 18 inches or wrapped together around a post to provide a continuous fabric bar­ rier around the inlet. Baffle Box For inlets receiving runoff with a higher vol­ ume or velocity, a baffle box inlet sediment trap should be used. As shown in Figure 6-28.2, the baffle box shall be constructed of 2” x 4” boards spaced a maximum of 1 inch apart or of plywood with weep holes 2 inches in diameter. The weep holes shall be placed approximately 6 inches on center vertically and horizontally. Gravel shall be placed outside the box, all around the inlet, to a depth of 2 to 4 inches. The entire box is wrapped DEFINITION A temporary protective device formed at or around an inlet to a storm drain to trap sediment. PURPOSE To prevent sediment from entering a storm drainage systems prior to permanent stabilization of the disturbed area draining to the inlet. CONDITIONS All storm drain drop inlets that receive runoff from disturbed areas. DESIGN CRITERIA Through testing there are two different categories (high retention and high flow) supported. In areas where BMPs are being used on paved surfaces, or safety is a concern, the potentially negative effects of ponding should be taken into account. In such cases, a high flow BMP is preferred. On unpaved areas where ponding will not cause a safety hazard, high retention shall be taken into account. If high retention is not used in this situation a rationale shall be given on the plan and an unpaved application should apply. Sediment traps must be self-draining unless they are otherwise protected in an approved fashion that will not present a safety hazard. The drainage area entering the inlet sediment trap shall be no greater than one acre. If runoff may bypass the protected inlet, a temporary dike should be constructed on the down slope side of the structure. Also, a stone Sd2 -B ---PAGE BREAK--- 6-148 2016 Edition Sd2 -Bg Sd2-G Sd2-S Sd2-P in Type C filter fabric that shall be entrenched 12 inches and backfilled. Block and Gravel Drop Inlet Protection This method of inlet protection is applicable where heavy flows are expected and where an overflow capacity is necessary to prevent exces­ sive ponding around the structure. As shown in Figure 6-28.3, one block is placed on each side of the structure on its side in the bottom row to allow pool drainage. The foundation should be excavated at least 2 inches below the crest of the storm drain. The bottom row of blocks is placed against the edge of the storm drain for lateral support and to avoid washouts when overflow occurs. If needed, lateral support may be given to subsequent rows by placing 2” x 4” wood studs through block openings. Hardware cloth or comparable wire mesh with 1/2 inch openings shall be fitted over all block openings to hold gravel in place. Clean gravel should be placed 2 inches below the top of the block on a 2:1 slope or flatter and smoothed to an even grade. DOT #57 washed stone is recommended. Gravel drop Inlet Protection This method of inlet protection is applicable where heavy concentrated flows are expected. As shown in Figure 6-28.4, stone and gravel are used to trap sediment. The slope toward the inlet shall be no steeper than 3:1. A minimum 1 foot wide level stone area shall be left between the structure and around the inlet to prevent gravel from entering the inlet. On the slope toward the inlet, stone 3 inches in diameter and larger should be used. On the slope away from the inlet, 1/2 to 3/4 inch gravel (#57 washed stone) should be used at a minimum thickness of 1 foot. Sod Inlet Protection This method of inlet protection is applicable only at the time of permanent seeding, to protect the inlet from sediment and mulch material until permanent vegetation has become established. As shown in Figure 6-28.5, the sod shall be placed to form a turf mat covering the soil for a distance of 4 feet from each side of the inlet structure. Sod strips shall be staggered so that adjacent strip ends are not aligned. Curb Inlet Protection Once pavement has been installed, a curb inlet filter shall be installed on inlets receiving runoff from disturbed areas. This method of inlet protection shall be removed if a safety hazard is created. One method of curb inlet protection uses “pigs-in-a-blanket”- 8-inch concrete blocks wrapped in filter fabric. See Figure 6-28.6. An­ other method uses gravel bags constructed by wrapping DOT #57 stone with filter fabric, wire, plastic mesh, or equivalent material. A gap of approximately 4 inches shall be left between the inlet filter and the inlet to allow for overflow and prevent hazardous ponding in the roadway. Proper installation and maintenance are crucial due to possible ponding in the road­ way, resulting in a hazardous condition. Several other methods are available to prevent the entry of sediment into storm drain in­ lets. Figure 6-28.7 shows one of these alternative methods. MAINTENANCE The trap shall be inspected daily and after each rain, and repairs made as needed. Sedi­ ment shall be removed when the sediment has accumulated to one-half the height of the trap. Sediment shall be removed from curb inlet pro­ tection immediately. For excavated inlet sediment traps, sediment shall be removed when one-half of the sediment storage capacity has been lost to sediment accumulation. Sod inlet protection shall be maintained as specified in Ds4 - Dis­ turbed Area Stabilization (With Sodding). Sediment shall not be washed into the inlet. It shall be removed from the sediment trap, dis­ posed of and stabilized so that it will not enter the inlet again. When the contributing drainage area has been permanently stabilized, all materials and any sediment shall be removed, and either ---PAGE BREAK--- 6-149 2016 Edition salvaged or disposed of properly. The disturbed area shall be brought to proper grade, then smoothed and compacted. Appropriately stabilize all disturbed areas around the inlet. ---PAGE BREAK--- 6-150 2016 Edition Figure 6-28.1 - Fabric and Supporting Frame For Inlet Projection ---PAGE BREAK--- 6-151 2016 Edition Figure 6-28.2 Baffle Box ---PAGE BREAK--- 6-152 2016 Edition Figure 6-28.3 Block and Gravel Drop Inlet Protections ---PAGE BREAK--- 6-153 2016 Edition Figure 6-28.4 Gravel Drop Inlet Protection Figure 6-28.5 Sod Inlet Protection ---PAGE BREAK--- 6-154 2016 Edition Figure 6-28.6 Curb Inlet Filter “Pigs in Blanket” ---PAGE BREAK--- 6-155 2016 Edition TO BE SHOWN ON THE EROSION AND SEDIMENT CONTROL PLAN If the EXCAVATED INLET SEDIMENT TRAP is used, show the following information: 1. Drainage area = ac 2. Required sediment storage = 67 cy/ac * drainage area Required sediment storage = 67 cy/ac * ac Required sediment storage = cy = cf 3. Assume excavation depth (minimum of 1.5 ft.) = ft 4. Assume slope of sides (shall not be steeper than 2:1) = :1 5. Determine required surface area SAmin = Required sediment storage / excavation depth SAmin = cy / ft SAmin = sf 6. Assume shape of excavation and determine dimensions. (A rectangular shape with 2:1 length to width ratio is recommended.) Shape: Dimensions: l = ft w = ft diameter (if applicable) = ft Provide a detail showing the depth, length and width, or diameter (if applicable), and side slopes of the excavation. Figure 6-28.7 Equivalent Inlet Sediment Trap ---PAGE BREAK--- 6-156 2016 Edition ---PAGE BREAK--- 6-157 2016 Edition DEFINITION A basin created by the construction of a bar­ rier or dam across a concentrated flow area, or by excavating a basin, or by a combination of both. A sediment basin typically consists of a dam, a pipe outlet, and an emergency spillway. The size of the structure will depend upon the location, size of the drainage area, soil type, and rainfall pattern. PURPOSE To detain runoff waters and trap sediment from erodible areas in order to protect properties and drainage ways below the installation from damage by excessive sedimentation and debris. The water is temporarily stored and the bulk of the sediment carried by the water drops out and is retained in the basin while the water is auto­ matically released. CONDITIONS This practice applies to critical areas where physical site conditions, construction schedules, or other restrictions preclude the installation or establishment of erosion control practices to sat­ isfactorily reduce runoff, erosion, and sedimenta­ tion. The structure may be used in combination with other practices and should remain in effect until the sediment-producing area is permanently stabilized. This standard applies to the installation of tem­ porary (to be removed within 18 months) sediment basins on sites where: failure of the structure would not result in loss of life or interruption of use or service of public utilities, and the drainage area does not exceed 150 acres. DESIGN CRITERIA Compliance With Laws and Regulations Design and construction shall comply with state and local laws, ordinances, rules and regu­ lations. Basins shall be constructed according to the approved erosion and sediment control plan unless modified by the design professional. Location Sediment basins shall never be placed in live streams. They should be located so that storm drains discharge into the basin. The sediment basin should be located to obtain the maximum storage benefit from the terrain and for ease of clean-out of the trapped sediment. It should be located to minimize interference with construction activities and construction of utilities. Volume The sediment storage volume of the basin, as measured to the elevation of the crest of the principal spillway, shall be at least 67 cubic yards per acre for the disturbed area draining into the basin (67 cubic yards is equivalent to 1/2 inch of sediment per acre of drainage area). The entire drainage basin area should be used for this com­ putation, rather than the disturbed area alone, to help ensure adequate trapping efficiency. Sediment shall be removed from the basin when approximately one-third of the storage volume has been lost to sediment accumulation. This volume shall be marked on the riser or by setting a marked post near the riser. Surface Area Studies (Barfield and Clar, 1985) indicate that the following relationship between surface area and peak inflow rate gives a trapping efficiency from greater than 75% for clay loam to 95% for loamy sandy soils. A = 0.01q Where A is basin surface area in acres and q is peak inflow rate in cfs. Area is measured at the crest of the principal spillway riser. The minimum peak inflow rate is determined from a 2-year, 24- hour storm. Shape It is recommended that the designer of a sedi­ ment basin incorporate features to maximize de­ tention time within the basin. Suggested methods Temporary Sediment Basin Sd3 ---PAGE BREAK--- 6-158 2016 Edition of accomplishing this objective are: 1. Length to width ratio greater than 2:1, where length is the distance between the inlet and outlet. 2. A wedge shape with the inlet located at the narrow end. 3. Installation of baffles or diversions. Procedure for Determining or Altering Sediment Basin Shape As specified in the Standards and Specifica­ tion, the pool area at the elevation of crest of the principal spillway shall have a length to width ratio of at least 2:1. The purpose of this requirement is to minimize the “short-circuiting” effect of the sediment-laden inflow to the riser and thereby in­ creasing the effectiveness of the sediment basin. The purpose of this procedure is to prescribe the parameters, procedures and methods of determin­ ing and modifying the shape of the basin. The length of the flow path is the distance from the point of inflow to the riser (outflow point). The point of inflow is the point that the stream en­ ters the normal pool (pool level at the riser crest elevation). The pool area is the area of the normal pool. The effective width (We) is equal to the Area divided by the length The length to width ratio (L:W) is found by the equation: L:W= I/We where We = A/L In the event there is more than one inflow point, any inflow point that conveys more than 30 percent of the total peak inflow rate shall meet the length- width ratio criteria. The required basin shape may be obtained by proper site selection, by excavation, or by con­ structing a baffle in the basin. The purpose of the baffle is to increase the effective flow length from the inflow point to the riser. Baffles shall be placed mid-way between the inflow point and the riser. The baffle length shall be as required to provide the minimum 2:1 length-width ratio. The effective length (Le) shall be the shortest distance the water must flow from the inflow point around the end of the baffle to the outflow point. Then: L:W = Le/We where We = A/Le Three examples are shown on the following pages. Note that for the special case in example C the water is allowed to go around both ends of the baffle and the effective length, Le = L1a + L1b = L2a + L2d. Otherwise, the length-width ratio computa­ tions are the same as shown above. This special case procedure for computing Le is allowable only when the two flow paths are equal, i.e., when L1 = L2. A baffle detail is also shown. For examples of sediment basin baffles, refer to Figure 6-29.2. The dimensions necessary to obtain the required basin volume and surface area shall be clearly shown on the plans to facilitate plan review, con­ struction and inspection. Spillways Runoff may be computed by the method outlined in Appendix A. Other approved equiva­ lent methods may be used. Runoff computa­ tions shall be based upon the worst soil-cover conditions expected to prevail in the contributing drainage area during the anticipated effective life of the structure. The combined capacities of the principal and emergency spillway shall be sufficient to pass the peak rate of runoff from a 25-year, 24-hour frequency storm. Even if the principal spillway is designed to convey the peak rate of runoff from a 25-year, 24,-hour storm, an emergency spillway shall be present. 1. Principal spillway - A spillway consisting of a vertical pipe or box type riser joined (watertight connection) to a pipe that shall extend through the embankment and an outlet beyond the toe of the fill shall be provided. See Figure 6-29.3. The metal gauge thickness shall comply with DOT or NRCS specifications. The discharge shall be based on a 2-year, 24-hour storm for the total drainage area without causing flow through the emergency spillway. The appropriate disturbed soil cover condition shall be used. The minimum size of the pipe shall be 8 inches in diameter. Principal spillway capacities may be determined from Table 6-29.1. Weir flow discharge above the crest of the riser may be determined from Table 6-29.2. Principal spillway pipe, riser pipe, and trash rack proportions are shown in Table 6-29.2. a. Crest elevation - The crest elevation of the riser shall be a minimum of one foot ---PAGE BREAK--- 6-159 2016 Edition below the elevation of the control section of the emergency spillway. b. Watertight barrel assembly - The riser and all pipe connections shall be com­ pletely water tight except for the inlet opening at the top or dewatering openings, and shall not have any other holes, leaks, rips or perforations. c. Dewatering the basin - Retention time within the basin is an important factor in effective sediment retention. The method used to dewater the sediment basin may be selected from the following two meth­ ods: Perforated Riser Pipe - The perforated riser pipe is the conventional method for dewatering a sedi­ ment basin. The lower half of the riser is perforated with 1/2-inch holes spaced approximately 3-inches apart. It is covered with two feet of 3 to 4 inch stone. Skimmer Outlet - The skimmer-type dewatering device operates at the surface of the ponded water and will not withdraw sediment from the submerged volume of the basin. As compared to conventional perforated risers, skimmers discharge a 45 percent less mass of sediment. However, skimmers are me­ chanically more complex and will require frequent inspection and maintenance in order to operate as designed. Refer to specification Sk-Floating Surface Skimmer. d. Trash rack and anti-vortex device - A trash rack and anti-vortex device shall be securely installed on top of the riser and may be the type as shown in Figure 6-29.4. e. Base - The riser shall have a base at­ tached with a watertight connection and shall have sufficient weight to prevent flotation of the riser. A concrete base 18” thick with the riser embedded 9-inches in the base is recommended. Computations shall be made to design a base that will prevent flotation. See Figure 6-29.5 and Table 6-29.3 for details. f. Anti-Seep Collars - One anti-seep collar shall be installed around the pipe, near the center of the dam, when any of the following conditions exist: 1. The settled height of the dam is greater than 15 feet. 2. The conduit is smooth pipe larger than 8” in diameter. 3. The conduit is corrugated metal pipe larger than 12” in diameter. Use an anti-seep collar with an 18- inch projection for heads less than or equal to 10 feet and a 24-inch projection for heads greater than 10 feet. The anti-seep collar and its connection shall be watertight. g. Outlet - An outlet shall be provided, includ­ ing a means of conveying the discharge in an erosion-free manner to an existing stable area. Where discharge occurs at the property line, drainage easements will be obtained in accordance with local ordi­ nances. Adequate notes and references will be shown on the erosion and sediment control plan. Protection against scour at the discharge end of the pipe spillway shall be provided. Measures may include exca­ vated plunge pools, riprap, impact basins, revetments, or other approved methods. Refer to specification St - Storm Drain Outlet Protection. h. For typical features of a temporary sedi­ ment basin, see Figure 6-29.1. 2. Emergency Spillway - The entire flow area of the emergency spillway shall be con­ structed in undisturbed ground (not fill). The emergency spillway cross-section shall be trapezoidal with a minimum bottom width of eight feet. This spillway channel shall have a straight control section of at least 20 feet in length and a straight outlet section for a minimum distance equal to 25 feet. See Figure 6-30.6. a. Capacity - The minimum capacity of the emergency spillway shall be that required to pass the peak rate of runoff from the 25-year, 24-hour frequency storm, less any reduction due to flow in the principal spillway. The appropriate disturbed soil cover condition shall be used. Emergency spillway dimensions may be determined by using the method described in this section. Refer to Table 6-29.4 and Figure ---PAGE BREAK--- 6-160 2016 Edition 6-29.6. b. Velocities - The velocity of flow in the exit channel shall not exceed 5 feet per second for vegetated channels. For channels with erosion protection other than vegetation, velocities shall be within the non-erosive range for the type of protection used. Veg­ etation, riprap, asphalt or concrete shall be provided to prevent erosion. Refer to specification Ch - Channel Stabilization. c. Freeboard - Freeboard is the difference between the design high water elevation in the emergency spillway and the top of the settled embankment. The freeboard shall be at least one foot. Entrance of Runoff Into Basin Points of entrance of surface runoff into excavated sediment basins shall be protected to prevent erosion and sediment generation. Dikes, swales, or other water control devices, shall be installed as necessary to direct runoff into the basin. Points of runoff entry should be located as far away from the riser as possible, to maximize travel time. Refer to St - Storm Drain Outlet Protection. CONSTRUCTION SPECIFICATIONS Site Preparation Areas under the embankment and under structural works shall be cleared, grubbed, and stripped of top-soil. All trees, vegetation, roots and other objectionable material shall be re­ moved and disposed of by approved methods. In order to facilitate clean-out or restoration, the pool area (measured at the top of the pipe spill­ way) will be cleared of all brush and trees. Cut-off Trench A cut-off trench will be excavated along the center-line of earth fill embankments. The mini­ mum depth shall be 2 feet. The cut-off trench shall extend up both abutments to the riser crest elevation. The minimum bottom width shall be 4 feet, but wide enough to permit operation of compaction equipment. The side slopes shall be no steeper than 1:1. Compaction requirements shall be the same as those for the embankment. The trench shall be drained during the backfilling and compaction operations. Embankment The fill material shall be taken from approved areas shown on the plans. It shall be clean mineral soil free of roots, woody vegetation, oversized stones, rocks or other objectionable material. Relatively pervious materials such as sand or gravel (Unified Soil Classes GW, GP, SW & SP) shall be placed in the section of the embankment. Areas on which fills are to be placed shall be scarified prior to placement of fill. The fill material shall contain sufficient moisture so that it can be formed by hand into a ball without crumbling. If water can be squeezed out of the ball, it is too wet for proper compac­ tion. Fill material shall be placed in six-inch to eight-inch thick continuous layers over the entire length of the fill. Compaction shall be obtained by routing and hauling the construction equipment over the fill so that the entire surface of the fill is traversed by at least one wheel or tread track of the equipment or by the use of a compactor. The embankment shall be constructed to an elevation 5 percent higher than the design height to allow for settlement. Principal Spillway The riser shall be securely attached to the pipe or pipe stub by welding the full circumfer­ ence making a watertight structural connection. The pipe stub must be attached to the riser at the same percent (angle) of grade as the outlet conduit. The connection between the riser and the riser base shall be watertight. All connec­ tions between pipe sections must be achieved by approved watertight band assemblies. The pipe and riser shall be placed on a firm, smooth foundation of impervious soil as the embank­ ment is constructed. Breaching the embankment is unacceptable. Pervious materials such as sand, gravel, or crushed stone shall not be used as backfill around the pipe or anti-seep collar. The fill material around the pipe spillway shall be placed in four inch layers and compacted under and around the pipe to at least the same density as the adjacent embankment. Care must be taken not to raise the pipe from firm contact with its foundation when compacting under the pipe haunches. A minimum depth of two feet of hand compacted backfill shall be placed over the pipe spillway before crossing it with construction equipment. ---PAGE BREAK--- 6-161 2016 Edition Emergency Spillway The emergency spillway shall be installed in undisturbed ground. The achievement of planned elevations, grades, design width, en­ trance and exit channel slopes are critical to the successful operation of the emergency spillway and must be constructed within a tolerance of ± 0.2 feet. If the emergency spillway requires ero­ sion protection other than vegetation, the lining shall not compromise the capacity of the emer­ gency spillway, e.g. the emergency spillway shall be over-excavated so that the lining will be flush with the slope surface. Vegetative Treatment Stabilize the embankment and all other disturbed areas in accordance with the ap­ propriate permanent vegetative measure, Ds3, immediately following construction. In no case shall the embankment remain unstabilized for more than seven days. Refer to specifications Ds2 Disturbed Area Stabilization (Temporary Seeding) , Ds3 - Disturbed Area Stabilization (Permanent Vegetation) and Ds4 - Disturbed Area Stabilization (With Sodding) respectively. Erosion and Pollution Control Construction operations will be carried out in such a manner that erosion and water pollution will be minimized. State and local law concerning pollution abatement shall be complied with. Safety State and local requirements shall be met concerning fencing and signs warning the public of hazards of soft sediment and floodwater. MAINTENANCE Repair all damages caused by soil erosion or construction equipment at or before the end of each working day. Sediment shall be removed from the basin when it reaches the specified distance below the top of the riser. Sediment shall not enter adjacent streams or drainageways during sediment removal or disposal. The sediment shall not be deposited from the embankment, adjacent to a stream or floodplain. FINAL DISPOSAL When temporary structures have served their intended purpose and the contributing drainage area has been properly stabilized, the embank­ ment and resulting sediment deposits are to be leveled or otherwise disposed of in accordance with approved sediment control plan. The pro­ posed use of a sediment basin site will often dictate final disposition of the basin and any sedi­ ment contained therein. If the site is scheduled for future construction, then the embankment and trapped sediment must be removed, safely disposed of, and backfilled with a structural fill. When the basin area is to remain open space, the pond may be pumped dry, graded and back­ filled. ---PAGE BREAK--- 6-162 2016 Edition TO BE SUBMITTED WITH/ON THE EROSION, SEDIMENTATION AND POLLUTION CONTROL PLAN On the ES&PC Plan 1. The specific location of the basin, showing existing and proposed contours. 2. Maintenance equipment access points. 3. Completed Figures 6-29.7 and 6-29.8. (details for the cross section of dam, principal spillway, and emer­ gency spillway, and profile of emergency spillway). 4. Details of trash rack, concrete riser base, and outlet structure assembly. (Refer to Figures 6-29.4 to 6-29.6) On 8 1/2” x 11”Sheet(s) 1. Hydrological study, including information regarding stage/storage relationship. 2. Temporary sediment basin design sheet, p.6-231 to 6-233. 3. Completed Figures 6-29.7 and 6-29.8 (details for the cross section of the dam, principal spillway, and emergency spillway, and profile of emergency spillway). ---PAGE BREAK--- 6-163 2016 Edition Figure 6-29.1 ---PAGE BREAK--- 6-164 2016 Edition Figure 6-29.2 Baffels (Sheet 1 of 2) ---PAGE BREAK--- 6-165 2016 Edition Figure 6-29.2 (Sheet 2) ---PAGE BREAK--- 6-166 2016 Edition Figure 6-29.3 Principle Spillway ---PAGE BREAK--- 6-167 2016 Edition For Corrugated Metal Pipe Inlet Km = Ka+ Kb = 1.0 and 70 Feet of Corrugated Metal Conduit (full flow assumed), n = 0.025 (Note correction factors for pipe other than 70 feet) Diameter Of Pipe In Inches H, in feet 8” 12” 18” 24” 30” 36” 42” 48” Discharge In Cubic Feet Per Second 3 1.22 3.43 9.48 19.1 32.6 49.9 71.2 96.5 4 1.40 3.97 10.9 22.1 37.6 57.7 82.3 111 5 1.57 4.43 12.2 24.7 42.1 64.5 92.0 125 6 1.72 4.86 13.4 27.0 46.1 70.6 101 136 7 1.86 5.25 14.5 29.2 49.8 76.3 109 147 8 1.99 5.61 15.5 31.2 53.2 81.5 116 158 9 2.11 5.95 16.4 33.1 56.4 86.5 123 167 10 2.22 6.27 17.3 34.9 59.5 91.2 130 176 11 2.33 6.58 18.2 36.6 62.4 95.6 136 185 12 2.43 6.87 19.0 38.2 65.2 99.9 142 193 13 2.53 7.15 19.7 39.8 67.8 104 148 201 14 2.63 7.42 20.5 41.3 70.4 108 154 208 15 2.72 7.68 21.2 42.8 72.8 112 159 216 16 2.81 7.93 21.9 44.2 75.2 115 165 223 17 2.90 8.18 22.6 45.5 77.5 119 170 230 18 2.98 8.41 23.2 46.8 79.8 120 174 236 19 3.06 8.64 23.9 48.1 82.0 126 179 243 20 3.14 8.87 24.5 49.4 84.1 129 184 249 L, in feet Correction Factors For Other Pipe 30 1.41 1.36 1.29 1.24 1.21 1.18 1.15 1.13 40 1.27 1.23 1.20 1.17 1.14 1.12 1.11 1.10 50 1.16 1.14 1.12 1.10 1.09 1.08 1.07 1.06 60 1.07 1.06 1.05 1.05 1.04 1.04 1.03 1.03 70 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 80 0.94 0.95 0.95 0.96 0.96 0.97 0.97 0.97 90 0.89 0.90 0.91 0.92 0.93 0.94 0.94 0.95 100 0.85 0.86 0.88 0.89 0.90 0.91 0.92 0.93 120 0.79 0.90 0.82 0.83 0.85 0.86 0.87 0.89 140 0.73 0.75 0.77 0.79 0.81 0.82 0.84 0.85 160 0.69 0.70 0.73 0.75 0.77 0.79 0.80 0.82 Table 6-29.1. Pipe Flow Chart For Corrugated Metal Pipe Drop Inlet Principal Spillway Conduit ---PAGE BREAK--- 6-168 2016 Edition HEAD-h HEAD-h In feet 12 18 24 30 36 48 54 60 in feet Flow In Cubic Feet Per Second 0.1 0.3 0.5 0.6 0.8 0.9 1.2 1.4 1.5 0.1 0.2 0.9 1.3 1.7 2.2 2.6 3.5 3.9 4.4 0.2 0.3 1.6 2.4 3.2 4.0 4.8 6.4 7.2 8.0 0.3 0.4 2.5 3.7 4.9 6.2 7.4 9.9 11.1 12.3 0.4 0.6 4.5 6.8 9.1 11.3 13.6 18.1 20.4 22.6 0.6 0.8 10.5 13.9 17.4 20.9 27.9 31.4 34.8 0.8 1.0 19.5 24.3 29.2 39.0 43.8 48.7 1.0 1.2 25.6 32.0 38.4 51.2 57.6 64.0 1.2 1.4 40.3 48.4 64.5 72.6 80.7 1.4 1.6 49.3 59.1 78.8 88.7 98.6 1.6 1.8 70.6 94.1 105.8 117.6 1.8 2.0 82.6 110.2 124.0 137.7 2.0 2.2 127.1 143.0 158.9 2.2 2.4 162.9 181.0 2.4 2.6 183.7 204.1 2.6 2.8 228.1 2.8 3.0 253.0 3.0 Pipe, Riser, and Trash Rack Proportions Eq. 6-10 Dr > (1.50) (Dps) where Dr = diameter of riser Dps = diameter of principal spillway Eq. 6-11 Dt > (1.4) (Dr) where Dt = diameter of trash rack Dr = diameter of riser Table 6-29.2 D h Dt r Dp Riser Crest EXAMPLE: The peak runoff for a 2-year, 24-hour rain is 32 cfs. Select a pipe size for a head of 12 feet and length of 100 feet. From Table 6-22.1, 38.2 x 0.89 = 34 cfs discharge for a 24-inch diameter pipe. Using Equation 6-10 Using Equation 6-11 36 inch diameter riser 50 inch diameter (Use 54 inch) 36" 34 cfs h 1.2' Determine h - From Table 6-22.2 D Dt Dt r D (1.5) (D ) (1.4) (D ) r r p Dr Q ≥ ≥ ≥ ≥ ≥ ≥ (1.5) (24) (1.4) (36) = = = NOTE: h = minimum distance between the crest of the riser and the crest of the emergency spillway. ---PAGE BREAK--- 6-169 2016 Edition Figure 6-29.4 ---PAGE BREAK--- 6-170 2016 Edition Riser Pipe Diameter (in) Bouoyant Force (lbs / V.F. of Riser Height)1 Volume of Concrete per Vertical Foot of Riser Height (c.f. Needed to Prevent Flotation2 12 18 21 24 30 36 48 54 60 49.0 110.3 150.1 196.0 306.3 441.1 784.1 992.4 1225.2 0.69 1.54 2.10 2.75 4.29 6.18 10.98 13.90 17.16 EXAMPLE: Find the volume of concrete required to stabilize a 24 inch diameter riser 10 feet high. VOL. = (2.75 cu.ft/V.F.) (10 feet) = 27.5 cu. ft. = 1 cu. yd. CONCRETE VOLUME REQUIRED TO PREVENT FLOTATION OF RISER Table 6-29.3 Figure 6-29.5 ---PAGE BREAK--- 6-171 2016 Edition Figure 6-29.6 ---PAGE BREAK--- 6-172 2016 Edition ---PAGE BREAK--- 6-173 2016 Edition DESIGN DATA FOR EARTH SPILLWAYS Table 6-29.4 ---PAGE BREAK--- 6-174 2016 Edition ---PAGE BREAK--- 6-175 2016 Edition TEMPORARY SEDIMENT BASIN DESIGN DATA SHEET EXAMPLE PROBLEM Computed by _ Date Checked _ Date Project Name Independence School, Paradise City Basin No. Total area draining to basin = 18.1 acres Disturbed area draining to basin = 18.1 acres Volume 1. Compute minimum required storage volume (Vs) Vs = 67 cy/ac * 18.1 acres = 1212.7 cy 2. Compute volume of basin at clean-out (Vc) Vc = 22 cy/ac * 18.1 acres = 398.2 cy 3. Determine elevation corresponding to minimum required storage volume, Vs Minimum riser crest elevation = 1052.5 ft (determined by stage/storage relationship) 4. Determine elevation corresponding to clean-out volume, Vc Clean-out elevation = 1051.9 ft (determined by stage/storage relationship) Note: Clean-out elevation shall be clearly marked on the riser or marked by a post near the riser. 5. Compute length of riser Riser length = Minimum elevation of riser crest - Lowest elevation of pipe at riser Riser length = 1052.5 ft - 1050.0 ft Riser length = 2.5 ft Stormwater Runoff 6. Compute peak discharge from a 2-yr, 24-hr storm event. Q2 = 26 cfs (Attach runoff computation sheet.) 7. Compute peak discharge from a 25-yr, 24-hr storm event. Q25 = 46 cfs (Attach runoff computation sheet.) Surface Area/Configuration Design 8. Compute minimum basin surface area (SAmin) SAmin = 0.01 ac/cfs * Q2 SAmin = 0.01 ac/cfs * 26 cfs SAmin = 0.26 ac = 43560 sf/ac * 0.26 ac = 11310 sf 9. Check available area at elevation of riser crest Available area = 18532 sf (determined by stage/storage relationship) Available area > SAmin ? Yes No 10. Compute required length to achieve 2:1 L:W ratio Average width = 80 ft Required length = 2 * average width Required length = 2 * 80 ft Required length = 160 ft Available length = 170 ft 2:1 L:W ratio satisfied? Yes No If no, refer to Figure 6-29.2 for baffle designs. Note any required baffles on E&SC Plan and include calcula-tions and details for baffle(s). Principal Spillway (ps) 11. Determine maximum principal spillway capacity = Q2 = 26 cfs 12. Compute the vertical distance between the centerline of the outlet pipe and the emergency spillway crest H = 9.75 ft 13. Compute the total pipe length of the principal spillway, L, using Figure 6-29.3. L = [A - (B+C)/2 ] [Zu+Zd] + T + E L = 70 ft ---PAGE BREAK--- 6-176 2016 Edition 14. Determine diameter of principal spillway (Dps) and flow through the principal spillway from Table 6-29.1 using H and Q2. Dps = 24 in. Q = 33.1 cfs (value directly from table) 15. Compute actual flow through the principal spillway, using Table 6-29.1 to determine the correction factor for pipe length, L. ps Q = Q * correction factor = 33.1 cfs * 1.00 ps Q = 33.1 cfs 16. Compute riser diameter (Dr) Dr > 1.5 * Dps Dr > 1.5 * 24 in. Dr > 36 in. Dr = 36 in. 17. Compute trash rack diameter (Dt) Dt > 1.4 * Dr Dt > 1.4* 36 in. Dt > 50.4 in. Dt = 54 in. 18. Determine the minimum distance between the riser crest and the emergency spillway crest, h, using Table 6-29.2 Dr, and Qps. h = 1.1 ft Concrete Riser Base Design 19. Determine the volume of concrete per vertical foot of riser height needed (from Table 6-29.3) to prevent flota-tion. Required volume of concrete per vertical foot = 6.18 cf/v.f. 20. Compute total volume of concrete required. Total required volume of concrete = Required volume per vertical foot * Riser length Total required volume of concrete = 6.18 cf/v.f. * 2.5 ft Total volume of concrete required = 15.45 cf 21. Assume base thickness (usually 18”) B = 18 in = 1.5 ft 22. Compute required surface area. Required surface area = Total volume required / B Required surface area = 15.45 cf / 1.5 ft Required surface area = 10.3 sf 23. Compute riser base length and width (assume square base). l = w = (required surface area )1/2 l = w = (10.3 sf)1/2 I = w = 3.21 ft = 12in/ft * 3.21 ft = 39 in. Anti-Seep Collar Design 24. Determine if anti-seep collar is required. If yes to any of the following conditions, a collar is required: The settled height of the dam is greater than 15 feet. The principal spillway diameter (Dps) is smooth pipe larger than The principal spillway diameter (Dps) is corrugated metal pipe larger than 12”. 25. Determine size of anti-seep collar required. 18-inch projection (for heads less than or equal to 10 feet). 24-inch projection (for heads greater than 10 feet). Emergency Spillway (es) 26. Compute minimum capacity of emergency spillway (Qes) es Q = Q25 - Qps = 46 cfs - 33 cfs es Q = 13 cfs 27. Determine stage (Hp), bottom width velocity and minimum exit slope using Table 6-29.4 and Qes. Hp = 0.7 ft b = 10 ft V = 3.2 fps S = 3.5 % 28. Actual entrance channel slope, Se = 5 % 29. Actual exit channel slope, So = 7 % Note: If So is steeper than S (from Table 6-29.4), then the velocity in the exit channel will increase. Calculate exit velocity (Vo) ---PAGE BREAK--- 6-177 2016 Edition Vo = V (So 0.3 = 3.8 fps / 35) 0.3 Vo = 4.7 fps Note: Refer to Channel Stabilization (Ch) to determine the proper lining for the emergency spillway. Grass Rip-rap Concrete Design Elevations 30. Riser crest elevation = 1052.5 ft 31. Compute minimum emergency spillway crest elevation Minimum emergency spillway crest elevation = Riser crest elevation + h Minimum emergency spillway crest elevation = 1052.5 ft + 1.1 ft Minimum emergency spillway crest elevation = 1053.6 ft Actual emergency spillway crest elevation = 1053.6 ft 32. Determine design high water elevation Design high water elevation = Emergency spillway crest elevation + Stage elevation (Hp) Design high water elevation = 1053.6 ft + 0.9 ft Design high water elevation = 1054.5 ft 33. Determine elevation of top of dam Elevation of top of dam = Design high water elevation + 1 ft freeboard Elevation of top of dam = 1054.5 ft + 1 ft Elevation of top of dam = 1055.5 ft ---PAGE BREAK--- 6-178 2016 Edition ---PAGE BREAK--- 6-179 2016 Edition TEMPORARY SEDIMENT BASIN DESIGN SHEET Computed by _ Date Checked _ Date Project Name Basin No. Total area draining to basin = Disturbed area draining to basin = Volume 1. Compute minimum required storage volume (Vs). Vs = 67 cy/ac * acres = cy 2. Compute volume of basin at clean-out (Vc). Vc = 22 cy/ac * acres = cy 3. Determine elevation corresponding to minimum required storage volume, Vs. Minimum riser crest elevation = ft (determined by stage/storage relationship) 4. Determine elevation corresponding to clean-out volume, Vc. Clean-out elevation = ft (determined by stage/storage relationship) Note: Clean-out elevation shall be clearly marked on the riser or marked by a post near the riser. 5. Compute length of riser. Riser length = Minimum elevation of riser crest - Lowest elevation of pipe at riser Riser length = ft - ft Riser length = ft Stormwater Runoff 6. Compute peak discharge from a 2-yr, 24-hr storm event. Q2 = cfs (Attach runoff computation sheet.) 7. Compute peak discharge from a 25-yr, 24-hr storm event. Q25 = cfs (Attach runoff computation sheet.) Surface Area/Configuration Design 8. Compute minimum basin surface area (SAmin). SAmin = 0.01 ac/cfs * Q2 SAmin = 0.01 ac/cfs * cfs SAmin ac = 43560 sf/ac ac = sf 9. Check available area at elevation of riser crest. Available area = sf (determined by stage/storage relationship) Available area SAmin? Yes No 10. Compute required length to achieve 2:1 L:W ratio. Average width = ft Required length = 2 * average width Required length = 2 ft Required length = ft Available length = ft 2:1 L:W ratio satisfied? Yes No If “no”, refer to Figure 6-29.2 for baffle designs. Note any required baffles on E&SC Plan and include calculations and details for baffle(s). Principal Spillway (ps) 11. Determine maximum principal spillway capacity. Qmax = Q2 cfs 12. Compute the vertical distance between the centerline of the outlet pipe and the emergency spillway crest H = ft 13. Compute the total pipe length of the principal spillway, L, using Figure 6-29.3. L = [A - (B+C)/2 ] [Zu+Zd] + T + E = [ ( [ + + L = ft ---PAGE BREAK--- 6-180 2016 Edition 14. Determine diameter of principal spillway (Dps) and flow through the principal spillway from Table 6-29.1 using H and Qmax. Dps = in. Q cfs (value directly from table) 15. Compute actual flow through the principal spillway, using Table 6-29.1 to determine the correction factor for pipe length, L. ps Q = Q * correction factor = cfs * ps Q = cfs 16. Compute riser diameter (Dr). Dr = 1.5 * Dps Dr = 1.5 * in. Dr = in. Dr = in. 17. Compute trash rack diameter (Dt). Dt = 1.4 * Dr Dt = 1.4* in. Dt = in. Dt = in. 18. Determine the minimum distance between the riser crest and the emergency spillway crest, h, using Table 6-29.2 Dr, and Qps. h = ft Concrete Riser Base Design 19. Determine the volume of concrete per vertical foot of riser height needed, from Table 6-29.3 to prevent flotation. Required volume of concrete per vertical foot = cf/v.f. 20. Compute total volume of concrete required. Total required volume of concrete = Required volume per vertical foot * Riser length Total required volume of concrete = cf/v.f. ft Total volume of concrete required = cf 21. Assume base thickness, B (usually 18”). B = in = ft 22. Compute required surface area. Required surface area = Total volume required / B Required surface area = cf / ft Required surface area = sf 23. Compute riser base length and width (assume square base). l = w = (required surface area )1/2 l = w = sf)1/2 l = w = ft = 12in/ft* ft = in Anti-Seep Collar Design 24. Determine if anti-seep collar is required. If yes, to any of the following conditions, a collar is required: The settled height of the dam is greater than 15 feet. The principal spillway diameter (Dps) is smooth pipe larger than The principal spillway diameter (Dps) is corrugated metal pipe larger than 12”. 25. Determine size of anti-seep collar required. 18-inch projection (for heads less than or equal to 10 feet). 24-inch projection (for heads greater than 10 feet). Emergency Spillway (es) 26. Compute minimum capacity of emergency spillway (Qes) Qes = Q25 - Qps = cfs cfs Qes = cfs TEMPORARY SEDIMENT BASIN DESIGN SHEET Project Name Page 2 ---PAGE BREAK--- 6-181 2016 Edition 27. Determine stage (Hp), bottom width velocity and minimum exit slope using Table 6-29.4 and Qes. Hp = ft b = ft V = fps S = 28. Actual entrance channel slope, Se = % 29. Actual exit channel slope, So = % Note: If So is steeper than S (from Table 6-29.4), then the velocity in the exit channel will increase. Calculate new exit velocity (Vo) Vo = V (So/S) 0.3 = fps * 0.3 Vo = fps Note: Refer to Channel Stabilization (Ch) to determine the proper lining for the emergency spillway. Grass Rip-rap Concrete Design Elevations 30. Riser crest elevation = ft 31. Compute minimum emergency spillway crest elevation. Minimum emergency spillway crest elevation = Riser crest elevation + h Minimum emergency spillway crest elevation = ft + ft Minimum emergency spillway crest elevation = ft 32. Determine design high water elevation Design high water elevation = Minimum emergency spillway crest elevation + Stage elevation (Hp) Design high water elevation = ft + ft Design high water elevation = ft 33. Determine elevation of top of dam Elevation of top of dam = Design high water elevation + 1 ft freeboard Elevation of top of dam = ft + 1 ft Elevation of top of dam = ft PLEASE NOTE THAT DESIGN VALUES DETERMINED BY THIS SHEET REPRESENT THE MINIMUM REQUIREMENTS FOR A TEMPORARY SEDIMENT BASIN. TEMPORARY SEDIMENT BASIN DESIGN SHEET Project Name Page 3 ---PAGE BREAK--- 6-182 2016 Edition ---PAGE BREAK--- 6-183 2016 Edition Figure 6-29.7 ---PAGE BREAK--- 6-184 2016 Edition Figure 6-29.8 ---PAGE BREAK--- 6-185 2016 Edition Temporary Sediment Trap Sd4 DEFINITION A small temporary pond that drains a dis­ turbed area so that sediment can settle out. The principle feature distinguishing a temporary sedi­ ment trap from a temporary sediment basin is the lack of a pipe or riser. PURPOSE To collect and store sediment from uphill sites cleared and or graded during construction. Intended for use on small tributary areas with no unusual drainage features. Effective against coarse sediment, but not against silt or clay par­ ticles that remain suspended. CONDITIONS Temporary sediment traps are constructed early in the construction process at locations that will require minimal clearing and grading. Natural draws or swells are favorable locations to build the traps. They should be easily acces­ sible for frequent maintenance and inspections. Temporary sediment traps shall never be placed in live streams. DESIGN CRITERIA Design and construction shall comply with laws, ordinances, rules and regulations on the local, state and federal level. The total drainage area of a temporary sedi­ ment trap is up to 5 acres, depending on type of construction. The height of a temporary sediment trap em­ bankment shall not exceed 5.5 feet as measured from the toe of slope to the top of the berm. Top width of an embankment shall be at least as wide as the height of the sediment trap embankment, with a minimum width of 3 feet. Maximum pond depth of a sediment trap is 4 feet as measured from the bottom of the trap to the invert of the emergency spillway. Slopes shall not exceed 2:1 (H:V) for excavated areas and for compacted embankments. Side slopes should be (3:1) or flatter allowing people and equipment to safely negotiate slopes or to enter the sediment trap. The length to width ratio must be greater than (2:1) (L:W) for the principal flowpaths in order to maximize residence time of stormwater within the sediment trap. Baffles may be required to prevent short-circuiting of the flow. A typical baffle design uses 4’x8’ sheets of exterior grade plywood 1/2 inch thick, mounted on 4”x4” hardwood posts. Volume Minimum volume of a temporary sediment trap shall be 67 cubic yards per acre for the total drainage area. The volume shall be measured at an elevation equivalent to the spillway invert. Volume of a temporary sediment trap in heav­ ily disturbed areas should be 134 cubic yards per acre for the total drainage area. This includes an upper area with a minimum of 67 cubic yards per acre drained, which is dewatered using one of the outlet design methods provided, and a lower wet zone for sediment storage and settling. The volume should be calculated from existing and proposed contours, or by measured cross sections. An approximate method for calculating the volume of traps using a natural draw is: V = 0.4 x A x D V = Sediment storage volume (below invert of emergency spillway) A = Surface area (at level of emerency spillway) D = Maximum depth (from emergency spillway invert) The cleanout volume for a temporary sediment trap is 1/3 of the total storage volume. Cleanout volume shall be calculated and marked with a stake at the outlet of the trap. ---PAGE BREAK--- 6-186 2016 Edition CONSTRUCTION SPECIFICATIONS The basic design guidlines are applicable to the type of temporary sediment trap constructed. The main differences are with regards to the type of outlet structures. The following types of con­ struction are acceptable under the designated conditions: Overflow (Sd4-A) An overflow temporary sediment trap is lim­ ited to small areas less than 1 acre, typically with gentle slopes (1 or 2 percent) and without major grading operations. The maximum life span of an overflow trap is 6 months. If water enters the trap with very low velocities, the same amount of water will be slowly displaced and leave the other end of the sediment trap. Silt fence, straw bale barriers or grass filter strips are used to “polish” the overflow water as it leaves the sediment trap. See Figure 6-30.1 Combination Straw Bale and Silt Fence Outlet (Sd4-B) The combination outlet uses straw bales and silt fence to dewater the sediment trap. Proper installation and staking of the straw bales, and wire backing on the silt fence are required for the materials to resist 1 foot or more of ponded water. The combination straw bale and silt fence outlet is limited to 1 acre total drainage area, and has a life span of less than 1 year. This type of outlet requires frequent maintenance and adjust­ ments to ensure the released stormwater is free from sediment. See Figure 6-30.2 Rock Outlet (Sd4-C) The rock outlet relies on filtering through layers of aggregate, rock or riprap material to dewater the sediment trap. It is the sturdiest of the sediment trap designs and generally requires less maintenance. It can be used for drainage area up to 5 acres and has a life span of 1 year. See Figure 6-30.3 Emergency Spillway The emergency overflow outlet of a temporary sediment trap must be stabilized with rock, geo­ textile, vegetation, or another suitable material that is resistant to erosion. It must be installed to safely convey stormwater runoff for the 10-year storm event. REFERENCE: City of Knoxville BMP Manual Best Management Practices, Knoxville, TN, May 2003 ---PAGE BREAK--- 6-187 2016 Edition Figure 6-30.1 ---PAGE BREAK--- 6-188 2016 Edition Figure 6-30.2 ---PAGE BREAK--- 6-189 2016 Edition Figure 6-30.3 ---PAGE BREAK--- 6-190 2016 Edition ---PAGE BREAK--- 6-191 2016 Edition DEFINITION A floating surface skimmer is a buoyant de­ vice that releases/drains water from the surface of sediment ponds, traps or basins at a con­ trolled rate of flow. It “skims”, or dewaters, from the water surface where sediment concentrations are at a minimum in the water column instead of draining from the bottom where sediment con­ centrations are their highest, and drains to a riser or the backside of a dam. Floating surface skimmers release a low rate of flow, draining the basin slowly at a nearly constant rate. The inlet of the skimmer device is sized according to the basin volume and de­ signed to drain the basin in a fixed amount of time. Traditional sediment basin outlet designs use a perforated riser for dewatering, which al­ lows water to leave the basin from all depths. PURPOSE •To discharge clearer water from the surface of a sediment pond, trap or basin at a relatively uniform rate, rather than the more turbid and sediment-laden water from lower depths that is discharged through a traditional perforated riser. •To reduce the retention time associated with meeting a desired water quality standard for discharge from a sediment pond, trap or basin. CONDITIONS The current principal spillway of most sedi­ ment basins is a vertical riser pipe. Water dis­ charges through 1/2 inch perforated holes in the bottom half of the riser. Holes at lower elevations discharge water that has a high turbidity value. The bottom half of the riser is typically covered with 2 feet of ½- to ¾-inch gravel. Over time, the gravel filter surrounding the riser is coated with sediment that traps and detains water in the basin. This reduces the storage capacity for incoming runoff. Sediment in the trapped water is re-suspended with each new inflow, and never has the opportunity to settle to the bottom. DESIGN CRITERIA A surface skimmer (Sk) replaces the riser pipe as the principal spillway, but DOES NOT REPLACE THE EMERCENCY OVERFLOW SPILLWAY. The skimmer only drains the basin from the crest of the emergency overflow spill­ way down to the bottom. Its flow capacity is too small to accommodate extreme storm events that exceed the available storage capacity, so an emergency spillway is required. When rainfall events occur, the water level in the basin rises. Under the influence of gravity, sediment settles slowly toward the bottom, leav­ ing clearer water at the surface. The skimmer floats at the surface as the water surface rises and discharges the cleaner water at a relatively uniform rate. By draining from the surface a skimmer can immediately begin removing rela­ tively clear water from the pond, trap or basin, and thereby reduce the retention time to obtain similarly clear discharge using traditional outlets. Product Designs One end of a rigid tube is connected to the barrel of the discharge system via a flexible coupling. The other end of the tube floats at the water surface. The flexible coupling allows the rigid tube to articulate as the water level changes. A screen at the inlet prevents floating trash from entering the tube. Each product (and each product size) has a unique design, includ­ ing the associated hydraulics that are affected by the floatation, inlet, and connecting tube/coupling designs chosen. The discharge rate is dependent on the specific product design and can only be determined through product-specific testing as discussed in Addendum A. Dewatering Rates. Skimmers come in several sizes to accommo­ Floating Surface Skimmer Sk ---PAGE BREAK--- 6-192 2016 Edition date a range of flows. The plans shall indicate a volume to be drained in a specified time period. A skimmer is then selected to satisfy this require­ ment. Addendum B presents a typical skimmer selection table based on product-specific testing in accordance with Addendum A. Floatation Requirements Floating surface skimmers that sink or com­ pletely suspend under the water surface are not acceptable. A portion of the skimmer must be visible above the water surface at all times. The location of the floating “headworks” relative to the water surface, and the size and location of vents and inlets, must be the same as when the prod­ uct was tested for flow rates. This should be veri­ fied and documented as inherent to the product design during flow testing. Trash Guard & Maintenance Rope All Floating surface skimmer designs include a trash guard and maintenance rope in order to prevent and remove blockage from floating debris. Trash guards prevent larger debris from entering the skimmer that may cause internal blockage. The maintenance rope is used to remove trash and debris that accumulates on the outside of the trash guard. Ensure the mainte­ nance rope is floatable. Skimmer Pit Excavate a shallow pit filled with riprap under the floating surface skimmer to account for sediment that accumulates on the sediment basin bottom around the skimmer. The pit allows the skimmer to completely drain the basin. At a minimum, the pit has dimensions of 4ft x 4ft with a minimum depth of 2 ft. Ensure the bottom of the pit is lower than the invert of the outlet bar­ rel from the riser. Floating Skimmers that have a footed design that prevents the device from lodging in accumulated sediment do not require a skimmer pit. CONSTRUCTION SPECIFICATIONS Materials Use floating surface skimmers made of PVC (Schedule 40 or greater) or other appropriate materials. Quality Assurance Each skimmer must have documented identi­ fication, including but not limited to the following: • Manufacturer’s name and location. • Manufacturer’s telephone number and fax number. • Manufacturer’s e-mail and web address. • Skimmer name, model, and/or serial number. • Skimmer dimensions. • Certification that the skimmer meets the physical and performance criteria of this specification. Installation Install the device according to the manufacturer’s instructions. Additional Information A shut-off valve to facilitate skimmer main­ tenance or emergency regulation of the flow discharge rate, installed at the discharge end of the barrel as it exits the embankment is recom­ mended. (Normal skimmer operation is to be based on the “full open” valve setting.) A storm drain outlet protection device shall be installed at the barrel discharge point. MAINTENANCE Inspect Floating Skimmers together with the Sediment Basin inspections. Inspect the floating surface skimmer for any structural dam­ age, clogging, or excessive sediment accumula­ tion. While draining the basin, the trash guard of the skimmer may clog with debris. Typically, a Figure 6-31.1. Floating skimmer of a different design. ---PAGE BREAK--- 6-193 2016 Edition few jerks on the maintenance rope will clear the skimmer of debris and restore flow. If jerking the maintenance rope does not work, pull the skim­ mer to the embankment with the maintenance rope and manually remove all debris from the trash guard. An internal clog or blockage may require the device to be disassembled and re­ paired. If the skimmer becomes stuck in the mud at the bottom of the basin it must be freed to allow for normal operation. This can typically be done by use of the maintenance rope. Remove sediment deposits from the basin when approximately one-third of the storage volume has been lost to sediment accumulation or when the floating skimmer cannot settle low enough to drain the entire basin. Remove or pull the skimmer to a side embankment using the maintenance rope and remove sediment from the skimmer pit. Floating “Headworks” Supporting Inlet Rigid Tube Flexible Coupling Figure 6-31.2. Skimmer Components TO BE SHOWN ON THE EROSION, SEDIMENTATION AND POLLUTION CONTROL PLAN When a FLOATING SURFACE SKIMMER is used, show the following information along with each sediment pond, trap or basin being used on the site: 1. Pond, trap or basin size, length* (top and bottom) width* (top and bottom) and depth = 2. Time to Drain (hrs) = 3. Skimmer Dimensions (orifice and head 4. Manufacturer’s *feet, inches Addendum A: Procedure for Measurement of Floating Pond Skimmer Flow Rate This procedure is for evaluating the flow rate of a floating pond skimmer vs. pond depth, including details for setting up a performance test that can be used for design characteriza- tion as well as quality assurance to determine product conformance to project specifications. Procedure a. Apparatus/Facility i. Testing is performed in a calibrated basin (i.e. it has a known surface area at any known depth.) ii. The basin shall be at least 40-ft long x 6-ft wide x 4-ft deep. iii. The basin shall be outfitted with discharge pipe having a diameter no smaller than that of the pipe joining to the floating skimmer head. The discharge pipe shall have a valve that can be controlled from the outside of the basin to initiate ---PAGE BREAK--- 6-194 2016 Edition d. Test Data: i. Record and tabulate water surface eleva- tion as a function of time. ii. From the change in surface elevation with time, compute the flow rate and report it at the average of the associated elevations. Addendum B: Selecting a Skimmer It is a straight forward process to choose the skimmer that best matches the required “time- to-drain” specified for a project. The volume (or dimensions) of the sediment pond, trap, or basin must be known, as well as, the number of days to drain the basin. With this information, a draw­ down rate calculation is made for each product and sized using the product-specific flow rates determined in accordance with Addendum A. Figure 6-31.3, shows a typical spreadsheet set up to make this calculation. This spread­ sheet lets the user input the pond dimensions and depth, as well as the time-to-drain require­ ment, and then calculates the time in hours that it would take for each skimmer size (and orifice size) to completely drain the pond. As different style skimmers are made from a wide variety of parts, including different diameter pipe components in the same device, it is gener­ ally agreed that the skimmer size is defined by the “rigid tube” diameter connecting the floating/ intake components to the (larger) flexible cou­ pling and outlet pipe. and stop flow through the skimmer. It is also recommended to have a second valved discharge pipe to enable lower- ing of the water surface within the basin if desired to take flow rate measure- ments at various depths without waiting for drainage exclusively through the skimmer. iv. A water supply along with an associated pump and piping is needed to fill the cali -brated basin. A calibrated ruler shall be mounted on the side of the basin to al low depth to be read. This calibrated ruler must not be moved, repositioned, jarred, or tampered with once the first reading of each replicate has been taken. b. Test Set-Up i. The test basin shall be watertight with at least one discharge pipe at least as large as the pipe that connects to the floating skimmer head. The discharge pipe shall have an accessible valve to control flow. ii. The skimmer is attached to the discharge pipe prior to pond filling using reducers/ connectors as directed by the client. The connection must be watertight so that all drainage is through the floating skimmer headworks/inlet. c.Test Operation and Data Collection: i. With the valve on the discharge pipe closed, and the skimmer to be tested in place, fill the test basin with water to the maximum desired depth. Filling should pro- ceed slowly enough to allow all air within the skimmer assembly to bleed completely during filling. ii. Once the basin is filled to the desired depth, allow the water surface to become still and record the depth on the ruler mounted to the sidewall. iii. Simultaneously open the discharge pipe valve and start timing. iv. As the water is discharged from the test basin through the floating skimmer, periodi cally record depth and associated time. ---PAGE BREAK--- 6-195 2016 Edition Figure 6-31.3 72 40833.33 4 305433.3 125 20 125 2.4 75 75 Water Level Depth, in. Avg. Water Level Depth, in. Incr. Depth, in L W Incr. Dis‐ charge, ft3 Cumm. Dis‐ charge, ft3 Cumm. Dis‐ charge, gal % of Total Volume Dis‐ charged Skimmer Flow Rate, gal/min Cumm. Drain Time, hrs. Skimmer Flow Rate, gal/min Cumm. Drain Time, hrs. Skimmer Flow Rate, gal/min Cumm. Drain Time, hrs. Skimmer Flow Rate, gal/min Cumm. Drain Time, hrs. Skimmer Flow Rate, gal/min Cumm. Drain Time, hrs. Skimmer Flow Rate, gal/min Cumm. Drain Time, hrs. Skimmer Flow Rate, gal/min Cumm. Drain Time, hrs. 48 125 125 45.6 46.8 2.4 [PHONE REDACTED] 3063 22911 7.5% 12 31 30 13 53 7 90 4 107 4 236 2 457 1 43.2 44.4 2.4 [PHONE REDACTED] 6003 44905 14.7% 12 62 29 26 52 14 89 8 105 7 233 3 445 2 40.8 42 2.4 [PHONE REDACTED] 8824 66002 21.6% 12 92 28 38 51 21 88 12 103 10 231 5 433 2 38.4 39.6 2.4 [PHONE REDACTED] 11527 86219 28.2% 12 121 27 51 51 28 87 16 101 14 228 6 420 3 36 37.2 2.4 [PHONE REDACTED] 14115 105577 34.6% 11 149 26 63 50 34 86 20 99 17 225 8 407 4 33.6 34.8 2.4 [PHONE REDACTED] 16590 124093 40.6% 11 177 25 75 49 41 85 24 97 20 222 9 393 5 31.2 32.4 2.4 [PHONE REDACTED] 18955 141787 46.4% 11 204 24 88 48 47 84 27 94 23 219 10 379 6 28.8 30 2.4 [PHONE REDACTED] 21213 158676 52.0% 11 230 23 100 47 53 83 31 92 26 216 12 364 6 26.4 27.6 2.4 [PHONE REDACTED] 23366 174780 57.2% 10 256 22 112 46 58 82 34 89 29 212 13 349 7 24 25.2 2.4 [PHONE REDACTED] 25417 190117 62.2% 10 282 21 124 45 64 81 37 86 32 209 14 333 8 21.6 22.8 2.4 98 98 1950 27367 204706 67.0% 10 306 20 136 44 70 79 40 83 35 204 15 316 9 19.2 20.4 2.4 95 95 1853 29220 218566 71.6% 9 331 19 148 42 75 78 43 80 38 200 16 299 9 16.8 18 2.4 93 93 1758 30978 231715 75.9% 9 355 17 161 41 81 76 46 77 41 195 18 280 10 14.4 15.6 2.4 90 90 1665 32643 244172 79.9% 9 379 16 174 39 86 74 49 73 44 190 19 261 11 12 13.2 2.4 88 88 1575 34219 255956 83.8% 8 403 15 187 38 91 72 51 69 47 184 20 239 12 9.6 10.8 2.4 85 85 1488 35707 267086 87.4% 8 427 13 201 36 96 69 54 64 50 176 21 216 13 7.2 8.4 2.4 83 83 1403 37110 277580 90.9% 7 451 11 216 33 102 66 57 59 53 168 22 190 14 4.8 6 2.4 80 80 1320 38430 287456 94.1% 6 477 10 234 30 107 63 59 52 56 157 23 160 15 2.4 3.6 2.4 78 78 1240 39670 296735 97.2% 5 505 7 255 26 113 57 62 44 59 142 24 123 16 0 1.2 2.4 75 75 1163 40833 305433 100.0% 4 542 4 292 20 120 47 65 30 64 114 25 70 18 Pond Bottom Length, ft = Pond Bottom Width, ft = Example Shown : 125 ft x 125 ft x 4 ft deep pond; Drainage Time < 72 hours Inputs Calculations Depth Increments for Calcs, in. = Time to Drain, hrs = Pond Depth, ft = Pond Top Length, ft = Pond Top Width, ft = Calculated Pond Volume, ft 3 = Calculated Pond Volume, gal = No. of Depth Increments for Calcs, in. = Flow Rate: Flow Rate: Skimmer Sizing Table 7.9914*depth 0.3116 Flow Rate: Type 1: 1.5 / 0.00 Type 1: 2.0 / 0.00 Flow Rate: 13.985*depth 0.5514 Type 1: 3.0 / 0.00 Flow Rate: 36.676*depth 0.2702 Type 3: 3.0 / 0.00 Flow Rate: 70.714*depth 0.1747 Type 1: 4.0 / 0.00 Type 1: 6.0 / 0.00 Note: Equations are from product testing: Type 3: 6.0 / 0.00 227.83*depth 0.5118 180.07*depth 0.1981 66.588*depth 0.3494 Skimmer Size Selection Optimization Skimmer Size, in / Orifice Size, in Flow Rate: Type 1: 6.0 / 0.00 Type 3: 6.0 / 0.00 Lowest depth that can still drain through skimmer. Skimmer / Orifice Combinations with Sufficient Flow: Type 3: 3.0 / 0.00 no no no Type 1: 4.0 / 0.00 ---PAGE BREAK--- 6-196 2016 Edition Figure 6-31.4 ---PAGE BREAK--- 6-197 2016 Edition Seep Berm SpB DEFINITION A seep berm is a linear control device con­ structed as a diversion perpendicular to the direction of the runoff to enhance dissipation and infiltration of runoff, while creating multiple sedimentation chambers with the employment of intermediate dikes. PURPOSE To allow the 2 year storm event, 24 hour de­ sign storm to seep out while allowing larger flows to be diverted to a sediment storage area. CONDITIONS Seep berms should be installed where runoff can be stored behind the seep berm without damaging the berm or submerged area behind the intermediate dike points. Seep berms are usually employed down-gradient of construction sites near the boundary of development. This standard applies under the following condi­ tions: 1.Seep berms shall not be used above fill slopes that have not achieved permanent stabilization meeting the definition of final stabilization. 2.Seep berms shall be designed by the design professional for use on a site. Seep berms shall not be installed across streams, ditches, waterways, or other concen­ trated flow areas. DESIGN CRITERIA The seep berm shall have a minimum width of 12 inches across the top of berm and shall not be taller than 4 feet in height. The top of berm may vary or stay constant. The storage area should be identified (shaded) on the plans. Two or more intermediate dikes in a series shall be used for drainage areas greater than one acre. Maximum spacing between dikes should be such that the toe of the upstream dike is at the same elevation as the top of the down­ stream dike. Intermediate dikes shall pass the 25-year storm event. If a fill berm is utilized it is very important that it has proper compaction and receives the proper stabilization. Fill berms should be stabilized with a slope stabilization meeting the c-factor. Sta­ bilization and applying seed at 70% germination or better shall occur prior to other land disturbing activities taking place in the drainage basin. Berm storage volumes can be figured as a function of berm height and watershed gradient. The volumes shall be calculated using 67 cubic yards per acre drained to the berm. Detailed calculations shall be shown on the plans when using the seep berms for sediment storage. If a berm encounters different gradients then it should be calculated using the steepest slope in that run, existing or proposed. Clean out markers must be placed at each intermediate dike using a sediment storage calculation. When the berms remain in place they may be utilized as a walking trail, etc. CONSTRUCTION SPECIFICATIONS Seep berms are readily constructed using typ­ ical on-site construction equipment. The earthen berm shall be compacted. This can be easily done through tracking by a skid-loader with a full bucket, tracking with a dozer and applying pres­ sure with the bucket of a track hoe or rubber tired backhoe (min. 90% std.protor test). Three general options are applicable for seep placement. 1. Seeps can be placed during the construc- tion of the berm, but then care must be exerted when compacting above the seeps. 2. After the entire berm has been constructed, excavation at the location of the seeps can ---PAGE BREAK--- 6-198 2016 Edition be conducted, seeps placed in the trench and back-filled, and the berm compacted above the seeps. 3.Completely build the earthen berm with proper compaction and then using a steel pipe with a conical end insert pipes through the berm. MAINTENANCE Inspect the drain from the seep and supporting berm after every half inch rainfall event or greater, or weekly depending on envi­ ronmental conditions. make necessary repairs. The seep berms shall have the sedi­ ment removed when sediment accumulates to one-third the height of the intermediate dike or before. ---PAGE BREAK--- 6-199 2016 Edition Figure 6-32.1 Integrated Seep Berm Erosion Control System ---PAGE BREAK--- 6-200 2016 Edition TO BE SHOWN ON THE EROSION, SEDIMENTATION AND POLLUTION CONTROL PLAN A. Top of Berm Elevation________ft B. Bottom of Berm Elevation________ft C. Top of Berm Width D. Height of the E. Seep Hole Diameter__________ft F. Distance from the the Top of the Seep to be Placed in Accordance with the 2yr-24hr storm G. Type of Seep (circle one) PVC Metal H. Spacing of Seep Along the References Dirt II Technical Panel Completion Report, Repairing the Chattahoochee. (2001). Chattahoochee-Flint Regional Development Center, Franklin, GA. http://www.gaepd.org/Documents/techguide_wpb.html#es Strun, T.W., Warner, R.C., Torrealba,S., and Hamade,F. (2008). Demonstration of a Performanced-Based System of Storm Water and Erosion Controls on Small Residen­ tial/Commercial Sites in the Georgia Piedmont. Final Report submitted to Georgia EPD, Project751-40101. Warner,R., Schwab,P.J., and Marshall, D.J. (1998). SEDCAD 4 Design Manual and User’s Guide. Civil Software Design. Breedlove,M.W., Breedlove Land Planning Inc. Seep Berm Installation. Personal Interview April, 2013. Warner,R.C., Strum,T.W., Torrealba,S. (2007). Seep Berm Design Manual. Final Report submitted to Georgia EPD and U.S. Environmental Protection Agency, Atlanta, GA ---PAGE BREAK--- 6-201 2016 Edition DEFINITION A temporary structure installed across a flow­ ing stream or watercourse for use by construc­ tion equipment. PURPOSE This standard provides a means for construc­ tion vehicles to cross streams or watercourses without moving sediment into streams, damaging the streambed or channel, or causing flooding. CONDITIONS Temporary stream crossings should not be used on streams with drainage areas greater than one square mile, unless specifically de­ signed to accommodate the additional drainage area by the design professional. A certification statement and signature shall accompany the design. Structures may include bridges, round pipes or pipe arches. Temporary stream crossings should be in place for less than one year and should not be used by the general public. DESIGN CRITERIA Size The structure shall be large enough to convey the full bank flow of the stream, typically flows produced by a 2-year, 24-hour frequency storm, without appreciably altering the stream flow char­ acteristic. Location The temporary stream crossing shall be perpendicular to the stream. Where approach conditions dictate, the crossing may vary 15% from the perpendicular. Overflow Protection Structures shall be protected from washout during periods of peak discharges by divert­ ing water around the structures. Methods to be considered for washout protection may include elevation of bridges above adjacent flood plain lands, crowning of fills over pipes, or by the use of diversions, dikes or island type structures. Two types of stream crossings that may be used are bridges and culverts. Frequency and in­ tended use, stream channel conditions, overflow areas, potential flood damage, and surface runoff control should be considered when selecting the type of temporary stream crossing to be used. Temporary Bridge Crossing A temporary access bridge causes the least erosion of the stream channel crossing when the bridge is installed and removed. It also provides the least obstruction to flow and fish migration. Provided that the bridge is properly designed and appropriate materials are used, a temporary access bridge will be long-lasting and will require little maintenance. However, it is generally the most expensive crossing to design and con­ struct, creating the greatest safety hazard if not adequately designed, installed and maintained. Temporary Culvert Crossing A temporary access culvert can control ero­ sion effectively, but can cause erosion when it is installed and removed. It is the most common stream crossing. A temporary culvert can be easily constructed and enables heavy equipment loads to be used. However, culverts create the greatest obstruction to flood flows and are sub­ ject to blockage and washout. Table 6-33.1 shall be used to determine the cul­ vert size necessary to safely convey streamflow. Temporary Stream Crossing Sr Sr-B Sr-C ---PAGE BREAK--- 6-202 2016 Edition Please note that the required pipe size is based on cross-sectional area of the pipe; e.g. if a 24 inch pipe is prescribed by Table 33.1, two 12 inch pipes could not be substituted because less flow area is provided. CONSTRUCTION SPECIFICATIONS All Crossings 1. Clearing of the stream bed and banks shall be kept to a minimum. 2. All surface water from the construction site shall be diverted onto undisturbed areas adjoining the stream. Line unstable stream banks with riprap or otherwise appropriately stabilize them. 3. The structure shall be removed as soon as it is no longer necessary for project construc­ tion. 4. Upon removal of the structure, the stream shall immediately be restored to its original cross-section and properly stabilized. Temporary Bridge Crossing 1. The temporary bridge shall be constructed at or above bank elevation to prevent the entrapment of floating materials and debris. 2. Abutments shall be placed parallel to and on stable banks. 3. Bridges shall be constructed to span the entire channel. If the channel width exceeds eight feet (as measured from the tops of the banks), a footing, pier or bridge support may be constructed within the waterway. 4. Bridges shall be securely anchored at only one end using steel cable or chain. This will prevent channel obstruction in the event that floodwaters float the bridge. Large trees, large boulders, or driven steel anchors can serve as anchors. Temporary Culvert Crossing 1. The invert elevation of the culvert shall be installed on the natural streambed grade. 2. The culvert(s) shall extend a minimum of one foot beyond the upstream and toe of the aggregate placed around the cul­ vert. In no case shall the culvert exceed 40 feet in length. 3. The culvert(s) shall be covered with a minimum of one foot of aggregate. If multiple culverts are used, they shall be separated by a minimum of 12 inches of compacted aggregate fill. MAINTENANCE The structure shall be inspected after every rainfall and at least once a week, whether it has rained or not, and all damages repaired im­ mediately. The structure shall be removed im­ mediately after construction is finished, and the streambed and banks must be stabilized. Refer to specification Bf - Buffer Zone. Table 6-33.1. Corrugated Metal Pipe (CMP) Diameters For Temporary Stream Crossings a Drainage Area Average Slope of Watershed (Acres) 1% 4% 8% 16% 1-25 24 24 30 30 26-50 24 30 36 36 51-100 30 36 42 48 101-150 30 42 48 48 151-200 36 42 48 54 201-250 36 48 54 54 251-300 36 48 54 60 301-350 42 48 60 60 351-400 42 54 60 60 401-450 42 54 60 72 451-500 42 54 60 72 501-550 48 60 60 72 551-600 48 60 60 72 601-640 48 60 72 72 a Assumptions for determining the table: USDA-NRCS Peak Discharge Method; CN = 65; Rainfall depth (average for Georgia) = 3.7” for 2-year frequency. Pipe diameters shown in the table are in inches. Sr-C Sr-B ---PAGE BREAK--- 6-203 2016 Edition TO BE SHOWN ON THE EROSION AND SEDIMENT CONTROL PLAN 1. Drainage area (ac), average slope of watershed and stream flow rate at bankfull flow (cfs). 2. Detailed dimensions of components for the type of crossing to be used. ---PAGE BREAK--- 6-204 2016 Edition Figure 6-33.1 Temporary Stream Crossing ---PAGE BREAK--- 6-205 2016 Edition Figure 6-33.2 ---PAGE BREAK--- 6-206 2016 Edition ---PAGE BREAK--- 6-207 2016 Edition DEFINITION Paved and/or riprapped channel sections, placed below storm drain outlets. PURPOSE To reduce velocity of flow before entering receiving channels below storm drain outlets. CONDITIONS This standard applies to all storm drain out­ lets, road culverts, paved channel outlets, etc., discharging into natural or constructed channels. Analysis and/or treatment will extend from the end of the conduit, channel or structure to the point of entry into an existing stream or publicly maintained drainage system. DESIGN CRITERIA Structurally lined aprons at the outlets of pipes and paved channel sections shall be de­ signed according to the following criteria: Capacity Peak stormflow from the 25-year, 24-hour frequency storm or the storm specified in Title 12-7-1 of the Official Code of Georgia Annotated or the design discharge of the water conveyance structure, whichever is greater. Tailwater Depth The depth of tailwater immediately below the pipe outlet must be determined for the design capacity of the pipe. Manning’s Equation may be used to determine tailwater depth. If the tailwater depth is less than half the diameter of the outlet pipe, it shall be classified as a Minimum Tailwater Condition. If the tailwater depth is greater than half the pipe diameter, it shall be classified as a Maximum Tailwater Condition. Pipes that outlet onto flat areas with no defined channel may be assumed to have a Minimum Tailwater Condition. Apron Length and Thickness The apron length and d50, stone median size, shall be determined from the curves according to tailwater conditions: Minimum Tailwater- Use Figure 6-34.1 Maximum Tailwater- Use Figure 6-34.2 Maximum Stone Size = 1.5 x d50 Apron Thickness = 1.5 x dmax Apron Width If the pipe discharges directly into a well-de­ fined channel, the apron shall extend across the channel bottom and up the channel banks to an elevation one foot above the maximum tailwa­ ter depth or to the top of the bank (whichever is less). If the pipe discharges onto a flat area with no defined channel, the width of the apron shall be determined as follows: a. The upstream end of the apron, adjacent to the pipe, shall have a width three times the diameter of the outlet pipe. b. For a Minimum Tailwater Condition, the end of the apron shall have a width equal to the pipe diameter plus the length of the apron. Refer to Figure 6-34.1. c. For a Maximum Tailwater Condition, the down stream end shall have a width equal to the pipe diameter plus 0.4 times the length of the apron. Refer to Figure 6-34.2. Bottom Grade The apron shall be constructed with no slope along its length (0.0% grade). The invert eleva­ tion of the end of the apron shall be equal to the elevation of the invert of the receiv­ ing channel. There shall be no overfall at the end of the apron. Side Slope If the pipe discharges into a well-defined channel, the side slopes of the channel shall not be steeper than 2:1. Storm Drain Outlet Protection St ---PAGE BREAK--- 6-208 2016 Edition Alignment The apron shall be located so that there are no bends in the horizontal alignment. Geotextile Geotextiles should be used as a separator between the graded stone, the soil base, and the abutments. The geotextile will prevent the migra­ tion of soil particles from the subgrade into the graded stone. The geotextile shall be specified in accordance with AASHTO M288-06 Section 8, Geotextile Property Requirements. The geotex­ tile should be placed immediately adjacent to the subgrade without any voids. Materials The apron may be lined with riprap, grouted riprap, or concrete. The median sized stone for riprap, d50, shall be determined from the curves, Figures 6-34.1 and 6-34.2, according to the tail­ water condition. The gradation, quality and place­ ment of riprap shall conform to Appendix C. Refer to Figure 6-34.4, for alternative structures to achieving energy dissipation at an outlet. For information regarding the selection and design of these alternative energy dissipators, refer to: FHWA Standard (REF. Hydraulic Design of En­ ergy Dissipators for Culverts and Channels; HEC No. 14, FHWA, Available from the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402. CONSTRUCTION SPECIFICATIONS 1. Ensure that the subgrade for the filter and riprap follows the required lines and grades shown in the plan. Compact any fill required in the subgrade to the density of the sur­ rounding undisturbed material. Low areas in the subgrade on undisturbed soil may also be filled by increasing the riprap thickness. 2. The riprap and gravel filter must conform to the specified grading limits shown on the plans. 3. Geotextile must meet design requirements and be properly protected from punching or tearing during installation. Repair any dam­ age by removing the riprap and placing an­ other piece of filter fabric over the damaged area. All connecting joints should overlap a minimum of 1 ft. If the damage is extensive, replace the entire filter fabric. 4. Riprap may be placed by equipment, but take care to avoid damaging the filter. 5. The minimum thickness of the riprap should be 1.5 times the maximum stone diameter. 6. Construct the apron on zero grade with no overfall at the end. Make the top of the riprap at the end level with the receiv­ ing area or below it. 7. Ensure that the apron is properly aligned with the receiving stream and preferably straight throughout its length. If a curve is needed to fit site conditions, place it in the upper section of the apron. 8. Immediately after construction, stabilize all disturbed areas with vegetation. 9. Stone quality - Select stone for riprap from field stone or quarry stone. The stone should be hard, angular, and highly weather-resis­ tant. The specific gravity of the individual stones should be at least 2.5. 10. Filter - Install a filter to prevent soil movement through the openings in the riprap. The filter should consist of a graded gravel layer or a filter cloth. See Appendix C; p. C-1. MAINTENANCE Inspect riprap outlet structures after heavy rains to see if any erosion around or below the riprap has taken place or if stones have been dislodged. Immediately make all needed repairs to prevent further damage. ---PAGE BREAK--- 6-209 2016 Edition TO BE SHOWN ON THE EROSION AND SEDIMENT CONTROL PLAN 1. The flow characteristics of the pipe at full flow including pipe diameter, flow rate (cfs), velocity (fps), and tail­ water condition. 2. The dimensions of the apron including length (La), width at the headwall (W1), width (W2), average stone diameter (d50), and stone depth designed in accordance with Figures 6-34.1 and 6-34.2. ---PAGE BREAK--- 6-210 2016 Edition d = 12 d = 15 d = 18 d = 21 d = 24 d = 27 d = 30 d = 12 d = 15 d = 18 d = 24 d = 27 d = 30 v = 30 d = 36 d = 42 d = 48 d = 54 d = 60 d = 66 d = 72 d = 78 d = 84 d = 90 d = 96 v = 20 v = 25 v = 15 v = 5 v = 10 d = 36 d = 42 d = 48 d = 54 d = 60 d = 66 d = 90 d = 96 d = 84 d = 78 d = 72 v = 40 v = 35 3 5 10 20 50 100 [PHONE REDACTED] 0 1 2 3 4 90 80 70 60 50 40 30 Minimum Length of Apron (La)(ft) 20 10 0 Discharge (ft3/sec) Curves may not be extrapolated. d50 Riprap Size (ft) La Tailwater < 0.5Do W = Do La 3Do Outlet pipe diameter (Do) d = 21 + La Figure 6-34.1 - Design of Outlet Protection From a Round Pipe Flowing Full, Minimum Tailwater Condition (Tw < 0.5 Diameter) ---PAGE BREAK--- 6-211 2016 Edition Figure 6-34.2 - Design of Outlet Protection From a Round Pipe Flowing Full, Maximum Tailwater Condition (Tw > 0.5 Diameter) v = 10 v = 15 v = 20 v = 25 v = 30 d = 12 d = 15 d = 18 d = 12 d = 15 d = 18 d = 21 d = 24 d = 27 d = 30 d = 36 d = 42 d = 48 d = 54 d = 60 d = 66 d = 72 d = 78 d = 84 d = 90 d = 96 d = 21 d = 24 d = 27 d = 30 d = 36 d = 42 d = 48 d = 54 d = 60 d = 66 d = 72 d = 78 d = 84 d = 90 d = 96 120 110 100 90 80 70 60 50 40 30 20 10 0 3 5 10 20 50 100 [PHONE REDACTED] 0 Minimum Length of Apron (La)(ft) Discharge (ft3/sec) Curves may not be extrapolated. d50 Riprap Size (ft) La Tailwater 0.5Do W = Do + 0.4La 3Do Outlet pipe diameter(Do) 1 2 3 > ---PAGE BREAK--- 6-212 2016 Edition Figure 6-34.3 - Riprap Outlet Protection (Modified From Va SWCC) ---PAGE BREAK--- 6-213 2016 Edition Figure 6-34.4 ---PAGE BREAK--- 6-214 2016 Edition ---PAGE BREAK--- 6-215 2016 Edition DEFINITION Providing a rough soil surface with horizontal depressions created by operating a tillage or other suitable implement on the contour, or by leaving slopes in a roughened condition by not fine-grading them. PURPOSE The purposes of surface roughening are to aid in establishment of vegetative cover with seed, to reduce runoff velocity and increase infil­ tration, reduce erosion and provide for sediment trapping. CONDITIONS All slopes steeper than 3:1 require surface roughening, either stair-step grading, grooving, furrowing, or tracking if they are to be stabilized with vegetation. However, if the slope is to be stabilized with erosion control blankets or soil reinforcement matting, the soil surface should not be roughened. Areas with grades less steep than 3:1 should have the soil surface roughened and loos­ ened to a depth of 2 to 4 inches prior to seeding. Areas that have been graded and will not be sta­ bilized immediately may be roughened to reduce runoff velocity until seeding takes place. Slopes with a stable rock face do not require roughening or stabilization. DESIGN CRITERIA Graded areas with smooth, hard surfaces give a false impression of “finished grading” and a job well done. It is difficult to establish veg­ etation on such surfaces due to reduced water infiltration and the potential for erosion. Rough slope surfaces with uneven soil and rocks left in place may appear unattractive or unfinished at first, but encourage water infiltration, speed up the establishment of vegetation, and decrease runoff velocity. Rough, loose soil surfaces give lime, fertilizer and seed some natural coverage. Niches in the surface provide microclimates that generally provide a cooler and more favorable moisture level than hard flat surfaces. This aids seed germination. There are different methods of achieving a roughened soil surface on a slope, and the se­ lection of an appropriate method depends upon the type of slope. Roughening methods include stair-step grading, grooving, and tracking. Factors to be considered in choosing a method are slope steepness, mowing requirements, and whether the slope is formed by cutting or filling. 1. Disturbed areas that will not require mowing may be stair-step graded, grooved, or left rough after filling. 2. Stair-step grading is particularly appropriate in soils containing large amounts of soft rock. Each “step” catches material that sloughs from above, and provides a level site where vegetation can become established. 3. Areas that will be mowed (these areas should have slopes less steep than 3:1) may have small furrows left by discing, harrowing, rak­ ing, or seed planting machinery operated on the contour. 4. It is important to avoid excessive compacting of the soil surface when scarifying. Tracking with bulldozer treads is preferable to not roughening at all, but it is not as effective as other forms of roughening, as the soil surface is severly compacted and runoff is increased. CONSTRUCTION SPECIFICATIONS Cut Slopes Steeper than 3:1 Cut slopes with a gradient steeper than 3:1 should not be mowed. They shall be stair-step graded or grooved (see Figure 6-35.1). 1. Stair-step grading may be carried out on any material soft enough to be ripped with a bulldozer. Slopes consisting of soft rock with some subsoil are particularly suited to stair-step grading. Surface Roughening Su ---PAGE BREAK--- 6-216 2016 Edition The ratio of the vertical cut distance to the horizontal distance shall be less than 1:1 and the horizontal portion of the “step” shall slope toward the vertical wall. Individual vertical cuts shall not be more than 30 inches on soft soil material and not more than 40 inches in rocky materials. 2. Grooving consists of using machinery to create a series of ridges and depressions that run perpendicular to the slope (on the contour). Grooves may be made with any appropriate implement that can be safely operated on the slope and that will not cause undue compaction. Suggested implements include discs, tillers, spring harrows, and the teeth on a front-end loader bucket. Such grooves shall not be less than 3 inches deep nor further than 15 inches apart. Fill Slopes Steeper than 3:1 Fill slopes with a gradient steeper than 3:1 should not be mowed. They shall be grooved or allowed to remain rough as they are constructed. Method or below may be used. 1. Groove according to #2 of “Cut Slopes Steeper than 3:1”. 2. As lifts of the fill are constructed, soil and rock material may be allowed to fall naturally onto the slope surface (see Figure 6-35.1). Colluvial materials (soil deposits at the base of slopes or from old stream beds) shall not be used in fills as they flow when saturated. Cuts, Fills, and Graded Areas That Will Be Mowed (less than 3:1) Mowed slopes should not be steeper than 3:1. Excessive roughness is undesirable where mowing is planned. These areas may be roughened with shallow grooves such as remain after tilling, discing, har­ rowing, raking, or use of a multipacker-seeder. The final pass of any such tillage implement shall be on the contour (perpendicular to the slope). Grooves formed by such implements shall be not less than one inch deep and not further than 12 inches apart. Fill slopes that are left rough as constructed may be smoothed with a dragline or pickchain to facilitate mowing. Roughening With Tracked Machinery Roughening with tracked machinery on clayed soils is not recommended unless no alternatives are available. Undue compaction of surface soil results from this practice. Sandy soils do not compact severely and may be tracked. In no case is tracking as effective as the other rough­ ening methods described. When tracking is the chosen surface roughening technique, it shall be done by operating tracked machinery up and down the slope to leave hori­ zontal depressions in the soil. As few passes of the machinery as possible should be made to minimize compaction. Seeding Roughened areas shall be seeded and mulched as soon as possible to obtain optimum seed germination and seeding growth. Refer to specifications Ds1, Ds2, Ds3, and Ds4 - Dis­ turbed Area Stabilization (With Mulching Only, Temporary Seeding, Permanent Vegeta­ tion, and Sodding), respectively. ---PAGE BREAK--- 6-217 2016 Edition Figure 6-35.1 ---PAGE BREAK--- 6-218 2016 Edition Figure 6-35.2 ---PAGE BREAK--- 6-219 2016 Edition DEFINITION A floating or staked barrier installed within the water. (It may also be referred to as a floating boom, silt barrier or silt curtain). PURPOSE Turbidity curtains are installed to minimize turbidity and silt migration from work occurring within the water or as a supplement to perimeter control BMPs at the water’s edge. Silt or turbid­ ity is confined to the area within the boundary created by the installation, such that suspended particles drop out of the water column over time. CONDITIONS By its nature, a turbidity curtain encourages a controlled deposition of silt or sediment. A turbid­ ity curtain is only allowed as a primary device when required permitting has been obtained for the site that approves the filling of State or U.S. waters. The unauthorized storing of sediment in waters of the State is strictly prohibited. The installation of a Tc as a supplemental BMP that in no way represents perimeter control, is allowed provided the stream, river or “water” substrate or bottom will not be altered in any manner by the installation. The owner, operator and design professional are cautioned that State or LIA water buffer and variance requirements may apply to bank and shoreline installations. PLANNING CONSIDERATIONS Careful assessment of the depth, flow or current of water and nature of construction is needed in order to determine if floating or staked installations are warranted. DESIGN CRITERIA Formal design is not required but the follow­ ing guidelines have been established: Depending upon the installation conditions (see Construction Specifications), curtain mate­ rial may be comprised of suitable impermeable materials such as heavy polyethylene film, or suitable permeable materials such as canvas duck. Floating Turbidity Curtains Tc-F Typical installations include large bodies of water such as rivers and lakes. Staked Turbidity Curtains Tc-S Typical installations include shallow inunda­ tions where construction is required. It may be used to protect a small stream while it is being realigned or restored. In this case the barrier should extend to the bottom of the streambed. The height should be limited to 5 feet whenever possible and extend 2 feet above the normal water elevation. CONSTRUCTION SPECIFICATIONS Whenever possible, place barrier approxi­ mately 25 feet outside of the affected construc­ tion area for large water bodies. Installations less than 25 feet from the work are allowed, however narrower confinements promote proportion­ ate sedimentation. Curtain depth should reach a depth within 5 feet of the bottom for floating installations. If the body of water has significant velocity or current, place the barrier parallel to the flow and ensure the curtain is permeable. In smaller streams the barrier should be placed close to the construction area. Installation dimensions and methods shall be fitted to the conditions, permitted activity and construction methods. In no instance shall the silt dispersion exceed the allowances the filling permit has authorized. The permittee is reminded to be a good steward of our resources by minimizing the migration and sedimentation regardless of permits obtained. Turbidity Curtain Tc Tc-F Tc-S ---PAGE BREAK--- 6-220 2016 Edition Barriers shall be either staked or floating depending upon current, tides, water depth and other variables. When staked barriers are used in stream relocations or widening, the curtain shall be permeable, weighted at the bottom and not be trenched in. MAINTENANCE For installations that permit the placement of fill within the water body, maintenance consists of removing the Turbidity Curtain when it is no longer required. If the deposition exceeds the al­ lowances of the filling permit, careful removal of the sediment is required and shall be performed in a manner that is consistent with all other ap­ plicable permits. If the installation is made as a supplemental BMP, the Tc should be removed after final sta­ bilization of the contributing drainage area and perimeter control removal has occurred. ---PAGE BREAK--- 6-221 2016 Edition Figure 6-36.1 ---PAGE BREAK--- 6-222 2016 Edition ---PAGE BREAK--- 6-223 2016 Edition DEFINITION Stripping off the more fertile top soil, storing it, then spreading it over the disturbed area after completion of construction activities. PURPOSE To provide a suitable soil medium for vegeta­ tive growth on areas where other measures will not produce or maintain a desirable stand. CONDITIONS This practice is recommended for sites of 2:1 or flatter slopes where: 1. The texture of the exposed subsoil or parent material is not suitable to produce adequate vegetative growth. 2. The soil material is so shallow that the rooting zone is not deep enough to support plants with continuing supplies of moisture and food. 3. The soil to be vegetated contains material toxic to plant growth. CONSTRUCTION SPECIFICATIONS Materials Topsoil should be friable and loamy, free of debris, objectionable weeds and stones and contain no toxic substance that may be harmful to plant growth. A pH range of 5.0-7.5 is accept­ able. Soluble salts should not exceed 500 ppm. Testing Field exploration should be made to deter­ mine whether the quantity and quality of surface soil justifies stripping. Stripping Stripping should be confined to the immediate construction area. A 4 to 6 inch stripping depth is common, but may vary depending on the particular soil. Topsoil pH If pH value is less than 6.0, lime shall be ap­ plied and incorporated with the topsoil to adjust the pH to 6.5 or higher. Topsoils containing soluble salts greater than 500 parts per million shall not be used. Stockpiles The location of topsoil stockpiles should not obstruct natural drainage or cause off-site envi­ ronmental damage. Stabilization Stockpiles shall be contained by sediment barriers to prevent sedimentation on adjacent ar­ eas. Stockpiles shall be stabilized in accordance with specifications Ds1 and Ds2 - Disturbed Area Stabilization (With Mulching) and (With Temporary Grassing), respectively, or Tac- Tackifiers. Site Preparation (Where topsoil is to be added) Topsoiling - When topsoiling, maintain needed erosion control practices such as diversions, grade stabilization structures, berms, dikes, level spread­ ers, waterways, sediment basins, etc. Grading - Grades on the areas to be topsoiled that have been previously established shall be maintained. Liming - Soil tests should be used to determine the pH of the soil. Where the pH of the subsoil is 5.0 or less or composed of heavy clays, agricultural limestone shall be spread at the rate of 100 pounds per 1,000 square feet. Lime shall be distributed uniformly over designated areas and worked into the soil in conjunction with tillage operations as described in the following procedure. Bonding - Use one of the following methods to insure bonding of topsoil and subsoil: 1. Tilling. After the areas to be topsoiled have Topsoiling Tp ---PAGE BREAK--- 6-224 2016 Edition been brought to grade, and immediately prior to dumping and spreading the topsoil, the subgrade shall be loosened by discing or scarifying to a depth of at least 3 inches to permit bonding of the topsoil to the subsoil. 2. Tracking. Passing a bulldozer over the entire surface area of the slope to leave horizontal depressions. Applying Topsoil 1. Topsoil should be handled only when it is dry enough to work without damaging soil structure. 2. A uniform application of 5 inches (unsettled) is recommended, but may be adjusted at the discretion of the design professional. Table 6-37.1. Cubic Yards Of Topsoil Required For Application To Various Depths Depth Per 1,000 (Inches) Square Feet Per Acre 1 3.1 134 2 6.2 268 3 9.3 403 4 12.4 537 5 15.5 672 6 18.6 806 ---PAGE BREAK--- 6-225 2016 Edition DEFINITION To protect desirable trees from injury during construction activity. PURPOSE To ensure the survival of desirable trees where they will be effective for erosion and sedi­ ment control, watershed protection, landscape beautification, dust and pollution control, noise reduction, shade and other environmental ben­ efits while the land is being converted from forest to urban-type uses. CONSTRUCTION ACTIVITIES Trees can be damaged or killed by a wide variety of construction activities. Obvious injuries such as broken branches or torn bark deplete the tree’s resources and provide entry points for insects, or for diseases such as Oak Wilt. The worst damage, however, often remains hidden underground. Roots are one of the most vital parts of a tree. They are responsible for nutrient and water uptake, energy storage and anchoring the plant. It is critical that you protect roots that lie in the path of construction. Soil compaction is the leading killer of urban trees. Tree roots need loose soil to grow, obtain oxygen, and absorb water and nutrients. Stock­ piled building materials, heavy machinery, and excessive foot traffic, all damage soil structure. Lacking good soil aeration, roots suffocate and tree health declines. Requirement for Regulatory Compliance Many cities and counties in Georgia have tree protection specifications written in their local ordinances. In some areas a permit is needed to remove trees with a specified diameter. It is important for property owners and design profes­ sionals to contact the local government to obtain information regarding tree ordinances BEFORE ES&PC plans are designed. Failure to do so could result in heavy fines or delay in construc­ tion. DESIGN CRITERIA No formal design is required. However, in planning, a number of criteria must be consid­ ered. Tree Protection Zones: 1. Measure the diameter of the tree trunk in inches at 4.5 feet from the ground. This is called the Diameter Breast Height or DBH. 2. Multiply this value by 1.5. This result is the radius of the root protection zone in feet. This is also considered the critical rooting distance. Once the size of the area is determined, con­ sider fencing materials. Orange tree save fencing or black silt fencing are commonly used. These materials are easy to install but they often get knocked down or removed when it is inconvenient to go around the tree save area. In some cases more permanent materials, such as chain link fencing, may be required. Whatever fencing material is used, it must be maintained throughout the construction process. Tree Protection Zone Fencing: Tree protection zone fencing may be one of the following: 1. For areas of large remnant forest to be protected use 4 feet high orange plastic fabric fencing stapled in three locations to treated wood 2x4 stakes. Set stakes 6 feet on center. Rebar is not to be used for stakes. Figure 6-38.1 2. For single family homes use a treated wood fencing as shown on detail. It may have orange fabric attached to it. 3. For all other developments use 6 feet high Tree Protection Tr ---PAGE BREAK--- 6-226 2016 Edition chain link fencing attached to galvanized metal post as shown on detail. Figure 6-38.2 For more information about standards for ad­ equate tree protection, refer to guidance by the American National Standard (ANSI) or the Inter­ national Society of Arboriculture. ---PAGE BREAK--- 6-227 2016 Edition Figure 6-38.1 ---PAGE BREAK--- 6-228 2016 Edition Figure 6-38.2 ---PAGE BREAK--- 6-229 2016 Edition DEFINITION A natural or constructed channel that is shaped or graded to required dimensions and established in suitable vegetation for the stable conveyance of runoff. PURPOSE To dispose of runoff without causing damage either by erosion or by flooding. CONDITIONS This standard applies to all sites where added channel capacity and/or stabilization is required to control erosion resulting from concentrated runoff, and where such control can be achieved by this practice alone or in combination with oth­ ers. DESIGN CRITERIA Capacity The minimum capacity shall be that required to convey the peak runoff expected from a 25- year, 24-hour storm, or the storm specified in Title 12-7-1 of the Official Code of Georgia An­ notated. Peak runoff values used in determining the capacity requirements shall be as outlined in Appendix A or by other accepted methods. The design of a waterway is based on the deter­ mination of channel dimensions that will carry the estimated flow without damage to the channel or its lining. Vegetative linings vary in their protective ability according to type and density. Therefore, safe velocities under various conditions are a mat­ ter for careful consideration. Velocity In designing grassed waterways, care must be taken to ensure that the design velocity is well within the limits of permissible velocities given in Table 6-39.1. These values apply to uniform good stands of each type of cover. Cross Section The minimum design capacity of a waterway receiving water from developing areas, diver­ sions, or other tributary channels shall be that depth required to keep the design water surface elevation in the channel to prevent overflow. The bottom width of waterways or outlets shall not exceed 50 feet unless multiple or divided wa­ terways or other means are provided to control meandering of low flows within this limit. See Figure 6-39.1. Drainage Tile or other suitable subsurface drainage measures shall be provided for sites having high water tables or seepage problems. Where there is base flow, a stone center or lined channel will be required. See Appendix C for rock riprap specifications. Stone Center Stone center waterways shall be constructed as shown in Figure 6-39.2 and Table 6-39.3 and stabilized with riprap according to the specifica­ tion Riprap - Appendix C. Geotextiles should be used as an erosion control measure beneath the riprap center. The geotextile shall be specified in accordance with AASHTO M288-06 Section 8, Geotextile Property Require­ ments. Vegetative Retardance Factor The design of a vegetated waterway is more complicated than for a bare channel since the value for varies where grass linings are used. Tests show that vegetation tends to bend and os­ cillate under the influence of velocity and depth of flow. Thus the retardance to flow varies as these factors change. Five general retardance curves designated as A, B, C, D, and E have been developed for various cover conditions. The vegetated conditions un­ der which the various retardance values apply in Vegetated Waterway or Stormwater Conveyance Channel Wt ---PAGE BREAK--- 6-230 2016 Edition Georgia are shown in Table 6-39.1. These cover classifications are based on tests in experimental channels when the covers were green and gener­ ally uniform. “The Stormwater Conveyance Channel Design Sheets” shall be used to design grass-lined chan­ nels. These design sheets include the cross-sec­ tional detail that shall be included on the erosion and sediment control plan. If a stone center waterway is selected, it shall be designed according to Tables 6-39.2 and 6-39.3. Cross-sectional details on the erosion and sedi­ ment control plan shall include all information noted in Figure 6-39.2, including the maximum stone size of the rock to be used. An example of how to design a grass-lined chan­ nel with a parabolic cross-section is provided on p. 6-288. CONSTRUCTION SPECIFICATIONS 1. All trees, brush, stumps, obstructions, and other objectionable material, shall be re­ moved and disposed of so as not to interfere with the proper functioning of the waterway. 2. The waterway or outlet shall be excavated or shaped to line, grade, and cross section as required to meet the criteria specified herein. It will be free of bank projections or other irregularities that will impede nor­ mal flow. If the channel must have erosion protection other than vegetation, the lining shall not compromise the capacity of the emergency spillway, i.e. the channel shall be over-excavated so that the lining will be flush with the slope surface. 3. Fills shall be compacted as needed to pre­ vent unequal settlement that would cause damage in the completed waterway. 4. All earth removed and not needed in con­ struction shall be spread or disposed of so that it will not interfere with waterway func­ tioning. 5. Stabilization Applicable vegetative standards shall be fol­ lowed for time of seeding, sprigging or sodding, liming and fertilizing, and site and seedbed prepa­ ration. Erosion control blankets or matting or sod shall be used to aid in the establishment of vegetation. Installation methods should follow manufacturer recommendations. Refer to specifications Ds4 - Disturbed Area Stabilization (With Sodding) and Ss - Slope Stabilization. Mulching shall be a requirement for all seeded or sprigged channels. Temporary protection during establishment should be provided when conditions permit through temporary diversions or other means to dispose of water. ---PAGE BREAK--- 6-231 2016 Edition Table 6-39.1. Permissible Velocities and Retardances for Vegetated and Rock-Lined Waterways VEGETATIVE COVER TYPE GOOD STAND MAXIMUM PERMISSIBLE VELOCITY, V1 FEET PER SECOND FOR CAPACITY AND V2 FOR STABILITY AND V1 RETARDANCE PLANT HT. NOT MOWED RETARDANCE PLANT HT. NOT MOWED BERMUDAGRASS B 12” D 2-6” 5 BAHIA C 6-12” D 2-6” 4 TALL FESCUE GRASS MIXTURES1 B 18” D 6” 4 SERICEA LESPEDEZA WEEPING LOVEGRASS B 19” D 2-6” 3 STONE CENTER RIPRAP STONE SIZE CAN BE DETERMINED IN APPENDIX C. 1 Mixtures of Tall Fescue, Bahia, and or Bremuda. NOTE: For planting instructions refer to Disturbed Area Stablization (with Permanent Vegetation) Ds3. ---PAGE BREAK--- 6-232 2016 Edition Figure 6-39.1 ---PAGE BREAK--- 6-233 2016 Edition Figure 6-39.2 - Waterway With Stone Center ---PAGE BREAK--- 6-234 2016 Edition Grade 6 Percent 8 Percent 10 Percent 12 Percent 15 Percent V D Q 8.0 10 1.3 1.6 8.0 10 1.1 1.3 8.0 10 1.0 1.2 8.0 10 0.9 1.1 8.0 10 0.8 0.9 Top Widths 20 25 30 35 40 45 50 55 60 65 70 75 80 90 100 110 120 130 140 150 160 170 180 190 200 220 240 280 280 300 6 7 7 8 9 9 10 7 11 7 12 8 13 9 14 10 16 11 17 11 19 12 20 13 22 14 23 15 25 16 26 17 27 18 29 19 32 21 35 23 38 25 40 27 43 29 5 6 7 8 9 6 9 6 10 7 11 7 12 8 13 9 14 9 15 10 17 11 19 13 21 14 22 15 24 16 26 17 27 18 29 19 31 20 32 22 34 23 38 25 41 27 44 30 48 32 51 34 5 6 7 8 5 9 6 10 7 11 7 12 8 12 9 19 9 14 10 15 10 17 12 19 13 21 14 23 16 25 17 27 18 29 20 31 21 33 22 34 23 36 25 38 26 42 29 46 31 50 34 54 36 57 39 5 6 7 8 5 9 6 10 6 11 7 12 8 13 8 14 9 15 10 16 10 18 11 20 13 22 14 24 15 26 17 29 18 31 19 33 21 35 22 37 24 39 25 42 26 44 28 48 31 53 33 57 36 61 39 66 42 5 6 4 7 5 8 6 10 7 11 7 12 8 13 9 14 9 16 11 17 11 18 12 19 13 21 15 24 16 26 18 29 20 31 21 33 23 36 24 38 26 40 28 43 29 45 31 47 33 52 38 57 39 62 42 67 45 71 49 Table 6-39.2 Velocity, Top Width and Depth for Parabolic Stone Center Waterwaterways ---PAGE BREAK--- 6-235 2016 Edition Table 6-39.3 - Determination of Rock Size For Stone Center Waterway 3.0 Design Depth in Feet d = 1.0 ft D75 7.9 in. S = 5.0% = Max. Size - "D"75 75% of the Rock in Inches Slope of Drain in % 2.5 2.0 1.5 1.0 0.9 EXAMPLE: = 1.0 Feet Place straight edge at value in Design Depth column and at value in Slope column. Read rock size in middle column 7.9 inches. Say 8 inches. FOR DESIGN: 25% of the rock by volumes should be in sizes of 8 inches or larger. The remain- ing 75% or less should be of well graded material, smaller than 8 inches, including sufficient sands and gravels to fill the voids between the larger rock. = 5% 0.8 0.7 0.6 0.5 0.4 0.3 0.3 0.3 0.4 0.4 0.5 0.5 1.0 1.0 1.5 2.0 2.0 3.0 3.0 4.0 4.0 5.0 5.0 10.0 10.0 15.0 15.0 20.0 20.0 50.0 40.0 30.0 100.0 0.2 0.1 0.2 ---PAGE BREAK--- 6-236 2016 Edition 1. Compute peak rate of runoff for 25-year, 24-hour storm. Q25 = 55 cfs 2. Determine grade of channel. Grade = 6% 3. Determine which vegetative cover will be used. Refer to Ds3 - Disturbed Area Stabilization (Using Permanent Vegetation). Vegetative cover = Bermudagrass 4. Determine retardances and permissible velocities for channel using Table 6-27.1. The retardance class for capacity (unmowed vegetation) is B. The retardance class for stability (mowed vegetation) is D. Maximum permissible velocity, V1, is 5 fps. 5. Determine dimensions of the parabolic channel. Use Table 6-28.1, for retardances and For a grade of 6% and a Q25 of 55 cfs, Top width, T = 29.1 ft (includes allowance for vegetative lining) Depth, D = 1.0 ft (includes allowance for vegetative lining) Velocity for unmowed vegetation, V2 = 2.8 fps. STORMWATER CONVEYANCE CHANNEL DESIGN SHEET Vegetated Parabolic Channel EXAMPLE Computed Date Checked Date Project Normal Ground Level Top width = 29 ft Parabolic Channel Example Freeboard = 0.5 ft Grass Depth of flow = 1.0 ft Lining ---PAGE BREAK--- 6-237 2016 Edition 1. Compute peak rate of runoff for 25-year, 24-hour storm. Q25 = cfs 2. Determine grade of channel. Grade = % 3. Determine which vegetative cover will be used. Refer to Ds3 - Disturbed Area Stabilization (Using Permanent Vegetation). Vegetative cover = 4. Determine retardances and permissible velocities for channel using Table 6-27.1. The retardance class for capacity (unmowed vegetation) is The retardance class for stability (mowed vegetation) is Maximum permissible velocity, V1, is fps. 5. Determine dimensions of the parabolic channel. Use Table 6-28.1 for retardances and Use Table 6-28.2 for retardance and For a grade of % and a Q25 of cfs, Top width, T = ft (includes allowance for vegetative lining) Depth, D = ft (includes allowance for vegetative lining) Velocity for unmowed vegetation, V2 = fps. STORMWATER CONVEYANCE CHANNEL DESIGN SHEET Vegetated Parabolic Channel Computed Date Checked Date Project Top width= Normal Ground Level ft ft ft Parabolic Freeboard= Lining Depth of flow = ---PAGE BREAK--- 6-238 2016 Edition 1. Compute peak rate of runoff for 25-year, 24-hour storm. Q25 = cfs 2. Determine grade of channel. Grade = % 3. Determine which vegetative cover will be used. Refer to Ds3 - Disturbed Area Stabilization (Using Permanent Vegetation). Vegetative cover = 4. Determine retardances and permissible velocities for channel using Table 6-27.1. The retardance class for capacity is and the unmowed plant height is in. The retardance class for stability is and the mowed plant height is in. Maximum permissible velocity, V1, is fps. 5. Determine dimensions of the channel. Use Table 6-28.3 for retardance Use Table 6-28.4 for retardance For a grade of % and Q25 of cfs, Side slopes (z:1) = Bottom width, B = ft (0 for triangular channel) Design depth, d = ft Area of channel, A = sf. 6. Calculate the constructed depth of the channel. Constructed depth, D = Design depth, d + Unmowed plant height Constructed depth, D = ft + ft Constructed depth, D = ft 7. Calculate the top width of the channel. Top width, T = Bottom width + 2(Side slope * design depth) Top width, T = B + 2(z*d) Top width, T = ft + Top width, T = ft STORMWATER CONVEYANCE CHANNEL DESIGN SHEET Vegetated Trapezoidal or Triangular Channel Computed Date Checked Date Project Sideslope Sideslope Lining Lining Normal Ground Level Normal Ground Level Triangular Trapezoidal Freeboard= ft Freeboard= ft Depth of flow = ft Depth of flow Top width= ft Top width= ft = ft = :1 Sideslope = :1 Sideslope = :1 = :1 ---PAGE BREAK--- 6-239 2016 Edition TO BE SUBMITTED WITH/ON THE EROSION, SEDIMENTATION AND POLLUTION CONTROL PLAN GRASS-LINED CHANNEL 1. Stormwater Conveyance Channel Design Sheet for the appropriate channel shape. 2. Cross-sectional detail of the channel (include with Design Sheet and show on E&SC Plan). STONE CENTER CHANNEL 1. Cross-sectional detail of the channel on the E&SC Plan. ---PAGE BREAK--- 6-240 2016 Edition ---PAGE BREAK--- 6-241 2016 Edition SECTION IV: TABLES FOR DESIGN OF STORMWATER CONVEYANCE PRACTICES ---PAGE BREAK--- 6-242 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 0.25 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 10 15 20 25 11.0 3.2 1.1 30 13.8 3.0 1.1 35 16.4 2.9 1.1 40 19.0 2.8 1.1 45 21.5 2.8 1.1 11.9 3.7 1.5 50 24.0 2.8 1.1 14.1 3.4 1.5 55 26.5 2.8 1.1 15.8 3.3 1.6 60 29.0 2.8 1.1 17.5 3.3 1.6 65 31.5 2.7 1.1 19.2 3.2 1.6 11.8 4.4 1.9 70 34.0 2.7 1.1 20.8 3.2 1.6 13.7 4.0 1.9 75 37.0 2.7 1.1 22.4 3.2 1.6 15.3 3.8 1.9 80 39.4 2.7 1.1 24.1 3.2 1.6 16.6 3.7 1.9 85 41.9 2.7 1.1 25.7 3.1 1.6 17.9 3.7 1.9 90 44.3 2.7 1.1 27.2 3.1 1.6 19.1 3.6 1.9 95 46.7 2.7 1.1 28.8 3.1 1.6 20.3 3.6 2.0 100 49.2 2.7 1.1 30.4 3.1 1.6 21.5 3.6 2.0 105 51.6 2.7 1.1 32.0 3.1 1.6 22.7 3.5 2.0 110 54.1 2.7 1.1 33.6 3.1 1.6 23.9 3.5 2.0 14.4 4.8 2.4 115 56.5 2.7 1.1 35.1 3.1 1.6 25.1 3.5 2.0 15.7 4.6 2.4 120 59.0 2.7 1.1 36.7 3.1 1.6 26.2 3.5 2.0 17.0 4.4 2.4 125 61.4 2.7 1.1 38.3 3.1 1.6 27.3 3.5 2.0 17.9 4.3 2.4 130 63.9 2.7 1.1 39.7 3.1 1.6 28.5 3.4 2.0 18.8 4.3 2.4 135 66.3 2.7 1.1 41.3 3.1 1.6 29.7 3.4 2.0 19.7 4.2 2.4 140 68.8 2.7 1.1 43.4 3.0 1.6 30.8 3.4 2.0 20.6 4.2 2.4 145 71.2 2.7 1.1 44.9 3.0 1.6 32.0 3.4 2.0 21.5 4.1 2.4 150 73.7 2.7 1.1 46.5 3.0 1.6 33.1 3.4 2.0 22.4 4.1 2.5 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. = Top width, tall vegetation = Depth, tall vegetation = Design velocity, tall vegetation = Permissible velocity, short vegetation T D V2 V1 T D Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-243 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 0.50 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 10 15 10.0 2.2 1.0 20 13.7 2.1 1.0 8.4 2.7 1.3 25 17.4 2.1 1.0 11.3 2.4 1.4 30 21.0 2.0 1.0 13.9 2.3 1.4 35 24.6 2.0 1.1 16.4 2.3 1.4 10.7 2.8 1.8 40 28.5 2.0 1.0 18.9 2.3 1.4 12.6 2.7 1.8 45 31.9 2.0 1.1 21.4 2.3 1.4 14.4 2.6 1.8 50 35.5 2.0 1.1 23.9 2.2 1.4 16.2 2.5 1.8 9.9 3.4 2.2 55 39.0 2.0 1.1 26.3 2.2 1.4 17.9 2.5 1.8 11.9 3.1 2.3 60 42.5 2.0 1.1 28.8 2.2 1.4 19.7 2.5 1.8 13.2 3.0 2.3 65 46.1 2.0 1.1 31.6 2.2 1.4 21.4 2.5 1.8 14.5 2.9 2.3 70 49.6 2.0 1.1 34.0 2.2 1.4 23.1 2.5 1.8 15.8 2.9 2.3 11.0 3.6 2.6 75 53.1 2.0 1.1 36.4 2.2 1.4 24.9 2.5 1.8 17.1 2.8 2.3 12.7 3.4 2.7 80 56.6 2.0 1.1 38.8 2.2 1.4 26.6 2.5 1.8 18.4 2.8 2.3 13.7 3.3 2.7 85 60.2 2.0 1.1 41.2 2.2 1.4 28.3 2.5 1.8 19.7 2.8 2.3 14.8 3.2 2.7 90 63.7 2.0 1.1 43.6 2.2 1.4 30.0 2.4 1.8 20.9 2.8 2.3 15.9 3.2 2.7 95 67.2 2.0 1.1 46.1 2.2 1.4 31.7 2.4 1.8 22.1 2.8 2.3 16.9 3.1 2.7 100 70.8 2.0 1.1 48.5 2.2 1.4 33.7 2.4 1.8 23.4 2.8 2.3 17.9 3.1 2.7 12.3 3.9 3.1 105 74.3 2.0 1.1 50.9 2.2 1.4 35.4 2.4 1.8 24.5 2.7 2.4 18.9 3.1 2.7 13.7 3.7 3.1 110 77.8 2.0 1.1 53.3 2.2 1.4 37.1 2.4 1.8 25.8 2.7 2.4 19.9 3.1 2.7 14.6 3.6 3.1 115 81.4 2.0 1.1 55.7 2.2 1.4 38.7 2.4 1.8 27.0 2.7 2.4 20.8 3.0 2.7 15.4 3.6 3.1 120 84.9 2.0 1.1 58.1 2.2 1.4 40.4 2.4 1.9 28.2 2.7 2.4 21.8 3.0 2.7 16.3 3.5 3.1 125 88.4 2.0 1.1 60.6 2.2 1.4 42.1 2.4 1.9 29.4 2.7 2.4 22.8 3.0 2.7 17.1 3.5 3.1 130 92.0 2.0 1.1 63.0 2.2 1.4 43.8 2.4 1.9 30.6 2.7 2.4 23.8 3.0 2.7 17.9 3.5 3.1 135 95.5 2.0 1.1 65.4 2.2 1.4 45.4 2.4 1.9 31.8 2.7 2.4 24.8 3.0 2.7 18.7 3.4 3.2 140 99.0 2.0 1.1 67.8 2.2 1.4 47.1 2.4 1.9 33.1 2.7 2.4 25.7 3.0 2.8 19.4 3.4 3.2 145 102.6 2.0 1.1 70.2 2.2 1.4 48.8 2.4 1.9 34.3 2.7 2.4 26.7 3.0 2.8 20.2 3.4 3.2 13.5 4.4 3.6 150 106.1 2.0 1.1 72.6 2.2 1.4 50.5 2.4 1.9 35.5 2.7 2.4 27.7 3.0 2.8 21.0 3.4 3.2 14.4 4.3 3.6 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-244 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 0.75 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 10 8.3 1.9 1.0 15 12.9 1.8 1.0 8.4 2.1 1.3 20 17.4 1.7 1.0 11.6 2.0 1.3 7.2 2.6 1.6 25 22.2 1.7 1.0 14.8 1.9 1.3 10.0 2.2 1.7 30 26.6 1.7 1.0 17.9 1.9 1.3 12.3 2.1 1.7 7.7 2.9 2.0 35 31.0 1.7 1.0 20.9 1.9 1.4 14.5 2.1 1.7 10.0 2.5 2.1 40 35.4 1.7 1.0 23.9 1.9 1.4 16.7 2.1 1.7 11.8 2.4 2.1 45 39.8 1.7 1.0 27.3 1.8 1.3 18.9 2.1 1.7 13.5 2.3 2.2 8.9 3.0 2.6 50 44.2 1.7 1.0 30.3 1.8 1.3 21.1 2.0 1.7 15.1 2.3 2.2 10.7 2.7 2.6 55 48.7 1.7 1.0 33.3 1.8 1.3 23.3 2.0 1.7 16.7 2.3 2.2 12.1 2.6 2.6 60 53.1 1.7 1.0 36.3 1.8 1.4 25.5 2.0 1.7 18.4 2.3 2.2 13.4 2.6 2.6 65 57.5 1.7 1.0 39.3 1.8 1.4 28.0 2.0 1.7 20.0 2.2 2.2 14.7 2.5 2.6 9.5 3.3 3.1 70 61.9 1.7 1.0 42.3 1.8 1.4 30.2 2.0 1.7 21.6 2.2 2.2 15.9 2.5 2.6 11.2 3.0 3.1 75 66.3 1.7 1.0 45.3 1.8 1.4 32.3 2.0 1.7 23.2 2.2 2.2 17.2 2.5 2.6 12.3 2.9 3.1 80 70.7 1.7 1.0 48.3 1.8 1.4 34.4 2.0 1.7 24.8 2.2 2.2 18.4 2.5 2.6 13.3 2.9 3.1 85 75.2 1.7 1.0 51.4 1.8 1.4 36.6 2.0 1.7 26.3 2.2 2.2 19.6 2.5 2.6 14.3 2.8 3.1 10.2 3.6 3.4 90 79.6 1.7 1.0 54.4 1.8 1.4 38.7 2.0 1.7 27.9 2.2 2.2 20.8 2.4 2.7 15.3 2.8 3.1 11.4 3.4 3.5 95 84.0 1.7 1.0 57.4 1.8 1.4 40.9 2.0 1.7 29.5 2.2 2.2 22.0 2.4 2.7 16.3 2.8 3.1 12.7 3.2 3.5 100 88.4 1.7 1.0 60.4 1.8 1.4 43.0 2.0 1.7 31.4 2.2 2.2 23.2 2.4 2.7 17.2 2.8 3.1 13.5 3.2 3.5 105 92.8 1.7 1.0 63.4 1.8 1.4 45.1 2.0 1.7 33.0 2.2 2.2 24.4 2.4 2.7 18.2 2.7 3.2 14.4 3.1 3.5 110 97.2 1.7 1.0 66.4 1.8 1.4 47.3 2.0 1.7 34.6 2.2 2.2 25.6 2.4 2.7 19.1 2.7 3.2 15.2 3.1 3.5 115 101.7 1.7 1.0 69.4 1.8 1.4 49.4 2.0 1.7 36.1 2.2 2.2 26.8 2.4 2.7 20.0 2.7 3.2 16.0 3.0 3.5 11.6 3.8 3.9 120 106.1 1.7 1.0 72.5 1.8 1.4 51.6 2.0 1.7 37.7 2.2 2.2 28.0 2.4 2.7 21.0 2.7 3.2 16.8 3.0 3.5 12.6 3.6 3.9 125 110.5 1.7 1.0 75.5 1.8 1.4 53.7 2.0 1.7 39.2 2.2 2.2 29.2 2.4 2.7 21.9 2.7 3.2 17.6 3.0 3.5 13.7 3.5 3.9 130 114.9 1.7 1.0 78.5 1.8 1.4 55.8 2.0 1.7 40.8 2.2 2.2 30.4 2.4 2.7 22.8 2.7 3.2 18.4 3.0 3.6 14.4 3.4 3.9 135 119.3 1.7 1.0 81.5 1.8 1.4 58.0 2.0 1.7 42.4 2.2 2.2 31.6 2.4 2.7 23.8 2.7 3.2 19.1 2.9 3.6 15.1 3.4 4.0 140 123.7 1.7 1.0 84.5 1.8 1.4 60.1 2.0 1.7 43.9 2.2 2.2 32.8 2.4 2.7 24.7 2.7 3.2 19.9 2.9 3.6 15.8 3.4 4.0 145 128.2 1.7 1.0 87.5 1.8 1.4 62.3 2.0 1.7 45.5 2.2 2.2 34.5 2.4 2.7 25.6 2.7 3.2 20.7 2.9 3.6 16.5 3.3 4.0 150 132.6 1.7 1.0 90.6 1.8 1.4 64.4 2.0 1.7 47.1 2.2 2.2 35.7 2.4 2.7 26.5 2.6 3.2 21.5 2.9 3.6 17.1 3.3 4.0 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-245 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 1.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 10 9.7 1.6 1.0 6.2 2.0 1.2 15 14.8 1.5 1.0 10.2 1.7 1.3 6.5 2.2 1.5 20 20.2 1.5 1.0 13.8 1.7 1.3 9.6 1.9 1.6 25 25.1 1.5 1.0 17.4 1.7 1.3 12.2 1.9 1.6 8.5 2.2 2.0 30 30.1 1.5 1.0 21.0 1.6 1.3 14.9 1.8 1.7 10.6 2.1 2.1 35 35.1 1.5 1.0 24.7 1.6 1.3 17.5 1.8 1.7 12.6 2.0 2.1 8.9 2.4 2.5 40 40.1 1.5 1.0 28.2 1.6 1.3 20.0 1.8 1.7 14.5 2.0 2.1 10.5 2.3 2.5 45 45.1 1.5 1.0 31.7 1.6 1.3 22.5 1.8 1.7 16.4 2.0 2.1 12.1 2.2 2.5 8.2 2.8 2.9 50 50.2 1.5 1.0 35.2 1.6 1.3 25.4 1.8 1.7 18.3 2.0 2.1 13.6 2.2 2.5 10.0 2.6 2.9 55 55.2 1.5 1.0 38.8 1.6 1.3 27.9 1.8 1.7 20.3 1.9 2.1 15.1 2.2 2.5 11.2 2.5 3.0 60 60.2 1.5 1.0 42.3 1.6 1.3 30.4 1.8 1.7 22.2 1.9 2.1 16.6 2.1 2.5 12.4 2.4 3.0 65 65.2 1.5 1.0 45.8 1.6 1.3 32.9 1.8 1.7 24.0 1.9 2.1 18.0 2.1 2.5 13.6 2.4 3.0 8.9 3.1 3.5 70 70.2 1.5 1.0 49.3 1.6 1.3 35.5 1.8 1.7 25.9 1.9 2.1 19.5 2.1 2.6 14.8 2.4 3.0 10.6 2.8 3.5 75 75.2 1.5 1.0 52.8 1.6 1.3 38.0 1.8 1.7 28.2 1.9 2.1 20.9 2.1 2.6 16.0 2.3 3.0 11.5 2.8 3.5 80 80.2 1.5 1.0 56.3 1.6 1.3 40.5 1.8 1.7 30.0 1.9 2.1 22.3 2.1 2.6 17.1 2.3 3.0 12.5 2.7 3.5 85 85.2 1.5 1.0 59.8 1.6 1.3 43.0 1.8 1.7 31.9 1.9 2.1 23.7 2.1 2.6 18.3 2.3 3.0 13.5 2.7 3.6 9.8 3.3 3.9 90 90.2 1.5 1.0 63.3 1.6 1.3 45.6 1.8 1.7 33.6 1.9 2.1 25.2 2.1 2.6 19.4 2.3 3.1 14.4 2.6 3.6 10.9 3.1 3.9 95 95.2 1.5 1.0 66.9 1.6 1.3 48.1 1.8 1.7 35.5 1.9 2.1 26.6 2.1 2.6 20.5 2.3 3.1 15.3 2.6 3.6 12.0 3.0 3.9 100 100.2 1.5 1.0 70.4 1.6 1.3 50.6 1.8 1.7 37.4 1.9 2.1 28.0 2.1 2.6 21.6 2.3 3.1 16.2 2.6 3.6 12.9 2.9 4.0 105 105.3 1.5 1.0 73.9 1.6 1.3 53.1 1.8 1.7 39.2 1.9 2.1 29.8 2.1 2.6 22.8 2.3 3.1 17.1 2.6 3.6 13.7 2.9 4.0 10.8 3.4 4.3 110 110.3 1.5 1.0 77.4 1.6 1.3 55.7 1.8 1.7 41.1 1.9 2.1 31.3 2.1 2.6 23.9 2.3 3.1 18.0 2.6 3.6 14.4 2.9 4.0 12.0 3.2 4.3 115 115.3 1.5 1.0 80.9 1.6 1.3 58.2 1.8 1.7 42.9 1.9 2.1 32.7 2.1 2.6 25.0 2.3 3.1 18.9 2.5 3.6 15.2 2.8 4.0 12.7 3.2 4.3 120 120.3 1.5 1.0 84.4 1.6 1.3 60.7 1.8 1.7 44.8 1.9 2.1 34.1 2.1 2.6 26.1 2.2 3.1 19.7 2.5 3.6 16.0 2.8 4.0 13.4 3.1 4.3 125 125.3 1.5 1.0 88.0 1.6 1.3 63.2 1.8 1.7 46.7 1.9 2.1 35.5 2.1 2.6 27.2 2.2 3.1 20.6 2.5 3.6 16.8 2.8 4.0 14.1 3.1 4.3 130 130.3 1.5 1.0 91.5 1.6 1.3 65.8 1.8 1.7 48.5 1.9 2.1 36.9 2.1 2.6 28.4 2.2 3.1 21.5 2.5 3.6 17.4 2.8 4.0 14.8 3.1 4.3 135 135.3 1.5 1.0 95.0 1.6 1.3 68.3 1.8 1.7 50.4 1.9 2.1 38.3 2.1 2.6 29.5 2.2 3.1 22.4 2.5 3.6 18.2 2.8 4.0 15.5 3.0 4.3 140 140.3 1.5 1.0 98.5 1.6 1.3 70.8 1.8 1.7 52.2 1.9 2.1 39.7 2.0 2.6 30.6 2.2 3.1 23.2 2.5 3.6 18.9 2.7 4.0 16.1 3.0 4.4 145 145.3 1.5 1.0 102.0 1.6 1.3 73.3 1.8 1.7 54.1 1.9 2.1 41.1 2.0 2.6 32.1 2.2 3.0 24.1 2.5 3.6 19.7 2.7 4.0 16.8 3.0 4.4 150 150.3 1.5 1.0 105.5 1.6 1.3 75.9 1.8 1.7 56.0 1.9 2.1 42.5 2.0 2.6 33.2 2.2 3.0 25.0 2.5 3.6 20.4 2.7 4.1 17.5 2.9 4.4 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-246 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 1.25 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 5.0 1.8 0.8 10 11.1 1.4 0.9 7.4 1.6 1.2 15 16.9 1.4 1.0 11.6 1.5 1.3 8.1 1.8 1.6 20 22.8 1.4 0.9 15.6 1.5 1.3 11.1 1.7 1.6 7.8 2.0 1.9 25 28.4 1.4 1.0 19.9 1.5 1.3 14.1 1.7 1.6 10.1 1.9 2.0 6.8 2.4 2.3 30 34.1 1.4 1.0 23.8 1.5 1.3 17.0 1.6 1.6 12.4 1.8 2.0 9.0 2.1 2.4 35 39.8 1.4 1.0 27.8 1.5 1.3 19.8 1.6 1.6 14.6 1.8 2.0 10.8 2.0 2.4 7.4 2.5 2.8 40 45.4 1.4 1.0 31.7 1.5 1.3 23.0 1.6 1.6 16.8 1.8 2.0 12.5 2.0 2.5 9.3 2.3 2.9 45 51.1 1.4 1.0 35.6 1.5 1.3 25.8 1.6 1.6 19.0 1.8 2.0 14.2 1.9 2.5 10.7 2.2 2.9 50 56.8 1.4 1.0 39.5 1.5 1.3 28.7 1.6 1.6 21.1 1.7 2.0 15.9 1.9 2.5 12.1 2.1 2.9 8.7 2.6 3.3 55 62.5 1.4 1.0 43.5 1.5 1.3 31.5 1.6 1.6 23.6 1.7 2.0 17.6 1.9 2.5 13.4 2.1 2.9 10.2 2.4 3.4 60 68.1 1.4 1.0 47.4 1.5 1.3 34.4 1.6 1.6 25.7 1.7 2.0 19.2 1.9 2.5 14.7 2.1 2.9 11.3 2.4 3.4 65 73.8 1.4 1.0 51.4 1.5 1.3 37.2 1.6 1.6 27.9 1.7 2.0 20.9 1.9 2.5 16.1 2.1 2.9 12.4 2.3 3.4 9.0 2.9 3.8 70 79.5 1.4 1.0 55.3 1 5 1.3 40.1 1.6 1.6 30.0 1.7 2.0 22.5 1.9 2.5 17.4 2.1 2.9 13.5 2.3 3.4 10.3 2.7 3.8 75 85.2 1.4 1.0 59.2 1.5 1.3 43.0 1.6 1.6 32.1 1.7 2.0 24.1 1.9 2.5 18.6 2.0 3.0 14.6 2.3 3.4 11.3 2.6 3.8 80 90.8 1.4 1.0 63.2 1.5 1.3 45.8 1.6 1.6 34.2 1.7 2.0 26.1 1.9 2.5 19.9 2.0 3.0 15.7 2.2 3.4 12.2 2.5 3.9 85 96.5 1.4 1.0 67.1 1.5 1.3 48.7 1.6 1.6 36.4 1.7 2.0 27.7 1.8 2.5 21.2 2.0 3.0 16.7 2.2 3.4 13.1 2.5 3.9 90 102.2 1.4 1.0 71.1 1.5 1.3 51.5 1.6 1.6 38.5 1.7 2.0 29.3 1.8 2.5 22.5 2.0 3.0 17.7 2.2 3.5 14.0 2.5 3.9 10.1 3.1 4.4 95 107.9 1.4 1.0 75.0 1.5 1.3 54.4 1.6 1.6 40.6 1.7 2.0 30.9 1.8 2.5 23.8 2.0 3.0 18.8 2.2 3.5 14.9 2.5 3.9 11.3 2.9 4.4 100 113.5 1.4 1.0 79.0 1.5 1.3 57.2 1.6 1.6 42.8 1.7 2.0 32.6 1.8 2.5 25.1 2.0 3.0 19.8 2.2 3.5 15.8 2.4 3.9 12.1 2.8 4.4 105 119.2 1.4 1.0 82.9 1.5 1.3 60.1 1.6 1.6 44.9 1.7 2.0 34.2 1.8 2.5 26.4 2.0 3.0 20.8 2.2 3.5 16.6 2.4 3.9 12.8 2.8 4.4 110 124.9 1.4 1.0 86.9 1.5 1.3 63.0 1.6 1.6 47.0 1.7 2.0 35.8 1.8 2.5 27.6 2.0 3.0 21.9 2.2 3.5 17.5 2.4 3.9 13.6 2.8 4.4 115 130.6 1.4 1.0 90.8 1.5 1.3 65.8 1.6 1.6 49.2 1.7 2.0 37.4 1.8 2.5 29.3 2.0 3.0 22.9 2.2 3.5 18.3 2.4 3.9 14.3 2.7 4.4 120 136.2 1.4 1.0 94.8 1.5 1.3 68.7 1.6 1.6 51.3 1.7 2.0 39.0 1.8 2.5 30.5 2.0 3.0 23.9 2.2 3.5 19.2 2.4 3.9 15.0 2.7 4.4 125 141.9 1.4 1.0 98.7 1.5 1.3 71.5 1.6 1.6 53.4 1.7 2.0 40.6 1.8 2.5 31.8 2.0 3.0 25.0 2.2 3.5 20.0 2.4 3.9 15.8 2.7 4.4 130 147.6 1.4 1.0 102.7 1.5 1.3 74.4 1.6 1.6 55.6 1.7 2.0 42.3 1.8 2.5 33.1 2.0 3.0 26.0 2.2 3.5 20.9 2.4 3.9 16.4 2.7 4.5 135 153.3 1.4 1.0 106.6 1.5 1.3 77.3 1.6 1.6 57.7 1.7 2.0 43.9 1.8 2.5 34.3 2.0 3.0 27.0 2.2 3.5 21.7 2.4 3.9 17.1 2.6 4.5 140 158.9 1.4 1.0 110.5 1.5 1.3 80.1 1.6 1.6 59.8 1.7 2.0 45.5 1.8 2.5 35.6 2.0 3.0 28.0 2.2 3.5 22.6 2.4 3.9 17.8 2.6 4.5 145 164.6 1.4 1.0 114.5 1.5 1.3 83.0 1.6 1.6 62.0 1.7 2.0 47.1 1.8 2.5 36.9 2.0 3.0 29.1 2.2 3.5 23.4 2.4 3.9 18.5 2.6 4.5 150 170.3 1.4 1.0 118.4 1.5 1.3 85.8 1.6 1.6 64.1 1.7 2.0 48.8 1.8 2.5 38.1 2.0 3.0 30.1 2.2 3.5 24.3 2.3 4.0 19.2 2.6 4.5 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-247 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 1.50 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 5.9 1.5 0.9 10 12.4 1.3 0.9 8.3 1.5 1.2 5.5 1.9 1.5 15 18.9 1.3 0.9 12.8 1.4 1.2 9.1 1.6 1.6 6.2 1.9 1.9 20 25.1 1.3 0.9 17.2 1.4 1.2 12.4 1.5 1.6 9.0 1.7 1.9 6.0 2.2 2.2 25 31.4 1.3 0.9 21.8 1.4 1.2 15.6 1.5 1.6 11.5 1.7 2.0 8.4 1.9 2.4 30 37.7 1.3 0.9 26.1 1.4 1.2 18.8 1.5 1.6 14.0 1.6 2.0 10.4 1.8 2.4 7.6 2.1 2.8 35 43.9 1.3 0.9 30.4 1.4 1.2 22.2 1.5 1.6 16.4 1.6 2.0 12.3 1.8 2.4 9.2 2.0 2.8 40 50.2 1.3 0.9 34.8 1.4 1.3 25.3 1.5 1.6 18.8 1.6 2.0 14.2 1.8 2.4 10.8 2.0 2.8 7.8 2.4 3.2 45 56.5 1.3 0.9 39.1 1.4 1.3 28.5 1.5 1.6 21.2 1.6 2.0 16.1 1.7 2.4 12.3 1.9 2.9 9.4 2.2 3.3 50 62.7 1.3 0.9 43.5 1.4 1.3 31.7 1.5 1.6 23.9 1.6 2.0 17.9 1.7 2.4 13.8 1.9 2.9 10.6 2.1 3.3 55 69.0 1.3 0.9 47.8 1.4 1.3 34.8 1.5 1.6 26.2 1.6 2.0 19.8 1.7 2.4 15.3 1.9 2.9 11.9 2.1 3.3 9.1 2.4 3.7 60 75.3 1.3 0.9 52.1 1.4 1.3 38.0 1.5 1.6 28.6 1.6 2.0 21.6 1.7 2.4 16.7 1.9 2.9 13.1 2.1 3.3 10.1 2.4 3.8 65 81.5 1.3 0.9 56.5 1.4 1.3 41.1 1.5 1.6 31.0 1.6 2.0 23.8 1.7 2.4 18.2 1.9 2.9 14.3 2.0 3.3 11.2 2.3 3.8 70 87.8 1.3 0.9 60.8 1.4 1.3 44.3 1.5 1.6 33.3 1.6 2.0 25.6 1.7 2.4 19.6 1.8 2.9 15.5 2.0 3.3 12.2 2.3 3.8 9.2 2.7 4.2 75 94.1 1.3 0.9 65.2 1.4 1.3 47.4 1.5 1.6 35.7 1.6 2.0 27.4 1.7 2.4 21.0 1.8 2.9 16.6 2.0 3.4 13.2 2.2 3.8 10.3 2.6 4.2 80 100.3 1.3 0.9 69.5 1.4 1.3 50.6 1.5 1.6 38.1 1.6 2.0 29.1 1.7 2.4 22.5 1.8 2.9 17.8 2.0 3.4 14.2 2.2 3.8 11.2 2.5 4.3 85 106.6 1.3 0.9 73.8 1.4 1.3 53.7 1.5 1.6 40.5 1.6 2.0 30.9 1.7 2.4 23.9 1.8 2.9 18.9 2.0 3.4 15.2 2.2 3.8 12.1 2.5 4.3 90 112.9 1.3 0.9 78.2 1.4 1.3 56.9 1.5 1.6 42.8 1.6 2.0 32.7 1.7 2.4 25.7 1.8 2.9 20.1 2.0 3.4 16.1 2.2 3.9 12.9 2.4 4.3 95 119.1 1.3 0.9 82.5 1.4 1.3 60.0 1.5 1.6 45.2 1.6 2.0 34.5 1.7 2.4 27.1 1.8 2.9 21.2 2.0 3.4 17.0 2.2 3.9 13.8 2.4 4.3 100 125.4 1.3 0.9 86.9 1.4 1.3 63.2 1.5 1.6 47.6 1.6 2.0 36.3 1.7 2.4 28.5 1.8 2.9 22.4 2.0 3.4 18.0 2.2 3.9 14.6 2.4 4.3 105 131.7 1.3 0.9 91.2 1.4 1.3 66.4 1.5 1.6 50.0 1.6 2.0 38.1 1.7 2.4 29.9 1.8 2.9 23.5 2.0 3.4 19.0 2.1 3.9 15.4 2.4 4.3 110 138.0 1.3 0.9 95.5 1.4 1.3 69.5 1.5 1.6 52.3 1.6 2.0 40.0 1.7 2.4 31.3 1.8 2.9 24.7 2.0 3.4 19.9 2.1 3.9 16.2 2.3 4.3 115 144.2 1.3 0.9 99.9 1.4 1.3 72.7 1.5 1.6 54.7 1.6 2.0 41.8 1.7 2.4 32.8 1.8 2.9 25.8 2.0 3.4 20.9 2.1 3.9 17.0 2.3 4.3 120 150.5 1.3 0.9 104.2 1.4 1.3 75.8 1.5 1.6 57.1 1.6 2.0 43.6 1.7 2.4 34.2 1.8 2.9 27.0 2.0 3.4 21.8 2.1 3.9 17.8 2.3 4.4 125 156.8 1.3 0.9 108.6 1.4 1.3 79.0 1.5 1.6 59.5 1.6 2.0 45.4 1.7 2.4 35.6 1.8 2.9 28.5 2.0 3.4 22.7 2.1 3.9 18.6 2.3 4.4 130 163.0 1.3 0.9 112.9 1.4 1.3 82.2 1.5 1.6 61.8 1.6 2.0 47.2 1.7 2.4 37.0 1.8 2.9 29.6 2.0 3.4 23.7 2.1 3.9 19.3 2.3 4.4 135 169.3 1.3 0.9 117.2 1.4 1.3 85.3 1.5 1.6 64.2 1.6 2.0 49.0 1.7 2.4 38.4 1.8 2.9 30.8 1.9 3.4 24.6 2.1 3.9 20.1 2.3 4.4 140 175.6 1.3 0.9 121.6 1.4 1.3 88.5 1.5 1.6 66.6 1.6 2.0 50.8 1.7 2.4 39.8 1.8 2.9 31.9 1.9 3.4 25.6 2.1 3.9 20.9 2.3 4.4 145 181.8 1.3 0.9 125.9 1.4 1.3 91.6 1.5 1.6 69.0 1.6 2.0 52.6 1.7 2.4 41.3 1.8 2.9 33.0 1.9 3.4 26.5 2.1 3.9 21.7 2.3 4.4 150 188.1 1.3 0.9 130.3 1.4 1.3 94.8 1.5 1.6 71.3 1.6 2.0 54.4 1.7 2.4 42.7 1.8 2.9 34.2 1.9 3.4 27.4 2.1 3.9 22.5 2.3 4.4 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-248 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 1.50 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 5.9 1.5 0.9 10 12.4 1.3 0.9 8.3 1.5 1.2 5.5 1.9 1.5 15 18.9 1.3 0.9 12.8 1.4 1.2 9.1 1.6 1.6 6.2 1.9 1.9 20 25.1 1.3 0.9 17.2 1.4 1.2 12.4 1.5 1.6 9.0 1.7 1.9 6.0 2.2 2.2 25 31.4 1.3 0.9 21.8 1.4 1.2 15.6 1.5 1.6 11.5 1.7 2.0 8.4 1.9 2.4 30 37.7 1.3 0.9 26.1 1.4 1.2 18.8 1.5 1.6 14.0 1.6 2.0 10.4 1.8 2.4 7.6 2.1 2.8 35 43.9 1.3 0.9 30.4 1.4 1.2 22.2 1.5 1.6 16.4 1.6 2.0 12.3 1.8 2.4 9.2 2.0 2.8 40 50.2 1.3 0.9 34.8 1.4 1.3 25.3 1.5 1.6 18.8 1.6 2.0 14.2 1.8 2.4 10.8 2.0 2.8 7.8 2.4 3.2 45 56.5 1.3 0.9 39.1 1.4 1.3 28.5 1.5 1.6 21.2 1.6 2.0 16.1 1.7 2.4 12.3 1.9 2.9 9.4 2.2 3.3 50 62.7 1.3 0.9 43.5 1.4 1.3 31.7 1.5 1.6 23.9 1.6 2.0 17.9 1.7 2.4 13.8 1.9 2.9 10.6 2.1 3.3 55 69.0 1.3 0.9 47.8 1.4 1.3 34.8 1.5 1.6 26.2 1.6 2.0 19.8 1.7 2.4 15.3 1.9 2.9 11.9 2.1 3.3 9.1 2.4 3.7 60 75.3 1.3 0.9 52.1 1.4 1.3 38.0 1.5 1.6 28.6 1.6 2.0 21.6 1.7 2.4 16.7 1.9 2.9 13.1 2.1 3.3 10.1 2.4 3.8 65 81.5 1.3 0.9 56.5 1.4 1.3 41.1 1.5 1.6 31.0 1.6 2.0 23.8 1.7 2.4 18.2 1.9 2.9 14.3 2.0 3.3 11.2 2.3 3.8 70 87.8 1.3 0.9 60.8 1.4 1.3 44.3 1.5 1.6 33.3 1.6 2.0 25.6 1.7 2.4 19.6 1.8 2.9 15.5 2.0 3.3 12.2 2.3 3.8 9.2 2.7 4.2 75 94.1 1.3 0.9 65.2 1.4 1.3 47.4 1.5 1.6 35.7 1.6 2.0 27.4 1.7 2.4 21.0 1.8 2.9 16.6 2.0 3.4 13.2 2.2 3.8 10.3 2.6 4.2 80 100.3 1.3 0.9 69.5 1.4 1.3 50.6 1.5 1.6 38.1 1.6 2.0 29.1 1.7 2.4 22.5 1.8 2.9 17.8 2.0 3.4 14.2 2.2 3.8 11.2 2.5 4.3 85 106.6 1.3 0.9 73.8 1.4 1.3 53.7 1.5 1.6 40.5 1.6 2.0 30.9 1.7 2.4 23.9 1.8 2.9 18.9 2.0 3.4 15.2 2.2 3.8 12.1 2.5 4.3 90 112.9 1.3 0.9 78.2 1.4 1.3 56.9 1.5 1.6 42.8 1.6 2.0 32.7 1.7 2.4 25.7 1.8 2.9 20.1 2.0 3.4 16.1 2.2 3.9 12.9 2.4 4.3 95 119.1 1.3 0.9 82.5 1.4 1.3 60.0 1.5 1.6 45.2 1.6 2.0 34.5 1.7 2.4 27.1 1.8 2.9 21.2 2.0 3.4 17.0 2.2 3.9 13.8 2.4 4.3 100 125.4 1.3 0.9 86.9 1.4 1.3 63.2 1.5 1.6 47.6 1.6 2.0 36.3 1.7 2.4 28.5 1.8 2.9 22.4 2.0 3.4 18.0 2.2 3.9 14.6 2.4 4.3 105 131.7 1.3 0.9 91.2 1.4 1.3 66.4 1.5 1.6 50.0 1.6 2.0 38.1 1.7 2.4 29.9 1.8 2.9 23.5 2.0 3.4 19.0 2.1 3.9 15.4 2.4 4.3 110 138.0 1.3 0.9 95.5 1.4 1.3 69.5 1.5 1.6 52.3 1.6 2.0 40.0 1.7 2.4 31.3 1.8 2.9 24.7 2.0 3.4 19.9 2.1 3.9 16.2 2.3 4.3 115 144.2 1.3 0.9 99.9 1.4 1.3 72.7 1.5 1.6 54.7 1.6 2.0 41.8 1.7 2.4 32.8 1.8 2.9 25.8 2.0 3.4 20.9 2.1 3.9 17.0 2.3 4.3 120 150.5 1.3 0.9 104.2 1.4 1.3 75.8 1.5 1.6 57.1 1.6 2.0 43.6 1.7 2.4 34.2 1.8 2.9 27.0 2.0 3.4 21.8 2.1 3.9 17.8 2.3 4.4 125 156.8 1.3 0.9 108.6 1.4 1.3 79.0 1.5 1.6 59.5 1.6 2.0 45.4 1.7 2.4 35.6 1.8 2.9 28.5 2.0 3.4 22.7 2.1 3.9 18.6 2.3 4.4 130 163.0 1.3 0.9 112.9 1.4 1.3 82.2 1.5 1.6 61.8 1.6 2.0 47.2 1.7 2.4 37.0 1.8 2.9 29.6 2.0 3.4 23.7 2.1 3.9 19.3 2.3 4.4 135 169.3 1.3 0.9 117.2 1.4 1.3 85.3 1.5 1.6 64.2 1.6 2.0 49.0 1.7 2.4 38.4 1.8 2.9 30.8 1.9 3.4 24.6 2.1 3.9 20.1 2.3 4.4 140 175.6 1.3 0.9 121.6 1.4 1.3 88.5 1.5 1.6 66.6 1.6 2.0 50.8 1.7 2.4 39.8 1.8 2.9 31.9 1.9 3.4 25.6 2.1 3.9 20.9 2.3 4.4 145 181.8 1.3 0.9 125.9 1.4 1.3 91.6 1.5 1.6 69.0 1.6 2.0 52.6 1.7 2.4 41.3 1.8 2.9 33.0 1.9 3.4 26.5 2.1 3.9 21.7 2.3 4.4 150 188.1 1.3 0.9 130.3 1.4 1.3 94.8 1.5 1.6 71.3 1.6 2.0 54.4 1.7 2.4 42.7 1.8 2.9 34.2 1.9 3.4 27.4 2.1 3.9 22.5 2.3 4.4 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-249 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 1.75 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 6.5 1.3 0.9 10 13.5 1.2 0.9 9.1 1.4 1.2 6.4 1.6 1.5 15 20.5 1.2 0.9 13.9 1.3 1.2 10.0 1.4 1.6 7.2 1.7 1.9 20 27.3 1.2 0.9 18.8 1.3 1.2 13.6 1.4 1.6 10.0 1.6 1.9 7.3 1.8 2.3 25 34.1 1.2 0.9 23.5 1.3 1.2 17.0 1.4 1.6 12.7 1.5 1.9 9.5 1.7 2.3 6.8 2.0 2.7 30 40.9 1.2 0.9 28.2 1.3 1.2 20.7 1.4 1.6 15.4 1.5 1.9 11.6 1.7 2.3 8.7 1.9 2.8 35 47.7 1.2 0.9 32.8 1.3 1.2 24.1 1.4 1.6 17.9 1.5 2.0 13.6 1.6 2.4 10.4 1.8 2.8 7.9 2.1 3.2 40 54.5 1.2 0.9 37.5 1.3 1.2 27.5 1.4 1.6 20.8 1.5 1.9 15.7 1.6 2.4 12.1 1.8 2.8 9.3 2.0 3.2 45 61.3 1.2 0.9 42.2 1.3 1.2 30.9 1.4 1.6 23.4 1.5 1.9 17.7 1.6 2.4 13.7 1.8 2.8 10.7 1.9 3.3 7.9 2.3 3.7 50 68.1 1.2 0.9 46.9 1.3 1.2 34.4 1.4 1.6 26.0 1.5 1.9 19.7 1.6 2.4 15.3 1.7 2.8 12.0 1.9 3.3 9.3 2.2 3.7 55 74.9 1.2 0.9 51.6 1.3 1.2 37.8 1.4 1.6 28.5 1.5 1.9 22.1 1.6 2.3 16.9 1.7 2.8 13.3 1.9 3.3 10.5 2.1 3.7 7.5 2.7 4.1 60 81.7 1.2 0.9 56.2 1.3 1.2 41.2 1.4 1.6 31.1 1.5 2.0 24.0 1.6 2.3 18.5 1.7 2.8 14.6 1.9 3.3 11.6 2.1 3.7 9.0 2.4 4.1 65 88.5 1.2 0.9 60.9 1.3 1.2 44.6 1.4 1.6 33.7 1.5 2.0 26.0 1.6 2.4 20.1 1.7 2.8 15.9 1.9 3.3 12.7 2.1 3.7 10.0 2.3 4.2 70 95.4 1.2 0.9 65.6 1.3 1.2 48.1 1.4 1.6 36.3 1.5 2.0 28.0 1.6 2.4 21.6 1.7 2.9 17.2 1.8 3.3 13.8 2.0 3.8 11.0 2.3 4.2 75 102.2 1.2 0.9 70.3 1.3 1.2 51.5 1.4 1.6 38.9 1.5 2.0 30.0 1.6 2.4 23.2 1.7 2.9 18.4 1.8 3.3 14.8 2.0 3.8 11.9 2.2 4.2 80 109.0 1.2 0.9 75.0 1.3 1.2 54.9 1.4 1.6 41.5 1.5 2.0 32.0 1.6 2.4 25.1 1.7 2.8 19.7 1.8 3.3 15.8 2.0 3.8 12.8 2.2 4.2 85 115.8 1.2 0.9 79.6 1.3 1.2 58.3 1.4 1.6 44.1 1.5 2.0 34.0 1.6 2.4 26.6 1.7 2.8 21.0 1.8 3.3 16.9 2.0 3.8 13.7 2.2 4.2 90 122.6 1.2 0.9 84.3 1.3 1.2 61.8 1.4 1.6 46.6 1.5 2.0 36.0 1.6 2.4 28.2 1.7 2.8 22.2 1.8 3.3 17.9 2.0 3.8 14.6 2.2 4.3 95 129.4 1.2 0.9 89.0 1.3 1.2 65.2 1.4 1.6 49.2 1.5 2.0 37.9 1.6 2.4 29.8 1.7 2.8 23.5 1.8 3.3 19.0 2.0 3.8 15.5 2.2 4.3 100 136.2 1.2 0.9 93.7 1.3 1.2 68.6 1.4 1.6 51.8 1.5 2.0 39.8 1.6 2.4 31.3 1.7 2.8 24.8 1.8 3.3 20.0 2.0 3.8 16.3 2.1 4.3 105 143.0 1.2 0.9 98.4 1.3 1.2 72.1 1.4 1.6 54.4 1.5 2.0 41.8 1.6 2.4 32.9 1.7 2.8 26.4 1.8 3.3 21.1 2.0 3.8 17.2 2.1 4.3 110 149.8 1.2 0.9 103.1 1.3 1.2 75.5 1.4 1.6 57.0 1.5 2.0 43.8 1.6 2.4 34.4 1.7 2.8 27.6 1.8 3.3 22.1 2.0 3.8 18.1 2.1 4.3 115 156.6 1.2 0.9 107.7 1.3 1.2 78.9 1.4 1.6 59.6 1.5 2.0 45.8 1.6 2.4 36.0 1.7 2.8 28.9 1.8 3.3 23.1 2.0 3.8 19.0 2.1 4.3 120 163.4 1.2 0.9 112.4 1.3 1.2 82.3 1.4 1.6 62.2 1.5 2.0 47.8 1.6 2.4 37.6 1.7 2.8 30.1 1.8 3.3 24.2 1.9 3.8 19.8 2.1 4.3 125 170.3 1.2 0.9 117.1 1.3 1.2 85.8 1.4 1.6 64.8 1.5 2.0 49.8 1.6 2.4 39.1 1.7 2.9 31.4 1.8 3.3 25.2 1.9 3.8 20.7 2.1 4.3 130 177.1 1.2 0.9 121.8 1.3 1.2 89.2 1.4 1.6 67.3 1.5 2.0 51.8 1.6 2.4 40.7 1.7 2.9 32.6 1.8 3.3 26.2 1.9 3.8 21.5 2.1 4.3 135 183.9 1.2 0.9 126.5 1.3 1.2 92.6 1.4 1.6 69.9 1.5 2.0 53.8 1.6 2.4 42.2 1.7 2.9 33.9 1.8 3.3 27.3 1.9 3.8 22.4 2.1 4.3 140 190.7 1.2 0.9 131.2 1.3 1.2 96.1 1.4 1.6 72.5 1.5 2.0 55.7 1.6 2.4 43.8 1.7 2.9 35.1 1.8 3.3 28.7 1.9 3.8 23.3 2.1 4.3 145 197.5 1.2 0.9 135.8 1.3 1.2 99.5 1.4 1.6 75.1 1.5 2.0 57.7 1.6 2.4 45.3 1.7 2.9 36.4 1.8 3.3 29.7 1.9 3.8 24.1 2.1 4.3 150 204.3 1.2 0.9 140.5 1.3 1.2 102.9 1.4 1.6 77.7 1.5 2.0 59.7 1.6 2.4 46.9 1.7 2.9 37.6 1.8 3.3 30.7 1.9 3.8 25.0 2.1 4.3 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-250 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 2.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 7.1 1.2 0.9 10 14.7 1.2 0.9 9.5 1.3 1.2 7.0 1.4 1.5 15 22.0 1.2 0.9 14.5 1.3 1.2 10.8 1.4 1.5 8.0 1.5 1.9 5.5 1.9 2.1 20 29.3 1.2 0.9 19.6 1.2 1.2 14.6 1.3 1.5 10.9 1.5 1.9 8.1 1.6 2.3 5.5 2.1 2.6 25 36.6 1.2 0.9 24.4 1.2 1.2 18.5 1.3 1.5 13.8 1.4 1.9 10.4 1.6 2.3 7.9 1.8 2.7 30 43.9 1.2 0.9 29.3 1.2 1.2 22.2 1.3 1.6 16.6 1.4 1.9 12.7 1.5 2.3 9.7 1.7 2.7 7.3 2.0 3.1 35 51.2 1.2 0.9 34.2 1.2 1.2 25.8 1.3 1.6 19.6 1.4 1.9 14.9 1.5 2.3 11.5 1.7 2.7 8.9 1.9 3.2 40 58.5 1.2 0.9 39.0 1.2 1.2 29.5 1.3 1.6 22.4 1.4 1.9 17.1 1.5 2.3 13.3 1.6 2.8 10.4 1.8 3.2 8.0 2.1 3.6 45 65.8 1.2 0.9 43.9 1.2 1.2 33.2 1.3 1.6 25.2 1.4 1.9 19.3 1.5 2.3 15.0 1.6 2.8 11.8 1.8 3.2 9.2 2.0 3.7 50 73.1 1.2 0.9 48.8 1.2 1.2 36.8 1.3 1.6 28.0 1.4 1.9 21.7 1.5 2.3 16.7 1.6 2.8 13.2 1.8 3.2 10.5 1.9 3.7 7.9 2.3 4.1 55 80.4 1.2 0.9 53.6 1.2 1.2 40.5 1.3 1.6 30.7 1.4 1.9 23.9 1.5 2.3 18.5 1.6 2.8 14.6 1.7 3.2 11.7 1.9 3.7 9.2 2.2 4.1 60 87.7 1.2 0.9 58.5 1.2 1.2 44.2 1.3 1.6 33.5 1.4 1.9 26.0 1.5 2.3 20.2 1.6 2.8 16.0 1.7 3.2 12.8 1.9 3.7 10.2 2.1 4.1 65 95.0 1.2 0.9 63.4 1.2 1.2 47.9 1.3 1.6 36.3 1.4 1.9 28.2 1.5 2.3 22.1 1.6 2.8 17.4 1.7 3.3 14.0 1.9 3.7 11.3 2.1 4.2 70 102.3 1.2 0.9 68.2 1.2 1.2 51.6 1.3 1.6 39.1 1.4 1.9 30.3 1.5 2.3 23.8 1.6 2.8 18.8 1.7 3.3 15.2 1.9 3.7 12.3 2.1 4.2 75 109.6 1.2 0.9 73.1 1.2 1.2 55.2 1.3 1.6 41.9 1.4 1.9 32.5 1.5 2.3 25.5 1.6 2.8 20.1 1.7 3.3 16.2 1.8 3.7 13.2 2.0 4.2 80 116.9 1.2 0.9 78.0 1.2 1.2 58.9 1.3 1.6 44.7 1.4 1.9 34.6 1.5 2.3 27.2 1.6 2.8 21.5 1.7 3.3 17.4 1.8 3.8 14.2 2.0 4.2 85 124.2 1.2 0.9 82.9 1.2 1.2 62.6 1.3 1.6 47.4 1.4 1.9 36.8 1.5 2.3 28.9 1.6 2.8 22.9 1.7 3.3 18.5 1.8 3.8 15.1 2.0 4.2 90 131.5 1.2 0.9 87.7 1.2 1.2 66.3 1.3 1.6 50.2 1.4 1.9 39.0 1.5 2.3 30.6 1.6 2.8 24.6 1.7 3.2 19.6 1.8 3.8 16.1 2.0 4.2 95 138.8 1.2 0.9 92.6 1.2 1.2 69.9 1.3 1.6 53.0 1.4 1.9 41.1 1.5 2.3 32.3 1.6 2.8 25.9 1.7 3.3 20.8 1.8 3.8 17.0 2.0 4.2 100 146.1 1.2 0.9 97.5 1.2 1.2 73.6 1.3 1.6 55.8 1.4 1.9 43.3 1.5 2.3 34.0 1.6 2.8 27.3 1.7 3.3 21.9 1.8 3.8 18.0 2.0 4.2 105 153.4 1.2 0.9 102.3 1.2 1.2 77.3 1.3 1.6 58.6 1.4 1.9 45.4 1.5 2.3 35.7 1.6 2.8 28.6 1.7 3.3 23.0 1.8 3.8 18.9 2.0 4.2 110 160.7 1.2 0.9 107.2 1.2 1.2 81.0 1.3 1.6 61.4 1.4 1.9 47.6 1.5 2.3 37.3 1.6 2.8 30.0 1.7 3.3 24.1 1.8 3.8 19.8 2.0 4.2 115 168.0 1.2 0.9 112.1 1.2 1.2 84.7 1.3 1.6 64.2 1.4 1.9 49.8 1.5 2.3 39.0 1.6 2.8 31.3 1.7 3.3 25.3 1.8 3.8 20.8 2.0 4.2 120 175.3 1.2 0.9 117.0 1.2 1.2 88.3 1.3 1.6 67.0 1.4 1.9 51.9 1.5 2.3 40.7 1.6 2.8 32.7 1.7 3.3 26.7 1.8 3.7 21.7 2.0 4.2 125 182.6 1.2 0.9 121.8 1.2 1.2 92.0 1.3 1.6 69.7 1.4 1.9 54.1 1.5 2.3 42.4 1.6 2.8 34.1 1.7 3.3 27.8 1.8 3.7 22.6 1.9 4.3 130 189.9 1.2 0.9 126.7 1.2 1.2 95.7 1.3 1.6 72.5 1.4 1.9 56.2 1.5 2.3 44.1 1.6 2.8 35.4 1.7 3.3 28.9 1.8 3.7 23.6 1.9 4.3 135 197.3 1.2 0.9 131.6 1.2 1.2 99.4 1.3 1.6 75.3 1.4 1.9 58.4 1.5 2.3 45.8 1.6 2.8 36.8 1.7 3.3 30.0 1.8 3.7 24.5 1.9 4.3 140 204.6 1.2 0.9 136.5 1.2 1.2 103.1 1.3 1.6 78.1 1.4 1.9 60.6 1.5 2.3 47.5 1.6 2.8 38.1 1.7 3.3 31.1 1.8 3.7 25.4 1.9 4.3 145 211.9 1.2 0.9 141.3 1.2 1.2 106.7 1.3 1.6 80.9 1.4 1.9 62.7 1.5 2.3 49.2 1.6 2.8 39.5 1.7 3.3 32.3 1.8 3.7 26.4 1.9 4.3 150 219.2 1.2 0.9 146.2 1.2 1.2 110.4 1.3 1.6 83.7 1.4 1.9 64.9 1.5 2.3 50.9 1.6 2.8 40.8 1.7 3.3 33.4 1.8 3.7 27.3 1.9 4.3 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-251 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 3.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 8.8 1.0 0.8 5.8 1.1 1.1 3.9 1.5 1.3 10 18.0 1.0 0.8 12.1 1.1 1.2 8.9 1.1 1.5 6.6 1.3 1.8 4.7 1.5 2.1 15 27.0 1.0 0.8 18.3 1.1 1.2 13.5 1.1 1.5 10.3 1.2 1.8 7.9 1.3 2.2 6.0 1.5 2.5 20 35.9 1.0 0.8 24.4 1.1 1.2 18.2 1.1 1.5 13.8 1.2 1.8 10.7 1.3 2.2 8.3 1.4 2.6 6.4 1.6 3.0 25 44.9 1.0 0.8 30.5 1.1 1.2 22.8 1.1 1.5 17.5 1.2 1.8 13.4 1.3 2.2 10.6 1.4 2.6 8.3 1.5 3.0 6.4 1.7 3.4 30 53.9 1.0 0.8 36.6 1.1 1.2 27.3 1.1 1.5 20.9 1.2 1.8 16.2 1.3 2.2 12.8 1.4 2.6 10.2 1.5 3.0 8.1 1.6 3.5 6.0 1.9 3.9 35 62.8 1.0 0.8 42.7 1.1 1.2 31.8 1.1 1.5 24.4 1.2 1.8 19.1 1.2 2.2 15.0 1.3 2.6 12.0 1.4 3.0 9.6 1.6 3.5 7.6 1.7 3.9 40 71.8 1.0 0.8 48.8 1.1 1.2 36.4 1.1 1.5 27.9 1.2 1.8 21.9 1.2 2.2 17.2 1.3 2.6 13.8 1.4 3.1 11.1 1.5 3.5 9.0 1.7 4.0 45 80.8 1.0 0.8 54.9 1.0 1.2 40.9 1.1 1.5 31.3 1.2 1.8 24.6 1.2 2.2 19.6 1.3 2.6 15.5 1.4 3.1 12.6 1.5 3.5 10.2 1.7 4.0 50 89.7 1.0 0.8 60.9 1.0 1.2 45.4 1.1 1.5 34.8 1.2 1.8 27.3 1.2 2.2 21.8 1.3 2.6 17.3 1.4 3.1 14.1 1.5 3.5 11.5 1.6 4.0 55 98.7 1.0 0.8 67.0 1.0 1.2 50.0 1.1 1.5 38.3 1.2 1.8 30.0 1.2 2.2 24.0 1.3 2.6 19.1 1.4 3.1 15.5 1.5 3.5 12.7 1.6 4.0 60 107.7 1.0 0.8 73.1 1.0 1.2 54.5 1.1 1.5 41.8 1.2 1.8 32.7 1.2 2.2 26.1 1.3 2.6 21.0 1.4 3.1 16.9 1.5 3.6 14.0 1.6 4.0 65 116.6 1.0 0.8 79.2 1.0 1.2 59.0 1.1 1.5 45.2 1.2 1.8 35.5 1.2 2.2 28.3 1.3 2.6 22.8 1.4 3.1 18.4 1.5 3.6 15.1 1.6 4.0 70 125.6 1.0 0.8 85.3 1.0 1.2 63.6 1.1 1.5 48.7 1.2 1.8 38.2 1.2 2.2 30.5 1.3 2.6 24.5 1.4 3.1 19.8 1.5 3.6 16.3 1.6 4.1 75 134.6 1.0 0.8 91.4 1.0 1.2 68.1 1.1 1.5 52.2 1.2 1.9 40.9 1.2 2.2 32.6 1.3 2.6 26.2 1.4 3.1 21.5 1.5 3.5 17.5 1.6 4.1 80 143.6 1.0 0.8 97.5 1.0 1.2 72.7 1.1 1.5 55.7 1.2 1.9 43.6 1.2 2.2 34.8 1.3 2.6 28.0 1.4 3.1 23.0 1.5 3.5 18.8 1.6 4.1 85 152.5 1.0 0.8 103.6 1.0 1.2 77.2 1.1 1.5 59.1 1.2 1.9 46.3 1.2 2.2 37.0 1.3 2.6 29.7 1.4 3.1 24.4 1.5 3.6 20.0 1.6 4.1 90 161.5 1.0 0.8 109.7 1.0 1.2 81.7 1.1 1.5 62.6 1.2 1.9 49.1 1.2 2.2 39.1 1.3 2.6 31.5 1.4 3.1 25.8 1.5 3.6 21.2 1.6 4.1 95 170.5 1.0 0.8 115.8 1.0 1.2 86.3 1.1 1.5 66.1 1.2 1.9 51.8 1.2 2.2 41.3 1.3 2.6 33.2 1.4 3.1 27.2 1.5 3.6 22.6 1.6 4.0 100 179.5 1.0 0.8 121.9 1.0 1.2 90.8 1.1 1.5 69.6 1.2 1.9 54.5 1.2 2.2 43.5 1.3 2.6 35.0 1.4 3.1 28.7 1.5 3.6 23.8 1.6 4.0 105 188.4 1.0 0.8 128.0 1.0 1.2 95.4 1.1 1.5 73.0 1.2 1.9 57.2 1.2 2.2 45.6 1.3 2.6 36.7 1.4 3.1 30.1 1.5 3.6 25.0 1.6 4.0 110 197.4 1.0 0.8 134.1 1.0 1.2 99.9 1.1 1.5 76.5 1.2 1.9 60.0 1.2 2.2 47.8 1.3 2.6 38.4 1.4 3.1 31.5 1.5 3.6 26.2 1.6 4.0 115 206.4 1.0 0.8 140.1 1.0 1.2 104.4 1.1 1.5 80.0 1.2 1.9 62.7 1.2 2.2 50.0 1.3 2.6 40.2 1.4 3.1 32.9 1.5 3.6 27.4 1.6 4.0 120 215.3 1.0 0.8 146.2 1.0 1.2 109.0 1.1 1.5 83.5 1.2 1.9 65.4 1.2 2.2 52.2 1.3 2.6 41.9 1.4 3.1 34.4 1.5 3.6 28.6 1.6 4.0 125 224.3 1.0 0.8 152.3 1.0 1.2 113.5 1.1 1.5 86.9 1.2 1.9 68.1 1.2 2.2 54.3 1.3 2.6 43.7 1.4 3.1 35.8 1.5 3.6 29.8 1.6 4.0 130 233.3 1.0 0.8 158.4 1.0 1.2 118.1 1.1 1.5 90.4 1.2 1.9 70.9 1.2 2.2 56.5 1.3 2.6 45.4 1.4 3.1 37.2 1.5 3.6 30.9 1.6 4.0 135 242.3 1.0 0.8 164.5 1.0 1.2 122.6 1.1 1.5 93.9 1.2 1.9 73.6 1.2 2.2 58.7 1.3 2.6 47.2 1.4 3.1 38.6 1.5 3.6 32.1 1.6 4.1 140 251.2 1.0 0.8 170.6 1.0 1.2 127.1 1.1 1.5 97.4 1.2 1.9 76.3 1.2 2.2 60.8 1.3 2.6 48.9 1.4 3.1 40.1 1.5 3.6 33.3 1.6 4.1 145 260.2 1.0 0.8 176.7 1.0 1.2 131.7 1.1 1.5 100.9 1.2 1.9 79.0 1.2 2.2 63.0 1.3 2.6 50.7 1.4 3.1 41.5 1.5 3.6 34.5 1.6 4.1 150 269.2 1.0 0.8 182.8 1.0 1.2 136.2 1.1 1.5 104.3 1.2 1.9 81.7 1.2 2.2 65.2 1.3 2.6 52.4 1.4 3.1 42.9 1.5 3.6 35.7 1.6 4.1 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-252 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 4.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 10.1 0.9 0.8 7.0 1.0 1.1 4.9 1.1 1.4 10 20.5 0.9 0.8 14.4 0.9 1.1 10.3 1.0 1.4 7.9 1.1 1.8 6.1 1.2 2.1 4.5 1.4 2.4 15 30.7 0.9 0.8 21.5 0.9 1.1 15.7 1.0 1.4 12.0 1.1 1.8 9.4 1.1 2.1 7.4 1.2 2.5 5.8 1.4 2.8 20 40.9 0.9 0.8 28.6 0.9 1.1 20.9 1.0 1.4 16.3 1.0 1.8 12.6 1.1 2.1 10.1 1.2 2.5 8.0 1.3 2.9 6.3 1.4 3.3 25 51.1 0.9 0.8 35.8 0.9 1.1 26.1 1.0 1.4 20.3 1.0 1.8 16.0 1.1 2.1 12.7 1.2 2.5 10.2 1.3 2.9 8.2 1.4 3.4 6.5 1.5 3.8 30 61.3 0.9 0.8 42.9 0.9 1.1 31.4 1.0 1.4 24.4 1.0 1.8 19.2 1.1 2.1 15.2 1.2 2.5 12.3 1.3 2.9 10.0 1.3 3.4 8.1 1.5 3.8 35 71.5 0.9 0.8 50.1 0.9 1.1 36.6 1.0 1.4 28.3 1.0 1.8 22.4 1.1 2.1 18.0 1.2 2.5 14.4 1.2 2.9 11.7 1.3 3.4 9.6 1.4 3.8 40 81.8 0.9 0.8 57.2 0.9 1.1 41.8 1.0 1.5 32.4 1.0 1.8 25.6 1.1 2.1 20.6 1.2 2.5 16.5 1.2 2.9 13.5 1.3 3.4 11.1 1.4 3.8 45 92.0 0.9 0.8 64.4 0.9 1.1 47.0 1.0 1.5 36.4 1.0 1.8 28.8 1.1 2.1 23.1 1.2 2.5 18.8 1.2 2.9 15.2 1.3 3.4 12.6 1.4 3.9 50 102.2 0.9 0.8 71.5 0.9 1.1 52.2 1.0 1.5 40.5 1.0 1.8 32.0 1.1 2.1 25.7 1.2 2.5 20.9 1.2 2.9 17.0 1.3 3.4 14.0 1.4 3.9 55 112.4 0.9 0.8 78.7 0.9 1.1 57.5 1.0 1.5 44.5 1.0 1.8 35.2 1.1 2.1 28.2 1.2 2.5 23.0 1.2 2.9 18.9 1.3 3.4 15.4 1.4 3.9 60 122.6 0.9 0.8 85.8 0.9 1.1 62.7 1.0 1.5 48.5 1.0 1.8 38.4 1.1 2.2 30.8 1.2 2.5 25.1 1.2 2.9 20.6 1.3 3.4 16.9 1.4 3.9 65 132.8 0.9 0.8 93.0 0.9 1.1 67.9 1.0 1.5 52.6 1.0 1.8 41.5 1.1 2.2 33.4 1.2 2.5 27.2 1.2 2.9 22.3 1.3 3.4 18.3 1.4 3.9 70 143.1 0.9 0.8 100.1 0.9 1.1 73.1 1.0 1.5 56.6 1.0 1.8 44.7 1.1 2.2 35.9 1.2 2.5 29.2 1.2 2.9 24.0 1.3 3.4 20.0 1.4 3.9 75 153.3 0.9 0.8 107.3 0.9 1.1 78.3 1.0 1.5 60.7 1.0 1.8 47.9 1.1 2.2 38.5 1.2 2.5 31.3 1.2 2.9 25.7 1.3 3.4 21.4 1.4 3.9 80 163.5 0.9 0.8 114.4 0.9 1.1 83.6 1.0 1.5 64.7 1.0 1.8 51.1 1.1 2.2 41.0 1.2 2.5 33.4 1.2 2.9 27.4 1.3 3.4 22.8 1.4 3.9 85 173.7 0.9 0.8 121.6 0.9 1.1 88.8 1.0 1.5 68.8 1.0 1.8 54.3 1.1 2.2 43.6 1.2 2.5 35.5 1.2 2.9 29.1 1.3 3.4 24.2 1.4 3.9 90 183.9 0.9 0.8 128.7 0.9 1.1 94.0 1.0 1.5 72.8 1.0 1.8 57.5 1.1 2.2 46.2 1.2 2.5 37.6 1.2 2.9 30.8 1.3 3.4 25.7 1.4 3.9 95 194.1 0.9 0.8 135.9 0.9 1.1 99.2 1.0 1.5 76.8 1.0 1.8 60.7 1.1 2.2 48.7 1.2 2.5 39.7 1.2 2.9 32.5 1.3 3.4 27.1 1.4 3.9 100 204.4 0.9 0.8 143.0 0.9 1.1 104.4 1.0 1.5 80.9 1.0 1.8 63.9 1.1 2.2 51.3 1.2 2.5 41.7 1.2 2.9 34.2 1.3 3.4 28.5 1.3 3.9 105 214.6 0.9 0.8 150.2 0.9 1.1 109.7 1.0 1.5 84.9 1.0 1.8 67.1 1.1 2.2 53.9 1.2 2.5 43.8 1.2 2.9 35.9 1.3 3.4 29.9 1.3 3.9 110 224.8 0.9 0.8 157.4 0.9 1.1 114.9 1.0 1.5 89.0 1.0 1.8 70.3 1.1 2.2 56.4 1.2 2.5 45.9 1.2 2.9 37.6 1.3 3.4 31.3 1.3 3.9 115 235.0 0.9 0.8 164.5 0.9 1.1 120.1 1.0 1.5 93.0 1.0 1.8 73.5 1.1 2.2 59.0 1.2 2.5 48.0 1.2 2.9 39.3 1.3 3.4 32.7 1.3 3.9 120 245.2 0.9 0.8 171.7 0.9 1.1 125.3 1.0 1.5 97.1 1.0 1.8 76.7 1.1 2.2 61.5 1.2 2.5 49.9 1.2 3.0 41.0 1.3 3.4 34.2 1.3 3.9 125 255.5 0.9 0.8 178.8 0.9 1.1 130.5 1.0 1.5 101.1 1.0 1.8 79.9 1.1 2.2 64.1 1.2 2.5 52.0 1.2 3.0 42.7 1.3 3.4 35.6 1.3 3.9 130 265.7 0.9 0.8 186.0 0.9 1.1 135.8 1.0 1.5 105.1 1.0 1.8 83.0 1.1 2.2 66.7 1.2 2.5 54.1 1.2 3.0 44.4 1.3 3.4 37.0 1.3 3.9 135 275.9 0.9 0.8 193.1 0.9 1.1 141.0 1.0 1.5 109.2 1.0 1.8 86.2 1.1 2.2 69.2 1.2 2.5 56.1 1.2 3.0 46.1 1.3 3.4 38.4 1.3 3.9 140 286.1 0.9 0.8 200.3 0.9 1.1 146.2 1.0 1.5 113.2 1.0 1.8 89.4 1.1 2.2 71.8 1.2 2.5 58.2 1.2 3.0 47.8 1.3 3.4 39.9 1.3 3.9 145 296.3 0.9 0.8 207.4 0.9 1.1 151.4 1.0 1.5 117.3 1.0 1.8 92.6 1.1 2.2 74.4 1.2 2.5 60.3 1.2 3.0 49.6 1.3 3.4 41.3 1.3 3.9 150 306.5 0.9 0.8 214.6 0.9 1.1 156.7 1.0 1.5 121.3 1.0 1.8 95.8 1.1 2.2 76.9 1.2 2.5 62.4 1.2 3.0 51.3 1.3 3.4 42.7 1.3 3.9 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-253 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 5.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 11.3 0.8 0.8 8.0 0.9 1.1 5.6 1.0 1.4 4.2 1.1 1.6 10 22.5 0.8 0.8 16.3 0.9 1.1 11.5 0.9 1.4 8.9 1.0 1.7 7.0 1.0 2.0 5.5 1.2 2.4 4.0 1.4 2.6 15 33.7 0.8 0.8 24.3 0.9 1.1 17.4 0.9 1.4 13.7 1.0 1.7 10.7 1.0 2.1 8.5 1.1 2.4 6.8 1.2 2.8 5.4 1.3 3.2 20 45.0 0.8 0.8 32.4 0.9 1.1 23.2 0.9 1.4 18.2 1.0 1.7 14.5 1.0 2.1 11.5 1.1 2.5 9.3 1.1 2.8 7.5 1.2 3.2 6.1 1.4 3.7 25 56.2 0.8 0.8 40.5 0.9 1.1 28.9 0.9 1.4 22.8 1.0 1.7 18.1 1.0 2.1 14.6 1.1 2.4 11.7 1.1 2.8 9.6 1.2 3.3 7.8 1.3 3.7 30 67.4 0.8 0.8 48.7 0.9 1.1 34.7 0.9 1.4 27.3 1.0 1.7 21.7 1.0 2.1 17.5 1.1 2.4 14.1 1.1 2.8 11.6 1.2 3.3 9.5 1.3 3.7 35 78.7 0.8 0.8 56.8 0.9 1.1 40.5 0.9 1.4 31.8 1.0 1.7 25.3 1.0 2.1 20.4 1.0 2.5 16.7 1.1 2.8 13.6 1.2 3.3 11.2 1.3 3.7 40 89.9 0.8 0.8 64.9 0.9 1.1 46.3 0.9 1.4 36.4 1.0 1.7 28.8 1.0 2.1 23.3 1.0 2.5 19.1 1.1 2.8 15.6 1.2 3.3 12.9 1.2 3.7 45 101.1 0.8 0.8 73.0 0.9 1.1 52.1 0.9 1.4 40.9 1.0 1.7 32.4 1.0 2.1 26.2 1.0 2.5 21.5 1.1 2.8 17.7 1.2 3.3 14.6 1.2 3.7 50 112.4 0.8 0.8 81.1 0.9 1.1 57.9 0.9 1.4 45.5 1.0 1.7 36.0 1.0 2.1 29.1 1.0 2.5 23.9 1.1 2.8 19.7 1.2 3.3 16.2 1.2 3.7 55 123.6 0.8 0.8 89.2 0.9 1.1 63.6 0.9 1.4 50.0 1.0 1.7 39.6 1.0 2.1 32.0 1.0 2.5 26.2 1.1 2.8 21.7 1.2 3.3 18.0 1.2 3.8 60 134.8 0.8 0.8 97.3 0.9 1.1 69.4 0.9 1.4 54.5 1.0 1.7 43.2 1.0 2.1 34.9 1.0 2.5 28.6 1.1 2.8 23.6 1.2 3.3 19.7 1.2 3.8 65 146.1 0.8 0.8 105.4 0.9 1.1 75.2 0.9 1.4 59.1 1.0 1.7 46.8 1.0 2.1 37.8 1.0 2.5 31.0 1.1 2.8 25.6 1.2 3.3 21.3 1.2 3.8 70 157.3 0.8 0.8 113.5 0.9 1.1 81.0 0.9 1.4 63.6 1.0 1.7 50.4 1.0 2.1 40.7 1.0 2.5 33.4 1.1 2.8 27.5 1.2 3.3 22.9 1.2 3.8 75 168.6 0.8 0.8 121.6 0.9 1.1 86.8 0.9 1.4 68.2 1.0 1.7 54.0 1.0 2.1 43.6 1.0 2.5 35.8 1.1 2.8 29.4 1.2 3.3 24.5 1.2 3.8 80 179.8 0.8 0.8 129.7 0.9 1.1 92.6 0.9 1.4 72.7 0.9 1.7 57.6 1.0 2.1 46.5 1.0 2.5 38.1 1.1 2.8 31.4 1.2 3.3 26.2 1.2 3.8 85 191.0 0.8 0.8 137.8 0.9 1.1 98.3 0.9 1.4 77.3 0.9 1.7 61.2 1.0 2.1 49.4 1.0 2.5 40.5 1.1 2.8 33.3 1.2 3.3 27.8 1.2 3.8 90 202.3 0.8 0.8 145.9 0.9 1.1 104.1 0.9 1.4 81.8 0.9 1.7 64.9 1.0 2.1 52.3 1.0 2.5 42.9 1.1 2.8 35.3 1.2 3.3 29.4 1.2 3.8 95 213.5 0.8 0.8 154.0 0.9 1.1 109.9 0.9 1.4 86.3 0.9 1.7 68.5 1.0 2.1 55.2 1.0 2.5 45.3 1.1 2.8 37.2 1.2 3.3 31.1 1.2 3.8 100 224.7 0.8 0.8 162.1 0.9 1.1 115.7 0.9 1.4 90.9 0.9 1.7 72.1 1.0 2.1 58.1 1.0 2.5 47.7 1.1 2.8 39.2 1.2 3.3 32.7 1.2 3.8 105 236.0 0.8 0.8 170.2 0.9 1.1 121.5 0.9 1.4 95.4 0.9 1.7 75.7 1.0 2.1 61.0 1.0 2.5 50.0 1.1 2.8 41.1 1.2 3.3 34.3 1.2 3.8 110 247.2 0.8 0.8 178.3 0.9 1.1 127.3 0.9 1.4 100.0 0.9 1.7 79.3 1.0 2.1 64.0 1.0 2.5 52.4 1.1 2.8 43.1 1.2 3.3 36.0 1.2 3.8 115 258.5 0.8 0.8 186.4 0.9 1.1 133.0 0.9 1.4 104.5 0.9 1.7 82.9 1.0 2.1 66.9 1.0 2.5 54.8 1.1 2.8 45.0 1.2 3.3 37.6 1.2 3.8 120 269.7 0.8 0.8 194.6 0.9 1.1 138.8 0.9 1.4 109.1 0.9 1.7 86.5 1.0 2.1 69.8 1.0 2.5 57.2 1.1 2.8 47.0 1.2 3.3 39.2 1.2 3.8 125 280.9 0.8 0.8 202.7 0.9 1.1 144.6 0.9 1.4 113.6 0.9 1.7 90.1 1.0 2.1 72.7 1.0 2.5 59.6 1.1 2.8 48.9 1.2 3.3 40.9 1.2 3.8 130 292.2 0.8 0.8 210.8 0.9 1.1 150.4 0.9 1.4 118.2 0.9 1.7 93.7 1.0 2.1 75.6 1.0 2.5 61.9 1.1 2.8 50.9 1.2 3.3 42.5 1.2 3.8 135 303.4 0.8 0.8 218.9 0.9 1.1 156.2 0.9 1.4 122.7 0.9 1.7 97.3 1.0 2.1 78.5 1.0 2.5 64.3 1.1 2.8 52.9 1.2 3.3 44.1 1.2 3.8 140 314.6 0.8 0.8 227.0 0.9 1.1 162.0 0.9 1.4 127.2 0.9 1.7 100.9 1.0 2.1 81.4 1.0 2.5 66.7 1.1 2.8 54.8 1.2 3.3 45.8 1.2 3.8 145 325.9 0.8 0.8 235.1 0.9 1.1 167.8 0.9 1.4 131.8 0.9 1.7 104.5 1.0 2.1 84.3 1.0 2.5 69.1 1.1 2.8 56.8 1.2 3.3 47.4 1.2 3.8 150 337.1 0.8 0.8 243.2 0.9 1.1 173.5 0.9 1.4 136.3 0.9 1.7 108.1 1.0 2.1 87.2 1.0 2.5 71.5 1.1 2.8 58.7 1.2 3.3 49.0 1.2 3.8 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-254 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 6.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 12.4 0.7 0.8 8.7 0.8 1.0 6.2 0.9 1.4 4.7 1.0 1.6 3.5 1.2 1.9 10 24.7 0.7 0.8 17.6 0.8 1.0 12.8 0.9 1.4 9.8 0.9 1.7 7.8 1.0 2.0 6.2 1.0 2.3 4.9 1.1 2.7 15 37.1 0.7 0.8 26.4 0.8 1.1 19.2 0.8 1.4 15.0 0.9 1.7 11.8 0.9 2.0 9.5 1.0 2.4 7.7 1.1 2.7 6.2 1.2 3.1 5.0 1.3 3.5 20 49.4 0.7 0.8 35.1 0.8 1.1 25.6 0.8 1.4 19.9 0.9 1.7 16.0 0.9 2.0 12.9 1.0 2.4 10.4 1.0 2.8 8.5 1.1 3.2 7.0 1.2 3.6 25 61.8 0.7 0.8 43.9 0.8 1.1 32.0 0.8 1.4 24.9 0.9 1.7 19.9 0.9 2.0 16.1 1.0 2.4 13.1 1.0 2.8 10.8 1.1 3.2 8.9 1.2 3.6 30 74.1 0.7 0.8 52.7 0.8 1.1 38.4 0.8 1.4 29.9 0.9 1.7 23.8 0.9 2.1 19.3 1.0 2.4 15.9 1.0 2.8 13.0 1.1 3.2 10.8 1.1 3.6 35 86.5 0.7 0.8 61.5 0.8 1.1 44.8 0.8 1.4 34.8 0.9 1.7 27.8 0.9 2.1 22.5 1.0 2.4 18.5 1.0 2.8 15.4 1.1 3.2 12.7 1.1 3.6 40 98.9 0.7 0.8 70.2 0.8 1.1 51.2 0.8 1.4 39.8 0.9 1.7 31.8 0.9 2.1 25.7 1.0 2.4 21.2 1.0 2.8 17.6 1.1 3.2 14.5 1.1 3.6 45 111.2 0.7 0.8 79.0 0.8 1.1 57.6 0.8 1.4 44.8 0.9 1.7 35.7 0.9 2.1 29.0 1.0 2.4 23.8 1.0 2.8 19.8 1.1 3.2 16.6 1.1 3.6 50 123.6 0.7 0.8 87.8 0.8 1.1 64.0 0.8 1.4 49.7 0.9 1.7 39.7 0.9 2.1 32.2 1.0 2.4 26.4 1.0 2.8 22.0 1.1 3.2 18.4 1.1 3.6 55 135.9 0.7 0.8 96.6 0.8 1.1 70.4 0.8 1.4 54.7 0.9 1.7 43.6 0.9 2.1 35.4 1.0 2.4 29.1 1.0 2.8 24.2 1.1 3.2 20.2 1.1 3.7 60 148.3 0.7 0.8 105.3 0.8 1.1 76.8 0.8 1.4 59.7 0.9 1.7 47.6 0.9 2.1 38.6 1.0 2.4 31.7 1.0 2.8 26.3 1.1 3.2 22.0 1.1 3.7 65 160.6 0.7 0.8 114.1 0.8 1.1 83.2 0.8 1.4 64.7 0.9 1.7 51.6 0.9 2.1 41.8 1.0 2.4 34.3 1.0 2.8 28.5 1.1 3.2 23.8 1.1 3.7 70 173.0 0.7 0.8 122.9 0.8 1.1 89.6 0.8 1.4 69.6 0.9 1.7 55.5 0.9 2.1 45.0 1.0 2.4 37.0 1.0 2.8 30.7 1.1 3.2 25.6 1.1 3.7 75 185.4 0.7 0.8 131.7 0.8 1.1 96.0 0.8 1.4 74.6 0.9 1.7 59.5 0.9 2.1 48.2 1.0 2.4 39.6 1.0 2.8 32.9 1.1 3.2 27.4 1.1 3.7 80 197.7 0.7 0.8 140.4 0.8 1.1 102.3 0.8 1.4 79.6 0.9 1.7 63.5 0.9 2.1 51.4 1.0 2.4 42.2 1.0 2.8 35.1 1.1 3.2 29.3 1.1 3.7 85 210.1 0.7 0.8 149.2 0.8 1.1 108.7 0.8 1.4 84.5 0.9 1.7 67.4 0.9 2.1 54.7 1.0 2.4 44.9 1.0 2.8 37.3 1.1 3.2 31.1 1.1 3.7 90 222.4 0.7 0.8 158.0 0.8 1.1 115.1 0.8 1.4 89.5 0.9 1.7 71.4 0.9 2.1 57.9 1.0 2.4 47.5 1.0 2.8 39.5 1.1 3.2 32.9 1.1 3.7 95 234.8 0.7 0.8 166.8 0.8 1.1 121.5 0.8 1.4 94.5 0.9 1.7 75.4 0.9 2.1 61.1 1.0 2.4 50.2 1.0 2.8 41.7 1.1 3.2 34.7 1.1 3.7 100 247.1 0.7 0.8 175.5 0.8 1.1 127.9 0.8 1.4 99.5 0.9 1.7 79.3 0.9 2.1 64.3 1.0 2.4 52.8 1.0 2.8 43.9 1.1 3.2 36.6 1.1 3.7 105 259.5 0.7 0.8 184.3 0.8 1.1 134.3 0.8 1.4 104.4 0.9 1.7 83.3 0.9 2.1 67.5 1.0 2.4 55.4 1.0 2.8 46.1 1.1 3.2 38.4 1.1 3.7 110 271.8 0.7 0.8 193.1 0.8 1.1 140.7 0.8 1.4 109.4 0.9 1.7 87.3 0.9 2.1 70.7 1.0 2.4 58.1 1.0 2.8 48.2 1.1 3.2 40.2 1.1 3.7 115 284.2 0.7 0.8 201.9 0.8 1.1 147.1 0.8 1.4 114.4 0.9 1.7 91.2 0.9 2.1 73.9 1.0 2.4 60.7 1.0 2.8 50.4 1.1 3.2 42.0 1.1 3.7 120 296.6 0.7 0.8 210.7 0.8 1.1 153.5 0.8 1.4 119.3 0.9 1.7 95.2 0.9 2.1 77.2 1.0 2.4 63.3 1.0 2.8 52.6 1.1 3.2 43.9 1.1 3.7 125 308.9 0.7 0.8 219.4 0.8 1.1 159.9 0.8 1.4 124.3 0.9 1.7 99.2 0.9 2.1 80.4 1.0 2.4 66.0 1.0 2.8 54.8 1.1 3.2 45.7 1.1 3.7 130 321.3 0.7 0.8 228.2 0.8 1.1 166.3 0.8 1.4 129.3 0.9 1.7 103.1 0.9 2.1 83.6 1.0 2.4 68.6 1.0 2.8 57.0 1.1 3.2 47.5 1.1 3.7 135 333.6 0.7 0.8 237.0 0.8 1.1 172.7 0.8 1.4 134.3 0.9 1.7 107.1 0.9 2.1 86.8 1.0 2.4 71.3 1.0 2.8 59.2 1.1 3.2 49.3 1.1 3.7 140 346.0 0.7 0.8 245.8 0.8 1.1 179.1 0.8 1.4 139.2 0.9 1.7 111.0 0.9 2.1 90.0 1.0 2.4 73.9 1.0 2.8 61.4 1.1 3.2 51.2 1.1 3.7 145 358.3 0.7 0.8 254.5 0.8 1.1 185.5 0.8 1.4 144.2 0.9 1.7 115.0 0.9 2.1 93.2 1.0 2.4 76.5 1.0 2.8 63.6 1.1 3.2 53.0 1.1 3.7 150 370.7 0.7 0.8 263.3 0.8 1.1 191.9 0.8 1.4 149.2 0.9 1.7 119.0 0.9 2.1 96.4 1.0 2.4 79.2 1.0 2.8 65.8 1.1 3.2 54.8 1.1 3.7 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-255 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 8.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 14.0 0.7 0.8 10.1 0.7 1.0 7.4 0.8 1.3 5.5 0.8 1.6 4.4 0.9 1.9 3.4 1.0 2.1 10 28.0 0.7 0.8 20.1 0.7 1.0 15.0 0.8 1.3 11.3 0.8 1.7 9.1 0.8 2.0 7.4 0.9 2.3 6.0 0.9 2.6 4.9 1.0 3.0 3.8 1.2 3.3 15 41.9 0.7 0.8 30.1 0.7 1.0 22.4 0.8 1.3 17.0 0.8 1.7 13.9 0.8 2.0 11.4 0.9 2.3 9.2 0.9 2.7 7.6 1.0 3.0 6.3 1.0 3.4 20 55.9 0.7 0.8 40.1 0.7 1.0 29.9 0.8 1.3 22.6 0.8 1.7 18.5 0.8 2.0 15.1 0.9 2.3 12.5 0.9 2.7 10.2 1.0 3.1 8.5 1.0 3.5 25 69.9 0.7 0.8 50.1 0.7 1.0 37.3 0.8 1.3 28.2 0.8 1.7 23.1 0.8 2.0 18.8 0.9 2.3 15.6 0.9 2.7 13.0 0.9 3.1 10.8 1.0 3.5 30 83.9 0.7 0.8 60.1 0.7 1.0 44.8 0.8 1.3 33.9 0.8 1.7 27.7 0.8 2.0 22.6 0.9 2.3 18.6 0.9 2.7 15.6 0.9 3.1 13.0 1.0 3.5 35 97.9 0.7 0.8 70.1 0.7 1.0 52.3 0.8 1.3 39.5 0.8 1.7 32.3 0.8 2.0 26.3 0.9 2.3 21.7 0.9 2.7 18.2 0.9 3.1 15.3 1.0 3.5 40 111.8 0.7 0.8 80.2 0.7 1.0 59.7 0.8 1.3 45.1 0.8 1.7 36.9 0.8 2.0 30.1 0.9 2.3 24.8 0.9 2.7 20.8 0.9 3.1 17.5 1.0 3.5 45 125.8 0.7 0.8 90.2 0.7 1.0 67.2 0.8 1.3 50.8 0.8 1.7 41.5 0.8 2.0 33.8 0.9 2.3 27.9 0.9 2.7 23.3 0.9 3.1 19.7 1.0 3.5 50 139.8 0.7 0.8 100.2 0.7 1.0 74.7 0.8 1.3 56.4 0.8 1.7 46.1 0.8 2.0 37.6 0.9 2.3 31.0 0.9 2.7 25.9 0.9 3.1 21.9 1.0 3.5 55 153.8 0.7 0.8 110.2 0.7 1.0 82.1 0.8 1.3 62.1 0.8 1.7 50.7 0.8 2.0 41.3 0.9 2.3 34.1 0.9 2.7 28.5 0.9 3.1 24.0 1.0 3.5 60 167.8 0.7 0.8 120.2 0.7 1.0 89.6 0.8 1.3 67.7 0.8 1.7 55.3 0.8 2.0 45.1 0.9 2.3 37.2 0.9 2.7 31.1 0.9 3.1 26.2 1.0 3.5 65 181.7 0.7 0.8 130.3 0.7 1.0 97.0 0.8 1.3 73.3 0.8 1.7 60.0 0.8 2.0 48.8 0.9 2.3 40.3 0.9 2.7 33.7 0.9 3.1 28.4 1.0 3.5 70 195.7 0.7 0.8 140.3 0.7 1.0 104.5 0.8 1.3 79.0 0.8 1.7 64.6 0.8 2.0 52.6 0.9 2.3 43.4 0.9 2.7 36.3 0.9 3.1 30.6 1.0 3.5 75 209.7 0.7 0.8 150.3 0.7 1.0 112.0 0.8 1.3 84.6 0.8 1.7 69.2 0.8 2.0 56.3 0.9 2.3 46.5 0.9 2.7 38.9 0.9 3.1 32.8 1.0 3.5 80 223.7 0.7 0.8 160.3 0.7 1.0 119.4 0.8 1.3 90.3 0.8 1.7 73.8 0.8 2.0 60.1 0.9 2.3 49.6 0.9 2.7 41.4 0.9 3.1 35.0 1.0 3.5 85 237.7 0.7 0.8 170.3 0.7 1.0 126.9 0.8 1.3 95.9 0.8 1.7 78.4 0.8 2.0 63.8 0.9 2.3 52.7 0.9 2.7 44.0 0.9 3.1 37.1 1.0 3.5 90 251.6 0.7 0.8 180.3 0.7 1.0 134.4 0.8 1.3 101.6 0.8 1.7 83.0 0.8 2.0 67.6 0.9 2.3 55.8 0.9 2.7 46.6 0.9 3.1 39.3 1.0 3.5 95 265.6 0.7 0.8 190.4 0.7 1.0 141.8 0.8 1.3 107.2 0.8 1.7 87.6 0.8 2.0 71.3 0.9 2.3 58.9 0.9 2.7 49.2 0.9 3.1 41.5 1.0 3.5 100 279.6 0.7 0.8 200.4 0.7 1.0 149.3 0.8 1.3 112.8 0.8 1.7 92.2 0.8 2.0 75.1 0.9 2.3 62.0 0.9 2.7 51.8 0.9 3.1 43.7 1.0 3.5 105 293.6 0.7 0.8 210.4 0.7 1.0 156.8 0.8 1.3 118.5 0.8 1.7 96.8 0.8 2.0 78.9 0.9 2.3 65.1 0.9 2.7 54.4 0.9 3.1 45.9 1.0 3.5 110 307.6 0.7 0.8 220.4 0.7 1.0 164.2 0.8 1.3 124.1 0.8 1.7 101.4 0.8 2.0 82.6 0.9 2.3 68.2 0.9 2.7 57.0 0.9 3.1 48.0 1.0 3.5 115 321.5 0.7 0.8 230.4 0.7 1.0 171.7 0.8 1.3 129.8 0.8 1.7 106.1 0.8 2.0 86.4 0.9 2.3 71.3 0.9 2.7 59.6 0.9 3.1 50.2 1.0 3.5 120 335.5 0.7 0.8 240.5 0.7 1.0 179.1 0.8 1.3 135.4 0.8 1.7 110.7 0.8 2.0 90.1 0.9 2.3 74.4 0.9 2.7 62.2 0.9 3.1 52.4 1.0 3.5 125 349.5 0.7 0.8 250.5 0.7 1.0 186.6 0.8 1.3 141.0 0.8 1.7 115.3 0.8 2.0 93.9 0.9 2.3 77.5 0.9 2.7 64.7 0.9 3.1 54.6 1.0 3.5 130 363.5 0.7 0.8 260.5 0.7 1.0 194.1 0.8 1.3 146.7 0.8 1.7 119.9 0.8 2.0 97.6 0.9 2.3 80.6 0.9 2.7 67.3 0.9 3.1 56.8 1.0 3.5 135 377.5 0.7 0.8 270.5 0.7 1.0 201.5 0.8 1.3 152.3 0.8 1.7 124.5 0.8 2.0 101.4 0.9 2.3 83.7 0.9 2.7 69.9 0.9 3.1 59.0 1.0 3.5 140 391.5 0.7 0.8 280.5 0.7 1.0 209.0 0.8 1.3 158.0 0.8 1.7 129.1 0.8 2.0 105.1 0.9 2.3 86.8 0.9 2.7 72.5 0.9 3.1 61.1 1.0 3.5 145 405.4 0.7 0.8 290.6 0.7 1.0 216.5 0.8 1.3 163.6 0.8 1.7 133.7 0.8 2.0 108.9 0.9 2.3 89.9 0.9 2.7 75.1 0.9 3.1 63.3 1.0 3.5 150 419.4 0.7 0.8 300.6 0.7 1.0 223.9 0.8 1.3 169.3 0.8 1.7 138.3 0.8 2.0 112.6 0.9 2.3 93.0 0.9 2.7 77.7 0.9 3.1 65.5 1.0 3.5 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-256 2016 Edition Table 6-28.1. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 10.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 15.3 0.6 0.8 11.1 0.7 1.0 8.1 0.7 1.3 6.3 0.7 1.6 4.8 0.8 1.9 4.0 0.9 2.2 3.1 1.0 2.4 10 30.6 0.6 0.8 22.1 0.7 1.0 16.5 0.7 1.3 12.8 0.7 1.6 10.0 0.8 2.0 8.4 0.8 2.2 6.9 0.8 2.6 5.7 0.9 2.9 4.7 1.0 3.3 15 45.9 0.6 0.8 33.2 0.7 1.0 24.7 0.7 1.3 19.2 0.7 1.6 15.0 0.8 2.0 12.7 0.8 2.2 10.5 0.8 2.6 8.7 0.9 3.0 7.3 0.9 3.3 20 61.2 0.6 0.8 44.2 0.7 1.0 32.9 0.7 1.3 25.6 0.7 1.6 20.0 0.8 2.0 17.0 0.8 2.2 14.1 0.8 2.6 11.8 0.9 3.0 9.8 0.9 3.4 25 76.5 0.6 0.8 55.3 0.7 1.0 41.1 0.7 1.3 32.0 0.7 1.6 25.0 0.8 2.0 21.2 0.8 2.3 17.6 0.8 2.6 14.7 0.9 3.0 12.5 0.9 3.4 30 91.8 0.6 0.8 66.3 0.7 1.0 49.3 0.7 1.3 38.3 0.7 1.6 29.9 0.8 2.0 25.4 0.8 2.3 21.1 0.8 2.6 17.7 0.8 3.0 15.0 0.9 3.3 35 107.1 0.6 0.8 77.4 0.7 1.0 57.5 0.7 1.3 44.7 0.7 1.6 34.9 0.8 2.0 29.7 0.8 2.3 24.6 0.8 2.6 20.6 0.8 3.0 17.5 0.9 3.4 40 122.4 0.6 0.8 88.4 0.7 1.0 65.7 0.7 1.3 51.1 0.7 1.6 39.9 0.8 2.0 33.9 0.8 2.3 28.1 0.8 2.6 23.5 0.8 3.0 20.0 0.9 3.4 45 137.8 0.6 0.8 99.5 0.7 1.0 73.9 0.7 1.3 57.5 0.7 1.6 44.9 0.8 2.0 38.0 0.8 2.3 31.6 0.8 2.6 26.5 0.8 3.0 22.5 0.9 3.4 50 153.1 0.6 0.8 110.6 0.7 1.0 82.1 0.7 1.3 63.9 0.7 1.6 49.9 0.8 2.0 42.2 0.8 2.3 35.1 0.8 2.6 29.4 0.8 3.0 25.0 0.9 3.4 55 168.4 0.6 0.8 121.6 0.7 1.0 90.3 0.7 1.3 70.3 0.7 1.6 54.9 0.8 2.0 46.4 0.8 2.3 38.6 0.8 2.6 32.3 0.8 3.0 27.5 0.9 3.4 60 183.7 0.6 0.8 132.7 0.7 1.0 98.5 0.7 1.3 76.7 0.7 1.6 59.9 0.8 2.0 50.7 0.8 2.3 42.1 0.8 2.6 35.3 0.8 3.0 30.0 0.9 3.4 65 199.0 0.6 0.8 143.7 0.7 1.0 106.7 0.7 1.3 83.1 0.7 1.6 64.8 0.8 2.0 54.9 0.8 2.3 45.6 0.8 2.6 38.2 0.8 3.0 32.5 0.9 3.4 70 214.3 0.6 0.8 154.8 0.7 1.0 115.0 0.7 1.3 89.4 0.7 1.6 69.8 0.8 2.0 59.1 0.8 2.3 49.1 0.8 2.6 41.2 0.8 3.0 35.0 0.9 3.4 75 229.6 0.6 0.8 165.8 0.7 1.0 123.2 0.7 1.3 95.8 0.7 1.6 74.8 0.8 2.0 63.3 0.8 2.3 52.6 0.8 2.6 44.1 0.8 3.0 37.4 0.9 3.4 80 244.9 0.6 0.8 176.9 0.7 1.0 131.4 0.7 1.3 102.2 0.7 1.6 79.8 0.8 2.0 67.6 0.8 2.3 56.1 0.8 2.6 47.0 0.8 3.0 39.8 0.9 3.4 85 260.2 0.6 0.8 187.9 0.7 1.0 139.6 0.7 1.3 108.6 0.7 1.6 84.8 0.8 2.0 71.8 0.8 2.3 59.6 0.8 2.6 50.0 0.8 3.0 42.3 0.9 3.4 90 275.5 0.6 0.8 199.0 0.7 1.0 147.8 0.7 1.3 115.0 0.7 1.6 89.8 0.8 2.0 76.0 0.8 2.3 63.1 0.8 2.6 52.9 0.8 3.0 44.8 0.9 3.4 95 290.8 0.6 0.8 210.0 0.7 1.0 156.0 0.7 1.3 121.4 0.7 1.6 94.8 0.8 2.0 80.2 0.8 2.3 66.6 0.8 2.6 55.8 0.8 3.0 47.3 0.9 3.4 100 306.1 0.6 0.8 221.1 0.7 1.0 164.2 0.7 1.3 127.8 0.7 1.6 99.8 0.8 2.0 84.4 0.8 2.3 70.1 0.8 2.6 58.8 0.8 3.0 49.7 0.9 3.4 105 321.4 0.6 0.8 232.2 0.7 1.0 172.4 0.7 1.3 134.2 0.7 1.6 104.7 0.8 2.0 88.7 0.8 2.3 73.6 0.8 2.6 61.7 0.8 3.0 52.2 0.9 3.4 110 336.7 0.6 0.8 243.2 0.7 1.0 180.6 0.7 1.3 140.5 0.7 1.6 109.7 0.8 2.0 92.9 0.8 2.3 77.1 0.8 2.6 64.7 0.8 3.0 54.7 0.9 3.4 115 352.0 0.6 0.8 254.3 0.7 1.0 188.8 0.7 1.3 146.9 0.7 1.6 114.7 0.8 2.0 97.1 0.8 2.3 80.6 0.8 2.6 67.6 0.8 3.0 57.2 0.9 3.4 120 367.3 0.6 0.8 265.3 0.7 1.0 197.1 0.7 1.3 153.3 0.7 1.6 119.7 0.8 2.0 101.3 0.8 2.3 84.1 0.8 2.6 70.5 0.8 3.0 59.7 0.9 3.4 125 382.6 0.6 0.8 276.4 0.7 1.0 205.3 0.7 1.3 159.7 0.7 1.6 124.7 0.8 2.0 105.5 0.8 2.3 87.6 0.8 2.6 73.5 0.8 3.0 62.2 0.9 3.4 130 397.9 0.6 0.8 287.4 0.7 1.0 213.5 0.7 1.3 166.1 0.7 1.6 129.7 0.8 2.0 109.8 0.8 2.3 91.1 0.8 2.6 76.4 0.8 3.0 64.7 0.9 3.4 135 413.2 0.6 0.8 298.5 0.7 1.0 221.7 0.7 1.3 172.5 0.7 1.6 134.7 0.8 2.0 114.0 0.8 2.3 94.6 0.8 2.6 79.3 0.8 3.0 67.2 0.9 3.4 140 428.6 0.6 0.8 309.5 0.7 1.0 229.9 0.7 1.3 178.9 0.7 1.6 139.7 0.8 2.0 118.2 0.8 2.3 98.1 0.8 2.6 82.3 0.8 3.0 69.6 0.9 3.4 145 443.9 0.6 0.8 320.6 0.7 1.0 238.1 0.7 1.3 185.3 0.7 1.6 144.6 0.8 2.0 122.4 0.8 2.3 101.7 0.8 2.6 85.2 0.8 3.0 72.1 0.9 3.4 150 459.2 0.6 0.8 331.7 0.7 1.0 246.3 0.7 1.3 191.6 0.7 1.6 149.6 0.8 2.0 126.7 0.8 2.3 105.2 0.8 2.6 88.2 0.9 3.0 74.6 0.9 3.4 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.1. Table 6-39.1. ---PAGE BREAK--- 6-257 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 0.25 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 10 15 20 25 9.3 2.3 1.7 30 11.7 2.2 1.8 35 14.1 2.1 1.7 40 16.3 2.1 1.8 45 18.5 2.1 1.8 10.4 2.8 2.3 50 20.7 2.1 1.8 12.3 2.6 2.3 55 22.9 2.1 1.8 13.8 2.6 2.3 60 25.0 2.0 1.8 15.3 2.5 2.3 65 27.2 2.0 1.8 16.8 2.5 2.3 10.4 3.4 2.8 70 29.3 2.0 1.8 18.2 2.5 2.3 12.1 3.1 2.8 75 31.9 2.0 1.7 19.7 2.4 2.3 13.5 3.0 2.8 80 34.0 2.0 1.7 21.1 2.4 2.3 14.7 2.9 2.8 85 36.1 2.0 1.7 22.5 2.4 2.3 15.8 2.9 2.8 90 38.2 2.0 1.7 23.9 2.4 2.3 16.9 2.8 2.8 95 40.3 2.0 1.7 25.3 2.4 2.3 18.0 2.8 2.8 100 42.4 2.0 1.7 26.7 2.4 2.3 19.1 2.8 2.8 105 44.6 2.0 1.7 28.1 2.4 2.3 20.2 2.8 2.8 110 46.7 2.0 1.7 29.5 2.4 2.3 21.3 2.8 2.8 12.9 3.8 3.4 115 48.8 2.0 1.7 30.8 2.4 2.3 22.3 2.8 2.8 14.0 3.7 3.4 120 50.9 2.0 1.7 32.2 2.4 2.3 23.4 2.8 2.8 15.3 3.5 3.4 125 53.0 2.0 1.8 33.6 2.4 2.3 24.4 2.8 2.8 16.1 3.5 3.4 130 55.1 2.0 1.8 35.0 2.4 2.3 25.5 2.8 2.8 16.9 3.4 3.4 135 57.3 2.0 1.8 36.4 2.4 2.3 26.5 2.7 2.8 17.7 3.4 3.4 140 59.4 2.0 1.8 38.3 2.4 2.3 27.6 2.7 2.8 18.5 3.4 3.4 145 61.5 2.0 1.8 39.7 2.4 2.3 28.6 2.7 2.8 19.3 3.3 3.4 150 63.6 2.0 1.8 41.1 2.4 2.3 29.6 2.7 2.8 20.1 3.3 3.4 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. = Top width, tall vegetation = Depth, tall vegetation = Design velocity, tall vegetation = Permissible velocity, short vegetation T D V2 V1 T D Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-258 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 0.50 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 10 15 8.4 1.6 1.7 20 11.7 1.5 1.7 7.1 2.0 2.2 25 14.9 1.5 1.7 9.7 1.8 2.2 30 18.0 1.5 1.7 12.0 1.7 2.2 35 21.0 1.5 1.7 14.2 1.7 2.2 9.3 2.1 2.7 40 24.4 1.5 1.7 16.3 1.7 2.2 10.9 2.0 2.7 45 27.4 1.5 1.7 18.5 1.7 2.2 12.5 2.0 2.7 50 30.5 1.5 1.7 20.6 1.7 2.2 14.1 1.9 2.7 8.7 2.6 3.3 55 33.5 1.5 1.7 22.7 1.7 2.2 15.7 1.9 2.7 10.4 2.4 3.3 60 36.6 1.5 1.7 24.8 1.7 2.2 17.2 1.9 2.7 11.7 2.3 3.3 65 39.6 1.5 1.7 27.3 1.7 2.2 18.8 1.9 2.7 12.9 2.3 3.3 70 42.6 1.5 1.7 29.4 1.7 2.2 20.3 1.9 2.7 14.0 2.2 3.3 9.8 2.8 3.8 75 45.7 1.5 1.7 31.4 1.7 2.2 21.8 1.9 2.7 15.2 2.2 3.3 11.3 2.7 3.8 80 48.7 1.5 1.7 33.5 1.7 2.2 23.3 1.9 2.7 16.3 2.2 3.3 12.2 2.6 3.8 85 51.7 1.5 1.7 35.6 1.6 2.2 24.8 1.9 2.7 17.4 2.2 3.3 13.2 2.5 3.8 90 54.8 1.5 1.7 37.7 1.6 2.2 26.3 1.9 2.7 18.5 2.2 3.3 14.2 2.5 3.8 95 57.8 1.5 1.7 39.8 1.6 2.2 27.8 1.9 2.7 19.6 2.2 3.3 15.1 2.5 3.8 100 60.9 1.5 1.7 41.9 1.6 2.2 29.7 1.9 2.7 20.7 2.2 3.3 16.0 2.5 3.8 11.0 3.2 4.3 105 63.9 1.5 1.7 44.0 1.6 2.2 31.2 1.9 2.7 21.8 2.2 3.3 16.9 2.5 3.8 12.3 3.0 4.3 110 66.9 1.5 1.7 46.1 1.6 2.2 32.6 1.9 2.7 22.9 2.2 3.3 17.8 2.4 3.8 13.1 2.9 4.3 115 70.0 1.5 1.7 48.1 1.6 2.2 34.1 1.9 2.7 24.0 2.1 3.3 18.7 2.4 3.8 13.9 2.9 4.3 120 73.0 1.5 1.7 50.2 1.6 2.2 35.6 1.9 2.7 25.1 2.1 3.3 19.6 2.4 3.8 14.6 2.9 4.3 125 76.1 1.5 1.7 52.3 1.6 2.2 37.1 1.9 2.7 26.2 2.1 3.3 20.5 2.4 3.8 15.4 2.8 4.3 130 79.1 1.5 1.7 54.4 1.6 2.2 38.5 1.9 2.7 27.3 2.1 3.3 21.3 2.4 3.8 16.1 2.8 4.3 135 82.1 1.5 1.7 56.5 1.6 2.2 40.0 1.9 2.7 28.4 2.1 3.3 22.2 2.4 3.8 16.9 2.8 4.3 140 85.2 1.5 1.7 58.6 1.6 2.2 41.5 1.9 2.7 29.4 2.1 3.3 23.1 2.4 3.8 17.6 2.8 4.3 145 88.2 1.5 1.7 60.7 1.6 2.2 43.0 1.9 2.7 30.5 2.1 3.3 24.0 2.4 3.8 18.3 2.8 4.3 12.3 3.7 4.9 150 91.3 1.5 1.7 62.8 1.6 2.2 44.5 1.9 2.7 31.6 2.1 3.3 24.8 2.4 3.8 19.0 2.7 4.3 13.1 3.5 4.9 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-259 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 0.75 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 10 7.0 1.3 1.6 15 11.0 1.3 1.6 7.1 1.5 2.1 20 14.9 1.3 1.6 9.9 1.4 2.1 6.1 1.9 2.6 25 18.9 1.2 1.6 12.7 1.4 2.1 8.6 1.6 2.7 30 22.7 1.2 1.6 15.3 1.4 2.1 10.6 1.6 2.6 6.7 2.1 3.2 35 26.5 1.2 1.6 18.0 1.4 2.1 12.6 1.6 2.7 8.7 1.9 3.2 40 30.2 1.2 1.6 20.6 1.4 2.1 14.5 1.6 2.7 10.3 1.8 3.2 45 34.0 1.2 1.6 23.5 1.4 2.1 16.4 1.5 2.7 11.8 1.8 3.2 7.8 2.3 3.8 50 37.8 1.2 1.6 26.1 1.4 2.1 18.3 1.5 2.7 13.2 1.8 3.2 9.5 2.1 3.8 55 41.5 1.2 1.6 28.7 1.4 2.1 20.2 1.5 2.7 14.7 1.7 3.2 10.7 2.0 3.8 60 45.3 1.2 1.6 31.3 1.4 2.1 22.1 1.5 2.7 16.1 1.7 3.2 11.8 2.0 3.8 65 49.1 1.2 1.6 33.9 1.4 2.1 24.3 1.5 2.6 17.6 1.7 3.2 13.0 2.0 3.8 8.5 2.6 4.4 70 52.9 1.2 1.6 36.5 1.4 2.1 26.2 1.5 2.6 19.0 1.7 3.2 14.1 2.0 3.8 10.0 2.4 4.3 75 56.6 1.2 1.6 39.1 1.4 2.1 28.0 1.5 2.6 20.4 1.7 3.2 15.2 2.0 3.8 11.0 2.4 4.4 80 60.4 1.2 1.6 41.7 1.4 2.1 29.9 1.5 2.6 21.8 1.7 3.2 16.3 1.9 3.8 11.9 2.3 4.4 85 64.2 1.2 1.6 44.3 1.4 2.1 31.8 1.5 2.6 23.2 1.7 3.2 17.4 1.9 3.8 12.8 2.3 4.4 9.1 2.9 4.8 90 67.9 1.2 1.6 46.9 1.4 2.1 33.6 1.5 2.6 24.6 1.7 3.2 18.5 1.9 3.8 13.7 2.3 4.4 10.3 2.7 4.8 95 71.7 1.2 1.6 49.5 1.4 2.1 35.5 1.5 2.6 26.0 1.7 3.2 19.6 1.9 3.8 14.6 2.2 4.4 11.4 2.6 4.8 100 75.5 1.2 1.6 52.1 1.4 2.1 37.3 1.5 2.6 27.8 1.7 3.2 20.7 1.9 3.8 15.4 2.2 4.4 12.2 2.6 4.8 105 79.3 1.2 1.6 54.7 1.4 2.1 39.2 1.5 2.6 29.1 1.7 3.2 21.8 1.9 3.8 16.3 2.2 4.4 12.9 2.5 4.8 110 83.0 1.2 1.6 57.3 1.4 2.1 41.1 1.5 2.6 30.5 1.7 3.2 22.8 1.9 3.8 17.2 2.2 4.4 13.7 2.5 4.8 115 86.8 1.2 1.6 59.9 1.4 2.1 42.9 1.5 2.6 31.9 1.7 3.2 23.9 1.9 3.8 18.0 2.2 4.4 14.4 2.5 4.8 10.5 3.1 5.3 120 90.6 1.2 1.6 62.5 1.4 2.1 44.8 1.5 2.7 33.3 1.7 3.2 25.0 1.9 3.8 18.9 2.2 4.4 15.2 2.5 4.8 11.4 3.0 5.3 125 94.3 1.2 1.6 65.1 1.4 2.1 46.7 1.5 2.7 34.7 1.7 3.2 26.0 1.9 3.8 19.7 2.2 4.4 15.9 2.4 4.8 12.4 2.9 5.3 130 98.1 1.2 1.6 67.7 1.4 2.1 48.5 1.5 2.7 36.0 1.7 3.2 27.1 1.9 3.8 20.5 2.2 4.4 16.6 2.4 4.8 13.0 2.8 5.3 135 101.9 1.2 1.6 70.3 1.4 2.1 50.4 1.5 2.7 37.4 1.7 3.2 28.2 1.9 3.8 21.4 2.2 4.4 17.3 2.4 4.8 13.7 2.8 5.3 140 105.7 1.2 1.6 72.9 1.4 2.1 52.2 1.5 2.7 38.8 1.7 3.2 29.3 1.9 3.8 22.2 2.2 4.4 18.0 2.4 4.9 14.3 2.8 5.3 145 109.4 1.2 1.6 75.5 1.4 2.1 54.1 1.5 2.7 40.2 1.7 3.2 30.8 1.9 3.7 23.1 2.2 4.4 18.7 2.4 4.9 14.9 2.7 5.3 150 113.2 1.2 1.6 78.1 1.4 2.1 56.0 1.5 2.7 41.6 1.7 3.2 31.9 1.9 3.7 23.9 2.1 4.4 19.4 2.4 4.9 15.5 2.7 5.3 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-260 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 1.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 10 8.2 1.2 1.6 5.2 1.4 2.0 15 12.6 1.1 1.6 8.7 1.3 2.1 5.5 1.6 2.6 20 17.1 1.1 1.6 11.8 1.2 2.1 8.2 1.4 2.6 25 21.4 1.1 1.6 14.9 1.2 2.1 10.5 1.4 2.6 7.3 1.6 3.1 30 25.7 1.1 1.6 18.0 1.2 2.1 12.8 1.4 2.6 9.1 1.6 3.2 35 29.9 1.1 1.6 21.2 1.2 2.1 15.0 1.3 2.6 10.9 1.5 3.1 7.8 1.8 3.7 40 34.2 1.1 1.6 24.3 1.2 2.1 17.3 1.3 2.6 12.6 1.5 3.1 9.2 1.7 3.7 45 38.5 1.1 1.6 27.3 1.2 2.1 19.5 1.3 2.6 14.3 1.5 3.1 10.6 1.7 3.7 7.2 2.2 4.3 50 42.7 1.1 1.6 30.3 1.2 2.1 21.9 1.3 2.6 16.0 1.5 3.2 11.9 1.7 3.7 8.8 2.0 4.3 55 47.0 1.1 1.6 33.3 1.2 2.1 24.1 1.3 2.6 17.7 1.5 3.2 13.3 1.7 3.7 9.9 1.9 4.3 60 51.3 1.1 1.6 36.3 1.2 2.1 26.3 1.3 2.6 19.3 1.5 3.2 14.6 1.7 3.7 11.0 1.9 4.3 65 55.5 1.1 1.6 39.4 1.2 2.1 28.5 1.3 2.6 21.0 1.5 3.2 15.9 1.6 3.7 12.1 1.9 4.3 8.0 2.5 4.9 70 59.8 1.1 1.6 42.4 1.2 2.1 30.7 1.3 2.6 22.7 1.5 3.2 17.1 1.6 3.7 13.2 1.9 4.3 9.5 2.3 4.8 75 64.1 1.1 1.6 45.4 1.2 2.1 32.9 1.3 2.6 24.6 1.5 3.1 18.5 1.6 3.7 14.2 1.8 4.3 10.4 2.2 4.9 80 68.3 1.1 1.6 48.4 1.2 2.1 35.0 1.3 2.6 26.2 1.5 3.1 19.8 1.6 3.7 15.2 1.8 4.3 11.3 2.2 4.9 85 72.6 1.1 1.6 51.5 1.2 2.1 37.2 1.3 2.6 27.9 1.5 3.1 21.0 1.6 3.7 16.3 1.8 4.3 12.1 2.2 4.9 8.8 2.7 5.4 90 76.9 1.1 1.6 54.5 1.2 2.1 39.4 1.3 2.6 29.5 1.5 3.1 22.3 1.6 3.7 17.3 1.8 4.3 13.0 2.1 4.9 9.8 2.6 5.4 95 81.1 1.1 1.6 57.5 1.2 2.1 41.6 1.3 2.6 31.1 1.5 3.1 23.6 1.6 3.7 18.3 1.8 4.3 13.8 2.1 4.9 10.9 2.5 5.3 100 85.4 1.1 1.6 60.5 1.2 2.1 43.8 1.3 2.6 32.7 1.5 3.1 24.9 1.6 3.7 19.3 1.8 4.3 14.6 2.1 4.9 11.6 2.4 5.4 105 89.7 1.1 1.6 63.6 1.2 2.1 46.0 1.3 2.6 34.4 1.5 3.1 26.5 1.6 3.7 20.3 1.8 4.3 15.4 2.1 4.9 12.4 2.4 5.4 9.7 2.8 5.8 110 94.0 1.1 1.6 66.6 1.2 2.1 48.2 1.3 2.6 36.0 1.5 3.1 27.7 1.6 3.7 21.3 1.8 4.3 16.2 2.1 4.9 13.1 2.4 5.4 10.8 2.6 5.8 115 98.2 1.1 1.6 69.6 1.2 2.1 50.4 1.3 2.6 37.6 1.5 3.1 29.0 1.6 3.7 22.3 1.8 4.3 17.0 2.1 4.9 13.8 2.3 5.4 11.5 2.6 5.8 120 102.5 1.1 1.6 72.6 1.2 2.1 52.5 1.3 2.6 39.3 1.5 3.1 30.2 1.6 3.7 23.3 1.8 4.3 17.9 2.1 4.9 14.5 2.3 5.4 12.2 2.6 5.8 125 106.8 1.1 1.6 75.7 1.2 2.1 54.7 1.3 2.6 40.9 1.5 3.1 31.5 1.6 3.7 24.3 1.8 4.3 18.7 2.1 4.9 15.2 2.3 5.4 12.8 2.5 5.8 130 111.0 1.1 1.6 78.7 1.2 2.1 56.9 1.3 2.6 42.5 1.5 3.1 32.7 1.6 3.7 25.3 1.8 4.3 19.4 2.1 4.9 15.9 2.3 5.4 13.4 2.5 5.8 135 115.3 1.1 1.6 81.7 1.2 2.1 59.1 1.3 2.6 44.2 1.5 3.1 34.0 1.6 3.7 26.3 1.8 4.3 20.2 2.0 4.9 16.6 2.3 5.4 14.1 2.5 5.8 140 119.6 1.1 1.6 84.7 1.2 2.1 61.3 1.3 2.6 45.8 1.5 3.1 35.2 1.6 3.7 27.3 1.8 4.3 21.0 2.0 4.9 17.2 2.3 5.4 14.7 2.5 5.8 145 123.8 1.1 1.6 87.8 1.2 2.1 63.5 1.3 2.6 47.5 1.5 3.1 36.5 1.6 3.7 28.7 1.8 4.3 21.8 2.0 4.9 17.9 2.3 5.4 15.3 2.5 5.8 150 128.1 1.1 1.6 90.8 1.2 2.1 65.7 1.3 2.6 49.1 1.5 3.1 37.8 1.6 3.7 29.7 1.8 4.3 22.6 2.0 4.9 18.6 2.3 5.4 15.9 2.4 5.8 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-261 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 1.25 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 4.1 1.2 1.5 10 9.4 1.0 1.5 6.3 1.2 2.0 15 14.3 1.0 1.6 9.9 1.1 2.0 6.8 1.3 2.6 20 19.4 1.0 1.5 13.4 1.1 2.0 9.5 1.2 2.6 6.7 1.4 3.1 25 24.2 1.0 1.5 17.0 1.1 2.0 12.1 1.2 2.6 8.8 1.4 3.1 5.9 1.7 3.6 30 29.0 1.0 1.6 20.4 1.1 2.0 14.6 1.2 2.6 10.7 1.4 3.1 7.8 1.6 3.7 35 33.8 1.0 1.6 23.8 1.1 2.0 17.1 1.2 2.6 12.7 1.3 3.1 9.4 1.5 3.7 6.5 1.9 4.2 40 38.6 1.0 1.6 27.1 1.1 2.0 19.8 1.2 2.5 14.6 1.3 3.1 10.9 1.5 3.7 8.1 1.7 4.2 45 43.5 1.0 1.6 30.5 1.1 2.0 22.3 1.2 2.5 16.5 1.3 3.1 12.5 1.5 3.7 9.4 1.7 4.2 50 48.3 1.0 1.6 33.9 1.1 2.0 24.8 1.2 2.5 18.3 1.3 3.1 13.9 1.5 3.7 10.6 1.7 4.2 7.7 2.0 4.8 55 53.1 1.0 1.6 37.3 1.1 2.0 27.2 1.2 2.6 20.5 1.3 3.1 15.4 1.5 3.7 11.8 1.6 4.3 9.0 1.9 4.8 60 57.9 1.0 1.6 40.7 1.1 2.0 29.7 1.2 2.6 22.3 1.3 3.1 16.9 1.5 3.7 13.0 1.6 4.3 10.1 1.9 4.8 65 62.8 1.0 1.6 44.1 1.1 2.0 32.2 1.2 2.6 24.2 1.3 3.1 18.3 1.5 3.7 14.2 1.6 4.3 11.1 1.8 4.8 8.0 2.3 5.3 70 67.6 1.0 1.6 47.5 1.1 2.0 34.6 1.2 2.6 26.0 1.3 3.1 19.8 1.4 3.7 15.4 1.6 4.3 12.0 1.8 4.8 9.3 2.1 5.3 75 72.4 1.0 1.6 50.8 1.1 2.0 37.1 1.2 2.6 27.9 1.3 3.1 21.2 1.4 3.7 16.5 1.6 4.3 13.0 1.8 4.8 10.1 2.1 5.3 80 77.2 1.0 1.6 54.2 1.1 2.0 39.6 1.2 2.6 29.7 1.3 3.1 23.0 1.4 3.6 17.7 1.6 4.3 14.0 1.8 4.8 11.0 2.0 5.3 85 82.1 1.0 1.6 57.6 1.1 2.0 42.0 1.2 2.6 31.6 1.3 3.1 24.4 1.4 3.6 18.8 1.6 4.3 14.9 1.8 4.8 11.8 2.0 5.3 90 86.9 1.0 1.6 61.0 1.1 2.0 44.5 1.2 2.6 33.5 1.3 3.1 25.8 1.4 3.6 20.0 1.6 4.3 15.9 1.8 4.8 12.6 2.0 5.3 9.1 2.5 5.9 95 91.7 1.0 1.6 64.4 1.1 2.0 47.0 1.2 2.6 35.3 1.3 3.1 27.3 1.4 3.6 21.1 1.6 4.3 16.8 1.8 4.8 13.4 2.0 5.4 10.2 2.4 5.9 100 96.6 1.0 1.6 67.8 1.1 2.0 49.4 1.2 2.6 37.2 1.3 3.1 28.7 1.4 3.6 22.3 1.6 4.3 17.7 1.8 4.8 14.2 2.0 5.4 10.9 2.3 5.9 105 101.4 1.0 1.6 71.2 1.1 2.0 51.9 1.2 2.6 39.0 1.3 3.1 30.1 1.4 3.6 23.4 1.6 4.3 18.7 1.8 4.8 15.0 2.0 5.4 11.6 2.3 5.9 110 106.2 1.0 1.6 74.6 1.1 2.0 54.4 1.2 2.6 40.9 1.3 3.1 31.6 1.4 3.6 24.6 1.6 4.3 19.6 1.7 4.8 15.8 2.0 5.4 12.3 2.3 5.9 115 111.0 1.0 1.6 78.0 1.1 2.0 56.8 1.2 2.6 42.7 1.3 3.1 33.0 1.4 3.6 26.1 1.6 4.2 20.5 1.7 4.8 16.6 1.9 5.4 13.0 2.2 5.9 120 115.9 1.0 1.6 81.3 1.1 2.0 59.3 1.2 2.6 44.6 1.3 3.1 34.4 1.4 3.6 27.2 1.6 4.2 21.5 1.7 4.8 17.3 1.9 5.4 13.6 2.2 5.9 125 120.7 1.0 1.6 84.7 1.1 2.0 61.8 1.2 2.6 46.4 1.3 3.1 35.9 1.4 3.6 28.3 1.6 4.2 22.4 1.7 4.8 18.1 1.9 5.4 14.3 2.2 5.9 130 125.5 1.0 1.6 88.1 1.1 2.0 64.3 1.2 2.6 48.3 1.3 3.1 37.3 1.4 3.7 29.5 1.6 4.2 23.3 1.7 4.8 18.9 1.9 5.4 14.9 2.2 5.9 135 130.3 1.0 1.6 91.5 1.1 2.0 66.7 1.2 2.6 50.2 1.3 3.1 38.7 1.4 3.7 30.6 1.6 4.2 24.2 1.7 4.8 19.6 1.9 5.4 15.6 2.2 5.9 140 135.2 1.0 1.6 94.9 1.1 2.0 69.2 1.2 2.6 52.0 1.3 3.1 40.2 1.4 3.7 31.7 1.6 4.2 25.1 1.7 4.8 20.4 1.9 5.4 16.2 2.2 5.9 145 140.0 1.0 1.6 98.3 1.1 2.0 71.7 1.2 2.6 53.9 1.3 3.1 41.6 1.4 3.7 32.9 1.6 4.2 26.1 1.7 4.8 21.2 1.9 5.4 16.9 2.2 5.9 150 144.8 1.0 1.6 101.7 1.1 2.0 74.1 1.2 2.6 55.7 1.3 3.1 43.0 1.4 3.7 34.0 1.6 4.2 27.0 1.7 4.8 21.9 1.9 5.4 17.5 2.2 5.9 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-262 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 1.50 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 4.9 1.0 1.5 10 10.5 0.9 1.5 7.1 1.1 2.0 4.6 1.3 2.5 15 16.0 0.9 1.5 10.9 1.0 2.0 7.8 1.1 2.5 5.3 1.4 3.1 20 21.3 0.9 1.5 14.7 1.0 2.0 10.6 1.1 2.5 7.7 1.3 3.1 5.1 1.6 3.6 25 26.6 0.9 1.5 18.6 1.0 2.0 13.4 1.1 2.5 9.9 1.2 3.1 7.3 1.4 3.6 30 31.9 0.9 1.5 22.3 1.0 2.0 16.2 1.1 2.5 12.0 1.2 3.1 9.0 1.4 3.6 6.6 1.6 4.2 35 37.3 0.9 1.5 26.0 1.0 2.0 19.1 1.1 2.5 14.1 1.2 3.1 10.7 1.4 3.6 8.1 1.5 4.2 40 42.6 0.9 1.5 29.7 1.0 2.0 21.8 1.1 2.5 16.2 1.2 3.1 12.4 1.3 3.6 9.5 1.5 4.2 6.9 1.8 4.7 45 47.9 0.9 1.5 33.4 1.0 2.0 24.5 1.1 2.5 18.3 1.2 3.1 14.0 1.3 3.6 10.8 1.5 4.2 8.3 1.7 4.7 50 53.2 0.9 1.5 37.1 1.0 2.0 27.3 1.1 2.5 20.6 1.2 3.0 15.7 1.3 3.6 12.1 1.5 4.2 9.4 1.7 4.8 55 58.5 0.9 1.5 40.8 1.0 2.0 30.0 1.1 2.5 22.7 1.2 3.0 17.3 1.3 3.6 13.4 1.5 4.2 10.5 1.6 4.8 8.1 1.9 5.3 60 63.8 0.9 1.5 44.5 1.0 2.0 32.7 1.1 2.5 24.7 1.2 3.0 18.9 1.3 3.6 14.7 1.4 4.2 11.6 1.6 4.8 9.1 1.9 5.3 65 69.2 0.9 1.5 48.2 1.0 2.0 35.4 1.1 2.5 26.8 1.2 3.1 20.8 1.3 3.6 16.0 1.4 4.2 12.7 1.6 4.8 10.0 1.8 5.3 70 74.5 0.9 1.5 51.9 1.0 2.0 38.2 1.1 2.5 28.8 1.2 3.1 22.4 1.3 3.6 17.3 1.4 4.2 13.7 1.6 4.8 10.9 1.8 5.3 8.2 2.2 5.8 75 79.8 0.9 1.5 55.6 1.0 2.0 40.9 1.1 2.5 30.9 1.2 3.1 23.9 1.3 3.6 18.6 1.4 4.2 14.8 1.6 4.8 11.8 1.8 5.3 9.3 2.1 5.8 80 85.1 0.9 1.5 59.4 1.0 2.0 43.6 1.1 2.5 32.9 1.2 3.1 25.5 1.3 3.6 19.9 1.4 4.2 15.8 1.6 4.8 12.7 1.8 5.3 10.1 2.0 5.9 85 90.4 0.9 1.5 63.1 1.0 2.0 46.3 1.1 2.5 35.0 1.2 3.1 27.1 1.3 3.6 21.2 1.4 4.2 16.9 1.6 4.8 13.6 1.8 5.3 10.9 2.0 5.9 90 95.8 0.9 1.5 66.8 1.0 2.0 49.0 1.1 2.5 37.1 1.2 3.1 28.7 1.3 3.6 22.8 1.4 4.1 17.9 1.6 4.8 14.5 1.8 5.3 11.6 2.0 5.9 95 101.1 0.9 1.5 70.5 1.0 2.0 51.8 1.1 2.5 39.1 1.2 3.1 30.3 1.3 3.6 24.0 1.4 4.2 18.9 1.6 4.8 15.3 1.7 5.3 12.4 2.0 5.9 100 106.4 0.9 1.5 74.2 1.0 2.0 54.5 1.1 2.5 41.2 1.2 3.1 31.9 1.3 3.6 25.3 1.4 4.2 20.0 1.6 4.8 16.2 1.7 5.3 13 1 1.9 5.9 105 111.7 0.9 1.5 77.9 1.0 2.0 57.2 1.1 2.5 43.2 1.2 3.1 33.5 1.3 3.6 26.5 1.4 4.2 21.0 1.6 4.8 17.0 1.7 5.3 13.9 1.9 5.9 110 117.0 0.9 1.5 81.6 1.0 2.0 59.9 1.1 2.5 45.3 1.2 3.1 35.1 1.3 3.6 27.8 1.4 4.2 22.0 1.6 4.8 17.9 1.7 5.3 14.6 1.9 5.9 115 122.4 0.9 1.5 85.3 1.0 2.0 62.6 1.1 2.5 47.3 1.2 3.1 36.7 1.3 3.6 29.1 1.4 4.2 23.1 1.6 4.8 18.8 1.7 5.3 15.3 1.9 5.9 120 127.7 0.9 1.5 89.0 1.0 2.0 65.4 1.1 2.5 49.4 1.2 3.1 38.3 1.3 3.6 30.3 1.4 4.2 24.1 1.6 478 19.6 1.7 5.3 16.1 1.9 5.9 125 133.0 0.9 1.5 92.7 1.0 2.0 68.1 1.1 2.5 51.4 1.2 3.1 39.9 1.3 3.6 31.6 1.4 4.2 25.4 1.6 4.8 20.5 1.7 5.3 16.8 1.9 5.9 130 138.3 0.9 1.5 96.4 1.0 2.0 70.8 1.1 2.5 53.5 1.2 3.1 41.4 1.3 3.6 32.8 1.4 4.2 26.4 1.6 4.8 21.3 1.7 5.3 17.5 1.9 5.9 135 143.6 0.9 1.5 100.1 1.0 2.0 73.5 1.1 2.5 55.6 1.2 3.1 43.0 1.3 3.6 34.1 1.4 4.2 27.4 1.6 4.8 22.2 1.7 5.3 18.2 1.9 5.9 140 149.0 0.9 1.5 103.9 1.0 2.0 76.3 1.1 2.5 57.6 1.2 3.1 44.6 1.3 3.6 35.3 1.4 4.2 28.5 1.6 4.8 23.0 1.7 5.3 18.9 1.9 5.9 145 154.3 0.9 1.5 107.6 1.0 2.0 79.0 1.1 2.5 59.7 1.2 3.1 46.2 1.3 3.6 36.6 1.4 4.2 29.5 1.6 4.8 23.8 1.7 5.3 19.7 1.9 5.9 150 159.6 0.9 1.5 111.3 1.0 2.0 81.7 1.1 2.5 61.7 1.2 3.1 47.8 1.3 3.6 37.9 1.4 4.2 30.5 1.6 4.8 24.7 1.7 5.3 20.4 1.9 5.9 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-263 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 1.75 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 5.4 0.9 1.5 10 11.4 0.9 1.5 7.7 1.0 2.0 5.4 1.1 2.5 15 17.3 0.9 1.5 11.8 1.0 2.0 8.6 1.1 2.5 6.2 1.2 3.0 20 23.1 0.9 1.5 16.0 0.9 2.0 11.6 1.0 2.5 8.6 1.2 3.0 6.3 1.3 3.6 25 28.8 0.9 1.5 20.0 0.9 2.0 14.6 1.0 2.5 10.9 1.1 3.0 8.2 1.3 3.6 5.9 1.5 4.1 30 34.6 0.9 1.5 24.0 0.9 2.0 17.8 1.0 2.5 13.2 1.1 3.0 10.1 1.2 3.6 7.6 1.4 4.2 35 40.3 0.9 1.5 28.0 0.9 2.0 20.7 1.0 2.5 15.5 1.1 3.0 11.9 1.2 3.6 9.1 1.4 4.2 6.9 1.6 4.7 40 46.1 0.9 1.5 32.0 0.9 2.0 23.7 1.0 2.5 18.0 1.1 3.0 13.7 1.2 3.6 10.6 1.4 4.2 8.2 1.6 4.7 45 51.9 0.9 1.5 36.0 0.9 2.0 26.6 1.0 2.5 20.2 1.1 3.0 15.4 1.2 3.6 12.0 1.3 4.2 9.4 1.5 4.7 7.0 1.8 5.3 50 57.6 0.9 1.5 40.0 0.9 2.0 29.6 1.0 2.5 22.4 1.1 3.0 17.2 1.2 3.6 13.5 1.3 4.1 10.6 1.5 4.7 8.3 1.7 5.3 55 63.4 0.9 1.5 44.0 0.9 2.0 32.5 1.0 2.5 24.7 1.1 3.0 19.2 1.2 3.6 14.9 1.3 4.1 11.8 1.5 4.7 9.3 1.7 5.3 6.7 2.1 5.8 60 69.1 0.9 1.5 48.0 0.9 2.0 35.5 1.0 2.5 26.9 1.1 3.0 20.9 1.2 3.6 16.3 1.3 4.1 12.9 1.5 4.7 10.3 1.6 5.3 8.1 1.9 5.8 65 74.9 0.9 1.5 52.0 0.9 2.0 38.4 1.0 2.5 29.2 1.1 3.0 22.7 1.2 3.6 17.7 1.3 4.1 14.1 1.5 4.7 11.3 1.6 5.3 9.0 1.9 5.8 70 80.7 0.9 1.5 56.0 0.9 2.0 41.4 1.0 2.5 31.4 1.1 3.0 24.4 1.2 3.6 19.1 1.3 4.1 15.2 1.5 4.7 12.3 1.6 5.3 9.8 1.8 5.8 75 86.4 0.9 1.5 60.0 0.9 2.0 44.3 1.0 2.5 33.6 1.1 3.0 26.1 1.2 3.6 20.5 1.3 4.1 16.4 1.4 4.7 13.2 1.6 5.3 10.7 1.8 5.8 80 92.2 0.9 1.5 63.9 0.9 2.0 47.3 1.0 2.5 35.9 1.1 3.0 27.9 1.2 3.6 22.2 1.3 4.1 17.5 1.4 4.7 14.2 1.6 5.3 11.5 1.8 5.8 85 97.9 0.9 1.5 67.9 0.9 2.0 50.2 1.0 2.5 38.1 1.1 3.0 29.6 1.2 3.6 23.5 1.3 4.1 18.6 1.4 4.7 15.1 1.6 5.3 12.3 1.8 5.8 90 103.7 0.9 1.5 71.9 0.9 2.0 53.2 1.0 2.5 40.3 1.1 3.0 31.4 1.2 3.6 24.9 1.3 4.1 19.8 1.4 4.7 16.1 1.6 5.3 13.1 1.8 5.8 95 109.5 0.9 1.5 75.9 0.9 2.0 56.1 1.0 2.5 42.6 1.1 3.0 33.1 1.2 3.6 26.3 1.3 4.1 20.9 1.4 4.7 17.0 1.6 5.3 13.9 1.7 5.8 100 115.2 0.9 1.5 79.9 0.9 2.0 59.1 1.0 2.5 44.8 1.1 3.0 34.8 1.2 3.6 27.7 1.3 4.1 22.0 1.4 4.7 17.9 1.6 5.3 14.7 1.7 5.8 105 121.0 0.9 1.5 83.9 0.9 2.0 62.0 1.0 2.5 47.1 1.1 3.0 36.6 1.2 3.6 29.0 1.3 4.1 23.4 1.4 4.7 18.9 1.6 5.3 15.5 1.7 5.8 110 126.8 0.9 1.5 87.9 0.9 2.0 65.0 1.0 2.5 49.3 1.1 3.0 38.3 1.2 3.6 30.4 1.3 4.1 24.5 1.4 4.7 19.8 1.6 5.3 16.3 1.7 5.8 115 132.5 0.9 1.5 91.9 0.9 2.0 67.9 1.0 2.5 51.5 1.1 3.0 40.1 1.2 3.6 31.8 1.3 4.1 25.6 1.4 4.7 20.7 1.6 5.3 17.1 1.7 5.9 120 138.3 0.9 1.5 95.9 0.9 2.0 70.9 1.0 2.5 53.8 1.1 3.0 41.8 1.2 3.6 33.2 1.3 4.1 26.8 1.4 4.7 21.7 1.6 5.3 17.9 1.7 5.9 125 144.0 0.9 1.5 99.9 0.9 2.0 73.8 1.0 2.5 56.0 1.1 3.0 43.5 1.2 3.6 34.6 1.3 4.1 27.9 1.4 4.7 22.6 1.6 5.3 18.7 1.7 5.9 130 149.8 0.9 1.5 103.9 0.9 2.0 76.8 1.0 2.5 58.3 1.1 3.0 45.3 1.2 3.6 35.9 1.3 4.1 29.0 1.4 4.7 23.5 1.6 5.3 19.4 1.7 5.9 135 155.6 0.9 1.5 107.9 0.9 2.0 79.7 1.0 2.5 60.5 1.1 3.0 47.0 1.2 3.6 37.3 1.3 4.1 30.1 1.4 4.7 24.5 1.6 5.3 20.2 1.7 5.9 140 161.3 0.9 1.5 111.9 0.9 2.0 82.7 1.0 2.5 62.7 1.1 3.0 48.8 1.2 3.6 38.7 1.3 4.1 31.2 1.4 4.7 25.7 1.6 5.3 21.0 1.7 5.9 145 167.1 0.9 1.5 115.9 0.9 2.0 85.6 1.0 2.5 65.0 1.1 3.0 50.5 1.2 3.6 40.1 1.3 4.1 32.3 1.4 4.7 26.6 1.6 5.3 21.8 1.7 5.9 150 172.8 0.9 1.5 119.9 0.9 2.0 88.6 1.0 2.5 67.2 1.1 3.0 52.2 1.2 3.6 41.5 1.3 4.1 33.4 1.4 4.7 27.5 1.6 5.3 22.6 1.7 5.9 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-264 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 2.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 5.9 0.9 1.5 10 12.4 0.8 1.5 8.1 0.9 2.0 5.9 1.0 2.5 15 18.5 0.8 1.5 12.3 0.9 2.0 9.3 1.0 2.5 6.8 1.1 3.0 4.7 1.4 3.5 20 24.7 0.8 1.5 16.7 0.9 2.0 12.5 1.0 2.5 9.4 1.1 3.0 7.0 1.2 3.6 4.7 1.5 4.1 25 30.8 0.8 1.5 20.8 0.9 2.0 15.9 1.0 2.4 11.8 1.1 3.0 9.0 1.2 3.5 6.8 1.3 4.1 30 37.0 0.8 1.5 25.0 0.9 2.0 19.0 1.0 2.5 14.3 1.1 3.0 11.0 1.2 3.5 8.5 1.3 4.1 6.4 1.5 4.7 35 43.2 0.8 1.5 29.1 0.9 2.0 22.2 1.0 2.5 16.9 1.0 3.0 12.9 1.1 3.5 10.1 1.3 4.1 7.8 1.4 4.7 40 49.3 0.8 1.5 33.3 0.9 2.0 25.3 1.0 2.5 19.3 1.0 3.0 14.8 1.1 3.5 11.6 1.3 4.1 9.1 1.4 4.7 7.1 1.6 5.2 45 55.5 0.8 1.5 37.4 0.9 2.0 28.5 1.0 2.5 21.7 1.0 3.0 16.7 1.1 3.5 13.1 1.3 4.1 10.4 1.4 4.7 8.2 1.6 5.2 50 61.7 0.8 1.5 41.6 0.9 2.0 31.7 1.0 2.5 24.1 1.0 3.0 18.8 1.1 3.5 14.7 1.2 4.1 11.7 1.4 4.7 9.3 1.5 5.3 7.1 1.8 5.8 55 67.8 0.8 1.5 45.7 0.9 2.0 34.8 1.0 2.5 26.5 1.0 3.0 20.7 1.1 3.5 16.2 1.2 4.1 12.9 1.4 4.7 10.4 1.5 5.3 8.2 1.7 5.8 60 74.0 0.8 1.5 49.9 0.9 2.0 38.0 1.0 2.5 28.9 1.0 3.0 22.6 1.1 3.5 17.7 1.2 4.1 14.1 1.4 4.7 11.4 1.5 5.3 9.2 1.7 5.8 65 80.2 0.8 1.5 54.0 0.9 2.0 41.1 1.0 2.5 31.4 1.0 3.0 24.5 1.1 3.5 19.5 1.2 4.1 15.4 1.3 4.7 12.4 1.5 5.3 10.1 1.7 5.8 70 86.3 0.8 1.5 58.2 0.9 2.0 44.3 1.0 2.5 33.8 1.0 3.0 26.3 1.1 3.5 21.0 1.2 4.1 16.6 1.3 4.7 13.5 1.5 5.3 11.0 1.6 5.8 75 92.5 0.8 1.5 62.3 0.9 2.0 47.5 1.0 2.5 36.2 1.0 3.0 28.2 1.1 3.5 22.4 1.2 4.1 17.8 1.3 4.7 14.5 1.5 5.3 11.8 1.6 5.8 80 98.7 0.8 1.5 66.5 0.9 2.0 50.6 1.0 2.5 38.6 1.0 3.0 30.1 1.1 3.5 23.9 1.2 4.1 19.0 1.3 4.7 15.5 1.5 5.3 12.7 1.6 5.8 85 104.8 0.8 1.5 70.6 0.9 2.0 53.8 1.0 2.5 41.0 1.0 3.0 32.0 1.1 3.5 25.4 1.2 4.1 20.3 1.3 4.7 16.5 1.5 5.3 13.6 1.6 5.8 90 111.0 0.8 1.5 74.8 0.9 2.0 57.0 1.0 2.5 43.4 1.0 3.0 33.8 1.1 3.5 26.9 1.2 4.1 21.8 1.3 4.6 17.5 1.5 5.3 14.4 1.6 5.8 95 117.2 0.8 1.5 78.9 0.9 2.0 60.1 1.0 2.5 45.8 1.0 3.0 35.7 1.1 3.5 28.4 1.2 4.1 23.0 1.3 4.6 18.6 1.5 5.3 15.3 1.6 5.8 100 123.3 0.8 1.5 83.1 0.9 2.0 63.3 1.0 2.5 48.2 1.0 3.0 37.6 1.1 3.5 29.9 1.2 4.1 24.2 1.3 4.6 19.6 1.5 5.3 16.2 1.6 5.8 105 129.5 0.8 1.5 87.3 0.9 2.0 66.4 1.0 2.5 50.6 1.0 3.0 39.5 1.1 3.5 31.4 1.2 4.1 25.4 1.3 4.6 20.6 1.5 5.3 17.0 1.6 5.8 110 135.7 0.8 1.5 91.4 0.9 2.0 69.6 1.0 2.5 53.0 1.0 3.0 41.3 1.1 3.5 32.9 1.2 4.1 26.6 1.3 4.7 21.6 1.4 5.3 17.9 1.6 5.8 115 141.8 0.8 1.5 95.6 0.9 2.0 72.8 1.0 2.5 55.4 1.0 3.0 43.2 1.1 3.5 34.4 1.2 4.1 27.9 1.3 4.7 22.6 1.4 5.3 18.7 1.6 5.8 120 148.0 0.8 1.5 99.7 0.9 2.0 75.9 1.0 2.5 57.9 1.0 3.0 45.1 1.1 3.5 35.9 1.2 4.1 29.1 1.3 4.7 23.9 1.4 5.2 19.5 1.6 5.8 125 154.1 0.8 1.5 103.9 0.9 2.0 79.1 1.0 2.5 60.3 1.0 3.0 47.0 1.1 3.5 37.4 1.2 4.1 30.3 1.3 4.7 24.8 1.4 5.2 20.4 1.6 5.8 130 160.3 0.8 1.5 108.0 0.9 2.0 82.3 1.0 2.5 62.7 1.0 3.0 48.8 1.1 3.5 38.9 1.2 4.1 31.5 1.3 4.7 25.8 1.4 5.3 21.2 1.6 5.8 135 166.5 0.8 1.5 112.2 0.9 2.0 85.4 1.0 2.5 65.1 1.0 3.0 50.7 1.1 3.5 40.3 1.2 4.1 32.7 1.3 4.7 26.8 1.4 5.3 22.1 1.6 5.8 140 172.6 0.8 1.5 116.3 0.9 2.0 88.6 1.0 2.5 67.5 1.0 3.0 52.6 1.1 3.5 41.8 1.2 4.1 33.9 1.3 4.7 27.8 1.4 5.3 22.9 1.6 5.8 145 178.8 0.8 1.5 120.5 0.9 2.0 91.8 1.0 2.5 69.9 1.0 3.0 54.5 1.1 3.5 43.3 1.2 4.1 35.1 1.3 4.7 28.8 1.4 5.3 23.7 1.6 5.8 150 185.0 0.8 1.5 124.6 0.9 2.0 94.9 1.0 2.5 72.3 1.0 3.0 56.4 1.1 3.5 44.8 1.2 4.1 36.3 1.3 4.7 29.8 1.4 5.3 24.6 1.6 5.8 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-265 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 3.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 7.4 0.7 1.4 4.9 0.8 1.9 3.2 1.0 2.3 10 15.1 0.7 1.4 10.2 0.8 1.9 7.6 0.8 2.4 5.7 0.9 2.9 4.0 1.1 3.4 15 22.6 0.7 1.4 15.6 0.8 1.9 11.5 0.8 2.4 8.8 0.9 2.9 6.7 1.0 3.4 5.1 1.1 4.0 20 30.1 0.7 1.4 20.7 0.8 1.9 15.5 0.8 2.4 11.8 0.9 2.9 9.2 0.9 3.4 7.2 1.0 4.0 5.5 1.2 4.6 25 37.6 0.7 1.4 25.9 0.8 1.9 19.4 0.8 2.4 15.0 0.9 2.9 11.6 0.9 3.4 9.2 1.0 4.0 7.2 1.1 4.6 5.6 1.3 5.1 30 45.1 0.7 1.4 31.1 0.8 1.9 23.3 0.8 2.4 18.0 0.9 2.9 14.0 0.9 3.4 11.1 1.0 4.0 8.9 1.1 4.6 7.1 1.2 5.2 5.3 1.5 5.7 35 52.7 0.7 1.4 36.2 0.8 1.9 27.1 0.8 2.4 21.0 0.9 2.9 16.5 0.9 3.4 13.0 1.0 4.0 10.5 1.1 4.6 8.4 1.2 5.2 6.7 1.4 5.7 40 60.2 0.7 1.4 41.4 0.8 1.9 31.0 0.8 2.4 24.0 0.9 2.9 18.9 0.9 3.4 14.9 1.0 4.0 12.0 1.1 4.6 9.8 1.2 5.2 7.9 1.3 5.7 45 67.7 0.7 1.4 46.6 0.8 1.9 34.9 0.8 2.4 27.0 0.9 2.9 21.2 0.9 3.4 17.0 1.0 4.0 13.6 1.1 4.6 11.1 1.2 5.2 9.1 1.3 5.7 50 75.2 0.7 1.4 51.8 0.8 1.9 38.8 0.8 2.4 29.9 0.9 2.9 23.6 0.9 3.4 18.9 1.0 4.0 15.2 1.1 4.6 12.4 1.2 5.2 10.2 1.3 5.7 55 82.8 0.7 1.4 56.9 0.8 1.9 42.6 0.8 2.4 32.9 0.9 2.9 25.9 0.9 3.4 20.8 1.0 4.0 16.7 1.1 4.6 13.7 1.2 5.2 11.3 1.3 5.7 60 90.3 0.7 1.4 62.1 0.8 1.9 46.5 0.8 2.4 35.9 0.9 2.9 28.3 0.9 3.4 22.7 1.0 4.0 18.5 1.1 4.5 14.9 1.2 5.2 12.4 1.3 5.7 65 97.8 0.7 1.4 67.3 0.8 1.9 50.4 0.8 2.4 38.9 0.9 2.9 30.6 0.9 3.4 24.6 1.0 4.0 20.0 1.1 4.5 16.2 1.2 5.2 13.5 1.3 5.7 70 105.3 0.7 1.4 72.4 0.8 1.9 54.3 0.8 2.4 41.9 0.9 2.9 33.0 0.9 3.4 26.4 1.0 4.0 21.5 1.1 4.5 17.5 1.2 5.2 14.5 1.3 5.7 75 112.8 0.7 1.4 77.6 0.8 1.9 58.1 0.8 2.4 44.9 0.9 2.9 35.3 0.9 3.4 28.3 1.0 4.0 23.1 1.1 4.5 19.1 1.2 5.1 15.6 1.3 5.7 80 120.4 0.7 1.4 82.8 0.8 1.9 62.0 0.8 2.4 47.9 0.9 2.9 37.7 0.9 3.4 30.2 1.0 4.0 24.6 1.1 4.5 20.3 1.2 5.1 16.7 1.3 5.7 85 127.9 0.7 1.4 88.0 0.8 1.9 65.9 0.8 2.4 50.9 0.9 2.9 40.1 0.9 3.4 32.1 1.0 4.0 26.1 1.1 4.5 21.6 1.2 5.1 17.8 1.2 5.7 90 135.4 0.7 1.4 93.1 0.8 1.9 69.8 0.8 2.4 53.9 0.9 2.9 42.4 0.9 3.4 34.0 1.0 4.0 27.7 1.1 4.5 22.9 1.2 5.1 18.9 1.2 5.7 95 142.9 0.7 1.4 98.3 0.8 1.9 73.6 0.8 2.4 56.9 0.9 2.9 44.8 0.9 3.4 35.9 1.0 4.0 29.2 1.1 4.5 24.1 1.2 5.1 20.2 1.2 5.7 100 150.5 0.7 1.4 103.5 0.8 1.9 77.5 0.8 2.4 59.9 0.9 2.9 47.1 0.9 3.4 37.8 1.0 4.0 30.7 1.1 4.5 25.4 1.2 5.1 21.2 1.2 5.7 105 158.0 0.7 1.4 108.7 0.8 1.9 81.4 0.8 2.4 62.8 0.9 2.9 49.5 0.9 3.4 39.6 1.0 4.0 32.3 1.1 4.5 26.7 1.2 5.1 22.3 1.2 5.7 110 165.5 0.7 1.4 113.8 0.8 1.9 85.3 0.8 2.4 65.8 0.9 2.9 51.8 0.9 3.4 41.5 1.0 4.0 33.8 1.1 4.6 27.9 1.2 5.1 23.3 1.2 5.7 115 173.0 0.7 1.4 119.0 0.8 1.9 89.1 0.8 2.4 68.8 0.9 2.9 54.2 0.9 3.4 43.4 1.0 4.0 35.4 1.1 4.6 29.2 1.2 5.1 24.4 1.2 5.7 120 180.5 0.7 1.4 124.2 0.8 1.9 93.0 0.8 2.4 71.8 0.9 2.9 56.5 0.9 3.4 45.3 1.0 4.0 36.9 1.1 4.6 30.5 1.2 5.1 25.5 1.2 5.7 125 188.1 0.7 1.4 129.4 0.8 1.9 96.9 0.8 2.4 74.8 0.9 2.9 58.9 0.9 3.4 47.2 1.0 4.0 38.4 1.1 4.6 31.7 1.2 5.1 26.5 1.2 5.7 130 195.6 0.7 1.4 134.5 0.8 1.9 100.8 0.8 2.4 77.8 0.9 2.9 61.2 0.9 3.4 49.1 1.0 4.0 40.0 1.1 4.6 33.0 1.2 5.1 27.6 1.2 5.7 135 203.1 0.7 1.4 139.7 0.8 1.9 104.6 0.8 2.4 80.8 0.9 2.9 63.6 0.9 3.4 51.0 1.0 4.0 41.5 1.1 4.6 34.3 1.2 5.1 28.6 1.2 5.7 140 210.6 0.7 1.4 144.9 0.8 1.9 108.5 0.8 2.4 83.8 0.9 2.9 66.0 0.9 3.4 52.8 1.0 4.0 43.0 1.1 4.6 35.6 1.2 5.1 29.7 1.2 5.7 145 218.2 0.7 1.4 150.1 0.8 1.9 112.4 0.8 2.4 86.8 0.9 2.9 68.3 0.9 3.4 54.7 1.0 4.0 44.6 1.1 4.6 36.8 1.2 5.1 30.7 1.2 5.7 150 225.7 0.7 1.4 155.2 0.8 1.9 116.3 0.8 2.4 89.8 0.9 2.9 70.7 0.9 3.4 56.6 1.0 4.0 46.1 1.1 4.6 38.1 1.2 5.1 31.8 1.2 5.7 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-266 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 4.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 8.5 0.6 1.4 5.9 0.7 1.8 4.1 0.8 2.3 10 17.2 0.6 1.4 12.1 0.7 1.8 8.8 0.7 2.3 6.7 0.8 2.8 5.2 0.9 3.3 3.8 1.0 3.9 15 25.8 0.6 1.4 18.1 0.7 1.8 13.4 0.7 2.3 10.3 0.8 2.8 8.1 0.8 3.4 6.4 0.9 3.9 4.9 1.0 4.5 20 34.4 0.6 1.4 24.2 0.7 1.8 17.8 0.7 2.3 13.9 0.8 2.8 10.9 0.8 3.4 8.7 0.9 3.9 6.9 1.0 4.5 5.5 1.1 5.0 25 43.0 0.6 1.4 30.2 0.7 1.9 22.3 0.7 2.3 17.4 0.8 2.8 13.8 0.8 3.3 10.9 0.9 3.9 8.8 1.0 4.5 7.1 1.0 5.1 5.7 1.2 5.6 30 51.6 0.6 1.4 36.3 0.7 1.9 26.7 0.7 2.3 20.8 0.8 2.8 16.5 0.8 3.3 13.2 0.9 3.9 10.7 0.9 4.5 8.7 1.0 5.1 7.1 1.1 5.6 35 60.2 0.6 1.4 42.3 0.7 1.9 31.1 0.7 2.3 24.3 0.8 2.8 19.3 0.8 3.4 15.6 0.9 3.9 12.5 0.9 4.5 10.3 1.0 5.0 8.4 1.1 5.6 40 68.8 0.6 1.4 48.3 0.7 1.9 35.6 0.7 2.3 27.8 0.8 2.8 22.0 0.8 3.4 17.8 0.9 3.9 14.4 0.9 4.5 11.8 1.0 5.0 9.8 1.1 5.7 45 77.4 0.6 1.4 54.4 0.7 1.9 40.0 0.7 2.4 31.2 0.8 2.8 24.8 0.8 3.4 20.0 0.9 3.9 16.4 0.9 4.4 13.3 1.0 5.0 11.1 1.1 5.7 50 86.0 0.6 1.4 60.4 0.7 1.9 44.5 0.7 2.4 34.7 0.8 2.8 27.5 0.8 3.4 22.2 0.9 3.9 18.2 0.9 4.4 14.9 1.0 5.0 12.3 1.1 5.7 55 94.6 0.6 1.4 66.5 0.7 1.9 48.9 0.7 2.4 38.2 0.8 2.8 30.3 0.8 3.4 24.4 0.9 3.9 20.0 0.9 4.4 16.6 1.0 5.0 13.6 1.1 5.7 60 103.2 0.6 1.4 72.5 0.7 1.9 53.4 0.7 2.4 41.7 0.8 2.8 33.0 0.8 3.4 26.6 0.9 3.9 21.8 0.9 4.5 18.1 1.0 5.0 14.9 1.1 5.7 65 111.8 0.6 1.4 78.5 0.7 1.9 57.8 0.7 2.4 45.1 0.8 2.8 35.8 0.8 3.4 28.9 0.9 3.9 23.6 0.9 4.5 19.6 1.0 5.0 16.2 1.1 5.7 70 120.4 0.6 1.4 84.6 0.7 1.9 62.3 0.7 2.4 48.6 0.8 2.8 38.6 0.8 3.4 31.1 0.9 3.9 25.4 0.9 4.5 21.1 1.0 5.0 17.7 1.1 5.6 75 129.0 0.6 1.4 90.6 0.7 1.9 66.7 0.7 2.4 52.1 0.8 2.8 41.3 0.8 3.4 33.3 0.9 3.9 27.2 0.9 4.5 22.6 1.0 5.0 19.0 1.1 5.6 80 137.6 0.6 1.4 96.7 0.7 1.9 71.2 0.7 2.4 55.5 0.8 2.8 44.1 0.8 3.4 35.5 0.9 3.9 29.1 0.9 4.5 24.1 1.0 5.0 20.2 1.1 5.6 85 146.2 0.6 1.4 102.7 0.7 1.9 75.6 0.7 2.4 59.0 0.8 2.8 46.8 0.8 3.4 37.7 0.9 3.9 30.9 0.9 4.5 25.6 1.0 5.0 21.5 1.1 5.6 90 154.8 0.6 1.4 108.7 0.7 1.9 80.0 0.7 2.4 62.5 0.8 2.8 49.6 0.8 3.4 39.9 0.9 3.9 32.7 0.9 4.5 27.1 1.0 5.0 22.8 1.1 5.6 95 163.4 0.6 1.4 114.8 0.7 1.9 84.5 0.7 2.4 65.9 0.8 2.8 52.3 0.8 3.4 42.2 0.9 3.9 34.5 0.9 4.5 28.6 1.0 5.0 24.0 1.1 5.6 100 172.0 0.6 1.4 120.8 0.7 1.9 88.9 0.7 2.4 69.4 0.8 2.8 55.1 0.8 3.4 44.4 0.9 3.9 36.3 0.9 4.5 30.1 1.0 5.0 25.3 1.1 5.6 105 180.6 0.6 1.4 126.9 0.7 1.9 93.4 0.7 2.4 72.9 0.8 2.8 57.8 0.8 3.4 46.6 0.9 3.9 38.1 0.9 4.5 31.6 1.0 5.0 26.5 1.1 5.6 110 189.2 0.6 1.4 132.9 0.7 1.9 97.8 0.7 2.4 76.3 0.8 2.8 60.6 0.8 3.4 48.8 0.9 3.9 39.9 0.9 4.5 33.1 1.0 5.0 27.8 1.1 5.6 115 197.8 0.6 1.4 138.9 0.7 1.9 102.3 0.7 2.4 79.8 0.8 2.8 63.3 0.8 3.4 51.0 0.9 3.9 41.7 0.9 4.5 34.6 1.0 5.0 29.0 1.1 5.6 120 206.4 0.6 1.4 145.0 0.7 1.9 106.7 0.7 2.4 83.3 0.8 2.8 66.1 0.8 3.4 53.3 0.9 3.9 43.6 0.9 4.5 36.1 1.0 5.0 30.2 1.1 5.7 125 215.0 0.6 1.4 151.0 0.7 1.9 111.2 0.7 2.4 86.8 0.8 2.8 68.8 0.8 3.4 55.5 0.9 3.9 45.4 0.9 4.5 37.6 1.0 5.0 31.5 1.1 5.7 130 223.7 0.6 1.4 157.1 0.7 1.9 115.6 0.7 2.4 90.2 0.8 2.8 71.6 0.8 3.4 57.7 0.9 3.9 47.2 0.9 4.5 39.1 1.0 5.0 32.7 1.1 5.7 135 232.3 0.6 1.4 163.1 0.7 1.9 120.1 0.7 2.4 93.7 0.8 2.8 74.3 0.8 3.4 59.9 0.9 3.9 49.0 0.9 4.5 40.6 1.0 5.0 34.0 1.1 5.7 140 240.9 0.6 1.4 169.1 0.7 1.9 124.5 0.7 2.4 97.2 0.8 2.8 77.1 0.8 3.4 62.1 0.9 3.9 50.8 0.9 4.5 42.1 1.0 5.0 35.2 1.1 5.7 145 249.5 0.6 1.4 175.2 0.7 1.9 129.0 0.7 2.4 100.6 0.8 2.8 79.8 0.8 3.4 64.3 0.9 3.9 52.6 0.9 4.5 43.6 1.0 5.0 36.5 1.1 5.7 150 258.1 0.6 1.4 181.2 0.7 1.9 133.4 0.7 2.4 104.1 0.8 2.8 82.6 0.8 3.4 66.6 0.9 3.9 54.4 0.9 4.5 45.1 1.0 5.0 37.8 1.1 5.7 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-267 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 5.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 9.5 0.6 1.4 6.7 0.6 1.8 4.7 0.7 2.3 3.5 0.8 2.8 10 19.0 0.6 1.4 13.7 0.6 1.8 9.7 0.7 2.3 7.6 0.7 2.8 6.0 0.8 3.3 4.7 0.8 3.8 3.4 1.0 4.4 15 28.5 0.6 1.4 20.5 0.6 1.8 14.8 0.7 2.3 11.7 0.7 2.8 9.2 0.7 3.3 7.3 0.8 3.8 5.9 0.9 4.4 4.7 1.0 5.0 20 38.0 0.6 1.4 27.3 0.6 1.8 19.7 0.7 2.3 15.5 0.7 2.8 12.4 0.7 3.3 9.9 0.8 3.8 8.0 0.9 4.4 6.5 0.9 4.9 5.3 1.0 5.5 25 47.5 0.6 1.4 34.1 0.6 1.8 24.6 0.7 2.3 19.4 0.7 2.8 15.5 0.7 3.3 12.6 0.8 3.8 10.1 0.8 4.4 8.3 0.9 5.0 6.8 1.0 5.6 30 57.0 0.6 1.4 40.9 0.6 1.8 29.5 0.7 2.3 23.3 0.7 2.8 18.6 0.7 3.3 15.1 0.8 3.8 12.2 0.8 4.4 10.1 0.9 5.0 8.3 1.0 5.6 35 66.5 0.6 1.4 47.7 0.6 1 8 34.4 07 2.3 27.2 0.7 2.8 21.7 0.7 3.3 17.6 0.8 3.8 14.5 0.8 4.4 11.8 09 5.0 9.8 1.0 5.6 40 76.0 0.6 1.4 54.6 0.6 1.8 39.4 0.7 2.3 31.0 0.7 2.8 24.8 0.7 3.3 20.1 0.8 3.8 16.5 0.8 4.4 13.6 0.9 5.0 11.3 1.0 5.5 45 85.5 0.6 1.4 61.4 0.6 1.8 44.3 0.7 2.3 34.9 0.7 2.8 27.9 0.7 3.3 22.6 0.8 3.8 18.6 0.8 4.4 15.5 0.9 4.9 12.8 1.0 5.5 50 95.0 0.6 1.4 68.2 0.6 1.8 49.2 0.7 2.3 38.8 0.7 2.8 31.0 0.7 3.3 25.1 0.8 3.8 20.6 0.8 4.4 17.2 0.9 4.9 14.3 1.0 5.5 55 104.6 0.6 1.4 75.0 0.6 1.8 54.1 0.7 2.3 42.7 0.7 2.8 34.1 0.7 3.3 27.6 0.8 3.8 22.7 0.8 4.4 18.9 0.9 4.9 15.9 0.9 5.5 60 114.1 0.6 1.4 81.8 0.6 1.8 59.0 0.7 2.3 46.6 0.7 2.8 37.2 0.7 3.3 30.1 0.8 3.8 24.7 0.8 4.4 20.6 0.9 4.9 17.3 0.9 5.5 65 123.6 0.6 1.4 88.6 0.6 1.8 63.9 0.7 2.3 50.4 0.7 2.8 40.3 0.7 3.3 32.6 0.8 3.8 26.8 0.8 4.4 22.3 0.9 4.9 18.8 0.9 5.5 70 133.1 0.6 1.4 95.5 0.6 1.8 68.9 0.7 2.3 54.3 0.7 2.8 43.4 0.7 3.3 35.1 0.8 3.8 28.9 0.8 4.4 24.0 0.9 4.9 20.2 0.9 5.5 75 142.6 0.6 1.4 102.3 0.6 1.8 73.8 0.7 2.3 58.2 0.7 2.8 46.5 0.7 3.3 37.7 0.8 3.8 30.9 0.8 4.4 25.7 0.9 4.9 21.6 0.9 5.5 80 152.1 0.6 1.4 109.1 0.6 1.8 78.7 0.7 2.3 62.1 0.7 2.8 49.6 0.7 3.3 40.2 0.8 3.8 33.0 0.8 4.4 27.4 0.9 4.9 23.1 0.9 5.5 85 161.6 0.6 1.4 115.9 0.6 1.8 83.6 0.7 2.3 65.9 0.7 2.8 52.7 0.7 3.3 42.7 0.8 3.8 35.0 0.8 4.4 29.1 0.9 5.0 24.5 0.9 5.5 90 171.1 0.6 1.4 122.7 0.6 1.8 88.5 0.7 2.3 69.8 0.7 2.8 55.8 0.7 3.3 45.2 0.8 3.8 37.1 0.8 4.4 30.9 0.9 5.0 26.0 0.9 5.5 95 180.6 0.6 1.4 129.6 0.6 1.8 93.4 0.7 2.3 73.7 0.7 2.8 58.9 0.7 3.3 47.7 0.8 3.8 39.2 0.8 4.4 32.6 0.9 5.0 27.4 0.9 5.5 100 190.1 0.6 1.4 136.4 0.6 1.8 98.4 0.7 2.3 77.6 0.7 2.8 62.0 0.7 3.3 50.2 0.8 3.8 41.2 0.8 4.4 34.3 0.9 5.0 28.8 0.9 5.5 105 199.6 0.6 1.4 143.2 0.6 1.8 103.3 0.7 2.3 81.5 0.7 2.8 65.1 0.7 3.3 52.7 0.8 3.8 43.3 0.8 4.4 36.0 0.9 5.0 30.3 0.9 5.5 110 209.1 0.6 1.4 150.0 0.6 1.8 108.2 0.7 2.3 85.3 0.7 2.8 68.2 0.7 3.3 55.2 0.8 3.8 45.3 0.8 4.4 37.7 0.9 5.0 31.7 0.9 5.5 115 218.6 0.6 1.4 156.8 0.6 1.8 113.1 0.7 2.3 89.2 0.7 2.8 71.3 0.7 3.3 57.7 0.8 3.8 47.4 0.8 4.4 39.4 0.9 5.0 33.2 0.9 5.5 120 228.1 0.6 1.4 163.6 0.6 1.8 118.0 0.7 2.3 93.1 0.7 2.8 74.3 0.7 3.3 60.2 0.8 3.8 49.5 0.8 4.4 41.1 0.9 5.0 34.6 0.9 5.5 125 237.6 0.6 1.4 170.5 0.6 1.8 123.0 0.7 2.3 97.0 0.7 2.8 77.4 0.7 3.3 62.7 0.8 3.8 51.5 0.8 4.4 42.8 0.9 5.0 36.0 0.9 5.5 130 247.1 0.6 1.4 177.3 0.6 1.8 127.9 0.7 2.3 100.8 0.7 2.8 80.5 0.7 3.3 65.2 0.8 3.8 53.6 0.8 4.4 44.6 0.9 5.0 37.5 0.9 5.5 135 256.6 0.6 1.4 184.1 0.6 1.8 132.8 0.7 2.3 104.7 0.7 2.8 83.6 0.7 3.3 67.8 0.8 3.8 55.6 0.8 4.4 46.3 0.9 5.0 38.9 0.9 5.5 140 266.1 0.6 1.4 190.9 0.6 1.8 137.7 0.7 2.3 108.6 0.7 2.8 86.7 0.7 3.3 70.3 0.8 3.8 57.7 0.8 4.4 48.0 0.9 5.0 40.4 0.9 5.5 145 275.6 0.6 1.4 197.7 0.6 1.8 142.6 0.7 2.3 112.5 0.7 2.8 89.8 0.7 3.3 72.8 0.8 3.8 59.8 0.8 4.4 49.7 0.9 5.0 41.8 0.9 5.5 150 285.1 0.6 1.4 204.6 0.6 1.8 147.5 0.7 2.3 116.4 0.7 2.8 92.9 0.7 3.3 75.3 0.8 3.8 61.8 0.8 4.4 51.4 0.9 5.0 43.2 0.9 5.5 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-268 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 6.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 10.6 0.5 1.3 7.3 0.6 1.8 5.3 0.6 2.3 4.0 0.7 2.8 2.9 0.8 3.2 10 21.1 0.5 1.3 14.7 0.6 1.8 10.9 0.6 2.3 8.4 0.7 2.8 6.6 0.7 3.2 5.3 0.8 3.8 4.2 0.8 4.3 15 31.6 0.5 1.3 22.1 0.6 1.8 16.3 0.6 2.3 12.7 0.6 2.7 10.1 0.7 3.3 8.2 0.7 3.8 6.6 0.8 4.3 5.4 0.9 4.9 4.3 1.0 5.5 20 42.1 0.5 1.3 29.5 0.6 1.8 21.7 0.6 2.3 17.0 0.6 2.7 13.6 0.7 3.2 11.1 0.7 3.7 9.0 0.8 4.3 7.4 0.8 4.9 6.1 0.9 5.5 25 52.7 0.5 1.3 36.8 0.6 1.8 27.1 0.6 2.3 21.2 0.6 2.8 17.0 0.7 3.2 13.9 0.7 3.8 11.3 0.8 4.3 9.3 0.8 4.9 7.8 0.9 5.5 30 63.2 0.5 1.3 44.2 0.6 1.8 32.5 0.6 2.3 25.4 0.6 2.8 20.4 0.7 3.2 16.6 0.7 3.8 13.7 0.8 4.3 11.3 0.8 4.9 9.4 0.9 5.5 35 73.7 0.5 1.3 51.6 0.6 1.8 38.0 0.6 2.3 29.7 0.6 2.8 23.8 0.7 3.2 19.4 0.7 3.8 16.0 0.8 4.3 13.4 0.8 4.9 11.1 0.9 5.5 40 84.2 0.5 1.3 58.9 0.6 1.8 43.4 0.6 2.3 33.9 0.6 2.8 27.2 0.7 3.3 22.2 0.7 3.8 18.3 0.8 4.3 15.3 0.8 4.9 12.7 0.9 5.5 45 94.8 0.5 1.3 66.3 0.6 1.8 48.8 0.6 2.3 38.2 0.6 2.8 30.7 0.7 3.3 24.9 0.7 3.8 20.6 0.8 4.3 17.2 0.8 4.9 14.5 0.9 5.4 50 105.3 0.5 1.3 73.6 0.6 1.8 54.2 0.6 2.3 42.4 0.6 2.8 34.1 0.7 3.3 27.7 0.7 3.8 22.8 0.8 4.3 19.1 0.8 4.9 16.1 0.9 5.4 55 115.8 0.5 1.3 81.0 0.6 1.8 59.7 0.6 2.3 46.6 0.6 2.8 37.5 0.7 3.3 30.5 0.7 3.8 25.1 0.8 4.3 21.0 0.8 4.9 17.7 0.9 5.4 60 126.4 0.5 1.3 88.4 0.6 1.8 65.1 0.6 2.3 50.9 0.6 2.8 40.9 0.7 3.3 33.3 0.7 3.8 27.4 0.8 4.3 22.9 0.8 4.9 19.3 0.9 5.4 65 136.9 0.5 1.3 95.7 0.6 1.8 70.5 0.6 2.3 55.1 0.6 2.8 44.3 0.7 3.3 36.0 0.7 3.8 29.7 0.8 4.3 24.8 0.8 4.9 20.9 0.9 5.4 70 147.4 0.5 1.3 103.1 0.6 1.8 75.9 0.6 2.3 59.3 0.6 2.8 47.7 0.7 3.3 38.8 0.7 3.8 32.0 0.8 4.3 26.7 0.8 4.9 22.5 0.9 5.4 75 158.0 0.5 1.3 110.5 0.6 1.8 81.3 0.6 2.3 63.6 0.6 2.8 51.1 0.7 3.3 41.6 0.7 3.8 34.3 0.8 4.3 28.6 0.8 4.9 24.1 0.9 5.4 80 168.5 0.5 1.3 117.8 0.6 1.8 86.8 0.6 2.3 67.8 0.6 2.8 54.5 0.7 3.3 44.3 0.7 3.8 36.5 0.8 4.3 30.5 0.8 4.9 25.7 0.9 5.5 85 179.0 0.5 1.3 125.2 0.6 1.8 92.2 0.6 2.3 72.0 0.6 2.8 57.9 0.7 3.3 47.1 0.7 3.8 38.8 0.8 4.3 32.4 0.8 4.9 27.3 0.9 5.5 90 189.6 0.5 1.3 132.6 0.6 1.8 97.6 0.6 2.3 76.3 0.6 2.8 61.3 0.7 3.3 49.9 0.7 3.8 41.1 0.8 4.3 34.3 0.8 4.9 28.9 0.9 5.5 95 200.1 0.5 1.3 139.9 0.6 1.8 103.0 0.6 2.3 80.5 0.6 2.8 64.7 0.7 3.3 52.6 0.7 3.8 43.4 0.8 4.3 36.2 0.8 4.9 30.5 0.9 5.5 100 210.6 0.5 1.3 147.3 0.6 1.8 108.5 0.6 2.3 84.8 0.6 2.8 68.1 0.7 3.3 55.4 0.7 3.8 45.7 0.8 4.3 38.1 0.8 4.9 32.1 0.9 5.5 105 221.1 0.5 1.3 154.6 0.6 1.8 113.9 0.6 2.3 89.0 0.6 2.8 71.5 0.7 3.3 58.2 0.7 3.8 47.9 0.8 4.3 40.0 0.8 4.9 33.7 0.9 5.5 110 231.7 0.5 1.3 162.0 0.6 1.8 119.3 0.6 2.3 93.2 0.6 2.8 74.9 0.7 3.3 60.9 0.7 3.8 50.2 0.8 4.3 41.9 0.8 4.9 35.3 0.9 5.5 115 242.2 0.5 1.3 169.4 0.6 1.8 124.7 0.6 2.3 97.5 0.6 2.8 78.3 0.7 3.3 63.7 0.7 3.8 52.5 0.8 4.3 43.8 0.8 4.9 36.9 0.9 5.5 120 252.7 0.5 1.3 176.7 0.6 1.8 130.2 0.6 2.3 101.7 0.6 2.8 81.7 0.7 3.3 66.5 0.7 3.8 54.8 0.8 4.3 45.7 0.8 4.9 38.5 0.9 5.5 125 263.3 0.5 1.3 184.1 0.6 1.8 135.6 0.6 2.3 106.0 0.6 2.8 85.1 0.7 3.3 69.3 0.7 3.8 57.1 0.8 4.3 47.6 0.8 4.9 40.1 0.9 5.5 130 273.8 0.5 1.3 191.5 0.6 1.8 141.0 0.6 2.3 110.2 0.6 2.8 88.5 0.7 3.3 72.0 0.7 3.8 59.4 0.8 4.3 49.5 0.8 4.9 41.7 0.9 5.5 135 284.3 0.5 1.3 198.8 0.6 1.8 146.4 0.6 2.3 114.4 0.6 2.8 91.9 0.7 3.3 74.8 0.7 3.8 61.6 0.8 4.3 51.4 0.8 4.9 43.3 0.9 5.5 140 294.9 0.5 1.3 206.2 0.6 1.8 151.8 0.6 2.3 118.7 0.6 2.8 95.3 0.7 3.3 77.6 0.7 3.8 63.9 0.8 4.3 53.3 0.8 4.9 44.9 0.9 5.5 145 305.4 0.5 1.3 213.6 0.6 1.8 157.3 0.6 2.3 122.9 0.6 2.8 98.7 0.7 3.3 80.3 0.7 3.8 66.2 0.8 4.3 55.2 0.8 4.9 46.5 0.9 5.5 150 315.9 0.5 1.3 220.9 0.6 1.8 162.7 0.6 2.3 127.1 0.6 2.8 102.1 0.7 3.3 83.1 0.7 3.8 68.5 0.8 4.3 57.1 0.8 4.9 48.1 0.9 5.5 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-269 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 8.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 12.0 0.5 1.3 8.5 0.5 1.7 6.2 0.5 2.2 4.6 0.6 2.7 3.7 0.6 3.2 2.9 0.7 3.6 10 24.1 0.5 1.3 16.9 0.5 1.7 12.6 0.5 2.2 9.6 0.6 2.7 7.8 0.6 3.2 6.3 0.6 3.7 5.1 0.7 4.2 4.2 0.8 4.8 3.2 0.9 5.3 15 36.1 0.5 1.3 25.3 0.5 1.7 18.9 0.5 2.2 14.4 0.6 2.7 11.8 0.6 3.2 9.7 0.6 3.7 7.9 0.7 4.2 6.5 0.7 4.8 5.4 0.8 5.3 20 48.1 0.5 1.3 33.8 0.5 1.7 25.2 0.5 2.2 19.2 0.6 2.7 15.8 0.6 3.2 12.9 0.6 3.7 10.7 0.7 4.2 8.8 0.7 4.8 7.4 0.8 5.3 25 60.1 0.5 1.3 42.2 0.5 1.7 31.5 0.5 2.2 24.0 0.6 2.7 19.7 0.6 3.2 16.2 0.6 3.7 13.4 0.7 4.2 11.2 0.7 4.7 9.3 0.8 5.3 30 72.1 0.5 1.3 50.6 0.5 1.7 37.8 0.5 2.2 28.8 0.6 2.7 23.6 0.6 3.2 19.4 0.6 3.7 16.1 0.7 4.2 13.5 0.7 4.8 11.3 0.7 5.3 35 84.1 0.5 1.3 59.1 0.5 1.7 44.1 0.5 2.2 33.6 0.6 2.7 27.6 0.6 3.2 22.6 0.6 3.7 18.7 0.7 4.2 15.7 0.7 4.8 13.3 0.7 5.3 40 96.2 0.5 1.3 67.5 0.5 1.7 50.4 0.5 2.2 38.4 0.6 2.7 31.5 0.6 3.2 25.8 0.6 3.7 21.4 0.7 4.2 17.9 0.7 4.8 15.2 0.7 5.3 45 108.2 0.5 1.3 76.0 0.5 1.7 56.7 0.5 2.2 43.2 0.6 2.7 35.4 0.6 3.2 29.0 0.6 3.7 24.1 0.7 4.2 20.2 0.7 4.8 17.1 0.7 5.3 50 120.2 0.5 1.3 84.4 0.5 1.7 63.0 0.5 2.2 48.0 0.6 2.7 39.4 0.6 3.2 32.3 0.6 3.7 26.8 0.7 4.2 22.4 0.7 4.8 19.0 0.7 5.3 55 132.2 0.5 1.3 92.8 0.5 1.7 69.3 0.5 2.2 52.8 0.6 2.7 43.3 0.6 3.2 35.5 0.6 3.7 29.4 0.7 4.2 24.7 0.7 4.8 20.9 0.7 5.3 60 144.2 0.5 1.3 101.3 0.5 1.7 75.6 0.5 2.2 57.6 0.6 2.7 47.2 0.6 3.2 38.7 0.6 3.7 32.1 0.7 4.2 26.9 0.7 4.8 22.8 0.7 5.3 65 156.3 0.5 1.3 109.7 0.5 1.7 81.8 0.5 2.2 62.4 0.6 2.7 51.2 0.6 3.2 41.9 0.6 3.7 34.8 0.7 4.2 29.1 0.7 4.8 24.7 0.7 5.3 70 168.3 0.5 1.3 118.2 0.5 1.7 88.1 0.5 2.2 67.2 0.6 2.7 55.1 0.6 3.2 45.2 0.6 3.7 37.5 0.7 4.2 31.4 0.7 4.8 26.6 0.7 5.3 75 180.3 0.5 1.3 126.6 0.5 1.7 94.4 0.5 2.2 72.0 0.6 2.7 59.0 0.6 3.2 48.4 0.6 3.7 40.1 0.7 4.2 33.6 0.7 4.8 28.5 0.7 5.3 80 192.3 0.5 1.3 135.0 0.5 1.7 100.7 0.5 2.2 76.8 0.6 2.7 63.0 0.6 3.2 51.6 0.6 3.7 42.8 0.7 4.2 35.9 0.7 4.8 30.3 0.7 5.3 85 204.3 0.5 1.3 143.5 0.5 1.7 107.0 0.5 2.2 81.6 0.6 2.7 66.9 0.6 3.2 54.9 0.6 3.7 45.5 0.7 4.2 38.1 0.7 4.8 32.2 0.7 5.3 90 216.4 0.5 1.3 151.9 0.5 1.7 113.3 0.5 2.2 86.4 0.6 2.7 70.8 0.6 3.2 58.1 0.6 3.7 48.1 0.7 4.2 40.3 0.7 4.8 34.1 0.7 5.3 95 228.4 0.5 1.3 160.3 0.5 1.7 119.6 0.5 2.2 91.2 0.6 2.7 74.8 0.6 3.2 61.3 0.6 3.7 50.8 0.7 4.2 42.6 0.7 4.8 36.0 0.7 5.3 100 240.4 0.5 1.3 168.8 0.5 1.7 125.9 0.5 2.2 96.0 0.6 2.7 78.7 0.6 3.2 64.5 0.6 3.7 53.5 0.7 4.2 44.8 0.7 4.8 37.9 0.7 5.3 105 252.4 0.5 1.3 177.2 0.5 1.7 132.2 0.5 2.2 100.8 0.6 2.7 82.6 0.6 3.2 67.8 0.6 3.7 56.2 0.7 4.2 47.1 0.7 4.8 39.8 0.7 5.3 110 264.4 0.5 1.3 185.7 0.5 1.7 138.5 0.5 2.2 105.6 0.6 2.7 86.6 0.6 3.2 71.0 0.6 3.7 58.8 0.7 4.2 49.3 0.7 4.8 41.7 0.7 5.3 115 276.5 0.5 1.3 194.1 0.5 1.7 144.8 0.5 2.2 110.4 0.6 2.7 90.5 0.6 3.2 74.2 0.6 3.7 61.5 0.7 4.2 51.5 0.7 4.8 43.6 0.7 5.3 120 288.5 0.5 1.3 202.5 0.5 1.7 151.1 0.5 2.2 115.2 0.6 2.7 94.4 0.6 3.2 77.4 0.6 3.7 64.2 0.7 4.2 53.8 0.7 4.8 45.5 0.7 5.3 125 300.5 0.5 1.3 211.0 0.5 1.7 157.4 0.5 2.2 120.0 0.6 2.7 98.4 0.6 3.2 80.7 0.6 3.7 66.9 0.7 4.2 56.0 0.7 4.8 47.4 0.7 5.3 130 312.5 0.5 1.3 219.4 0.5 1.7 163.7 0.5 2.2 124.8 0.6 2.7 102.3 0.6 3.2 83.9 0.6 3.7 69.5 0.7 4.2 58.3 0.7 4.8 49.3 0.7 5.3 135 324.5 0.5 1.3 227.9 0.5 1.7 170.0 0.5 2.2 129.6 0.6 2.7 106.2 0.6 3.2 87.1 0.6 3.7 72.2 0.7 4.2 60.5 0.7 4.8 51.2 0.7 5.3 140 336.6 0.5 1.3 236.3 0.5 1.7 176.3 0.5 2.2 134.4 0.6 2.7 110.2 0.6 3.2 90.3 0.6 3.7 74.9 0.7 4.2 62.7 0.7 4.8 53.1 0.7 5.3 145 348.6 0.5 1.3 244.7 0.5 1.7 182.6 0.5 2.2 139.2 0.6 2.7 114.1 0.6 3.2 93.6 0.6 3.7 77.6 0.7 4.2 65.0 0.7 4.8 55.0 0.7 5.3 150 360.6 0.5 1.3 253.2 0.5 1.7 188.9 0.5 2.2 144.0 0.6 2.7 118.0 0.6 3.2 96.8 0.6 3.7 80.2 0.7 4.2 67.2 0.7 4.8 56.9 0.7 5.3 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-270 2016 Edition Table 6-28.2. Design Chart for Parabolic Vegetated Diversion, Waterway or Stormwater Conveyance (Continued) V1 FOR RETARDANCE TOP WIDTH DEPTH AND V2 FOR RETARDANCE Grade 10.00 Percent T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 T D V2 5 13.3 0.4 1.3 9.4 0.5 1.7 6.8 0.5 2.2 5.3 0.5 2.6 4.1 0.6 3.2 3.4 0.6 3.6 2.6 0.7 4.1 10 26.6 0.4 1.3 18.7 0.5 1.7 13.8 0.5 2.2 10.9 0.5 2.6 8.5 0.6 3.2 7.1 0.6 3.6 5.9 0.6 4.1 4.9 0.7 4.7 4.0 0.7 5.3 15 39.9 0.4 1.3 28.0 0.5 1.7 20.7 0.5 2.2 16.3 0.5 2.6 12.8 0.6 3.2 10.9 0.6 3.6 9.0 0.6 4.1 7.5 0.6 4.7 6.3 0.7 5.2 20 53.2 0.4 1.3 37.4 0.5 1.7 27.6 0.5 2.2 21.7 0.5 2.7 17.0 0.6 3.2 14.5 0.6 3.6 12.1 0.6 4.1 10.2 0.6 4.6 8.5 0.7 5.2 25 66.5 0.4 1.3 46.7 0.5 1.7 34.5 0.5 2.2 27.1 0.5 2.7 21.3 0.6 3.2 18.1 0.6 3.6 15.1 0.6 4.1 12.7 0.6 4.7 10.8 0.7 5.2 30 79.8 0.4 1.3 56.1 0.5 1.7 41.4 0.5 2.2 32.5 0.5 2.7 25.5 0.6 3.2 21.7 0.6 3.6 18.1 0.6 4.1 15.2 0.6 4.7 12.9 0.7 5.2 35 93.1 0.4 1.3 65.4 0.5 1.7 48.3 0.5 2.2 37.9 0.5 2.7 29.8 0.6 3.2 25.3 0.6 3.6 21.1 0.6 4.1 17.8 0.6 4.7 15.1 0.7 5.2 40 106.4 0.4 1.3 74.7 0.5 1.7 55.2 0.5 2.2 43.3 0.5 2.7 34.0 0.6 3.2 29.0 0.6 3.6 24.1 0.6 4.1 20.3 0.6 4.7 17.2 0.7 5.2 45 119.7 0.4 1.3 84.1 0.5 1.7 62.1 0.5 2.2 48.8 0.5 2.7 38.3 0.6 3.2 32.6 0.6 3.6 27.2 0.6 4.1 22.8 0.6 4.7 19.4 0.7 5.2 50 133.0 0.4 1.3 93.4 0.5 1.7 69.0 0.5 2.2 54.2 0.5 2.7 42.5 0.6 3.2 36.2 0.6 3.6 30.2 0.6 4.1 25.4 0.6 4.7 21.5 0.7 5.2 55 146.3 0.4 1.3 102.8 0.5 1.7 75.9 0.5 2.2 59.6 0.5 2.7 46.8 0.6 3.2 39.8 0.6 3.6 33.2 0.6 4.1 27.9 0.6 4.7 23.7 0.7 5.2 60 159.6 0.4 1.3 112.1 0.5 1.7 82.8 0.5 2.2 65.0 0.5 2.7 51.0 0.6 3.2 43.4 0.6 3.6 36.2 0.6 4.1 30.5 0.6 4.7 25.9 0.7 5.2 65 172.9 0.4 1.3 121.4 0.5 1.7 89.7 0.5 2.2 70.4 0.5 2.7 55.3 0.6 3.2 47.1 0.6 3.6 39.2 0.6 4.1 33.0 0.6 4.7 28.0 0.7 5.2 70 186.2 0.4 1.3 130.8 0.5 1.7 96.6 0.5 2.2 75.8 0.5 2.7 59.5 0.6 3.2 50.7 0.6 3.6 42.2 0.6 4.1 35.5 0.6 4.7 30.2 0.7 5.2 75 199.5 0.4 1.3 140.1 0.5 1.7 103.5 0.5 2.2 81.2 0.5 2.7 63.8 0.6 3.2 54.3 0.6 3.6 45.2 0.6 4.1 38.1 0.6 4.7 32.3 0.7 5.2 80 212.8 0.4 1.3 149.5 0.5 1.7 110.5 0.5 2.2 86.7 0.5 2.7 68.0 0.6 3.2 57.9 0.6 3.6 48.3 0.6 4.1 40.6 0.6 4.7 34.5 0.7 5.2 85 226.1 0.4 1.3 158.8 0.5 1.7 117.4 0.5 2.2 92.1 0.5 2.7 72.3 0.6 3.2 61.5 0.6 3.6 51.3 0.6 4.1 43.1 0.6 4.7 36.6 0.7 5.2 90 239.4 0.4 1.3 168.1 0.5 1.7 124.3 0.5 2.2 97.5 0.5 2.7 76.5 0.6 3.2 65.2 0.6 3.6 54.3 0.6 4.1 45.7 0.6 4.7 38.8 0.7 5.2 95 252.7 0.4 1.3 177.5 0.5 1.7 131.2 0.5 2.2 102.9 0.5 2.7 80.8 0.6 3.2 68.8 0.6 3.6 57.3 0.6 4.1 48.2 0.6 4.7 40.9 0.7 5.2 100 266.0 0.4 1.3 186.8 0.5 1.7 138.1 0.5 2.2 108.3 0.5 2.7 85.0 0.6 3.2 72.4 0.6 3.6 60.3 0.6 4.1 50.7 0.6 4.7 43.1 0.7 5.2 105 279.3 0.4 1.3 196.2 0.5 1.7 145.0 0.5 2.2 113.7 0.5 2.7 89.3 0.6 3.2 76.0 0.6 3.6 63.3 0.6 4.1 53.3 0.6 4.7 45.2 0.7 5.2 110 292.6 0.4 1.3 205.5 0.5 1.7 151.9 0.5 2.2 119.2 0.5 2.7 93.5 0.6 3.2 79.6 0.6 3.6 66.4 0.6 4.1 55.8 0.6 4.7 47.4 0.7 5.2 115 305.9 0.4 1.3 214.9 0.5 1.7 158.8 0.5 2.2 124.6 0.5 2.7 97.8 0.6 3.2 83.3 0.6 3.6 69.4 0.6 4.1 58.3 0.6 4.7 49.5 0.7 5.3 120 319.2 0.4 1.3 224.2 0.5 1.7 165.7 0.5 2.2 130.0 0.5 2.7 102.0 0.6 3.2 86.9 0.6 3.6 72.4 0.6 4.1 60.9 0.6 4.7 51.7 0.7 5.3 125 332.5 0.4 1.3 233.5 0.5 1.7 172.6 0.5 2.2 135.4 0.5 2.7 106.3 0.6 3.2 90.5 0.6 3.6 75.4 0.6 4.1 63.4 0.6 4.7 53.8 0.7 5.3 130 345.8 0.4 1.3 242.9 0.5 1.7 179.5 0.5 2.2 140.8 0.5 2.7 110.5 0.6 3.2 94.1 0.6 3.6 78.4 0.6 4.1 66.0 0.6 4.7 56.0 0.7 5.3 135 359.1 0.4 1.3 252.2 0.5 1.7 186.4 0.5 2.2 146.2 0.5 2.7 114.8 0.6 3.2 97.7 0.6 3.6 81.4 0.6 4.1 68.5 0.6 4.7 58.1 0.7 5.3 140 372.4 0.4 1.3 261.6 0.5 1.7 193.3 0.5 2.2 151.7 0.5 2.7 119.0 0.6 3.2 101.3 0.6 3.6 84.4 0.6 4.1 71.0 0.6 4.7 60.3 0.7 5.3 145 385.7 0.4 1.3 270.9 0.5 1.7 200.2 0.5 2.2 157.1 0.5 2.7 123.3 0.6 3.2 105.0 0.6 3.6 87.5 0.6 4.1 73.6 0.6 4.7 62.5 0.7 5.3 150 399.0 0.4 1.3 280.2 0.5 1.7 207.1 0.5 2.2 162.5 0.5 2.7 127.5 0.6 3.2 108.6 0.6 3.6 90.5 0.6 4.1 76.1 0.6 4.7 64.6 0.7 5.3 Q CFS V1=2.0 V1=2.5 V1=3.0 V1=3.5 V1=4.0 V1=4.5 V1=5.0 V1=5.5 V1=6.0 RETARDANCE AND NOTE: Width and Depth dimensions are in feet; Velocity measurements are in feet per second; Depth does not include allowance for freeboard or settlement. Table 6-39.2. Table 6-39.2. ---PAGE BREAK--- 6-271 2016 Edition Table 6-28.3. Diversion Design Table D Retardance (V and Trapezoidal Section) (Based on Handbook of Channel Design, SCS-TP-61) NOTE: For diversions built on slopes under the available cross-sectional area above normal ground will allow a reduction in design depth as follows: For land slopes of 1% or less, reduce depth of flow (taken from Design Table) 20%. For land Slopes of 1% to reduce depth of flow (taken from Design Table) 10%. For land slopes greater than use depth of flow taken from Design Table. For Example: A diversion 6 feet wide with a 2.5 foot depth of flow is required to remove 120 c.f.s. on a 0.4% grade. If this is built on a 1% slope, the depth may be reduced 20%, thus obtaining a flow depth of 2.0 feet. The required cross- sectional area of the channel plus that above normal ground line will be 34 square feet corresponding to the 2.5 foot depth. The overall height of diversion will be 2.0 feet plus 0.5 foot freeboard or 2.5 feet, instead of the original 3.0 feet. z z 6" depth of flow Normal ground Freeboard Approximately 3:1 A d b d = depth of flow, feet b = bottom width of channel, feet A = channel capacity, sq. ft., including area below 0.5' freeboard and excluding any area less than 0.5' depth of flow z = side slope of channel (horizontal to vertical) To all designed depth of flow add freeboard required by State Standards and Specifications to obtain overall height of terrace above bottom of channel. For final check on cross-sectional area, subtract required freeboard from settled height of diversion and provide for cross-sectional area shown in table. IMPORTANT: 3:1 Side Slopes Retardance % Triangular 6' bottom width 8' bottom width 10' bottom width 12' bottom width Grade 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 Q-cfs d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d 10 1.9 11 1.8 10 1.7 9 1.6 8 1.3 12 1.1 10 1.0 9 0.9 8 1.2 13 1.1 11 1.0 10 0.9 9 1.1 14 1.0 12 0.9 11 0.8 10 1.0 14 0.9 12 0.8 11 0.7 20 2.2 15 2.1 13 1.9 11 1.8 10 1.5 16 1.4 14 1.2 12 1.1 10 1.4 17 1.3 16 1.2 14 1.1 12 1.3 18 1.2 16 1.0 13 0.9 11 1.2 19 1.1 17 1.0 15 0.9 30 2.5 19 2.3 16 2.2 15 2.0 12 1.8 21 1.6 17 1.5 16 1.3 13 1.7 22 1.5 19 1.4 17 1.2 14 1.5 22 1.4 20 1.2 16 1.1 15 1.3 21 1.2 19 1.2 19 1.1 40 2.6 20 2.5 19 2.3 16 2.2 15 2.0 24 1.8 21 1.7 19 1.5 16 1.8 24 1.7 22 1.5 19 1.4 17 1.7 26 1.5 22 1.4 20 1.2 16 1.6 27 1.5 25 1.3 21 1.2 60 3.0 27 2.8 24 2.7 22 2.5 19 2.3 30 2.1 26 1.9 22 1.7 19 2.1 30 1.9 26 1.8 24 1.6 21 2.0 32 1.8 28 1.7 26 1.5 22 1.8 31 1.6 27 1.5 25 1.3 80 3.1 29 2.9 25 2.7 22 2.5 34 2.3 30 2.1 26 1.9 22 2.4 37 2.2 32 2.0 28 1.8 24 2.3 39 2.1 34 1.9 30 1.7 26 2.1 38 1.9 34 1.8 31 1.6 100 3.1 29 2.9 25 2.8 40 2.5 34 2.3 30 2.1 26 2.6 41 2.4 37 2.2 32 2.0 28 2.4 41 2.2 37 2.1 34 1.9 30 2.3 44 2.1 38 1.9 34 1.7 120 3.0 27 3.0 45 2.8 40 2.5 34 2.3 30 2.8 46 2.5 39 2.3 34 2.1 30 2.6 46 2.4 41 2.2 37 2.0 32 2.5 50 2.3 44 2.1 38 1.9 140 2.9 43 2.6 36 2.4 32 2.9 48 2.7 44 2.5 39 2.3 34 2.7 49 2.5 44 2.3 39 2.1 34 2.6 52 2.4 46 2.2 41 2.0 160 3.0 45 2.8 40 2.6 36 3.1 51 2.9 48 2.7 44 2.5 39 2.9 54 2.7 49 2.5 44 2.3 39 2.7 54 2.5 50 2.3 44 2.1 180 2.6 41 3.0 57 2.8 51 2.6 46 2.4 41 2.8 57 2.6 52 2.4 46 2.2 200 2.5 44 2.9 60 2.7 54 2.5 50 2.3 220 3.0 63 2.8 57 2.7 54 2.5 A 10 13 17 19 21 27 29 34 36 38 41 44 50 Table 6-39.3. Table 6-39.3. ---PAGE BREAK--- 6-272 2016 Edition Table 6-28.3. Diversion Design Table D Retardance (V and Trapezoidal Section) (Continued) (Based on Handbook of Channel Design, SCS-TP-61) 4:1 Side Slopes Retardance 6:1 Side Slopes Retardance A 12 14 18 20 22 29 32 35 40 43 46 49 52 % Triangular 6' bottom width 8' bottom width 10' bottom width 12' bottom width Grade 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 Q-cfs d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d 10 1.8 13 1.7 12 1.6 11 1.5 10 1.2 13 1.1 11 1.0 10 0.9 9 1.1 14 1.0 13 0.9 11 08 10 1.1 14 1.0 13 0.9 12 0.8 11 1.0 15 0.9 14 0.8 13 0.7 20 2.1 18 2.0 16 1.8 13 1.7 12 1.5 18 1.4 16 1.2 13 1.1 11 1.4 19 1.3 17 1.2 15 1.1 14 1.3 20 1.2 18 1.0 14 0.9 12 1.2 20 1.1 18 1.0 16 0.9 30 2.4 23 2.2 19 2.1 18 1.9 14 1.8 24 1.6 20 1.5 18 1.3 15 1.7 25 1.5 21 1.4 19 1.2 15 1.5 24 1.4 22 1.2 18 1.1 16 1.3 22 1.2 20 1.2 20 1.1 40 2.5 25 2.4 23 2.2 19 2.1 18 1.9 26 1.8 24 1.6 20 1.5 18 1.8 27 1.7 25 1.5 21 1.4 19 1.6 26 1.5 24 1.3 20 1.2 18 1.6 29 1.5 27 1.3 22 1.2 60 2.8 31 2.6 27 2.5 25 2.3 21 2.2 33 2.0 28 1.9 26 1.7 22 2.0 32 1.9 30 1.7 25 1.6 23 1.9 33 1.8 31 1.6 26 1.5 24 1.7 32 1.6 29 1.4 25 1.3 80 3.1 38 2.9 34 2.7 29 2.5 25 2.4 37 2.2 33 2.1 30 1.9 26 2.3 40 2.1 34 2.0 32 1.8 27 2.2 41 2.0 36 1.8 31 1.6 26 2.0 40 1.9 37 1.7 32 1.6 100 3.1 38 2.9 34 2.7 29 2.7 45 2.5 40 2.3 35 2.1 30 2.5 45 2.3 40 2.1 34 1.9 30 2.3 44 2.1 39 2.0 36 1.8 31 2.2 46 2.0 40 1.9 37 1.7 120 2.8 31 2.9 51 2.7 45 2.4 37 2.2 33 2.7 51 2.5 45 2.3 40 2.1 34 2.5 50 2.3 44 2.2 41 2.0 36 2.4 52 2.2 46 2.0 40 1.8 140 3.0 54 2.8 48 2.6 43 2.4 37 2.8 54 2.6 48 2.5 45 2.3 40 2.6 53 2.4 47 2.3 44 2.1 39 2.5 55 2.3 49 2.2 46 2.0 160 3.1 57 2.9 51 2.8 48 2.6 43 3.0 60 2.8 54 2.6 48 2.4 42 2.8 59 2.6 53 2.5 50 2.3 44 2.7 62 2.5 55 2.3 49 2.1 180 2.5 45 2.9 63 2.7 56 2.6 53 2.4 47 2.8 65 2.6 58 2.4 52 2.2 200 2.5 50 2.9 68 2.7 62 2.5 55 2.3 220 3.0 72 2.8 65 2.6 58 2.4 % Triangular 6' bottom width 8' bottom width 10' bottom width 12' bottom width Grade 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 Q-cfs d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d 10 1.6 15 1.5 14 1.4 13 1.3 11 1.2 16 1.1 14 1.0 12 0.9 10 1.1 16 1.0 14 0.9 13 0.8 11 1.1 17 1.0 15 0.9 13 0.8 12 1.0 17 0.9 15 0.8 14 0.7 20 1.9 22 1.8 19 1.6 15 1.5 14 1.5 23 1.4 20 1.2 16 1.1 14 1.4 23 1.3 21 1.1 16 1.0 14 1.3 21 1.2 20 1.1 18 1.0 16 1.3 25 1.2 23 1.0 17 0.9 30 2.1 27 2.0 24 1.8 19 1.7 17 1.7 28 1.5 23 1.4 20 1.2 16 1.6 28 1.5 26 1.3 21 1.2 18 1.4 26 1.3 23 1.2 20 1.1 18 1.4 29 1 3 27 1.1 20 1.0 40 2.3 32 2.2 29 2.0 24 1.8 19 1.8 30 1.7 28 1.5 23 1.4 20 1.7 31 1.6 28 1.4 23 1.3 21 1.5 29 1.4 26 1.3 23 1.2 20 1.5 32 1.4 29 1.3 27 1.2 60 2.5 38 2.3 32 2.2 29 2.0 24 2.0 36 1.9 33 1.7 28 1.6 25 1.9 37 1.8 34 1.6 28 1.5 26 1.8 38 1.7 34 1.5 29 1.4 26 1.6 34 1.5 32 1.4 29 1.3 80 2.7 44 2.5 38 2.4 35 2.2 29 2.2 42 2.1 39 1.9 33 1.8 30 2.1 43 2.0 40 1.8 34 1.7 31 2.0 44 1.9 41 1.7 34 1.6 31 1.8 41 1.7 37 1.6 34 1.5 100 2.9 51 2.7 44 2.6 41 2.4 35 2.4 49 2.2 42 2.1 39 1.9 33 2.3 50 2.1 43 2.0 40 1.8 34 2.2 51 2.0 44 1.9 41 1.7 34 2.1 51 1.9 45 1.8 41 1.6 120 3.0 54 2.8 47 2.7 44 2.5 38 2.6 56 2.4 49 2.3 46 2.1 39 2.5 58 2.3 50 2.2 47 2.0 40 2.3 55 2.2 51 2.0 44 1.9 41 2.2 55 2.0 48 1.9 45 1.7 140 2.7 61 2.6 56 2.4 49 2.3 46 2.6 61 2.5 58 2.3 50 2.2 47 2.5 63 2.3 55 2.2 51 2.0 44 2.4 64 2.2 55 2.1 51 1.9 160 2.9 68 2.8 64 2.6 56 2.5 53 2.8 67 2.6 61 2.5 58 2.3 50 2.7 71 2.5 63 2.4 59 2.2 51 2.6 70 2.4 64 2.3 59 2.1 180 2.9 71 2.7 64 2.6 61 2.4 54 2.8 75 2.6 67 2.5 63 2.3 55 2.7 76 2.5 68 2.4 63 2.2 200 3.0 72 2.8 67 2.6 61 2.4 54 2.9 79 2.7 77 2.6 67 2.4 59 2.8 81 2.6 72 2.5 68 2.3 220 2.5 58 2.4 59 2.9 85 2.7 76 2.5 68 2.3 240 2.5 63 2.4 260 2.5 A 12 16 18 22 27 32 34 37 45 51 55 59 59 64 68 Table 6-39.3. Table 6-39.3. ---PAGE BREAK--- 6-273 2016 Edition Table 6-28.4. Diversion Design Table C Retardance (V and Trapezoidal Section) (Based on Handbook of Channel Design, SCS-TP-61) 3:1 Side Slopes Retardance 4:1 Side Slopes Retardance % Triangular 6' bottom width 8' bottom width 10' bottom width 12' bottom width Grade 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 Q d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d 20 2.5 19 2.3 16 2.1 13 1.9 11 1.9 22 1.7 19 1.5 16 1.4 14 1.7 22 1.5 19 1.4 17 1.3 15 1.6 24 1.4 20 1.3 18 1.2 16 30 2.5 19 2.3 16 2.2 15 2.0 24 1.8 21 1.7 19 1.5 16 1.9 26 1.7 22 1.5 19 1.4 17 1.7 26 1.5 22 1.4 20 1.3 18 1.6 27 1.4 23 1.3 21 1.2 40 2.5 19 2.4 17 2.2 28 2.0 24 1.9 22 1.7 19 2.0 28 1.8 24 1.6 21 1.5 19 1.9 30 1.7 26 1.5 22 1.4 20 1.8 31 1.6 27 1.5 25 1.4 50 2.5 19 2.3 30 2.1 26 2.0 24 1.8 21 2.2 32 2.0 28 1.8 24 1.6 21 2.0 32 1.8 28 1.6 24 1.5 22 1.9 34 1.7 29 1.6 27 1.5 60 2.5 34 2.3 30 2.1 26 1.9 22 2.3 34 2.1 30 1.9 26 1.8 24 2.2 37 2.0 32 1.8 28 1.6 24 2.0 36 1.8 31 1.7 29 1.6 80 2.5 34 2.3 30 2.1 26 2.5 39 2.3 34 2.1 30 1.9 26 2.4 41 2.2 37 2.0 32 1.8 28 2.2 41 2.0 36 1.9 34 1.7 100 2.5 34 2.3 30 2.5 39 2.3 34 2.1 30 2.4 41 2.2 37 2.0 32 2.5 49 2.2 41 2.0 36 1.8 120 2.5 34 2.5 39 2.3 34 2.3 39 2.1 34 2.4 46 2.2 41 2.0 140 2.4 36 2.5 44 2.3 39 2.3 43 2.1 160 2.4 41 2.4 46 2.2 180 2.5 44 2.4 200 2.5 220 2.6 A 19 23 25 27 29 31 36 38 41 46 49 51 % Triangular 6' bottom width 8' bottom width 10' bottom width 12' bottom width Grade 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 Q d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d 30 2.5 25 2.4 23 2.3 21 2.1 18 2.0 28 1.8 24 1.6 20 1.5 18 1.8 27 1.7 25 1.5 21 1.4 19 1.8 31 1.6 26 1.4 22 1.3 20 1.7 32 1.6 29 1.4 25 1.2 40 2.5 25 2.4 23 2.2 19 2.1 30 1.9 26 1.7 22 1.6 20 2.0 32 1.8 27 1.6 23 1.5 21 1.9 33 1.7 29 1.5 24 1.4 22 1.8 35 1.7 32 1.5 27 1.3 50 2.5 25 2.4 23 2.3 35 2.1 30 1.9 26 1.7 22 2.1 34 1.9 30 1.7 25 1.6 23 2.0 36 1.8 31 1.6 26 1.5 24 1.9 37 1.8 35 1.6 29 1.4 60 2.5 25 2.4 37 2.2 33 2.0 28 1.9 26 2.3 40 2.1 34 1.9 30 1.7 25 2.1 39 1.9 34 1.7 29 1.6 26 2.0 40 1.9 37 1.7 32 1.5 80 2.4 37 2.2 33 2.0 28 2.5 45 2.3 40 2.1 34 1.9 30 2.3 44 2.1 39 1.9 34 1.8 31 2.2 46 2.0 40 1.8 35 1.7 100 2.5 40 2.3 35 2.2 33 2.5 45 2.3 40 2.0 32 2.5 50 2.3 44 2.1 39 1.9 34 2.3 49 2.1 43 2.0 40 1.8 120 2.5 40 2.4 37 2.4 42 2.2 37 2.5 50 2.3 44 2.1 39 2.5 55 2.3 49 2.2 46 2.0 140 2.5 40 2.5 45 2.3 40 2.4 47 2.2 41 2.5 55 2.3 49 2.1 160 2.5 45 2.5 50 2.3 44 2.4 52 2.2 180 2.4 47 2.5 55 2.3 200 2.5 50 2.4 220 2.5 A 20 22 25 27 32 35 40 43 46 49 52 55 Table 6-39.4. Table 6-39.4. ---PAGE BREAK--- 6-274 2016 Edition Table 6-28.4. Diversion Design Table C Retardance (V and Trapezoidal Section) (Continued) (Based on Handbook of Channel Design, SCS-TP-61) 6:1 Side Slopes Retardance % Triangular 6' bottom width 8' bottom width 10' bottom width 12' bottom width Grade 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 2 3 4 5 Q d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d A d 20 2.2 29 2.1 26 1.9 22 1.8 19 1.8 30 1.7 28 1.6 25 1.4 20 1.7 31 1.6 28 1.5 26 1.3 21 1.6 31 1.5 29 1.4 26 1.2 20 1.5 32 1.4 29 1.3 27 1.2 30 2.4 35 2.2 29 2.1 26 1.9 22 2.0 36 1.9 33 1.7 28 1.5 23 1.8 34 1.7 31 1.6 28 1.4 23 1.8 38 1.7 34 1.5 29 1.3 23 1.7 37 1.6 34 1.4 29 1.3 40 2.5 38 2.3 32 2.2 29 2.0 24 2.1 39 2.0 36 1.8 30 1.6 25 2.0 40 1.9 37 1.7 31 1.5 26 1.9 41 1.8 38 1.6 31 1.4 26 1.8 41 1.7 37 1.5 32 1.3 50 2.5 38 2.3 32 2.1 26 2.2 42 2.1 39 1.9 33 1.7 28 2.1 43 2.0 40 1.8 34 1.6 28 2.0 44 1.9 41 1.7 34 1.5 29 1.9 45 1.8 41 1.6 34 1.4 60 2.4 35 2.2 29 2.3 46 2.2 42 2.0 36 1.8 30 2.2 47 2.1 43 1.9 37 1.7 31 2.1 47 2.0 44 1.8 38 1.6 31 2.0 48 1.9 45 1.8 41 1.6 80 2.5 38 2.3 32 2.5 53 2.3 46 2.1 39 1.9 33 2.4 54 2.2 47 2.0 40 1.8 34 2.3 55 2.1 47 1.9 41 1.7 34 2.2 55 2.1 52 1.9 45 1.7 100 2.5 38 2.5 53 2.3 46 2.1 39 2.5 58 2.4 54 2.2 47 2.0 40 2.4 59 2.3 55 2.1 47 1.9 41 2.3 59 2.2 55 2.0 48 1.8 120 2.4 49 2.2 42 2.5 58 2.3 50 2.1 43 2.5 63 2.4 59 2.2 51 2.0 44 2.4 64 2.3 59 2.1 52 1.9 140 2.5 53 2.3 46 2.4 54 2.2 47 2.5 63 2.3 55 2.1 47 2.5 68 2.4 64 2.2 55 2.0 160 2.4 49 2.5 58 2.3 50 2.4 59 2.2 51 2.5 68 2.3 59 2.1 180 2.5 53 2.4 54 2.5 63 2.3 55 2.4 64 2.2 200 2.5 58 2.4 59 2.5 68 2.2 220 2.5 63 2.3 A 22 27 27 29 34 37 41 45 48 52 55 55 59 Table 6-39.4. Table 6-39.4. ---PAGE BREAK--- A-1-1 2016 Edition APPENDIX A WinTR-55 and TR-20 National Engineering Handbook, Part 630, Hydrology (NEH630) The Soil Conservation Service (SCS, now NRCS) first developed the National Engineer­ ing Handbook, Section 4, Hydrology (NEH-4) as a means of documenting the procedures which were being developed for evaluating the hydrol­ ogy of watersheds in watershed planning proj­ ects. Prior to this time (the early 1950s), there was no comprehensive guidance available for such projects. Later, the SCS became the Natu­ ral Resources Conservation Service (NRCS) and the NEH-4 was renamed to be the National Engineering Handbook, Part 630, Hydrology (NEH630). NEH630 documents the technical aspects of the hydrologic methodologies used to de­ velop runoff hydrographs, to a limited extent, to route such hydrographs. The NRCS NEH Part 630 can be downloaded by chapter from the NRCS eDirectives web-site at: http://di­ rectives.sc.egov.usda.gov/viewDirective. aspx?hid=21422 TECHNICAL RELEASE NO. 20: PROJECT FORMULATION – HYDROLOGY (TR-20) Technical Release No. 20, Project Formu­ lation – Hydrology (TR-20) was developed in the 1960s to automate the hydrologic evalua­ tion of large multi-sub-area watersheds using procedures found in the National Engineering Handbook, Section 4, Hydrology (NEH-4) TR-20 was originally issued as a mainframe computer program designed to run on a Harris mainframe system. In the 1980s, TR-20 was updated to run in a disk-operating system (DOS) environment on a personal computer (PC). Eventually, TR-20 was updated to run in a Windows environment on the PC. In this iteration, the computation en­ gine, TR-20, sits behind the graphical user inter­ face, WinTR-20 which allows users to enter, edit, and display input date; run the TR-20 model; and display output. TR-20 develops full hydrographs at user speci­ fied locations throughout a watershed and allows the user to route the hydrographs through stream channels and structures based on user input rat­ ing curves. The TR-20 model has been updated over time to take advantage of advances and updates in hydrologic science. One example of this is the procedure used to route hydrographs through stream channels. The original TR-20 utilized the convex routing procedure. Later that was replaced by the Att-Kin method. The current TR-20/WinTR-20 uses the Muskingum-Cunge method. The current WinTR-20 computer pro­ gram and documentation can be downloaded from the following web-site: http://www. nrcs.usda.gov/wps/portal/nrcs/detailfull/ TECHNICAL RELEASE NO. 55 IN,URBAN HYDROLOGY FOR SMALL WATERSHEDS (TR-55) Technical Release No. 55, Urban Hydrology for Small Watersheds (TR-55) was originally developed in 1975 in response to an increased focus on the analysis of small urbanizing water­ sheds. The procedures found in the SCS-TP 149, A Method for Estimating Volume and Rate of Runoff in Small Watersheds (which later morphed into the Engineering Field Manual Chapter 2, Estimating Runoff Volume and Peak Discharge), and the methodologies found in the NEH-4 were focused on agricultural watersheds. The curve number tables found in NEH-4 and TP-149 did not cover urban or urbanizing areas. TR-55 expanded the curve number tables to include urban and urbanizing areas. TR-55 was developed as a manual method by utilizing multiple runs of TR-20 to develop generalized tables and graphs from the output to cover a range of watershed conditions, primarily restricted by time of concentration. Contrary to popular belief, TR-55 was not limited to water­ sheds of a specific size, but instead was limited to watersheds with times of concentration rang­ ing from 0.1 to 5 hours Additionally, the 1975 version of TR-55 ---PAGE BREAK--- A-1-2 2016 Edition covered only areas for which the Type II rainfall distribution was appropriate. The 1986 version of the TR-55 added generalized curves and tables for Types I, IA, and III rainfall distributions and expanded the range of applicability for time of concentration up to 10 hours. A DOS based TR55 computer program was also developed in the 1980s. This computer program was a sort of spread-sheet based program that mirrored the published document. TR-55 gives the user an estimate of runoff volume and a peak discharge estimate, or in the case of the tabular method, a partial hydrograph bracketing the peak discharge. NRCS no longer supports (updates) TR-55 and no longer encourages its use. We do under­ stand that TR-55 has gained widespread accep­ tance and use, so, while it is not available as an official NRCS directive, we do still make it avail­ able for download. Information on downloading the 1986 TR-55 and accompanying computer program can be found at the following web-site http://www.nrcs.usda.gov/Internet/FSE_DOC­ which provides links for this and other computer programs no longer supported by NRCS. The updated WinTR-55 computer program, Small Watershed Hydrology, was developed as a windows update/replacement to the DOS based TR55 computer program. While TR55 was based on generalized tables and graphs to provide an estimate of peak discharge and al­ lowed the user to develop a partial hydrograph, the WinTR-55 computer program uses the latest TR-20 computational engine (behind the Win­ TR-55 graphical user interface) to compute full hydrographs. The limitations, now including a drainage area size limitation, placed on WinTR-55 were done so in order to limit its use to watershed similar to those that could be modeled with the DOS based TR55. A more complete discussion of the differenc­ es between TR55 and WinTR-55 can be found in a technical paper The New USDA-NRCS WinTR-55 Small Watershed Hydrology Model by Claudia Scheer and Karl Visser, and presented at the 2002 Federal Interagency Hydrologic Mod­ eling Conference, Las Vegas, NV can be found in the conference proceedings (pp. 404-410) through the following web-site: http://acwi.gov/ ings/index.html/ (Please note that the web-links referenced in the paper (including the e-mail ad­ dresses) are no longer valid). The WinTR-55 computer program can be down­ loaded at: http://www.nrcs.usda.gov/wps/portal/nrcs/de­ Additional information on all NRCS hydrologic tools and methodologies can be found at: http://www.nrcs.usda.gov/wps/portal/nrcs/ main/national/technical/alphabetical/water/hy­ drology. The “Tools and Models” and “Technical Information” links specifically link to a great deal of additional information. WIN TR-20 BACKGROUND Using a 24- hr design storm distribution is standard practice in Win TR-20. In order to best reflect the updated NOAA Atlas 14 precipication data, a site specific distribution iis developed based on the text file download from the NOAA Atlas 14 website. The 24- hr design storm distribution is developed based on maximixing the rainfall during and duration from 5-minutes to 24-hours. The duration from 5 minutes to 24 hours are centered on 12 hours and extended symmetrically for the periods before and after 12 hours. Investigations were conducted which showed that regional storm distribution similar to the prior standard NRCS storm distributions (Type 1, Type IA, Type II and Type III) are not feasible in states covered by NOAA Atlas 14. TO DATA SMOOTHING TECHNIQUE Several mathematical techniques were inves­ tigated to determine a computationally efficient, accurate, practical, stable and robust procedure. Since the generated hydrograph is primarily dependent on the relationship of precipitation intensity with duration, this relationship is what is smoothed. This relationship of intensity (inches/ hour) and duration is based on a factor defined as incremental intensity. Incremental intensity is ---PAGE BREAK--- A-1-3 2016 Edition defined as the difference in precipitation divided by the difference in duration. The incremen­ tal intensity for the 5-minute duration is equal to the 5-minute precipitation divided by ½ and has the units of inches per hour (or mm/hour in metric units). The incremental intensity for the 10 minute duration is the 10-minute precipitation minus the 5 and 10 minutes in units of hours. Each incremental intensity is calculated based on the difference in precipitation divided by the difference in duration. Incremental intensity is calculated and smoothed for each return period independently. The final smoothing procedure keeps the 5-min­ ute, 60-minute and 24-hour precipitation un­ changed from the original NOAA Atlas 14 values. 10,15,30 and 120-minute and 3,6,12-hour values are open to adjustment. The incremental inten­ sity for the 5-minute duration is unchanged. A straight line on the log-log plot extends from 5-minute to 60–minute duration. A second straight line segment on the log-log plot extends from the 60-minute value to 24-hour value. CONCLUSION and SUMMARY – the user has the option to develop storm distributions based on the original NOAA Atlas 14 data or smoothed data. Comparing hydrographs generated by original and smoothed data indicated that with the smoothed data, peak discharges may vary by as much as plus or minus 10%. OVERVIEW The Win TR-20 System Controller/Editor al­ lows running on any of the system components (TR-20 model, input convertor, import NOAA Atlas data, and HEC-RAS reformatter) as well as editing a WinTR-20 input file. The Controller/ Editor is organized following the input sections described in the user documentation. For edit­ ing, each WinTR-20 input section has its own entry window which is accessible by clicking the input section name on the main window. In ad­ dition to the input section entry windows, there are entry windows for locally added land used identifiers runoff curve numbers by hydrologic soil group) and locally added soils applicable hydrologic soil groups). Entry windows for these two local additions are accessible from the File pull down on main window. HELP FACILITIES Help windows of a general nature on the program system are available via the new user button (available at program start up) or from the Help pull down on the main window. All of the Help windows are available from the pull down while only selected ones are available via the “New User ? Click Here” button. The data entry window that allow for entry and/ or editing of input data contain additional Help in the form of information about the current window and the information about each variable to be entered. This Help is available by clicking the window or variable name on the entry window. A Help box opens in the lower left corner of the entry window and displays the window or vari­ able name, its description and range of values (if appropriate). Only window and variable names shown in yellow have such help available. A second click on the window or variable names closes the Help box. GETTING STARTED TO EDIT WIN TR-20 INPUT FILE Select one of the first three File pull down choices (New WinTR-20 File, Open Existing WinTR-20 File, and Re-Open Last Session) on the main window. No matter which of the three are selected, the WinTR-20 Identifier entry win­ dow appears. Make sure the proper input unit system (English or metric) is selected. Once the information on the window is completed, ac­ cept the data by clicking the “Accept Changes (Close)” button. The WinTR-20 Identifier Win­ dow will close leaving the main window. Con­ tinue by clicking (selecting) another input section entry window from the list on the main window. To save data entered, use the Save or SaveAs selections on the File pull down. Remember to save early and save often. TO CONVERT OLD TR-20 INPUT FILE – Se­ lect Convert Old Data from the File pull down on the main window. Then select the file name to be converted to start the converter. When the converter run is complete, either the Error File (indicating a problem with converting the data) will displayed or the WinTR-20 Identifier entry ---PAGE BREAK--- A-1-4 2016 Edition window will open for editing the converted data. TO REFORMAT HEC-RAS from the File pull down on the main window. Then select the HEC-RAS output file name to be reformatted. If a WinTR-20 input file is currently loaded, the choice to either add to the current data or start a new file can also be made. After reformatting is complete, either the Error File will be displayed or the WinTR-20 Identifier entry window will open for editing the file containing the reformatted data. To IMPORT NOAA ATLAS 14 DATA – Select Import NOAA Data from the File pull down menu on the main window. Then enter NOAA Atlas text file. Do not try to import NOAA Data into Win­ TR-20 input file if currently loaded, the data will be deleted and substituted with NOAA Atlas data. It is recommended to open a new file to include only NOAA Atlas data. TO RUN WINTR-20 INPUT FILE USING THE EDIT, CONVERT, and/or REFORMAT tech­ niques described above. Select WinTR-20 from the Run pull down on the main window to run WinTR-20 model. When the run is complete either the Error file or WinTR-20 output file will be displayed. (Note: The Run pull down is ONLY available if the current data has a file name (not”>Untitled<”) and the data has not been modified since it was loaded or saved. If Run is not displayed, then save the current data to make the Run pull down visible.) EFH2 PEAK DISCHARGE DETERMINATION A program for determining peak discharge as prescribed by Engineering Field Handbook Chapter 2. Required information includes wa­ tershed characteristics (drainage area, curve number, hydraulic length, watershed slope) and rainfall amount and distribution. This program has restricted applications. May be applied when: •Watershed is accurately represented by a single runoff curve number between 40 and 98. •Watershed area is between 1 and 2,000 acres. •Watershed hydraulic length is between 200 and 26,000 feet. •Average watershed slope is between 0.5 and 64%. •No valley or reservoir routing is required. •Urban land use within the watershed does not exceed 10%. For complete information please visit: http://www.nrcs.usda.gov/wps/portal/nrcs/detail­ ---PAGE BREAK--- A-2-1 2016 Edition APPENDIX A-2 Joining the Equivalent BMP List: Application and Removal Process BACKGROUND AND PURPOSE Pursuant to the Clean Water Act, EPA estab­ lished requirements for storm water discharges under the National Pollutant Discharge Elimina­ tion System (NPDES) permitting program. Geor­ gia’s Environmental Protection Division (EPD) administers three NDPES General Permits that authorize the discharge of storm water from sites where construction activities occur. Each of these permits requires BMPs to be implemented in accordance with the design specifications con­ tained in the Manual for Erosion and Sediment Control (Manual) published by the Georgia Soil and Water Conservation Commission The allowance of the efficient addition of proven BMPs that are at least as stringent as the Manu­ al for Erosion and Sediment Control recognizes the dynamic growth and technological advance­ ments in the area of BMP development. Each of the NPDES General Permits authorizing the discharge of storm water also allows for Alterna­ tive BMPs – BMPs not listed in the Manual – to be used if they meet the following requirement: The use of alternative BMPs whose performance has been documented to be equivalent or su­ perior to conventional BMPs as certified by a Design Professional may be allowed (unless disapproved by EPD or the State Soil and Water Conservation Commission). and EPD have previously developed a guidance document for the use of Alternative BMPs. Specifically, the Design Professional pre­ paring the Erosion, Sedimentation and Pollution Control Plan (ES&PC Plan) for a permittee must sign and certify the following documentation: 1. One page summary detailing why the alter­ native BMP is equivalent or superior to the conventional BMPs found in the Manual. 2. Documented side by side testing (alterna­ tive BMP vs. conventional BMP) using the appropriate design requirements and speci­ fications contained in the Manual. 3. Proof that the alternative BMP was previ­ ously installed and worked under condi­ tions comparable to the environmental conditions of the proposed site. This can be documented with photographs. 4. All specifications including the design re­ quirements and the procedures for proper installation and maintenance. In the year 2015, BMPs not in the Manual may be approved as part of the Alternative BMP pro­ cess described above. Allowing a new mecha­ nism for Alternative BMPs repeatedly used and approved under Guidance to be placed on an Equivalent BMP List would increase ef­ ficiency for all the agencies involved and the development community. This would be similar to the 5th edition of the Manual’s recognition of materials approved by the Georgia Depart­ ment of Transportation (GDOT), which appear on GDOT’s Qualified Products List (QPL). As of January 1, 2016, any product that seeks to be on the GDOT QPL List must first go through the Equivalent BMP process. approval of a BMP however does not ensure GDOT’s adop­ tion of that item into their QPL, design policies or procedures. Therefore, the purpose of this document is to provide a process by which BMPs having dem­ onstrated success in the field at least three times under the Alternative BMP process and having been bench tested may be placed on an Equiva­ lent BMP List. The procedure also includes a mechanism for removing BMPs from the Equiva­ lent BMP list. In addition, the has the discretion to remove a BMP from the Equivalent BMP List at any time. PROCEDURE FOR APPLYING FOR THE EQUIVALENT BMP LIST For a BMP to be considered for inclusion on the Equivalent BMP List, a Design Professional must have successfully completed the current process for Alternative BMPs as outlined by Guidance on at least three completed projects where EPD’s Notice of Termination Form has been filed. Geographic dispersion of the ---PAGE BREAK--- A-2-2 2016 Edition project sites is encouraged. The following steps are required: 1. Provide pre-notice to EPD and of the intent to apply for an Alternative BMP to be included on the Equivalent BMP List as follows: A. Specify on the required checklist that ac­ companies the Notice of Intent Form that the project includes an Alternative BMP that will be included on an Application for the Equivalent BMP List. B. Inform of the intent to apply by sending a digital copy of the approved ES&PC plan and a copy of the above to when each NOI is filed with EPD. 2. Once the project involving the Alternative BMP has been completed and a Notice of Termination Form for the project has been filed, submit to the following: A. An Application to be on the Equivalent BMP List and a sample of the BMP. B. Three sets one for each time the Alter­ native BMP was used in three separate projects of the required documentation to use the Alternative BMP, based on the current approval process as outlined by Guidance. Evidence of repeat­ able bench and field testing must be in­ cluded as part of this documentation. Only approved ASTM standards or Overview Council-approved standards will be accept­ ed for repeatable bench testing; working test methods will not be accepted. C. Three sets one for each time the Alterna­ tive BMP was used in three separate proj­ ects of the Notice of Termination Form for each project involving the Alternative BMP. D. A Certification Form signed by two individu­ als a Level II certified Design Profes­ sional and a Level 1A or Level 1B Certified Personnel who evaluated the BMPs performance in the field stating that the Alternative BMP performed as expected throughout the life of each of the three proj­ ects. E. Three sets of installation photos one for each time the Alternative BMP was used of the Alternative BMP utilized in the three projects. F. Three sets of after-storm event photos one for each time the Alternative BMP was used of the Alternative BMP utilized in the three projects. G. Any post-storm event inspection records as well as inspection and enforcement records made by any federal, state, or local regula­ tory agency related to this specific BMP on this project. The above materials should be submitted to both electronically and with hard cop­ ies to P.O. Box 8024, Athens, Georgia 30603. will provide copies of the materials sub­ mitted to EPD and GDOT upon receipt. will receive and review the information submitted above. has the discretion to approve the application, deny the application, request a resubmittal, or request additional information, with consultation from EPD and GDOT. Appli­ cants will be informed of determina­ tion in writing. Applicants receiving approval for inclusion on the Equivalent BMP List will be notified within 90 days. Applicants with BMPs denied from inclusion on the Equivalent BMP List may seek review of the determination from the State Board. PROCEDURE FOR REMOVING A BMP FROM THE EQUIVALENT BMP LIST Any individual, local government, or agency may submit to a request that the BMP be removed from the Equivalent BMP List. The re­ quest should include a certified statement that the Alternative BMP failed to perform as expected and thus should be removed from the Equivalent BMP List, along with supporting documentation (picture, inspection forms, etc.). The request for removal is encouraged to focus on complaints independent of issues of ordinary installation and maintenance of the BMP. The request should be submitted to both electronically and with hard copies to P.O. Box 8024, Athens, Georgia 30603. will provide copies of the request for removal to EPD and GDOT upon receipt. GSW­ ---PAGE BREAK--- A-2-3 2016 Edition CC will also provide a copy of the request to the individual who initially applied for the Alternative BMP to be included on the Equivalent BMP List. has the discretion to approve the re­ quest, deny the request, request a resubmittal, or request additional information with consultation from EPD and GDOT. An applicant with a BMP removed from the Equivalent BMP List may seek review of the determination from the State Board. An Alternative BMP removed from the Equivalent BMP List may be returned to the list if an appli­ cant successfully completes the Procedure for Applying for the Equivalent BMP List again. TRANSITION PERIOD The Manual for Erosion and Sediment Control in Georgia has been revised and revisions will become effective January 1, 2016. The Equiva­ lent BMP List will first be made available January 1, 2016. BMPs included in the 5th Edition of the Manual and GDOT’s QPL list will be recognized by and included on the Equivalent BMP List. Applications for BMPs to be included on the Equivalent BMP list will be based on NOI’S submitted on or after January 1, 2016. approval of a BMP however does not ensure GDOT’s adoption of that item into their QPL, design policies or procedures. The first update to the Equivalent BMP list will occur on or after March 31, 2016. 1 See NPDES General Permit No. GAR 10001, Authorization To Discharge Under the National Pollutant Discharge Elimination System Storm Water Discharges Associated with Construction Activity For Stand Alone Construction Projects; NPDES General Permit No. GAR 10002, Authori­ zation To Discharge Under the National Pollutant Discharge Elimination System Storm Water Discharges Associated with Construction Activity for Infrastructure Construction Projects; NPDES General Permit No. GAR 10003, Authorization To Discharge Under the National Pollutant Discharge Elimination System Storm Water Discharges Associated with Construction Activity for Common Developments. 2 See Id. at Permit No. GAR100003 (page 24), Permit No. GAR 100002 (page 21), and Permit No. GAR 10001 (page 21). 3 Guidance Document for Alternative BMPs, available at Guidance_Document_Oct_2008.pdf. 4 Ga. Code Ann., § 12-7-3 (10.2) provides: “Manual for Erosion and Sediment Control in Georgia” or “manual” means the published guidance of the commission governing the design and practices to be utilized in the protection of this state’s natural resources from erosion and sedimentation which shall be based foremost upon sound engineering principles and repeatable bench and field testing of structural and vegetative best management practices and which shall have the annual approval of the Erosion and Sediment Control Overview Council established pursuant to Code Section 12-7-7.1. 5 See Notice of Termination, available at 6 State law requires that the design and practices utilized for erosion and sedimentation control must be based on “sound engineering principles and repeatable bench and field testing of structural and vegetative best management practices….” See supra note 5. 7 Ga. Code Ann., § 12-7-19, Education and training certification requirements, provides that: Persons involved in land development design, review, permitting, construction, monitoring, or inspection or any land-disturbing activity shall meet the education and training certification requirements, dependent on his or her level of involvement with the process, as developed by the commission in accordance with this Code section and in consultation with the division and the Stakeholder Advisory Board created pursuant to Code Section 12-7-20. On or after May 14, 2007, for each site on which land-disturbing activity occurs, each entity or person acting as either a primary, secondary, or tertiary permittee, as defined in the state general permit, shall have as a minimum one person who is in responsible charge of erosion and sedi­ mentation control activities on behalf of said entity or person and meets the applicable education or training certification requirements developed by the commission present on site whenever land- disturbing activities are conducted on that site….. 8 The State Soil and Water Conservation Commission is established pursuant to Ga. Code Ann. § 2-6-23, and the Governor appoints one at-large member from each of the five soil and water conservation district regions to serve on the commission. ENDNOTES ---PAGE BREAK--- B-1-1 2016 Edition SOILS INFORMATION AND THE WEB SOIL SURVEY The Web Soil Survey is an interactive, inter­ net based application that contains soil maps and associated attribute data from soil surveys produced by the National Cooperative Soil Sur­ vey. Spatial and attribute data are available on the Web Soil Survey for all Georgia counties that have a completed, correlated soil survey, which includes most, but not all Georgia Counties. A status map of Georgia counties with spatial data available can be found on the Soil Data Mart at http://soildatamart.nrcs.usda.gov/Statusmap. aspx. The URL to access the Web Soil Survey is http://websoilsurvey.nrcs.usda.gov/. The Web Soil Survey Home Page contains guidance on how to use the application, including an explanatory document called “How to Use the Web Soil Survey”. A brief description of the Web Soil Survey, information it contains, and how to use the ap­ plication follows. Additional help can be found by clicking on the question mark throughout the application. Other links to downloadable soils data, archived soil survey publications, and a glossary are at the top of the Web Soil Survey screen. Start the Web Soil Survey Start the Web Soil Survey application by clicking on the big green button that says “Start WSS”. At the top of the page, there are 4 major tabs: Area of Interest (AOI), Soil Map, Soil Data Ex­ plorer, and Shopping Cart (Free). Locate and Designate the Area of Interest (AOI) The first step is to locate and outline the AOI. The AOI options will be displayed when the WSS application is started, but can also be accessed at anytime by clicking on the Area of Interest (AOI) tab. There is an Area of Interest Interactive Map on the right side of the screen, and an AOI can be located by progressively zoom­ ing in to the area on the map using the magnifier tool. Alternatively, quick navigation options are on the left side of the screen. These allow for easy selection of locations using several options, in­ cluding an address, state and county, soil survey area, longitude and latitude, and others. Click on the navigation method of choice, enter the appropriate selections, and click on View. Then use the magnifier tool to zoom in to the specific AOI. One of the two AOI tools is then used to delineate the AOI as a rectangle, or as a multi-sided polygon. Once identified, the AOI will appear as a hatched area within the pre­ scribed boundary. The AOI must be 10,000 acres or smaller in size, unless the entire survey area is selected as an AOI. The AOI can be set to the entire survey area by clicking on Set AOI, rather than View, when using quick navigation. View the Soil Map Once the AOI is defined, the soil map for the area can be displayed by clicking on the “Soil Map” tab. A map with soil lines and soil symbols will be displayed on the right side of the screen. A legend with map symbols, soil map unit names, and the extent of each map unit will be displayed on the left side of the screen. At this point an ADOBE PDF file can be created for download or printing by clicking on the Printable Version bar. Viewing of the map can be switched between a Full Width Map Layout , or a “Normal Map Lay­ out” with legend, by clicking on the layout icons on the top-right portion of the screen. Click on the Legend tab at the top-left por­ tion of the map to open a legend that allows for customized viewing options. Various features, such as streams, roads, cities, and counties can be turned on or off. The background map can also be switched between aerial photography and topographic maps. Explore Soil Data and Interpretations Access information about the soils by click­ ing on the Soil Data Explorer tab. This opens up a subset of folders that includes tabs for Intro to Soils, Suitabilities and Limitations for Use, Soil APPENDIX B-1 ---PAGE BREAK--- B-1-2 2016 Edition Properties and Qualities, Ecological Site Assess­ ment, and Soil Reports. Information on Ecological Site Assessment is not available at this time, but this tab will become active as Ecological Site information is devel­ oped in the future. The Intro to Soils folder contains descrip­ tive information about soils and their use. The Suitabilities and Limitations for Use folder con­ tains land classifications, productivity ratings, and interpretations for urban and recreational uses, forestland, cropland, waste disposal, water management, and other uses. The Soil Proper­ ties and Qualities folder contains information about chemical and physical properties of the soils, water features related to the soils, erosion factors, and other soil qualities and features. The Soil Reports folder provides for grouping of similar items in soil reports, without the graphical display. Information in the Suitabilities and Limitations for Use, and the Soil Properties and Qualities folders, when selected, can be displayed graphi­ cally on the map, as the items listed are related to specific soil components. Click on the Soil Properties and Qualities tab, and a list of selectable groups of soil properties and qualities appears. Click on one of these groups, and specific items appear for selection. For example, select­ ing Soil Erosion Factors will open up selections for K Factor Rock Free, K Factor Whole Soil, T Factor, Wind Erodibility group, and Wind Erodibil­ ity Index. Select K Factor Whole Soil, then View Rating to get a map display of the k factors with an associated legend. At this point an ADOBE .pdf file can be created for download or printing by clicking on the Printable Version bar. There is also an option to create a document with multiple selections. Click on the Add to Shopping Cart bar to add any number of items to a customized report, which will be created at the end of the session. All selected items will have a View Descrip­ tion bar in addition to the View Rating bar. Click on the View Description bar for an explanation of the feature selected. There will also be a View Description option that can be checked to include a detailed description of the feature as part of the generated report. Check Out Click on the Shopping Cart (Free) tab to cre­ ate a customized soil report for any or all of the soil items or reports that were previously select­ ed using the Add to Shopping Cart option. The Report Properties option allows for designation of titles, paper sizes and scales. Selections can be made under the Table of Contents to remove any reports or descriptive materials not needed. Finally, click on the Check Out bar. Choices are to get the report now, or download later. It may be better to download very large files at a later time. An ADOBE PDF file containing customized maps, and selected items about the soils, will be created and made available for download. Most of the information under the Suitabilities and Limitations for Use tab, and the Soil Proper­ ties and Qualities tab, can also be found under the Soil Reports tab. Information from the Soil Reports tab will not be graphically displayed on the map. However, the soil reports offer group­ ings of several related items, rather than the single item displayed from the other tabs. The reports, along with the associated soil map, may be a good option for many applications. Download data There is an option in Web Soil Survey to download the spatial and tabular data for the defined AOI in a format that can be utilized on a local computer in a GIS system, such as Arc­ Map. Once the AOI has been identified, click on the Download Soils Data option at the top of the screen. Select or deselect tabular data, template database, or spatial data to download, enter an email address, and click the Download bar. Pro­ cessing of the request will commence, and when completed, an email will be sent with a link for downloading the requested data. Content of the Web Soil Survey Soil properties, qualities, and interpretations that are currently in the Web Soil Survey under suitabilities, limitations, soil qualities and fea­ tures, and soil reports are listed below. Content of the Web Soil Survey is refreshed periodically with updates and with additional information. ---PAGE BREAK--- B-1-3 2016 Edition Suitabilities and Limitations Ratings in the Web Soil Survey Category Interpretation Building Site of Concrete Building Site of Steel Building Site Development With Basements Building Site Without Basements Building Site Landscaping, and Golf Fairways Building Site Roads and Streets Building Site Excavations Building Site Commercial Buildings Construction Source Construction Source Construction Source Construction Source Disaster Recovery Planning........................Catastrophic Mortality, Large Animal Disposal, Pit Disaster Recovery Planning........................Catastrophic Mortality, Large Animal Disposal, Trench Disaster Recovery Liner Material Source Disaster Recovery Planning........................Composting Facility - Subsurface Disaster Recovery Planning........................Composting Facility - Surface Disaster Recovery Planning........................Composting Medium and Final Cover Disaster Recovery and Debris Disposal, Large-Scale Event Land Classifications Classification (this includes prime farmland and farmland of statewide importance) Land Classifications Rating by mapunit Land Taxonomy Classification Land Limitations for Haul Roads and Log Landings Land Hazard (Off-Road, Off- Trail) Land Hazard (Road, Trail) Land Equipment Operability Land Site Preparation (Deep) Land Site Preparation (Surface) Land for Seedling Mortality Land Rutting Hazard Land for Hand Planting Land for Log Landings Land for Mechanical Planting Land for Roads (Natural Surface) Military Areas Military for Crew-Served Weapon Fighting Positions ---PAGE BREAK--- B-1-4 2016 Edition Military for Individual Fighting Positions Military for Vehicle Fighting Positions Military Landing Zones Military Trafficability Recreational Development Areas Recreational Development and Trails Recreational Development Areas Recreational Development Sanitary Cover for Landfill Sanitary Landfill (Area) Sanitary Landfill (Trench) Sanitary Tank Absorption Fields Sanitary lagoons Vegetative Productivity (Cubic Feet per Acre per Year) Vegetative Productivity (Tree Site Index) Vegetative of Irrigated Crops (Component) Vegetative of Non-Irrigated Crops (Component) Water Dikes, and Levees Water Ponds (Aquifer-Fed) ---PAGE BREAK--- B-1-5 2016 Edition Soil Properties and Qualities in the Web Soil Survey Category Soil Property or Quality Soil Chemical Carbonate (CaCO3) Soil Chemical Properties............................Cation-Exchange Capacity (CEC-7) Soil Chemical Properties............................Effective Cation-Exchange Capacity (ECEC) Soil Chemical Properties............................Electrical Conductivity (EC) Soil Chemical Soil Chemical (1 to 1 Water) Soil Chemical Adsorption Ratio (SAR) Soil Erosion Factors Factor, Rock Free Soil Erosion Factors K Factor, Whole Soil Soil Erosion Factor Soil Erosion Factors Erodibility Group Soil Erosion Factors Erodibility Index Soil Physical Water Capacity Soil Physical Water Supply, 0 to 100 cm Soil Physical Water Supply, 0 to 150 cm Soil Physical Water Supply, 0 to 25 cm Soil Physical Water Supply, 0 to 50 cm Soil Physical Density, 15 Bar Soil Physical Density, One-Tenth Bar Soil Physical Density, One-Third Bar Soil Physical Extensibility Soil Physical Limit Soil Physical Matter Soil Physical Clay Soil Physical Sand Soil Physical Silt Soil Physical Properties..............................Plasticity Index Soil Physical Hydraulic Conductivity (Ksat) Soil Physical Hydraulic Conductivity (Ksat), Standard Classes Soil Physical Texture Soil Physical Content, 15 Bar Soil Physical Content, One-Third Bar Soil Qualities and Group Classification (Surface) Soil Qualities and to a Selected Soil Restrictive Layer Soil Qualities and to Any Soil Restrictive Layer Soil Qualities and Class Soil Qualities and Action Soil Qualities and Days Soil Qualities and Features.........................Hydraulic Soil Group Soil Qualities and Unit Name ---PAGE BREAK--- B-1-6 2016 Edition Soil Qualities and Material Name Soil Qualities and Features........................Representative Slope Soil Qualities and Soil Classification ( Surface) Water to Water Table Water Frequency Class Water Frequency Class Reports in the Web Soil Survey Report Feature AOI Inventory Component unit symbol Component Legend unit name Component percent Component name Component Legend kind Component percent Map Unit Unit Description Map Unit Description Unit Description (Brief) Map Unit Description (Brief, Generated)....Map Unit Description (Brief, Generated) Selected Soil Interpretations.......................Selected Soil Interpretations Selected Survey Area Interpretation Descriptions..........................Selected Survey Area Interpretation Descriptions Survey Area Data area version Survey Area Data area version established date Survey Area Data data version Survey Area Data data NASIS export data Survey Area Data data certification status Building Site Development Dwellings and Small Commercial Buildings........Dwellings without basements Dwellings and Small Commercial Buildings........Dwellings with basements Dwellings and Small Commercial Buildings........Small commercial buildings Construction Materials Source of Roadfill and Topsoi.....................Potential as a source of roadfill Source of Roadfill and Topsoil....................Potential as a source of topsoil Source of Sand and as a source of sand Source of Sand and as a source of gravel ---PAGE BREAK--- B-1-7 2016 Edition Land Classifications Hydric Soils Land Capability Classification.....................Land Capability Classification Prime and other Important Farmlands........Farmland classification Taxonomic Classification of the Soils..........Taxonomic Classification of the Soils Land Management Hazard of Erosion and Suitabilities for Roads on Forestland Hazard of off-road or off-trail erosion Hazard of Erosion and Suitabilities for Roads on ForestlandHazard of erosion on roads and trails Hazard of Erosion and Suitabilities for Roads on ForestlandSuitability for roads (natural surface) Recreational Development Camp Areas, Picnic Areas, and Playgrounds...........Camp areas Camp Areas, Picnic Areas, and Playgrounds...........Picnic areas Camp Areas, Picnic Areas, and Playgrounds...........Playgrounds Paths, Trails, and Golf and trails Paths, Trails, and Golf fairways Sanitary Facilities sanitary landfill sanitary landfill cover for landfill Sewage tank absorption fields Sewage lagoons Soil Chemical Properties Chemical exchange capacity Chemical cation exchange capacity Chemical carbonate Chemical reaction Chemical Chemical Chemical absorption ratio Erosion RUSLE2 Related Attributes.........................hydrologic group RUSLE2 Related RUSLE2 Related factor RUSLE2 Related percent RUSLE2 Related percent RUSLE2 Related percent Soil Physical Properties Engineering texture Engineering classification Engineering classification Engineering > 10 inches ---PAGE BREAK--- B-1-8 2016 Edition Engineering 3-10 inches Engineering passing sieve number 4 Engineering passing sieve number 10 Engineering passing sieve number 40 Engineering passing sieve number 200 Engineering limit Engineering index Particle Size and Coarse Fragments..........Horizon Particle Size and Coarse Fragments..........Depth Particle Size and Coarse Fragments..........Sand percent Particle Size and Coarse Fragments..........Silt percent Particle Size and Coarse Fragments..........Clay percent Particle Size and Coarse Fragments..........Total Fragments Particle Size and Coarse Fragments..........Fragments 2-74 mm Particle Size and Coarse Fragments..........Fragments 75-249 mm Particle Size and Coarse Fragments..........Fragments 250-599 mm Particle Size and Coarse Fragments..........Fragments >=600 mm Soil Qualities and Features Soil Layer Soil Soil Features for frost action Soil of corrosion-Uncoated steel Soil of corrosion-Concrete Vegetative Productivity Forestland trees Forestland Index Forestland of wood fiber Forestland to manage Irrigated Yields by Map Unit Component............Land capability Irrigated Yields by Map Unit Component............Crop yields Nonirrigated Yields by Map Unit Component......Land capability Nonirrigated Yields by Map Unit Component......Crop yields Waste Management Large Animal Carcass Disposal..................Large Animal Carcass Disposal, Pit Large Animal Carcass Disposal..................Large Animal Carcass Disposal, Trench Water Features Water group Water runoff Water table Water Water ---PAGE BREAK--- B-1-9 2016 Edition Water Management Ponds and reservoir areas Ponds and Embankments...........................Embankments, dikes, and levees Index for the Suitabilities and Limitations Tab in the Web Soil Survey Interpretation Category Bivouac Operations Camp Development Catastrophic Mortality, Large Animal Disposal, Pit...............Disaster Recovery Planning Catastrophic Mortality, Large Animal Disposal, Trench .......Disaster Recovery Planning Clay Liner Material Recovery Planning Composting Facility - Recovery Planning Composting Facility - Recovery Planning Composting Medium and Final Recovery Planning Construction Limitations for Haul Roads and Log Landings..Land Management Corrosion of Site Development Corrosion of Site Development Daily Cover for Facilities Dwellings With Basements Development Dwellings Without Site Development Embankments, Dikes, and management Erosion Hazard (Off-Road, Off- Management Erosion Hazard (Road, Management Excavated Ponds management Excavations for Crew-Served Weapon Fighting Positions...Military Operations Excavations for Individual Fighting Positions.......................Military Operations Excavations for Vehicle Fighting Operations Farmland Classification (includes prime farmland and farmland of statewide Classifications Forest Productivity (Cubic Feet per Acre per Year).............Vegetative Productivity Forest Productivity (Tree Site Productivity Gravel Materials Harvest Equipment Management Helicopter Landing Operations Hydric Rating by Classifications Lawns, Landscaping, and Golf Fairways Building.............Site Development Local Roads and Site Development Mechanical Site Preparation Management Mechanical Site Preparation Management Nonirrigated Capability Classifications Nonirrigated Capability Classifications Paths and Development ---PAGE BREAK--- B-1-10 2016 Edition Picnic Development Development Potential for Seedling Mortality...................Land Management Roadfill Materials Rubble and Debris Disposal, Large-Scale Event.....Disaster Recovery Planning Sand Materials Sanitary Landfill Facilities Sanitary Landfill Facilities Septic Tank Absorption Fields....................Sanitary Facilities Sewage Facilities Shallow Site Development Small Commercial Buildings.......................Building Site Development Soil Rutting Management Soil Taxonomy Classification.......................Land Classifications Suitability for Hand Management Suitability for Log Management Suitability for Mechanical Planting Management Suitability for Roads (Natural Surface).......Land Management Topsoil Materials Vehicle Operations Yield of Irrigated Crops (Component).........Vegetative Productivity Yield of Non-Irrigated Crops (Component)..Vegetative Productivity Index for the Soil Properties and Qualities Tab in the Web Soil Survey Item Subcategory AASHTO Group Classification (Surface)....Soil Qualities and Features Available Water Physical Properties Available Water Supply, 0 to 100 Physical Properties Available Water Supply, 0 to 150 Physical Properties Available Water Supply, 0 to 25 Physical Properties Available Water Supply, 0 to 50 Physical Properties Bulk Density, 15 Physical Properties Bulk Density, One-Tenth Physical Properties Bulk Density, One-Third Physical Properties Calcium Carbonate Chemical Properties Cation-Exchange Capacity Chemical Properties Depth to a Selected Soil Restrictive Layer..Soil Qualities and Features Depth to Any Soil Restrictive Layer............Soil Qualities and Features Depth to Water Features Drainage Qualities and Features Effective Cation-Exchange Capacity (ECEC)........Soil Chemical Properties Electrical Conductivity Chemical Properties Flooding Frequency Features Frost Qualities and Features ---PAGE BREAK--- B-1-11 2016 Edition Frost-Free Qualities and Features Chemical Properties Hydraulic Soil Qualities and Features K Factor, Rock Erosion Factors K Factor, Whole Erosion Factors Linear Physical Properties Liquid Physical Properties Map Unit Qualities and Features Organic Physical Properties Parent Material Qualities and Features Percent Physical Properties Percent Physical Properties Percent Physical Properties pH (1 to 1 Chemical Properties Plasticity Physical Properties Ponding Frequency Features Representative Qualities and Features Saturated Hydraulic Conductivity (Ksat).....Soil Physical Properties Saturated Hydraulic Conductivity (Ksat), Standard Classes.......Soil Physical Properties Sodium Adsorption Ratio Chemical Properties Surface Physical Properties T Erosion Factors Unified Soil Classification ( Surface)..........Soil Qualities and Features Water Content, 15 Physical Properties Water Content, One-Third Physical Properties Wind Erodibility Erosion Factors Wind Erodibility Erosion Factors Index for the Soil Reports Tab in the Web Soil Survey Item Report (Category) AASHTO classification...............................Engineering Properties (Soil Physical Properties) Area sanitary (Sanitary Facilities) Calcium Properties (Soil Chemical Properties) Camp Areas, Picnic Areas, and Playgrounds (Recreational Development) Cation exchange Properties (Soil Chemical Properties) Clay Related Attributes (Erosion) Clay Size and Coarse Fragments (Soil Physical Properties) Common Productivity (Vegetative Productivity) Component Legend (AOI Inventory) Component Legend (AOI Inventory) Component Legend (AOI Inventory) Crop Yields by Map Unit Component (Vegetative Productivity) Crop Nonirrigated Yields by Map Unit Component (Vegetative Productivity) Daily cover for (Sanitary Facilities) Size and Coarse Fragments (Soil Physical Properties) ---PAGE BREAK--- B-1-12 2016 Edition Dwellings with and Small Commercial Buildings (Building Site Development) Dwellings without basements.....................Dwellings and Small Commercial Buildings (Building Site Development) Effective cation exchange capacity.............Chemical Properties (Soil Chemical Properties) Embankments, dikes, and levees...............Ponds and Embankments (Water Management) Farmland and other Important Farmlands (Land Classifications) Features (Water Features) Fragments > 10 Properties (Soil Physical Properties) Fragments >=600 Size and Coarse Fragments (Soil Physical Properties) Fragments 250-599 Size and Coarse Fragments (Soil Physical Properties) Fragments 2-74 Size and Coarse Fragments (Soil Physical Properties) Fragments 3-10 Properties (Soil Physical Properties) Fragments 75-249 Size and Coarse Fragments (Soil Physical Properties) Golf Trails, and Golf Fairways (Recreational Development) Properties (Soil Chemical Properties) Hazard of Erosion on roads and trails........Hazard of Erosion and Suitabilities for Roads on Forestland (Land Management) Hazard of off-road or off-trail Erosion...........Hazard of Erosion and Suitabilities for Roads on Forestland (Land Management) Size and Coarse Fragments (Soil Physical Properties) Hydric Soils (Land Classifications) hydrologic Related Attributes (Erosion) Hydrologic Features (Water Features) Related Attributes (Erosion) Land capability...........................Irrigated Yields by Map Unit Component (Vegetative Productivity) Land capability.....................Nonirrigated Yields by Map Unit Component (Vegetative Productivity) Land Capability Classification.....................Land Capability Classification (Land Classifications) Large Animal Carcass Disposal,Pit.............Large Animal Carcass Disposal Waste Management Large Animal Carcass Disposal, Trench.....Large Animal Carcass Disposal Waste Management Liquid Properties (Soil Physical Properties) Map Unit Unit Description (AOI Inventory) Map Unit Description Unit Description (Brief) (AOI Inventory) Map Unit Description(Brief, Generated)....Map Unit Description (Brief, Generated) (AOI Inventory) Map unit Legend (AOI Inventory) Map unit Legend (AOI Inventory) Paths and Trails, and Golf Fairways (Recreational Development) Percent passing sieve number 10..............Engineering Properties (Soil Physical Properties) Percent passing sieve number 200............Engineering Properties (Soil Physical Properties) Percent passing sieve number 4................Engineering Properties (Soil Physical Properties) Percent passing sieve number 40..............Engineering Properties (Soil Physical Properties) Picnic Areas, Picnic Areas, and Playgrounds (Recreational Development) Plasticity Properties (Soil Physical Properties) Playgrounds..................Camp Areas, Picnic Areas, and Playgrounds (Recreational Development) Pond reservoir and Embankments (Water Management) Features (Water Features) Potential as a source of of Sand and Gravel Construction Materials ---PAGE BREAK--- B-1-13 2016 Edition Potential as a source of roadfill..................Source of Roadfill and Topsoil Construction Materials Potential as a source of of Sand and Gravel Construction Materials Potential as a source of topsoil..................Source of Roadfill and Topsoil Construction Materials Potential for frost Features Soil Qualities and Features Restrictive Features Soil Qualities and Features Risk of corrosion-Concrete.........................Soil Features Soil Qualities and Features Risk of corrosion-Uncoated Features Soil Qualities and Features Properties (Soil Chemical Properties) Sand percent Related Attributes (Erosion) Sand Size and Coarse Fragments (Soil Physical Properties) Selected Soil Interpretations.......................Selected Soil Interpretations (AOI Inventory) Selected Survey Area Interpretation Descriptions............Selected Survey Area Interpretation Descriptions (AOI Inventory) Septic tank absorption Disposal (Sanitary Facilities) Sewage Disposal (Sanitary Facilities) Silt Related Attributes (Erosion) Silt Size and Coarse Fragments (Soil Physical Properties) Site Productivity (Vegetative Productivity) Slope Legend (AOI Inventory) Small commercial buildings........................Dwellings and Small Commercial Buildings (Building Site Development) Sodium absorption Properties (Soil Chemical Properties) Soil Properties (Soil Chemical Properties) Features Soil Qualities and Features Suitability for roads (natural surface).........Hazard of Erosion and Suitabilities for Roads on Forestland (Land Management) Surface Features (Water Features) Survey area Area Data Summary (AOI Inventory) Survey area version established date........Survey Area Data Summary (AOI Inventory) T Related Attributes (Erosion) Tabular data certification status..................Survey Area Data Summary (AOI Inventory) Tabular data Area Data Summary (AOI Inventory) Tabular export data Survey Area Data Summary (AOI Inventory) Taxonomic Classification of the Soils.........Taxonomic Classification of the Soils (Land Classifications) Total Size and Coarse Fragments (Soil Physical Properties) Trees to Productivity (Vegetative Productivity) Trench sanitary (Sanitary Facilities) Unified classification...................................Engineering Properties (Soil Physical Properties) USDA Properties (Soil Physical Properties) Volume of wood Productivity (Vegetative Productivity) Water Features (Water Features) ---PAGE BREAK--- B-2-1 2016 Edition Scientific planning for soil erosion reduction re­ quires knowledge of the relations between those factors that cause loss of soil and water and those that help to reduce such losses. The Revised Universal Soil Loss Equation (RUSLE2) is used to estimate the quantity of soil erosion (sheet and rill) caused by water and to design water erosion control systems. The soil loss predicted by the USLE is that of soil moved off the particular slope segment in sheet and rill erosion. Sheet erosion is defined as the removal of layer of soil from the land surface by the action of rainfall and runoff. It is the first stage in water erosion. This is followed by rill erosion. Rills are small, occur in cropland situations, are removed by normal farming operations, and usually do not reoccur in the same place. The RUSLE2 does not predict sediment deposi­ tion or soil erosion caused by gully, streambank, streambed, mass movement, or wind erosion. The RUSLE2 equation is: a = r k l s c p a is the soil loss in tons per acre per year. r is the rainfall factor. The R factor value quanti­ fies the raindrop impact effect. Rainfall energy is directly related to rain intensity. The energy of a rainstorm is a function of the amount of rain and of all the storm’s component intensities. Median raindrop size increases with rain intensity and the terminal velocity of free-falling waterdrops increase with increased dropsize. k is the soil erodibility factor. Some soils erode more readily than others even when all other fac­ tors are the same. l,s is the topographic factor. Both the length,the APPENDIX B-2 Estimating Soil Erosion With the Revised Universal Soil Loss Equation (RUSLE2) steepnesss and shape of the land slope substan­ tially affect the rate of soil erosion by water. Slope length is defined as the distance from the point of origin of overland flow of water to the point where either the slope gradient decreases enough that deposition begins, or the runoff water enters a well-defined channel (terrace channel, concen­ trated flow area, gully, ditch, grass waterway, etc.). It is not the total length or width of the field in most cases. c is the cover and management factor. C is the ratio of soil loss from land with a specified type and amount of cover to the corresponding loss from a clean tilled, continuous fallow site. p is the support practice factor. P is the ratio of soil loss with a specific support practice to the cor­ responding loss with up-and-down slope farming. Soil Loss Tolerance The term “soil loss tolerance”, sometimes called the value, denotes the maximum level of soil erosion that will permit a high level of crop produc­ tivity to be sustained economically and indefinitely. Any cropping and management combination for which the predicted erosion rate is less than the tolerance may be expected to provide satisfactory erosion control. Soil loss tolerances range from 1 to 5 tons/acre/year for soils of the U.S. acre/year Water Erosion Prediction Project (WEPP) The development of a new generation of tech­ nology for predicting water erosion is under way by a USDA team in the Water Erosion Prediction Project (WEPP). Working with other agencies and academic institutions, the goal of the WEPP is a process oriented model or family of models that are ---PAGE BREAK--- B-2-2 2016 Edition conceptually superior to the lumped model RUSLE and are more versatile as to the conditions that can be evaluated. The WEPP technology is expected to replace RUSLE sometime in the future. ---PAGE BREAK--- B-2-3 2016 Edition Appling 350 Atkinson 325 Bacon 350 Baker 375 Baldwin 275 Banks 300 Barrow 275 Bartow 300 Ben Hill 325 Berrien 350 Bibb 300 Bleckley 300 Brantley 375 Brooks 375 Bryan 350 Bulloch 325 Burke 275 Butts 300 Calhoun 375 Camden 400 Candler 300 Carroll 325 Catoosa 275 Charlton 375 Chatham 350 Chattahoochee 350 Chattooga 300 Table B-2.1 - Rainfall-Erosion Index Factor Values County R County R County R Cherokee 300 Clarke 275 Clay 375 Clayton 300 Clinch 350 Cobb 300 Coffee 325 Colquitt 350 Columbia 250 Cook 350 Coweta 325 Crawford 300 Crisp 325 Dade 275 Dawson 275 Decatur 425 DeKalb 300 Dodge 300 Dooly 325 Dougherty 350 Douglas 300 Early 400 Echols 350 Effingham 350 Elbert 250 Emanuel 300 Evans 325 Fannin 275 Fayette 300 Floyd 300 275 Franklin 300 Fulton 300 Gilmer 275 Glascock 250 400 Gordon 300 Grady 400 Greene 250 Gwinnett 300 Habersham 300 Hall 275 Hancock 250 Haralson 325 Harris 325 Hart 275 Heard 325 Henry 300 Houston 300 Irwin 325 Jackson 275 Jasper 275 Jeff Davis 325 Jefferson 275 ---PAGE BREAK--- B-2-4 2016 Edition County R County R County R Jenkins 300 Johnson 300 Jones 275 Lamar 300 Lanier 350 Laurens 300 Lee 350 Liberty 350 Lincoln 250 Long 350 Lowndes 350 Lumpkin 275 McDuffie 250 400 Macon 325 Madison 275 Marion 325 Meriwether 325 Miller 400 Mitchell 375 Monroe 300 Montgomery 300 Morgan 275 Murray 275 Muscogee 325 Newton 300 Oconee 275 Oglethorpe 250 Paulding 300 Peach 300 Pickens 275 Pierce 350 Pike 325 Polk 300 Pulaski 300 Putnam 275 Quitman 375 Rabun 300 Randolph 350 Richmond 250 Rockdale 300 Schley 325 Screven 300 Seminole 425 Spalding 300 Stephens 300 Stewart 350 Sumter 325 Talbot 325 Taliaferro 250 Tattnall 325 Taylor 325 Telfair 325 Terrell 350 Thomas 400 Tift 350 Toombs 325 Towns 300 Treutlen 300 Troup 325 Turner 325 Twiggs 300 Union 300 Upson 325 Walker 275 Walton 275 Ware 350 Warren 250 Washington 275 Wayne 375 Webster 350 Wheeler 300 White 300 Whitfield 275 Wilcox 325 Wilkes 250 Wilkinson 275 Worth 350 ---PAGE BREAK--- C-1 2016 Edition DEFINITION A revetment of loose rock or similar material installed on a cut or fill slope or a channel side slope to protect the slope from erosion. PURPOSE The purpose of the riprap is to provide a pro­ tective, non-erosive cover on a slope. CONDITIONS This standard applies to channels where velocities do not exceed 10 feet per second or to cut or fill slopes where soil conditions, water turbulence and velocity are such that it will not be stable. DESIGN CRITERIA An appropriate geotextile fabric shall be placed between the riprap and soil base. Use NRCS, DOT or the manufacturer’s specifications for type and weight of fabric. The toe of the revetment shall be entrenched in stable channel bottoms for a depth of 1.5 to 3 feet depending on the size of the riprap. Riprap shall extend up the bank to an elevation where vegetation will provide adequate protection. For channels, riprap shall be sized as required by channel velocity at full bank flow. Use Table C-1 and Figure C-1. The filter size is also shown in Table C-1. Riprap shall not be placed on slopes steeper than 1.5 horizontal to 1.0 vertical. The stone should be reasonably well graded within the gradation curves for each size desig­ nated, and any stone gradation, as determined from a field test sample, that lies within these limits shall be acceptable. The designer should establish the size of graded quarry stone required for the project using accept­ able design criteria. Consideration should then be given to using one of the standardized sizes contained in the following tables. APPENDIX C Riprap The thickness of the graded quarry stone layer and the gradation are interrelated. The thickness specified normally will vary form 1.0 to 1.5 times the maximum stone size in the gradation. In high turbulence areas, the layer thickness should be 1.5 times the maximum stone size. In low turbulence areas, the layer thickness can be reduced to the di­ mension of the largest stone in the gradation band. CONSTRUCTION SPECIFICATIONS The channel side slope and the toe excava­ tion shall be prepared to the required lines and grades. Filter material and riprap shall be placed in suc­ cession to the required thicknesses and elevations. Riprap shall be handplaced around structures to prevent damage to the structures. Terminology: Graded Riprap - durable, dense, specifically selected and graded, quarried stone, placed to prevent erosion. Filter Bedding Stone - stone generally less than 6 inches in size, that may be placed under graded riprap stone in a layer or combination of layers, designed and installed in such a manner as to prevent loss of underlying soil or finer materials because of moving water. Surge Stone - a quarry run ungraded, un­ screened material which may or may not have fines. The standard sizes of quarried stone for erosion control specifications may be produced by any suit­ able commercial quarrying method and by the use of any type of sizing device, necessary to produce the desired sizes. Standard sizes of stone for erosion and sediment control are defined by their weight or square sieve openings. In Georgia two stone classification sys­ tems exist: the National Stone Association classification and the Department of Transportation classification system. Each system sepa­ rates the stone sizes into two categories: graded ---PAGE BREAK--- C-2 2016 Edition riprap stone sizes and filter bedding stone sizes. N.S.A. Graded riprap stone sizes are shown in Table C-1. N.S.A. Filter bedding stone sizes are shown in Table C-1 and C-2. D.O.T. Graded riprap stone sizes are shown in Table C-3. D.O.T. Filter bedding stone sizes are shown in Table C-4. Data for stone center waterways are shown in Table C-5 and Figure C-3. 2.5 R-1 1 1/2 3/4 No. 8 FS-1 4.5 R-2 3 1 1/2 1 FS-1 6.5 R-3 6 3 2 FS-2 9.0 R-4 12 6 3 FS-2 11.5 R-5 18 9 5 FS-2 13.0 R-6 24 12 7 FS-3 14.5 R-7 30 15 12 FS-3 Table C-1 Graded Rip-Rap Stone Size Inches Flow Velocity (Sq. Opening) Filter Stone (ft./sec.) N.S.A. No.1 Max. Avg.2 Min. N.S.A. No.1 1 National Stone Association 2 At least 50% of the individual stone particles must be equal or larger than this listed size ---PAGE BREAK--- C-3 2016 Edition Size Inches (Sq. opening) N.S.A. No1 Max. Avg.2 Min.3 FS-1 3/8 #30 mesh #100 mesh FS-2 2 #4 #100 mesh FS-3 6 1/2 2 1/2 #16 1 National Stone Association 2 At least 50% of the individual stone particles must be equal or larger than this listed size 3 85 - 100% of the individual stone particles may be less than listed size Table C-2. Fitter Bedding Stone Size inches (Sq. opening) D.O.T. No.1 Max. Avg. Min. Common Uses Type 3 12 9 5 Creek Banks Pipe Outlets Type 1 24 12 7 Lakes & Shorelines Rivers 1Georgia Department of Transportation Table C-3. Graded Rip-Rap Stone ---PAGE BREAK--- C-4 2016 Edition D.O.T. No.1 Nominal Sizes (inches) 3 2” - 1” 4 1 1/2” - 3/4” 5 1” - 1/2” 6 3/4” - 3/8” 57 1” - No. 4 1 Georgia Department of Transportation Table C-4. Filter Bedding Stone ---PAGE BREAK--- C-5 2016 Edition Figure C-1. - Maximum Stone Size for Riprap Maximum weight of Minimum and maximum range Weight range of stone required (lbs.) in weight of stones (lbs.) 75 percent of stones (lbs.) 150 25 - 150 50 - 150 200 25 - 200 50 - 200 250 25 - 250 50 - 250 400 25 - 400 100 - 400 600 25 - 600 150 - 600 800 25 - 800 200 - 800 1000 50 - 1000 250 - 1000 1300 50 - 1300 325 - 1300 1600 50 - 1600 400 - 1600 2000 75 - 2000 600 - 2000 2700 100 - 2700 800 - 2700 Table C-5. - Gradation of Riprap ---PAGE BREAK--- C-6 2016 Edition Figure C-2. - Determination of Rock Size for Stone Center Waterway ---PAGE BREAK--- C-7 2016 Edition Grade 6 Percent 8 Percent 10 Percent 12 Percent 15 Percent V 8.0 10 8.0 10 8.0 10.0 8.0 10.0 8.0 10.0 D 1.3 1.6 1.1 1.3 1.0 1.2 0.9 1.1 0.8 0.9 Q Top Widths 20 5 5 25 5 6 6 4 30 5 6 7 7 5 35 6 7 8 5 8 6 40 6 7 8 5 9 6 10 7 45 7 8 9 6 10 6 11 7 50 7 9 6 10 7 11 7 12 8 55 8 9 6 11 7 12 8 13 9 60 9 10 7 12 8 13 8 14 9 65 9 11 7 12 9 14 9 16 11 70 10 7 12 8 13 9 15 10 17 11 75 11 7 13 9 14 10 16 10 18 12 80 12 8 14 9 15 10 18 11 19 13 90 13 9 15 10 17 12 20 13 21 15 100 14 10 17 11 19 13 22 14 24 16 110 16 11 19 13 21 14 24 15 26 18 120 17 11 21 14 23 16 26 17 29 20 130 19 12 22 15 25 17 29 18 31 21 140 20 13 24 16 27 18 31 19 33 23 150 22 14 26 17 29 20 33 21 36 24 160 23 15 27 18 31 21 35 22 38 26 170 25 16 29 19 33 22 37 24 40 28 180 26 17 31 20 34 23 39 25 43 29 190 27 18 32 22 36 25 42 26 45 31 200 29 19 34 23 38 26 44 28 47 33 220 32 21 38 25 42 29 48 31 52 38 240 35 23 41 27 46 31 53 33 57 39 260 38 25 44 30 50 34 57 36 62 42 280 40 27 48 32 54 36 61 39 67 45 300 43 29 51 34 57 39 66 42 71 49 Table C-6. - Velocity, Top Width and Depth for Parabolic Stone Center Waterways ---PAGE BREAK--- C-8 2016 Edition Figure C-3 - Waterway with Stone Center ---PAGE BREAK--- D-1 2016 Edition APPENDIX D Model Soil Erosion and Sedimentation Control Ordinance A model ordinance has been developed by the Georgia Soil and Water Conservation Commission and the Georgia EPD for use by officials in municipalities and counties. The model ordinance is intended primarily to provide guidelines for control of urban soil erosion and sediment pollution. It is designed to meet state requirements for establishing programs as required in Act 599, as well as compliance with the NPDES Permits. An LIA must review, revise, or amend its ordinances within twelve months of any amendment to the E&SC Act. The Model Ordinance can be found on the website at www.gaswcc.georgia.gov, under Documents. ---PAGE BREAK--- E-1 2016 Edition acres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 60 x 102 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. rods acres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 047 x 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . hectares acres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 35 x 104 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. ft. acres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 047 x 103 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. meters acres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 562 x 10-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. miles acres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 840 x 103 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. yards acre-feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 356 x 104 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cu. feet acre-feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 259 x 105 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . gallons centimeters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 937 x 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . inches cubic feet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 832 x 10-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cu. meters cubic feet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. 48052. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . gallons cubic feet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 832 x 101 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . liters cubic feet/min. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 247 x 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . gallons/sec. cubic feet/sec. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. 46317 x 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . million gals/day cubic meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 531 x 101 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cu. ft. cubic meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 308. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cu. yards cubic meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 642 x 102 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . gallons cubic yards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 02 x 102 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . gallons cubic yards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. 646 x 102 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . liters feet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 048 x 101 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . centimeters feet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 048 x 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . meters feet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 894 x 10-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . miles feet of water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 335 x 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pounds/sq. in. gallons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 337 x 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cu. feet gallons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 785 x 10-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cu. meters gallons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 951 x 10-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cu. yards gallons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 785. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . liters gallons of water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8. 337. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pounds of water gallons/min. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 228 x 10-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cu. ft/sec. gallons/min. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. 308 x 10-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . liters/sec. grams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 205 x 10-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pounds hectares. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 471. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . acres hectares. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 076 x 105 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. feet inches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 540. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . centimeters kilograms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 2046. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pounds kilograms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 102 x 10-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . tons kilometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 281 x 103 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . feet kilometer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. 214 x 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . miles kilometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 0936 x 103 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . yards liters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 642 x 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . gallons meters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 281. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . feet meters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 094. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . yards miles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. 280 x 103 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . feet miles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 609. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . kilometers miles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 760 x 103 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . yards million gals/day. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 54723. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cu. ft/sec. rods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 65 x 101 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . feet square feet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 296 x 10-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . acres square feet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. 29 x 10-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. meters square meters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 076 x 101 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. ft. square meters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 861 x 10-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. miles square meters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 196. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. yards square miles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. 40 x 102 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . acres square miles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 590. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. kms. square miles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 098 x 106 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. yards square yards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 066 x 10-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . acres square yards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. ft. square yards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8. 361 x 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. meters square yards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 228 x 10-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sq. miles tons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. 0718 x 102 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . kilograms yards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. 144 x 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . meters yards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. 682 x 10-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . miles CONVERSION FACTORS TO CONVERT: MULTIPLY BY: TO OBTAIN: ---PAGE BREAK--- E-2 2016 Edition ---PAGE BREAK--- F-1 2016 Edition GLOSSARY The list of terms that follows is representative of those used by soil scientists, engineers, develop­ ers, conservationist planners, etc. The terms are not necessarily used in the text, nonetheless they are in common use in conservation matters. AASHTO CLASSIFICATION (soil engineer­ ing) - The official classification of soil materials and soil aggregate mixtures for highway construction used by the American Association of State Highway Transportation Officials. ACID SOIL - A soil with a preponderance of hydrogen ions, and probably of aluminum in pro­ portion to hydroxyl ions. Specifically, soil with a pH value less than 7.0. For most practical purposes, a soil with a pH less than 6.6, the values obtained vary greatly with the method used consequently there is no unanimous agreement on what consti­ tutes an acid soil. The term is usually applied to the surface layer or to the root zone unless specified otherwise. ACRE-FOOT - The volume of water that will cover 1 acre to a depth of 1 foot. AGGRADATION - The process of building up a surface by deposition. This is a long-term or geo­ logic trend in sedimentation. ALKALINE SOIL - A soil that has a pH greater than 7.0, particularly above 7.3, throughout most or all of the root zone, although the term is commonly applied to only the surface layer or horizon of a soil. ALLUVIAL - Pertaining to material that is trans­ ported and deposited by running water. ALLUVIAL LAND - Areas of unconsolidated alluvium, generally stratified and varying widely in texture, recently deposited by streams, and subject to frequent flooding. A miscellaneous land type. ALLUVIAL SOILS - An axonal great soil group of soils, developed from transported and recently deposited material (alluvium) characterized by a weak modification (or none) of the original material by soil forming processes. ALLUVIUM - A general term for all detrital ma­ terial deposited or in transit by streams, including gravel, sand, silt, clay, and all variations and mix­ APPENDIX F tures of these. Unless otherwise noted, alluvium is unconsolidated. ANGLE OF REPOSE - Angle between the hori­ zontal and the maximum slope that a soil assumes through natural processes. ANTECEDENT SOIL WATER - Degree of wet­ ness of a soil prior to irrigation or at the beginning of a runoff period, expressed as an index or as total inches soil water. ANTI-SEEP COLLAR - A device constructed around a pipe or other conduit and placed through a dam, levee, or dike for the purpose of reducing seepage losses and piping failures. ANTI-VORTEX DEVICE - A facility placed at the entrance to a pipe conduit structure such as a drop inlet spillway or hood inlet spillway to prevent air from entering the structure when the pipe is flowing full. APRON (soil engineering) - A floor or lining to protect a surface from erosion. An example is the pavement below chutes, spillways, or at the toes of dams. AUXILIARY SPILLWAY - A dam spillway built to carry runoff in excess of that carried by the principal spillway. See Emergency Spillway. BACKFILL - The material used to refill a ditch or other excavation, or the process of doing so. BEDROCK - The solid rock underlying soils and the regolith in depths ranging from zero (where exposed by erosion) to several hundred feet. BEDLOAD - The sediment that moves by sliding, rolling, or bounding on or very near the streambed; sediment moved mainly by tractive or gravitational forces or both but at velocities less than the sur­ rounding flow. BEST MANAGEMENT PRACTICES (BMP) - A collection of structural practices and vegetative measures which, when properly designed, installed and maintained, will provide effective erosion and sedimentation control for all rainfall events up to and including a 25-year, 24-hour rainfall event. ---PAGE BREAK--- F-2 2016 Edition BLINDING MATERIAL - Material placed on top and around a closed drain to improve the flow of water to the drain and to prevent displacement during back-filling of the trench. BLIND INLET - Inlet to a drain in which entrance of water is by percolation rather than open flow channels. BORROW AREA - A source of earth fill material used in the construction of embankments or other earthfill structures. BOTTOM LANDS - A term often used to define lowlands adjacent to streams. BOX-CUT - The initial cut driven in a property where no open side exists, resulting in a highwall on both sides at the cut. BRUSH MATTING A matting of branches placed on badly eroded land to conserve moisture and re­ duce erosion while trees or other vegetative covers are being established. A matting of mesh wire and brush used to retard streambank erosion. CHANNEL - A natural stream that conveys water; a ditch or channel excavated for the flow of water. See Watercourse. CHANNEL IMPROVEMENT - The improvement of the flow characteristics of a channel by clearing, excavation, realignment, lining, or other means in order to increase its capacity. Sometimes used to connote channel stabilization. CHANNEL SLOPE - Natural or excavated sides (banks) of a watercourse. CHANNEL STABILIZATION - Erosion preven­ tion and stabilization of velocity distribution in a channel using jetties, drops, revetments, vegeta­ tion, and other measures. CHANNEL STORAGE - Water temporarily stored in channels while enroute to an outlet. COLLOID - In soil, organic or inorganic matter having very small particle size and a correspond­ ingly large surface area per unit of mass. Most colloidal particles are too small to be seen with the ordinary compound microscope. COMPACTION - In soil engineering, the process by which the silt grains are rearranged to decrease void space and bring them into closer contact with one another, thereby increasing the weight of solid material per cubic foot. CONDUIT - Any channel intended for the con­ veyance of water, whether open or closed. CONSERVATION - The protection, improve­ ment, and use of natural resources according to principles that will assure their highest economic or social benefits. CONSERVATION DISTRICT - A public organiza­ tion created under state enabling law as a special purpose district to develop and carry out a program of soil, water, and related resource conservation, use, and development within its boundaries, usu­ ally a subdivision of state government with a local governing body. Often called a soil conservation district or a soil and water conservation district. CONTOUR An imaginary line on the surface of the earth connecting points of the same elevation. A line drawn on a map connecting points of the same elevation. COVER CROP - A close-growing crop grown primarily for the purpose of protecting and improv­ ing soil between periods of permanent vegetation. CRADLE - A device, usually concrete, used to support a pipe conduit or barrel. CREEP (SOIL) - Slow mass movement of soil and soil material down relatively steep slopes, pri­ marily under the influence of gravity but facilitated by saturation with water and by alternate freezing and thawing. CRITICAL AREA - A severely eroded sediment producing area that requires special management to establish and maintain vegetation to stabilize soil conditions. CUT - A portion of land surface or area from which earth has been removed or will be removed by excavation; the depth below the original ground surface to the excavated surface. Syn. Excavation. CUT-AND-FILL - Process of earth moving by excavating part of an area and using the excavated material for adjacent embankments or fill areas. ---PAGE BREAK--- F-3 2016 Edition CUTOFF - A wall, collar or other structure, such as a trench, filled with relatively impervious mate­ rial intended to reduce seepage of water through porous strata. DAM - A barrier to confine or raise water for storage or diversion, to create a hydraulic head, to prevent gully erosion, or for retention or soil, rock, or other debris. DEBRIS - The loose material arising from the disintegration of rocks and vegetative material; transportable by streams, ice or floods. DEBRIS DAM - A barrier built across a stream channel to retain rock, sand, gravel, silt, or other material. DEBRIS GUARD - A screen or grate at the intake of a channel, drainage, or pump structure for the purpose of stopping debris. DEGRADATION - To wear down by erosion, especially through stream action. DESIGN HIGHWATER - The elevation of the water surface as determined by the flow conditions of the design floods. DESIGN LIFE - The period of time for which a facility is expected to perform its intended function. DESILTING AREA - An area of grass, shrubs, or other vegetation used for inducing deposition of silt and other debris from flowing water; located above a stock tank, pond, field, or other area need­ ing protection from sediment accumulation. See Filter Strip. DETENTION DAM - A dam constructed for the purpose of temporary storage of streamflow or surface runoff and for releasing the stored water at controlled rates. DIKE (engineering) - An embankment to con­ fine or control water, especially one built along the banks of a river to prevent overflow of lowlands; a levee. (geology) A tabular body of igneous rock that cuts across the structure of adjacent rocks or cuts massive rocks. DISCHARGE (hydraulics) - Rate of flow, specifi­ cally fluid flow; a volume of fluid passing a point per unit time, commonly expressed as cubic feet per second, million gallons per day, gallons per minute, or cubic meters per second. DISCHARGE COEFFICIENT (hydraulics) - The ratio of actual rate of flow to the theoretical rate of flow through orifices, weirs, or other hydraulic structures. DISCHARGE FORMULA (hydraulics) - A for­ mula to calculate rate of flow of fluid in a conduit or through an opening. For steady flow discharge, Q = AV, wherein Q is rate of flow, A is cross-sectional area and V is mean velocity. Common units are cubic feet per second, square feet, and feet per second, respectively. To calculate the mean veloc­ ity, V for uniform flow in pipes or open channels see Manning’s Formula. DISPERSION, SOIL - The breaking down of soil aggregates into individual particles, resulting in single-grain structure. Ease of dispersion is an important factor influencing the erodibility of soils. Generally speaking, the more easily dispersed the soil, the more erodible it is. DIVERSION - A channel with or without a sup­ porting ridge on the lower side constructed across the top or bottom of a slope for the purpose of intercepting surface runoff. DIVERISION DAM - A barrier built to divert part or all of the water from a stream into a different course. DRAIN A buried pipe or other conduit (closed drain). A ditch (open drain) for carrying off surplus surface water of groundwater. To provide channels, such as open ditches or closed drains, so that excess water can be removed by surface flow or by internal flow. To lose water (from the soil) by percolation. DRAINAGE The removal of excess surface water or ground-water from land by means of sur­ face or subsurface drains. Soil characteristics that affect natural drain­ age. DRAINAGE, SOIL - As a natural condition of the soil, soil drainage refers to the frequency and dura­ ---PAGE BREAK--- F-4 2016 Edition tion of periods when the soil is free of saturation; for example, in well-drained soils the water is removed readily but not rapidly; in poorly drained soils the root zone is waterlogged for long periods unless artificially drained, and the roots of ordinary crop plants cannot get enough oxygen: in excessively drained soils the water is removed so completely that most crop plants suffer from lack of water. Strictly speaking, excessively drained soils are a result of excessive runoff due to steep slopes or low available water holding capacity due to small amounts of silt and clay in the soil material. The fol­ lowing classes are used to describe soil drainage: Well drained - excess water drains away rapidly and no mottling occurs within 36 inches of the surface. Moderately well drained - water is removed from the soil somewhat slowly, resulting in small but significant periods of wetness. Mottling occurs between 8 and 18 inches. Somewhat poorly drained - water is removed from the soil slowly enough to keep it wet for signifi­ cant periods but not all of the time. Mottling occurs between 0 to 18 inches. Poorly drained - water is removed so slowly that the soil is wet for a large part of the time. Mottling occurs between 0 to 8 inches. Very poorly drained - water is removed so slowly that the water table remains at or near the surface for the greater part of the time. There may also be periods of surface ponding. The soil has a black to gray surface layer with mottles up to the surface. DRAWDOWN - Lowering of the water surface (in open channel flow), water table, or piezomet­ ric surface (in groundwater flow) resulting from a withdrawal of water. DROP-INLET SPILLWAY - An overfall structure in which the water drops through a vertical riser connected to a discharge conduit. DROP SPILLWAY - An overfall structure in which the water drops over a vertical wall onto an apron at a lower elevation. DROP STRUCTURE - A structure for dropping water to a lower level and dissipating its surplus energy; a fall. A drop may be vertical or inclined. EARTH DAM - Dam constructed of compacted soil material. EMBANKMENT - A man-made deposit of soil, rock, or other material used to form an impound­ ment. EMERGENCY SPILLWAY - A spillway used to carry runoff exceeding a given design flood. Syn. Auxiliary Spillway. ENERGY DISSIPATOR - A device used to re­ duce the energy of flowing water. ERODIBLE (geology and soils) - Susceptible to erosion. EROSION The wearing away of the land surface by running water, wind, ice or other geologi­ cal agents, including such processes as gravitational creep. Detachment and movement of soil or rock fragments by water, wind, ice, or gravity. The following terms are used to describe different types of water erosion: ACCELERATED EROSION - Erosion much more rapid than normal, or geologic erosion, pri­ marily as a result of the influence of the activities of man, or in some cases, of other animals or natural catastrophes that expose base surfaces, for example, fires. GEOLOGIC EROSION - The normal or natural erosion caused by geological processes acting over long geologic periods and resulting in the wearing away of mountains, the building up of floodplains, coastal plains, etc. See Natural Erosion. GULLY EROSION - The erosion process whereby water accumulates in narrow channels and, over short periods, removes the soil from this narrow area to considerable depths, ranging from 1 to 2 feet to as much as 75 to 100 feet. NATURAL EROSION - Wearing away of the earth’s surface by water, ice, or other natural agents under natural environmental conditions of climate, vegetation, etc., undisturbed by man. See Geological Erosion. NORMAL EROSION - The gradual erosion of land used by man which does not greatly exceed natural erosion. See Natural Erosion. RILL EROSION - An erosion process in which numerous small channels only several inches deep ---PAGE BREAK--- F-5 2016 Edition are formed; occurs mainly on recently disturbed and exposed soils. See Rill. SHEET EROSION - The removal of fairly uniform layer of soil from the land surface by runoff water. SPLASH EROSION - The spattering of small soil particles caused by the impact of raindrops on wet soils. The loosened and spattered particles may or may not be subsequently removed by surface runoff. EROSION AND SEDIMENTATION CONTROL PLAN - A plan for the control of erosion and sedi­ ment resulting from a land-disturbing activity. EROSION CLASSES (soil survey) - A grouping of erosion conditions based on the degree of ero­ sion or on characteristic patterns; applied to accel­ erated erosion, not to normal, natural, or geological erosion. Four erosion classes are recognized for water erosion and three for wind erosion. EROSION INDEX - An interaction term of kinetic energy times maximum 30-minute rainfall intensity that reflects the combined potential of raindrop im­ pact and turbulence of runoff to transport dislodged soil particles from a field. EROSIVE - Having sufficient velocity to cause erosion; refers to wind or water. Not to be confused with erodible as a quality of soil. ESCARPMENT - A steep face or ridge of high­ land; the scarpenet of a mountain range is generally on that side nearest the sea. EXISTING GRADE - The vertical location of the existing ground surface prior to cutting or filling. FERTILIZER - Any organic or inorganic material of natural or origin that is added to a soil to supply elements essential to plant growth. FERTILIZER ANALYSIS - The percentage composition of fertilizer, expressed in terms of ni­ trogen, phosphoric acid, and potash. For example, a fertilizer with a 6-12-6 analysis contains 6 percent nitrogen 12 percent available phosphoric acid (P205) and 6 percent water-soluble potash (K2O). Minor elements may also be included. Recent analysis expresses the percentages in terms of the elemental fertilizer (nitrogen, phosphorus, potassium). FILLING - The placement of any soil or other solid material either organic or inorganic on a natu­ ral ground surface or an excavation. FILTER STRIP - A long, narrow vegetative planting used to retard or collect sediment for the protection of diversions, drainage basins or other structures. FINAL CUT - The last cut or line of excavation made when mining a specific property or area. FINISHED GRADE - The final grade or elevation of the ground surface forming proposed design. FLOOD - An overflow or inundation that comes from a river or other body of water and causes or threatens damage. FLOOD CONTROL - Methods or facilities for reducing flood flows. FLOOD CONTROL PROJECT - A structural system installed for protection of land and improve­ ments from floods by the construction of dikes, river embankments, channels, or dams. FLOODGATE - A gate placed in a channel or closed conduit to keep out floodwater or tidal backwater. FLOODPEAK - The highest value of the stage or discharge attained by a flood. The peak stage or peak discharge. FLOODPLAIN - Nearly level land situated on either side of a channel which is subject to overflow flooding. FLOODROUTING - Determining the changes in the rise and fall of floodwater as it proceeds through a valley or reservoir. FLOOD STAGE - The stage at which overflow of the natural banks of a stream begins to cause dam­ age in the reach in which the elevation is measured. FLOODWATER RETARDING STRUCTURE - A structure providing for temporary storage and controlled release of floodwater. FLOODWAY - A channel, either natural, exca­ vated, or bounded by dikes and levees, used to carry excessive flood flows to reduce flooding; sometimes considered to be the transitional area between the active channel and the floodplain. FLUME - A device constructed to convey water on steep grades lined with erosion resistant ma­ terials. ---PAGE BREAK--- F-6 2016 Edition FRAGIPAN - A natural subsurface horizon with high bulk density relative to the solum above, seem­ ingly cemented when dry but showing a moderate to weak brittleness when moist. The layer is low in organic matter, mottled, slowly or very slowly permeable to water, and usually shows occasional or frequent bleached cracks forming polygons. It may be found in profiles of either cultivated or virgin soils but not in calcareous material. FREEBOARD (hydraulics) - Vertical distance between the maximum water surface elevation an­ ticipated in design and the top of retaining banks or structures provided to prevent overtopping because of unforeseen conditions. GAGE OR GAUGE - Device for registering pre­ cipitation, water level, discharge, velocity, pressure, temperature, etc. GAGING STATION - A selected section of a stream channel equipped with a gage, recorder, or other facilities for determining stream discharge. GEOTEXTILE - A term used to describe woven or non-woven fabric materials used to reinforce or separate soil and other materials. GRADATION (geology) - The bringing of a surface or a streambed to grade by running water. As used in connection with sedimentation and fragmental products for engineering evaluation, the term gradation refers to the frequency distribution of the various sized grains that constitute a sedi­ ment, soil, or material. GRADE The slope of a road, channel, or natural ground. The finished surface of a canal bed, road­ bed, top of embankment, or bottom of excavation; any surface prepared for the support of construction like paving or laying a conduit. To finish the surface of canal bed, roadbed, top of embankment, or bottom of excava­ tion. GRADED STREAM - A stream in which, over a period of years, the slope is delicately adjusted to provide, with available discharge and with pre­ vailing channel characteristics, just the velocity required for transportation of the load (of sediment) supplied from the drainage basin. The graded pro­ file is a slope of transportation. It is a phenomenon in which the element of time has a restricted con­ notation. Works of man are limited to his experience and of design and construction. GRADE STABILIZATION STRUCTURE - A structure for the purpose of stabilizing the grade of a gully or other watercourse, thereby preventing fur­ ther head-cutting or lowering of the channel grade. GRADIENT - Change of elevation, velocity, pres­ sure, or other characteristics per unit length; slope. GRADING - Altering surfaces to specified el­ evations, dimensions, and/or slopes; this includes stripping, cutting, filling, stockpiling and shaping or any combination thereof and shall include the land in its cut or filled condition. GRASS - A member of the botanical family Gramineae, characterized by bladelike leaves ar­ ranged on the culm or stem in two ranks. GRASSED WATERWAY - A natural or construct­ ed waterway, usually broad and shallow, covered with erosion-resistant grasses, used to conduct surface water from cropland. GULLY - A channel or miniature valley cut by concentrated runoff but through which water com­ monly flows only during and immediately after heavy rains or during the melting of snow. A gully may be dendritic, or branching, or it may be linear; rather long, narrow, and of uniform width. The distinction between gully and rill is one of depth. A gully is sufficiently deep that it would not be obliter­ ated by normal tillage operations, whereas a rill is of lesser depth and would be smoothed by use of ordinary tillage equipment. See Erosion, Rill. GULLY EROSION - See Erosion. GULLY CONTROL PLANTINGS - The planting of forage, legume, or woody plant seeds, seedlings, cuttings, or transplants in gullies to establish or re- establish a vegetative cover adequate to control runoff and erosion and incidentally produce useful products. HABITAT - The environment in which the life needs of a plant or animal organism, population or community are supplied. HEAD (hydraulics) The height of water above any plane of ---PAGE BREAK--- F-7 2016 Edition reference. The energy, either kinetic or potential, pos­ sessed by each unit weight of a liquid, ex­ pressed as the vertical height through which a unit weight would have to fall to release the average energy possessed; used in various compound terms such as pressure head, velocity head, and lost head. The internal pressure expressed in “feet” or pounds per square inch of an enclosed conduit. HEAD GATE - Water control structure; the gate at the entrance to a conduit. HEAD LOSS - Energy loss due to friction, ed­ dies, changes in velocity, or direction of flow. Syn. friction-head. HEADWATER The source of stream. The water upstream from a structure or point on a stream. HOOD INLET - Entrance to a closed conduit that has been shaped to induce full flow at minimum water surface elevation. HYDROGRAPH - A graph showing variation in stage (depth) or discharge of a stream of water over a period of time. IMPOUNDMENT - Generally an artificial collec­ tion or storage of water, as a reservoir, pit, dugout, sump, etc. Syn. reservoir. INFILTRATION - The gradual downward flow of water from the surface through soil to ground water and water table reservoirs. INFILTRATION RATE - A soil characteristic de­ termining or describing the maximum rate at which water can enter the soil under specified conditions, including the presence of an excess of water. INLET (hydraulics) A surface connection to a closed drain. A structure at the diversion end of a conduit. The upstream end of any structure through which water may flow. INOCULATION - The process of introducing pure or mixed cultures or micro-organisms into natural or artificial cultural media. INTAKE The headworks of a conduit, the place of diversion. Entry of water into soil. See Infiltration. INTAKE RATE - The rate of entry of water into soil. See Infiltration Rate. INTENSITY - Rainfall rate usually in/hr. INTERCEPTION (hydraulics) - The process by which precipitation is caught and held by foliage, twigs, and branches of trees, shrubs, and other vegetation. Often used for “interception loss” or the amount of water evaporated from the precipitation intercepted. INTERCEPTION CHANNEL - A channel exca­ vated at the top of earth cuts, at the foot of slopes or at other critical places to intercept surface flow; a catch drain. Syn. Interception Ditches of water. INLET (hydraulics) A surface connection to a closed drain. A structure at the diversion end of a conduit. The upstream end of any structure through which water may flow. INOCULATION - The process of introducing pure or mixed cultures or micro-organisms into natural or artificial cultural media. INTAKE The headworks of a conduit, the place of diversion. Entry of water into soil. See Infiltration. INTAKE RATE - The rate of entry of water into soil. See Infiltration Rate. INTENSITY - Rainfall rate usually in/hr. INTERCEPTION (hydraulics) - The process by which precipitation is caught and held by foliage, twigs, and branches of trees, shrubs, and other vegetation. Often used for “interception loss” or the amount of water evaporated from the precipitation ---PAGE BREAK--- F-8 2016 Edition intercepted. INTERCEPTION CHANNEL - A channel exca­ vated at the top of earth cuts, at the foot of slopes or at other critical places to intercept surface flow; a catch drain. Syn. Interception Ditch. INTERCEPTOR DRAIN - Surface or subsurface drain, or a combination of both, designed and in­ stalled to intercept flowing water. INTERFLOW - That portion of rainfall that infil­ trates into the soil and moves laterally through the upper soil horizons until intercepted by a stream channel or until it returns to the surface at some point downslope from its point of infiltration. INTERMITTENT STREAM - A stream or por­ tion of a stream that flows only in direct response to precipitation. It receives little or no water from springs and no long-continued supply from melting snow or other sources. It is dry for a large part of the year, ordinarily more than 3 months. INTERNAL SOIL DRAINAGE - The downward movement of water through the soil profile. The rate of movement is determined by the texture, structure, and other characteristics of the soil pro­ file and underlying layers and by the height of the water table, either permanent or perched. Relative terms for expressing internal drainage are: none, very slow, slow, medium, rapid, and very rapid. LAND - The total natural and cultural environ­ ment within which production takes place; a broad­ er term than soil. In addition to soil, its attributes include other physical conditions, such as mineral deposits, climate, and water supply; location in rela­ tion to centers of commerce, population, and other land; the size of the individual tracts or holdings; and existing plant cover, works of improvement, and the like. Some use the terms loosely in other senses: as defined above but without the economic or cultural criteria; especially in the expression “natural land” as a synonym for “soil”; for the solid surface of the earth; and also for earthy surface formations, especially in the geomorphological expression “land form”. LAND CAPABILITY - The suitability of land for use without permanent damage. Land capability, as ordinarily used in the United States, is an ex­ pression of the effect of physical land conditions, including climate, on the total suitability for use without damage for crops that require regular till­ age, for grazing, for woodland, and for wildlife. Land capability involves consideration of the risks of land damage from erosion and other causes and the difficulties in land use owing to physical land characteristics, including climate. LAND CAPABILITY CLASSIFICATION - A grouping of kinds of soils into special units, sub­ classes, and classes according to their capability for intensive use and the treatments required for sustained use. (Prepared by the Natural Resources Conservation Service, USDA.) LAND CAPABILITY MAP - A map showing land capability units, subclasses and classes, or a soil survey map colored to show land capability classes. LAND CAPABILITY UNIT - Capability units provide more specific and detailed information for application to specific fields on a farm or ranch than the subclass of the land capability classification. A capability unit is group of soils that are nearly alike in suitability for plant growth and responses to the same kinds of soil management. LAND CLASSIFICATION - The arrangement of land units into various categories based on the properties of the land or its suitability for some particular purpose. LAND-DISTURBING ACTIVITY - Any land change which may result in soil erosion from water or wind and the movement of sediments into State water or onto lands within the State, including, but not limited to, clearing, dredging, grading, excavat­ ing, transporting and filling of land. LAND FORM - A discernible natural landscape, such as a floodplain, stream terrace, plateau, val­ ley, etc. LAND RECLAMATION - Making land capable of more intensive use by changing its general character, as by drainage of excessively wet land; irrigation of arid or semiarid land; or recovery of submerged land from seas, lakes, and rivers. Large-scale reclamation projects usually are car­ ried out through collective effort. Simple improve­ ments, such as cleaning of stumps or stones from land, should not be referred to as land reclamation. LEACHING - The removal from the soil in solu­ tion of the more soluble materials by percolating waters. ---PAGE BREAK--- F-9 2016 Edition LEGUME - A member of the legume or pulse family, Leguminosae. One of the most important and widely distributed plant families. The fruit is a “legume” or pod that opens along two sutures when ripe. Flowers are usually papilionaceous Leaves are alternate, have stipules, and are usually compound. Includes many valuable food and forage species, such as the peas, beans, peanuts, clover, alfalfas, sweet clovers, lespede­ zas, vetches, and kudzu. Practically all legumes are nitrogen-fixing plants. LEVEL SPREADER - A shallow channel exca­ vation at the outlet end of a diversion with a level section for the purpose of diffusing the diversion out-flow. LIME - Lime, from the strictly chemical stand­ point, refers to only one compound, calcium oxid (CaO); however, the term “lime” is commonly used in agriculture to include a great variety of materi­ als which are usually composed of the oxide, hy­ droxide, or carbonate of calcium or of calcium and magnesium. The most commonly used forms of agriculture lime are ground limestone (carbonates), hydrated lime (hydroxides), burnt lime (oxides), marl, and oyster shells. LIME, AGRICULTURAL - A soil amendment consisting principally of calcium carbonate, but including magnesium carbonate and perhaps other materials, used to furnish calcium and magnesium as essential elements for the growth of plants and to neutralize soil acidity. LIMING - The application of lime to land, primar­ ily to reduce soil acidity and supply calcium for plant growth. Dolomitic limestone supplies both calcium and magnesium. It may also improve soil structure, organic matter content, and nitrogen content of the soil by encouraging the growth of legumes and soil microorganisms. Liming an acid soil to pH value of about 6.5 is desirable for maintaining a high degree of availability of most of the nutrient elements re­ quired by plants. LIQUEFICATION (spontaneous liquefica­ tion) - The sudden large decrease of the shearing resistance of a cohesionless soil, caused by a collapse of the structure from shock or other type of strain and associated with a sudden but tempo­ rary increase in the pore-fluid pressure. It involves a temporary transformation of the material into a fluid mass. LIQUID LIMIT (LL) - The water content corre­ sponding to the arbitrary limit between the liquid and plastic states of consistency of a soil. LITTER - In forestry, a surface layer of loose organic debris in forests, consisting of freshly fallen or decomposed organic materials. LOAMY - Intermediate in texture and proper­ ties between fine-textured and coarse-textured materials. LOOSE ROCK DAM - A dam built of rock without the use of mortar, a rubble dam. See Rock-Fill Dam. MADE LAND - Areas filled with earth or earth and trash mixed, usually made by or under the control of man. A miscellaneous land type. MANNING’S FORMULA (hydraulics) - A for­ mula used to predict the velocity of water flow in an open channel or pipelines: V = 1.486r2/3 S1/2 n wherein V is the mean velocity of flow in feet per second; r is the hydraulic radius; s is the slope of the energy gradient or for assumed uniform flow the slope of the channel in feet per foot; and n is the roughness coefficient or retardance factor of the channel lining. MEAN DEPTH (hydraulics) - Average depth; cross-sectional area of a stream or channel divided by its surface or top width. MEAN VELOCITY - Average velocity obtained by dividing the flow rate discharge by the cross- sectional area for that given cross-section. MEASURING WEIR - A shaped notch through which water flows are measured. Common shapes are rectangular, trapezoidal, and triangular. MECHANICAL ANALYSIS - The analytical procedure by which soil particles are separated to determine the particle size distribution. MECHANICAL PRACTICES - Soil and water conservation practices that primarily change the surface of the land or that store, convey, regulate, or dispose of runoff water without excessive ero­ sion. See Structural Practices. MONOLITHIC - Of or pertaining to a structure formed from a single mass of stone. MOUNTAIN TOP REMOVAL - A mining method in which 100 percent of the overburden covering ---PAGE BREAK--- F-10 2016 Edition a mineral deposit is removed in order to recover 100 percent of the mineral. Excess spoil material is hauled to a nearby hollow to create valley fill. MOVEABLE DAM - A moveable barrier that may be opened in whole or in part, permitting control of the flow of water through or over the dam. MUCK SOIL An organic soil in which the organic matter is well decomposed (USA usage). A soil containing 20 to 50 percent organic matter. MULCH - A natural or artificial layer of plant residue or other materials, such as sand or paper, on the soil surface. NATURAL GROUND SURFACE - The ground surface in its original state before any grading, excavation or filling. NOISE POLLUTION - The persistent intrusion of noise into the environment at a level that may be injurious to human health. NORMAL DEPTH - Depth of flow in an open conduit during uniform flow for the given conditions. See Uniform Flow. OPEN DRAIN - Natural watercourse or con­ structed open channel that conveys drainage water. OUTFALL - Point where water flows from a conduit, stream, or drain. OUTLET - Point of water disposal from a stream, river, lake, tidewater, or artificial dam. OUTLET CHANNEL - A waterway constructed or altered primarily to carry water from man-made structures, such as terraces, tile lines, and diver­ sions. OVERFALL - Abrupt change in stream channel elevation; the part of a dam or weir over which the water flows. OVERHAUL - Transportation of excavated material beyond a specified haul limit, usually ex­ pressed in cubic yard stations (1 cubic yard hauled 100 feet). PARENT MATERIAL (soils) - The unconsoli­ dated, more or less chemically weathered, mineral or organic matter from which the solum of soils has developed by pedogenic processes. The C horizon may or may not consist of materials similar to those from which the A and B horizons developed. PEAK DISCHARGE - The maximum instan­ taneous flow from a given storm condition at a specific location. PERCOLATION - The downward movement of water through soil, especially the downward flow of water in saturated or nearly saturated soil at hydraulic gradients of the order of 1.0 of less. PERMEABILITY - Capacity for transmitting a fluid. It is measured by the rate at which a fluid of standard viscosity can move through material in a given interval of time under a given hydraulic gradient. PERMEABILITY, soil - The quality of soil hori­ zon that enables water or air to move through it. The permeability of a soil may be limited by the presence of one nearly impermeable horizon even though the others are permeable. pH - A numerical measure of the acidity or hy­ drogen ion activity. The neutral point is pH 7.0. All pH values below 7.0 are acid and all above are alkaline. PIPE DROP - A circular conduit used to convey water down steep grades. PLASTICITY INDEX (PI) - The numerical differ­ ence between the liquid limit and the plastic limit. PLASTIC LIMIT (PL) - The water content cor­ responding to an arbitrary limit between the plastic and semisolid states of consistency of soil. PLASTIC SOIL - A soil capable of being molded or deformed continuously and permanently by relatively moderate pressure. PLUNGE POOL - A device used to dissipate the energy of flowing water that may be constructed or made by the action of flowing. These facilities may be protected by various lining materials. POOLS - Areas of a stream where the velocity provides a favorable habitat for plankton. Silts and other loose materials that settle to the bottom of pools are favorable for burrowing forms of benthos. Syn. riffle. PRINCIPAL SPILLWAY - A water conveying device generally constructed of permanent mate­ rial and designed to regulate the normal water level, provide flood protection and/or reduce the frequency of operation of the emergency spillway. ---PAGE BREAK--- F-11 2016 Edition PURE LIVE SEED (PLS) - A term used to ex­ press the quality of seed, even if it is not shown on the label. Expressed as a percentage of the seeds that are pure and will germinate. Determined by multiplying the percent of pure seed times the percents of germination and dividing by 100. RATIONAL FORMULA - Q = CIA. Where is the peak discharge measured in cubic feet per second, is the runoff coefficient reflecting the ratio of runoff to rainfall, is the rainfall intensity for the duration of the storm measured in inches per hour, and is the area contributing drainage measured in acres. RELIEF DRAIN - A drain designed to remove water from the soil in order to lower the water table and reduce hydrostatic pressure. RELIEF WELL - Well, pit, or bore penetrating the water table to relieve hydrostatic pressure by allowing flow from the aquifer. RESTORATION - The process of restoring site conditions as they were before the land distur­ bance. RETURN FLOW - That portion of the water di­ verted from a stream that finds its way back to the stream channel either as surface or underground flow. RILL - A small intermittent watercourse with steep sides, usually only a few inches deep and thus no obstacle to tillage operations. RILL EROSION - See Erosion. RIPRAP - Broken rock, cobbles, or boulders place on earth surfaces, such as the face of a dam or the bank of a stream for protection against the action of water (waves); also applied to brush or pole mattresses, or brush and stone, or other similar materials used for soil erosion control. RISER - The inlet portions of drop inlet spillway that extend vertically from the pipe conduit barrel to the water surface. RIVER BASIN - A major water resource region. The United States has been divided into 20 river basin areas. ROCK-FILL DAM - A dam composed of loose rock usually dumped in place, often with the up­ stream part constructed of handplaced or derrick- placed rock and faced with rolled earth or with an impervious surface of concrete, timber, or steel. RUNOFF (hydraulics) - That portion of the precipitation on a drainage area that is discharged from the area in stream channels. Types include runoff, groundwater runoff, or seepage. SCARIFY - To abrade, scratch, or modify the surface; for example, to scratch the impervious seed coat of hard seed or to break the surface of the soil with a narrow-bladed implement. SCREENING - The use of any vegetative plant­ ing, fencing, ornamental wall of masonry, or other architectural treatment, earthen embankment, or a combination of any of these which will effectively hide from view any undesirable areas from the main traveled way. SEDIMENT - Solid material, both mineral and organic, that is in suspension, is being transported, or has been moved from its site of origin by air, water, gravity, or ice, as a product of erosion. SEDIMENT BASIN - A depression formed from the construction of a barrier or dam built at a suit­ able location to retain sediment and debris. SEDIMENT DISCHARGE - The quantity of sediment, measured in dry weight or by volume, transported through a stream cross-section in a given time. Sediment discharge consists of both suspended load and bedload. SEDIMENT LOAD - See Sediment Discharge. SEDIMENT POOL - The reservoir space allotted to the accumulation of submerged sediment during the life of the structure. SEEDBED - The soil prepared by natural or ar­ tificial means to promote the germination of seed and the growth of seedlings. SEEPAGE Water escaping through or emerging from the ground along an extensive line or sur­ face as contrasted with a spring where the water emerges from a localized spot. (percolation) The slow movement of gravi­ tational water through the soil. SHEET FLOW - Water, usually storm runoff, flowing in a thin layer over the ground surface; also ---PAGE BREAK--- F-12 2016 Edition called overland flow. SHRINK-SWELL POTENTIAL - Susceptibility to volume change due to loss or gain in moisture content. SHRINKAGE INDEX (SI) - The numerical dif­ ference between the plastic and shrinkage limits. SHRINKAGE LIMIT (SL) - The maximum water content at which a reduction in water content will not cause a decrease in the volume of the soil mass. This defines the arbitrary limit between the solid and semi-solid states. SIDE SLOPE - Generic term used to describe slope of earth-moving operations, generally stated in horizontal to vertical ratio. SILT A soil separate consisting of particles be­ tween 0.05 and 0.002 millimeter in equiva­ lent diameter. A soil textural class. SILTING - See Sediment. SILT LOAM - A soil textural class containing a large amount of silt and small quantities of sand and clay. SILTY CLAY - A soil textural class containing a relatively large amount of silt and clay and a small amount of sand. SILTY CLAY LOAM - A soil textural class con­ taining a relatively large amount of silt, a lesser quantity of clay, and a still smaller quantity of sand. SLOPE - The degree of deviation of a surface from horizontal, measured in a numerical ratio, per­ cent, or degrees. Expressed as a ratio or percent­ age, the first number is the vertical distance (rise) and the second is the horizontal distance (run), as 2:1 or 200 percent. Expressed in degrees, it is the angle of the slope from the horizontal plane with a 90I slope being vertical (maximum) and 45I being a 1:1 slope. SLOPE CHARACTERISTICS - Slopes may be characterized as concave (decrease in steepness in lower portion), uniform, or convex (increase in steepness at base). Erosion is strongly affected by shape, ranked in order of increasing erodibility from concave to uniform to convex. SOIL - The unconsolidated mineral and organic material on the immediate surface of the earth that serves as a natural medium for the growth of land plants. SOIL AMENDMENT - Any material, such as lime, gypsum, sawdust, or conditioner, that is worked into the soil to make it more ame­ nable to plant growth. SOIL HORIZON - A layer of soil or soil mate­ rial approximately parallel to the land surface and differing from adjacent genetically related layers in physical, chemical, and biological properties or characteristics, such as color, structure, texture consistence, kinds and numbers of organisms present, degree of alkalinity, etc. SOIL PROFILE - A vertical section of the soil from the surface through all horizons, including C horizons. SPILLWAY - An open or closed channel, or both, used to convey excess water from a reservoir. It may contain gates, either manually or automati­ cally controlled, to regulate the discharge of excess water. SPOIL - Soil or rock material excavated from a canal, ditch, basin, or similar construction. STABILIZATION - The process of establishing an enduring soil cover of vegetation and/or mulch or other ground cover in combination with installing temporary or permanent structures for the purpose of reducing to a minimum the transport of sediment by wind, water, ice or gravity. STABILIZED GRADE - The slope of a channel at which neither erosion nor deposition occurs. STAGE (hydraulics) - The variable water sur­ face or the water surface elevation above any chosen datum. See Gaging Station. STATE SOIL AND WATER CONSERVATION COMMISSION - The state agency established by soil and water conservation district enabling legislation to assist with the administration of the provisions of that law. STORM DRAIN OUTLET PROTECTION STRUCTURE - A device used to dissipate the energy of flowing water. Generally constructed of concrete or rock in the form of a partially depressed or partially submerged vessel and may utilize ---PAGE BREAK--- F-13 2016 Edition baffles to dissipate velocities. STORM FREQUENCY - An expression or mea­ sure of how often a hydrologic event of a given size or magnitude should on an average occur, based on a reasonable sample. STREAMBANKS - The usual boundaries, not the flood boundaries, of a stream channel. Right and left banks are named facing STREAM GAGING - The quantitative determi­ nation of stream flow using gages, current meters, weirs, or other measuring instruments at selected locations. See Gaging Station. STREAM LOAD - Quantity of solid and dissolved material carried by a stream. See Sediment Load. STRUCTURAL PRACTICES - Soil and water conservation measures, other than vegetation, utilizing the mechanical properties of matter for the purpose of either changing the surface of the land or storing, regulating, or disposing of runoff to prevent excessive sediment loss. Including but not limited to riprap, sediment basins, dikes, level spreaders, waterways or outlets, diversions, grade stabilization structures, sediment traps, land grad­ ing, etc. See Mechanical Practices. SUBSOIL - The B horizons of soils with distinct profiles. In soils with weak profile development, the subsoil can be defined as the soil below the plowed soil (or its equivalent of surface soil), in which roots normally grow. Although a common term, it cannot be defined accurately. It has been carried over from early days when “soil” was conceived only as the plowed soil and that under it as the “subsoil”. SUBWATERSHED - A watershed subdivision of unspecified size that forms a convenient natural unit. TERRACE - An embankment or combination of an embankment and channel across a slope to control erosion by diverting or storing surface runoff instead of permitting it to flow uninterrupted down from the soil. TILE, DRAIN - Pipe made of burned clay, con­ crete, or similar material, in short usually laid with open joints to collect and carry excess water from the soil. TILE DRAINAGE - Land drainage by means of a series of tile lines laid at a specified depth and grade. TILTH - A soil’s physical condition as related to its ease to work (till). TOE (engineering) - Terminal edge or edges of a structure. TOE DRAIN - Interceptor drain located near the toe of a structure. TOPSOIL - Earthy material used as top-dressing for house lots, grounds for large buildings, gar­ dens, road cuts, or similar areas. It has favorable characteristics for production of desired kinds of vegetation or can be made favorable. TRASH RACK - A structural device used to prevent debris from entering a spillway or other hydraulic structure. UNIFIED SOIL CLASSIFICATION SYSTEM (engineering) - A classification system based on the identification of soils according to their particle size, gradation, plasticity index, and liquid limit. UNIFORM FLOW - A state of steady flow when the mean velocity and cross-sectional area are equal at all sections of a reach. UNIVERSAL SOIL LOSS EQUATION - An equa­ tion used for the design of water erosion control systems: A = wherein A = average annual soil loss in tons per acre per year; R = rainfall factor; K = soil erodibility factor; L = length of slope; S = percent of slope; C = cropping and management factor; and P = conservation practice factor. VEGETATIVE MEASURES - Stabilization of erosive or sediment-producing areas by covering the soil with: Permanent seeding, producing long-term vegetative cover, or Short-term seeding, producing temporary vegetative cover, or Sodding, producing areas covered with a turf of perennial sod-forming grass. WATER CLASSIFICATION - separation of water of an area into classes according to usage, such as domestic consumption, fisheries, recreation, indus­ trial, agricultural, navigation, waste disposal, etc. WATER CONSERVATION - The physical con­ trol, protection, management, and use of water resources in such a way as to maintain crop, graz­ ---PAGE BREAK--- F-14 2016 Edition ing, and forest lands; vegetal cover; wildlife; and wildlife habitat for maximum sustained benefits to people, agriculture, industry, commerce, and other segments of the national economy. WATER CONTROL (soil and water conser­ vation) - The physical control of water by such measures as conservation practices on the land, channel improvement, and installation of structures for water retardation and sediment detention (does not refer to legal control or water rights as defined). WATER CUSHION - Pool of water maintained to absorb the impact of water flowing from an overfall structure. WATER DEMAND - Water requirements for a particular purpose, such as irrigation, power, mu­ nicipal supply, plant transpiration, or storage. WATER DISPOSAL SYSTEM - The complete system for removing excess water from land with minimum erosion. For sloping land, it may include a terrace system, terrace outlet channels, dams and grassed waterways. For level land, it may include surface drains or both surface and subsurface drains. WATER QUALITY STANDARDS - Minimum requirements of purity of water for various uses; for example, water for agricultural use in irriga­ tion systems should not exceed specific levels of sodium bicarbonates, pH total dissolved salts, etc. WATER RESOURCES - The supply of ground­ water and surface water in a given area. WATERCOURSE - Any natural or artificial water-course, stream, river, creek, channel, ditch, canal, conduit, drain, waterway, gully, ravine, or wash in which water flows either continuously or intermittently and which has a definite channel, bed and banks, and including any area adjacent thereto subject to inundation by reason of overflow or floodwater. WATERSHED AREA - All land and water within the confines of a drainage divide or a water problem area consisting in whole or in part of land needing drainage or irrigation. WATERSHED LAG - Time from center of mass of effective rainfall to peak of hydrograph. WATERSHED MANAGEMENT - Use, regula­ tion, and treatment of water and land resources of a watershed to accomplish stated objectives. WATERSHED PLANNING - Formulation of a plan to use and treat water and land resources. WATERWAY - An natural course or constructed channel for the flow of water. See Grassed Wa­ terway. WEIR - Device for measuring or regulating the flow of water. WEIR NOTCH - The opening in a weir for the passage of water. WETTING AGENT - A chemical that reduces the surface tension of water and enables it to soak into porous material more readily. This glossary was compiled from definitions supplied by the Natural Resources Conservation Service, Soil and Water Conservation Society of America, Resource Conservation Glossary, and other state and federal publications. ---PAGE BREAK--- G-1 2016 Edition 1. Agricultural Research Service and Environmental Protection Agency, Control of Water Pollution From Cropland, ARS-H-5-1 or Environmental Protection Agency-600/2-75-026a, November, 1975. 2. Baltimore County, Maryland, Sediment Control Manual, October, 1968. 3. Barnett, A.P. and B.H. Hendrickson, “Erosion on Piedmont Soils,” Soil Conservation Magazine, USDA, Soil Conservation Service, Volume XXVI, No. 2, Sept., 1960. 4. Cooperative Extension Service, Ohio, Ohio Erosion Control and Sediment Pollution Abatement Guide, Bulletin 594, March, 1975. 5. Davis, Raymond F.S. Foote, and J. W. Delly, Surveying Theory and Practice, McGraw-Hill Book Company, 1968. 6. Department of Natural Resources, Georgia, Land Reclamation Performance Standards, Draft copy, October 1975. 7. Department of Natural Resources, West Virginia, Drainage Handbook for Surface Mining, January, 1975. 8. Department of Public Works, Division of Highways, California, Bank and Shore Protection in California Highway Practice, November, 1970. 9. Department of Transportation, Georgia, Standard Specifications: Construction of Roads and Bridges, 1993. 10. Diseker, E. and Richardson, E.C., Transaction of the American Society of Agricultural Engineers, St. Joseph, Michigan, vol. 1, No. 1, pp 62-64, 68. 11. Environmental Protection Agency, Guidelines for Erosion and Sediment Control Planning and Implemen­ tation, Environmental Protection Agency-R2-72-015, August 1972. 12. Environmental Protection Agency, Control of Erosion and Sediment Deposition From Construction of Highways and Land Development, September, 1971. 13. Environmental Protection Agency, Methods and Practices for Controlling Water Pollution From Agricultural Non-Point Sources, Environmental Protection Agency-430/9-73-015, October, 1973. 14. Environmental Protection Agency, Proceedings Workshop on Agricultural Non-Point Source Water Pol­ lution Control, September 16-17, 1974, Mayflower Hotel, Washington, D.C. 15. Environmental Protection Agency, Guidelines for Erosion and Sediment Control Planning and Implemen­ tation, Environmental Protection Agency-430/9-73-014, October, 1973. 16. Environmental Protection Agency, Processes, Procedures, and Methods to Control Pollution Resulting from All Construction Activity, Environmental Protection Agency-430/9-73-007, October, 1973. 17. Federal Highway Administration, Suggestions for Temporary Erosion and Siltation Control Measures, February, 1973. 18. 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Soil Conservation Service, Guidelines for the Control of Erosion and Sediment in Urban Areas of the Northeast, August, 1970. 33. Soil Conservation Service, Michigan Program for Soil Erosion and Sedimentation Control, July 1973. 34. Soil Conservation Service, Mississippi, Guidelines for the Control of Erosion and Sediment in Urbanizing Areas Within Mississippi, August, 1975. 35. Soil Conservation Service, National Engineering Handbook, Section 3, Sedimentation, Section 4, Hydrol­ ogy. 36. Soil Conservation Service, North Carolina, Guide for Sediment Control on Construction Sites in North Carolina, March, 1973. 37. Soil Conservation Service, Ohio, Water Management and Sediment Control for Urbanizing Areas, April, 1972. 38. Soil Conservation Service, Planning and Design of Open Channels, Technical Release No. 25, December, ---PAGE BREAK--- G-3 2016 Edition 1964. 39. Soil Conservation Service, Procedure for Computing Sheet and Rill Erosion on Project Areas, Technical Release No. 51, Geology, January 1975. 40. Soil Conservation Service, Standards and Specification for Soil Erosion and Sediment Control in Urban­ izing Areas, November, 1968. 41. Soil Conservation Service, Urban Hydrology for Small Watersheds, 2nd Edition, Technical Release No. 55, June, 1986. 42. United States Forestry Service, Tractor Attachments for Brush, Slash and Root Removal, ED & T 1332, January, 1971. 43. United States Geological Survey Water - Data Report Georgia-75-1, Water Resources Data for Georgia Water Year 1975, Georgia-75-1. 44. USDA Agricultural Research Service, PAMphlet: a concise guide for safe and practical use of polyacry- lamide(PAM) for irrigation-induced erosion control and infiltration enhancement. USDA-ARS Northwest Irrigation and Soils Research Laboratory Station Note #02-98. 45. 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Cross, A Soil Erodibility Nomograph for Farmland and Con­ struction Sites. Journal of Soil and Water Conservation 26(5): 189-193, 1971. ---PAGE BREAK--- G-4 2016 Edition