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HomeMy WebLinkAboutHEARTSIDE HILL ODP - ODP210005 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT PRELIMINARY DRAINAGE REPORT FOR Heartside Hill Prepared by: Highland Development Services 6355 Fairgrounds Ave, Suite 100 Windsor, Colorado 80550 Phone: 970.674.7550 Prepared for: CARE Housing, Inc. 1303 W. Swallow Road Fort Collins, CO 80525 Office: 970.282.7522 December 22, 2021 Job Number 21-1045-00 Highland Development Services, Inc. 6355 Fairgrounds Avenue, Suite 100 | Windsor, CO 80550 | 970.674.7550 December 22, 2021 Mr. Matt Simpson, P.E. Fort Collins Utilities 700 Wood Street Fort Collins, CO 80522 RE: Preliminary Drainage Report for Magnolia Dwellings Dear Dan, We are pleased to submit for your review, the Preliminary Drainage Report for the Heartside Hill affordable residential housing project. This report describes the drainage design intent to be in accordance with the City of Fort Collins Stormwater Criteria Manual. We appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Sincerely, Highland Development Services Andrew C. Bartel, EI Jason T. Claeys, P.E., LEED AP Page i TABLE OF CONTENTS Table of Contents ............................................................................................................................. i Engineer Certification ......................................................................................................................ii General Description and Location .................................................................................................. 1 Site Description and Location ...................................................................................................... 1 Site Soils ....................................................................................................................................... 2 Storm Drainage Criteria .................................................................................................................. 3 Hydrologic Criteria ....................................................................................................................... 3 Hydraulic Criteria ......................................................................................................................... 3 Drainage Basins ............................................................................................................................... 4 Drainage Facility Design .................................................................................................................. 6 Drainage Conveyance Design ...................................................................................................... 6 Low Impact Development ............................................................................................................... 7 Stormwater Pollution Prevention ................................................................................................... 9 Conclusions ................................................................................................................................... 10 References .................................................................................................................................... 11 Appendix ....................................................................................................................................... 12 Appendix A – Site Descriptions, Characteristics, & References .................................................. A Appendix B – Rational Calculations ............................................................................................. B Appendix C – Low Impact Development Calculations ................................................................. C Appendix D – Pond Calculations .................................................................................................. D Page ii ENGINEER CERTIFICATION I hereby certify that this report (plan) for the preliminary drainage design of Heartside Hill was prepared by me (or under my direct supervision) in accordance with the provisions of the City of Fort Collins Stormwater Criteria Manual and Construction of Public and Private Improvements for the Responsible Parties thereof. I understand that the City of Fort Collins does not and shall not assume liability for drainage facilities designed by others. ________________________________________ Jason T. Claeys, PE Registered Professional Engineer State of Colorado No. 42122 Page 1 GENERAL DESCRIPTION AND LOCATION SITE DESCRIPTION AND LOCATION The project site is situated in the southeast quarter of Section 12, Township 6 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, in the State of Colorado. The property consists of Lots 1 and 2, Block 1 of the Heart of the Rockies Second Subdivision, dated June 9, 1999. Heartside Hill is located within Lot 2, at the northwest corner of the intersection of S. Lemay Ave. and E. Trilby Rd. Lot 1 contains the existing Heart of the Rockies Christian Church. It is bounded by private residential lots to the north and west, E. Trilby Rd. to the south, and S Lemay Ave to the east. The existing church facilities are anticipated to remain. The site area is currently undeveloped and is approximately 8.84 acres. The development would consist of up to 72 CARE Housing for rent apartment units ([1] 8-unit with an attached clubhouse, [5] 8-unit and [2] 12-unit buildings), 9 Habitat for Humanity single-family detached lots, 2 L’arche group homes, and a planned shared community center to be designed and constructed at a future date. The project is anticipated to be completed in a single phase. The project site generally slopes from the southwest to the northeast at approximately 4% toward an existing pond at the northeast of the property. Storm runoff is currently conveyed from a grate inlet in the pond to a ditch along the east side of the property and into the existing storm drain sewer. The existing project site is approximately 0.0% impervious. No wetlands are located within the area of proposed development. The project site is not located within the FEMA floodway or floodplain and is within the non- printed FEMA FIRM panel 08069C1200F, effective 12/19/2006. The site is also not located within the City of Fort Collins floodplain. The proposed development includes eight multi-family buildings with a clubhouse along with eleven low income housing lots. The required parking areas, driveways, sidewalks, and open space are also included in the development. A rain garden is proposed to provide the stormwater quality enhancement requirement as a low impact development technique. The site was previously analyzed within the “Drainage Investigation for Heart of the Rockies Christian Church,” prepared by Messner Engineering, Inc., dated June 29, 1999. Page 2 SITE SOILS The Heatside Hill project site consists primarily of Renohill clay loam and a small portion of Longmont clay and are both classified as Type D hydrologic group. According to USDA/Natural Resource Conservation Group, Type D soils a have very slow infiltration rate when thoroughly wet. These soils 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 also have a very slow rate of water transmission. Per the “Preliminary Geotechnical Subsurface Exploration Report, Proposed Residential Development Lots 1 and 2, Heart of the Rockies Second Subdivision”, prepared by Soilogic, Inc. dated August 13, 2021: “The subsurface materials encountered in the completed site borings were quite variable across the site, but generally consisted of a thin mantle of vegetation and topsoil underlain by brown/beige/rust lean clay with varying amounts of sand. A portion of the near-surface lean clay encountered at the location of boring B-2 extending to a depth of about 3 to 4 feet below ground surface was somewhat mottled in color, appeared to contain bedrock fragments and was identified as possible existing fill material which may have been placed to develop present site grade. In general, the lean clay varied from medium stiff to very stiff in terms of consistency, exhibited variable swell potential (ranging from none to very high) at current moisture and density conditions and extended to depths between 2½ to 18 feet below present site grade, where it was underlain by brown/olive/beige/gray/rust interbedded claystone/siltstone/ sandstone bedrock of varying composition. The bedrock varied from weathered to very hard in terms of hardness, also exhibited variable swell potential (ranging from low to high) at in-situ moisture and density conditions and extended to the bottom of each boring at depths ranging from approximately 15 to 30 feet below present site grades. In general, we judge the bedrock unit underlying the site to possess moderate to high swell potential overall.” Groundwater was also observed during the subsurface soil exploration: “Groundwater was measured in borings B-1, B-2, B-3 and B-6 at depths between about 13 and 27 feet below ground surface, but was not encountered in any of the remaining site borings to the depths explored when checked immediately after completion of drilling. When checked seven (7) days after drilling, groundwater was measured in all borings with the exception of boring B-3 at depths between about 5 and 15 feet below ground surface. The ground surface in the area of boring B-3 had been disturbed, such that subsequent groundwater level measurements could not be completed.” Page 3 STORM DRAINAGE CRITERIA This preliminary drainage report was prepared to meet or exceed the City of Fort Collins Stormwater Criteria Manual. The Criteria Manual and amendments to the Urban Drainage Flood Control District’s (UDFCD) Drainage Criteria Manual (USDCM) Volumes 1, 2 and 3 were referenced as guidelines for this design. HYDROLOGIC CRITERIA The rational method was performed to calculate the peak runoff rates for each basin. Percent imperviousness and runoff coefficients were calculated for each basin using the surface characteristics of each basin. The time of concentration was calculated using City of Fort Collins initial time of concentration and the intensity was calculated using the corresponding storm rainfall depth and the City of Fort Collins’ Intensity-Duration-Frequency Curve. The City of Fort Collins area has a 2-yr, 1-hr rainfall depth of 0.82 inches and a 100-yr, 1-hr rainfall depth of 2.86 inches. These depths do account for the 1999 adjusted rainfall depths. HYDRAULIC CRITERIA The final Heartside Hill storm drainage system will been designed to convey the minor and major storm events through the combination of private drives, storm sewer pipes and swales. Runoff flows determined with the rational method will be attenuated through the site. Inlet capacities will be calculated using UDFCD’s spreadsheet UD-Inlet_v4.05.xlsm. The Autodesk Hydraflow Express program will be used to compute the open channel hydraulics and check the capacities of the drainage swales throughout the site. Flow velocities within these swales will be reviewed and where flows are found to be supercritical, the swales will be lined with turf reinforcement mat. All swale and pipe outlets will be protected with riprap or suitable erosion protection methods. Storm sewer pipe outlets will be protected using the requirements set by the USDCM for the protection downstream of culverts. All supporting calculations are located in the Appendix. Page 4 DRAINAGE BASINS The Heartside Hill developed drainage basins are delineated by areas draining through the site. The drainage basins are placed to limit the runoff flowing from the site into Brittany Street. The site is broken into 10 main drainage systems: Drainage Basin D1: Drainage Basin D1 has an approximate area of 1.05 acres and is approximately 36.7% impervious. This basin consists of a future community center and open space. Runoff is conveyed via swales to a curb cut and is conveyed through Rain Garden D1 to detention Pond D. Drainage Basin D2: Drainage Basin D2 has an approximate area of 2.47 acres and is approximately 50.9% impervious. This basin consists of half of the existing church building, nine of the low income housing lots, private drives, parking areas, and a majority of the open space/amphitheater area. The area along the low income housing lots draining to Type R inlet, Ex Inlet-03, is negligible and the capture rate is assumed to be the same as the approved. Runoff is conveyed via private drives, through two curb cuts, into Rain Garden D1 and is ultimately discharged to detention Pond D. Drainage Basin D3: Drainage Basin D3 has an approximate area of 0.75 acres and is approximately 34.1% impervious. This basin consists of two of the multi-family buildings, the attached clubhouse, and Rain Garden D1. Runoff is conveyed via swales to Rain Garden D1 and is discharged to detention Pond D. Drainage Basin D4: Drainage Basin D4 has an approximate area of 1.09 acres and is approximately 27.3% impervious. This basin consists of three multi-family buildings and open space. Runoff is conveyed via swales and is discharged to detention Pond D. Drainage Basin D5: Drainage Basin D5 has an approximate area of 0.42 acres and is approximately 97.1% impervious. This basin consists of private drives and parking areas. Runoff is conveyed via private drives, storm drains, and swales to a type R inlet and is ultimately discharged to detention Pond D. Page 5 Drainage Basin D6: Drainage Basin D6 has an approximate area of 0.13 acres and is approximately 78.6% impervious. This basin consists of the private drive access from Trilby Rd. Runoff is conveyed to a curb cut and is ultimately discharged to detention Pond D. Drainage Basin D7: Drainage Basin D7 has an approximate area of 0.79 acres and is approximately 35.2% impervious. This basin consists of three multi-family buildings and open space. Runoff is conveyed via swales and is ultimately conveyed to detention Pond D. Drainage Basin D8: Drainage Basin D8 has an approximate area of 0.70 acres and is approximately 92.3% impervious. This basin consists of private drives and parking areas. Runoff is conveyed via private drives to a curb cut, where it is discharged into detention Pond D. Drainage Basin D9: Drainage Basin D9 has an approximate area of 1.42 acres and is approximately 20.6% impervious. This basin consists of a part of a multi-family building, private drives, parking areas, two low income lots, open space, and detention Pond D. Runoff is conveyed via private drives and swales to detention Pond D. Drainage Basin OS1: Drainage Basin OS1 pertains to the drainage from the existing improvements in Lot 1. This basin has an approximate area of 1.89 acres and is approximately 69.8% impervious. This basin consists of half of the existing church building, private drives, parking areas, and open space. Runoff is conveyed via roadways to a swale and is ultimately conveyed through Rain Garden D1 to detention Pond D. Page 6 DRAINAGE FACILITY DESIGN DRAINAGE CONVEYANCE DESIGN Storm infrastructure to convey runoff will include swales, inlets, and storm sewer pipes. Stormwater detention and water quality enhancement are achieved through the use of detention Pond D and Rain Garden D1. DETENTION/WATER QUALITY POND DESIGN An extended detention basin, Detention Pond D, will be utilized as the detention and water quality facility for Heartside Hill. For the preliminary drainage study, the FAA method was used to determine the detention volume needed. UDFCD is referenced for the standard water quality capture volume (WQCV) with a 40-hr drain time. Below is a brief summary of the proposed design for the pond: Pond D: Extended detention basin for both Lots 1 and 2 with standard water quality treatment. A 100-yr orifice plate maximizes volume in the pond and restricts release rate into the existing stormwater system. The existing 100-yr release rate into the existing stormwater system is 13.2 cfs according to the Drainage Investigation for Heart of the Rockies Christian Church, prepared by Messner Engineering, Inc (Revised June 29, 1999). The 100-yr water surface elevation is 4911.05 feet, with a maximum depth in the pond of 3.35 feet. During an event that exceeds the 100-yr storm, or the pond outlet should be obstructed, overtopping will occur through a 66-ft spillway on the east side of the pond with an overflow depth of 0.45 feet. The top of berm elevation is at 4912.50 ft, providing 1-ft of freeboard over the spill depth. The 100-yr emergency spillway will flow into Lemay Avenue public ROW. Page 7 LOW IMPACT DEVELOPMENT The City of Fort Collins updated the Low Impact Development ordinance in 2016 (Ordinance No. 007, 2016) to require: · Treat at least 75% of any newly developed or redeveloped impervious area using one or a combination of LID techniques, or · Treat at least 50% of any newly developed or redeveloped impervious area using one or a combination of LID techniques when 25% of private driveable surfaces are permeable. To satisfy the required implementation of Low Impact Development (LID) techniques, Heartside Hill utilizes a bioretention pond/Rain Garden D1. Due to site constraints and the inability to treat the required amount of newly developed impervious area, the rain garden is designed to treat a portion of the newly developed impervious area along with the existing church impervious area. The rain garden is designed to treat the total drainage area being directed to the rain garden. The result is that the rain garden treats 105.9% of the impervious area required to be treated. The water quality capture volume provided within the rain garden (LID) is 3,802 cu-ft and the pond (standard WQCV) is 0.087 ac-ft. Below is a description of the 4-step process for selecting structural BMPs: Urban Drainage and Flood Control District (UDFCD) recommends a Four Step Process for receiving water protection that focuses on reducing runoff volumes, treating the water quality capture volume (WQCV), stabilizing drainageways and implementing long-term source controls. The Four Step Process applies to the management of smaller, frequently occurring events. Step 1: Employ Runoff Reduction Practices To reduce runoff peaks, volumes, and pollutant loads from urbanizing areas, implement Low Impact Development (LID) strategies, including Minimizing Directly Connected Impervious Areas (MDCIA). Captured runoff from strategic areas are routed through bioretention pond/rain gardens. Rain gardens will slow runoff, promote infiltration, and filter runoff prior to being released into the adjacent storm drain system. Step 2: Implement BMPs that Provide a Water Quality Capture Volume with Slow Release Page 8 The bioretention pond/rain gardens are designed to provide water quality capture volume per Urban Drainage’s recommendations and calculations. The captured runoff is designed for a 12- hr drain time. Step 3: Stabilize Drainageways Natural Drainageways are subject to bed and bank erosion due to increases in frequency, duration, rate and volume of runoff during and following development. Because the site will drain to an existing storm system, bank stabilization is unnecessary with this project. Step 4: Implement Site Specific and Other Source Control BMPs The proposed project will improve upon site specific source controls compared to historic conditions by providing localized trash enclosures within the development for disposal of solid waste; a rain garden for water treatment prior to flows entering storm systems; and additional water quality measures to protect and prolong the design life of BMPS delineated in Step 1. All calculations are attached for reference. Page 9 STORMWATER POLLUTION PREVENTION Erosion and sedimentation will be controlled on-site by use of sediment control logs, inlet protection, and gravel construction entrances. The measures are designed to limit the overall sediment yield increase due to construction as required by the City of Fort Collins. During overlot and final grading the soil will be roughened and furrowed perpendicular to the prevailing winds. During the performance of the work required by these specifications or any operations appurtenant thereto, whether on right-of-way provided by the City or elsewhere, the contractor shall furnish all labor, equipment, materials, and means required. The Contractor shall carry out proper efficient measures wherever and as necessary to reduce dust nuisance, and to prevent dust nuisance that has originated from his operations from damaging crops, orchards, cultivated fields, and dwellings, or causing nuisance to persons. The Contractor will be held liable for any damage resulting from dust originating from his operations under these specifications on right-of-way or elsewhere. It is unlawful to track or cause to be tracked mud or other debris onto public streets or rights- of-way. Wherever construction vehicles access routes or intersect paved public roads, previsions must be made to minimize the transport of sediment by runoff or vehicles tracking onto the paved surface. Stabilized construction entrances are required with base material consisting of 6” coarse aggregate. The contractor will be responsible for clearing mud tracked onto public streets on a daily basis. All temporary and permanent erosion and sediment control practices must be maintained and repaired as needed to assure continued performance of their intended function. Maintenance is the responsibility of the contractor. All disturbed areas must be seeded and mulched within 30 days of project start. Vegetation shall not be considered established until a ground cover is achieved which is demonstrated to be mature enough to control soil erosion to the satisfaction of the City Inspector and to survive severe weather condition. Page 10 CONCLUSIONS This Preliminary Drainage Report for Heartside Hill has been prepared to comply with the stormwater criteria set by the City of Fort Collins. The proposed drainage system will be designed to convey the developed peak 100-yr storm water runoff through the site to the proposed detention pond, and ultimately to the existing storm system. Drainage conveyance systems will be designed to convey drainage to the proposed roadways and collect onsite drainage and treat it in accordance with LID requirements before discharging it into the proposed detention pond. This preliminary drainage report anticipates the implementation of best management practices for erosion control, temporary and permanent, and on-site construction facilities. It can therefore be concluded that development of Heartside Hill will comply with the storm water jurisdictional criteria and the approved City of Fort Collins Stormwater Criteria Manual and will not adversely affect the adjacent properties, streets, storm drain system and/or detention/water quality facilities. Page 11 REFERENCES 1. Urban Storm Drainage Criteria Manual (Volumes 1, 2, and 3), Urban Drainage and Flood Control District, June 2001, Revised January 2016. 2. Fort Collins Stormwater Criteria Manual, Fort Collins Utilities, City of Fort Collins, Colorado, Dated December 2018, Adopted January 2019. 3. “Hydrologic Group Rating for Larimer County Area, Colorado”, USDA-Natural Resources Conservation Service, National Cooperative Soil Survey. Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov. [11/15/2021] 4. “Preliminary Geotechnical Subsurface Exploration Report, Proposed Residential Development Lots 1 and 2, Heart of the Rockies Second Subdivision”, prepared by Soilogic, LLC, Dated August 13, 2021. 5. “Drainage Investigation for Heart of the Rockies Christian Church”, prepared by Messner Engineering, Inc., Dated June 29, 1999. Page 12 APPENDIX Appendix A – Site Descriptions, Characteristics, & References Appendix B – Rational Calculations Appendix C – Low Impact Development Calculations Appendix D – Pond Calculations Appendix A APPENDIX A – SITE DESCRIPTIONS, CHARACTERISTICS, & REFERENCES SITE Vicinity Map Scale: 1" = 1000' PROJECT DATUM: NAVD88 CITY OF FORT COLLINS BENCHMARK #24-94 ON THE NORTHEAST CORNER OF THE INTERSECTION OF EAST TRILBY ROAD AND PORTNER DRIVE, ON TOP OF THE WEST END OF A CONCRETE HEADWALL ELEV= 4960.69 CITY OF FORT COLLINS BENCHMARK #25-94 ON THE NORTHWEST CORNER OF THE INTERSECTION OF EAST TRILBY ROAD AND SOUTH LEMAY AVENUE, ON TOP OF THE SOUTHEAST EDGE OF THE CONCRETE RING TO AN ELECTRIC MANHOLE ELEV= 4913.16 PLEASE NOTE: THIS PLAN SET IS USING NAVD88 FOR A VERTICAL DATUM. SURROUNDING DEVELOPMENTS HAVE USED NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) FOR THEIR VERTICAL DATUMS. IF NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) IS REQUIRED FOR ANY PURPOSE, THE FOLLOWING EQUATIONS SHOULD BE USED: NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) = 4960.69 (NAVD88 DATUM) - 3.19' NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) = 4913.16 (NAVD88 DATUM) - 3.19' E TRILBY RDS LEMAY AVEBRIT T A N Y S T AUTUMN RIDGE DRBRITTANY DRHEARTSIDE HILL Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 12/21/2021 Page 1 of 444826504482690448273044827704482810448285044828904482650448269044827304482770448281044828504482890494720494760494800494840494880494920494960495000495040495080495120 494720 494760 494800 494840 494880 494920 494960 495000 495040 495080 495120 40° 29' 48'' N 105° 3' 44'' W40° 29' 48'' N105° 3' 27'' W40° 29' 39'' N 105° 3' 44'' W40° 29' 39'' N 105° 3' 27'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 50 100 200 300 Feet 0 25 50 100 150 Meters Map Scale: 1:1,880 if printed on A landscape (11" x 8.5") 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 of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 16, Sep 2, 2021 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 11, 2018—Aug 12, 2018 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 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 12/21/2021 Page 2 of 4 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 63 Longmont clay, 0 to 3 percent slopes D 0.8 6.2% 90 Renohill clay loam, 3 to 9 percent slopes D 12.8 93.8% Totals for Area of Interest 13.6 100.0% 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. Rating Options Aggregation Method: Dominant Condition Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 12/21/2021 Page 3 of 4 Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 12/21/2021 Page 4 of 4 National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOOD HAZARD AREAS Without Base Flood Elevation (BFE) Zone A, V, A99 With BFE or DepthZone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mileZone X Future Conditions 1% Annual Chance Flood HazardZone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood HazardZone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 12/7/2021 at 10:59 AM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. 1:6,000 105°3'53"W 40°29'57"N 105°3'16"W 40°29'30"N Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020 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 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 9 Figure 3.4-1. Rainfall IDF Curve – Fort Collins Appendix B APPENDIX B – RATIONAL CALCULATIONS Design Engineer: Design Firm: Project Number: Date: % Impervious Runoff Coefficient C Return Period Frequency Adjustment Factor (Cf) 100% 0.95 2-year to 10-year 1.00 90% 0.95 100-year 1.25 90% 0.95 40% 0.50 0% 0.25 45% 0.55 70% 0.65 C2 to C10 C100 OS1 82,365 1.891 48,074 3,889 6,585 0 0 0 23,817 69.8% 0.75 0.93 D1 45,849 1.053 0 0 519 0 0 23,353 21,977 36.7% 0.46 0.58 D2 107,650 2.471 31,612 3,742 4,243 4,050 31,988 0 32,015 50.9% 0.61 0.76 OS1+D1+D2 235,864 5.415 79,686 7,631 11,347 4,050 31,988 23,353 77,809 54.7% 0.63 0.78 D3 32,721 0.751 0 10,921 1,485 0 0 0 20,315 34.1% 0.52 0.64 D4 47,548 1.092 0 13,981 467 0 0 0 33,100 27.3% 0.46 0.58 D5 18,328 0.421 17,629 0 183 0 0 0 516 97.1% 0.93 1.00 D4+D5 65,876 1.512 17,629 13,981 650 0 0 0 33,616 46.7% 0.59 0.74 D6 5,452 0.125 3,492 0 882 0 0 0 1,078 78.6% 0.81 1.00 D7 34,247 0.786 0 12,941 458 0 0 0 20,848 35.2% 0.52 0.65 D8 30,254 0.695 26,477 0 1,617 0 0 0 2,160 92.3% 0.90 1.00 D4+…+D7 71,328 1.637 21,121 13,981 1,532 0 0 0 34,694 49.2% 0.61 0.76 D9 61,908 1.421 7,517 1,040 103 0 9,405 0 43,843 20.6% 0.39 0.49 Total 466,322 10.705 134,801 46,514 16,542 4,050 41,393 23,353 199,669 48.9% 0.60 0.74 Heartside Hill DEVELOPED IMPERVIOUS AREA CALCULATION DESIGN CRITERIA: Fort Collins Stormwater Criteria Manual BASINS: Highland Development Services % Impervious values from Table 3.2.2 in the Fort Collins Stormwater Criteria Manual A. Bartel 20-1045-00 December 21, 2021 Land Use Paved Roof Walks Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual Gravel/Pavers Lawns (Heavy, 2-7% Slope) Sub-basin Designation Atotal (sq feet) Atotal (acres) Weighted % Impervious Habitat & L'arche Lots Community Center Lot COMPOSITEApaved (sq feet) Aroof (sq feet) Awalk (sq feet) Agravel/pavers (sq feet) Alawn (sq feet) AHabitat/L'Arche (sq feet) Acom. Center (sq feet) 21-1045-00 Rational Calcs (2021-12-21).xlsx Page 1 of 4 Highland Development Services Design Engineer: Design Firm: Project Number: Date: EQUATIONS: -Equation 5-3 -Equation 5-4 -Urbanized Check Equation 3.3-5 - CoFC Overland Flow CONSTRAINTS: 300 ft - Overland flow shall not exceed for developed condition 500 ft - Overland flow shall not exceed for undeveloped condition Final t c = minimum of t i + t t and urbanized basin check recommended minimum t c = 5 min for urbanized basins Time of Concentration (2-yr to 10-yr) OS1 OS1 69.8% 0.75 1.891 240 0.0381 6.53 330 0.0177 0.10 0.016 2.67 2.07 8.60 570 13.17 8.60 D1 D1 36.7% 0.46 1.053 225 0.0268 12.89 98 0.0834 0.10 0.030 3.09 0.53 13.42 323 11.79 11.79 D2 D2 50.9% 0.61 2.471 88 0.0413 5.39 506 0.0292 0.10 0.016 3.43 2.46 7.85 594 13.30 7.85 D3 D3 34.1% 0.52 0.751 36 0.0500 3.85 237 0.0625 0.10 0.030 2.68 1.48 5.33 274 11.52 5.33 D4 D4 27.3% 0.46 1.092 55 0.0278 6.28 388 0.0453 0.10 0.030 2.28 2.84 9.12 443 12.46 9.12 D5 D5 97.1% 0.93 0.421 90 0.0510 1.75 215 0.0428 0.10 0.016 4.15 0.86 5.00 306 11.70 5.00 D6 D6 78.6% 0.81 0.125 51 0.0654 2.06 20 0.0065 0.10 0.016 1.62 0.20 5.00 71 10.39 5.00 D7 D7 35.2% 0.52 0.786 44 0.0100 7.15 378 0.0407 0.10 0.016 4.05 1.56 8.70 422 12.34 8.70 D8 D8 92.3% 0.90 0.695 108 0.0549 2.20 388 0.0357 0.10 0.030 2.02 3.20 5.40 496 12.76 5.40 D9 D9 20.6% 0.39 1.421 101 0.0331 8.90 63 0.0109 0.10 0.016 2.09 0.50 9.40 164 10.91 9.40 December 21, 2021 Heartside Hill DEVELOPED TIME OF CONCENTRATION A. Bartel 21-1045-00 Highland Development Services LENGTH (ft) DESIGN CRITERIA: City of Fort Collins Stormwater Criteria Manual Overland Flow Equations for City of Fort Collins Stormwater Criteria Manual SUB-BASIN DATA INITIAL/OVERLAND TIME (ti)TRAVEL TIME (tt) tc=ti+tt (min) Urban Check Final tc (min)DESIGN POINT Sub-basin % Impervious C2-10 AREA (acres) tt (min) OVERALL LENGTH (ft/ft) tc (min) SLOPE (ft/ft) ti (min) LENGTH (ft) SLOPE (ft/ft) VELOCITY (ft/s) ROUGHNESS COEFFICIENT HYDRAULIC RADIUS (ft) ticttt+= V Ltt60 =1.871.1 10 180 +=LtcV.R2/3 S 1/2 21-1045-00 Rational Calcs (2021-12-21).xlsx Page 2 of 4 Highland Development Services Design Engineer: Design Firm: Project Number: Date: EQUATIONS: -Equation 5-3 -Equation 5-4 -Urbanized Check Equation 3.3-5 - CoFC Overland Flow CONSTRAINTS: 300 ft - Overland flow shall not exceed for developed condition 500 ft - Overland flow shall not exceed for undeveloped condition Final t c = minimum of t i + t t and urbanized basin check recommended minimum t c = 5 min for urbanized basins Time of Concentration (100-yr) OS1 OS1 69.8% 0.93 1.891 240 0.0381 3.07 330 0.0177 0.14 0.016 3.34 1.65 5.00 570 13.17 5.00 D1 D1 36.7% 0.58 1.053 225 0.0268 10.56 98 0.0834 0.14 0.030 3.87 0.42 10.98 323 11.79 10.98 D2 D2 50.9% 0.76 2.471 88 0.0413 3.74 506 0.0292 0.14 0.016 4.29 1.96 5.70 594 13.30 5.70 D3 D3 34.1% 0.64 0.751 36 0.0500 3.00 237 0.0625 0.14 0.030 3.35 1.18 5.00 274 11.52 5.00 D4 D4 27.3% 0.58 1.092 55 0.0278 5.14 388 0.0453 0.14 0.030 2.85 2.27 7.41 443 12.46 7.41 D5 D5 97.1% 1.00 0.421 90 0.0510 1.03 215 0.0428 0.14 0.016 5.19 0.69 5.00 306 11.70 5.00 D6 D6 78.6% 1.00 0.125 51 0.0654 0.72 20 0.0065 0.14 0.016 2.03 0.16 5.00 71 10.39 5.00 D7 D7 35.2% 0.65 0.786 44 0.0100 5.52 378 0.0407 0.14 0.016 5.06 1.24 6.77 422 12.34 6.77 D8 D8 92.3% 1.00 0.695 108 0.0549 1.10 388 0.0357 0.14 0.030 2.53 2.56 5.00 496 12.76 5.00 D9 D9 20.6% 0.49 1.421 101 0.0331 7.66 63 0.0109 0.14 0.016 2.62 0.40 8.06 164 10.91 8.06 December 21, 2021 Heartside Hill DEVELOPED TIME OF CONCENTRATION A. Bartel 21-1045-00 Highland Development Services LENGTH (ft) DESIGN CRITERIA: City of Fort Collins Stormwater Criteria Manual Overland Flow Equations for City of Fort Collins Stormwater Criteria Manual SUB-BASIN DATA INITIAL/OVERLAND TIME (ti)TRAVEL TIME (tt) tc=ti+tt (min) Urban Check Final tc (min)DESIGN POINT Sub-basin % Impervious C100 AREA (acres) tt (min) OVERALL LENGTH (ft/ft) tc (min) SLOPE (ft/ft) ti (min) LENGTH (ft) SLOPE (ft/ft) VELOCITY (ft/s) HYDRAULIC RADIUS (ft) ROUGHNESS COEFFICIENT ticttt+= V Ltt60 =1.871.1 10 180 +=LtcV.R2/3 S 1/2 21-1045-00 Rational Calcs (2021-12-21).xlsx Page 3 of 4 Highland Development Services Design Engineer: Design Firm: Project Number: Date: EQUATIONS:I = rainfall intensity (in/hr) Q n = n -yr peak discharge (cfs)P 1 = one-hour point rainfall depth (in) C n = n -yr runoff coefficient t c = time of concentration (min) I n = n -yr rainfall intensity (in/hr) P 1-2yr =0.82 in A n = Basin drainage area (ac)P 1-10yr =1.40 in P 1-100yr =2.86 in BASIN SUMMARY: tc (min)Runoff Coeff (C2-10)C(A) (acres)Intensity (in/hr)Q (ft3/s)tc (min)Runoff Coeff (C2-10)C(A) (acres)Intensity (in/hr)Q (ft3/s)tc (min)Runoff Coeff. (C100)C(A) (acres)Intensity (in/hr)Q (ft3/s) OS1 OS1 1.891 69.8% 8.60 0.75 1.41 2.34 3.31 8.60 0.75 1.41 4.00 5.66 5.00 0.93 1.77 9.95 17.58 D1 D1 1.053 36.7% 11.79 0.46 0.49 2.07 1.01 11.79 0.46 0.49 3.53 1.72 10.98 0.58 0.61 7.44 4.52 D2 D2 2.471 50.9% 7.85 0.61 1.50 2.42 3.63 7.85 0.61 1.50 4.13 6.19 5.70 0.76 1.87 9.34 17.49 D3 D3 0.751 34.1% 5.33 0.52 0.39 2.73 1.06 5.33 0.52 0.39 4.66 1.80 5.00 0.64 0.48 9.95 4.82 D4 D4 1.092 27.3% 9.12 0.46 0.51 2.29 1.16 9.12 0.46 0.51 3.92 1.98 7.41 0.58 0.63 8.61 5.44 D5 D5 0.421 97.1% 5.00 0.93 0.39 2.85 1.12 5.00 0.93 0.39 4.87 1.91 5.00 1.00 0.42 9.95 4.19 D6 D6 0.125 78.6% 5.00 0.81 0.10 2.85 0.29 5.00 0.81 0.10 4.87 0.49 5.00 1.00 0.13 9.95 1.25 D7 D7 0.786 35.2% 8.70 0.52 0.41 2.33 0.96 8.70 0.52 0.41 3.98 1.64 6.77 0.65 0.51 8.87 4.57 D8 D8 0.695 92.3% 5.40 0.90 0.63 2.72 1.70 5.40 0.90 0.63 4.64 2.90 5.00 1.00 0.69 9.95 6.91 D9 D9 1.421 20.6% 9.40 0.39 0.56 2.27 1.27 9.40 0.39 0.56 3.87 2.17 8.06 0.49 0.70 8.37 5.85 10-yr Peak Runoff 100-yr Peak Runoff Heartside Hill DEVELOPED PEAK RUNOFF DESIGN CRITERIA: Design Point Sub-basin Area (acres) A. Bartel Highland Development Services 21-1045-00 December 21, 2021 2-yr Peak Runoff City of Fort Collins Stormwater Criteria Manual % Impervious nnnnAICQ=(0.786651) 1 )10( 5.28 ct PI + = 21-1045-00 Rational Calcs (2021-12-21).xlsx Page 4 of 4 Highland Development Services Appendix C APPENDIX C – LOW IMPACT DEVELOPMENT CALCULATIONS Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA Low Impact Development Summary Sq-Ft Acres Impervious Area (sq-ft) % of Impervious Area Requiring Treatment Impervious Area Requiring Treatment 105,661 2.43 63,509 0% 0 363,964 8.36 178,480 75% 133,860 443,462 10.78 241,989 - 133,860 LID Facility Contributing Basins Area Drainage to LID (sq-ft) % Impervious Impervious Area Treated (sq-ft) WQCV12-hr (watershed inches) WQCV12-hr (cu-ft) Treatment Method D1 OS1+D1+D2+D3 268,585 52.2% 141,812 0.17 3,802 Rain Garden EDB Pond Contributing Basins Drainage Area (sq-ft) Drainage Area (acre)% Impervious WQCV40-hr (watershed inches) WQCV40-hr (ac-ft) Pond D D4+…+D9 197,737 4.539 44.4% 0.19 0.087 133,860 141,812 105.9% Area (sq-ft) Area (acres) Treatment Ratio 268,585 6.17 57.2% 197,737 4.54 42.1% 3,303 0.08 0.7% 469,625 10.78 December 21, 2021 Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016) Heartside Hill Low Impact Development J.Claeys Highland Development Services 21-1045-00 Total Improvement Area Water Quality Area Treatment Summary Description Total Area Treated by LID Total Area Treated by EDB Total Area Not Treated Total % Treatment Development Area Breakdown City of Fort Collins - Ordinance No. 007, 2016 - Treat at least 75% of any newly developed or redeveloped impervious area using one or a combination of LID techniques, or - Treat at least 50% of any newly developed or redeveloped impervious area using one or a combination of LID techniques when 25% of private driveable surfaces are permeable. Total Impervious Area Treated (sq-ft) Total Impervious Area Required for LID Treatment (sq-ft) LID Treatment Summary LID Treatment Areas Totals Standard Water Quality Areas Description Existing Church Site Proposed Site Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =52.2 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.522 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.17 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 268,585 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 =0.43 in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER =3,802 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 =12 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 =2804 sq ft D) Actual Flat Surface Area AActual =sq ft E) Area at Design Depth (Top Surface Area)ATop =sq ft F) Rain Garden Total Volume VT=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 =ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =cu ft iii) Orifice Diameter, 3/8" Minimum DO = in Design Procedure Form: Rain Garden (RG) A. Bartel Highland Development Services December 22, 2021 Heartside Hill Fort Collins, CO UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO UD-BMP_v3.07.xlsm, RG 12/22/2021, 10:22 AM 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) A. Bartel Highland Development Services December 22, 2021 Heartside Hill Fort Collins, CO 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.xlsm, RG 12/22/2021, 10:22 AM Appendix D APPENDIX D – POND CALCULATIONS Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA 0.59 1.25 0.74 ft3 acre-ft 10.700 acres 40,661 0.93 13.20 cfs Time (min) 100-yr Intensity (I , in/hr) Q100 (cfs) Accumulative Runoff Volume (ft3) Release Volume (ft3) Detained Volume (ft3) Detained Volume (acre-ft) 0 0.00 0.00 0 0 0 0.00 5 9.95 78.78 23,635 3,960 19,675 0.45 10 7.72 61.13 36,676 7,920 28,756 0.66 15 6.52 51.63 46,463 11,880 34,583 0.79 20 5.60 44.34 53,209 15,840 37,369 0.86 25 4.98 39.43 59,147 19,800 39,347 0.90 30 4.52 35.79 64,421 23,760 40,661 0.93 35 4.08 32.31 67,841 27,720 40,121 0.92 40 3.74 29.61 71,072 31,680 39,392 0.90 45 3.46 27.40 73,970 35,640 38,330 0.88 50 3.23 25.58 76,725 39,600 37,125 0.85 55 3.03 23.99 79,172 43,560 35,612 0.82 60 2.86 22.65 81,524 47,520 34,004 0.78 65 2.72 21.54 83,994 51,480 32,514 0.75 70 2.59 20.51 86,132 55,440 30,692 0.70 75 2.48 19.64 88,365 59,400 28,965 0.66 80 2.38 18.84 90,455 63,360 27,095 0.62 85 2.29 18.13 92,474 67,320 25,154 0.58 90 2.21 17.50 94,493 71,280 23,213 0.53 95 2.13 16.87 96,132 75,240 20,892 0.48 100 2.06 16.31 97,866 79,200 18,666 0.43 105 2.00 15.84 99,767 83,160 16,607 0.38 110 1.94 15.36 101,382 87,120 14,262 0.33 115 1.89 14.97 103,259 91,080 12,179 0.28 120 1.84 14.57 104,898 95,040 9,858 0.23 Area (A ) Allowed Release Rate Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual City of Fort Collins - Storm Water Criteria Manual Runoff Coefficient (C ) Frequency Factor (C f )Required Detention Adjusted Runoff Coefficient (CC f ) Detention Volume Calculation - Pond D Heartside Hill 100-yr Detention Volume - FAA Method Highland Development Services December 21, 2021 21-1045-00 J.Claeys Heartside Hill Critical Pond Elevations Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised January 2016) Stage Storage Volume (pond volume calculated using the prismoidal formula): CONTOUR (FT)AREA (FT2)AREA (ACRE)VOLUME (ACRE-FT)DEPTH (FT)CUMULATIVE VOLUME (ACRE-FT) 4907.70 0 0.000 0.000 0.00 0.000 4908.0 775 0.018 0.002 0.30 0.002 4909.0 9774 0.224 0.102 1.30 0.104 4910.0 20152 0.463 0.336 2.30 0.440 4911.0 26826 0.616 0.537 3.30 0.977 4912.0 39536 0.908 0.757 4.30 1.734 0.087 4908.84 ft 1.017 4911.05 ft A. Bartel Highland Development 21-1045-00 Acre-Ft Interpolates to an Elev. of Required 100-yr Detention Volume (including WQCV) = December 21, 2021 Required Water Quality Capture Volume (WQCV) = Acre-Ft Interpolates to an Elev. of () 3 2121 DepthAAAAV++= 21-1045-00 PondCalcs.xls - Pond Stage Storage Page 1 of 1 Highland Development Services Heartside Hill Emergency Overflow Spillway Calculations Design Engineer: Design Firm: Project Number: Date: Broad-Crested Weir Equation-Trapezoidal Shape where:Q = Discharge (cfs) C = Weir Coeffecient L = Weir Length (ft) H = Average Weir Head (ft) H:V =Side Slope Calculations Knowns:4.00 0.45 ft 2.6 4911.05 ft 53.7 cfs 66.62 ft 67 ft 1.00 ft 1.45 ft 4912.50 ftTop of Berm Elevation 100-yr Pond Inflow Calculated Spillway Use Spillway Length Total Spillway Depth Spillway Freeboard Side Slopes (H:V) Desired Spillway Head Weir Coefficient Spillway Elevation A. Bartel Highland Development Services 21-1045-00 December 21, 2021 2 5 2 3 H V HCCLHQ   += 21-1045-00 PondCalcs.xls - Spillway Page 1 of 1 Highland Development Services