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Home My WebLink AboutTIMBERLINE - INTERNATIONAL - FDP210020 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORT Prepared for: Owner/Developer Mr. Devin Ferrey FR Holdings, Ltd. 125 S. Howes Street, 2nd Floor Fort Collins, Colorado 80521 Prepared by: 11582 Colony Row Broomfield, CO 80021 Phone: (720)259-0965, Fax: (720)259-1519 Project Number: 1805.00-TIM Drainage Design Considerations for the Timberline - International Final Development Plan (FDP) Fort Collins, Colorado September 27, 2021 September 27, 2021 Mr. Matt Simpson Stormwater Engineering City of Fort Collins 700 Wood Street Fort Collins, Colorado 80522 Subject: Drainage Design Considerations for the Timberline-International Final Development Plan (FDP) Fort Collins, Colorado Dear Mr. Simpson: Wohnrade Civil Engineers, Inc. (WCE) is pleased to resubmit this final hydrologic and hydraulic report for the subject project for your review. We have addressed staff comments contained in the document, Timberline-International, PDP200014, Round Number 3, dated May 21, 2021. This report complies with technical criteria set forth in the City of Fort Collins, Stormwater Criteria Manual, and Mile High Flood 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. Jon Rohrer – Staff Civil Designer Mary B. Wohnrade, P.E. - Principal Professional Engineer - (CO) Drainage Design Considerations for Timberline-International 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 .................................................................................................... 3 4.1 Proposed Project Description .......................................................................................................... 3 4.2 Post-Project Drainage Basins ........................................................................................................... 4 4.3 Post-Project Drainage Patterns ........................................................................................................ 4 4.4 Proposed Detention Pond ................................................................................................................ 4 5. DESIGN CRITERIA ......................................................................................................................... 6 5.1 Design References ............................................................................................................................ 6 5.2 Hydrologic Criteria ........................................................................................................................... 6 6. EROSION CONTROL ...................................................................................................................... 7 6.1 Low Impact Design (LID) .................................................................................................................. 7 6.2 Erosion Control Plan ........................................................................................................................ 7 6.3 Site Stabilization ............................................................................................................................... 8 7. CONCLUSIONS ................................................................................................................................ 8 7.1 Compliance with Standards ............................................................................................................. 8 7.2 Variances .......................................................................................................................................... 8 8. REFERENCES ................................................................................................................................... 8 Drainage Design Considerations for Timberline-International FDP TABLE OF CONTENTS, cont. Vicinity Map APPENDICES Appendix A: Post-Project Condition Hydrology Appendix B: Detention Pond Design Appendix C: LID Design Appendix D: Future Off-site Storm Sewer Preliminary Design DRAWINGS Sheet 1 of 1 Post-Project Drainage Plan Drainage Design Considerations for Timberline-International FDP Fort Collins, Colorado September 27, 2021 1. INTRODUCTION 1.1 Objective This study documents the results of a comprehensive hydrologic and hydraulic analysis for the proposed Timberline-International FDP project located in Fort Collins, Colorado. The project includes new 2,900 sf and 624 sf commercial buildings, new water and sewer services lines, site improvements, and an onsite stormwater detention pond (Photo 1). 1.2 Project History and Previous Studies There are no known hydrologic or hydraulic studies for the Timberline-International property. 1.3 Mapping and Surveying Intermill Land Surveying, of Loveland, Colorado, provided field survey information and topographic mapping of the project site, with a contour interval of 1-foot. The survey was performed in June 2018, and was referenced to NGS Monuments F136 and C402 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 Southwest ¼ of Section 8, Township 7 North, and Range 68 West of the 6th Principal Meridian, City of Fort Collins, Larimer County, Colorado. The site is bounded by N. Timberline Road on the east, International Boulevard on the south, Lake Canal on the west, and an existing commercial property on the north. The project is located outside of any FEMA regulated floodplain, as per the FEMA Flood Insurance Rate Map (FIRM), Community-Panel Number 08069C-0984H, effective on Photo 1 – Project Site Looking North Timberline-International FDP September 27, 2021 Page 2 May 2, 2012 (see Firmette). The property is also located adjacent to the Lake Canal, which is not a City of Fort Collins designated floodplain, as per the online mapping application FCMaps. 2.1 Site Description The project site is roughly 1.39 acres in size, and is located in a commercial area within Larimer County, Colorado. The property is currently being annexed into the City of Fort Collins, Colorado. The site is currently undeveloped and contains an existing ditch access road, a fill pile, and some existing utilities. The site is located in the Dry Creek Drainage Basin, as defined by the City of Fort Collins Master Drainage Plan. A future off-site storm sewer will be located parallel to the east property line, which begins at East Ridge Second Filing, and ends at the Dry Creek channel. No offsite stormwater runoff enters the site from the adjacent property located to the north. Stormwater runoff from South Timberline Road enters the property along the east property line. A geotechnical subsurface exploration report was prepared by CTL Thompson, and is dated October 1, 2018 (Reference 4). The subsurface materials encountered consist of 2 to 3 feet of sand and clay over sand and gravel. Groundwater was encountered in three borings at the time of drilling at a depth of roughly 13-feet, and was measured three days later at depths ranging from 11.5-feet to 12 feet. Bedrock was not encountered in any of the four borings within the property. The sand and gravel layer will facilitate a Partial Infiltration Section as it relates to bioretention. The USGS Web Soil Survey was also used to identify the hydrologic soils group within the project limits. The site consists entirely of Group B type soils, which exhibits a moderate infiltration rate. 3. PRE-PROJECT CONDITIONS 3.1 Pre-Project Drainage Basins The existing project site includes a single onsite drainage basin that includes the entire property for a total area of 1.39 acres. There is also a single off-site basin of 0.46 acres, which includes the west half of North Timberline Road. 3.2 Pre-Project Drainage Patterns Stormwater runoff from the entire property drains overland, across gravel and vegetated surfaces to Lake Canal, which bounds the property on the west and south. Timberline-International FDP September 27, 2021 Page 3 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 new 3,364 and 624 sf buildings, new asphalt parking and drives, new underground utilities, and a new onsite stormwater detention facility. The widening of N. Timberline Road to the west has also been accounted for in this drainage analysis. The widening will include a right turn lane for southbound traffic onto International Boulevard, and a northbound left-turn lane into the site. The street widening has been designed, and will be constructed as part of this development proposal. Stormwater runoff from the west half of Timberline Road will be conveyed along the west flowline of Timberline flowing north to south, and then continue west along the north flowline of International Boulevard. There are no proposed storm inlets in the adjacent streets as part of this future improvement. The preliminary design of a 30-inch diameter off-site storm sewer has also been included as part of this development proposal (See Appendix D). The off-site sewer would be located in the center of the existing right-turn lane in N. Timberline Road. A 390-foot long section of this sewer would be constructed as part of this development. Developed stormwater runoff will be discharged to Lake Canal at a rate not to exceed 0.20 cfs/acre. An agreement has been reached with Lake Canal Company, which allows for this release. Final engineering plans and the drainage report have been submitted to Lake Canal Company for review and comment. A written agreement for this stormwater release has been executed by Lake Canal Company, and is attached to this report. WCE also provided revised civil construction plans to Lake Canal Company on April 6, 2021 for their review and comment. The release rate and discharge location has not changed since the date of the executed agreement. Standard water quality treatment and Low Impact Development (LID) has also been incorporated into the stormwater design for this project, as per City of Fort Collins criteria. The primary LID measure includes a rain garden to treat stormwater runoff from 100% of the impervious surfaces. The proposed road improvements to N. Timberline Road and International Boulevard will necessitate the extension of the existing 6’H x 14’W RCB culvert in Lake Canal. The existing box culvert will be extended 20-feet to the northwest, and will require a new concrete headwall, wingwalls, and guardrail. Structural plans for the proposed extension have been prepared by Weeks & Associates of Fort Collins, Colorado, and will be submitted to Lake Canal Company for review and approval. Timberline-International FDP September 27, 2021 Page 4 4.2 Post-Project Drainage Basins The proposed project site has been divided into 3 post-project drainage basins for a total drainage area of 1.28 acres. Offsite Basin O1 (0.46 acres) extends from the existing centerline in N. Timberline Road, to the proposed back of walk on the west side of Timberline, and includes the ultimate widening of Timberline. Post-project drainage basins and patterns will generally mimic pre-project conditions, with Basin 1 draining in the direction of Lake Canal directly to a detention facility and Basin 2 draining to a bioretention area that overflows into the detention facility. The detention facility will release developed runoff to Lake Canal at a rate not to exceed 0.20 cfs/acre, as per the Dry Creek Basin Master Drainage Plan. 4.3 Post-Project Drainage Patterns Basin 1 (0.28 ac) drains overland across vegetated areas, at slopes ranging from 2.0% to 25%, to the new detention facility, and includes 100% pervious surfaces. The drainage pattern within this basin will generally mimic pre-project drainage patterns. The 10 and 100-year peak discharges are estimated to be 0.3 cfs and 0.8 cfs respectively. Basin 2 (0.71 ac) drains overland across vegetated areas, and in vertical curb and gutter, at slopes ranging from 1.67% to 25%, to the new bioretention area. Basin 2 includes 100% of the project impervious surfaces. The drainage pattern within this basin mimics pre-project drainage patterns. The 10 and 100-year peak discharges are estimated to be 2.4 cfs and 6.1 cfs respectively. Basin 3 (0.29 ac) drains overland across the new ditch access road (gravel surface), and existing vegetated areas at slopes ranging from 1.55% to 4.0%, towards Lake Canal. The drainage pattern within this basin mimics pre-project drainage patterns. The 10 and 100-year peak discharges are estimated to be 0.5 cfs and 1.2 cfs respectively. Offsite Basin O1 (0.46 ac) drains overland across the pavement on Timberline Road to the proposed vertical curb and gutter on the west side of the southbound lane. The 10 and 100-year peak discharges are estimated to be 1.9 cfs and 4.6 cfs respectively. Calculations made as part of this investigation, along with other supporting material, are contained in Appendix A. 4.4 Proposed Detention Pond The proposed detention pond is located in the southeast portion of the property, adjacent to Lake Canal. The pond will detain stormwater runoff from onsite Basins 1 and 2. Stormwater runoff from Basin 2 will be first be routed through the bioretention area to meet LID requirements. Timberline-International FDP September 27, 2021 Page 5 The pond has been designed to accommodate the 100-yr flood control volume. The standard City of Fort Collins Water Quality Outlet Structure will be used to control the 100-year stormwater release. 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 Basins 1 and 2 (0.99 acres) will be released at this rate. Stormwater runoff from Basin 3 cannot be captured and routed to an onsite facility, and will therefore drain directly to Lake Canal. The maximum allowable release from the developed site is 0.20 cfs/ac x 0.99 acres= 0.20 cfs. As per Colorado Revised Statutes 37-92-602(8), criteria regarding detention drain time will apply to this project. The spreadsheet (SDI_Design_Data_v1.08.xlsm) developed by the UDFCD and State of Colorado Division of Water Resources has been used to verify the 5 and 100-year drain times. The maximum time to drain 97% of all runoff, from a rainfall event that is less than or equal to a 5-year storm, is within 72 hours after the end on the event. The estimated drain time for Pond 1 is 4.6 hours, which is much less than the required maximum. The maximum time to drain 99% of all runoff, for events greater than the 5-year storm, is within 120 hours after the end of the event. The estimated drain time for Pond 1 for storms greater than the 5-year event is 12.8 hours, which is much less than the maximum. The completed SDI_Design_Data spreadsheet has been provided in Appendix B of this report. The computer program, Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2016 was used to route the 100-year design storm through the detention pond. The Storage Indication Method was used to route the 100-yr design storm through the proposed detention pond. An inflow hydrograph was developed to route the 100-year storm through the detention pond, which includes Basins 1 and 2 (0.99 acres). Results of the pond routing predict a maximum 100-yr water surface elevation of 4935.91, with an associated storage requirement of 2,682 cu-ft. A 2.25” diameter orifice will control the release of developed stormwater runoff at a maximum rate of 0.18 cfs. The 100-year storm was routed through the pond, beginning at an elevation of 4934.00. An emergency pond overflow weir has also been designed to pass the 100-year peak inflow (7.1 cfs) to the pond. The notch elevation of the weir will be set at 4937.50, and the top at an elevation of 4938.00, and will be 10’ in width. The weir will direct stormwater runoff to the historic discharge location, which is the Lake Canal. Bioretention has also been incorporated into the Low Impact Development design. The computer programs UD-BMP (v3.07), developed by the Mile High Flood District (MHFD), has been used to calculate the required orifice size based on a 12-hour drain time. Stormwater runoff from all proposed impervious areas (Basin 2) will be routed through Timberline-International FDP September 27, 2021 Page 6 a bioretention area for treatment. Calculations have been determined for this area, based on fully developed conditions. Based on the Rain Garden (RG) design procedure in the UD-BMP spreadsheet, the calculated design volume for the bioretention area is 462 cu-ft, and includes runoff from onsite Basin 2. The total volume provided in the bioretention area from elevation 4936.5 to 4937.0 is 2,033 cu-ft. Calculations made as part of this pond analysis, along with other supporting material, are contained in Appendix C. 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 Mile High Flood 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. 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 referenced in Table 3.4-1 of the City of Fort Collins Stormwater Criteria Manual (Reference 1). Runoff coefficients were derived using the equations described in Chapter 5, Section 3.2 of the Fort Collins Stormwater Criteria Manual. The area of all impervious surfaces was determined for each drainage basin, including roads, walk, and roofs. It is a much more laborious effort but provides a more realistic estimate of peak discharge from the developed site. Site specific rainfall data from the NOAA Precipitation Server is normally used on all WCE projects, but will not be used on this project, as requested by the City. We believe that using the site-specific rainfall data and determining the area of impervious surfaces for each drainage basin results in the most accurate representation of peak discharge from both the historic and developed sites. Using the City runoff coefficients and citywide rainfall data generally results in lower overall peak discharges, and won’t be as conservative as site specific data. Timberline-International FDP September 27, 2021 Page 7 6. EROSION CONTROL 6.1 Low Impact Design (LID) The proposed project has incorporated the 4-step process developed by the Mile High Flood District (MHFD), for the protection of receiving waters downstream of the project site. The BMP Selection Tool within the UD-BMP spreadsheet has been used to select the appropriate BMPs for Steps 1 and 2 of the 4-step processes. The project implements volume reduction strategies including grass swales, and BMPs including Bioretention – Partial Infiltration Basins. Low Impact Development (LID) is a comprehensive land planning and engineering design approach to managing stormwater runoff with a goal of replicating the pre-development hydrologic regime of urban and developing watersheds. Volume 3 of the UDFCD Drainage Criteria Manual emphasizes LID criteria, including Minimizing Directly Connected Impervious Areas (MDCIA) as the first step in stormwater quality planning and has provided guidance on LID techniques such as grass swales, grass buffers, permeable pavement systems, bioretention, and pollution prevention (pollutant source controls). Low Impact Development (LID) design will be required for this project using methods and techniques described in Volume 3, Chapter 1, Section 4.1, Runoff Reduction Practices. The opportunity to implementation multiple LID techniques is limited, due to the size of the site (1.39 acres). Surface runoff from impervious areas drains to the bioretention area. The length and depth of grass buffers and grass swales is employed to some extent, but is limited. The project has also been designed to minimize impacts to the site, and conserve existing amenities. One example of this would be minimizing the disturbance in drainage Basin 3 along the east side of Lake Canal, and retaining the existing vegetation. With the exception of a small portion of the drive entrance, nearly 100% of all newly added or modified impervious area will be treated by LID techniques, which complies with criteria set forth in the City of Fort Collins Stormwater Criteria Manual, Chapter 7, Section 6.0, Low Impact Development. The technique to be employed will include a bioretention area (rain garden), which will be located adjacent to the stormwater detention pond. The clayey sand, and sand and gravel layer will facilitate a Partial Infiltration Section as it relates to bioretention. A perforated underdrain will be installed beneath the bioretention area in order to hydraulically connect the area to the detention pond. Calculations made as part of this LID analysis, along with other supporting material, are contained in Appendix C. 6.2 Erosion Control Plan A proposed rainfall erosion control plan during construction will consist of temporary Timberline-International FDP September 27, 2021 Page 8 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. Wohnrade Civil Engineers, Inc. will prepare 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 will also be 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 will be included in the written SWMP report. 6.3 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. 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, Mile High Flood District, Denver, Colorado, Revised April 2008. 3. CDOT Drainage Design Manual, Colorado Department of Transportation. 4. Geotechnical Investigation, Proposed Commercial Development, Lot 1, Industrial Business Park, CTL Thompson, Inc., October 1, 2018. Project Location 125 S. Howes Street 2nd Floor Fort Collins, CO 80521 Justin Green Lake Canal Sent via email: justin@lakecanal.com RE: Requested Storm Water Outfall into Lake Canal Mr. Green; FR Holdings, Ltd. is the owner of Lot 1 in the Industrial Business Park PUD in Fort Collins, a 1.39 acre parcel that borders Lake Canal at the north west intersection of Timberline Road and International Boulevard. We are pursuing a small mixed-‐use commercial development on our property. In our initial conversations with the City of Fort Collins, we were asked to construct and pay for a comprehensive master-‐planned storm drainage system along Timberline Road which would run not only along our eastern frontage, but further south several hundred yards, well beyond our property boundary. This request is obviously cost prohibitive. As an alternative, City staff proposed a storm water outfall agreement with Lake Canal. Staff mentioned that other projects in the area have made similar arrangements with Lake Canal. Enclosed is a preliminary design for our project including an outfall structure into the canal as well as a flow calculation from our site based on a 100-‐year event. We are requesting approval from Lake Canal for this discharge, and understand there will be an annual fee associated with the same. Please contact me directly with any questions. Thank you, Devin Ferrey President, FR Holdings, Ltd. devin@fr-‐corp.com 970-‐691-‐1234 Appendix A Timberline-International Preliminary Development Plan April 6, 2021 Runoff Coefficient Calculations Post-Project Condition, Basin 1 NRCS Soil Type B Surface Type Asphalt Gravel Concrete Rooftop Lawns, Clayey Soil, Avg Slope Composite Runoff Coefficient Area (acres)0.000 0.000 0.003 0.000 0.277 0.26 Runoff Coefficients 0.95 0.5 0.95 0.95 0.25 Total Area (acres)0.28 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 0.26 0.26 0.26 0.28 0.31 0.32 Post-Project Condition, Basin 2 (Rain Garden Inflow) NRCS Soil Type B Surface Type Asphalt Gravel Concrete Rooftop Lawns, Clayey Soil, Avg Slope Composite Runoff Coefficient Area (acres)0.269 0.000 0.098 0.087 0.256 0.70 Runoff Coefficients 0.95 0.5 0.95 0.95 0.25 Total Area (acres)0.71 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 0.70 0.70 0.70 0.77 0.84 0.87 Storm Return Period Runoff coefficient equations taken from Table 3.2-2 of the Fort Collins Stormwater Criteria Manual, Chapter 5, Section 3.2 Runoff coefficient equations taken from Table 3.2-2 of the Fort Collins Stormwater Criteria Manual, Chapter 5, Section 3.2 Storm Return Period Page 1 of 3 Timberline-International Preliminary Development Plan April 6, 2021 Runoff Coefficient Calculations Post-Project Condition, Basin 3 NRCS Soil Type B Surface Type Asphalt Gravel Concrete Rooftop Lawns, Clayey Soil, Avg Slope Composite Runoff Coefficient Area (acres)0.000 0.090 0.000 0.000 0.200 0.33 Runoff Coefficients 0.95 0.5 0.95 0.95 0.25 Total Area (acres)0.29 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 0.33 0.33 0.33 0.36 0.39 0.41 Post-Project Condition, Basin O1 NRCS Soil Type B Surface Type Asphalt Gravel Concrete Rooftop Lawns, Clayey Soil, Avg Slope Composite Runoff Coefficient Area (acres)0.367 0.000 0.038 0.000 0.055 0.87 Runoff Coefficients 0.95 0.5 0.95 0.95 0.25 Total Area (acres)0.46 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 0.87 0.87 0.87 0.95 1.00 1.00 Runoff coefficient equations taken from Table 3.2-2 of the Fort Collins Stormwater Criteria Manual, Chapter 5, Section 3.2 Runoff coefficient equations taken from Table 3.2-2 of the Fort Collins Stormwater Criteria Manual, Chapter 5, Section 3.2 Storm Return Period Storm Return Period Page 2 of 3 Timberline-International Preliminary Development Plan April 6, 2021 Runoff Coefficient Calculations Post-Project Condition, Basins 1 & 2 (Detention Pond Inflow) NRCS Soil Type B Surface Type Asphalt Gravel Concrete Rooftop Lawns, Clayey Soil, Avg Slope Composite Runoff Coefficient Area (acres)0.269 0.000 0.101 0.087 0.533 0.57 Runoff Coefficients 0.95 0.5 0.95 0.95 0.25 Total Area (acres)0.99 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 0.57 0.57 0.57 0.63 0.69 0.72 Runoff coefficient equations taken from Table 3.2-2 of the Fort Collins Stormwater Criteria Manual, Chapter 5, Section 3.2 Storm Return Period Page 3 of 3 City of Fort Collins, Colorado, Overland Flow, Time of Concentration: Ti= 1.87(1.1-CxCf)L1/2 / S1/3 Gutter/Swale Flow, Time of Concentration: Tt= L / 60V Tc= Ti + Tt Intensity, (i) taken from intensity formula for Timberline-International PDP, i =30.04/(Tc+11.30)0.84 Calculations by: M. Wohnrade Velocity, (V) taken from Figure 3-1 Project: Timberline-International PDP Rational Equation: Q = ciA Date: April 6, 2021 C5 Length, L (ft) Slope, S (%) 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 0.28 0.26 0.26 33.8 2.7 6.6 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 7.3 2.55 0.2 2 2 0.0 0.71 0.70 0.70 22.3 2.4 2.6 0.0 0.0 0.00 0.0 186.4 1.9 2.22 1.4 5.0 2.85 1.4 3 3 0.0 0.29 0.33 0.33 25.0 3.2 4.9 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 2.85 0.3 O1 O1 0.0 0.46 0.87 0.87 52.3 5.0 1.8 233.3 0.4 1.29 3.0 0.0 0.0 0.00 0.0 5.0 2.85 1.1 1 1,2 0.0 0.99 0.57 0.57 33.8 2.7 4.1 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 5.0 2.85 1.6 Post-Project Conditions 2-Yr Runoff Computations Design Point Basins Upstream Time of Concentration Tc Area, A (acres) Runoff Coefficient c Overland Flow Gutter/Pipe Flow Swale Flow Note: Tc (min) Intensity, i (in/hr) Flow, Q (cfs) Rainfall intensity values were generated using Table 3.4-1 of the Fort Collins Stormwater Criteria Manual TIM-DevQ.xlsx Page 1 of 3 City of Fort Collins, Colorado, Overland Flow, Time of Concentration: Ti= 1.87(1.1-CxCf)L1/2 / S1/3 Gutter/Swale Flow, Time of Concentration: Tt= L / 60V Tc= Ti + Tt Intensity, (i) taken from intensity formula for Timberline-International PDP, i =46.95/(Tc+10.60)0.83 Calculations by: M. Wohnrade Velocity, (V) taken from Figure 3-1 Project: Timberline-International PDP Rational Equation: Q = ciA Date: April 6, 2021 C5 Length, L (ft) Slope, S (%) 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 0.28 0.26 0.26 33.8 2.7 6.6 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 7.3 4.35 0.3 2 2 0.0 0.71 0.70 0.70 22.3 2.4 2.6 0.0 0.0 0.00 0.0 186.4 1.9 2.22 1.4 5.0 4.87 2.4 3 3 0.0 0.29 0.33 0.33 25.0 3.2 4.9 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 4.87 0.5 O1 O1 0.0 0.46 0.87 0.87 52.3 5.0 1.8 233.3 0.4 1.29 3.0 0.0 0.0 0.00 0.0 5.0 4.87 1.9 1 1,2 0.0 0.99 0.57 0.57 33.8 2.7 4.1 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 5.0 4.87 2.7 Rainfall intensity values were generated using Table 3.4-1 of the Fort Collins Stormwater Criteria Manual Note: Post-Project Conditions 10-Yr Runoff Computations 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 (cfs) TIM-DevQ.xlsx Page 2 of 3 Wohnrade Civil Engineers, Inc. City of Fort Collins, Colorado, Overland Flow, Time of Concentration: Ti= 1.87(1.1-CxCf)L1/2 / S1/3 Gutter/Swale Flow, Time of Concentration: Tt= L / 60V Tc= Ti + Tt Intensity, (i) taken from intensity formula for Timberline-International PDP, i =98.31/(Tc+10.80)0.83 Calculations by: M. Wohnrade Velocity, (V) taken from Figure 3-1 Project: Timberline-International PDP Rational Equation: Q = ciA Date: April 6, 2021 C5 Length, L (ft) Slope, S (%) 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 0.28 0.32 0.26 33.8 2.7 6.1 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 6.8 9.09 0.8 2 2 0.0 0.71 0.87 0.70 22.3 2.4 1.5 0.0 0.0 0.00 0.0 186.4 1.9 2.22 1.4 5.0 9.94 6.1 3 3 0.0 0.29 0.41 0.33 25.0 3.2 4.4 0.0 0.0 0.00 0.0 0.0 0.0 0.00 0.0 5.0 9.94 1.2 O1 O1 0.0 0.46 1.00 0.87 52.3 5.0 0.8 233.3 0.4 1.29 3.0 0.0 0.0 0.00 0.0 5.0 9.94 4.6 1 1,2 0.0 0.99 0.72 0.57 33.8 2.7 3.0 0.0 0.0 0.00 0.0 147.0 4.8 3.53 0.7 5.0 9.94 7.1 Rainfall intensity values were generated using Table 3.4-1 of the Fort Collins Stormwater Criteria Manual Note: Post-Project Conditions 100-Yr Runoff Computations 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 (cfs) TIM-DevQ.xlsx Page 3 of 3 Wohnrade Civil Engineers, Inc. WOHNRADE CIVIL ENGINEERS, INC. FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 8 Table 3.4-1. IDF Table for Rational Method Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) 5 2.85 4.87 9.95 39 1.09 1.86 3.8 6 2.67 4.56 9.31 40 1.07 1.83 3.74 7 2.52 4.31 8.80 41 1.05 1.80 3.68 8 2.40 4.10 8.38 42 1.04 1.77 3.62 9 2.30 3.93 8.03 43 1.02 1.74 3.56 10 2.21 3.78 7.72 44 1.01 1.72 3.51 11 2.13 3.63 7.42 45 0.99 1.69 3.46 12 2.05 3.50 7.16 46 0.98 1.67 3.41 13 1.98 3.39 6.92 47 0.96 1.64 3.36 14 1.92 3.29 6.71 48 0.95 1.62 3.31 15 1.87 3.19 6.52 49 0.94 1.6 3.27 16 1.81 3.08 6.30 50 0.92 1.58 3.23 17 1.75 2.99 6.10 51 0.91 1.56 3.18 18 1.70 2.90 5.92 52 0.9 1.54 3.14 19 1.65 2.82 5.75 53 0.89 1.52 3.10 20 1.61 2.74 5.60 54 0.88 1.50 3.07 21 1.56 2.67 5.46 55 0.87 1.48 3.03 22 1.53 2.61 5.32 56 0.86 1.47 2.99 23 1.49 2.55 5.20 57 0.85 1.45 2.96 24 1.46 2.49 5.09 58 0.84 1.43 2.92 25 1.43 2.44 4.98 59 0.83 1.42 2.89 26 1.4 2.39 4.87 60 0.82 1.4 2.86 27 1.37 2.34 4.78 65 0.78 1.32 2.71 28 1.34 2.29 4.69 70 0.73 1.25 2.59 29 1.32 2.25 4.60 75 0.70 1.19 2.48 30 1.30 2.21 4.52 80 0.66 1.14 2.38 31 1.27 2.16 4.42 85 0.64 1.09 2.29 32 1.24 2.12 4.33 90 0.61 1.05 2.21 33 1.22 2.08 4.24 95 0.58 1.01 2.13 34 1.19 2.04 4.16 100 0.56 0.97 2.06 35 1.17 2.00 4.08 105 0.54 0.94 2.00 36 1.15 1.96 4.01 110 0.52 0.91 1.94 37 1.16 1.93 3.93 115 0.51 0.88 1.88 38 1.11 1.89 3.87 120 0.49 0.86 1.84 FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.2 Runoff Coefficients Page 5 Table 3.2-2. Surface Type - Runoff Coefficients Surface Type Runoff Coefficients Hardscape or Hard Surface Asphalt, Concrete 0.95 Rooftop 0.95 Recycled Asphalt 0.80 Gravel 0.50 Pavers 0.50 Landscape or Pervious Surface Lawns, Sandy Soil, Flat Slope < 2% 0.10 Lawns, Sandy Soil, Avg Slope 2-7% 0.15 Lawns, Sandy Soil, Steep Slope >7% 0.20 Lawns, Clayey Soil, Flat Slope < 2% 0.20 Lawns, Clayey Soil, Avg Slope 2-7% 0.25 Lawns, Clayey Soil, Steep Slope >7% 0.35 3.2.1 Composite Runoff Coefficients Drainage sub-basins are frequently composed of land that has multiple surface types or zoning classifications. In such cases a composite runoff coefficient must be calculated for any given drainage sub-basin. The composite runoff coefficient is obtained using the following formula: t n i ii A xAC C 1 Equation 5-2 Where: C = Composite Runoff Coefficient Ci = Runoff Coefficient for Specific Area (Ai), dimensionless Ai = Area of Surface with Runoff Coefficient of Ci, acres or square feet n = Number of different surfaces to be considered At = Total Area over which C is applicable, acres or square feet 3.2.2 Runoff Coefficient Frequency Adjustment Factor The runoff coefficients provided in Table 3.2-1 and Table 3.2-2 are appropriate for use with the 2-year storm event. For any analysis of storms with higher intensities, an adjustment of the runoff coefficient is required due to the lessening amount of infiltration, depression retention, evapotranspiration and other losses that have a proportionally smaller effect on high-intensity storm runoff. This adjustment is 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 Hydraflow Rainfall Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020 Wednesday, 03 / 24 / 2021 Return Intensity-Duration-Frequency Equation Coefficients (FHA) Period (Yrs)B D E (N/A) 1 0.0000 0.0000 0.0000 -------- 2 30.0397 11.3000 0.8439 -------- 3 0.0000 0.0000 0.0000 -------- 5 0.0000 0.0000 0.0000 -------- 10 46.9523 10.6000 0.8251 -------- 25 0.0000 0.0000 0.0000 -------- 50 0.0000 0.0000 0.0000 -------- 100 98.3129 10.8000 0.8304 -------- File name: TIM.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 2.85 2.27 1.90 1.64 1.45 1.30 1.18 1.08 1.00 0.93 0.87 0.82 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 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 10 4.87 3.87 3.23 2.79 2.46 2.21 2.01 1.84 1.70 1.59 1.49 1.40 25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100 9.94 7.91 6.61 5.71 5.04 4.52 4.11 3.77 3.49 3.25 3.04 2.86 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 FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 9 Figure 3.4-1. Rainfall IDF Curve – Fort Collins Appendix B Project: Basin ID: Depth Increment = ft Required Volume Calculation Top of Micropool -- 0.00 -- -- -- 0 0.000 Selected BMP Type =EDB -- 0.50 -- -- -- 484 0.011 116 0.003 Watershed Area = 0.99 acres Note: L / W Ratio < 1 -- 1.00 -- -- -- 1,814 0.042 677 0.016 Watershed Length = 181 ft L / W Ratio = 0.8 -- 1.50 -- -- -- 2,280 0.052 1,696 0.039 Watershed Slope = 0.044 ft/ft -- 2.00 -- -- -- 2,844 0.065 2,972 0.068 Watershed Imperviousness = 57.00% percent -- 2.50 -- -- -- 5,449 0.125 5,073 0.116 Percentage Hydrologic Soil Group A = 0.0% percent -- 3.00 -- -- -- 6,751 0.155 8,123 0.186 Percentage Hydrologic Soil Group B = 100.0% percent -- 3.50 -- -- -- 8,231 0.189 11,869 0.272 Percentage Hydrologic Soil Groups C/D = 0.0% percent -- 4.00 -- -- -- 9,752 0.224 16,364 0.376 Desired WQCV Drain Time = 40.0 hours -- -- -- -- Location for 1-hr Rainfall Depths = Denver - Capitol Building -- -- -- -- Water Quality Capture Volume (WQCV) = 0.019 acre-feet -- -- -- -- Excess Urban Runoff Volume (EURV) = 0.061 acre-feet -- -- -- -- 2-yr Runoff Volume (P1 = 0.87 in.) = 0.036 acre-feet 0.87 inches -- -- -- -- 5-yr Runoff Volume (P1 = 1.15 in.) = 0.052 acre-feet 1.15 inches -- -- -- -- 10-yr Runoff Volume (P1 = 1.45 in.) = 0.073 acre-feet 1.45 inches -- -- -- -- 25-yr Runoff Volume (P1 = 1.96 in.) = 0.116 acre-feet 1.96 inches -- -- -- -- 50-yr Runoff Volume (P1 = 2.43 in.) = 0.151 acre-feet 2.43 inches -- -- -- -- 100-yr Runoff Volume (P1 = 2.97 in.) = 0.198 acre-feet 2.97 inches -- -- -- -- 500-yr Runoff Volume (P1 = 4.5 in.) = 0.323 acre-feet 4.50 inches -- -- -- -- Approximate 2-yr Detention Volume = 0.034 acre-feet -- -- -- -- Approximate 5-yr Detention Volume = 0.048 acre-feet -- -- -- -- Approximate 10-yr Detention Volume = 0.068 acre-feet -- -- -- -- Approximate 25-yr Detention Volume = 0.087 acre-feet -- -- -- -- Approximate 50-yr Detention Volume = 0.100 acre-feet -- -- -- -- Approximate 100-yr Detention Volume = 0.120 acre-feet -- -- -- -- -- -- -- -- Stage-Storage Calculation -- -- -- -- Zone 1 Volume (100-year) = 0.120 acre-feet -- -- -- -- Select Zone 2 Storage Volume (Optional) =acre-feet -- -- -- -- Select Zone 3 Storage Volume (Optional) =acre-feet -- -- -- -- Total Detention Basin Volume = 0.120 acre-feet -- -- -- -- Initial Surcharge Volume (ISV) = user ft^3 -- -- -- -- Initial Surcharge Depth (ISD) = user ft -- -- -- -- Total Available Detention Depth (Htotal) =user ft -- -- -- -- Depth of Trickle Channel (HTC) = user ft -- -- -- -- Slope of Trickle Channel (STC) =user ft/ft -- -- -- -- Slopes of Main Basin Sides (Smain) =user H:V -- -- -- -- Basin Length-to-Width Ratio (RL/W) =user -- -- -- -- -- -- -- -- Initial Surcharge Area (AISV) =user ft^2 -- -- -- -- Surcharge Volume Length (LISV) =user ft -- -- -- -- Surcharge Volume Width (WISV) =user ft -- -- -- -- Depth of Basin Floor (HFLOOR) =user ft -- -- -- -- Length of Basin Floor (LFLOOR) =user ft -- -- -- -- Width of Basin Floor (WFLOOR) =user ft -- -- -- -- Area of Basin Floor (AFLOOR) =user ft^2 -- -- -- -- Volume of Basin Floor (VFLOOR) =user ft^3 -- -- -- -- Depth of Main Basin (HMAIN) =user ft -- -- -- -- Length of Main Basin (LMAIN) =user ft -- -- -- -- Width of Main Basin (WMAIN) =user ft -- -- -- -- Area of Main Basin (AMAIN) =user ft^2 -- -- -- -- Volume of Main Basin (VMAIN) =user ft^3 -- -- -- -- Calculated Total Basin Volume (Vtotal) =user acre-feet -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- DETENTION BASIN STAGE-STORAGE TABLE BUILDER Optional Override Area (ft^2) Length (ft) Optional Override Stage (ft) Stage (ft) Stage - Storage Description Area (ft^2) Width (ft) 142 Timberline Detention Pond 1 - Includes Basins 1 and 2 UD-Detention, Version 3.07 (February 2017) Volume (ft^3) Volume (ac-ft) Area (acre) Optional User Override 1-hr Precipitation WQCV not provided! Example Zone Configuration (Retention Pond) UD-Detention_v3.07.xlsm, Basin 4/21/2021, 1:07 PM 1 User Defined Stage-Area Boolean for Message 1 Equal Stage-Area Inputs 1 Watershed L:W 1 CountA 0 Calc_S_TC H_FLOOR L_FLOOR_OTHER 0.00 ISV 0.00 ISV 0.00 Floor 0.00 Floor 2.54 Zone 1 (100-year)2.54 Zone 1 (100-year) 0.00 Zone 2 0.00 Zone 2 0.00 Zone 3 0.00 Zone 3 DETENTION BASIN STAGE-STORAGE TABLE BUILDER UD-Detention, Version 3.07 (February 2017) 0.000 0.095 0.190 0.285 0.380 0.000 0.060 0.120 0.180 0.240 0.00 1.00 2.00 3.00 4.00 Volume (ac-ft)Area (acres)Stage (ft.) Area (acres)Volume (ac-ft) 0 100 200 300 400 0 5 10 15 20 0.00 1.00 2.00 3.00 4.00 Area (sq.ft.)Length, Width (ft.)Stage (ft) Length (ft)Width (ft)Area (sq.ft.) UD-Detention_v3.07.xlsm, Basin 4/21/2021, 1:07 PM Project: Basin ID: Stage (ft)Zone Volume (ac-ft)Outlet Type Zone 1 (100-year)2.54 0.120 Circular Orifice Zone 2 Zone 3 0.120 Total User Input: Orifice at Underdrain Outlet (typically used to drain WQCV in a Filtration BMP) Calculated Parameters for Underdrain Underdrain Orifice Invert Depth = N/A ft (distance below the filtration media surface) Underdrain Orifice Area = N/A ft2 Underdrain Orifice Diameter = N/A inches Underdrain Orifice Centroid = N/A feet User Input: Orifice Plate with one or more orifices or Elliptical Slot Weir (typically used to drain WQCV and/or EURV in a sedimentation BMP) Calculated Parameters for Plate Invert of Lowest Orifice = N/A ft (relative to basin bottom at Stage = 0 ft) WQ Orifice Area per Row = N/A ft2 Depth at top of Zone using Orifice Plate = N/A ft (relative to basin bottom at Stage = 0 ft) Elliptical Half-Width = N/A feet Orifice Plate: Orifice Vertical Spacing = N/A inches Elliptical Slot Centroid = N/A feet Orifice Plate: Orifice Area per Row = N/A inches Elliptical Slot Area = N/A ft2 User Input: Stage and Total Area of Each Orifice Row (numbered from lowest to highest) Row 1 (optional) Row 2 (optional) Row 3 (optional) Row 4 (optional) Row 5 (optional) Row 6 (optional) Row 7 (optional) Row 8 (optional) Stage of Orifice Centroid (ft) N/A N/A N/A N/A N/A N/A N/A N/A Orifice Area (sq. inches) N/A N/A N/A N/A N/A N/A N/A N/A Row 9 (optional) Row 10 (optional) Row 11 (optional) Row 12 (optional) Row 13 (optional) Row 14 (optional) Row 15 (optional) Row 16 (optional) Stage of Orifice Centroid (ft) N/A N/A N/A N/A N/A N/A N/A N/A Orifice Area (sq. inches) N/A N/A N/A N/A N/A N/A N/A N/A User Input: Vertical Orifice (Circular or Rectangular) Calculated Parameters for Vertical Orifice Zone 1 Circular Not Selected Zone 1 Circular Not Selected Invert of Vertical Orifice = 0.00 ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Area =ft2 Depth at top of Zone using Vertical Orifice = 2.54 ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Centroid = feet Vertical Orifice Diameter = inches User Input: Overflow Weir (Dropbox) and Grate (Flat or Sloped) Calculated Parameters for Overflow Weir Not Selected Not Selected Not Selected Not Selected Overflow Weir Front Edge Height, Ho =ft (relative to basin bottom at Stage = 0 ft)Height of Grate Upper Edge, Ht = feet Overflow Weir Front Edge Length = feet Over Flow Weir Slope Length = feet Overflow Weir Slope = H:V (enter zero for flat grate) Grate Open Area / 100-yr Orifice Area =should be > 4 Horiz. Length of Weir Sides = feet Overflow Grate Open Area w/o Debris =ft2 Overflow Grate Open Area % = %, grate open area/total area Overflow Grate Open Area w/ Debris =ft2 Debris Clogging % = % User Input: Outlet Pipe w/ Flow Restriction Plate (Circular Orifice, Restrictor Plate, or Rectangular Orifice) Calculated Parameters for Outlet Pipe w/ Flow Restriction Plate Not Selected Not Selected Not Selected Not Selected Depth to Invert of Outlet Pipe =ft (distance below basin bottom at Stage = 0 ft)Outlet Orifice Area =ft2 Circular Orifice Diameter = inches Outlet Orifice Centroid = feet Half-Central Angle of Restrictor Plate on Pipe = N/A N/A radians User Input: Emergency Spillway (Rectangular or Trapezoidal) Calculated Parameters for Spillway Spillway Invert Stage= 2.60 ft (relative to basin bottom at Stage = 0 ft) Spillway Design Flow Depth= 0.57 feet Spillway Crest Length = 2.00 feet Stage at Top of Freeboard = 4.17 feet Spillway End Slopes = 4.00 H:V Basin Area at Top of Freeboard = 0.22 acres Freeboard above Max Water Surface = 1.00 feet Routed Hydrograph Results Design Storm Return Period =WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year 500 Year One-Hour Rainfall Depth (in) =0.53 1.07 0.87 1.15 1.45 1.96 2.43 2.97 4.50 Calculated Runoff Volume (acre-ft) =0.019 0.061 0.036 0.052 0.073 0.116 0.151 0.198 0.323 OPTIONAL Override Runoff Volume (acre-ft) = Inflow Hydrograph Volume (acre-ft) =0.019 0.061 0.035 0.051 0.073 0.116 0.151 0.197 0.323 Predevelopment Unit Peak Flow, q (cfs/acre) =0.00 0.00 0.01 0.02 0.26 0.95 1.45 2.09 3.73 Predevelopment Peak Q (cfs) =0.0 0.0 0.0 0.0 0.3 0.9 1.4 2.1 3.7 Peak Inflow Q (cfs) =0.5 1.6 0.9 1.3 1.9 3.0 3.9 5.0 8.2 Peak Outflow Q (cfs) =0.2 1.0 3.7 Ratio Peak Outflow to Predevelopment Q =0.1 0.5 1.0 Structure Controlling Flow =Spillway Spillway Spillway Max Velocity through Grate 1 (fps) =N/A N/A N/A Max Velocity through Grate 2 (fps) =N/A N/A N/A Time to Drain 97% of Inflow Volume (hours) =>120 >120 >120 Time to Drain 99% of Inflow Volume (hours) =>120 >120 >120 Maximum Ponding Depth (ft) =2.70 2.84 3.09 Area at Maximum Ponding Depth (acres) =0.14 0.15 0.16 Maximum Volume Stored (acre-ft) =0.141 0.162 0.201 Detention Basin Outlet Structure Design UD-Detention, Version 3.07 (February 2017) 142 Timberline Detention Pond 1 - Includes Basins 1 and 2 Example Zone Configuration (Retention Pond) COUNTA for Basin Tab =1 Ao Dia WQ Plate Type Vert Orifice 1 Vert Orifice 2 Count_Underdrain =0 0.11(diameter = 3/8 inch)1 2 1 Count_WQPlate =0 0.14(diameter = 7/16 inch) Count_VertOrifice1 =0 0.18(diameter = 1/2 inch)Outlet Plate 1 Outlet Plate 2 Drain Time Message Boolean Count_VertOrifice2 =0 0.24(diameter = 9/16 inch)1 1 5yr, <72hr 0 Count_Weir1 =0 0.29(diameter = 5/8 inch)>5yr, <120hr 0 Count_Weir2 =0 0.36(diameter = 11/16 inch)Max Depth Row Count_OutletPipe1 =0 0.42(diameter = 3/4 inch)WQCV #VALUE! Watershed Constraint Check Count_OutletPipe2 =0 0.50(diameter = 13/16 inch)2 Year #VALUE! Slope 0.040 COUNTA_2 (Standard FSD Setup)=0 0.58(diameter = 7/8 inch)EURV #VALUE! Shape 1.00 MaxPondDepth_Error? FALSE 0.67(diameter = 15/16 inch)5 Year #VALUE! Hidden Parameters & Calculations 0.76 (diameter = 1 inch)10 Year #VALUE! Spillway Depth 0.86(diameter = 1-1/16 inches)25 Year #VALUE! 0.57 WQ Plate Flow at 100yr depth =0.00 0.97(diameter = 1-1/8 inches)50 Year 271 CLOG #1=0%1.08(diameter = 1-3/16 inches)100 Year 285 0 Z1_Boolean Cdw #1 =1.20(diameter = 1-1/4 inches)500 Year 310 1 Z2_Boolean Cdo #1 =1.32(diameter = 1-5/16 inches)Zone3_Pulldown Message 1 Z3_Boolean Overflow Weir #1 Angle =1.45(diameter = 1-3/8 inches)1 Opening Message CLOG #2=0%1.59(diameter = 1-7/16 inches)Draintime Running Cdw #2 =1.73(diameter = 1-1/2 inches)Outlet Boolean Outlet Rank Total (1 to 4) Cdo #2 =1.88(diameter = 1-9/16 inches)Vertical Orifice 1 0 0 0 Overflow Weir #2 Angle =2.03(diameter = 1-5/8 inches)Vertical Orifice 2 0 0 Boolean Underdrain Q at 100yr depth =0.00 2.20(diameter = 1-11/16 inches)Overflow Weir 1 0 0 0 Max Depth VertOrifice1 Q at 100yr depth =0.00 2.36(diameter = 1-3/4 inches)Overflow Weir 2 0 0 0 500yr Depth VertOrifice2 Q at 100yr depth =0.00 2.54(diameter = 1-13/16 inches)Outlet Pipe 1 0 0 1 Freeboard EURV_draintime_user = 2.72(diameter = 1-7/8 inches)Outlet Pipe 2 0 0 1 Spillway Count_User_Hydrographs 0 2.90(diameter = 1-15/16 inches)0 Spillway Length CountA_3 (EURV & 100yr) =0 3.09(diameter = 2 inches)Button Visibility Boolean FALSE Time Interval CountA_4 (100yr Only) = 0 3.29(use rectangular openings)1 Button_Trigger 0 Underdrain 0 WQCV Plate 0 EURV-WQCV Plate 0 EURV-WQCV VertOrifice 0 Outlet 90% Qpeak 0 Outlet Undetained S-A-V-D Chart Axis Override X-axis Left Y-Axis Right Y-Axis minimum bound maximum bound UD-Detention, Version 3.07 (February 2017) Detention Basin Outlet Structure Design 0 1 2 3 4 5 6 7 8 9 0.1 1 10FLOW [cfs]TIME [hr] 500YR IN 500YR OUT 100YR IN 100YR OUT 50YR IN 50YR OUT 25YR IN 25YR OUT 10YR IN 10YR OUT 5YR IN 5YR OUT 2YR IN 2YR OUT EURV IN EURV OUT WQCV IN WQCV OUT 0 0.5 1 1.5 2 2.5 3 3.5 0.1 1 10 100PONDING DEPTH [ft]DRAIN TIME [hr] 500YR 100YR 50YR 25YR 10YR 5YR 2YR EURV WQCV 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 OUTFLOW [cfs]AREA [ft^2], VOLUME [ft^3]PONDING DEPTH [ft] User Area [ft^2] Interpolated Area [ft^2] Summary Area [ft^2] Volume [ft^3] Summary Volume [ft^3] Outflow [cfs] Summary Outflow [cfs] Detention Pond 1 Stage-Storage Rating Project: 142 Timberline Basin Description: Detention Pond 1 Contour Contour Depth Incremental Cumulative Elevation Area (ft) Volume Volume (sq. ft) Conic Conic (cu. ft.) (cu. ft.) 4,934.00 0.00 N/A N/A 0.00 4,934.50 484.43 0.50 80.74 80.74 4,935.00 1,813.65 0.50 539.24 619.97 4,935.50 2,279.61 0.50 1021.10 1641.07 4,936.00 2,844.42 0.50 1278.41 2919.48 4,936.50 5,448.49 0.50 2038.27 4957.75 4,937.00 6,750.76 0.50 3044.00 8001.76 4,937.50 8,231.33 0.50 3739.41 11741.17 4,938.00 9,751.73 0.50 4490.40 16231.57 100 Year This is to convert % imp. to a C value 100-year (must insert % imp. and C pervious). ft3 acre-ft. 'C' value 0.57 (2 yr)7904.8 0.181 'C' * 1.25 0.7125 (100 yr) Area 0.99 acres Modified Modified Release Rate 0.2 M. FATER D. JUDISH C. LI 5/95 Nov-97 Nov-98 DETENTION POND SIZING TIME TIME INTENSITY Q 100 Runoff Release Required Required cum 100 year Volume Cum total Detention Detention (mins)(secs)(in/hr)(cfs)(ft^3)(ft^3)(ft^3)(ac-ft) 0 0 0 0.00 0 0.0 0.0 0.0000 5 300 9.950 7.02 2105.544 60.0 2045.5 0.0470 10 600 7.720 5.45 3267.297 120.0 3147.3 0.0723 15 900 6.520 4.60 4139.141 180.0 3959.1 0.0909 20 1200 5.600 3.95 4740.12 240.0 4500.1 0.1033 25 1500 4.980 3.51 5269.151 300.0 4969.2 0.1141 30 1800 4.520 3.19 5738.931 360.0 5378.9 0.1235 35 2100 4.080 2.88 6043.653 420.0 5623.7 0.1291 40 2400 3.740 2.64 6331.446 480.0 5851.4 0.1343 45 2700 3.460 2.44 6589.613 540.0 6049.6 0.1389 50 3000 3.230 2.28 6835.084 600.0 6235.1 0.1431 55 3300 3.030 2.14 7053.045 660.0 6393.0 0.1468 60 3600 2.860 2.02 7262.541 720.0 6542.5 0.1502 65 3900 2.720 1.92 7482.618 780.0 6702.6 0.1539 70 4200 2.590 1.83 7673.069 840.0 6833.1 0.1569 75 4500 2.480 1.75 7871.985 900.0 6972.0 0.1601 80 4800 2.380 1.68 8058.204 960.0 7098.2 0.1630 85 5100 2.290 1.62 8238.075 1020.0 7218.1 0.1657 90 5400 2.210 1.56 8417.945 1080.0 7337.9 0.1685 95 5700 2.130 1.50 8563.958 1140.0 7424.0 0.1704 100 6000 2.060 1.45 8718.435 1200.0 7518.4 0.1726 105 6300 2.000 1.41 8887.725 1260.0 7627.7 0.1751 110 6600 1.940 1.37 9031.622 1320.0 7711.6 0.1770 115 6900 1.890 1.33 9198.795 1380.0 7818.8 0.1795 120 7200 1.840 1.30 9344.808 1440.0 7904.8 0.1815 125 7500 1.790 1.26 9469.659 1500.0 7969.7 0.1830 130 7800 1.750 1.23 9628.369 1560.0 8068.4 0.1852 135 8100 1.710 1.21 9770.149 1620.0 8150.1 0.1871 140 8400 1.670 1.18 9895.001 1680.0 8215.0 0.1886 145 8700 1.630 1.15 10002.92 1740.0 8262.9 0.1897 150 9000 1.600 1.13 10157.4 1800.0 8357.4 0.1919 155 9300 1.570 1.11 10299.18 1860.0 8439.2 0.1937 160 9600 1.540 1.09 10428.26 1920.0 8508.3 0.1953 165 9900 1.510 1.07 10544.65 1980.0 8564.7 0.1966 170 10200 1.480 1.04 10648.34 2040.0 8608.3 0.1976 175 10500 1.450 1.02 10739.33 2100.0 8639.3 0.1983 180 10800 1.420 1.00 10817.63 2160.0 8657.6 0.1988 185 11100 1.400 0.99 10961.53 2220.0 8741.5 0.2007 190 11400 1.380 0.97 11096.96 2280.0 8817.0 0.2024 195 11700 1.360 0.96 11223.93 2340.0 8883.9 0.2039 200 12000 1.340 0.95 11342.43 2400.0 8942.4 0.2053 205 12300 1.320 0.93 11452.47 2460.0 8992.5 0.2064 210 12600 1.300 0.92 11554.04 2520.0 9034.0 0.2074 215 12900 1.280 0.90 11647.15 2580.0 9067.2 0.2082 220 13200 1.260 0.89 11731.8 2640.0 9091.8 0.2087 225 13500 1.240 0.87 11807.98 2700.0 9108.0 0.2091 230 13800 1.220 0.86 11875.69 2760.0 9115.7 0.2093 235 14100 1.210 0.85 12034.4 2820.0 9214.4 0.2115 240 14400 1.200 0.85 12188.88 2880.0 9308.9 0.2137 Required detention Page 1 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020 Wednesday, 04 / 21 / 2021 Hyd. No. 3 Basins 1-2 Hydrograph type = Combine Peak discharge = 6.714 cfs Storm frequency = 100 yrs Time to peak = 5 min Time interval = 1 min Hyd. volume = 2,829 cuft Inflow hyds. = 1, 2 Contrib. drain. area = 0.990 ac 0 2 4 6 8 10 12 14 16 18 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 5.00 5.00 6.00 6.00 7.00 7.00 Q (cfs) Time (min) Basins 1-2 Hyd. No. 3 -- 100 Year Hyd No. 3 Hyd No. 1 Hyd No. 2 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020 Wednesday, 04 / 21 / 2021 Hyd. No. 4 Pond 1 Routing Hydrograph type = Reservoir Peak discharge = 0.179 cfs Storm frequency = 100 yrs Time to peak = 16 min Time interval = 1 min Hyd. volume = 2,828 cuft Inflow hyd. No. = 3 - Basins 1-2 Max. Elevation = 4935.91 ft Reservoir name = Pond 1 Max. Storage = 2,682 cuft Storage Indication method used. 0 60 120 180 240 300 360 420 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 5.00 5.00 6.00 6.00 7.00 7.00 Q (cfs) Time (min) Pond 1 Routing Hyd. No. 4 -- 100 Year Hyd No. 4 Hyd No. 3 Total storage used = 2,682 cuft Pond Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2020 Wednesday, 04 / 21 / 2021 Pond No. 1 - Pond 1 Pond Data Pond storage is based on user-defined values. Stage / Storage Table Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft) 0.00 4934.00 n/a 0 0 0.50 4934.50 n/a 81 81 1.00 4935.00 n/a 539 620 1.50 4935.50 n/a 1,021 1,641 2.00 4936.00 n/a 1,278 2,919 2.50 4936.50 n/a 2,038 4,958 3.00 4937.00 n/a 3,044 8,002 3.50 4937.50 n/a 3,739 11,741 4.00 4938.00 n/a 4,490 16,232 Culvert / Orifice Structures Weir Structures [A] [B] [C] [PrfRsr] [A] [B] [C] [D] Rise (in)= 2.25 0.00 0.00 0.00 Span (in)= 2.25 0.00 0.00 0.00 No. Barrels = 1 0 0 0 Invert El. (ft)= 4934.00 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)= 10.00 0.00 0.00 0.00 Crest El. (ft)= 4937.50 0.00 0.00 0.00 Weir Coeff.= 2.60 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 4934.00 0.00 --- --- --- 0.00 --- --- --- --- --- 0.000 0.50 81 4934.50 0.08 ic --- --- --- 0.00 --- --- --- --- --- 0.085 1.00 620 4935.00 0.13 ic --- --- --- 0.00 --- --- --- --- --- 0.127 1.50 1,641 4935.50 0.16 ic --- --- --- 0.00 --- --- --- --- --- 0.158 2.00 2,919 4936.00 0.18 ic --- --- --- 0.00 --- --- --- --- --- 0.184 2.50 4,958 4936.50 0.21 ic --- --- --- 0.00 --- --- --- --- --- 0.206 3.00 8,002 4937.00 0.23 ic --- --- --- 0.00 --- --- --- --- --- 0.227 3.50 11,741 4937.50 0.25 ic --- --- --- 0.00 --- --- --- --- --- 0.245 4.00 16,232 4938.00 0.26 ic --- --- --- 9.19 --- --- --- --- --- 9.455 Weir Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Thursday, Mar 25 2021 Detention Pond 1 - Emergency Overflow Weir - Q100= 6.8 cfs Trapezoidal Weir Crest = Sharp Bottom Length (ft) = 10.00 Total Depth (ft) = 0.50 Side Slope (z:1) = 4.00 Calculations Weir Coeff. Cw = 3.10 Compute by: Known Q Known Q (cfs) = 7.10 Highlighted Depth (ft) = 0.35 Q (cfs) = 7.100 Area (sqft) = 3.99 Velocity (ft/s) = 1.78 Top Width (ft) = 12.80 0 2 4 6 8 10 12 14 16 18 Depth (ft) Depth (ft)Detention Pond 1 - Emergency Overflow Weir - Q100= 6.8 cfs -0.50 -0.50 0.00 0.00 0.50 0.50 1.00 1.00 Length (ft)Weir W.S. Stormwater Facility Name: Facility Location & Jurisdiction: User Input: Watershed Characteristics User Defined User Defined User Defined User Defined Watershed Slope =0.044 ft/ft Stage [ft] Area [ft^2] Stage [ft] Discharge [cfs] Watershed Length =181 ft 0.00 0 0.00 0.00 Watershed Area = 0.99 acres 0.50 484 0.50 0.09 Watershed Imperviousness = 57.0%percent 1.00 1,814 1.00 0.13 Percentage Hydrologic Soil Group A =percent 1.50 2,280 1.50 0.16 Percentage Hydrologic Soil Group B = 100.0%percent 2.00 2,844 2.00 0.18 Percentage Hydrologic Soil Groups C/D =percent 2.50 5,449 2.50 0.21 3.00 6,751 3.00 0.23 User Input 17 3.50 8,231 3.50 0.25 4.00 9,752 4.00 9.46 WQCV Treatment Method =hours After completing and printing this worksheet to a pdf, go to: https://maperture.digitaldataservices.com/gvh/?viewer=cswdif create a new stormwater facility, and attach the pdf of this worksheet to that record. Routed Hydrograph Results Design Storm Return Period =WQCV 2 Year 5 Year 10 Year 50 Year 100 Year One-Hour Rainfall Depth =0.53 0.85 1.12 1.41 2.34 2.84 in Calculated Runoff Volume =0.036 0.050 0.071 0.145 0.189 acre-ft OPTIONAL Override Runoff Volume =acre-ft Inflow Hydrograph Volume =0.035 0.049 0.071 0.145 0.188 acre-ft Time to Drain 97% of Inflow Volume =3.7 4.6 6.1 10.1 12.3 hours Time to Drain 99% of Inflow Volume =3.9 4.9 6.3 10.6 12.8 hours Maximum Ponding Depth =1.21 1.46 1.81 2.57 2.87 ft Maximum Ponded Area =0.05 0.05 0.06 0.13 0.15 acres Maximum Volume Stored = 0.025 0.037 0.057 0.125 0.166 acre-ft Stormwater Detention and Infiltration Design Data Sheet Pond 1 N. Timberline Road and International Boulevard, Fort Collins, Colorado Location for 1-hr Rainfall Depths (use dropdown): Workbook Protected Worksheet Protected SDI_Design_Data_v1.08.xlsm, Design Data 4/21/2021, 12:38 PM WQCV_Trigger = 1 RunOnce= 1 CountA=1 Draintime Coeff= 1.0 0 1 2 3 #N/A #N/A 0 1 2 3 #N/A #N/A Check Data Set 1 Check Data Set 1 Stormwater Detention and Infiltration Design Data Sheet Area Discharge 0 1 2 3 4 5 6 0.1 1 10FLOW [cfs]TIME [hr] 100YR IN 100YR OUT 50YR IN 50YR OUT 10YR IN 10YR OUT 5YR IN 5YR OUT 2YR IN 2YR OUT WQCV IN WQCV OUT 0 0.5 1 1.5 2 2.5 3 3.5 0.1 1 10 100PONDING DEPTH [ft]DRAIN TIME [hr] 100YR 50YR 10YR 5YR 2YR WQCV SDI_Design_Data_v1.08.xlsm, Design Data 4/21/2021, 12:38 PM Appendix C Sheet 1 of 1 Designer: Company: Date: Project: Location: 1. To identify potential BMPs, what best describes the type of site? SKIP # 2 2. Does the typical section include a parking lane, shoulder, median, or otherwise allow for surface BMPs? 3. Is the site comprised of Hydrologic Soil Group A or B soils? 4.Is the tributary impervious area1 greater than 1 acre? SKIP #6-10 5. Is the depth of bedrock greater than 5 feet? 6.Is the tributary impervious area1 greater than 5 acres? 7. Is a water source available for use? (baseflow or groundwater) 8.Is the BMP in a developing watershed? 9. Are BMPs allowed in the right-of-way? 10. Does the community have an established Fee in Lieu Program in place? 11.Step 1 of Four Step Process: Grass Buffer MDCIA / Volume Reduction (Not WQCV) BMPs Grass Swale Permeable Pavement- Full Infiltration (5) Green Roof (3) 12.Step 2 of Four Step Process:Permeable Pavement- Full Infiltration (5) WQCV BMPs Bioretention- Full Infiltration (5) Sand Filter Extended Detention Basin- Full Infiltration (5) Green Roof (3) Regional Water Quality Treatment (4) Notes: 1. 'Tributary impervious area' refers to the impervious area draining to the BMP, not the total area of the project site. 2. For a successful wetland channel or basin, a water source (groundwater or baseflow) will be required. 3. In the Front Range of Colorado, irrgation, at least periodically in dry times, will be required to sustain a green roof. 4. If a regional facility will be used to provide the WQCV, some degree of onsite treatment/MDCIA will still likely be required. 5. No Infiltration= underdrain and liner, Partial Infiltration= underdrain and no liner, Full Infiltration= no underdrain and no liner. 6. Consider this BMP for a portion of your site. It's best suited for impervious tributary areas of approximately one acre or less. Design Procedure Form: BMP Selection Tool Mary B. Wohnrade, P.E. Wohnrade Civil Engineers, Inc. September 10, 2020 Timberline-International Timberline Road, Fort Collins, CO UD-BMP (Version 3.07, March 2018) Choose One Highly Urbanized Site Conventional Site Choose One YES NO Choose One YES NO Choose One YES NO Choose One YES NO Choose One YES NO Choose One YES NO Choose One YES NO Choose One YES NO Linear Construction in Urbanized Area Choose One YES NO TIM_UD-BMP_v3.07_SELECTION_TOOL.xlsm, BMP Selection Tool 9/10/2020, 6:03 PM Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =70.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.700 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.22 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 30,933 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 =0.35 in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER =462 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =9 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =433 sq ft D) Actual Flat Surface Area AActual =2163 sq ft E) Area at Design Depth (Top Surface Area)ATop =3188 sq ft F) Rain Garden Total Volume VT=2,033 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided?1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y =1.5 ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =462 cu ft iii) Orifice Diameter, 3/8" Minimum DO =1/2 in Design Procedure Form: Rain Garden (RG) Mary B. Wohnrade, P.E. Wohnrade Civil Engineers, Inc. February 15, 2021 Timberline-International - Rain Garden No. 1 Fort Collins, Colorado UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO UD-BMP_v3.07-Rain_Garden.xlsm, RG 2/15/2021, 5:16 PM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) Mary B. Wohnrade, P.E. Wohnrade Civil Engineers, Inc. February 15, 2021 Timberline-International - Rain Garden No. 1 Fort Collins, Colorado Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO UD-BMP_v3.07-Rain_Garden.xlsm, RG 2/15/2021, 5:16 PM Appendix D Culvert Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Tuesday, Aug 7 2018 Future Storm Sewer Line Invert Elev Dn (ft) = 4923.48 Pipe Length (ft) = 392.47 Slope (%) = 0.40 Invert Elev Up (ft) = 4925.05 Rise (in) = 30.0 Shape = Circular Span (in) = 30.0 No. Barrels = 1 n-Value = 0.013 Culvert Type = Circular Concrete Culvert Entrance = Square edge w/headwall (C) Coeff. K,M,c,Y,k = 0.0098, 2, 0.0398, 0.67, 0.5 Embankment Top Elevation (ft) = 4941.89 Top Width (ft) = 24.00 Crest Width (ft) = 100.00 Calculations Qmin (cfs) = 0.00 Qmax (cfs) = 23.00 Tailwater Elev (ft) = Normal Highlighted Qtotal (cfs) = 23.00 Qpipe (cfs) = 23.00 Qovertop (cfs) = 0.00 Veloc Dn (ft/s) = 5.97 Veloc Up (ft/s) = 6.78 HGL Dn (ft) = 4925.31 HGL Up (ft) = 4926.68 Hw Elev (ft) = 4927.61 Hw/D (ft) = 1.02 Flow Regime = Inlet Control Project:Date:Sheets11582 Colony Row Broomfield, Colorado 80021 Phone: (720)259-0965 Fax: (720)259-1519 No.Revisions:By:Date: WOHNRADE CIVIL ENGINEERS, INC.257/22/2021TIM: 1805.00Scale:Designed By:Reviewed By:Sheet16MBWJDM1"=20'CALL UTILITY NOTIFICATION CENTER OFCOLORADOKnow what'sbelow.before you dig.CallR