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Home My WebLink AboutLEGACY AUTO - FDP - FDP170014 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTPrepared for: Mr. Gary Farkas Legacy Tractor and Auto Sales 1845 N. College Avenue Fort Collins, Colorado 80524 Prepared by: Wohnrade Civil Engineers, Inc. 11582 Colony Row Broomfield, CO 80021 Phone: (720)259-0965, Fax: (720)259-1519 Project Number: 1707.00-LEG Drainage Design Considerations for the Legacy Auto Final Development Plan (FDP) Fort Collins, Colorado June 21, 2017 June 21, 2017 Mr. Wes Lamarque Utilities Department City of Fort Collins 700 Wood Street Fort Collins, Colorado 80522 Re: Drainage Design Considerations for the Legacy Auto FDP Fort Collins, Colorado Dear Mr. Lamarque: Wohnrade Civil Engineers, Inc. (WCE) is pleased to resubmit this final hydrologic and hydraulic report for the Legacy Tractor and Auto Sales project for your review. We have addressed the first round of comments contained in the letter dated June 16, 2017. This report complies with technical criteria set forth in the City of Fort Collins, Stormwater Criteria Manual, and Urban Drainage and Flood Control District criteria. We acknowledge that the City of Fort Collins’s review of this study is only for general conformance with submittal requirements, current design criteria, and standard engineering principles and practices. If you should have any questions or comments as you review this report, please feel free to contact me at your convenience. Sincerely, WOHNRADE CIVIL ENGINEERS, INC Mary B. Wohnrade, P.E. - Principal Professional Engineer - (CO, NV) Wohnrade Civil Engineers, Inc. 11582 Colony Row, Broomfield, CO 80021 Phone: 720-259-0965, Fax: 720-259-1519 Drainage Design Considerations for Legacy Auto FDP Table of Contents 1. INTRODUCTION .............................................................................................................................. 1 1.1 Objective ............................................................................................................................................. 1 1.2 Project History and Previous Studies .................................................................................................. 1 1.3 Mapping and Surveying ....................................................................................................................... 1 2. SITE LOCATION AND DESCRIPTION ........................................................................................ 1 2.1 Site Location ........................................................................................................................................ 1 2.1 Site Description ................................................................................................................................... 2 3. PRE-PROJECT CONDITIONS ........................................................................................................ 2 3.1 Pre-Project Drainage Basins ................................................................................................................ 2 3.2 Pre-Project Drainage Patterns ............................................................................................................. 2 4. POST-PROJECT CONDITIONS ..................................................................................................... 2 4.1 Proposed Project Description .............................................................................................................. 2 4.2 Post-Project Drainage Basins ............................................................................................................... 3 4.3 Post-Project Drainage Patterns ........................................................................................................... 3 4.4 Proposed Detention/Water Quality Pond ........................................................................................... 3 5. DESIGN CRITERIA .......................................................................................................................... 4 5.1 Design References ............................................................................................................................... 4 5.2 Hydrologic Criteria ............................................................................................................................... 4 6. EROSION CONTROL ....................................................................................................................... 5 6.1 Erosion Control Plan ............................................................................................................................ 5 6.2 Site Stabilization .................................................................................................................................. 5 7. CONCLUSIONS ................................................................................................................................. 5 7.1 Compliance with Standards ................................................................................................................. 5 7.2 Variances ............................................................................................................................................. 6 8. REFERENCES .................................................................................................................................... 6 Drainage Design Considerations for Legacy Auto FDP TABLE OF CONTENTS, cont. Vicinity Map APPENDICES Appendix A: Post-Project Condition Hydrology Appendix B: Detention/Water Quality Pond Design DRAWINGS Sheet 1 of 2 Pre-Project Drainage Plan Sheet 2 of 2 Post-Project Drainage Plan Drainage Design Considerations for Legacy Auto FDP Fort Collins, Colorado June 21, 2017 1. INTRODUCTION 1.1 Objective This study documents the results of a comprehensive hydrologic and hydraulic analysis for the proposed Legacy Tractor and Auto Sales FDP project located in Fort Collins, Colorado. The project includes a 10,500 sf building addition, new water and sewer services lines, site improvements, and an onsite stormwater detention/water quality pond (Photo 1). 1.2 Project History and Previous Studies There is one known hydrologic and hydraulic study for the Legacy Tractor property. A Final Drainage and Erosion Control Report for Legacy Auto was prepared by North Star Design as part of the Preliminary Development Plan, and is dated April 4, 2014. 1.3 Mapping and Surveying King Surveying, of Windsor, Colorado, provided field survey information and topographic mapping of the project site, with a contour interval of 1-foot. The survey was performed in January 2010, and was referenced to NGS Monuments U402 and V401 on the NAVD88 datum, and the NAD 83, Colorado State Plane (UTM Zone 13) North Zone survey coordinate system. 2. SITE LOCATION AND DESCRIPTION 2.1 Site Location The project is located in the Southeast ¼ of Section 35, Township 8 North, and Range 69 West of the 6th Principal Meridian, City of Fort Collins, Larimer County, Colorado. The site is bounded by N. College Avenue on the east, the Larimer and Weld Canal on the north, and existing commercial properties on the west and south. The project is located outside of any FEMA regulated floodplain, as per the FEMA Flood Photo 1 – Project Site Looking Northeast Legacy Auto FDP June 21, 2017 Page 2 Wohnrade Civil Engineers, Inc. Insurance Rate Map(FIRM), Community-Panel Number 08069C-0977G, revised on June 17, 2008 (see Firmette). The property is also adjacent to a City of Fort Collins designated floodplain along the Larimer and Weld Canal. Floodplain mapping contained on the online mapping application FCMaps shows that this floodplain is contained within the banks of the Larimer and Weld Canal, and does not encroach onto the project site. 2.1 Site Description The project site is roughly 2.91 acres in size, and is located in a commercial area within the City of Fort Collins, Colorado. The site is partially developed on the east side of the property adjacent to N. College Avenue, and contains an existing structure with paved and gravel parking, and utilities. The existing site drains to a depression located in the southwest corner of the site, with no discernable outlet. The site is located in the Dry Creek Drainage Basin, as defined by the City of Fort Collins Master Drainage Plan. Stormwater runoff from offsite properties (0.68 acres) enters the site on the north, south and west. 3. PRE-PROJECT CONDITIONS 3.1 Pre-Project Drainage Basins The existing project site includes one single drainage basin, for a total area of 2.91 acres. 3.2 Pre-Project Drainage Patterns Stormwater runoff from the entire property drains overland, across paved and vegetated surfaces, to the existing depression located in the southwest corner of the property where stormwater is retained onsite. Runoff calculations for the pre-project condition have not been performed, since the maximum allowable developed release rate is a fixed 0.20 cfs/acre, and is independent of the historic discharges. 4. POST-PROJECT CONDITIONS 4.1 Proposed Project Description The proposed project includes a new 10,500 sf building addition, new asphalt parking and drives, new underground utilities, and a new onsite stormwater detention/water quality facility. Legacy Auto FDP June 21, 2017 Page 3 Wohnrade Civil Engineers, Inc. The existing building will remain, but all other paving and utilities will be removed. 4.2 Post-Project Drainage Basins The proposed project site has been divided into 2 post-project drainage basins for a total drainage area of 2.91 acres. Post-project drainage basins and patterns will mimic pre-project conditions, with Basin1 draining to the southwest corner of the property to the new detention facility, and Basin 2 draining to the existing depression, which is also located in the southwest corner of the property. 4.3 Post-Project Drainage Patterns Basins 1 (2.80 ac) drains overland in vertical curb and gutter and valley pans, at slopes ranging from 0.44% to 4.53%, to the new detention facility. The drainage pattern within this basins mimics pre-project drainage patterns. The 10 and 100-year peak discharges are estimated to be 6.9 cfs and 16.1 cfs respectively. Basin 2 (0.11 ac) drains overland across a native grass area to the existing depression located in the southwest corner of the property. The drainage pattern within this basins mimics pre-project drainage patterns. The 10 and 100-year peak discharges are estimated to be 0.2 cfs and 0.5 cfs respectively. Offsite Basins O1 and O3 will also drain to the new detention/water quality facility. Stormwater runoff from these basins will be conveyed by overland flow across vegetated surfaces. The 10 and 100-year peak inflow to the detention pond from Basins 1, O1, and O3 (3.28 ac) are estimated to be 3.7 cfs and 18.8 cfs respectively. Calculations made as part of this investigation, along with other supporting material, are contained in Appendix A. 4.4 Proposed Detention/Water Quality Pond The proposed detention/water quality pond is located in the southwest corner of the property, near the existing depression. The pond will detain stormwater runoff from Basin 1 of the developed site, as well as, offsite Basins O1 and O3, which are located to the south and west of the property. The property lies within the Dry Creek Drainage Basin, which requires runoff from the 100-year developed storm to be released at a maximum rate of 0.20 cfs/ac. Stormwater runoff from onsite Basin 1, and offsite Basins O1 and O3 will be released at this rate. The maximum allowable release is 0.20 cfs/ac x 3.28 acres= 0.66 cfs. The computer program, Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2016 was used to route the 100-year design storm through the detention pond. An inflow Legacy Auto FDP June 21, 2017 Page 4 Wohnrade Civil Engineers, Inc. hydrograph was developed to route the 100-year storm through the detention pond, which includes Basins 1, O1 and O3 (3.28 acres). Results of the pond routing predict a maximum 100-yr water surface elevation of 4982.79, with an associated storage requirement of 11,417 cu-ft. A 4” diameter orifice will control the release of developed stormwater runoff at a maximum rate of 0.47 cfs. The 100-year storm was routed through the pond, beginning at an elevation of 4982.00, which is the top of the Water Quality Capture Volume (WQCV). An emergency pond overflow weir has also been designed to pass the 100-year peak inflow (18.8 cfs) to the pond. The notch elevation of the weir will be set at an elevation of 4983.00, and will be 5’ in width. The weir will direct stormwater runoff to the historic location, which is the existing depression in the southwest corner of the site, where it will be retained onsite. Extended detention has also been incorporated into the detention pond design. The computer programs, UD-Detention (v3.07) and UD-BMP (v3.05), developed by the Urban Drainage and Flood Control District (UDFCD), have been used to calculate the required Water Quality Capture Volume (WQCV), and orifice size based on a 40-hour drain time. Based on the UD-Detention and UD_BMP spreadsheets, the calculated WQCV is 0.051 ac-ft, which, based on the pond stage-storage rating, translates to a water surface elevation of 4981.98, (or 4982.00), and design volume depth of 0.65’. The WQCV orifice plate will contain one column with 3- 7/16” diameters orifices. The pond outlet structure has been designed to mimic Figure OS-8 by Urban Drainage. Calculations made as part of this pond analysis, along with other supporting material, are contained in Appendix B. 5. DESIGN CRITERIA 5.1 Design References Drainage design criteria outlined in the City of Fort Collins Stormwater Criteria Manual (Reference 1), and the Urban Storm Drainage Criteria Manual by the Urban Drainage and Flood Control District (Reference 2), have been referenced in the preparation of this study. 5.2 Hydrologic Criteria Due to the relatively small basin size, and in keeping with criteria set forth in the City of Fort Collins, Stormwater Criteria Manual, the Rational Method has been used to estimate peak stormwater runoff from the project site. Legacy Auto FDP June 21, 2017 Page 5 Wohnrade Civil Engineers, Inc. The initial 2 and 10-year, and major 100-year design storms have been used to evaluate the proposed drainage system. Rainfall intensity data for the Rational Method has been taken from IDF equations generated specifically for the project site using the Hydraflow Hydrographs Extension computer software from Autodesk. Point precipitation frequency estimates were generated using the NOAA Atlas 14, Precipitation Data Frequency Server, which are site specific. 6. EROSION CONTROL 6.1 Erosion Control Plan A proposed rainfall erosion control plan during construction will consist of temporary structural erosion control measures. Erosion control measures have been specified on the Grading and Erosion Control Plan, and on three separate drawings contained in the written Stormwater Management Plan (SWMP). These drawings include a Pre-disturbance, Interim, and Final Stabilization Plans. Based on requirements set forth in the 2014 Preliminary Development Plan, Low Impact Development (LID) design criteria will not be required for this project. Wohnrade Civil Engineers, Inc. has prepared a separate report containing the Stormwater Management Plan (SWMP) for this project. A Colorado Discharge Permit System (CDPS), Stormwater Discharge Associated with Construction Activities application has also been submitted to the Colorado Department of Public Health and Environment. A City of Fort Collins Erosion and Sediment Control Escrow/Security Calculation has been prepared for this project, and is included in the written SWMP report. 6.2 Site Stabilization All areas disturbed by construction will be landscaped, paved, or re-seeded using the recommended seed varieties, quantities, and application rates as specified on the project Landscape Plan. 7. CONCLUSIONS 7.1 Compliance with Standards The proposed drainage improvements been designed to comply with all applicable drainage criteria, in accordance with the City of Fort Collins Stormwater Criteria Manual. Legacy Auto FDP June 21, 2017 Page 6 Wohnrade Civil Engineers, Inc. 7.2 Variances There are no variances requested as part of this stormwater drainage design. 8. REFERENCES 1. Stormwater Criteria Manual, City of Fort Collins, adopted December 2011. 2. Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, Denver, Colorado, Revised April 2008. 3. CDOT Drainage Design Manual, Colorado Department of Transportation. 4. Geotechnical Investigation, Proposed Detention Pond, CTL Thompson, Inc., January 29, 2015. PROJECT LOCATION Appendix A Legacy Auto Final Development Plan (FDP) May 10, 2017 Page 1 of 3 Wohnrade Civil Engineers, Inc. Composite Percentage Imperviousness Calculations: Post-Project Condition, Basin 1 NRCS Soil Type D Surface Characteristics Streets: Paved Streets: Gravel Drives and Walks Roofs Lawns Clayey Soil Imperviousness Area (acres) 0.000 0.000 1.070 0.240 1.49 0.43 Percent Imperviousness 100 40 90 90 2 Total Area (acres) 2.80 Correction Factors KA and KCD for Use With Equations RO-6 and RO-7 NRCS Soil Type 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year C and D 0.000 0.067 0.132 0.209 0.258 0.292 A 0.000 0.055 0.110 0.158 0.185 0.212 Equations RO-6 and RO-7, Drainage Criteria Manual, Volume 1 CA 0.21 0.26 0.32 0.37 0.39 0.42 CB 0.25 0.31 0.37 0.44 0.47 0.50 CCD 0.30 0.36 0.43 0.51 0.55 0.59 Equations taken from Urban Storm Drainage Criteria Manual, Volume 1, Chapter 5, Section 2.7, by the Urban Drainage and Flood Control District, Denver, Colorado Post-Project Condition, Basin 2 NRCS Soil Type D Surface Characteristics Streets: Paved Streets: Gravel Walks and Patios Roofs Lawns Clayey Soil Imperviousness Area (acres) 0 0.00 0.00 0.00 0.11 0.02 Percent Imperviousness 100 40 96 90 2 Total Area (acres) 0.11 Correction Factors KA and KCD for Use With Equations RO-6 and RO-7 NRCS Soil Type 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year C and D 0.000 0.108 0.206 0.324 0.393 0.452 A 0.000 0.088 0.167 0.236 0.276 0.315 Equations RO-6 and RO-7, Drainage Criteria Manual, Volume 1 CA 0.00 -0.01 0.07 0.14 0.18 0.22 CB 0.03 0.08 0.17 0.26 0.31 0.36 CCD 0.06 0.16 0.26 0.38 0.45 0.51 S:\PROJECTS\LEG\DRNG\LEG-DevC.wpd Legacy Auto Final Development Plan (FDP) May 10, 2017 Page 2 of 3 Wohnrade Civil Engineers, Inc. Post-Project Condition, Basin O1 NRCS Soil Type D Surface Characteristics Streets: Paved Streets: Gravel Walks and Parking Roofs Lawns Clayey Soil Imperviousness Area (acres) 0 0.00 0.00 0.05 0.28 0.15 Percent Imperviousness 100 40 90 90 2 Total Area (acres) 0.33 Correction Factors KA and KCD for Use With Equations RO-6 and RO-7 NRCS Soil Type 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year C and D 0.000 0.095 0.182 0.287 0.349 0.400 A 0.000 0.078 0.149 0.211 0.246 0.282 Equations RO-6 and RO-7, Drainage Criteria Manual, Volume 1 CA 0.02 0.10 0.17 0.24 0.27 0.31 CB 0.08 0.17 0.25 0.33 0.38 0.43 CCD 0.14 0.24 0.33 0.43 0.49 0.54 Equations taken from Urban Storm Drainage Criteria Manual, Volume 1, Chapter 5, Section 2.7, by the Urban Drainage and Flood Control District, Denver, Colorado Post-Project Condition, Basin O2 NRCS Soil Type D Surface Characteristics Streets: Paved Streets: Gravel Walks and Parking Roofs Lawns Clayey Soil Imperviousness Area (acres) 0 0.00 0.00 0.09 0.11 0.42 Percent Imperviousness 100 40 90 90 2 Total Area (acres) 0.20 Correction Factors KA and KCD for Use With Equations RO-6 and RO-7 NRCS Soil Type 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year C and D 0.000 0.068 0.135 0.214 0.263 0.298 A 0.000 0.057 0.112 0.161 0.188 0.216 Equations RO-6 and RO-7, Drainage Criteria Manual, Volume 1 CA 0.20 0.25 0.31 0.36 0.39 0.41 CB 0.24 0.31 0.37 0.43 0.47 0.50 CCD 0.29 0.36 0.42 0.50 0.55 0.59 S:\PROJECTS\LEG\DRNG\LEG-DevC.wpd Legacy Auto Final Development Plan (FDP) May 10, 2017 Page 3 of 3 Wohnrade Civil Engineers, Inc. Post-Project Condition, Basin O3 NRCS Soil Type D Surface Characteristics Streets: Paved Streets: Gravel Walks and Parking Roofs Lawns Clayey Soil Imperviousness Area (acres) 0 0.00 0.00 0.15 0.00 0.90 Percent Imperviousness 100 40 90 90 2 Total Area (acres) 0.15 Correction Factors KA and KCD for Use With Equations RO-6 and RO-7 NRCS Soil Type 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year C and D 0.000 0.020 0.048 0.078 0.103 0.109 A 0.000 0.018 0.044 0.069 0.082 0.095 Equations RO-6 and RO-7, Drainage Criteria Manual, Volume 1 CA 0.69 0.71 0.73 0.76 0.77 0.79 CB 0.71 0.73 0.75 0.78 0.80 0.81 CCD 0.73 0.75 0.77 0.80 0.83 0.83 Equations taken from Urban Storm Drainage Criteria Manual, Volume 1, Chapter 5, Section 2.7, by the Urban Drainage and Flood Control District, Denver, Colorado Post-Project Condition, Basins 1, O1 and O3 NRCS Soil Type D Surface Characteristics Streets: Paved Streets: Gravel Drives and Walks Roofs Lawns Clayey Soil Imperviousness Area (acres) 0.000 0.000 1.070 0.440 1.77 0.43 Percent Imperviousness 100 40 90 90 2 Total Area (acres) 3.28 Correction Factors KA and KCD for Use With Equations RO-6 and RO-7 NRCS Soil Type 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year C and D 0.000 0.067 0.133 0.211 0.260 0.294 A 0.000 0.056 0.110 0.159 0.186 0.214 Equations RO-6 and RO-7, Drainage Criteria Manual, Volume 1 CA 0.20 0.26 0.31 0.36 0.39 0.42 CB 0.25 0.31 0.37 0.43 0.47 0.50 CCD 0.29 0.36 0.43 0.50 0.55 0.59 S:\PROJECTS\LEG\DRNG\LEG-DevC.wpd Post-Project Conditions 2-Yr Runoff Computations City of Fort Collins, Colorado, Overland Flow, Time of Concentration: Ti= 0.395(1.1-C5)L1/2 / S1/3 Gutter/Swale Flow, Time of Concentration: Tt= L / 60V Tc= Ti + Tt Intensity, (i) taken from intensity formula for City of Fort Collins, i =29.97/(Tc+10.70)0.83 Calculations By: M. Wohnrade Velocity, (V) taken from Figure 3-1 Project: Legacy Auto FDP Rational Equation: Q= ciA Date: May 10, 2017 Design Point Basins Upstream Time of Concentration Tc Area, A (acres) Runoff Coefficient c Overland Flow Gutter/Pipe Flow Swale Flow Tc (min) Intensity,i (in/hr) Flow,Q C5 (cfs) Length,L (ft) Slope,S (ft/ft) Ti (min) Length,L (ft) Slope,S (%) Velocity,V (fps) Tt (min) Length,L (ft) Slope,S (%) Velocity,V (fps) Tt (min) 1 1 0.0 2.80 0.30 0.36 73.0 0.071 6.0 293.0 1.5 2.52 1.9 0.0 0.0 0.00 0.0 8.0 2.64 2.2 2 2 0.0 0.11 0.06 0.16 34.0 0.017 8.4 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 8.4 2.59 0.0 O1 O1 0.0 0.33 0.14 0.24 38.0 0.019 7.8 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 7.8 2.65 0.1 O2 O2 0.0 0.29 0.29 0.36 29.0 0.052 4.2 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 3.05 0.3 O3 O3 0.0 0.15 0.73 0.75 42.0 0.020 3.3 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 3.05 0.3 1 1,O1,O3 0.0 3.28 0.29 0.36 73.0 0.071 6.0 293.0 1.5 2.52 1.9 0.0 0.0 0.00 0.0 8.0 2.64 2.5 Note: S:\PROJECTS\LEG\DRNG\LEG-Developed_Runoff.wpd Page 1 of 3 Wohnrade Civil Engineers, Inc. Post-Project Conditions 10-Yr Runoff Computations City of Fort Collins, Colorado, Overland Flow, Time of Concentration: Ti= 0.395(1.1-C5)L1/2 / S1/3 Gutter/Swale Flow, Time of Concentration: Tt= L / 60V Tc= Ti + Tt Intensity, (i) taken from intensity formula for City of Fort Collins, i =65.29/(Tc+10.70)0.83 Calculations By: M. Wohnrade Velocity, (V) taken from Figure 3-1 Project: Legacy Auto FDP Rational Equation: Q= ciA Date: May 10, 2017 Design Point Basins Upstream Time of Concentration Tc Area, A (acres) Runoff Coefficient c Overland Flow Gutter/Pipe Flow Swale Flow Tc (min) Intensity,i (in/hr) Flow,Q C5 (cfs) Length,L (ft) Slope,S (ft/ft) Ti (min) Length,L (ft) Slope,S (%) Velocity,V (fps) Tt (min) Length,L (ft) Slope,S (%) Velocity,V (fps) Tt (min) 1 1 0.0 2.80 0.43 0.36 73.0 0.071 6.0 293.0 1.5 2.52 1.9 0.0 0.0 0.00 0.0 8.0 5.75 6.9 2 2 0.0 0.11 0.26 0.16 34.0 0.017 8.4 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 8.4 5.64 0.2 O1 O1 0.0 0.33 0.33 0.24 38.0 0.019 7.8 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 7.8 5.78 0.6 O2 O2 0.0 0.42 0.42 0.36 29.0 0.052 4.2 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 6.64 1.2 O3 O3 0.0 0.15 0.77 0.75 42.0 0.020 3.3 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 6.64 0.8 1 1,O1,O3 0.0 3.28 0.43 0.36 73.0 0.071 6.0 293.0 1.5 2.52 1.9 0.0 0.0 0.00 0.0 8.0 2.64 3.7 Note: S:\PROJECTS\LEG\DRNG\LEG-Developed_Runoff.wpd Page 2 of 3 Wohnrade Civil Engineers, Inc. Post-Project Conditions 100-Yr Runoff Computations City of Fort Collins, Colorado, Overland Flow, Time of Concentration: Ti= 0.395(1.1-C5)L1/2 / S1/3 Gutter/Swale Flow, Time of Concentration: Tt= L / 60V Tc= Ti + Tt Intensity, (i) taken from intensity formula for City of Fort Collins, i =110.46/(Tc+10.70)0.83 Calculations By: M. Wohnrade Velocity, (V) taken from Figure 3-1 Project: Legacy Auto FDP Rational Equation: Q= ciA Date: May 10, 2017 Design Point Basins Upstream Time of Concentration Tc Area, A (acres) Runoff Coefficient c Overland Flow Gutter/Pipe Flow Swale Flow Tc (min) Intensity,i (in/hr) Flow,Q C5 (cfs) Length,L (ft) Slope,S (ft/ft) Ti (min) Length,L (ft) Slope,S (%) Velocity,V (fps) Tt (min) Length,L (ft) Slope,S (%) Velocity,V (fps) Tt (min) 1 1 0.0 2.80 0.59 0.36 73.0 0.071 6.0 293.0 1.5 2.52 1.9 0.0 0.0 0.00 0.0 8.0 9.73 16.1 2 2 0.0 0.11 0.51 0.16 34.0 0.017 8.4 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 8.4 9.54 0.5 O1 O1 0.0 0.33 0.54 0.24 38.0 0.019 7.8 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 7.8 9.78 1.7 O2 O2 0.0 0.20 0.59 0.36 29.0 0.052 4.2 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 11.24 1.3 O3 O3 0.0 0.15 0.83 0.75 42.0 0.020 3.3 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 11.24 1.4 1 1,O1,O3 0.0 3.28 0.59 0.36 73.0 0.071 6.0 293.0 1.5 2.49 2.0 0.0 0.0 0.00 0.0 8.0 9.72 18.8 Note: S:\PROJECTS\LEG\DRNG\LEG-Developed_Runoff.wpd Page 3 of 3 Wohnrade Civil Engineers, Inc. 6-8 Urban Drainage and Flood Control District March 2017 Urban Storm Drainage Criteria Manual Volume 1 Table 6-3. Recommended percentage imperviousness values Land Use or Percentage Imperviousness Surface Characteristics (%) Business: Downtown Areas 95 Suburban Areas 75 Residential lots (lot area only): Single-family 2.5 acres or larger 12 0.75 – 2.5 acres 20 0.25 – 0.75 acres 30 0.25 acres or less 45 Apartments 75 Industrial: Light areas 80 Heavy areas 90 Parks, cemeteries 10 Playgrounds 25 Schools 55 Railroad yard areas 50 Undeveloped Areas: Historic flow analysis 2 Greenbelts, agricultural 2 Off-site flow analysis (when land use not defined) 45 Streets: Paved 100 Gravel (packed) 40 Drive and walks 90 Roofs 90 Lawns, sandy soil 2 Lawns, clayey soil 2 WOHNRADE CIVIL ENGINEERS, Hydraflow Rainfall Report Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v10.5 Saturday, 05 / 6 / 2017 Return Intensity-Duration-Frequency Equation Coefficients (FHA) Period (Yrs) B D E (N/A) 1 0.0000 0.0000 0.0000 -------- 2 29.9744 10.7000 0.8283 -------- 3 0.0000 0.0000 0.0000 -------- 5 50.0131 10.7000 0.8283 -------- 10 65.2885 10.7000 0.8283 -------- 25 82.5349 10.7000 0.8283 -------- 50 97.3175 10.7000 0.8283 -------- 100 110.4577 10.7000 0.8283 -------- File name: LEG.IDF Intensity = B / (Tc + D)^E Return Intensity Values (in/hr) Period (Yrs) 5 min 10 15 20 25 30 35 40 45 50 55 60 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2 3.06 2.44 2.04 1.76 1.55 1.39 1.26 1.16 1.07 1.00 0.94 0.88 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5 5.11 4.06 3.40 2.93 2.59 2.32 2.11 1.94 1.79 1.67 1.56 1.47 10 6.67 5.31 4.44 3.83 3.38 3.03 2.75 2.53 2.34 2.18 2.04 1.92 25 8.43 6.71 5.61 4.84 4.27 3.83 3.48 3.19 2.95 2.75 2.58 2.42 50 9.94 7.91 6.61 5.71 5.04 4.52 4.10 3.77 3.48 3.24 3.04 2.86 100 11.29 8.98 7.50 6.48 5.72 5.13 4.66 4.27 3.95 3.68 3.45 3.25 Tc = time in minutes. Values may exceed 60. Rainfall Precipitation Table (in) Precip. file name: S:\PROJECTS\CR16\DRNG\CR16-Civil 3D Hydroflow Rainfall Data.pcp Storm Distribution 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr SCS 24-hour 0.00 1.78 0.00 2.28 4.25 5.77 6.80 4.63 SCS 6-Hr 0.00 1.23 0.00 1.61 2.60 0.00 0.00 3.76 Huff-1st 0.00 0.00 0.00 0.00 4.00 5.38 6.50 0.00 Huff-2nd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff-3rd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff-4th 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff-Indy 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Custom 0.00 0.00 0.00 0.00 3.90 5.25 6.00 0.00 Hydrologic Soil Group—Larimer County Area, Colorado (Soil Mapping) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/29/2017 Page 1 of 4 4495660 4495680 4495700 4495720 4495740 4495760 4495780 4495800 4495820 4495660 4495680 4495700 4495720 4495740 4495760 4495780 4495800 4495820 493410 493430 493450 493470 493490 493510 493530 493410 493430 493450 493470 493490 493510 493530 40° 36' 47'' N 105° 4' 40'' W 40° 36' 47'' N 105° 4' 35'' W 40° 36' 41'' N 105° 4' 40'' W 40° 36' 41'' N 105° 4' 35'' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 40 80 160 240 Feet 0 10 20 40 60 Meters Map Scale: 1:835 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as Hydrologic Soil Group Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 22 Caruso clay loam, 0 to 1 percent slope D 1.8 63.5% 73 Nunn clay loam, 0 to 1 percent slopes C 1.1 36.5% Totals for Area of Interest 2.9 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Hydrologic Soil Group—Larimer County Area, Colorado Soil Mapping Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/29/2017 Page 3 of 4 Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado Soil Mapping Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/29/2017 Page 4 of 4 Appendix B Pond_1_Stage-Storage_Revised.txt Pond 1 Stage-Storage Rating Project: Legacy Auto FDP Basin Description: Pond 1 Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,981.40 3.22 N/A N/A 0.00 N/A 0.00 4,981.45 6.66 0.05 0.25 0.25 0.24 0.24 4,981.50 150.00 0.05 3.92 4.16 3.14 3.38 4,981.55 506.30 0.05 16.41 20.57 15.53 18.91 4,981.60 1,074.35 0.05 39.52 60.09 38.64 57.55 4,981.65 1,854.02 0.05 73.21 133.30 72.33 129.88 4,981.70 2,841.06 0.05 117.38 250.67 116.50 246.38 4,981.75 4,036.65 0.05 171.94 422.62 171.07 417.45 4,981.80 5,440.92 0.05 236.94 659.56 236.07 653.52 4,981.85 7,053.73 0.05 312.37 971.92 311.50 965.01 4,981.90 8,874.21 0.05 398.20 1370.12 397.33 1362.34 4,981.95 10,903.38 0.05 494.44 1864.56 493.57 1855.91 4,982.00 13,206.54 0.05 602.75 2467.31 601.83 2457.74 4,982.05 13,321.11 0.05 663.19 3130.50 663.19 3120.93 4,982.10 13,451.43 0.05 669.31 3799.81 669.31 3790.24 4,982.15 13,584.09 0.05 675.89 4475.70 675.89 4466.12 4,982.20 13,719.10 0.05 682.58 5158.28 682.58 5148.70 4,982.25 13,856.04 0.05 689.38 5847.66 689.38 5838.08 4,982.30 13,995.16 0.05 696.28 6543.94 696.28 6534.35 4,982.35 14,136.54 0.05 703.29 7247.23 703.29 7237.64 4,982.40 14,280.17 0.05 710.42 7957.65 710.41 7948.06 4,982.45 14,426.08 0.05 717.66 8675.30 717.65 8665.71 4,982.50 14,574.13 0.05 725.01 9400.31 725.00 9390.71 4,982.55 14,724.32 0.05 732.46 10132.77 732.46 10123.17 4,982.60 14,876.73 0.05 740.03 10872.80 740.02 10863.19 4,982.65 15,031.36 0.05 747.70 11620.50 747.70 11610.89 4,982.70 15,188.21 0.05 755.49 12375.99 755.49 12366.38 4,982.75 15,347.43 0.05 763.39 13139.38 763.39 13129.77 Page 1 Pond_1_Stage-Storage_Revised.txt 4,982.80 15,672.98 0.05 779.55 14690.33 779.54 14680.71 4,982.90 15,838.79 0.05 396.00 15086.33 266.26 14946.97 4,982.95 16,006.41 0.05 400.37 15486.70 272.96 15219.93 4,983.00 16,204.25 0.05 405.65 15892.35 280.31 15500.24 4,983.05 16,385.82 0.05 410.52 16302.87 286.31 15786.55 4,983.10 16,600.06 0.05 418.44 16721.31 304.15 16090.70 4,983.15 16,820.59 0.05 424.27 17145.58 309.35 16400.05 4,983.20 17,031.30 0.05 429.93 17575.51 314.64 16714.70 4,983.25 17,261.61 0.05 436.13 18011.64 326.43 17361.55 4,983.35 17,768.57 0.05 449.80 18904.00 333.08 17694.63 4,983.40 18,069.68 0.05 457.88 19361.88 340.36 18034.99 4,983.45 18,387.33 0.05 466.40 19828.28 347.98 18382.97 4,983.50 18,731.19 0.05 475.61 20303.89 356.13 18739.10 4,983.55 19,103.48 0.05 485.55 20789.44 364.82 19103.91 4,983.60 19,503.90 0.05 496.22 21285.66 374.04 19477.95 4,983.65 19,938.05 0.05 507.75 21793.41 383.90 19861.85 4,983.70 20,405.81 0.05 520.15 22313.56 394.40 20256.25 4,983.75 20,944.48 0.05 534.34 22847.91 406.20 20662.45 4,983.80 21,446.14 0.05 560.41 23955.94 428.21 21508.04 4,983.90 22,372.03 0.05 570.17 25098.44 382.13 22328.61 4,984.00 20,873.86 0.05 536.50 25634.94 415.96 22744.57 Page 2 Pond Report Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Saturday, 06 / 17 / 2017 Pond No. 1 - Pond 1 Pond Data Contours -User-defined contour areas. Average end area method used for volume calculation. Begining Elevation = 4982.00 ft Stage / Storage Table Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft) 0.00 4982.00 13,207 0 0 0.50 4982.50 14,574 6,945 6,945 1.00 4983.00 16,204 7,694 14,640 1.50 4983.50 18,731 8,734 23,373 2.00 4984.00 20,874 9,901 33,275 Culvert / Orifice Structures Weir Structures [A] [B] [C] [PrfRsr] [A] [B] [C] [D] Rise (in) = 4.00 0.00 0.00 0.00 Span (in) = 4.00 0.00 0.00 0.00 No. Barrels = 1 0 0 0 Invert El. (ft) = 4981.35 0.00 0.00 0.00 Length (ft) = 0.00 0.00 0.00 0.00 Slope (%) = 0.00 0.00 0.00 n/a N-Value = .013 .013 .013 n/a Orifice Coeff. = 0.60 0.60 0.60 0.60 Multi-Stage = n/a No No No Crest Len (ft) = 5.00 0.00 0.00 0.00 Crest El. (ft) = 4983.00 0.00 0.00 0.00 Weir Coeff. = 3.13 3.33 3.33 3.33 Weir Type = Broad --- --- --- Multi-Stage = No No No No Exfil.(in/hr) = 0.000 (by Wet area) TW Elev. (ft) = 0.00 Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s). Stage / Storage / Discharge Table Stage Storage Elevation Clv A Clv B Clv C PrfRsr Wr A Wr B Wr C Wr D Exfil User Total ft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs 0.00 0 4982.00 0.29 ic --- --- --- 0.00 --- --- --- --- --- 0.290 0.50 6,945 4982.50 0.41 ic --- --- --- 0.00 --- --- --- --- --- 0.414 1.00 14,640 4983.00 0.51 ic --- --- --- 0.00 --- --- --- --- --- 0.508 1.50 23,373 4983.50 0.59 ic --- --- --- 5.53 --- --- --- --- --- 6.121 2.00 33,275 4984.00 0.66 ic --- --- --- 15.65 --- --- --- --- --- 16.31 Hydrograph Report Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v10.5 Wednesday, 05 / 10 / 2017 Hyd. No. 1 Basins 1,O1 and O3 Hydrograph type = Rational Peak discharge = 18.90 cfs Storm frequency = 100 yrs Time to peak = 8 min Time interval = 1 min Hyd. volume = 12,109 cuft Drainage area = 3.280 ac Runoff coeff. = 0.59 Intensity = 9.765 in/hr Tc by User = 8.00 min IDF Curve = LEG.IDF Asc/Rec limb fact = 1/1.67 0 2 4 6 8 10 12 14 16 18 20 22 Q (cfs) 0.00 0.00 3.00 3.00 6.00 6.00 9.00 9.00 12.00 12.00 15.00 15.00 18.00 18.00 21.00 21.00 Q (cfs) Time (min) Basins 1,O1 and O3 Hyd. No. 1 -- 100 Year Hyd No. 1 Hydrograph Report Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Saturday, 06 / 17 / 2017 Hyd. No. 2 Pond 1 Routing Hydrograph type = Reservoir Peak discharge = 0.471 cfs Storm frequency = 100 yrs Time to peak = 0.35 hrs Time interval = 1 min Hyd. volume = 52,992 cuft Inflow hyd. No. = 1 - Basins 1,O1 and O3 Max. Elevation = 4982.79 ft Reservoir name = Pond 1 Max. Storage = 11,417 cuft Storage Indication method used. 0 5 10 15 20 25 30 35 40 45 50 Q (cfs) 0.00 0.00 3.00 3.00 6.00 6.00 9.00 9.00 12.00 12.00 15.00 15.00 18.00 18.00 21.00 21.00 Q (cfs) Time (hrs) Pond 1 Routing Hyd. No. 2 -- 100 Year Hyd No. 2 Hyd No. 1 Total storage used = 11,417 cuft WOHNRADE CIVIL ENGINEERS, Sheet 1 of 4 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia = 43.0 % B) Tributary Area's Imperviousness Ratio (i = Ia / 100 ) i = 0.430 C) Contributing Watershed Area Area = 3.280 ac D) For Watersheds Outside of the Denver Region, Depth of Average d6 = 0.43 in Runoff Producing Storm E) Design Concept (Select EURV when also designing for flood control) F) Design Volume (WQCV) Based on 40-hour Drain Time V DESIGN= 0.051 ac-ft (VDESIGN = (1.0 * (0.91 * i 3 - 1.19 * i 2 + 0.78 * i) / 12 * Area ) G) For Watersheds Outside of the Denver Region, V DESIGN OTHER= 0.051 ac-ft Water Quality Capture Volume (WQCV) Design Volume (VWQCV OTHER = (d 6*(VDESIGN /0.43)) H) User Input of Water Quality Capture Volume (WQCV) Design Volume V DESIGN USER= ac-ft (Only if a different WQCV Design Volume is desired) I) Predominant Watershed NRCS Soil Group WQCV selected. Soil group not required. J) Excess Urban Runoff Volume (EURV) Design Volume For HSG A: EURVA = 1.68 * i 1.28 EURV = ac-f t For HSG B: EURVB = 1.36 * i 1.08 For HSG C/D: EURVC/D = 1.20 * i 1.08 2. Basin Shape: Length to Width Ratio L : W = 2.0 : 1 (A basin length to width ratio of at least 2:1 will improve TSS reduction.) 3. Basin Side Slopes A) Basin Maximum Side Slopes Z = 4.00 ft / ft (Horizontal distance per unit vertical, 4:1 or flatter preferred) 4. Inlet Riprap A) Describe means of providing energy dissipation at concentrated inflow locations: Design Procedure Form: Extended Detention Basin (EDB) Legacy Auto Final Development Plan Wohnrade Civil Engineers, Inc. May 11, 2017 Fort Collins, Colorado Mary B. Wohnrade, P.E. Choose One Excess Urban Runoff Volume (EURV) Choose One A Sheet 2 of 4 Designer: Company: Date: Project: Location: 5. Forebay A) Minimum Forebay Volume V FMIN = 0.001 ac-ft (VFMIN = 1% of the WQCV) B) Actual Forebay Volume V F = ac-ft C) Forebay Depth (DF = 12 inch maximum) D F = in D) Forebay Discharge i) Undetained 100-year Peak Discharge Q 100 = cfs ii) Forebay Discharge Design Flow Q F = cfs (QF = 0.02 * Q 100) E) Forebay Discharge Design F) Discharge Pipe Size (minimum 8-inches) Calculated DP = in G) Rectangular Notch Width Calculated W N = in 6. Trickle Channel A) Type of Trickle Channel F) Slope of Trickle Channel S = 0.0044 ft / ft 7. Micropool and Outlet Structure A) Depth of Micropool (2.5-feet minimum) D M = 2.5 ft B) Surface Area of Micropool (10 ft 2 minimum) A M = 10 sq ft C) Outlet Type D) Smallest Dimension of Orifice Opening Based on Hydrograph Routing (Use UD-Detention) Dorifice = 0.44 inches E) Total Outlet Area Aot = 0.45 square inches (flow too small for berm w/ pipe) Legacy Auto Final Development Plan May 11, 2017 Wohnrade Civil Engineers, Inc. Design Procedure Form: Extended Detention Basin (EDB) Fort Collins, Colorado Mary B. Wohnrade, P.E. Choose One Wall with Rect. Notch Berm With Pipe Choose One Orifice Plate Other (Describe): Choose One Concrete Sheet 3 of 4 Designer: Company: Date: Project: Location: 8. Initial Surcharge Volume A) Depth of Initial Surcharge Volume D IS = 4 in (Minimum recommended depth is 4 inches) B) Minimum Initial Surcharge Volume VIS = cu ft (Minimum volume of 0.3% of the WQCV) C) Initial Surcharge Provided Above Micropool Vs = 3.3 cu ft 9. Trash Rack A) Water Quality Screen Open Area: At = A ot * 38.5*(e -0.095D ) A t = 17 square inches Other (Y/N): N C) Ratio of Total Open Area to Total Area (only for type 'Other') User Ratio = D) Total Water Quality Screen Area (based on screen type) A total = 28 sq. in. E) Depth of Design Volume (EURV or WQCV) H= 0.65 feet (Based on design concept chosen under 1E) F) Height of Water Quality Screen (HTR) H TR= 35.8 inches G) Width of Water Quality Screen Opening (Wopening) W opening = 12.0 inches (Minimum of 12 inches is recommended) Design Procedure Form: Extended Detention Basin (EDB) Mary B. Wohnrade, P.E. Wohnrade Civil Engineers, Inc. May 11, 2017 Legacy Auto Final Development Plan Fort Collins, Colorado B) Type of Screen (If specifying an alternative to the materials recommended S.S. Well Screen with 60% Open Area in the USDCM, indicate "other" and enter the ratio of the total open are to the total screen are for the material specified.) UD-BMP_v3.05.xlsm, EDB 5/11/2017, 11:33 AM Sheet 4 of 4 Designer: Company: Date: Project: Location: 10. Overflow Embankment A) Describe embankment protection for 100-year and greater overtopping: B) Slope of Overflow Embankment 4H:1V (Horizontal distance per unit vertical, 4:1 or flatter preferred) 11. Vegetation 12. Access A) Describe Sediment Removal Procedures Notes: Fort Collins, Colorado Wohnrade Civil Engineers, Inc. Mary B. Wohnrade, P.E. Legacy Auto Final Development Plan Riprap protection will be provided at the detention pond emergency overflow weir. Design Procedure Form: Extended Detention Basin (EDB) May 11, 2017 Choose One Irrigated Not Irrigated UD-BMP_v3.05.xlsm, EDB 5/11/2017, 11:33 AM Scale: Designed By: Reviewed By: Sheet 1"=20' MBW YSG 1 Project: Date: Sheets 11582 Colony Row Broomfield, Colorado 80021 Phone: (720)259-0965 Fax: (720)259-1519 No. Revisions: By: Date: WOHNRADE CIVIL ENGINEERS, INC. LEG: 1707.00 6/20/17 2 Scale: Designed By: Reviewed By: Sheet 1"=20' MBW YSG 2 Project: Date: Sheets 11582 Colony Row Broomfield, Colorado 80021 Phone: (720)259-0965 Fax: (720)259-1519 No. Revisions: By: Date: WOHNRADE CIVIL ENGINEERS, INC. LEG: 1707.00 6/20/17 2 Soft Bottom Wall with V-Notch Weir UD-BMP_v3.05.xlsm, EDB 5/11/2017, 11:33 AM B C / D Water Quality Capture Volume (WQCV) UD-BMP_v3.05.xlsm, EDB 5/11/2017, 11:33 AM of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 11, Sep 23, 2016 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Apr 22, 2011—Apr 28, 2011 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—Larimer County Area, Colorado (Soil Mapping) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/29/2017 Page 2 of 4