Document Laramie_doc_050b4e948e

The North Laramie Drainage Master Plan SEH Job Number - LARAM 112351 Final Report January 2013 Prepared For City of Laramie Prepared By Short Elliott Hendrickson Inc. 390 Union Blvd., Suite 630 Lakewood, CO 80228 [PHONE REDACTED] [PHONE REDACTED]-Fax ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page i Table of Contents 1.0 ACKNOWLEDGEMENT 1 2.0 INTRODUCTION 2 2.1 Authorization 2 2.2 Purpose and Scope 2 2.3 Public Process 2 2.4 Baseline Information 3 2.4.1 Survey Data Collection and Structure Inventory 3 2.4.2 Geotechnical Investigation 3 2.5 Design Procedures 3 3.0 STUDY AREA DESCRIPTION 4 3.1 Location 4 3.2 Existing Outfalls 4 3.3 Flood History 4 3.4 Land Characteristics 5 3.5 Land Use 5 4.0 HYDROLOGIC MODEL 6 4.1 General 6 4.2 Rainfall Data 6 4.3 and CUHP Parameters 7 4.4 Calibration 9 4.5 Street Capacity 10 4.6 Detention Areas 10 4.7 Addition of LaBonte Subbasins 11 4.8 11 5.0 PRELIMINARY IDENTIFICATION OF FLOOD PRONE AREAS 15 5.1 Existing Percent Imperviousness 15 5.2 Future Percent Imperviousness 16 5.3 Existing Detention Ponds 16 6.0 ANALYSIS OF ALTERNATIVE IMPROVEMENTS 21 6.1 General 21 6.2 Qualitative Analysis of Alternative Improvements 21 6.3 Quantitative Analysis of Alternative Improvements 22 6.3.1 Upstream Improvements 22 6.3.2 Alternative 1: Upsize Existing Trunk Line Sewers 23 6.3.3 Alternative 2: Additional Trunk Line Sewers 24 6.3.4 Alternative 3: LaBonte Discharge and Upsize Trunk Line Sewers 24 6.4 Cost Analysis of Alternative Improvements 25 6.5 Water Quality and Erosion Control 28 7.0 RECOMMENDED PLAN 29 7.1 Plan Description 29 7.2 Floodproofing 34 7.3 Cost Analysis of Recommended Plan 34 7.4 Recommendation of Construction Phasing 35 7.5 Water Quality Impacts 37 7.6 Operations and Maintenance 37 ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page ii 8.0 DEVELOPING A STORMWATER UTILITY 38 9.0 REFERENCES 40 Tables Table 1: Weather Station Data vs. NOAA Atlas Data for 24‐hour Point Rainfall Depths 6 Table 2: NOAA 1‐hour Point Rainfall Depths 7 Table 3: 2‐hour Precipitation Distribution Depths from CUHP 7 Table 4: Soil Infiltration Parameters 8 Table 5: Percent Impervious for Existing Land Uses in Study Area 8 Table 6: Percent Impervious for Future Land Uses in Study Area 8 Table 7: Typical Conveyance Element Parameters 9 Table 8: Flood Peak Calibration, to CUHP 9 Table 9: Location and Approximate Volume of Detention Areas 11 Table 10: Existing Flood Peaks 12 Table 11: Future Flow Peaks 13 Table 12: Percent Increase of Flows from Existing to Future 14 Table 13: North Laramie Problem Areas ‐ Existing Percent Impervious 17 Table 14: North Laramie Problem Areas ‐ Future Percent Impervious 19 Table 15: Estimated Regional 100‐Year Detention Volumes for Undeveloped Subbasins 22 Table 16: Estimated Increase in Detention Volumes for Existing Detention Ponds 23 Table 17: Conceptual Cost Estimate for Alternative 1 26 Table 18: Conceptual Cost Estimate for Alternative 2 27 Table 19: Conceptual Cost Estimate for Alternative 3 28 Table 20: Conceptual Cost Estimate Recommended Plan 35 Figures Figure 1: Location Map 4 Figure 2: Typical Urban Street Section 10 Figure 3: Typical Urban Street Section Capacity Rating Curve 10 Figure 4: Flowchart for Phase One of Developing a Stormwater Utility 38 Figure 5: Hydrologic Soils Group Figure 6: Existing Land Use Figure 7: Future Land Use Figure 8: Rain Gage Locations Figure 9a: Subbasin Delineation Map Figure 9b: Basin Contour Map (24” x 36” Fold Out Map) Figure 10a‐10d: Routing Schematic Figure 11: Reach Designations Figure 12: Areas of Flooding: 2‐ and 100‐year Events – Existing Percent Impervious Figure 13: Areas of Flooding: 2‐ and 100‐year Events – Future Percent Impervious Figure 14: Upstream Alternative: Pond Modifications Figure 15: Alternative 1: Upsize Existing Trunk Line Sewers Figure 16: Alternative 2: Additional Trunk Line Sewers Figure 17: Alternative 3: LaBonte Discharge and Upsize Existing Trunk Line Sewers Figure 18: Recommended Plan Figure 19: Recommended Plan – Proposed Pond Contours Figure 20: Recommended Phasing Plan ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page iii Appendices Appendix A – Public Meeting Comments Appendix B – Survey Notes Appendix C – Inventory of Existing Storm Structures Appendix D – Geotechnical Report Appendix E – CUHP Input Appendix F – Detention Pond Calculations Appendix G – Input/ Output – Existing Conditions Appendix H – Input/ Output – Future Conditions Appendix I – Rainfall Data Appendix J – Conceptual Solution Scoring Matrix Appendix K – Conceptual Outfall at Harney Street ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page iv THIS PAGE INTENTIONALLY LEFT BLANK. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 1 1.0 ACKNOWLEDGEMENT SEH wishes to acknowledge the various individuals who assisted in the preparation of this North Laramie Drainage Master Plan. The City of Laramie provided the guidance and knowledge of the North Laramie drainage issues that made this Drainage Master Plan possible. In addition, several residents provided insight regarding specific problem areas, observations during rainfall events and photographs of problem areas. The following members of the SEH project team have contributed in the preparation of this report. E. Danny Elsner PE, SEH (Project Manager) Roger Peterson PE, SEH (Sr. Drainage Engineer) Steve Gardner PE, SEH (Sr. Drainage Engineer) Kelly Jankowski EI, SEH (Staff Engineer) George Walton PE, Progressive Enterprises, Inc. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 2 2.0 INTRODUCTION 2.1 Authorization The City of Laramie has contracted Short Elliott Hendrickson Inc. (SEH) to complete a drainage master plan for the northern portion of the City of Laramie in response to many drainage problems in the area. 2.2 Purpose and Scope The purpose of the North Laramie Drainage Master Plan is to analyze the existing and future drainage conditions, identify problem areas within the study area, and provide alternate methods to convey stormwater within the study area to enhance public safety and minimize property damage. The drainage master plan document may serve as a guideline for addressing water quality degradation and flood peak increases resulting from current and future development within the study area. It may also be used to standardize storm drainage criteria for the City of Laramie and may be used to establish framework for future storm modeling of development. The drainage master plan entailed:  Holding three public meetings;  Obtaining survey data of existing stormwater management facilities;  Obtaining documents and files from the City including existing drainage and development plans and GIS data;  Performing a geotechnical investigation;  Performing a rainfall analysis for the study area;  Identifying probable flow paths and catchment areas under current land use;  Developing base hydrologic prediction models for existing and project future percent imperviousness for the 10‐, and 100‐year storm events;  Identifying existing stormwater management facilities and the adequacy of their hydraulic operation under existing and proposed percent imperviousness;  Defining critical areas requiring stormwater management;  Qualitative analysis of possible alternatives to alleviate critical areas of potential flooding;  Quantitative analysis of the top alternatives from the qualitative analysis and size the necessary improvements,  Cost analysis of the top alternatives; and  Providing a recommended plan of improvements and correspond cost analysis. 2.3 Public Process Two initial public meetings were held at Fire Station No. 2 on Wednesday, June 23rd and Thursday, June 24th, 2010 from 6 to 8 pm. The purpose of the public meetings was to make the public aware of the drainage master plan being developed and to gather insight and information on problem areas from the citizens living within the study area. Information collected from the public meeting attendees can be found in Appendix A. A third public meeting was held on January 26, 2011 to inform the citizens of hydrologic model findings and possible solutions to the existing drainage problems. During these meetings, the public identified multiple locations of local drainage. These local issues are described throughout the report. A meeting sign in sheet can be found in Appendix A. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 3 2.4 Baseline Information Information used for the outfall study includes:  Topographic mapping information, mapped using aerial photogrammetry, was obtained from the City of Laramie as GIS contours at two‐foot contour intervals (City of Laramie, 2010);  Existing Zoning and Proposed Land Use maps for the City of Laramie (City of Laramie, 2010);  NRCS soils maps for Albany County (NRCS, 2007);  Flood Insurance Studies (FIS) and Flood Insurance Rate Maps (FIRM) updated in 1996;  Various drainage reports and development plans within the study area provided by the City of Laramie. 2.4.1 Survey Data Collection and Structure Inventory Existing storm sewer infrastructure data was collected by Coffey Engineering and Surveying throughout the months of June and July 2010. Additional survey data was collected by Coffey Engineering and Surveying on August 26, 2011 and September 12, 2011. Survey notes are located in Appendix B. During the survey data collection, photos were obtained of each of the structures surveyed, and the size, material, and overall maintenance condition was noted. A copy of the photos and notes obtained is located in Appendix C. 2.4.2 Geotechnical Investigation A geotechnical investigation of the North Laramie study area was performed by Terracon to determine soil strata within the basin. The geotechnical engineering report presents the results of the subsurface exploration and provides geotechnical recommendations concerning drainage and slope stability. A copy of the Geotechnical Report is located in Appendix D. As discussed in the geotechnical report, groundwater was encountered at depths of 6 to 11 feet below the ground surface. In agreement with this statement, local staff has verified that prior to development a small channel ran along what now is Reynolds Street. Also verifying this statement, the groundwater level appears to be evident in lower basin detention ponds after a rain event. 2.5 Design Procedures Design procedures and parameters used in the study follow those recommended by the City of Laramie in the Request for Proposal for the North Laramie Drainage Master Plan. Computer models used in the study include Colorado Urban Hydrograph Procedure (CUHP) 2005 version 1.3.3 (Urban Drainage and Flood Control District, 2010) and (XP Software, 2010). ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 4 3.0 STUDY AREA DESCRIPTION 3.1 Location The study area is approximately four square miles located within the City of Laramie, Albany County, Wyoming. It is generally located within the area bounded by 45th Street on the east, north of the Jacoby Golf Course; north of the University of Wyoming campus; north of Ivinson Street; and bounded on the west by Union Pacific Railroad. See Figure 1 below. Figure 1: Location Map 3.2 Existing Outfalls The North Laramie study area has two outfalls at a common location at the northwest corner of the site and one outfall at the southwest corner of the site. See Figure 1, above, for outfall locations. The systems outfall into drainage ditches and eventually into the Laramie River, which is located parallel to the west boundary of the study area and flows north. In this report, the three systems will be commonly referred to as the Curtis Street system, the Reynolds Street system and the LaBonte system. 3.3 Flood History The North Laramie area can generally be divided into two halves, with the basins east of 15th Street referred to as “upstream” and the basins west of 15th Street referred to as As evidenced during the public meetings, North Laramie has experienced flooding within recent years. Stakeholders within the neighborhood have noted flooding along Reynolds Street and Curtis Street, as well as localized low spots within the area. It was also noted that certain detention facilities in the portions of the basin have reached maximum volume during many rainfall events. A majority of the flooding appears to occur within the basins near major trunk lines, though many localized spots were discussed during the public meetings. Curtis and Reynolds Outfall LaBonte Outfall Laramie River ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 5 3.4 Land Characteristics Topography within the study area is characterized as generally flat terrain at the end (west end) of the site near the Laramie River and moderate slopes upstream. Vegetation in the study area consists of mostly irrigated turf areas due to urbanization, however in the upper portions of the study the historic vegetation is shown as prairie with minimal coverage. Soils within the study area are primarily Hydrologic Soils Group B interspersed with Hydrologic Soils Group C and D, as show in Figure 5. Soil information within the study area was obtained using the Natural Resources Conservation Service (NRCS) Soil Survey Geographic (SSURGO) Database (NRCS, 2007). 3.5 Land Use The study area currently includes medium density residential, commercial, and industrial development in the southwest portion of the site; low density residential development in the southeast portion of the site; and is mostly undeveloped along the north boundary of the site. Current percent imperviousness for on‐site areas was determined using the City of Laramie existing Zoning Map (City of Laramie, 2010), shown in Figure 6. Projected percent impervious for the study area was determined using a Future Land Use map created as part of the Laramie Comprehensive Plan adopted by the City Council on May 30, 2003 (City of Laramie, 2003), shown in Figure 7. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 6 4.0 HYDROLOGIC MODEL 4.1 General Flood Peaks and hydrographs for the study area were determined using calibrated to CUHP for the 100‐year storm event. AutoCad Civil 3D and ArcInfo GIS were used to identify basin parameters required for CUHP and The CUHP calibration input is in Appendix E. The Detention Pond Calculations are found in Appendix F. Input and Output data from for both the existing and future model are in Appendix G and H, respectively. 4.2 Rainfall Data Rainfall data for three weather stations near the study area was obtained from the University of Wyoming Water Resources Data System (WRDS). See Figure 8 for the location of the three rain gage locations. Data received was 24‐hour rainfall depths from 1970 to present for two of the stations and from 1998 to present for the third station. The data was evaluated for each of the stations and 24‐hour point rainfall depths for the 10‐, and 25‐year storm event were calculated. An insufficient amount of data was collected to determine the 100‐year storm event rainfall depth. The overall lack of data points reduces the confidence in the larger storm events. To determine the 24‐ hour point rainfall depths for the study area, the point rainfall depth values from each of the stations were weighted based on their distance from the study area. Appendix I shows the values for each station. The calculated 24‐hour point rainfall depths were compared to National Oceanic and Atmospheric Administration (NOAA) values calculated from NOAA Atlas Volume II‐Wyoming for the City of Laramie (NOAA 1973). Table 1 below shows a comparison of the 24‐hour point rainfall depths. Table 1: Weather Station Data vs. NOAA Atlas Data for 24‐hour Point Rainfall Depths Design Storm Weighted Average of Weather Station Data (inches) NOAA (inches) 2‐year 1.1 1.2 5‐year 1.6 1.6 10‐year 2.1 1.8 25‐year 2.1 2.2 100‐year 2.6 The 24‐hour point rainfall data from WRDS was comparable to the NOAA Atlas values, and given the limited data available, it was concluded that the current NOAA values are a more accurate representation. Therefore, one‐hour point rainfall values from the NOAA Atlas were used for the hydrologic model. The values used are shown in Table 2. A comparison between the NOAA atlas and the latest City of Laramie publication shows that the NOAA value used for the 100‐year design storm is higher (0.1 inches), and therefore more conservative, than the 100‐year rainfall intensity used in the Informational Bulletin #2 of the City of Laramie Community Development Department – Code Administration Division. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 7 Table 2: NOAA 1‐hour Point Rainfall Depths Design Storm Point Rainfall Depth (inches) 2‐year 0.6 5‐year 0.9 10‐year 1.1 100‐year 1.9 4.3 and CUHP Parameters CUHP was used to determine two‐hour precipitation values for the 10‐, and 100‐year storm events. Because of input requirements specific to CUHP, the one‐hour point rainfall depths shown in Table 2 are distributed over two hours in five minute increments. The precipitation distribution depths, shown in Table 3 below, were input into the hydrologic model. Table 3: 2‐hour Precipitation Distribution Depths from CUHP Time (minutes) 2‐year (inches) 5‐year (inches) 10‐year (inches) 100‐year (inches) 0:05 0.012 0.018 0.022 0.019 0:10 0.024 0.033 0.041 0.057 0:15 0.050 0.078 0.090 0.087 0:20 0.096 0.138 0.165 0.152 0:25 0.150 0.225 0.275 0.266 0:30 0.084 0.117 0.132 0.475 0:35 0.038 0.052 0.062 0.266 0:40 0.030 0.040 0.047 0.152 0:45 0.018 0.032 0.042 0.118 0:50 0.018 0.032 0.035 0.095 0:55 0.018 0.027 0.035 0.076 1:00 0.018 0.027 0.035 0.076 1:05 0.018 0.027 0.035 0.076 1:10 0.012 0.027 0.035 0.038 1:15 0.012 0.023 0.035 0.038 1:20 0.012 0.020 0.028 0.023 1:25 0.012 0.020 0.021 0.023 1:30 0.012 0.020 0.021 0.023 1:35 0.012 0.020 0.021 0.023 1:40 0.012 0.014 0.021 0.023 1:45 0.012 0.014 0.021 0.023 1:50 0.012 0.014 0.021 0.023 1:55 0.006 0.014 0.019 0.023 2:00 0.006 0.012 0.014 0.023 2:05 0.000 0.000 0.000 0.000 Subbasin catchment parameters, including area, basin length, slope and distance to centroid were identified using recent topographic mapping provided by the City of Laramie. 44 subbasins were delineated within the study area, shown in both Figure 9a and Figure 9b. Area, length, and slope measurements were obtained using GIS. A routing schematic for these basins is shown in Figures 10a through 10d. Areas for each of the hydrologic soil groups within each of the subbasins were determined using GIS. Weighted soil infiltration parameters, including initial and final infiltration rates and decay ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 8 coefficients, were calculated for each of the basins using the soil infiltration parameters listed in Table 4. Note that infiltration rates were estimated in the geotechnical investigation using the Hazen equation. Comparing the results of the geotechnical investigation and the values recommended by the Urban Drainage and Flood Control District (UDFCD) showed that the recommended infiltration parameters are more conservative and were therefore used for this study. Table 4: Soil Infiltration Parameters SCS Soil Infiltration (inches/hour) Decay Type Fi Fo Coefficient B 4.5 0.6 0.0018 C/D 3 0.5 0.0018 The type and density of land use defines the magnitude of percent impervious parameters used in the hydrologic model. Percent impervious used for each of the existing land use types and future land use types are listed in Table 5 and Table 6, respectively, below. Weight percent impervious was determined for each of the subbasins using GIS. In some instances, the weighted future percent impervious was lower than the existing percent impervious, due to the limited accuracy of the future land use map. In these instances, the existing percent impervious was used for the future percent impervious. Table 5: Percent Impervious for Existing Land Uses in Study Area Existing Land Use Percent Impervious Undeveloped 2 Low Density Residential 40 Medium Density Residential 60 Medium Density Residential w/ Independent Mobile Homes 60 Multifamily 75 Neighborhood Business 80 General Business 85 Limited Business 85 Industrial 90 Commercial Wholesale 95 Table 6: Percent Impervious for Future Land Uses in Study Area Future Land Use Percent Impervious Agriculture 2 Park/ Open Space 5 Auto‐Urban Residential 40 Suburban Residential 40 Urban Residential 40 Public/ Institutional 50 Urban University 50 Auto‐Urban Multi‐Family 75 Industrial 90 Auto‐Urban Commercial 95 Suburban Commercial 95 Urban Commercial 95 ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 9 Catchment width parameters were calculated using, W =Lc[2‐(Ai+1‐Ai)/At] (Huber et al., 1984) Where Lc= length of the channel, Ai= area on the ith side of the channel, and At = the total area of the catchment. Most conveyance elements were simulated with a main element and an overflow element. Following recommendations in the UDSWM manual (Boyle Engineering Corp., 1985), and in accordance with UDFCD recommendations, coefficients for overflow conveyance elements were increased by 25 percent to yield more accurate, dependable results. Two types of overflow conveyance elements were used within the catchments; a grassed channel, and a street. Typical parameters used for each of the conveyance elements are shown in Table 7 below. Table 7: Typical Conveyance Element Parameters Depth (feet) Side Slopes H:V Manning n Bottom Width (feet) Pipe Concrete 0.013 HDPE 0.011 Channel Main 3 3:1 0.044* 5 Overflow 10:1 0.056* Street Main 0.5 0.020* 45 Overflow 1 10:1 0.044* *increased by 25% 4.4 Calibration Hydrographs produced by are calibrated to CUHP hydrographs for the 100‐year event using two catchments within the study area. Hydrograph model calibration is an iterative procedure of parameter evaluation and refinement used to compare simulated and observed values to ensure realistic results. Flood peak calibration in cubic feet per second (cfs) is summarized on Table 8 below. Flood peak and hydrograph calibration was achieved by multiplying the catchment width parameters for all catchments by 1.3. This multiplication factor was applied to the catchment width parameter for all other storm events. For future development within the North Laramie basin, we recommend using this model or requiring that the model used is calibrated to yield the same results as this model. Table 8: Flood Peak Calibration, to CUHP Flood Peak (cfs) Percent different from CUHP Catchment CUHP Coefficient CL 150 174 15% CU 253 220 ‐16% ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 10 4.5 Street Capacity A typical urban street section was obtained from the City and used to determine street capacities. The Urban Typical Section with Curb, Gutter and Sidewalk used for modeling purposes is shown in Figure 2. Figure 2: Typical Urban Street Section For modeling purposes, it was assumed that the streets could carry a maximum of one foot of flow above the flow line during the 100‐year event. Figure 3 is a rating curve of Discharge vs. Slope. The maximum street capacity should be examined further in final design using City of Laramie design criteria that is to be produced in the future. Figure 3: Typical Urban Street Section Capacity Rating Curve 4.6 Detention Areas Eleven existing detention facilities were incorporated into the existing and future condition hydrologic models. Volumes were determined using the existing two‐foot contour interval topography provided by the City of Laramie. Outlet and spill crest information was collected by Coffey Engineering and Surveying throughout the months of June and July of 2010. See Table 9 for location and approximate volume of each of the detention areas. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 11 Table 9: Location and Approximate Volume of Detention Areas Node Name Location Approximate Volume (acre‐feet) 2122 (CM02) 10th Street and Beaufort Street 1.9 RM07 22nd Street and Reynolds Street 3.2 2407 (RM02) 22nd Street and Binford Street 7.8 RU05 30th Street and Reynolds Street (NE) 1.3 2634 (RU04) 30th Street and Reynolds Street (SE) 11.7 2490 (RM03) Bath Street and Reynolds Street 4.4 RM08 22nd Street and Nighthawk Drive 7.4 RM06 17th Street and Reynolds Street 3.7 LM01 15th Street and Harney Street (NE) 1.4 LM02 15th Street and Harney Street (SE) 1.4 LL10 LaBonte Park (9th Street and Canby Street) 20.0 4.7 Addition of LaBonte Subbasins The original North Laramie Drainage Master Plan did not contain subbasins LL05 through LL09, located just south of LaBonte Park. At the 75% submittal, it was recommended to the City of Laramie to add these subbasins to the study. LaBonte Park pond appeared to be the best opportunity to reduce peak flows in the lower portions of the basin. For the hydrologic analysis of these additional subbasins, the delineation for these subbasins was adapted from the West Campus Drainage Study and Recommended Improvements Report for City of Laramie prepared by Nolte Associates, Inc. and dated June 2009. The remainder of the basin characteristics were calculated and determined using the same procedure as discussed in the beginning of this section. The model was updated to include these six additional subbasins. Since LaBonte Park pond does not have one specific outfall and it uses a few of the inflow pipes as pond outfalls, LaBonte Park pond was modeled as a retention pond with no outlet except an overflow weir. 4.8 Results Flood peaks for the 10‐, and 100‐year flood events for each of the subbasins are summarized in Tables 10 and 11. Table 12 shows the percent increase of flows from existing to future percent impervious values, calculated by taking the Future Flow minus the Existing Flow and then the difference divided by the Existing Flow. A significant increase in flows occurs in all subbasins which are currently undeveloped. These are primarily located in the upstream portion of the North Laramie basin. The existing percent imperviousness in these subbasins is 2% allowing many flows to infiltrate prior to leaving the basin. The significant increase in flows is caused by the significant increase in percent impervious upon development of these subbasins. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 12 Table 10: Existing Flood Peaks Subbasin Percent Impervious 2‐year (cfs) 5‐year (cfs) 10‐year (cfs) 100‐year (cfs) CL01 2 2 3 4 66 CL02 2 3 4 5 70 CL03 23 27 40 49 106 CL04 58 50 78 96 184 CL05 52 76 117 144 273 CL06 67 56 93 118 228 CL07 62 46 71 88 166 CL08 53 38 58 71 146 CL09 5 2 4 4 52 CM01 2 3 5 6 79 CM02 19 42 63 78 209 CU01 2 10 15 18 256 LL01 73 83 133 166 320 LL02 73 66 110 140 274 LL03 61 28 43 53 101 LL04 64 52 81 101 190 LL05 71 17 28 35 66 LL06 75 30 47 59 111 LL07 75 79 124 155 300 LL08 87 39 63 82 170 LL09 86 56 95 122 245 LL10 61 22 35 44 90 LM01 75 26 41 51 105 LM02 75 55 84 104 216 RL01 66 40 63 79 147 RL02 71 54 89 115 236 RL03 93 38 62 80 168 RM01 47 16 25 30 58 RM02 40 45 71 88 170 RM03 40 34 51 63 142 RM04 35 20 31 37 90 RM05 63 43 66 81 181 RM06 74 79 125 156 299 RM07 34 27 40 49 111 RM08 27 25 38 47 104 RM09 45 30 46 57 107 RM10 2 2 3 4 64 RM11 56 50 77 96 183 RU01 31 47 71 88 207 RU02 40 33 49 61 130 RU03 41 24 37 46 94 RU04 40 40 60 74 190 RU05 35 15 22 27 71 RU06 45 82 126 156 302 ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 13 Table 11: Future Flow Peaks Subbasin Percent Impervious 2‐year (cfs) 5‐year (cfs) 10‐year (cfs) 100‐year (cfs) CL01 40 42 65 80 158 CL02 52 56 88 109 215 CL03 47 51 78 97 186 CL04 58 50 78 96 184 CL05 52 76 117 144 273 CL06 67 56 93 118 228 CL07 62 46 71 88 166 CL08 70 49 75 92 183 CL09 92 39 60 75 142 CM01 45 67 102 126 234 CM02 40 86 130 160 319 CU01 43 177 277 345 691 LL01 73 83 133 166 320 LL02 73 66 110 140 274 LL03 61 28 43 53 101 LL04 64 52 81 101 190 LL05 71 17 28 35 66 LL06 75 30 47 59 111 LL07 75 79 124 155 300 LL08 87 39 63 82 170 LL09 91 58 98 126 255 LL10 61 22 35 44 90 LM01 75 26 41 51 105 LM02 75 55 84 104 216 RL01 66 40 63 79 147 RL02 71 54 89 115 236 RL03 93 38 62 80 168 RM01 47 16 25 30 58 RM02 40 45 71 88 170 RM03 42 36 54 66 148 RM04 37 21 32 40 94 RM05 63 43 66 81 181 RM06 74 79 125 156 299 RM07 38 30 45 55 121 RM08 40 36 55 68 141 RM09 45 30 46 57 107 RM10 40 42 65 79 150 RM11 56 50 77 96 183 RU01 40 59 91 112 249 RU02 40 33 49 61 130 RU03 41 24 37 46 94 RU04 40 40 60 74 190 RU05 39 17 25 31 76 RU06 45 82 126 156 302 ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 14 Table 12: Percent Increase of Flows from Existing to Future Subbasin 2‐year 5‐year 10‐year 100‐year CL01 2000% 2067% 1900% 139% CL02 1767% 2100% 2080% 207% CL03 89% 95% 98% 75% CL04 0% 0% 0% 0% CL05 0% 0% 0% 0% CL06 0% 0% 0% 0% CL07 0% 0% 0% 0% CL08 29% 29% 30% 25% CL09 1850% 1400% 1775% 173% CM01 2133% 1940% 2000% 196% CM02 105% 106% 105% 53% CU01 1670% 1747% 1817% 170% LL01 0% 0% 0% 0% LL02 0% 0% 0% 0% LL03 0% 0% 0% 0% LL04 0% 0% 0% 0% LL05 0% 0% 0% 0% LL06 0% 0% 0% 0% LL07 0% 0% 0% 0% LL08 0% 0% 0% 0% LL09 4% 3% 3% 4% LL10 0% 0% 0% 0% LM01 0% 0% 0% 0% LM02 0% 0% 0% 0% RL01 0% 0% 0% 0% RL02 0% 0% 0% 0% RL03 0% 0% 0% 0% RM01 0% 0% 0% 0% RM02 0% 0% 0% 0% RM03 6% 6% 5% 4% RM04 5% 3% 8% 4% RM05 0% 0% 0% 0% RM06 0% 0% 0% 0% RM07 11% 13% 12% 9% RM08 44% 45% 45% 36% RM09 0% 0% 0% 0% RM10 2000% 2067% 1875% 134% RM11 0% 0% 0% 0% RU01 26% 28% 27% 20% RU02 0% 0% 0% 0% RU03 0% 0% 0% 0% RU04 0% 0% 0% 0% RU05 13% 14% 15% 7% RU06 0% 0% 0% 0% ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 15 5.0 PRELIMINARY IDENTIFICATION OF FLOOD PRONE AREAS One major cause of flooding in the North Laramie basin is caused by a backwater effect; most significantly in low slope areas. Backwater or ponding increases water surface elevations and results in a reduction in hydraulic head between and upstream areas. This reduces the ability of the stormwater conveyance system to quickly pass stormwater When the capacity of the stormwater conveyance system is limited by a small change in hydraulic head, the stormwater cannot be directly conveyed and the model “ponds” this water. Consequently, this water is “stored” or ponded in the streets and neighborhoods until it can be removed by gravity flow and this ponded water creates flooding in the neighborhood. This cause of flooding predominately occurs along the low slope areas near the outfall. A second major cause of flooding in the study area is inadequate conveyance to transport the peak flows. Under these cases, the model “stores” waters upstream of the reach with inadequate conveyance until it has the capacity to transport the flows. This flooding can occur anywhere in the catchment, but it is most common when flow conveyance is limited by storm sewer capacity and where the discharge from a number of catchments combines and overwhelms the carrying capacity of the streets, channels, and storm sewers To simplify the discussion of flood prone areas, the major stormwater conveyance routes in the study were divided into reaches. Reaches are identified in Figure 11. Tables 13 and 14 identify flood prone areas for the 10‐, and 100‐year events, for the existing and future conditions, respectively, while the below discussion focuses on both the minor (2‐year) and major (100‐year) events. The analysis incorporated the best available information on existing detention areas, but assumes no new detention areas for future conditions. 5.1 Existing Percent Imperviousness Refer to Figure 12 for location of flooding areas for the 2‐ and 100‐year events with the existing percent imperviousness. A majority of these local flooding areas were also identified by local citizens during the public meetings described in Section 2.3. Reach 1, located in the northern part of the study area, shows no flooding areas for the 2‐year event. Minor flooding is observed along Beaufort Street between 9th Street and 10th Street during the 100‐year event. Reach 2, located in the northwest part of the study area, shows flooding at the intersection of Downey Street and 9th Street during the 2‐year event. During the 100‐year event, 9th Street between Curtis Street and Downey Street will flood. Reach 3, located in the eastern section of the study area, will experience no significant flooding during the 2‐year event. Reynolds Street between 22nd Street and 30th Street, as well as 30th Street between Grays Gable Road and Reynolds Street, will experience flooding during the 100‐year event. Reach 4 is located north of Reynolds Street along 22nd Street. No significant flooding will be experienced in this reach during the 2‐year event. During the 100‐year event, flooding is anticipated at the intersection of 22nd Street and Reynolds Street. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 16 Reach 5 is located south of Reynolds Street along 22nd Street. No significant flooding will be experienced in this reach during the 2‐year event. Flooding will be experienced from Hancock Street to Reynolds Street along 22nd Street during the 100‐year event. Reach 6 receives runoff from Reaches 3, 4, and 5 which influences flooding in the Reach. During the two year event, flooding is anticipated in the lower part of the Reach, bounded on the west and east by 4th Street and 9th Street, and bounded on the north and south by Reynolds Street and Hancock Street. During the 100‐year event, flooding is anticipated in the reach during the 2‐year event and along Reynolds Street from 9th Street to the west to 22nd Street to the east. Flooding in Reach 7, located in the southwest part of the Study area, is strongly influenced by the multifamily development in the upper part of the reach which causes large flood peak discharges. Flooding is anticipated all along the Reach, roughly a diagonal between the intersection of Shield Street and 9th Street to the intersection of Harney Street and 15th Street during the 2‐ and 100‐year event. Reach 8 is the outfall area and receives runoff from all Reaches in the Study area. Reach 8 is strongly influenced by backwater effects. Due to topographic conditions, stormwater flows are directed in two paths at the intersection of Curtis Street and 7th Street, one path located along Curtis Street, the other flowing to the southwest towards Hancock Street. Once the storm sewer in Curtis Street is filled to capacity, stormwater flows tend to follow the southwestern path. During the 2‐ year event, lands south of Curtis Street are flooded. During the 100‐year event, all lands in the Reach are flooded. Reach 9, located south of LaBonte Park, is independent of all other reaches. Flooding at the intersection of 3rd Street and Canby Street will occur in this reach during a 2‐year event. During a 100‐year event, flooding will occur at the intersections of 6th Street and Canby Street and 3rd Street and Canby Street and along 3rd Street, 6th Street, Canby Street and Harney Street west of 3rd Street. Flooding is this reach is a result of extremely low slopes within the reach. 5.2 Future Percent Imperviousness Refer to the Figure 13 for location of flooding areas for the 2‐ and 100‐year events with future percent imperviousness. Future condition flooding is similar to existing condition flooding. The only exception is additional flooding in Reach 2. In Reach 2, flooding will appear along 9th Street between Curtis Street and Downey Street. For the 100‐year event, flooding is anticipated on 9th Street between Curtis Street and Beaufort Street as existing conditions but will extend north of Beaufort Street along 9th Street to Seeton Street. 5.3 Existing Detention Ponds The hydrologic analysis indicates some existing detention ponds successfully detain the 100‐year event while others do not. Ponds working properly include those identified as nodes RM03 (2490), RM02, RM07 and RM08. Ponds overtopping during the 100‐year event include RU04 (2634), RU05, RM06, LM01, LM02, CM02 (2122) and LL10. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 17 Table 13: North Laramie Problem Areas ‐ Existing Percent Impervious Reach Location Major Areas, Streets 2‐year event 5‐year event 10‐year event 100‐year event 1 Northeast Undeveloped upstream areas, Beaufort St. No significant flooding No significant flooding No significant flooding Along Beaufort St. between 9th St. and 10th St. 2 Northwest 9th St., Curtis St. Intersection Downey St. and 9th St. Along 9th St. between Curtis St. and Beaufort St. Along 9th St. between Curtis St. and Seeton St. Along 9th St. between Curtis St. and Seeton St. 3 Southeast Grays Gable Road, Alta Vista Drive, 30th St. No significant flooding No significant flooding Intersection 30th St. and Reynolds St. Along 30th St. between Grays Gable Road Road and Reynolds St. Reynolds St. Along Reynolds St. between 22nd St. and 30th St. 4 North Central 22nd St. north of Reynolds St. No significant flooding No significant flooding No significant flooding Intersection 22nd St. and Reynolds St. 5 South Central 22nd St. south of Reynolds St. No significant flooding Near Hancock St. and 22nd St. Near Hancock St. and 22nd St. Hancock St. to Reynolds St. 6 Central Reynolds St., 9th St., and Hancock St. Along 9th St. between Reynolds St. and Hancock St. Along 9th St. between Reynolds St. and Hancock St. Along 9th St. between Reynolds St. and Hancock St. Along Reynolds St. between 22nd St. and 9th St. Along Hancock St. between 9th St. and 4th St. Near 15th St. and Reynolds St. Near 15th St. and Reynolds St. Along 9th St. between Reynolds St. and Hancock St. Along Hancock St. between 9th St. and 4th St. Along Hancock St. between 9th St. and 4th St. Along Hancock St. between 9th St. and 4th St. 7 South Harney St., 14th St., Gibbon St., 11th St. Along Harney St. between 14th St. and 15th St. Along Harney St. between 14th St. and 15th St. Along Harney St. between 14th St. and 15th St. Along Harney St. between 14th St. and 15th St. Canby, 9th St., Hancock St. Along 14th St. between Harney St. and Gibbon St. Along 14th St. between Harney St. and Gibbon St. Along 14th St. between Harney St. and Gibbon St. Along 14th St. between Harney St. and Gibbon St. Along Gibbon St. between 14th St. and 11th St. Along Gibbon St. between 14th St. and 11th St. Along Gibbon St. between 14th St. and 11th St. Along Gibbon St. between 14th St. and 11th St. Along 11th St. between Gibbon St. and Canby St. Along 11th St. between Gibbon St. and Canby St. Along 11th St. between Gibbon St. and Canby St. Along 11th St. between Gibbon St. and Canby St. Along Canby St. between 11th St. and 9th St. Along Canby St. between 11th St. and 9th St. Along Canby St. between 11th St. and 9th St. Along Canby St. between 11th St. and 9th St. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 18 Reach Location Major Areas, Streets 2‐year event 5‐year event 10‐year event 100‐year event 7 South Canby, 9th St., Hancock St. Along 9th St. between Canby St. and Shield St. Along 9th St. between Canby St. and Shield St. Along 9th St. between Canby St. and Shield St. Along 9th St. between Canby St. and Shield St. From Shield St. and 9th St. to 4th St. and Hancock St. From Shield St. and 9th St. to 4th St. and Hancock St. From Shield St. and 9th St. to 4th St. and Hancock St. From Shield St. and 9th St. to 4th St. and Hancock St. 8 West, Outfall Curtis St. from 7th St. to 3rd not flooded Curtis St. from 7th St. to 3rd not flooded Curtis St. from 7th St. to 3rd not flooded Entire area flooded Entire area to south of Curtis St. flooded Area south of Curtis St. flooded Area south of Curtis St. flooded Area south of Curtis St. flooded 9 South of LaBonte Park Canby St., Harney St. Outfall Intersection of 3rd St. and Canby St. Flooded Intersection of 3rd St. and Canby St. Flooded Along Canby St. from 3rd St. to 6th St. Entire area flooded Intersection of 6th St. and Canby St. Flooded Along 6th St. from Lewis St. to Canby St. Along 3rd St. between Canby St. and Harney St. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 19 Table 14: North Laramie Problem Areas ‐ Future Percent Impervious Reach Location Major Areas, Streets 2‐year event 5‐year event 10‐year event 100‐year event 1 Northeast Undeveloped upstream areas, Beaufort St. No significant flooding Along Beaufort St. between 9th St. and 10th St. Along Beaufort St. between 9th St. and 10th St. Along Beaufort St. between 9th St. and 10th St. 2 Northwest 9th St., Curtis St. Along 9th St. between Curtis St. and Downey St. Along 9th St. between Curtis St. and Beaufort St. Along 9th St. between Curtis St. and Seeton St. Along 9th St. between Curtis St. and Seeton St. 3 Southeast Grays Gable Road, Alta Vista Drive, 30th St. No significant flooding No significant flooding Intersection 30th St. and Reynolds St. Along 30th St. between Grays Gable Road and Reynolds St. Reynolds St. Along Reynolds St. between 22nd St. and 30th St. 4 North Central 22nd St. north of Reynolds St. No significant flooding No significant flooding No significant flooding Intersection 22nd St. and Reynolds St. 5 South Central 22nd St. south of Reynolds St. No significant flooding Near Hancock St. and 22nd St. Near Hancock St. and 22nd St. Hancock St. to Reynolds St. 6 Central Reynolds St., 9th St., and Hancock St. Along 9th St. between Reynolds St. and Hancock St. Along 9th St. between Reynolds St. and Hancock St. Along 9th St. between Reynolds St. and Hancock St. Along Reynolds St. between 22nd St. and 9th St. Along Hancock St. between 9th St. and 4th St. Near 15th St. and Reynolds St. Near 15th St. and Reynolds St. Along 9th St. between Reynolds St. and Hancock St. Along Hancock St. between 9th St. and 4th St. Along Hancock St. between 9th St. and 4th St. Along Hancock St. between 9th St. and 4th St. 7 South Harney St., 14th St., Gibbon St., 11 th St. Along Harney St. between 14th St. and 15th St. Along Harney St. between 14th St. and 15th St. Along Harney St. between 14th St. and 15th St. Along Harney St. between 14th St. and 15th St. Canby, 9th St., Hancock St. Along 14th St. between Harney St. and Gibbon St. Along 14th St. between Harney St. and Gibbon St. Along 14th St. between Harney St. and Gibbon St. Along 14th St. between Harney St. and Gibbon St. Along Gibbon St. between 14th St. and 11th St. Along Gibbon St. between 14th St. and 11th St. Along Gibbon St. between 14th St. and 11th St. Along Gibbon St. between 14th St. and 11th St. Along 11th St. between Gibbon St. and Canby St. Along 11th St. between Gibbon St. and Canby St. Along 11th St. between Gibbon St. and Canby St. Along 11th St. between Gibbon St. and Canby St. Along Canby St. between 11th St. and 9th St. Along Canby St. between 11th St. and 9th St. Along Canby St. between 11th St. and 9th St. Along Canby St. between 11th St. and 9th St. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 20 Reach Location Major Areas, Streets 2‐year event 5‐year event 10‐year event 100‐year event 7 South Canby, 9th St., Hancock St. Along 9th St. between Canby St. and Shield St. Along 9th St. between Canby St. and Shield St. Along 9th St. between Canby St. and Shield St. Along 9th St. between Canby St. and Shield St. From Shield St. and 9th St. to 4th St. and Hancock St. From Shield St. and 9th St. to 4th St. and Hancock St. From Shield St. and 9th St. to 4th St. and Hancock St. From Shield St. and 9th St. to 4th St. and Hancock St. 8 West, Outfall Curtis St. from 7th St. to 3rd not flooded Curtis St. from 7th St. to 3rd not flooded Curtis St. from 7th St. to 3rd not flooded Entire area flooded Entire area to south of Curtis St. flooded Area south of Curtis St. flooded Area south of Curtis St. flooded Area south of Curtis St. flooded 9 South of LaBonte Park Canby St., Harney St. Outfall Intersection of 3rd St. and Canby St. Flooded Intersection of 3rd St. and Canby St. Flooded Along Canby St. from 3rd St. to 6th St. Entire area flooded Intersection of 6th St. and Canby St. Flooded Along 6th St. from Lewis St. to Canby St. Along 3rd St. between Canby St. and Harney St. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 21 6.0 ANALYSIS OF ALTERNATIVE IMPROVEMENTS 6.1 General The hydrologic analysis indicated development in the study area will increase the magnitude of flood peaks for basins that are currently undeveloped. The hydrologic analysis also indicated that the existing system floods under the existing conditions. The three major areas of potential flooding identified in the North Laramie drainage area are:  Increased discharge due to development in the north and east (Curtis Street system);  Upstream capacity during large events (especially in the Reynolds Street system); and  capacity/backwater effect toward all outfalls. The additional LaBonte subbasins described in Section 4.7 are not included in this analysis as they were added later in the study. 6.2 Qualitative Analysis of Alternative Improvements In response to the three major areas of potential flooding, a scoring matrix was developed to qualitatively analyze possible solutions. See Appendix J for the Conceptual Solution Scoring Matrix. The matrix involved determining all possible solutions to each of the three major areas of potential flooding mentioned above and rating each of the solutions based on costs, maintenance, proven acceptance, and hydrologic impact on the minor and major storm events. Each of the categories was scored according to the effectiveness within the North Laramie project area using a for positive impacts, for no impact and for negative impacts. The scores were completed independently by three team members. The scores were summed for an overall rating for each of the solutions. The solutions were then ranked, by problem, according to their overall score and the highest ranked solutions were chosen for the alternative improvements. It was noted that for the “Increased discharge due to development” and the “Upstream capacity during large events”, a potential solution for each by far out‐weighed the others in its positive impacts. Therefore, for these two major areas of potential flooding, one solution was used. The highest ranked solution for “Increased discharge due to development” was the requirement for detention within the basin upon future development. Note that Low Impact Development also ranked high and is encouraged within these basins to detain the smaller events to historic flows. However, detention will still be needed for large events. The highest ranked solutions for “Upstream capacity during large events” were to modify/optimize existing detention and, if necessary, provide additional detention. This would include modifying the existing outlet structure to release at historic rates for all storm events (full‐spectrum detention), enlarge existing ponds when possible and necessary, and add new detention ponds when possible and necessary. The four highest ranked solutions for capacity / backwater effect” were floodplain management/floodproofing, additional trunk line systems, upsize existing trunk line system, and providing regional detention. It was noted that floodplain management/floodproofing should be a part of all solutions in some manner and therefore was not included into the structural alternatives. The solutions for each of the three major areas of potential flooding were combined to form the following three alternative solutions to quantitatively analyze. The three alternatives are: ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 22 1. Require detention for future development, modify/optimize existing detention and add additional detention, upsize the existing trunk line storm sewer system and provide floodproofing where necessary. 2. Require detention for future development, modify/optimize existing detention and add additional detention, add additional trunk line storm sewer systems and provide floodproofing where necessary. 3. Require detention for future development, modify/optimize existing detention and add additional detention and provide regional detention, upsize existing trunk line storm sewer system and provide floodproofing where necessary. 6.3 Quantitative Analysis of Alternative Improvements The solutions for both “Increased discharge due to development” and “Upstream capacity during large events” are the same for all three alternatives; therefore, they were analyzed first and added to each base alternative model created. Design Criteria was used throughout all qualitative analyses. One foot of flow depth within the street was considered allowable and was checked with FlowMaster using normal depth for different slopes. A depth greater than one foot within the street was considered flooding. Pipe capacities were also checked with FlowMaster. 6.3.1 Upstream Improvements Upstream improvements include requiring detention for future development in undeveloped areas, modifying existing detention ponds, and adding new detention in developed areas. Figure 14 shows pond modifications and required detention for undeveloped areas. Subbasins CU01, CM01, CL01, CL02 and RM10 are currently undeveloped basins (existing percent impervious is For these subbasins, detention is required for all future development and release rates for the detention must not exceed existing or “historic” rates. It is recommended that these undeveloped areas release the 100‐year event at 10‐year “historic” release rates to help reduce the flooding in the lower portions of North Laramie. Assuming that these basins will release at “historic” rates after development, existing percent impervious was used in the base alternative model. Future regional detention for these subbasins was estimated using the SCS method and an estimated hydrograph using the 10‐year and 100‐year peak flow rate and the time of peak. The estimated regional detention volume for each of the ponds, for both 100‐year and 10‐year “historic” release rates, is listed in Table 15. Subbasins RU01, RM10, RM08, CM02 and CL03 are partially undeveloped. Local detention is also required for future development in these undeveloped areas, though each will need to be done on an individual basis and not on a regional level due to the existing grade of the basin and the existing development. For modeling purposes, existing percent impervious values were used for these basins as well. Table 15: Estimated Regional 100‐Year Detention Volumes for Undeveloped Subbasins Subbasin Estimated Regional Detention Volume 100‐yr Release Rate) (acre‐feet) Estimated Regional Detention Volume 10‐yr Release Rate) (acre‐feet) CU01 21.9 36.7 CM01 7.8 12.4 CL01 4.7 8.4 CL02 7.4 11.5 RM10 4.4 8.0 Each of the existing eleven detention ponds was optimized for full spectrum detention. Therefore, each pond was optimized to release at “historic rates” for all four storm events: 10‐ and 100‐ ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 23 year. Because development has already occurred in the subbasins in which these ponds are located, a historic release rate for each of the storm events was estimated. The four undeveloped subbasins, CU01, CM01, CL01 and CL02, were used to estimate the “historic” release rates. The existing flow rates and potential future flow rates for each of the four storm events were compared to determine the increase from existing to future flows. This increase for each of the storm events was averaged for each of the four undeveloped basins and a multiplier for each of the storm events was determined. This new multiplier was used to determine an acceptable release rate for each existing pond to mimic “historic” conditions. Each of the existing ponds was modeled separately to accurately model the optimized outlet without the influence of backwater. Existing detention ponds located in subbasins LM01, RU05, RM06, CM02 and LL10 were enlarged to their maximum potential volumes given land constraints and outlet and spill crest elevation constraints to help reduce flooding Table 16 shows the increase in volume for each pond. Table 16: Estimated Increase in Detention Volumes for Existing Detention Ponds Detention Pond Estimated Increase in Detention Volume (acre‐feet) LM01 1.1 RU05 1.7 RM06 1.6 CM02 2.9 After modifying/optimizing all existing ponds, flooding still occurred at 22nd Street and Reynolds Street. Existing detention ponds located in subbasins RU04 and RU05, were unable to reduce this flooding and could not be further enlarged due to site constraints. To remove this flooding issue, a new detention pond of approximately 10 acre‐feet was located on an undeveloped parcel of land located at the southwest corner of the intersection of 22nd Street and Reynolds Street in basin RM02. The additional pond RM02, the modification/optimization of the existing ponds, plus the required detention for future developments removed the two major areas of potential flooding described above. Note that ponds CM02, LM02 and the new pond RM02 overtop during normal 100‐year event operations and do not cause flooding within the area based on the Design Criteria stated. Also note that basin RU02, RU03, and RU06 cause potential flooding along Grays Gable Road and 30th Street. The new pond located in RM02 is sized to capture this flow and remove flooding There is a current inlet diversion system at the end of Basin RU06 that diverts flow to the Jacoby Golf Course, which if possible, could be increased to remove flow and flooding from Grays Gable Road. This removal of flow may decrease the size of the new pond RM02 depending on the amount of flow diverted to the Jacoby Golf Course. For this study, it was assumed no flow was diverted. 6.3.2 Alternative 1: Upsize Existing Trunk Line Sewers In addition to the upstream improvements discussed above, Alternative 1 involves upsizing the existing trunk line sewers in the area of the North Laramie drainage basin as shown in Figure 15. In this alternative, pipe sizes would be increased so that streets met the Design Criteria stated. Flat slopes (less than 0.5%) in the area limit the size of pipe available due to cover. Alternative 1 requires increases to the trunk line sewer system of the Curtis Street system from ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 24 Beaufort Street and 9th Street to the outfall, increases to the trunk line sewer system of the Reynolds Street system from 15th Street and Reynolds Street to the outfall, and increases to the trunk line sewer system of the LaBonte system from 11th and Gibbon to the Reynolds Street system. The results are an 8’x8’ reinforced concrete box culvert (RCBC) at the outfall of the Curtis Street system which would convey approximately 800 cfs, a 6’x20’ RCBC at the outfall of the Reynolds Street system which would convey approximately 1000 cfs, and a 5’x10’ concrete box at the connection of the LaBonte system to the Reynolds Street system. Alternative 1 removes the capacity / backwater effect” area of potential flooding. 6.3.3 Alternative 2: Additional Trunk Line Sewers As illustrated in Figure 16, Alternative 2 consists of adding additional interceptor trunk line systems which would remove flows from the Curtis Street and Reynolds Street systems and discharge the flows directly to the outfall. The Curtis Street system would be intercepted at 9th Street and Downey Street with a 6’x8’ RCBC that would remove 450 cfs from the system and convey the flows directly to the outfall channel west of Highway 287 at the northwest corner of the North Laramie drainage basin. The trunk line system would run west along Downey Street to 7th Street and then run south along 7th Street to Mitchell Street; west along Mitchell Street to 3rd Street, south on 3rd to Superior Court west, and then north on Superior Court to the outfall. The additional trunk line sewer system interceptor would prevent flooding from occurring of 9th Street and Downey Street for the remainder of the existing Curtis Street system. However, potential flooding would occur upstream of 9th Street to Beaufort Street. The LaBonte system would be intercepted at 9th Street and Shield Street with a 6’x9’ RCBC which would convey approximately 450 cfs directly to the outfall channel. The interceptor system would run west along Shield Street to the railroad tracks and north along the railroad tracks to the outfall. Removing flow from the Reynolds Street system would prevent flooding of the existing system along Shield Street and 4th Street, but the remainder of the LaBonte system would have potential flooding during large storm events upstream of 11th Street to Gibson Street. Though removing a majority of the LaBonte system from the Reynolds Street system improves the potential flooding situation, the Reynolds Street system still has potential flooding and no other alternative path to take for a trunk line. This alternative does not remove the capacity / backwater effect” area of potential flooding, but does improve the situation. 6.3.4 Alternative 3: LaBonte Discharge and Upsize Trunk Line Sewers It was anticipated that Alternative 3 would consist of regional detention within the area of North Laramie. However, there is no undeveloped land available for regional detention. Therefore, Alternative 3 consists of utilizing the LaBonte Park pond as a retention or detention pond and discharging all of the 100‐year flow, approximately 700 cfs, upstream of 9th Street and Shield Street directly into the LaBonte Park pond through a 4’x20’ RCBC. As shown in Figure 17, Alternative 3 also consists of upsizing the Curtis Street system and Reynolds Street system. Alternative 3 would yield the same results as Alternative 1 for the Curtis Street system and would end with an 8’x8’ box culvert at the outfall of the system. The Reynolds Street system upstream of the LaBonte Park discharge would also yield the same results as Alternative 1. However, the LaBonte Park Pond discharge would reduce the size of the box culvert of the discharge from Alternative 1 to a 6’x12’ RCBC. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 25 This alternative does remove the capacity / backwater effect” area of potential flooding. 6.4 Cost Analysis of Alternative Improvements Cost estimates are presented in Tables 17 through 19 for the three alternatives. Alternative 1 includes modification of existing ponds, adding detention ponds, and upsizing existing storm sewers for a total estimated cost of $24,000,000. Alternative 2 modifies the existing ponds and adds detention ponds, but only adds additional trunk line sewers to the existing storm sewer system, for a total estimated cost of $13,900,000. Alternative 3 has an estimated total cost of $19,200,000 and includes modification of existing ponds, adding detention ponds, directing flows to LaBonte Park pond, and upsizing existing storm sewers. The cost estimates are divided into Storm Sewer, Detention, and Utility Relocation categories, and are intended to provide a basis for comparing the three alternatives. The construction cost estimates presented are based on construction unit costs for recently completed drainage projects in the Denver metro area, a bid tabulation database maintained by the UDFCD, and engineering judgment. Because of the unique sizes of the proposed reinforced concrete box culverts, a one‐foot wall, floor, and ceiling thickness and a $625 per cubic yard price for concrete was assumed. Construction cost estimates are increased by 20 percent to account for contingencies, engineering, administration, and legal fees. Costs were also increased by assuming a 5 percent traffic control component, 8 percent for mobilization/demolition, 5 percent for material remediation and disposal, and 20 percent for utility relocation. Land acquisition costs are not included in the estimate because the additional ponds are common to all alternatives, and because land values vary over time. The cost estimates included in this master plan are conceptual in nature and are to be used for comparative purposes only. All construction costs are presented in 2010 dollars, and no financing costs or phased construction alternatives are included. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 26 Table 17: Conceptual Cost Estimate for Alternative 1 Item No. Description Quantity Unit Unit Price Total Cost Traffic Control 1 LS $848,336 $848,336 Mobilization/Demolition 1 LS $1,357,337 $1,357,337 Material Management (environmental remediation and disposal) 1 LS $848,336 $848,336 Storm Sewer* 54" RCP 1442 LF $210 $302,820 60" RCP 3673 LF $230 $844,790 72" RCP 601 LF $265 $159,265 8'x8' RCBC 3342 LF $750 $2,506,500 7'x9' RCBC 750 LF $750 $562,500 6'x8' RCBC 1577 LF $650 $1,025,050 6'x20' RCBC 1976 LF $1,200 $2,371,200 5'x20' RCBC 1878 LF $1,150 $2,159,700 5'x10' RCBC 2171 LF $700 $1,519,700 5'x8' RCBC 1798 LF $600 $1,078,800 5'x16' RCBC 936 LF $975 $912,600 Sub‐Total $13,442,925 Detention Detention Volume 17.4 AC‐FT $40,000 $696,000 Sub‐Total $696,000 Utility Relocates Dry Utility Administration (20%) 1 LS $2,827,385 $2,827,785 Sub‐Total $2,827,785 Sub‐Total for Alternative $20,017,886 Contingency (20%) $4,004,144 Total For Alternative $24,000,000 *Box culvert sizes are height x width; assumes 1 foot slab thickness and $625/CY ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 27 Table 18: Conceptual Cost Estimate for Alternative 2 Item No. Description Quantity Unit Unit Price Total Cost Traffic Control 1 LS $490,110 $490,230 Mobilization/Demolition 1 LS $784,176 $784,368 Material Management (environmental remediation and disposal) 1 LS $490,110 $490,230 Storm Sewer 6'x9' RCBC 5970 LF $700 $4,179,000 6'x8' RCBC 5070 LF $650 $3,295,500 Sub‐Total $7,474,500 Detention Detention Volume 17.4 AC‐FT $40,000 $696,000 Sub‐Total $696,000 Utility Relocates Dry Utility Administration (20%) 1 LS $1,633,700 $1,634,100 Sub‐Total $1,634,100 Sub‐Total for Alternative $11,569,428 Contingency (20%) $2,313,886 Total For Alternative $13,900,000 *Box culvert sizes are height x width; assumes 1 foot slab thickness and $625/CY ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 28 Table 19: Conceptual Cost Estimate for Alternative 3 Item No. Description Quantity Unit Unit Price Total Cost Traffic Control 1 LS $676,100 $676,220 Mobilization/Demolition 1 LS $1,081,759 $1,081,951 Material Management (environmental remediation and disposal) 1 LS $676,100 $676,220 Storm Sewer 54" RCP 1442 LF $210 $302,820 60" RCP 3673 LF $230 $844,790 72" RCP 601 LF $265 $159,265 8'x8' RCBC 3342 LF $750 $2,506,500 7'x9' RCBC 750 LF $750 $562,500 6'x8' RCBC 1577 LF $650 $1,025,050 6'x12' RCBC 1976 LF $850 $1,679,600 5'x12' RCBC 1878 LF $800 $1,502,400 5'x8' RCBC 1798 LF $600 $1,078,800 5'x16' RCBC 936 LF $975 $912,600 Sub‐Total $10,574,325 Detention Detention Volume 17.4 AC‐FT $40,000 $696,000 Sub‐Total $696,000 Utility Relocates Dry Utility Administration (20%) 1 LS $2,253,665 $2,254,065 Sub‐Total $2,254,065 Sub‐Total for Alternative $15,958,780 Contingency (20%) $3,191,756 Total For Alternative $19,200,000 6.5 Water Quality and Erosion Control The provision for permanent water quality BMPs and erosion protection at all outfalls to North Laramie is assumed included in all alternatives. Where possible, combining water quality BMPs with sub‐regional detention is a top priority. Opportunities to incorporate low impact development (LID) BMPs are abundant in the upper undeveloped portions of the watershed. The abundance of Type B soils in this watershed (see Figure 5) is conducive to infiltration BMPs such as porous landscape detention, sand filters, and porous pavements. However, the possibility of high groundwater noted earlier must be considered in the design. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 29 7.0 RECOMMENDED PLAN The following is a discussion of improvements recommended by SEH and explanation of how the recommended plan mitigates and addresses each problem area. The Recommended Plan is shown in Figure 18. 7.1 Plan Description The plan recommended by SEH is a combination of all three alternative improvement plans in addition to optimizing LaBonte Park pond. The alternative analyses concluded that modifying and optimizing existing detention and providing new detention in the upper portions of the basin optimizes the use of the existing storm sewer and street system, providing 100‐year conveyance capacity along Reynolds, upstream of 17th Street. The maturity of the lower portion of the basin remains the most significant constraint to providing upgraded infrastructure that would meet City of Laramie and UDFCD criteria for new development. As discussed in Section 4.7, LaBonte Park pond was added to the selected alternatives to create the Recommended Plan. LaBonte Park pond had the best potential opportunity for regional detention in the lower basin. In order to include LaBonte Park pond modifications in the Recommended Plan, additional subbasins that were not a part of the original North Laramie Drainage Master Plan were added to the study. The recommended plan is presented below on a reach by reach basis, as presented in Figure 18. As a part of the recommended plan, conceptual grading for existing ponds is presented in Figure 19. The costs associated with the components of the recommended plan are summarized in Table 20. As discussed in Section 6.3.1, Subbasins CU01, CM01, CL01, CL02 and RM10 are currently undeveloped basins (existing percent impervious is For these subbasins, detention is required for all future development and release rates for the detention must not exceed existing or “historic” 10‐year peak flow rates. Subbasins RU01, RM08, CM02 and CL03 are partially undeveloped, based on the existing zoning and future land use maps. Local detention is also required for future development in these undeveloped areas, though each will need to be done on an individual basis and not on a regional level due to the existing grade of the basin and the existing development. Also discussed in Section 6.3.1, each of the existing eleven detention ponds was optimized for full spectrum detention. Therefore, each pond was optimized to release at “historic rates” for all four storm events: 10‐ and 100‐year. Subbasins CU01, CM01, CM02 and RM10 currently flow from east to west. At the time of development of future 22nd Street and 30th Street extensions, the hydrology will have to be reviewed. The best option would be to direct flows underneath the street extensions to keep consistent with the flow paths assumed in the hydrologic model for this project. However, if directing flows underneath the road is not an option, additional detention for flows from these subbasins will be necessary to release flows south into the storm sewer system. Reach 1 Reach 1 consists of upstream improvements, as discussed in Section 6.3.1, including requiring detention for future development in undeveloped areas and modifying existing detention ponds. Subbasins CU01 and CM01 are currently undeveloped basins. Approximate detention volumes needed to detain the 100‐year event upon development of these basins are presented in Table 15 in Section 6.3.1. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 30 Currently, subbasin CU01 flows to a sump condition that appears to infiltrate. Infiltration, in addition to localized detention, could be used to in future development to reduce flows to “historic” rates. However, future analysis of infiltration rates would be required. The existing detention pond located in subbasin CM02 is enlarged by approximately 1.7 acre‐feet, the maximum potential volume given land constraints and outlet/spill crest elevation constraints, to help reduce flooding In summary, the recommended plan for Reach 1 will mitigate the flooding problems that would occur upon future development of these subbasins by detaining flows and significantly reducing peak flows. Water quality is also enhanced through extended detention. Reach 2 Reach 2 consists of upstream improvements as well as upsizing existing pipe and adding additional pipe. Subbasins CL01 and CL02 are currently undeveloped subbasins. Approximate detention volumes needed to detain the 100‐year event upon development of these basins are presented in Table 15 in Section 6.3.1. Subbasins CL03, CL04, CL05, CL06 and CL 07 are fully developed subbasins based on existing zoning and future land use maps (existing percent impervious is equal to future percent impervious). Improvements for these subbasins include upsizing the existing 18” reinforced concrete pipe (RCP) along Beaufort Street between 8th Street and 9th Street and 30” RCP storm sewer 9th Street between Beaufort Street and Downey Street to 54” RCP and installing a new 6’x8’ RCBC trunkline storm sewer that intercepts flows at the intersection of 9th Street and Downey Street and carries them to the outfall channel via Downey Street to 7th Street south to Mitchell Street and west toward the existing outfall channel. The recommended plan for Reach 2 will mitigate the flooding problems that would occur upon future development of these subbasins by detaining flows and significantly reducing peak flows. Water quality is also enhanced through extended detention. In addition, upsizing the pipe along 9th and Beaufort Streets and adding an additional trunkline system to the outfall removes flows and reduces flooding along Curtis Street. Reach 3 Reach 3 consists only of upstream improvements, as discussed in Section 6.3.1, including requiring detention for future development and modifying/ optimizing existing detention ponds. Improvements consist of upsizing the existing pond at the northeast corner of 30th and Reynolds Streets approximately 1.7 acre‐feet, as well as optimizing the outlet of this pond and the outlet of the existing pond at the southeast corner of 30th and Reynolds to accommodate full spectrum detention. Subbasin RU06 currently flows west along Grays Gable to 30th Street and contributes to flooding along 30th Street. It is assumed that the flows from subbasin RU05, approximately 300 cfs during the 100‐year event, will be intercepted and redirected to Jacoby Golf Course irrigation ditch located just south of Grays Gable. However, if these flows are not intercepted from the Golf Course, it is recommended to upsize the existing 24” RCP storm sewer in 30th Street, from Grays Gable to ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 31 Reynolds, to 60” RCP. The 10 acre‐foot pond at the southeast corner of 30th Street and Reynolds Street is sized to handle the 300 cfs discussed above. If the Jocoby Golf Course does intercept the flow from subbasin RU05, the size of this pond may be reduced. The recommended improvements for Reach 3 will eliminate the flooding which occurs along 30th and Reynolds Street and reduce flooding Reach 4 Reach 4 consists of upstream improvements, as discussed in Section 6.3.1, including requiring detention for future development and optimizing existing detention ponds. Subbasin RM10 is currently an undeveloped subbasin. The approximate detention volume needed to detain the 100‐year event upon development of these basins are presented in Table 15 in Section 6.3.1. Subasins RM07 and RM08 are partially developed. Improvements for these subbasins include optimizing the outlets of the existing ponds at the northwest corner of Nighthawk and 22nd Streets and at the northwest corner of 22nd and Reynolds Streets to accommodate for full‐spectrum detention. In summary, the improvements for Reach 4 will reduce flooding along Reynolds Street upon future development of these subbasins. Reach 5 Reach 5 consists of upstream improvements, as discussed in Section 6.3.1, including requiring detention for future development and optimizing existing detention ponds. Subbasins RM02 and RM05 are fully developed subbasins. Improvements for these subbasins include optimizing the pond outlet structure in the existing pond at the southeast corner of 22nd and Binford Streets to accommodate full spectrum detention. The addition of a 10 acre‐feet pond at the southwest corner of 30th and Reynolds, which would work in series with the pond at the southeast corner of this intersection, would alleviate flooding issues at the corner of 30th and Reynolds Streets and along Reynolds. Reach 6 Reach 6 consists of upstream improvements, as discussed in Section 6.3.1, including modifying and optimizing an existing detention pond as well as upsizing existing storm sewer pipe. All subbasins within this reach are fully developed subbasins. Improvements in subbasin RM06 consists of increasing the size of the existing detention at on the south side of Reynolds Street between 17th and 19th Streets approximately 1.6 acre‐feet and modifying the outlet structure to accommodate full spectrum detention. Additional improvements in this reach include upsizing the existing 42” and 48” RCP storm sewer in Reynolds Street to 60” RCP from about Coughlin St. west to 9th Street and continuing south down 9th Street to Hancock Street. A flow split will be installed at the intersection of 9th Street and Hancock Street allowing some flow to utilize the existing 48” RCP along Hancock Street in Reach 8. An additional 5’x8’ RCBC storm sewer is installed from the intersection of 9th Street and Hancock Street south to Shields Street to direct the remaining flows to LaBonte Park pond. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 32 Improvements in Reach 6 will remove flooding from Reynolds street and direct more flows to LaBonte Park Pond, reducing flooding within Reach 8. Reach 7 Reach 7 consists of upstream improvements, as discussed in Section 6.3.1, including modifying and optimizing an existing detention pond as well as upsizing existing storm sewer pipe. All subbasins within this reach are fully developed subbasins. Improvements in subbasin LM01 consist of increasing the size of the existing detention at on the northeast corner of 15th Street and Harney Street approximately 1.1 acre‐feet and modifying the outlet structure to accommodate full spectrum detention. Improvements in subbasin LM02 consists of optimizing the outlet structure to the existing pond at the southeast corner of 15th Street and Harney Street to accommodate full spectrum detention. Improvements within subbasins LL01, LL02, LL03, LL04 and LL05 consist of upsizing the existing 24”, 30” and 36” RCP storm sewer pipe to 60” RCP from 11th Street and Gibbon Street north to 11th Street and Canby Street and west along Canby Street to 9th Street as well as from 9th Street and Gibbon Street north along 9th Street to Canby Street. Continuing west along Canby Street from 9th Street to 8th Street, new 5’x8’ RCBC pipe is installed. At 8th Street and Canby Street, the 5’x8’ RCBC will join 42” RCP, upsized from 18” RCP, from 8th Street and Harney Street and continues to LaBonte Park pond as a 5’x10’ RCBC. Improvements in Reach 7 also consist of regrading LaBonte Park pond and 9th Street to increase the volume of the pond approximately 36.4 acre‐feet and more directly convey flows from 9th Street into the pond. This would include inverting the crown of 9th Street to slope the street towards LaBonte Park pond and possibly removing the curb and gutter on the west side of the street to allow flows into the pond. Improvements to LaBonte Park pond also include upsizing the existing 36”x60” elliptical RCP storm sewer outfall into LaBonte Park pond at 9th and Shields to 5’x10’ RCBC and installing a new 36” RCP outfall from LaBonte Park pond to 7th and Shields Street. During the initial discussion of LaBonte Park as a potential location for detention, it was noted by the City of Laramie Parks and Recreation Department that the existing trees would not survive any grading. It was concluded that the City would not want to grade LaBonte Park to create additional storage. However, the current sump condition of the park will still allow for the 10‐ and 100‐year event to be detained as long as the following items are allowed:  A berm on the west side of LaBonte Park pond at a minimum elevation of 7146.0 is needed to contain the 100‐year water surface elevation of 7145.9.  The 100‐year event will cause water to discharge to the south into Canby Street and pond, with minimal depth of water in the street but no apparent inundation of structures. This area within Canby Street will be part of the detention pond volume and will eventually discharge back through the LaBonte Park pond during the draining portion of the event. (Note that during design of the west side berm and upstream improvements into LaBonte Park, the exact elevation of the berm will need to be compared to the elevations of the structures on Canby Street, so as to prevent any impact to any dwellings. It is possible that an additional berm along the south side of LaBonte Park pond could contain the 100‐year event.)  The detention pond will have minimal to no freeboard during the 100‐year event and will have no defined spillway. Any additional stormwater above the 100‐year event will overtop the proposed west side berm and other locations and will spill most‐likely to the northwest. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 33 Although LaBonte Park pond does not have the typical freeboard required for the 100‐year event, it should be noted that the proposed Reach 8 will be sized for the 10‐ year storm event and LaBonte Park pond has the required freeboard for the 10‐year event. Reach 7 improvements will mitigate flooding during the 100‐year event within the reach specifically along 9th Street. Improvements to LaBonte Park pond also reduce flooding in Reach 8 by intercepting and detaining all flows from Reach 7 and a portion of flow from Reaches upstream along Reynolds Street. Reach 7 may be subject to minor localized flooding within the Reach near the intersection of 14th and Harney Streets. Reach 8 Improvements within Reach 8 consist of upsizing existing storm sewer pipe. Due to physical constraints, this Reach is sized to convey the 10‐year storm event. Storm sewer is upsized beginning at 7th Street and Shields Street with 36” RCP, replacing 24” RCP, and continues west to 4th Street, north along 4th Street to Hancock Street at which it increases to a 4’x8’ RCBC. At this point, the existing 48” RCP, carrying the flows split west from 9th Street and Hancock Street, join the system. The 4’x8’ RCBC, replacing existing 48” RCP, continues west along Hancock Street to 2nd Street where it turns north towards McConnnell Street and then turns west toward the railroad track. The pipe is then increased to a 4’x10’ RCBC, replacing the existing 48” RCP outfall, which parallels the railroad tracks to the existing Reynolds Street outfall. It is recommended, if possible, that the existing outfall channel which runs parallel to the railroad tracks and begins perpendicular to Beaufort Street be extended upstream to McConnell Street in lieu of the proposed 4’x10’ RCBC, reducing backwater effects and allowing for more conveyance to the Laramie River. In summary, improvements within Reach 8 help mitigate flooding within the Reach however, flooding will still occur in the Reach along Hancock Street, 2nd Street and McConnell Street during any event larger than a 10‐year event. Reach 9 Improvements within Reach 9 consist of upsizing existing storm sewer pipe. These improvements are independent of all other reaches. Storm sewer is upsized from existing 24” RCP to 60” RCP beginning in 6th Street from Lewis Street north to Canby. At 6th and Canby Street the 60” RCP meets a 4’x10’ RCBC, upsized from 24” RCP, which runs along Canby Street from 6th Street to 3rd Street and continues south along 3rd Street to Harney Street where it joins a 42” RCP, upsized from 24” RCP, that runs along 3rd Street from Lewis to Harney. At 3rd and Harney Street the existing 42” RCP storm sewer is upsized to a 4’x10” RCBC that continues west along Harney clearing beneath the railroad tracks and above the existing sanitary sewer line and eventually outfalls into the Laramie River. Local improvements due localized flooding will also be needed on Canby between 3rd and 6th Street. The outfall to the Laramie River is limited due to the railroad tracks and existing sanitary sewer. See Appendix K for a preliminary plan and profile of the outfall. Improvements in Reach 9 mitigate flooding in the reach during the 100‐year event with exception to minor localized flooding along Canby Street near 3rd Street. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 34 7.2 Floodproofing Improvements as recommended above provide protection against the 100‐year event in all Reaches except Reach 8, with exception to minor localized flooding areas mentioned above. Improvements within Reach 8 will protect against the 10‐year event but the reach will experience flooding during any event larger than a 10‐year event. Floodproofing of existing buildings and structures within Reach 8 may be cost effective if they flood regularly. Floodproofing may include installing berms/ levees around the structure or physically making structural improvements, which range from installing watertight doors and windows to physically raising the structures elevation, using fill or piles. The purpose of floodproofing is to minimize damages by redirecting flows around a structure or making the property less vulnerable to damages if the flood waters reach the structure. Floodproofing does not eliminate all flood damages but, if installed correctly, may significantly reduce the severity of damages. 7.3 Cost Analysis of Recommended Plan A cost estimate for the recommended plan is presented in Tables 20. The construction cost estimate presented is based on construction unit costs for recently completed drainage projects in the Denver metro area, a bid tabulation database maintained by the UDFCD, and engineering judgment. Because of the unique sizes of the proposed reinforced box culverts, a one‐foot wall, floor, and ceiling thickness and a $625 per cubic yard price for concrete was assumed. The construction cost estimate is increased by 20 percent to account for contingencies, engineering, administration, and legal fees. Costs were also increased by assuming a 5 percent traffic control component, 8 percent for mobilization/demolition, 5 percent for material remediation and disposal, and 20 percent for utility relocation. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 35 Table 20: Conceptual Cost Estimate Recommended Plan Item No. Description Quantity Unit Unit Price Total Cost Traffic Control 1 LS $814,158 $814,158 Mobilization/Demolition 1 LS $1,302,653 $1,302,653 Material Management (environmental remediation and disposal) 1 LS $814,158 $814,158 Storm Sewer 36" RCP 1900 LF $150 $285,000 42" RCP 1710 LF $190 $324,900 54" RCP 1440 LF $210 $302,400 60" RCP 7950 LF $230 $1,828,500 4'x8' RCBC 1880 LF $550 $1,034,000 5'x8' RCBC 650 LF $600 $390,000 6'x8' RCBC 5070 LF $650 $3,295,500 4'x10' RCBC 5630 LF $650 $3,659,500 5'x10' RCBC 425 LF $700 $297,500 Sub‐Total $11,417,300 Detention Detention Volume 53.8 AC‐FT $40,000 $2,152,000 Sub‐Total $2,152,000 Utility Relocates Dry Utility Administration (20%) 1 LS $2,735,460 $2,713,860 Sub‐Total $2,713,860 Sub‐Total for Recommended Plan $19,214,129 Contingency (20%) $3,842,826 Total For Recommended Plan $23,100,000 7.4 Recommendation of Construction Phasing Given the complexity and expense of the recommended plan, a recommended construction phasing plan has been prepared to prioritize the construction of the improvements while maximizing the potential benefits of the individual improvements. The recommended plan has been divided up into nine construction phases as discussed below. Figure 20 depicts these phases. Benefits, predecessors and protection provided by construction of each of the phases is listed in Table 21 ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 36 Table 21: Benefits‐Predecessor‐Protection by Phase Phase Description Benefits Predecessors Protection As‐ needed Regional Detention (based on development)  Reduces post development 100‐year flows to 10‐year “historic” rates.  Ultimately reduces flooding in Reach 8  As‐needed based on development in the basin 100‐year in Reach 1 (Note: The 10 acre‐foot pond at 30th Street and Reynolds Street depends on availability of the land, the potential for removing flow at Gray’s Gable and other phased improvements. At a minimal, the pond should be considered part of Phase 1 Optimize existing ponds at 15th Street and Harney Street  Inexpensive improvements  Reduces flooding immediately  None 2 Optimize existing ponds at 30th Street and Reynolds Street  Inexpensive improvements  Reduces flooding in lower portions of the basin  None 100‐year in Reach 3 3 Optimize existing ponds along Reynolds Street (Note: See above note about new 10 acre‐foot pond)  Inexpensive improvements  Reduces flooding in the lower portions of the basin  None 100‐year in Reaches 4 and 5 4 Optimize existing pond at 10th Street and Beaufort Street  Inexpensive improvements  Reduces flooding in lower portions of the basin  None 5 Reach 8 improvements from LaBonte Park pond outfall to the outfall channel  Reduces local flooding in Reach 8  Allows flows to be released from LaBonte Park pond  Phases 2 and 3 6 LaBonte Park pond improvements and upstream connection  Optimizes flow into LaBonte Park pond from Reach 7  Conveys more flows from Reynolds Street into LaBonte Park pond  Phase 5 100‐year in Reach 7 7 Harney Street outfall  Increases conveyance in Reach 7  Removes flows from LaBonte Park pond to allow for more capacity from Reynolds Street  None (If done before Phase 6, the current connection between LaBonte Park pond will need to be examined.) 100‐year in Reach 9 8 Additional Curtis Street outfall  Provides an additional outfall for flows from Reach 2  Removes flows from entering Reach 8  Phase 4 100‐year in Reach 2 9 Reynolds Street and 9th Street improvements  Provides local capacity in Reach 6  Optimizes flows from Reynolds Street into LaBonte Park pond  Phase 6 100‐year in Reach 6, 10‐ year in Reach 8 ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 37 Phase 1 begins with improvements to the detention ponds located at the northeast and southeast corners of the intersection of 15th and Harney Streets. Phase 2 includes improvements the two detention ponds located at the northeast and southeast corners of the intersection of 30th and Reynolds Streets. Phase 2 is followed by improvements to five detention ponds located at the intersection of 22nd and Nighthawk Streets, 22nd and Hancock Streets and 22nd and Reynolds Streets and along Reynolds Street between Bath and Dillon Streets, and between 17th and 18th Streets in Phase 3. Phase 4 includes includes improvements to the detention pond at the intersection of 10th and Beaufort Streets. Improvements to the trunkline system of LaBonte Park pond are a part of Phase 5, followed by improvements to LaBonte Park pond and storm sewer improvements upstream along Canby and 11th Streets in Phase 6. Phase 7 includes improvements to the trunkline sewer system south of, and independent of, LaBonte Park pond including the outfall along Harney Street. Installing improvements along 9th Street north of Downey as well as the construction of the new outfall along Mitchell Street are a part of Phase 8. Lastly, Phase 9 improvements involve replacement of the storm sewer system along 9th Street north of Hancock Street and along Reynolds Street west of 9th Street. Construction of additional detention ponds within the undeveloped upstream basins are to be constructed as‐needed upon development of these basins. 7.5 Water Quality Impacts Although portions of the basin are considered fully developed, and sediment‐laden runoff is not a primary concern, the Laramie River receiving waters will benefit from the water quality improvements in the recommended plan. The outfall protection that is recommended for the outfalls will reduce stream and bank erosion in the outfall channels. A majority of the water quality improvements will be from extended detention, which occurs in the upper portions of the basin. A focus on Low Impact Development in local drainage projects in the lower portion of the basin will also increase water quality, especially in areas of B soils. 7.6 Operations and Maintenance The replacement of the storm sewers and inlets required for the full implementation of the recommended plan will result in the same or less maintenance, as new inlets are less likely to clog. Also, an appropriate number of inlets will be provided in key locations to ensure that storm sewers receive the expected flowrates, ensuring that debris and minor sediment that enters the system is properly flushed out. The addition of water quality components will also have a positive impact on lessening the frequency and scope of inlet and storm sewer maintenance required. The implementation of the recommended sub‐regional detention and water quality ponds, however, will require additional maintenance to ensure proper operation of these facilities. The new regional detention/water quality ponds will require additional time, materials, and equipment to maintain in perpetuity. Inspections, debris and litter removal, routine mowing, and mosquito control will all become potential routine maintenance activities. Based on the fully developed nature of the basin, routine sediment removal should not be expected, but is anticipated to be required every 5‐15 years. The upgrades to the LaBonte Park detention pond will increase the frequency of required inspection and maintenance, as litter and debris removal, maintenance path repairs, and retaining walls/benched areas may require more attention. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 38 8.0 DEVELOPING A STORMWATER UTILITY SEH recommends developing a stormwater utility in the City of Laramie for means of funding stormwater improvements within the City. The following is a recommended two‐phase approach toward establishing a stormwater utility or other means of funding for the stormwater program. The first phase, which will culminate in a Technical Feasibility Study, is essentially an action plan that incorporates reconnaissance level investigations focused on the feasibility and applicability of a stormwater utility. The purpose of the Technical Feasibility Study is to determine preliminary direction and answers to key questions, all of which will likely have cost and schedule implications. Through this technical feasibility investigation, the approach taken and the associated costs with respect to the second phase can be refined and used to provide the City of Laramie with a roadmap for implementation of the ultimate funding mechanism selected. Figure 4 below depicts the progression of the stages recommended by SEH for the first phase of developing a stormwater utility. Figure 4: Flowchart for Phase One of Developing a Stormwater Utility The City will need to assess the current stormwater management program, refine the problems and needs, establish proposed program priorities, develop an improved stormwater management program, and explore the advantages and disadvantages of the possible funding options. Potential funding options may include: Program Description •Define current level of service •Review and summarize existing City of Laramie Stormwater Management program and budget Problems and Needs •Refine problems and needs •Identify flooding issues •Perform a risk assessment Program Priorities •Develop preliminary program priorities and implementation goals •Evaluate risks and identitfy acceptable levels of risk and mitigation strategies Planned Program •Define proposed level of service •Develop initial cost of service estimates Funding Options •Examine available funding options based on statutory and pre‐ existing limitations •Compare stormwater service fees and programs for similar cities and towns •Explore database and billing options Financial Plan Technical Memo •Develop an Action Plan for the second phase •Highlight existing and proposed 10‐year revenue and expenditure projections ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 39 • General fund appropriations (sales and/or property taxes), • Stormwater utility service fees, • Public improvement districts, • Bonding for capital improvements, • System development fees, • Plan review, development inspection, and special inspection fees, • Impact fees, • Federal and state grants and funding opportunities, or • Formation of a regional drainage and flood control district. Based on this effort, a 10‐year financial plan will need to be evaluated and developed as the capstone to the Technical Feasibility Study. The existing and proposed stormwater program categories evaluated will include: • Operation and maintenance, • Capital needs, • Water quality and NPDES MS4 programs, • Floodplain management and master planning, • Land development, • Billing and finance, and • Engineering support. The results of the financial plan will be used to develop an action plan for the second phase of the work. The action plan for the second phase of work will: • Test the political feasibility/acceptability of the proposed program and fee structure, • Refine the program strategy and preliminary cost of service estimates, • Identify the preferred service fee rate methodology, • Investigate appropriate governance mechanisms, and • Determine the best master account file, billing, collection, and accounting methods. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Page 40 9.0 REFERENCES Nolte Associates, Inc., 2009. West Campus Drainage Study and Recommended Improvements Report. Urban Drainage and Flood Control District, 2005. Colorado Urban Hydrograph Procedure, Version 1.3.3. Urban Drainage and Flood Control District, 2001. Urban Storm Drainage Criteria Manual. ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Figures Figure 1: Location Map (within the report) Figure 2: Typical Urban Street Section (within the report) Figure 3: Typical Urban Street Section Capacity Rating Curve (within the report) Figure 4: Flowchart for Phase One of Developing a Stormwater Facility (within the report) Figure 5: Hydrologic Soil Group Figure 6: Existing Land Use Figure 7: Future Land Use Figure 8: Rain Gage Locations Figure 9a: Subbasin Delineation Map Figure 9b: Subbasin Contour Map (24” x 36” Fold Out Map) Figure 10a‐10d: Routing Schematic Figure 11: Reach Designations Figure 12: Areas of Flooding: 2‐ and 100‐year Events – Existing Percent Impervious Figure 13: Areas of Flooding: 2‐ and 100‐year Events – Future Percent Impervious Figure 14: Upstream Alternative: Pond Modifications Figure 15: Alternative 1: Upsize Existing Trunk Line Sewers Figure 16: Alternative 2: Additional Trunk Line Sewers Figure 17: Alternative 3: LaBonte Discharge and Upsize Existing Trunk Line Sewers Figure 18: Recommended Plan Figure 19: Recommended Plan – Proposed Pond Contours Figure 20: Recommended Phasing Plan ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- CU01 CM02 RU06 CM01 CL05 LL01 RL02 RU01 CL06 LL07 LL09 CL02 CL03 RM02 LL04 RM06 LL08 RM11 RU04 RM08 RM10 RL03 CL07 RU02 LM02 CL08 RM03 RM07 CL04 RM09 RL01 RM05 LL02 RU03 RM04 LL06 LL03 CL01 LL10 CL09 RU05 LM01 LL05 RM01 15TH 3RD 9TH 287 HARNEY WILLETT 5TH 22ND REYNOLDS 4TH 6TH 7TH 8TH SHIELD LEWIS FLINT PINE 30TH IVINSON 11TH 10TH CLARK CANBY HILL 13TH GIBBON CEDAR CURTIS LYON BRADLEY 2ND 12TH 14TH 19TH HANCOCK GRAND BAKER SULLY RAILROAD FREMONT MILL HODGEMAN 45TH MITCHELL INCA DOWNEY UNIVERSITY 17TH BEAUFORT 23RD 1ST CROW NIGHTHAWK 18TH KING ARMORY DOVER APACHE FRONTERA BATH COE RENSHAW HAYFORD GRAYS GABLE 16TH CRANE HIDALGO GRANITO BINFORD 28TH 21ST ALTA VISTA EDWARDS CHEYENNE SORORITY JOANNA BRUNER COMANCHE TELEVISION DUNA ALSOP MCCONNELL LAND GRAFTON FRATERNITY INDIAN HILLS KNADLER HENRY SOULE KIOWA NELSON COUGHLIN TOLTEC ALBIN THAXTON BONITA TRABING LESLIE DALE NORTHVIEW AMES ARAPHAHO CARRINGTON TULLIS RIDGEVIEW SIOUX HANCOCK HILL KNADLER O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 5 Hydrologic Soil Groups Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 02/2012 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend Street Subbasin Boundary Hydrologic Soil Group B C D 0 1,200 2,400 600 Feet ---PAGE BREAK--- 15TH 3RD 9TH 287 WILLETT HARNEY 5TH 22ND REYNOLDS 4TH 6TH 7TH 8TH SHIELD LEWIS FLINT 30TH IVINSON 11TH 10TH CANBY HILL 13TH GIBBON LYON CLARK CURTIS BRADLEY 2ND 14TH 12TH 19TH HANCOCK SULLY BAKER RAILROAD MITCHELL FREMONT MILL 45TH INCA DOWNEY UNIVERSITY 17TH BEAUFORT 23RD CROW 1ST GRAND DOVER ARMORY 18TH APACHE FRONTERA BATH COE LAND NIGHTHAWK RENSHAW HAYFORD 16TH HIDALGO ALTA VISTA GRANITO BINFORD GRAYS GABLE NAVAJO 27TH 28TH 21ST INDIAN HILLS EDWARDS CHEYENNE SORORITY COMANCHE TELEVISION DUNA ALSOP DILLON MCCONNELL SEETON GRAFTON FRATERNITY THOMES KNADLER SOULE NELSON BONITA COUGHLIN HENRY TOLTEC ALBIN THAXTON EMPINADO TRABING SUPERIOR CT BANOCK LESLIE NORTHVIEW NOTTAGE AMES DIAMOND HEAD ARAPHAHO CARRINGTON SIOUX FOX FOX RIDGE HILLTOP HANCOCK HAYFORD HILL KNADLER CU01 CM02 RU06 CM01 CL05 LL01 RL02 RU01 CL06 LL07 LL09 CL02 CL03 RM02 LL04 RM06 LL08 RM11 RU04 RM08 RM10 RL03 CL07 RU02 LM02 CL08 RM03 RM07 CL04 RM09 RL01 RM05 LL02 RU03 RM04 LL06 LL03 CL01 LL10 CL09 RU05 LM01 LL05 RM01 O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 6 Existing Land Use Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 02/2012 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Text Legend Street Subbasin Boundary Land Use Type Undeveloped Low Density Residential (40%) Mediuim Density Residential (60%) Mediuim Density Residential w/ Indep. Mobile Homes (60%) Multifamily (75%) Neighborhood Business (80%) General Business (85%) Limited Business (85%) Industrial (90%) Commercial Wholesale (95%) 0 1,200 2,400 600 Feet Note: Existing Land Use layers were created from existing zoning GIS data received from the City of Laramie. ---PAGE BREAK--- CU01 CM02 RU06 CM01 CL05 LL01 RL02 RU01 CL06 LL07 LL09 CL02 CL03 RM02 LL04 RM06 LL08 RM11 RU04 RM08 RM10 RL03 CL07 RU02 LM02 CL08 RM03 RM07 CL04 RM09 RL01 RM05 LL02 RU03 RM04 LL06 LL03 CL01 LL10 CL09 RU05 LM01 LL05 RM01 15TH 3RD 9TH 287 WILLETT HARNEY 5TH 22ND REYNOLDS 4TH 6TH 7TH 8TH LEWIS FLINT SHIELD 30TH 11TH 10TH CANBY HILL 13TH IVINSON GIBBON LYON CLARK CURTIS BRADLEY 2ND 12TH 14TH 19TH HANCOCK SULLY BAKER RAILROAD MITCHELL FREMONT MILL 45TH INCA DOWNEY UNIVERSITY 17TH BEAUFORT 23RD CROW 18TH 1ST ARMORY DOVER APACHE FRONTERA BATH COE NIGHTHAWK RENSHAW HAYFORD GRAYS GABLE 16TH HIDALGO ALTA VISTA GRANITO BINFORD 28TH 21ST INDIAN HILLS EDWARDS CHEYENNE SORORITY COMANCHE TELEVISION DUNA ALSOP MCCONNELL LAND GRAFTON FRATERNITY KNADLER SOULE NELSON COUGHLIN HENRY TOLTEC ALBIN THAXTON BONITA TRABING BANOCK LESLIE DALE NORTHVIEW AMES ARAPHAHO CARRINGTON TULLIS RIDGEVIEW SIOUX HANCOCK HILL KNADLER O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 7 Future Land Use Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 02/2012 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Text Legend Street Subbasin Boundary Land Use Type Agriculture Park / Open Space Auto-Urban Residential (40%) Suburban Residential (40%) Urban Residential (40%) Public / Institutional (50%) Urban University (50%) Auto-Urban Multifamily (75%) Industrial (90%) Auto-Urban Commercial (95%) Suburban Commercial (95%) Urban Commercial (95%) 0 1,200 2,400 600 Feet Note: Future Land Use layers were created from future land use GIS data received from the City of Laramie. ---PAGE BREAK--- #0 #0 #0 North Laramie 80 130 230 9TH 15TH 3RD 287 5TH 4TH 7TH 8TH 22ND 2ND 6TH WILLETT PINE HARNEY PARK 30TH ADAMS 13TH GRAND VISTA REYNOLDS CURTIS SHIELD LEWIS 17TH ORD FLINT SHERIDAN CEDAR GRANT COLORADO PIERCE TAYLOR LYON IVINSON STOCKYARDS 11TH 10TH CLARK CANBY CUSTER HILL POLK MCCUE RIVERSIDE GIBBON JOHNSON MONROE WYOMING FILLMORE KEARNEY GARFIELD SYMONS 12TH BRADLEY HARRISON RUSSELL SNOWY RANGE MADISON 1ST 14TH JACKSON CORTHELL 21ST 19TH STEELE VAN BUREN 23RD SKYLINE WASHINGTON BILL NYE BOULDER BAKER FORT SANDERS 18TH ARNOLD SULLY 26TH HAYES RAILROAD HURON MITCHELL VENTURE FREMONT E 16TH PILOT PEAK MILL BOBOLINK 45TH HILLSIDE INCA DOWNEY C JEFFERSON RAINBOW FAIRVIEW BEAUFORT BEECH SANDERS SYBILLE CROW SWEETWATER FRANKLIN HAYFORD PERSON KING SPRING CREEK OVERLAND BARRATT PLAZA FORT BUFORD ARMORY APACHE FRONTERA OLD 130 20TH COE EASTERLING AEROSPACE CHIMNEY LAMP BINFORD ARTHUR YUCCA 24TH RENSHAW BOSWELL CLEVELAND ALTA VISTA EVANS 27TH LUPINE HOLIDAY DOVER INDIAN HILLS DOUGLAS CARROLL MOUNTAIN SHADOW HACKNEY ASHLEY ORIOLE DUNA GLACIER SEETON REGENCY FRATERNITY COUNTY SHOP PLATEAU CONNERS WISTER ARABIAN ROBERTS COMMERCE WARREN THAXTON DADISMAN PEARL SUPERIOR CT 287 18TH SANDERS BOSWELL 29226 ft 18337 ft 11536 ft Sta. No. 485417 Sta. No. 485415 Sta. No. 485435 O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 8 Rain Gage Locations Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 02/2012 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend Street Study Area 0 3,000 6,000 1,500 Feet ---PAGE BREAK--- CU01 267 ac. 43% CM01 117 ac. 45% CM02 120 ac. 19%/ 40% RU06 109 ac. 45%/ 45% CL02 70 ac. 52% RU01 87 ac. 31%/ 40% CL05 84 ac. 52%/ 52% RL02 81 ac. 71%/ 71% CL06 80 ac. 67%/ 67% LL01 75 ac. 73%/ 73% RM02 71 ac. 40%/ 40% RM10 55 ac. 40% LL07 70 ac. 75%/ 75% RM06 68 ac. 74%/ 74% CL03 65 ac. 23%/ 47% LL09 64 ac. 86%/ 91% RM11 60 ac. 56%/ 56% RM08 58 ac. 27%/ 40% RU04 56 ac. 40%/ 40% LL04 52 ac. 64%/ 64% LL08 50 ac. 87%/ 87% RM03 49 ac. 40%/ 42% LM02 46 ac. 75%/ 75% RL03 46 ac. 93%/ 93% RM07 45 ac. 34%/ 38% CL07 45 ac. 62%/ 62% CL08 41 ac. 53%/ 70% RM09 40 ac. 45%/ 45% CL09 26 ac. 92% LL02 30 ac. 73%/ 73% LL10 25 ac. 61%/ 61% RU02 46 ac. 40%/ 40% RM05 39 ac. 63%/ 63% CL01 28 ac. 40% CL04 36 ac. 58%/ 58% RM04 36 ac. 35%/ 37% RU03 34 ac. 41%/ 41% RL01 33 ac. 66%/ 66% RU05 28 ac. 35%/ 39% LL06 27 ac. 75%/ 75% LL03 27 ac. 61%/ 61% LM01 22 ac. 75%/ 75% RM01 20 ac. 47%/ 47% LL05 17 ac. 71%/ 71% 15TH 3RD 9TH 287 HARNEY WILLETT 5TH 22ND 4TH 6TH 7TH 8TH REYNOLDS LEWIS 30TH FLINT GRAND SHIELD IVINSON 11TH 10TH CANBY HILL 13TH CLARK GIBBON PINE 2ND LYON CURTIS BRADLEY 12TH 14TH 19TH HANCOCK BAKER SULLY RAILROAD MITCHELL FREMONT MILL HODGEMAN 45TH 1ST INCA DOWNEY UNIVERSITY 17TH BEAUFORT 23RD CROW 18TH DOVER KING ARMORY APACHE FRONTERA BATH COE NIGHTHAWK RENSHAW HAYFORD 16TH CRANE ALTA VISTA HIDALGO GRANITO BINFORD GRAYS GABLE 27TH INDIAN HILLS SORORITY JOANNA BRUNER COMANCHE TELEVISION 21ST MCCONNELL LAND GRAFTON FRATERNITY KNADLER SOULE NELSON ALBIN WARREN ARROWHEAD 20TH TRABING BANOCK LESLIE NORTHVIEW AMES ARAPHAHO RIDGEVIEW HANCOCK HILL O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 9a Subbasin Delineation Map Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 02/2012 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend Street Subbasin Boundary Basin ID Area (acres) Existing/ Future % Impervious RU03 34.1 ac. 41%/41% 0 1,200 2,400 600 Feet ---PAGE BREAK--- # #
CL05 L1300 L1306 L1310 L2110 L1005 L1200 L2022 L1031 L1036 L1911 L1000 L1001 L1035 L2001 L2122 L1101 L1010 L1015 L2010 L1110 L2120 L1020 L1311 L2005 L1105 L1912 L1115 21 L1300 L2115 L1030 L21 L1000
CL01
CL02
CL04
CL03
CM02
CM01
CL07
CL08
CL05
CL06
CL09
RM11
RL02 2319 2178 2166 2121 2116 2115 2105 2093 2059 2054 2022 2021 2009 2007 0010 0007 O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 10a Routing Schematic Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 09/2010 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend # Storage Node Subbasin Boundary 0 500 1,000 250 Feet 4,000 0 2,000 Feet O XP SWMM Link ID Subbasin ID ---PAGE BREAK--- # # # #
CL05 L1300
LL07
LL05
LL06
LL09
LL08 L2206 L2201 L2203 L2806 L2801 L2805 L2800 L2802 L2807 L2110 L2200 L2100 L1005 L2022 L2125 L2215 L2230 L2101 L2226 L2001 L2202 L2122 L1010 L2220 L1015 L2225 L2210 L2020 L2010 L2120 L1020 L2105 L2005 L1912 L2021 L2240 L2211 L2115 L2235 L2201 L2205 L2245 L2121
LL02
RM11
RM09
RL03
RL02
RL01
LL04
LL01
LM01
LL03 2705 2700 2335 2334 2327 2319 2297 2282 2279 2235 2229 2226 2211 2206 2199 2186 2178 2059 2054 2030 2022 2021 2019 2009 0006 O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 10b Routing Schematic Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 09/2010 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend # Storage Node Subbasin Boundary 0 500 1,000 250 Feet 4,000 0 2,000 Feet O XP SWMM Link ID Subbasin ID ---PAGE BREAK--- # #
CL05 L1300
RM08 L1315 L1306 L1310 L2110 L1200 L1031 L2310 L2305 L2122 L1311 L2506 L1300 L2510 L2306
CL01
CL02
CM02
CM01
CU01
CL05
RM10
RM07
RM04
RM03

RM11
RM09 0016 2435 2121 0007 O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 10c Routing Schematic Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 09/2010 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend # Storage Node Link Subbasin Boundary 0 500 1,000 250 Feet 4,000 0 2,000 Feet O XP SWMM Link ID Subbasin ID ---PAGE BREAK--- # # # # #
CL05 L1300 L2640 L2605 L2706 L2305 L2630 L2636 L2405 L2700 L2710 L2506 L2616 L2130 L2620 L2600 L2510 L2617 L2126 L2705
RM07
RM04
RM03
RU01
RU05
RM01
RM02
RU02
RU03
RM05
RU04 L2650 L2631
RU06 801 0016 0015 2650 2643 2639 2412 2365 2364 2363 2359 0017 0005 0004 O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 10d Routing Schematic Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 09/2010 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend # Storage Node Subbasin Boundary 0 500 1,000 250 Feet 4,000 0 2,000 Feet O XP SWMM Link ID Subbasin ID ---PAGE BREAK--- # # # # # # # CU01 RU06 CM02 CM01 LL01 CL05 RL02 CL06 RU01 LL07 LL09 CL02 CL03 LL04 RM02 LL08 RM06 RM11 RU04 RM08 RL03 CL07 RM10 RU02 LM02 CL08 RM03 RM07 CL04 RL01 LL02 RM09 RM05 RU03 LL06 LL03 RM04 CL01 LL10 CL09 RU05 LM01 LL05 RM01 15TH 3RD 9TH 287 WILLETT HARNEY 5TH 22ND REYNOLDS 4TH 6TH 7TH 8TH LEWIS FLINT SHIELD 30TH 11TH HILL CANBY 10TH 13TH GIBBON CLARK IVINSON LYON BRADLEY 14TH 12TH 2ND 19TH HANCOCK BAKER SULLY CURTIS RAILROAD MITCHELL MILL FREMONT INCA 45TH DOWNEY 17TH BEAUFORT UNIVERSITY 23RD HODGEMAN CROW NIGHTHAWK 18TH ARMORY 1ST BATH APACHE FRONTERA COE BINFORD RENSHAW GRAYS GABLE HAYFORD 16TH ALTA VISTA HIDALGO PINE DOVER INDIAN HILLS CHEYENNE SORORITY COMANCHE ALSOP TELEVISION 21ST MCCONNELL GRAFTON FRATERNITY KNADLER SOULE NELSON ALBIN HENRY KENDRICK TRABING BANOCK LESLIE DALE NORTHVIEW AMES ARAPHAHO CARRINGTON TULLIS SIOUX HILL KNADLER O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 11 Reach Designations Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 02/2012 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend Street Subbasin Boundary # Detention Pond Reach 1 2 3 4 5 6 7 8 9 0 1,200 2,400 600 Feet ---PAGE BREAK--- 15TH 3RD 9TH 287 HARNEY WILLETT 5TH 22ND REYNOLDS 4TH 6TH 7TH 8TH SHIELD LEWIS FLINT PINE 30TH IVINSON 11TH 10TH CLARK CANBY HILL 13TH GIBBON CEDAR LYON CURTIS BRADLEY 2ND 14TH 12TH 19TH HANCOCK SULLY DOWNEY BAKER RAILROAD MITCHELL FREMONT MILL 45TH INCA HODGEMAN 17TH UNIVERSITY 23RD BEAUFORT CROW NIGHTHAWK 18TH 1ST GRAND ARMORY DOVER APACHE BATH FRONTERA COE RENSHAW HAYFORD GRAYS GABLE 16TH ALTA VISTA HIDALGO GRANITO BINFORD 27TH 28TH 21ST NAVAJO INDIAN HILLS EDWARDS CHEYENNE SORORITY COMANCHE TELEVISION DUNA ALSOP DILLON LAND MCCONNELL SEETON GRAFTON FRATERNITY THOMES KNADLER HENRY SOULE NELSON ALBIN THAXTON KENDRICK TRABING SUPERIOR CT LESLIE BANOCK NOTTAGE NORTHVIEW AMES DIAMOND HEAD ARAPHAHO CARRINGTON SIOUX HILL O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 12 Areas of Flooding: 2- and 100-year Events Existing Percent Impervious Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 03/2012 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. 0 1,200 2,400 600 Feet Legend Street Subbasin Boundary Flooded Link 100-yr Storm 2- and 100-yr Storm Flooded Node 2- and 100-yr Storm 100-yr Storm Storage Existing Pond Existing Pond Flooded during 100-year ---PAGE BREAK--- 15TH 3RD 9TH 287 HARNEY 5TH WILLETT 22ND GRAND 4TH 6TH 7TH 8TH REYNOLDS SHIELD 30TH LEWIS FLINT PINE IVINSON 11TH 10TH CANBY HILL 13TH CLARK GIBBON 2ND LYON CURTIS BRADLEY 14TH 12TH 19TH HANCOCK BAKER SULLY RAILROAD MITCHELL GARFIELD FREMONT MILL 1ST 45TH INCA HODGEMAN DOWNEY 17TH UNIVERSITY 23RD BEAUFORT CROW HAYFORD 18TH KING DOVER ARMORY APACHE BATH FRONTERA COE NIGHTHAWK RENSHAW ALTA VISTA HIDALGO GRANITO BINFORD 27TH GRAYS GABLE 28TH 21ST 16TH NAVAJO INDIAN HILLS EDWARDS CHEYENNE SORORITY COMANCHE TELEVISION DUNA ALSOP DILLON LAND MCCONNELL SEETON GRAFTON FRATERNITY THOMES 20TH KNADLER SOULE NELSON HENRY ALBIN WARREN THAXTON KENDRICK TRABING SUPERIOR CT LESLIE BANOCK LODGEPOLE NOTTAGE NORTHVIEW AMES DIAMOND HEAD ARAPHAHO CARRINGTON SIOUX HILL O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 13 Areas of Flooding: 2- and 100-year Events Future Percent Impervious Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 02/2012 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend Street Subbasin Boundary Flooded Link 100-yr Storm 2- and 100-yr Storm Flooded Node 2-yr Storm 100-yr Storm Storage Existing Pond Existing Pond Flooded During 100-year 0 1,200 2,400 600 Feet ---PAGE BREAK--- # # # # # # # # # # 0 ac- ft 0 ac- ft 0 ac- ft 0 ac- ft 0 ac- ft 0 ac- ft 10 ac- ft 4.7 ac- ft 7.4 ac- ft 7.8 ac- ft 4.4 ac- ft 21.9 ac- ft +1.7 ac- ft +1.6 ac- ft +1.1 ac- ft +2.9 ac- ft 15TH 3RD 9TH 287 HARNEY WILLETT 5TH 22ND REYNOLDS 4TH 6TH 7TH 8TH SHIELD LEWIS FLINT 30TH 11TH 10TH CANBY HILL IVINSON 13TH GIBBON LYON CLARK BRADLEY 2ND 14TH 12TH 19TH HANCOCK BAKER SULLY CURTIS RAILROAD FREMONT MILL MITCHELL INCA DOWNEY UNIVERSITY 17TH BEAUFORT 23RD CROW 18TH 1ST ARMORY APACHE FRONTERA BATH COE BINFORD LAND NIGHTHAWK RENSHAW HAYFORD GRAYS GABLE 16TH HIDALGO ALTA VISTA GRANITO 27TH 28TH 21ST EDWARDS DOVER NAVAJO SORORITY TELEVISION CHEYENNE DUNA ALSOP DILLON MCCONNELL SEETON GRAFTON COMANCHE FRATERNITY INDIAN HILLS THOMES KNADLER SOULE NELSON COUGHLIN HENRY ALBIN THAXTON BONITA TRABING SUPERIOR CT BANOCK LESLIE TOLTEC NORTHVIEW NOTTAGE AMES DIAMOND HEAD ARAPHAHO CARRINGTON SIOUX FOX HILLTOP HANCOCK HAYFORD HILL CU01 CM02 CM01 RU06 CL05 LL01 RL02 RU01 CL06 LL07 LL09 CL02 CL03 RM02 LL04 RM06 LL08 RM11 RU04 RM08 RM10 RL03 CL07 RU02 LM02 CL08 RM03 RM07 CL04 RM09 RL01 RM05 LL02 RU03 RM04 LL06 LL03 CL01 LL10 CL09 RU05 LM01 LL05 RM01 O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 14 Upstream Improvements: Pond Modifications Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 09/2010 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. 0 1,200 2,400 600 Feet Legend Street Subbasin Boundary Parcel Existing Storm System flooded during 100-year Existing Storm System Pond Modification Type # New Pond Construction acre- feet) # Optimize Pond Outlet Structure # Enlarge Pond acre- feet) # Proposed Regional Detention Pond for Future Development acre-feet) Detention Required in Future Development See Alternatives (Figures 15-17) ---PAGE BREAK--- 15TH 3RD HARNEY 9TH REYNOLDS 4TH 287 SHIELD FLINT 22ND 5TH 11TH CANBY 10TH 13TH GIBBON 7TH LYON BRADLEY 6TH HILL 8TH PINE LEWIS 12TH 30TH 14TH HANCOCK CURTIS CEDAR BAKER 2ND SULLY DOWNEY MITCHELL RAILROAD MILL 19TH 17TH BEAUFORT 23RD NIGHTHAWK 18TH ARMORY BATH HODGEMAN RENSHAW 16TH BINFORD 27TH 28TH 21ST EDWARDS ALTA VISTA DOVER TELEVISION ALSOP DILLON MCCONNELL SEETON GRAFTON THOMES KNADLER BONITA COUGHLIN HAYFORD HENRY ALBIN THAXTON GRAYS GABLE TRABING SUPERIOR CT LESLIE DALE NOTTAGE AMES DIAMOND HEAD CARRINGTON RIDGEVIEW LINDSEY NEWTON FOX HILLTOP BATTLE DUTTON HANCOCK KNADLER 5'x8' RCBC 6'x20' RCBC 5'x10' RCBC 8'x8' RCBC 18" RCP 42" RCP 72" RCP 7'x9' RCBC 5'x16' RCBC 5'x20' RCBC 54" RCP 24" RCP 60" RCP 5x16 RCBC 6'x8' RCBC 6'x8' RCBC 5'x20' RCBC 24" RCP 54" RCP 24" RCP 60" RCP 18" RCP 6'x8' RCBC 24" RCP 5'x20' RCBC 60" RCP 24" RCP 8'x8' RCBC 18" RCP 60" RCP 24" RCP 36"x60" ERCP 24" RCP O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 15 Alternative 1: Upsize Existing Trunk Line Sewers Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 09/2010 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend Street Subbasin Boundary Existing Storm System Upsize Storm System Storm Sewer System Location Upstream 0 700 1,400 350 Feet ---PAGE BREAK--- 15TH HARNEY 3RD 9TH 4TH SHIELD 287 REYNOLDS FLINT CANBY HILL 13TH 22ND GIBBON 7TH LYON 11TH 10TH 5TH 6TH HANCOCK CURTIS CEDAR 2ND SULLY BAKER 8TH PINE MITCHELL 12TH MILL 14TH DOWNEY 17TH BEAUFORT 23RD RAILROAD 18TH 19TH RENSHAW 16TH BINFORD HODGEMAN BRADLEY EDWARDS 21ST ALSOP NIGHTHAWK DILLON MCCONNELL SEETON GRAFTON THOMES COUGHLIN HENRY ALBIN THAXTON TRABING SUPERIOR CT OWEN REDTAIL DOVER AMES DIAMOND HEAD CARRINGTON KNADLER NEWTON FOX HILLTOP DUTTON W HILL HANCOCK 6'x9' RCBC 6'x8' RCBC 60" RCP 36" RCP 54" RCP 30" RCP 18" RCP 42" RCP 48" RCP 36"x60" ERCP 18" HDPE 15" RCP 24" RCP 24" RCP 18" RCP 24" RCP 42" RCP 42" RCP 54" RCP 48" RCP 30" RCP 60" RCP 48" RCP 48" RCP 48" RCP 18" RCP 24" RCP 48" RCP 48" RCP 48" RCP 48" RCP 36" RCP 24" RCP 24" RCP 18" HDPE 15" RCP 24" RCP 24" RCP 24" RCP 24" RCP 30" RCP 15" RCP 18" R 18" RCP O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 16 Alternative 2: Additional Trunk Line Sewers Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 09/2010 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend Street Subbasin Boundary Existing System flooded during 100-year Existing Storm System Proposed Storm System Storm Sewer System Location Upstream 0 700 1,400 350 Feet ---PAGE BREAK--- 15TH HARNEY 3RD REYNOLDS 9TH 4TH SHIELD FLINT 287 CANBY HILL 13TH 22ND GIBBON 7TH 11TH 10TH 5TH LYON 6TH HANCOCK BAKER 2ND SULLY 8TH CURTIS 12TH 14TH MILL MITCHELL DOWNEY 17TH RAILROAD BEAUFORT 23RD 19TH BATH ARMORY 18TH RENSHAW PINE NIGHTHAWK 16TH BINFORD HODGEMAN 27TH 28TH 21ST EDWARDS TELEVISION ALSOP DILLON MCCONNELL SEETON GRAFTON THOMES BRADLEY HENRY KNADLER ALBIN DOVER THAXTON TRABING SUPERIOR CT COUGHLIN LESLIE DALE OWEN REDTAIL AMES DIAMOND HEAD CARRINGTON LINDSEY NEWTON FOX HILLTOP BATTLE DUTTON W HILL HANCOCK KNADLER 48" RCP 6'x12' RCBC 8'x8' RCBC 18" RCP 42" RCP 7'x9' RCBC 72" RCP 5'x12' RCBC 54" RCP 24" RCP 60" RCP 6'x8' RCBC 5'x14' RCBC 60" RCP 8'x8' RCBC 5'x14' RCBC 6'x8' RCBC 24" RCP 6'x8' RCBC 24" RCP 24" RCP 24" RCP 24" RCP 18" RCP 5'x12' RCBC 60" RCP 54" RCP 5'x12' RCBC 60" RCP 24" RCP 24" RCP 48" RCP 18" RCP 60" RCP 5'x14' RCBC O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 17 Alternative 3: LaBonte Discharge and Upsize Trunk Line Sewers Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 09/2010 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend Street Subbasin Boundary Existing Storm System Upsize Storm System Storm Sewer System Location Upstream 0 700 1,400 350 Feet ---PAGE BREAK--- # # # # # # # # # # # 6'x8' RCBC 42" RCP 5'x8' RCBC 5'x10' RCBC 5'x8' RCBC 60" RCP 60" RCP 6'x8' RCBC 48" RCP 18" RCP 4'x10'' RCBC 18" RCP 42" RCP 4'x8' RCBC 54" RCP 24" RCP 60" RCP 36" RCP 4'x10' RCBC 48" RCP 60" RCP 24" RCP 60" RCP 60" RCP 42" RCP 54" RCP 4'x8' RCBC 60" RCP 60" RCP 24" RCP 54" RCP 24" RCP 24" RCP 18" RCP 60" RCP 4'x10' RCBC 54" RCP 24" RCP 36" RCP 4'x10' RCBC 5'X10' RCBC 24" RCP 24" RCP 4'x8' RCBC 36" RCP 0 ac- ft 0 ac- ft 0 ac- ft 0 ac- ft 0 ac- ft 0 ac- ft 10 ac- ft 4.7 ac- ft 7.4 ac- ft 7.8 ac- ft 4.4 ac- ft 21.9 ac- ft +1.7 ac- ft +1.6 ac- ft +1.1 ac- ft +1.7 ac- ft +36.4 ac-ft CU01 RU06 CM02 CM01 CL05 RL02 CL06 RU01 LL01 CL02 LL07 CL03 LL09 RM02 RM06 RM11 LL04 RU04 LL08 RM08 RL03 CL07 RM10 RU02 CL08 LM02 RM03 RM07 CL04 RL01 RM09 RM05 RU03 LL02 RM04 CL01 LL06 LL03 CL09 RU05 LM01 LL05 LL10 RM01 15TH 3RD 9TH 287 HARNEY 5TH WILLETT 22ND 4TH 6TH 7TH GRAND 8TH REYNOLDS 30TH LEWIS FLINT SHIELD IVINSON 11TH 10TH CANBY HILL 13TH GIBBON 2ND LYON CLARK CURTIS BRADLEY 14TH 12TH 19TH BAKER SULLY RAILROAD MITCHELL FREMONT MILL 45TH 1ST INCA DOWNEY GARFIELD UNIVERSITY 17TH BEAUFORT 23RD CROW NIGHTHAWK 18TH KING ARMORY DOVER FRONTERA BATH COE BINFORD LAND RENSHAW HAYFORD HIDALGO GRANITO GRAYS GABLE 27TH 21ST 16TH ALTA VISTA INDIAN HILLS APACHE CHEYENNE SORORITY JOANNA BRUNER COMANCHE TELEVISION DUNA ALSOP DILLON MCCONNELL GRAFTON FRATERNITY KNADLER 20TH SOULE NELSON TOLTEC ALBIN WARREN ARROWHEAD THAXTON EMPINADO TRABING COUGHLIN BANOCK NORTHVIEW AMES ARAPHAHO SIOUX WYMAN SUNDANCE HILL O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 18 Recommended Plan Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 03/2012 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend Street Subbasin Boundary Reach 1 (100-yr Design) 2 (100-yr Design) 3 (100-yr Design) 4 (100-yr Design) 5 (100-yr Design) 6 (100-yr Design) 7 (100-yr Design) 8 (10-yr Design) 9 (100-yr Design) Area of Regrade Existing Storm Sewer Upsize/ New Storm Sewer Pond Modification Type # New Pond Construction acre- feet) # Optimize Pond Outlet Structure # Enlarge Pond acre- feet) # Proposed Regional Detention Pond for Future Development acre-feet) 0 700 1,400 350 Feet Note: All ponds drain within 48 hours. ---PAGE BREAK--- O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 19 Recommended Plan - Proposed Pond Contours Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 03/2012 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. 0 200 400 100 Feet 15TH HARNEY CANBY GIBBON LM02 LL01 LM01 7186 7184 7182 17TH REYNOLDS 18TH 19TH HANCOCK RM06 RM11 RM09 7180 7178 10TH 13TH BEAUFORT CM02 CL05 CL03 CL06 7166 7164 7162 30TH REYNOLDS KNADLER HAYFORD RU04 RM01 RM02 RU05 RM03 7228 7226 7224 7240 7238 7236 Notes: 1. Tie proposed contours into existing at edge of pond. 2. Maintain existing bottom elevation of pond. Notes: 1. Tie proposed contours into existing at edge of pond. 2. Maintain existing bottom elevation of pond. Notes: RU05 1. Tie proposed contours into existing at edge of pond. 2. Maintain existing bottom elevation of pond. RM02 1. Tie proposed contours into existing at edge of pond. 2. Pond dimensions are approximate and could be changed based on future development. Notes: 1. Tie proposed contours into existing at edge of pond. 2. Maintain existing bottom elevation of pond. LaBonte Park Pond Typical Cross Section A-a N.T.S. Legend Street Parcel Boundary Flood 10-Year Storm 100-Year Storm Subbasin Boundary 7144 7146 7146 7146 # # PROPOSED BERM # H 9TH CANBY SHIELD 7TH 6TH 8TH 5TH SULLY LL10 RL02 LL04 LL05 LL06 LL03 Notes: 1. Tie proposed berm contours into existing. 2. No proposed modifications to existing pond. 3. Improvements involve regrading of 9th St. and along trail as shown. 4. Note that the proposed improvements below will result in NO FREEBOARD. A a Legend Estimated Area of Regrading ---PAGE BREAK--- # # # # # # # # # # # 6'x8' RCBC 6'x8' RCBC 4'x10'' RCBC 4'x8' RCBC 54" RCP 36" RCP 4'x10' RCBC 5'x14' RCBC 60" RCP 60" RCP 42" RCP 4'x8' RCBC 60" RCP 60" RCP 60" RCP 6'x12' RCBC 72" RCP 54" RCP 4'x10' RCBC 5'x14' RCBC 42" RCP 4'x8' RCBC 36" RCP 0 ac- ft 0 ac- ft 0 ac- ft 0 ac- ft 0 ac- ft 0 ac- ft 10 ac- ft 4.7 ac- ft 7.4 ac- ft 7.8 ac- ft 4.4 ac- ft 21.9 ac- ft +1.7 ac- ft +1.6 ac- ft +1.1 ac- ft +1.7 ac- ft +36.4 ac-ft CU01 CM02 CM01 RU06 CL05 RL02 CL06 LL01 CL02 RU01 LL07 CL03 LL09 RM02 RM06 LL04 LL08 RM11 RM08 RL03 RU04 CL07 RM10 CL08 RM03 RU02 LM02 RM07 CL04 RL01 RM09 RM05 LL02 RM04 CL01 LL06 RU03 LL03 CL09 RU05 LL05 LL10 LM01 RM01 15TH 3RD 9TH 287 HARNEY 5TH WILLETT 22ND 4TH 6TH 7TH GRAND 8TH REYNOLDS SHIELD 30TH LEWIS FLINT PINE IVINSON 11TH 10TH CANBY HILL 13TH CLARK GIBBON 2ND LYON CURTIS BRADLEY 14TH 12TH 19TH HANCOCK BAKER SULLY RAILROAD MITCHELL FREMONT MILL HODGEMAN 45TH 1ST INCA DOWNEY GARFIELD UNIVERSITY 17TH BEAUFORT 23RD CROW NIGHTHAWK 18TH KING ARMORY DOVER FRONTERA BATH COE LAND RENSHAW HAYFORD ALTA VISTA HIDALGO GRANITO BINFORD GRAYS GABLE 27TH 16TH INDIAN HILLS APACHE CHEYENNE SORORITY JOANNA BRUNER COMANCHE TELEVISION 21ST DUNA ALSOP DILLON MCCONNELL GRAFTON FRATERNITY KNADLER 20TH SOULE NELSON COUGHLIN TOLTEC ALBIN WARREN ARROWHEAD THAXTON EMPINADO TRABING BANOCK NORTHVIEW AMES ARAPHAHO CARRINGTON SIOUX WYMAN SUNDANCE HANCOCK HILL O Map Document: P:\KO\L\LARAM\112351\4.0 Hydrologic and Hydraulic Analysis\GIS\Maps NORTH LARAMIE DRAINAGE MASTER PLAN Laramie, Wyoming FIGURE 20 Recommended Phasing Plan Map by: KRJ Projection: NAD_1983_StatePlane_Wyoming_East_FIPS_4901_Feet Source: Project Number: LARAM 112351 Print Date: 03/2012 This map is neither a legally recorded map nor a survey map and is not intended to be used as one. This map is a compilation of records, information, and data gathered from various sources listed on this map and is to be used for reference purposes only. SEH does not warrant that the Geographic Information System (GIS) Data used to prepare this map are error free, and SEH does not represent that the GIS Data can be used for navigational, tracking, or any other purpose requiring exacting measurement of distance or direction or precision in the depiction of geographic features. The user of this map acknowledges that SEH shall not be liable for any damages which arise out of the user's access or use of data provided. Legend Street Subbasin Boundary Phase # 1 # 2 # 3 # 4 # 6 # As-needed 5 6 7 8 9 0 700 1,400 350 Feet ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Appendices Appendix A – Public Meeting Comments Appendix B – Survey Notes Appendix C – Inventory of Existing Storm Structures (To be included in final document) Appendix D – Geotechnical Report Appendix E – CUHP Input Appendix F – Detention Pond Calculations Appendix G – Input/ Output – Existing Conditions Appendix H – Input/ Output – Future Conditions Appendix I – Rainfall Data Appendix J – Conceptual Solution Scoring Matrix Appendix K – Conceptual Outfall at Harney Street ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Appendix A – Public Meeting Comments ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Appendix B – Survey Notes ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Appendix C – Inventory of Existing Storm Structures ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Appendix D – Geotechnical Report ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Appendix E – CUHP Input ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- North Laramie Drainage Master Plan Summary of CUHP Input Parameters (Version 1.3.3) Catchment Name/ID Raingage Name/ID Area (sq.mi.) Dist. to Centroid (miles) Length (miles) Slope (ft./ft.) Percent Imperv. Pervious (inches) Imperv. (inches) Initial Rate (in./hr.) Final Rate (in.hr.) Decay Coeff. (1/sec.) DCIA Level Dir. Con'ct Imperv. Fraction Receiv. Perv. Fraction Percent Eff. Imperv. CL 100 0.256 0.355 0.629 0.023 0.1 0.35 0.10 3.99 0.55 0.0018 0.00 0.00 0.00 0.09 RU 100 0.394 0.374 0.926 0.030 0.4 0.35 0.10 3.49 0.53 0.0018 0.00 0.01 0.00 0.29 CU 100 0.415 0.426 0.880 0.054 0.0 0.35 0.10 3.69 0.55 0.0018 0.00 0.00 0.00 0.02 Depression Storage Horton's Infiltration Parameters DCIA Level and Fractions SEH 11/20/2010 CUHP Input Parameters ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Appendix F – Detention Pond Calculations ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- North Laramie Drainage Master Plan CM02 Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Existing Elevation above Invert Elevation, h Area, A (sf) Area, A (acres) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7161.09 0 7161.09 0 0 0 0 0 Spill Elev = 7164.85 0.91 7162 13176.00 0.303 3996.72 3997 0.09 2.91 7164 46590.00 1.07 56361.60 60358 1.39 Approximate Total Volume = 84312 1.9 Proposed Elevation above Invert Elevation, h Area, A (sf) Area, A (acres) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7161.09 0 7161.09 0 0 0 0 0 Spill Elev = 7165.5 0.91 7162 15930.00 0.366 4832.10 4832 0.11 2.91 7164 77744.00 1.785 85910.53 90743 2.08 4.91 7166 84596.00 1.943 162291.78 253034 5.81 Approximate Total Volume = 212461 4.9 SEH 4/4/2012 Detention Pond CM02 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan LM01 Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Existing Elevation above invert Elevation, h Area, A (sf) Area, A (acres) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7180.98 0 7180.98 0 0 0 0 0 Spill Elev = 7185.52 3.02 7184 18587 0.427 18710.91 18711 0.43 5.02 7186 35824.00 0.823 53476.85 72188 1.66 Approximate Total Volume = 59353 1.4 Proposed Elevation above invert Elevation, h Area, A (sf) Area, A (acres) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) 0 7180.98 0.00 0 0.00 0 0.00 1.02 7182 11529.00 0.265 3919.86 3920 0.09 3.02 7184 36315.00 0.834 45537.04 49457 1.14 5.02 7186 42060.00 0.966 78304.72 127762 2.93 Approximate Total Volume = 108968 2.5 SEH 4/4/2012 Detention Pond LM01 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan LM02 Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Existing Elevation above invert Elevation, h Area, A (sf) Area, A (acres) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7180.95 0 7180.95 0 0 0.00 0 0.00 Spill Elev = 7184.69 3.05 7184 30210 0.694 30713.50 30714 0.71 5.05 7186 63756.00 1.464 91902.00 122615 2.81 Approximate Total Volume = 62420 1.4 SEH 4/4/2012 Detention Pond LM02 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan RM02 Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Existing Elevation above invert Elevation, h Area, A (sf) Area, A (acres) Volume (cu-ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7192.86 0 7192.86 0 0 0 0 0 Spill Elev = 7196.28 1.14 7194 84982 1.951 32293.16 32293 0.74 3.14 7196 191763.00 4.403 269601.58 301895 6.93 Approximate Total Volume = 339639 7.8 Additional Pond Elevation above invert Elevation, h Area, A (sf) Area, A (ac) Volume (cu-ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7223 0 7223 0 0 0 0 0 Spill Elev = 7228 1 7224 55316 1.27 18438.67 18439 0.42 3 7226 118960 2.731 170263.74 188702 4.33 5 7228 127570.00 2.929 246479.87 435182 9.99 Approximate Total Volume = 435182 10.0 SEH 4/4/2012 Detention Pond RM02 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan RM03 Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Existing Elevation above invert Elevation, h Area, A (sf) Area, A (acres) Volume (cu-ft) Cumulative Volume (cu- ft) Cumulative Volume (acre-ft) Invert Elev= 7201.05 0 7201.05 0 0 0 0 0 Spill Elev = 7204.53 0.95 7202 58863 1.352 18639.95 18640 0.43 2.95 7204 76534.00 1.757 135010.97 153651 3.53 Approximate Total Volume = 191664 4.4 SEH 4/4/2012 Detention Pond RM03 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan RM06 Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Existing Elevation above invert Elevation, h Area, A (sf) Area, A (acres) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7176.5 0 7176.5 0 0 0 0 0 Spill Elev = 7181.57 1.5 7178 1632 0.038 816.00 816 0.02 3.5 7180 59061.00 1.356 47007.14 47823 1.10 5.5 7182 84448.00 1.939 142754.55 190578 4.38 Approximate Total Volume = 159885 3.7 Proposed Elevation above invert Elevation, h Area, A (sf) Area, A (acres) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) 0 7176.5 0 0 0 0 0 1.5 7178 30140 0.692 15070.00 15070.00 0.35 3.5 7180 66523.00 1.528 94293.51 109363.51 2.51 5.5 7182 84448.00 1.939 150615.03 259978.54 5.97 Approximate Total Volume = 227596 5.2 SEH 4/4/2012 Detention Pond RM06 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan RM07 Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Existing Elevation above invert Elevation, h Area, A (sf) Area, A (acres) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7188.51 0 7188.51 0 0 0 0 0 Spill Elev = 7193 1.49 7190 33975 0.78 16874.25 16874 0.39 3.49 7192 47381.00 1.088 80985.29 97860 2.25 Approximate Total Volume = 138352 3.2 SEH 4/4/2012 Detention Pond RM07 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan RM08 Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Existing Elevation above invert Elevation, h Area, A (sf) Area, A (acres) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7203.19 0 7203.19 0 0 0 0 0 Spill Elev = 7212.02 0.81 7204 385 0.009 103.95 104 0.00 2.81 7206 33083.00 0.76 24691.26 24795 0.57 4.81 7208 47239.00 1.085 79902.91 104698 2.40 6.81 7210 54171.00 1.244 101330.93 206029 4.73 8.81 7212 61890.00 1.421 115975.34 322004 7.39 Approximate Total Volume = 322004 7.4 SEH 4/4/2012 Detention Pond RM08 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan RU04 Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Existing Elevation above invert Elevation, h Area, A (sf) Area, A (ac) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7232.56 0 7232.56 0 0 0 0 0 Spill Elev = 7240.43 1.44 7234 15402 0.354 7392.96 7393 0.17 3.44 7236 81990.00 1.883 88618.69 96012 2.20 5.44 7238 92493.00 2.124 174377.53 270389 6.21 7.44 7240 102892.00 2.363 195292.69 465682 10.69 Approximate Total Volume = 507670 11.7 SEH 4/4/2012 Detention Pond RU04 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan RU05 Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Existing Elevation above invert Elevation, h Area, A (sf) Area, A (ac) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7233.11 0 7233.11 0 0 0 0 0 Spill Elev = 7240.42 2.89 7236 6969 0.16 6713.47 6713 0.15 4.89 7238 10831.00 0.249 17658.66 24372 0.56 6.89 7240 15302.00 0.352 26004.57 50377 1.16 Approximate Total Volume = 55838 1.3 Proposed Elevation above invert Elevation, h Area, A (sf) Area, A (ac) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) 0 7233.11 0.00 0 0 0 0 2.89 7236 20949.00 0.481 20180.87 20181 0.46 4.89 7238 24834.00 0.571 45727.96 65909 1.51 6.89 7240 29021.00 0.667 53800.66 119709 2.75 Approximate Total Volume = 131008 3.0 SEH 4/4/2012 Detention Pond RU05 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan CL04 Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Proposed Elevation above invert Elevation, h Area, A (sf) Area, A (ac) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7175 0 7175 0.00 0 0 0 0 Spill Elev = 7180 1 7176 47366.00 1.088 15788.67 15789 0.36 3 7178 52829.00 1.213 100145.32 115934 2.66 5 7180 58581.00 1.345 111360.47 227294 5.22 Approximate Total Volume = 216079 5.0 SEH 4/4/2012 Detention Pond CL04 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan LL10 (LaBonte Park Pond) Volume = 1/3*(h2‐h1)*(A1+A2+(A1A2)0.5) Existing Elevation above invert Elevation, h Area, A (sf) Area, A (ac) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7140.43 0 7140.43 0.00 0 0 0 0 Spill Elev = 7144.3 1.57 7142 284566.00 6.533 148922.87 148923 3.42 3.57 7144 319408.00 7.333 603638.73 752562 17.28 5.57 7146 468773.00 10.762 783420.27 1535982 35.26 Approximate Total Volume = 870075 20.0 Proposed Elevation above invert Elevation, h Area, A (sf) Area, A (ac) Volume (cu- ft) Cumulative Volume (cu-ft) Cumulative Volume (acre-ft) Invert Elev= 7140.43 0 7140.43 0.00 0 0 0 0 Spill Elev = 7147 1.57 7142 284566.00 6.533 148922.87 148923 3.42 3.57 7144 319408.00 7.333 603638.73 752562 17.28 5.57 7146 695346.00 15.963 990685.26 1743247 40.02 6.57 7147 733420.00 16.838 714298.43 2457545 56.42 7.57 7148 772347.00 17.731 752799.62 3210345 73.70 Approximate Total Volume = 2457545 56.4 SEH 4/4/2012 Detention Pond LL10 Volume Calculation ---PAGE BREAK--- North Laramie Drainage Master Plan January 2013 Short Elliott Hendrickson Inc. Appendix G – Input/ Output – Existing Conditions ---PAGE BREAK--- THIS PAGE INTENTIONALLY LEFT BLANK ---PAGE BREAK--- North Laramie Drainage Master Plan HORTON INFILTRATION PARAMETERS SCS Infiltration (in/hr) Decay Soil Type Fi Fo Coeff. <