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21156 Preliminary Stormwater Report.docx Page 1 of 12 HIEX HOTEL REMODEL & ADDITION REVISED STORM DESIGN REPORT For Amandeep Virk 8815 SW Sun Place Wilsonville, OR 97070 By MSS Inc. 215 NW 4th Street Corvallis, OR 97330 Prepared by Linsey McLane-Godwin Reviewed by Peter Seaders Job Number: 21156 March 31, 2023 6/30/2024 ---PAGE BREAK--- MSS INC [HIEX Storm Design Report] 21156 Preliminary Stormwater Report.docx Page 2 of 12 1 TABLE OF CONTENTS 1 Purpose of Report 3 2 Project Description 3 3 Existing Conditions Summary 3 3.1 Existing Site Conditions 3 3.2 Soil Conditions 4 3.3 Sensitive and Critical Areas 4 4 Developed Conditions & Calculations Summary 5 4.1 Design Criteria & Calculations Summary 5 4.2 Proposed Stormwater System: 6 4.3 Analysis Results & Summary 6 5 Appendices 7 Appendix A – Existing Conditions Map 8 Appendix B – Preliminary Grading & Drainage Plan 9 Appendix C – Rational Method Analysis Results 10 Appendix D – NRCS Soil Report 11 Appendix E – Stormwater Detention & Flow Control Manhole Detail 12 ---PAGE BREAK--- MSS INC [HIEX Storm Design Report] 21156 Preliminary Stormwater Report.docx Page 3 of 12 1 PURPOSE OF REPORT The purpose of this report is to fulfill the required storm water report specified by Woodburn Development Ordinance Design Review application for the HIEX Hotel Remodel & Addition. The project includes the enlargement of the porta cochere, enclosure of an existing pool and the addition of floors above the enclosed pool. Additionally, the parking lot will be expanded to provide parking for the proposed additional hotel rooms. The drainage system is designed to collect the runoff created by the existing building and parking lot, proposed addition and parking lot expansion. The drainage system is private on-site and on the adjacent property to the west and north until it connects with the publicly owned system maintained by the Oregon Department of Transportation (ODOT). Water quality is not required per City of Woodburn standards. The runoff will drain into the existing storm drainage system. All design analysis in this report has been performed in accordance with Woodburn Development Ordinance (WDO), the Woodburn Storm Drainage Master Plan (SDMP) Chapters 7 and 11 and the ODOT Hydraulics Manual. Results presented in this report are preliminary, and subject to refinement in final design. 2 PROJECT DESCRIPTION The new development applicable to this report includes the construction of: • 0.28 acre of new impervious surface for the addition and increased parking area. • Expansion of the storm drainage infrastructure. The total impervious area is 1.38 acres. 3 EXISTING CONDITIONS SUMMARY 3.1 EXISTING SITE CONDITIONS The HIEX Hotel Remodel & Addition development is a 1.76-acre site located at 120 N Arney Rd, Woodburn, Oregon. The site contains an existing hotel and parking lot with 1.1-acres of impervious surface and an existing onsite stormwater drainage system connected to the public stormwater system. The development is on the south and east side of N Arney Road, north of Hillsboro-Silverton Hwy NE and west of Interstate-5. The subject property is currently developed, see Appendix A. The onsite slope ranges from 3-20%. The entire site generally slopes from the north to the south and southwest. There is a high point at the entrance to the existing hotel. From this high point the land gently slopes in all directions. ---PAGE BREAK--- MSS INC [HIEX Storm Design Report] 21156 Preliminary Stormwater Report.docx Page 4 of 12 3.2 SOIL CONDITIONS There are two soils identified on the subject property: 0.2% consists of Ba — Bashaw clay with an infiltration rate range of 0.00 to 0.06 inches per hour (in/hr) and 99.8% consists of WuA — Woodburn silt loam, 0 to 3 percent slopes with an infiltration rate range of 0.06 to 0.20 in/hr. Bashaw clay is classified as Hydrological Soil Group D, while Woodburn silt loam is classified as Hydrological Soil Group C. Refer to Appendix D, NRCS Soil Report, for the soil map and soil description. 3.3 SENSITIVE AND CRITICAL AREAS No wetlands or sensitive/critical areas were identified on the property. The Federal Emergency Management Agency (FEMA) Flood Insurance Map 41047C0119G, effective January 19, 2000, shows the subject property as not within a regulated floodplain. ---PAGE BREAK--- MSS INC [HIEX Storm Design Report] 21156 Preliminary Stormwater Report.docx Page 5 of 12 4 DEVELOPED CONDITIONS & CALCULATIONS SUMMARY 4.1 DESIGN CRITERIA & CALCULATIONS SUMMARY The on-site stormwater system is a private system that connects to Oregon Department of Transportation (ODOT) facilities in both N Arney Rd and the Hillsboro-Silverton Highway. Based on conversations with ODOT and City of Woodburn staff on June 13, 2022, the proposed stormwater system must meet the ODOT Hydraulics Manual storm detention requirements. Below are the stormwater criteria from the Woodburn Development Ordinance, the Woodburn Storm Drainage Master Plan and the ODOT Hydraulics Manual. 4.1.1 Woodburn Development Ordinance (WDO) 3.05.02 General Provisions G. All vehicle parking, loading, and storage areas shall be graded and provide storm drainage facilities approved by the Director. 4.1.2 Woodburn Storm Drainage Master Plan (SDMP) Chapter 11 H. Detention Requirement for Small Developments: Any new construction, or expansion of existing construction, for commercial, industrial, institutional, or multi-family uses which creates less than 2.5 acres of total impervious areas (not including public roads created as part of the development) may be required to provide on-site detention to address system capacity limitations, satisfy requirements of other jurisdictions, or mitigate local conditions which preclude full discharge of stormwater. At a minimum, the following information will be required for City staff review: 1. Calculations of the volume and rate of stormwater runoff prior to and following development, done in conformance with City policy and the Storm Drainage Master Plan. 2. Identification of the closest public storm sewer or drainageway which will receive the runoff from the development. 3. Calculations showing the peak flow rate of storm water which will be discharged to the public system including any deleterious hydraulic impacts of stormwater runoff on facilities (pipes, culvert, ditches, etc.) 4.1.3 ODOT Hydraulics Manual 12.5.1 General Criteria Detention may not be needed when it is not required by the local jurisdiction and any one of the following criteria is met: a. The uncontrolled peak post-construction runoff rate during the design storm is less than 0.5 cubic feet per second, and the total contributing area after the proposed development is less than 0.25 acre. 4.1.4 ODOT Hydraulics Manual 12.5.1.1: A. For detention facilities which serve 5 acres or less and discharge directly to and are physically connected to storm sewers or which discharge to ditches which do not lead directly to cross culverts or inlets: ---PAGE BREAK--- MSS INC [HIEX Storm Design Report] 21156 Preliminary Stormwater Report.docx Page 6 of 12 • 10-year. The subject property contains less than 2.5 acres of total impervious areas. As described above, the on- site stormwater system does not discharge into a public storm sewer system or drainageway maintained by the City of Woodburn, but instead discharges into systems maintained by ODOT. As a result, the City of Woodburn is deferring to ODOT stormwater detention requirements. According to ODOT Hydraulics Manual Section 12.5.1.1.A, the proposed system calculations should be based on the rational method using the 10-year design storm. As shown in Appendix C, the pre-development peak runoff rate during the design storm is 2.38 cubic feet per second. 4.2 PROPOSED STORMWATER SYSTEM: The proposed parking lot expansion, shown on Appendix B, Preliminary Grading & Utility Plan sheet P210 may not qualify for the exception to detention. While the increase in uncontrolled peak post- construction runoff rate during the design storm is less than 0.5 cubic feet per second, the increase in pavement is exceeds the 0.25-acre threshold (the proposed development adds 0.28 acres of additional impervious area). To match the post-development peak runoff rate to pre-development conditions, a stormwater detention volume of at least 120 cubic feet will be needed, if required by ODOT. The storage will be provided in a 96-inch-diameter manhole with 2.39 vertical feet of storage between the inlet and the outlet elevations. The manhole will fitted with a 7.66-inch-diameter orifice, sized per Appendix C to limit the peak outflow to 2.38 cubic feet per second. Alternatively, the storage volume can be provided by oversized piping integrated into the proposed storm system, or other underground storage systems such as arch pipes or rock galleries. The runoff from the proposed expansion will be collected in a series of catch basins which are to be piped into the existing private on-site stormwater infrastructure. The flow control manhole will be installed in-line with the existing infrastructure, of the new catch basin connections. Below said manhole, the runoff from both the existing and proposed tributary area will follow the existing conveyance off the site and into the ODOT system to the southwest. There is no stormwater treatment proposed for this site and none is required by either the City of Woodburn nor ODOT. 4.3 ANALYSIS RESULTS & SUMMARY Runoff analysis was performed following the ODOT Hydraulics Manual code requirements. The ODOT Rational Method was used for calculations. No water quality treatment of the stormwater runoff is required. The proposed stormwater infrastructure connects to the existing infrastructure at the required rate. Detention for 120 cubic feet of stormwater is provided on-site. ---PAGE BREAK--- 21156 Preliminary Stormwater Report.docx Page 7 5 APPENDICES ---PAGE BREAK--- MSS INC [HIEX Storm Design Report] 21156 Preliminary Stormwater Report.docx Page 8 APPENDIX A – EXISTING CONDITIONS MAP ---PAGE BREAK--- EXISTING CONDITIONS P100 MSS, Inc. holds all rights to the plans and ideas on this sheet. These plans and specifications are for the construction of one project and restricted to the original site for which the were prepared as shown in the title block. These plans are not to be copied in any form whatsoever without the expressed written permission of MSS, Inc. The contractor shall be responsible for checking dimensions and site conditions and is to report any errors or omissions in writing to the designers before the start of construction. 215 NW 4th STREET CORVALLIS, OR 97330 (541) 753-1320 FAX:(541) 753-5956 ENGINEERING CONSULTANTS MSS INC AND PLANNERS HIEX WOODBURN ADDITION WOODBURN, OREGON VARITONE ARCHITECTURE 231 SW 2ND AVE ALBANY, OREGON (541) 497-2954 MSS, Inc. holds all rights to the plans and ideas on this sheet. These plans and specifications are for the construction of one project and restricted to the original site for which the were prepared as shown in the title block. These plans are not to be copied in any form whatsoever without the expressed written permission of MSS, Inc. The contractor shall be responsible for checking dimensions and site conditions and is to report any errors or omissions in writing to the designers before the start of construction. ---PAGE BREAK--- MSS INC [HIEX Storm Design Report] 21156 Preliminary Stormwater Report.docx Page 9 APPENDIX B – PRELIMINARY GRADING & DRAINAGE PLAN ---PAGE BREAK--- C C C C C C C C C C C C C C C C C EV EV EV EV CV CV CV 215 NW 4th STREET CORVALLIS, OR 97330 (541) 753-1320 FAX:(541) 753-5956 ENGINEERING CONSULTANTS MSS INC AND PLANNERS HIEX WOODBURN ADDITION WOODBURN, OREGON VARITONE ARCHITECTURE 231 SW 2ND AVE ALBANY, OREGON (541) 497-2954 MSS, Inc. holds all rights to the plans and ideas on this sheet. These plans and specifications are for the construction of one project and restricted to the original site for which the were prepared as shown in the title block. These plans are not to be copied in any form whatsoever without the expressed written permission of MSS, Inc. The contractor shall be responsible for checking dimensions and site conditions and is to report any errors or omissions in writing to the designers before the start of construction. PRELIMINARY GRADING & UTILITY PLAN P210 GENERAL NOTES · ALL ELEVATIONS ARE FG PAVING U.N.O. · SLOPES SHALL HAVE A MAXIMUM CONSTRUCTED SLOPE OF 2:1 AFTER STABILIZATION. · GRADE AT LANDSCAPED AREAS TO BE 6” MIN BELOW BUILDING FINISH FLOOR ELEVATION. · ADA PARKING SPACES & LOADING AREA SHALL HAVE A MAXIMUM SLOPE OF 2% IN ANY DIRECTION. · SIDEWALK CROSS SLOPE SHALL BE 1.5% TYP U.N.O., BUT SHALL NOT EXCEED LONGITUDINAL SLOPES SHALL NOT EXCEED U.N.O. PROVIDE HANDRAILS FOR SLOPES BETWEEN 5% & 8.33%. NO SLOPES WITHIN AN ADA PATH OF TRAVEL MAY EXCEED 8.33% FINAL CONSTRUCTED SLOPE. · NO NEW SEWER OR WATER SERVICE IS REQUIRED, EXISTING SERVICES TO BE MAINTAINED · NO NEW STREET LIGHTS ARE REQUIRED. EXISTING STREET LIGHTS MEET THE ILLUMINATING ENGINEERING SOCIETY (IES) OF NORTH AMERICA RECOMMENDED PRACTICE 8, ROADWAY LIGHTING (RP-8) STANDARDS. GRADING & UTILITY KEYNOTES 1 EXISTING SEWER SERVICE TO BE REUSED, SIZING TO BE CONFIRMED BY MEP AT BUILDING PERMIT. 2 EXISTING WATER METERS TO BE RELOCATED AND REUSED (OR REPLACED, IF NEEDED), SIZING TO BE CONFIRMED BY MEP AT BUILDING PERMIT. 3 EXISTING POWER TRANSFORMER TO BE REUSED, SIZING TO BE CONFIRMED BY MEP AT BUILDING PERMIT. EXISTING FIRE HYDRANTS TO BE REUSED. SEE FIRE FLOW REPORT FOR FLOW RATES. 5. EXISTING FDCS TO BE REUSED. FDCS SHALL BE CLEARLY LABELED TO INDICATE THEIR PURPOSE (ONE FOR SPRINKLERS AND ONE FOR STANDPIPES). 6. ARNEY RD DRIVEWAY TO BE RECONSTRUCTED PER CITY OF WOODBURN PUBLIC WORKS STANDARD DRAWING NO. WALL EXTENTS MAY BE REDUCED IF GRADING INTO RW IS APPROVED BY ODOT. STORMWATER NOTES · TOTAL IMPERVIOUS AREA IS 1.32 ACRES OF THE 1.6 ACRES SITE. · NEW IMPERVIOUS SURFACE FOR THE ADDITION AND INCREASED PARKING AREA TOTAL ACRE AND AN EXPANSION OF THE STORM DRAINAGE INFRASTRUCTURE. · THE EXISTING STORMWATER SYSTEM SERVING THE SITE IS A PRIVATE SYSTEM THAT FEEDS INTO AN OREGON DEPARTMENT OF TRANSPORTATION (ODOT) SYSTEM. AS A RESULT, THE STORM WAS DESIGNED TO ODOT HYDRAULICS MANUAL STANDARDS. · UNDER EXISTING CONDITIONS, THE TOTAL TRIBUTARY IMPERVIOUS AREA TO THE OUTFALL FOR THIS PRO-ECT IS 1.1 ACRES, AND THE PEAK OUTFLOW IS 2.38 CFS. THE DEVELOPMENT PROPOSES .28 ACRES OF ADDITIONAL IMPERVIOUS AREA. BASED ON THE ODOT STANDARDS FOR STORMWATER DETENTION, WHICH USE THE RATIONAL METHOD FOR A 1-YEAR DESIGN STORM, A STORAGE VOLUME OF 12 FT3 MAY BE REQUIRED. THE PROPOSED STORAGE SYSTEM IS A 6 MANHOLE WITH A MAXIMUM STORAGE DEPTH OF 2.3 AND A .66 ORIFICE. ALTERNATE STORAGE SYSTEMS MAY BE USED TO MEET DESIGN REQUIREMENTS AT TIME OF PERMIT IF DETENTION IS REQUIRED BY ODOT. · NO WATER QUALITY FACILITIES ARE REQUIRED BY EITHER ODOT OR THE CITY OF WOODBURN. ---PAGE BREAK--- MSS INC [HIEX Storm Design Report] 21156 Preliminary Stormwater Report.docx Page 10 APPENDIX C – RATIONAL METHOD ANALYSIS RESULTS ---PAGE BREAK--- Detention Storage - Rational Method Project: HIEX Hotel Remodel & Addition Prepared By: LMG/NT/PS Before Development Conditions Hydrologic Zone 7 C A CA Storm Frequency (yrs) 10 Pervious 0.22 0.66 0.15 Impervious 0.9 1.1 0.99 Tc I (inches/hr) Qoutflow Total / Weighted 0.65 1.76 1.1 5 2.1 2.38 After Development Conditions C A CA Max Depth @ orifice 2.39 ft Pervious 0.22 0.38 0.08 Single Orifice Size = 7.66 inches Impervious 0.9 1.38 1.24 Tc Total / Weighted 0.75 1.76 1.33 5 Time CA Rain Inten. Inflow Rate Inflow Vol Outflow Rate Outflow Vol Min. Acres in/hr cfs ft3 cfs ft3 5 1.3 2.10 2.8 835 2.38 715 120 10 1.3 1.62 2.1 1,288 2.38 1,430 - - - 15 1.3 1.38 1.8 1,646 2.38 2,146 - - - 20 1.3 1.20 1.6 1,909 2.38 2,861 - - - 25 1.3 1.06 1.4 2,108 2.38 3,576 - - - 30 1.3 0.96 1.3 2,291 2.38 4,291 - - - 35 1.3 0.87 1.2 2,422 2.38 5,006 - - - 40 1.3 0.80 1.1 2,545 2.38 5,721 - - - 45 1.3 0.74 1.0 2,649 2.38 6,437 - - - 50 1.3 0.68 0.9 2,704 2.38 7,152 - - - 55 1.3 0.66 0.9 2,887 2.38 7,867 - - - 60 1.3 0.60 0.8 2,863 2.38 8,582 - - - 65 1.3 0.58 0.8 2,999 2.38 9,297 - - - 70 1.3 0.55 0.7 3,062 2.38 10,012 - - - 80 1.3 0.51 0.7 3,245 2.38 11,443 - - - 90 1.3 0.48 0.6 3,436 2.38 12,873 - - - 100 1.3 0.46 0.6 3,659 2.38 14,304 - - - 120 1.3 0.42 0.6 4,009 2.38 17,164 - - - 150 1.3 0.39 0.5 4,653 2.38 21,455 - - - 200 1.3 0.34 0.5 5,408 2.38 28,607 - - - 250 1.3 0.31 0.4 6,164 2.38 35,759 - - - 300 1.3 0.29 0.4 6,920 2.38 42,911 - - - Required Storage = 120 ft3 REQ'd Storage ft3 Prepared by MSS Inc 3/31/2023 Page 1 ---PAGE BREAK--- MSS INC [HIEX Storm Design Report] 21156 Preliminary Stormwater Report.docx Page 11 APPENDIX D – NRCS SOIL REPORT ---PAGE BREAK--- United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Marion County Area, Oregon Woodburn Hotel Remodel Natural Resources Conservation Service June 1, 2022 ---PAGE BREAK--- Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/ portal/nrcs/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center or your NRCS State Soil Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/? cid=nrcs142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require 2 ---PAGE BREAK--- alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 ---PAGE BREAK--- Contents 2 How Soil Surveys Are Soil 8 Soil Map Unit 11 Map Unit Marion County Area, Ba—Bashaw 13 WuA—Woodburn silt loam, 0 to 3 percent 4 ---PAGE BREAK--- How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil-vegetation-landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil 5 ---PAGE BREAK--- scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil-landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil-landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field-observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and Custom Soil Resource Report 6 ---PAGE BREAK--- identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. Custom Soil Resource Report 7 ---PAGE BREAK--- Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 8 ---PAGE BREAK--- 9 Custom Soil Resource Report Soil Map 4999760 4999780 4999800 4999820 4999840 4999860 4999880 4999760 4999780 4999800 4999820 4999840 4999860 4999880 509120 509140 509160 509180 509200 509220 509240 509260 509280 509300 509120 509140 509160 509180 509200 509220 509240 509260 509280 509300 45° 9' N 122° 53' W 45° 9' N 122° 52' 53'' W 45° 9' N 122° 53' W 45° 9' N 122° 52' 53'' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 40 80 160 240 Feet 0 10 20 40 60 Meters Map Scale: 1:907 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. ---PAGE BREAK--- MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:20,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Marion County Area, Oregon Survey Area Data: Version 19, Oct 27, 2021 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 19, 2015—Sep 13, 2016 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Custom Soil Resource Report 10 ---PAGE BREAK--- Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI Ba Bashaw clay 0.0 0.2% WuA Woodburn silt loam, 0 to 3 percent slopes 1.8 99.8% Totals for Area of Interest 1.8 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, Custom Soil Resource Report 11 ---PAGE BREAK--- onsite investigation is needed to define and locate the soils and miscellaneous areas. An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Custom Soil Resource Report 12 ---PAGE BREAK--- Marion County Area, Oregon Ba—Bashaw clay Map Unit Setting National map unit symbol: 24nt Elevation: 100 to 400 feet Mean annual precipitation: 40 to 45 inches Mean annual air temperature: 52 to 54 degrees F Frost-free period: 200 to 210 days Farmland classification: Farmland of statewide importance Map Unit Composition Bashaw and similar soils: 85 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Bashaw Setting Landform: Flood plains Landform position (three-dimensional): Tread Down-slope shape: Concave, linear Across-slope shape: Linear Parent material: Alluvium Typical profile H1 - 0 to 14 inches: clay H2 - 14 to 48 inches: clay H3 - 48 to 60 inches: clay Properties and qualities Slope: 0 to 1 percent Depth to restrictive feature: More than 80 inches Drainage class: Poorly drained Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table: About 0 to 12 inches Frequency of flooding: NoneFrequent Frequency of ponding: Frequent Available water supply, 0 to 60 inches: Moderate (about 9.0 inches) Interpretive groups Land capability classification (irrigated): 4w Land capability classification (nonirrigated): 4w Hydrologic Soil Group: D Ecological site: R002XC005OR - High Floodplain Group Forage suitability group: Poorly Drained (G002XY006OR) Other vegetative classification: Poorly Drained (G002XY006OR) Hydric soil rating: Yes Custom Soil Resource Report 13 ---PAGE BREAK--- WuA—Woodburn silt loam, 0 to 3 percent slopes Map Unit Setting National map unit symbol: 24s3 Elevation: 150 to 350 feet Mean annual precipitation: 40 to 45 inches Mean annual air temperature: 52 to 54 degrees F Frost-free period: 200 to 210 days Farmland classification: All areas are prime farmland Map Unit Composition Woodburn and similar soils: 85 percent Minor components: 1 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Woodburn Setting Landform: Terraces Landform position (three-dimensional): Tread Down-slope shape: Linear Across-slope shape: Linear Parent material: Silty alluvium and mixed mineralogy loess Typical profile H1 - 0 to 17 inches: silt loam H2 - 17 to 32 inches: silty clay loam H3 - 32 to 68 inches: silt loam Properties and qualities Slope: 0 to 3 percent Depth to restrictive feature: More than 80 inches Drainage class: Moderately well drained Capacity of the most limiting layer to transmit water (Ksat): Moderately low to moderately high (0.06 to 0.20 in/hr) Depth to water table: About 25 to 32 inches Frequency of flooding: None Frequency of ponding: None Available water supply, 0 to 60 inches: High (about 12.0 inches) Interpretive groups Land capability classification (irrigated): 2w Land capability classification (nonirrigated): 2w Hydrologic Soil Group: C Ecological site: R002XC008OR - Valley Terrace Group Forage suitability group: Moderately Well Drained < 15% Slopes (G002XY004OR) Other vegetative classification: Moderately Well Drained < 15% Slopes (G002XY004OR) Hydric soil rating: No Custom Soil Resource Report 14 ---PAGE BREAK--- Minor Components Aquolls, somewhat poorly drained Percent of map unit: 1 percent Landform: Terraces Hydric soil rating: Yes Custom Soil Resource Report 15 ---PAGE BREAK--- References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/national/soils/?cid=nrcs142p2_054262 Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ home/?cid=nrcs142p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/ 16 ---PAGE BREAK--- United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/soils/scientists/?cid=nrcs142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/? cid=nrcs142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf Custom Soil Resource Report 17 ---PAGE BREAK--- MSS INC [HIEX Storm Design Report] 21156 Preliminary Stormwater Report.docx Page 12 APPENDIX E – STORMWATER DETENTION & FLOW CONTROL MANHOLE DETAIL ---PAGE BREAK--- 1