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SEVEN GENERATIONS MULTIFAMILY - FDP230008 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT
FINAL DRAINAGE REPORT FOR Seven Generations Multifamily Prepared by: Highland Development Services 6355 Fairgrounds Ave, Suite 100 Windsor, Colorado 80550 Phone: 970.674.7550 Prepared for: Black Timber Builders 417 Jefferson Street Fort Collins, CO 80524 Office: 970.657.2399 March 1, 2023 Job Number 22-1057-00 Highland Development Services, Inc. 6355 Fairgrounds Avenue, Suite 100 | Windsor, CO 80550 | 970.674.7550 March 1, 2023 Fort Collins Utilities – Stormwater Department 700 Wood Street Fort Collins, CO 80522 RE: Final Drainage Report for Heartside Hill Fort Collins Stormwater Department, We are pleased to submit for your review, the Final Drainage Report for the redevelopment project Seven Generations Multifamily 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 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 .................................................................................................................. 5 Drainage Conveyance Design ...................................................................................................... 5 Detention/Water Quality Pond Design ....................................................................................... 5 Low Impact Development ............................................................................................................... 6 Stormwater Pollution Prevention ................................................................................................... 8 Conclusions ..................................................................................................................................... 9 References .................................................................................................................................... 10 Appendix ....................................................................................................................................... 11 Appendix A – Site Descriptions, Characteristics, & References .................................................. A Appendix B – Rational Calculations ............................................................................................. B Appendix C – Low Impact Development Calculations ................................................................. C Appendix D – Capacity Calculations ............................................................................................ D Page ii ENGINEER CERTIFICATION I hereby certify that this report (plan) for the final drainage design of Seven Generations Multifamily 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 30, Township 7 North, Range 68 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, in the State of Colorado. The property consists of Lot 2 and the south 85 feet of the west 410 feet of Lot 4 of the New Hampshire Subdivision, west of the intersection of Vermont Drive and Eastbrook Drive. It is bounded by open space owned by the City of Fort Collins to the north, Eastbrook Drive to the east, commercial development to the south, and the Union Pacific Railroad to the west. The site was previously developed as commercial office spaces with one building, the parking lot, and all of the utility infrastructure currently constructed. The total site, including the existing improvements and commercial office building is approximately 3.64 acres. The area of proposed redevelopment, approximately 1.28 acres, is currently unimproved and was originally approved with the Seven Generation Office Park for two additional commercial office buildings and plaza space. The Seven Generations Multifamily proposes to redevelop this area with the construction of a single 75-unit multifamily building and supporting access and plaza spaces. The existing infrastructure, parking and utilities, is to generally be protected in place and utilized to support the proposed redevelopment. The project site generally slopes from the southeast to the northwest at approximately 2% toward an existing water quality pond in the northwest corner of the property. The water quality pond was designed and constructed to support the previous commercial office development and is well established with vegetation. The intent is to protect the existing water quality pond and be utilized to provide water quality enhancement for the existing improvements. No wetlands are located within the area of proposed redevelopment. The project site is not located within the FEMA floodway or floodplain and is within the non- printed FEMA FIRM panel 08069C1000F, effective 12/19/2006. The site is within the City of Fort Collins Foothill Master Drainage Basin and the City 100-yr floodplain is located along the west and north sides of the property. The redevelopment area is outside of the City’s 100-yr floodplain. Due to the vicinity of the site to this floodplain, timing of the peak runoff, and proposed impervious area, on site detention was not required per the approval of the Seven Generations Office Park. The proposed redevelopment includes a single 75-unit multifamily building and plaza space that will provide the required emergency access. The existing improvements will generally be Page 2 protected in place and will provide the required parking, utility services, and standard water quality. A filtration gallery is proposed to provide additional stormwater quality enhancement and is intended to satisfy the low impact development (LID) requirement. The site was previously analyzed within the “Final Drainage and Erosion Control Report for Seven Generations Office,” prepared by Interwest Consulting Group, revised October 12, 2006. SITE SOILS The Seven Generations Multifamily redevelopment project site consists primarily of Nunn clay loam and a small portion of Fort Collins loam both classified as Type C hydrologic group. According to USDA/Natural Resource Conservation Group, Type C soils a have 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 also have a slow rate of water transmission. Per the “Preliminary Subsurface Exploration Report, 3400 Eastbrook Drive, Fort Collins, Colorado,” prepared by Earth Engineering Consultants, Inc. dated March 2, 2006: “A thin mantle of topsoil/vegetation was encountered at the surface at boring locations. The topsoil/vegetation was underlain by clayey sand and in boring B-1 and sandy lean clay in borings B-2 and B-3. The clayey sand and sandy lean clay showed low swell potential in laboratory testing at present moisture and density. The essentially granular soils extended to the bottom of borings B-1 while moderately cohesive soils extended to depths of approximately 14 and 8 ft, respectively, in borings B-2 and B-3. The lean clay soils in boring B-2 and B-3 were underlain in poorly graded sand and gravel. The granular soils were loose to medium dense with cobbles observed with depth. The sand and gravel extended to the bottom of the borings at depths of approximately 15 feet below present site grades.” Groundwater was also observed during the subsurface soil exploration: “Observations were made while drilling and after completion of the borings to detect the presence and depth to the hydrostatic groundwater table. At the time of drilling, no free groundwater was observed in the test borings.” 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. The proposed redevelopment rational calculations are compared to the pervious rational calculations to review the impacts of this proposal. HYDRAULIC CRITERIA The existing storm drainage system was analyzed to confirm conveyance capacity of the minor 10-yr event. The major 100-yr storm event is conveyed 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 capacity was confirmed utilizing the manufacturer capacity charts. 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 Seven Generations Multifamily drainage basins are delineated by areas draining through the site and also in reference to previous basin delineation for comparison and review of impacts. The site is divided into 4 main drainage basins: Drainage Basin 1A: Drainage Basin 1A is approximately 0.35 acres and 65.1% impervious. This basin consists of the existing commercial office building and the adjacent existing landscape and walks. Runoff is conveyed via existing storm drains to the existing water quality pond. Drainage Basin 1B: Drainage Basin 1A is approximately 0.98 acres and 77.6% impervious. This basin consists of most of the redevelopment area. Runoff is conveyed to the Filtration Gallery and to the existing water quality pond. Drainage Basins 1A & 1B combined correlate to the previous Basin 1 of the Seven Generations Office drainage study. Combined these basins are 1.33 acres and 74.4% impervious. This is an increase in area of approximately 0.32 acres and increase of approximately 6% impervious. There is an increase in runoff rates and the proposed Filtration Gallery offsets with impacts to the existing water quality pond. Drainage Basin 2: Drainage Basin 2 is approximately 1.72 acres and 71.1% impervious. This basin consists of the existing parking area, existing water quality pond, and the areas adjacent to the south/west/north sides of the proposed multifamily building. Runoff is conveyed via surface curb and pans to the existing water quality pond. Majority of the existing and proposed redevelopment improvements are contained within Basins 1A, 1B, and 2. Combined these basins are 3.05 acres and 72.5% impervious. Relating back to the previous Seven Generations Office drainage study, this is a decrease in area of approximately 0.12 acres and increase of approximately 6% impervious. There is a slight increase in runoff rates that may be considered negligible. Drainage Basin 3: Drainage Basin 3 is approximately 0.83 acres and 32.8% impervious. This basin consists of the existing west half of Eastbrook Drive, and open space to the north and west. Runoff is conveyed offsite via curbs and overland surface flows. Comparing the combination of all the drainage basins, there is an increase in 3% impervious area. Page 5 DRAINAGE FACILITY DESIGN DRAINAGE CONVEYANCE DESIGN The existing storm infrastructure to convey runoff includes swales, inlets, and storm drain pipes. Stormwater water quality enhancement is achieved through the use of the existing water quality pond and the proposed Filtration Gallery. DETENTION/WATER QUALITY POND DESIGN The existing water quality pond is intended to be protected with this proposed redevelopment project and utilized to provide water quality enhancement for the existing improvements. Similar to the previously approved Seven Generations Office project, this project is proposing to provide water quality only with no detention with the following justifications: - This site peaks at approximately 8.2 minutes, and the peak flow within the Foothills Master Drainage Basin channel is over 3 hours. Runoff from this site does not contribute to the peak flow (detained or undetained.) The increase of impervious with this redevelopment proposal is not significant enough to invalidate the previous detention waiver justification. City Stormwater has confirmed the precious detention waiver for the site plan and will allow it to remain for the current project. Below is a summary of the proposed change in impervious area: 1 1.01 68%1A+1B 1.33 74% 0.32 6% 2 2.15 67%2 1.72 71% -0.43 4% 1+2 3.17 67% 1A+1B+2 3.05 73% -0.12 6% 3 0.71 35%3 0.83 33% 0.12 -2% Totals 3.88 61%Totals 3.88 64% 0.00 3% Previous ComparisonRedeveloped Area (acres) % Impervious Area (acres) % Impervious Seven Generations Office Park Basins Area (acres) % Impervious Seven Generations Multifamily Basins Page 6 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, Seven Generations Multifamily proposes to utilize a Filtration Gallery to provide water quality enhancement of the redevelopment area. The impervious area treated by the proposed Filtration Gallery will exceed the required area of treatment. Below is the Low Impact Development Summary for reference: 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 Page 7 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 the filtration gallery. Filtration galleries 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 The filtration gallery is designed to provide water quality capture volume per the City of Fort Collins recommendations and supporting calculations. 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 implement site specific source controls by managing the existing localized trash enclosures within the development for disposal of solid waste; a filtration gallery 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 8 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 conditions. Page 9 CONCLUSIONS This Final Drainage Report for Seven Generations Multifamily 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, and ultimately to the existing drainage features. 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 to the existing water quality pond and offsite. 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 Seven Generations Multifamily complies 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 10 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. [9/6/2022] 4. “Preliminary Subsurface Exploration Report, 3400 Eastbrook Drive, Fort Collins, Colorado,” prepared by Earth Engineering Consultants, Inc. dated March 2, 2006. 5. “Final Drainage and Erosion Control Report for Seven Generations Office,” prepared by Interwest Consulting Group, revised October 12, 2006. Page 11 APPENDIX Appendix A – Site Descriptions, Characteristics, & References Appendix B – Rational Calculations Appendix C – Low Impact Development Calculations Appendix D – Capacity Calculations Appendix A APPENDIX A – SITE DESCRIPTIONS, CHARACTERISTICS, & REFERENCES SITE E. DRAKE RD UNION PACIFIC RAILROADS. TIMBERLINE RDE. HORSETOOTH RDS. LEMAYAVEVicinity Map Scale: 1" = 1000' PROJECT DATUM: NAVD88 CITY OF FORT COLLINS BENCHMARK #43-01 EAST SIDE OF TIMBERLINE ROAD, AT THE SOUTH ENTRANCE TO C.S.U. RIGDEN FARM, ON THE NORTH END OF THE HEAD WALL OF A STORM DITCH ELEV= 4937.02 CITY OF FORT COLLINS BENCHMARK #12-93 NORTHWEST CORNER OF HORSETOOTH ROAD AND TIMBERLINE ROAD, ON A SIGNAL POLE BASE ELEV= 4957.08 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) = 4937.02 (NAVD88 DATUM) - 3.18' NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) = 4957.08 (NAVD88 DATUM) - 3.19' Hydrologic Soil Group—Larimer County Area, Colorado (Seven Generations) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/6/2022 Page 1 of 44487940448796044879804488000448802044880404488060448808044879404487960448798044880004488020448804044880604488080496300496320496340496360496380496400496420496440496460496480496500496520 496300 496320 496340 496360 496380 496400 496420 496440 496460 496480 496500 496520 40° 32' 36'' N 105° 2' 37'' W40° 32' 36'' N105° 2' 27'' W40° 32' 31'' N 105° 2' 37'' W40° 32' 31'' N 105° 2' 27'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 45 90 180 270 Feet 0 10 20 40 60 Meters Map Scale: 1:1,010 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: Jul 2, 2021—Aug 25, 2021 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 (Seven Generations) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/6/2022 Page 2 of 4 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 36 Fort Collins loam, 3 to 5 percent slopes C 0.2 4.8% 74 Nunn clay loam, 1 to 3 percent slopes C 3.7 79.0% 76 Nunn clay loam, wet, 1 to 3 percent slopes C 0.8 16.2% Totals for Area of Interest 4.6 100.0% 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. Hydrologic Soil Group—Larimer County Area, Colorado Seven Generations Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/6/2022 Page 3 of 4 Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado Seven Generations Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/6/2022 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 9/12/2022 at 7:11 PM 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°2'51"W 40°32'48"N 105°2'14"W 40°32'20"N Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020 2,257 376.2 Seven Generations Multifamily This map is a user generated static output from the City of Fort Collins FCMaps Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. City of Fort Collins - GIS 286.0 1: WGS_1984_Web_Mercator_Auxiliary_Sphere Feet286.00143.00 Notes Legend 1,715 FEMA Floodplain FEMA High Risk - Floodway FEMA High Risk - 100 Year FEMA Moderate Risk - 100 / 500 Year City Floodplains City High Risk - Floodway City High Risk - 100 Year City Moderate Risk - 100 Year City Limits NearMap Logo 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 FOOTHILLS BASIN HYDROLOGY UPDATE AND ALTERNATIVE ANALYSIS AT DRAKE RD. AND LEMAY AVE. Prepared by: Prepared for: Enginuity Engineering Solutions, LLC (Enginuity) City of Fort Collins – Utility Department 10106 W. San Juan Way, Ste 215 700 Wood St. Littleton, CO 80127 Fort Collins, CO 80522 February 2020 FOOTHILLS BASINS UPDATE SUB624 SUB621 SUB64 SUB63 SUB650 SUB58SUB59 SUB584 SUB53 SUB57 SUB55 SUB47 SUB56 SUB54SUB48 SUB46 SUB671SUB66 SUB67 SUB581 SUB583SUB582 SUB68 SUB691 SUB69 SUB681 SUB682 SUB651 SUB622 SUB61 SUB60 SUB52 SUB150 SUB50 SUB51 SUB49 SUB45 SUB144 SUB44 SUB40 SUB142 SUB43 SUB37 SUB39SUB38 SUB26 SUB29 SUB30 SUB28 SUB36 SUB33 SUB35 SUB34 SUB25N SUB24 SUB22 SUB15 SUB19 SUB17 SUB14 SUB16 SUB12 SUB11SUB8SUB7SUB6 SUB10 SUB105 SUB5 SUB4 SUB78 SUB75 SUB2 SUB3 SUB31 SUB70SUB71 SUB18 SUB27 SUB65 SUB623 SUB32 SUB252 SUB255 SUB249 SUB251 SUB250 SUB248 SUB254 SUB253 SUB243 SUB240 SUB241 SUB242 SUB247 SUB246 SUB244 SUB245 SUB25S Esri, HERE, Garmin, (c) OpenStreetMap contributors, and the GIS user community, Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community 0 0.5 10.3 Miles ¹ Foothills Impervious Update Difference in Impervious (Updated - MODSWMM) ≤-30 ≤-15 ≤-5 ≤5 ≤15 ≤40 Development_Change_Areas DRAKE RD.COLLEGE RD.LEMAY AVE. This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Apr-12-2022 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA Appendix B APPENDIX B – RATIONAL CALCULATIONS NYLOPLAST DUCTILE IRONDO NOT POLLUTE DRAINS TO WATERWAYS NYLOPLAST DUCTILE IRON DO NOT POLLUTE DRAINS TO WATERWAYS NYLOPLAST DUCTILE IRON DO NOT POLLUTE DRAINS TO WATERWAYS 100-YR FP 100-YR FP100-YR FPVERMONT DRIVE (54' ROW)EASTBROOK DRIVE(54' ROW)LOT 1 NEW HAMPSHIRE SUBDIVISION EXISTING COMMERCIAL BUILDING FFE = 4950.70 SEVEN GENERATIONS MULTIFAMILY BUILDING FFE = 4952.25UNION PACIFIC RAILROADTRACT A TIMBERLINE VILLAGE PUD (City of Fort Collins) (U&DE) APPROX LIMITS OF REDEVELOPMENT AREA & DISTURBED AREA 56,500± SQFT (1.30± ACRES) FILTRATION GALLERY 48~SC-160LP STORMTECH CHAMBERS EXISTING STANDARD WATER QUALITY POND EX TRASH ENCLOSURE (MODIFIED)REVISIONNO.BYDATEHIGHLANDDEVELOPMENT SERVICES6355 FAIRGROUNDS AVENUE, SUITE 100 | WINDSOR, CO 80550PHONE: 970.674.7550 | EMAIL: Info@Highland-DS.com | www.Highland-DS.comPREPARED BY OR UNDER THE DIRECT SUPERVISION OF: FOR AND ON BEHALF OF HIGHLAND DEVELOPMENT SERVICES REVIEW SET NOT FOR CONSTRUCTION OFSHEET DRAWN BY CHECKED BY DATE SCALE (H) HDS PROJECT # SCALE (V)SEVEN GENERATIONS MULTIFAMILYDRAINAGE & EROSION CONTROL PLAN3/1/23 1" = 20' N/A JTC JTC 22-1057-00 C2.00 4 9 CALL UTILITY NOTIFICATION CENTER OF COLORADO CALL 2-BUSINESS DAYS IN ADVANCE BEFORE YOU DIG, GRADE OR EXCAVATE FOR THE MARKING OF UNDERGROUND MEMBER UTILITIES. before you dig.CallKnow what's below. R N W E S 0 SCALE: 1" = 20' 40201020 BASIN COEFFICIENT (100-YR) BASIN DESIGNATION BASIN AREA DESIGN POINT DRAINAGE FLOW ARROW DRAINAGE BASIN BOUNDARY DRAINAGE BASIN FLOW PATH LEGEND EXISTING MAJOR CONTOUR EXISTING MINOR CONTOUR PROPOSED MAJOR CONTOUR PROPOSED MINOR CONTOUR ROCK SOCK INLET PROTECTION SEDIMENT CONTROL LOG CONCRETE WASHOUT AREA NOTES 1.THE NATURAL HABITAT BUFFER ZONE (NHBZ) IS INTENDED TO BE MAINTAINED IN A NATIVE LANDSCAPE. PLEASE SEE SECTION 3.4.1 OF THE LAND USE CODE FOR ALLOWABLE USES WITHIN THE NATURAL HABITAT BUFFER ZONE. 2.CONTRACTOR TO PROVIDE AND MAINTAIN ALL NECESSARY EROSION CONTROL MEASURES PRIOR TO AND THROUGHOUT CONSTRUCTION. PLACE EROSION CONTROL PROTECTION AT ALL EXISTING INLETS DOWNSTREAM FROM THE CONSTRUCTION AREA. EROSION CONTROL PROTECTION SHALL REMAIN IN PLACE UNTIL CONSTRUCTION IS COMPLETE AND ALL DISTURBED GROUND IS ADEQUATELY VEGETATED WITH OWNER'S APPROVAL FOR REMOVAL. 3.THE EXTENT OF EROSION CONTROL PROTECTION SHALL BE OBSERVED AND ADJUSTED AS NEEDED DURING CONSTRUCTION BASED ON SITE CONDITIONS AND THE PERFORMANCE OF THE EROSION CONTROL CONTROL MEASURES SHOWN, TO SUPPLY SUFFICIENT EROSION CONTROL AND MINIMIZE DOWNSTREAM WATERWAY POLLUTION. 4.LIMIT DISTURBANCE TO AREAS WITHIN EROSION CONTROL BOUNDARIES. ADJUST EROSION CONTROL BOUNDARIES AS NECESSARY TO ADEQUATELY COMPLETE PROPOSED WORK. ALL DISTURBED AREAS SHALL BE PREPARED (SEEDED & MULCHED, SURFACE ROUGHENING, ETC.) TO MINIMIZE EROSION POTENTIAL AND SOIL MIGRATION. 5.STORMWATER MANAGEMENT PLAN SHALL BE PREPARED AND SUBMITTED BY CONTRACTOR PRIOR TO CONSTRUCTION COMMENCEMENT. 6.SEE LANDSCAPE PLAN FOR REVEGETATION METHODS AND DETAILS. DURING CONSTRUCTION, ANY SOIL DISTURBED AND NOT UNDER ACTIVE CONSTRUCTION SHALL BE SEEDED AND MULCHED PER CITY STANDARDS. 7.ANY DISTURBED LAND MUST RECEIVE SURFACE ROUGHENING, INCLUDING BUT NOT LIMITED TO SLOPED AREAS. 8.NO VEHICULAR TRAFFIC IS ANTICIPATED IN/OUT OF THE REDEVELOPMENT AREA DURING CONSTRUCTION. ALL CONSTRUCTION VEHICLES ARE TO STAGE WITHIN THE EXISTING SITE PARKING LOT. 9.REFERENCE SEVEN GENERATIONS MULTIFAMILY DRAINAGE REPORT. 10.REFERENCE SHEET 7 FOR EROSION CONTROL DETAILS. Design Engineer: Design Firm: Project Number: Date: DRAINAGE SUMMARY: Q2 (ft3/s) Q10 (ft3/s) Q100 (ft3/s) Q2 (ft3/s) Q10 (ft3/s) Q100 (ft3/s) Q2 (ft3/s) Q10 (ft3/s) Q100 (ft3/s) 1 1.01 68% 2.2 3.7 9.6 1A+1B 1.33 74% 2.7 4.6 13.2 0.32 6% 0.5 0.9 3.6 2 2.15 67% 3.5 6.0 16.4 2 1.72 71% 2.8 4.7 13.1 -0.43 4% -0.7 -1.3 -3.3 1+2 3.17 67%5.1 8.9 24.6 1A+1B+2 3.05 73%5.2 8.9 24.8 -0.12 6%0.1 0.0 0.2 3 0.71 35%0.9 1.5 3.9 3 0.83 33%0.8 1.4 3.7 0.12 -2%-0.1 -0.1 -0.2 Totals 3.88 61%Totals 3.88 64%0.00 3% J.Claeys Highland Development Services, Inc. 22-1057-00 September 13, 2022 Seven Generations Multifamily DRAINAGE SUMMARY Peak Runoff Comparison Seven Generations Multifamily Basins Area (acres) % Imprevious Area (acres) % Imprevious Previous Redeveloped Peak Runoff Peak RunoffSeven Generations Office Park Basins Area (acres) % Imprevious 22-1057-00 Rational Calcs.xlsx Page 1 of 5 Interwest Consulting Group 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% 0.20 C2 to C10 C100 1A 15,031 0.35 0 10,034 845 0 4,152 65.1% 0.74 0.93 1B 42,894 0.98 8,146 27,640 312 0 6,797 77.6% 0.83 1.00 1A+1B 57,925 1.33 8,146 37,674 1,157 0 10,948 74.4% 0.81 1.00 2 74,920 1.72 52,663 0 687 0 21,571 71.1% 0.73 0.92 1A+1B+2 132,846 3.05 60,809 37,674 1,844 0 32,519 72.5% 0.77 0.96 3 35,984 0.83 10,907 0 980 0 24,097 32.8% 0.45 0.56 Total 168,830 3.88 71,716 37,674 2,823 0 56,617 64.1% 0.70 0.87 COMPOSITEApaved (sq feet) Aroof (sq feet) Awalk (sq feet) Alawn (sq feet) Agravel/pavers (sq feet) Lawns (Flat, < 2% Slope) Sub-basin Designation Atotal (sq feet) Atotal (acres) Weighted % Impervious Gravel/Pavers Paved Roof Walks Land Use Seven Generations Multifamily DEVELOPED IMPERVIOUS AREA CALCULATION DESIGN CRITERIA: Fort Collins Stormwater Criteria Manual BASINS: Highland Development Services, Inc. Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual % Impervious values from Table 3.2.2 in the Fort Collins Stormwater Criteria Manual J.Claeys 22-1057-00 September 13, 2022 22-1057-00 Rational Calcs.xlsx Page 2 of 5 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) 1A 1A 65.1% 0.74 0.35 63 0.0200 4.20 159 0.0070 0.10 0.016 1.68 1.58 5.78 222 11.23 5.78 1B 1B 77.6% 0.83 0.98 103 0.0200 4.04 234 0.0050 0.10 0.016 1.42 2.75 6.79 337 11.87 6.79 1A+1B 1A+1B 74.4% 0.81 1.33 103 0.0200 4.39 234 0.0050 0.10 0.016 1.42 2.75 7.14 337 11.87 7.14 2 2 71.1% 0.73 1.72 55 0.0200 4.04 599 0.0065 0.10 0.016 1.62 6.17 10.21 654 13.63 10.21 2 1A+1B+2 72.5% 0.77 3.05 55 0.0200 3.68 599 0.0065 0.10 0.016 1.62 6.17 9.86 654 13.63 9.86 3 3 32.8% 0.45 0.83 41 0.0200 6.19 372 0.0065 0.10 0.016 1.62 3.84 10.02 413 12.30 10.02 OVERALL LENGTH (ft/ft) tc (min) SLOPE (ft/ft) ti (min) LENGTH (ft) SLOPE (ft/ft) VELOCITY (ft/s) ROUGHNESS COEFFICIENT HYDRAULIC RADIUS (ft) 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) September 13, 2022 Seven Generations Multifamily DEVELOPED TIME OF CONCENTRATION J.Claeys 22-1057-00 Highland Development Services, Inc. ticttt+= V Ltt60 =1.871.1 10 180 +=LtcV.R2/3 S 1/2 22-1057-00 Rational Calcs.xlsx Page 3 of 5 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) 1A 1A 65.1% 0.93 0.35 63 0.0200 2.02 159 0.0070 0.10 0.016 1.68 1.58 5.00 222 11.23 5.00 1B 1B 77.6% 1.00 0.98 103 0.0200 1.50 234 0.0050 0.10 0.016 1.42 2.75 5.00 337 11.87 5.00 1A+1B 1A+1B 74.4% 1.00 1.33 103 0.0200 1.50 234 0.0050 0.10 0.016 1.42 2.75 5.00 337 11.87 5.00 2 2 71.1% 0.92 1.72 55 0.0200 2.01 599 0.0065 0.10 0.016 1.62 6.17 8.19 654 13.63 8.19 2 1A+1B+2 72.5% 0.96 3.05 55 0.0200 1.57 599 0.0065 0.10 0.016 1.62 6.17 7.74 654 13.63 7.74 3 3 32.8% 0.56 0.83 41 0.0200 5.13 372 0.0065 0.10 0.016 1.62 3.84 8.96 413 12.30 8.96 OVERALL LENGTH (ft/ft) tc (min) SLOPE (ft/ft) ti (min) LENGTH (ft) SLOPE (ft/ft) VELOCITY (ft/s) HYDRAULIC RADIUS (ft) ROUGHNESS COEFFICIENT 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) September 13, 2022 Seven Generations Multifamily DEVELOPED TIME OF CONCENTRATION J.Claeys 22-1057-00 Highland Development Services, Inc. ticttt+= V Ltt60 =1.871.1 10 180 +=LtcV.R2/3 S 1/2 22-1057-00 Rational Calcs.xlsx Page 4 of 5 Highland Development Services Design Engineer: Design Firm: Project Number: Date: EQUATIONS: P 1-2yr =0.82 in 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) Q2 (ft3/s) tc (min) Runoff Coeff (C2-10) C(A) (acres) Intensity (in/hr) Q10 (ft3/s) tc (min) Runoff Coeff. (C100) C(A) (acres) Intensity (in/hr) Q100 (ft3/s) 1A 1A 0.345 65.1% 5.78 0.74 0.26 2.67 0.68 5.78 0.74 0.26 4.55 1.17 5.00 0.93 0.32 9.95 3.19 1B 1B 0.985 77.6% 6.79 0.83 0.82 2.54 2.08 6.79 0.83 0.82 4.34 3.55 5.00 1.00 0.98 9.95 9.80 1A+1B 1A+1B 1.330 74.4% 7.14 0.81 1.07 2.50 2.69 7.14 0.81 1.07 4.27 4.59 5.00 1.00 1.33 9.95 13.23 2 2 1.720 71.1% 10.21 0.73 1.26 2.20 2.77 10.21 0.73 1.26 3.75 4.73 8.19 0.92 1.58 8.32 13.13 2 1A+1B+2 3.050 72.5% 9.86 0.77 2.34 2.23 5.20 9.86 0.77 2.34 3.80 8.89 7.74 0.96 2.92 8.49 24.80 3 3 0.826 32.8% 10.02 0.45 0.37 2.21 0.82 10.02 0.45 0.37 3.78 1.40 8.96 0.56 0.46 8.05 3.72 C n = n -yr runoff coefficient I n = n -yr rainfall intensity (in/hr) A n = Basin drainage area (ac) I = rainfall intensity (in/hr) P 1 = one-hour point rainfall depth (in) t c = time of concentration (min) 10-yr Peak Runoff 100-yr Peak Runoff Seven Generations Multifamily DEVELOPED PEAK RUNOFF DESIGN CRITERIA: Design Point Sub-basin Area (acres) J.Claeys Highland Development Services, Inc. 22-1057-00 September 13, 2022 2-yr Peak Runoff City of Fort Collins Stormwater Criteria Manual % Impervious Q n = n -yr peak discharge (cfs) nnnnAICQ=(0.786651) 1 )10( 5.28 ct PI + = 22-1057-00 Rational Calcs.xlsx Page 5 of 5 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 55,874 1.28 6,385 75% 4,789 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 1B 1B 42,894 77.6% 70,846 0.25 898 Storm Chamber 4,789 70,846 1479.4% Area (sq-ft) Area (acres) Treatment Ratio 42,894 0.98 96.3% 1,665 0.04 3.7% 44,559 1.02 Seven Generations Multifamily Low Impact Development Total % Required 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. Impervious Area Treated (sq-ft) Impervious Area Required for LID Treatment (sq-ft) LID Treatment Summary LID Treatment Areas J.Claeys Highland Development Services 22-1057-00 March 1, 2023 Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016) Description Total Redeveloped Area Total Improvement Area Water Quality Area Treatment Summary Description Total Area Treated by LID Total Area unable to be Treated Allowed FilterFabric Flow Ratea(cfs)0.35 gpm/sq-ftSC-106LP 14 10 6 6 85.4 25 12 14.8 0.012 6.9 15.0SC-310 18 8 6 6 85.4 34 16 20.2 0.016 14.7 31.0SC-740 18 8 6 6 85.4 51 30 30.2 0.024 45.9 74.9DC-780 18 12 6 9 85.4 51 30 30.2 0.024 46.2 78.4MC-3500 24 8 12 9 90 77 45 48.1 0.038 109.9 178.9 14.9 46MC-4500 24 7 12 9 52 100 60 36.1 0.028 106.5 162.6 35.7 108.7LIDFacilityChamberTypeTotalRelease Ratef(cfs) WQ Flowg(cfs)Req'd StorageVolumeh(cu-ft)Minimum No. of ChambersiChamberStoragej(cu-ft)No. ofEndcapskEndcapStoragel(cu-ft)Total ChamberVolumem(cu-ft)Total InstalledSystem Volumen(cu-ft)WQCV12-hr(cu-ft)1B SC-106LP 0.55 0.95209 48 329 4 0 329 926 898NegligibleEndcapVolumed(cu-ft)Min InstalledEndcap/AggregateVolumee(cu-ft)NegligibleNegligibleNegligibleMin InstalledChamber/AggregateVolumec(cu-ft)Seven Generations MultifamilyLow Impact DevelopmentStormTech Chamber Configuration SummaryStormTech Chamber DataDesign Engineer:Design Firm:Project Number:Date:Length(in)Width(in)Height(in)Floor Area(sq-ft)ChamberVolumeb(cu-ft)MinAggregate Base(in)Min Aggregate Cover(in)Max Cover(ft)Min Cover(in)ChamberModelJ.ClaeysHighland Development Services22-1057-00March 1, 2023Note:a. Release rate per chamber, limited by flow through geotextile with accumulated sediment. City acceptable flow rates determined to be approximately 1/2 of the Nov-07 Qmaxfrom Figure 17 of the "Final Report on Field Verification Testing of the StormTech Isoloator Row Treatement Unit", prepard by the University of New Hamphire Stormwater Center, dated Setpember 2010.b. Volume within chamber only, not accounting for void spaces in surrounding aggregate.c. Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit.d. Volume within endcap only, not accounting for void spaces in surrounding aggregate.e. Volume includes endcap and void spaces (40%) in surrounding aggregate, per chamber unit.f. Release rate per chamber times number of chambers. This is used as the allowed release rate for the FAA calculations.g. WQ flow, equal to 1/2 of the 2-yr peak runoff rate, referenced to size flow control structure.h. Required detention volume determined using the FAA Method based on the acceptable release rate of sediment accumulated filter fabric of the chambers and the 1/2 of the 2yr in flow rate.i. Number of chambers required to provide required FAA storage volume stored within the chamber and endcaps only (no aggregate storage).j. Total volume provided in chambers only (no aggregate storage).k. Number of endcaps based on desired chamber layout.l. Total volume provided in endcaps only (no aggregate storage).m. Total chamber and endcap storage (not aggregate storage). This number must meet or exceed the required FAA storage volume.n. System volume includes total chambervolumeplus surrounding aggregate volume,assumes a 40% void ratio for aggregate storage.This totalis provided from ADS Design Tool. DESIGN CRITERIA 0.83 1.00 0.83 ft3 acre-ft 0.99 acres 209 0.00 0.55 cfs Time (min) 1/2 2-yr Intensity (I , in/hr) Q100 (cfs) Accumulative Runoff Volume (ft3) Accumulative Release Volume (ft3) Detained Volume (ft3) Detained Volume (acre-ft) 0 0.000 0.00 0 0 0 0.00 5 1.425 1.17 350 166 183 0.00 10 1.105 0.90 542 333 209 0.00 15 0.935 0.76 688 499 189 0.00 20 0.805 0.66 790 666 124 0.00 25 0.715 0.58 877 832 44 0.00 30 0.650 0.53 957 999 -42 0.00 35 0.585 0.48 1,004 1,165 -161 0.00 40 0.535 0.44 1,050 1,332 -282 -0.01 45 0.495 0.40 1,093 1,498 -406 -0.01 50 0.460 0.38 1,128 1,665 -537 -0.01 55 0.435 0.36 1,174 1,831 -658 -0.02 60 0.410 0.34 1,207 1,998 -791 -0.02 March 1, 2023 Design Engineer: Design Firm: Project Number: Date: #SPILL! WQ Treatment Volume - FAA Method J.Claeys Highland Development Services 22-1057-00 Adjusted Runoff Coefficient (CC f ) Area (A ) Allowed Release Rate - City of Fort Collins - Storm Water Criteria Manual - City of Fort Collins accepts 1/2 of the 2-yr runoff as the WQ inflow rate WQ Treatment Volume Calculation - 1B Filtration Chamber Runoff Coefficient (C ) Frequency Factor (C f )Required Detention User Inputs Chamber Model: SC-160LP Outlet Control Structure: No Project Name: Seven Genera- tions Multifamily - SC-160LP Engineer: Jason Claeys Project Location: Colorado Measurement Type: Imperial Required Storage Volume: 875 cubic ft. Stone Porosity: 40% Stone Foundation Depth: 6 in. Stone Above Chambers: 6 in. Average Cover Over Chambers: 14 in. Design Constraint Dimensions:(16 ft. x 60 ft.) Results System Volume and Bed Size Installed Storage Volume: 926.40 cubic ft. Storage Volume Per Chamber: 6.85 cubic ft. Number Of Chambers Required: 48 Number Of End Caps Required: 12 Chamber Rows: 6 Maximum Length:62.86 ft. Maximum Width: 14.50 ft. Approx. Bed Size Required: 911.40 square ft. System Components Amount Of Stone Required: 56 cubic yards Volume Of Excavation (Not Including Fill): 68 cubic yards Total Non-woven Geotextile Required:285 square yards Woven Geotextile Required (excluding Isolator Row): 90 square yards Woven Geotextile Required (Isolator Row): 184 square yards Total Woven Geotextile Required:274 square yards Impervious Liner Required:0 square yards SHEET OFDATE:PROJECT #:DRAWN:CHECKED:THIS DRAWING HAS BEEN PREPARED BASED ON INFORMATION PROVIDED TO ADS UNDER THE DIRECTION OF THE SITE DESIGN ENGINEER OR OTHER PROJECT REPRESENTATIVE. THE SITE DESIGN ENGINEER SHALL REVIEW THIS DRAWING PRIOR TO CONSTRUCTION. IT IS THE ULTIMATERESPONSIBILITY OF THE SITE DESIGN ENGINEER TO ENSURE THAT THE PRODUCT(S) DEPICTED AND ALL ASSOCIATED DETAILS MEET ALL APPLICABLE LAWS, REGULATIONS, AND PROJECT REQUIREMENTS.1 19/12/22KLJKLJSTANDARD CROSS SECTIONSC-160LP4640 TRUEMAN BLVDHILLIARD, OH 43026DATEDRWNCHKDDESCRIPTIONMATERIAL LOCATION DESCRIPTION AASHTO MATERIAL CLASSIFICATIONS COMPACTION / DENSITY REQUIREMENT D FINAL FILL: FILL MATERIAL FOR LAYER 'D' STARTS FROM THE TOP OF THE 'C' LAYER TO THE BOTTOM OF FLEXIBLE PAVEMENT OR UNPAVED FINISHED GRADE ABOVE. NOTE THAT PAVEMENT SUBBASE MAY BE PART OF THE 'D' LAYER ANY SOIL/ROCK MATERIALS, NATIVE SOILS, OR PER ENGINEER'S PLANS. CHECK PLANS FOR PAVEMENT SUBGRADE REQUIREMENTS.N/A PREPARE PER SITE DESIGN ENGINEER'S PLANS. PAVED INSTALLATIONS MAY HAVE STRINGENT MATERIAL AND PREPARATION REQUIREMENTS. C INITIAL FILL: FILL MATERIAL FOR LAYER 'C' STARTS FROM THE TOP OF THE EMBEDMENT STONE ('B' LAYER) TO 14" (355 mm) ABOVE THE TOP OF THE CHAMBER. NOTE THAT PAVEMENT SUBBASE MAY BE A PART OF THE 'C' LAYER. GRANULAR WELL-GRADED SOIL/AGGREGATE MIXTURES, <35% FINES OR PROCESSED AGGREGATE. MOST PAVEMENT SUBBASE MATERIALS CAN BE USED IN LIEU OF THIS LAYER. AASHTO M145¹ A-1, A-2-4, A-3 OR AASHTO M43¹ 3, 357, 4, 467, 5, 56, 57, 6, 67, 68, 7, 78, 8, 89, 9, 10 BEGIN COMPACTIONS AFTER 12" (300 mm) OF MATERIAL OVER THE CHAMBERS IS REACHED. COMPACT ADDITIONAL LAYERS IN 6" (150 mm) MAX LIFTS TO A MIN. 95% PROCTOR DENSITY FOR WELL GRADED MATERIAL AND 95% RELATIVE DENSITY FOR PROCESSED AGGREGATE MATERIALS. ROLLER GROSS VEHICLE WEIGHT NOT TO EXCEED 12,000 lbs (53 kN). DYNAMIC FORCE NOT TO EXCEED 20,000 lbs (89 kN). B EMBEDMENT STONE: FILL SURROUNDING THE CHAMBERS FROM THE FOUNDATION STONE ('A' LAYER) TO THE 'C' LAYER ABOVE.CLEAN, CRUSHED, ANGULAR STONE AASHTO M43¹ 3, 357, 4, 467, 5, 56, 57 NO COMPACTION REQUIRED. A FOUNDATION STONE: FILL BELOW CHAMBERS FROM THE SUBGRADE UP TO THE FOOT (BOTTOM) OF THE CHAMBER.CLEAN, CRUSHED, ANGULAR STONE AASHTO M43¹ 3, 357, 4, 467, 5, 56, 57 PLATE COMPACT OR ROLL TO ACHIEVE A FLAT SURFACE.2,3 PLEASE NOTE: 1.THE LISTED AASHTO DESIGNATIONS ARE FOR GRADATIONS ONLY. THE STONE MUST ALSO BE CLEAN, CRUSHED, ANGULAR. FOR EXAMPLE, A SPECIFICATION FOR #4 STONE WOULD STATE: "CLEAN, CRUSHED, ANGULAR NO. 4 (AASHTO M43) STONE". 2.STORMTECH COMPACTION REQUIREMENTS ARE MET FOR 'A' LOCATION MATERIALS WHEN PLACED AND COMPACTED IN 6" (150 mm) (MAX) LIFTS USING TWO FULL COVERAGES WITH A VIBRATORY COMPACTOR. 3.WHERE INFILTRATION SURFACES MAY BE COMPROMISED BY COMPACTION, FOR STANDARD DESIGN LOAD CONDITIONS, A FLAT SURFACE MAY BE ACHIEVED BY RAKING OR DRAGGING WITHOUT COMPACTION EQUIPMENT. FOR SPECIAL LOAD DESIGNS, CONTACT STORMTECH FOR COMPACTION REQUIREMENTS. 4.ONCE LAYER 'C' IS PLACED, ANY SOIL/MATERIAL CAN BE PLACED IN LAYER 'D' UP TO THE FINISHED GRADE. MOST PAVEMENT SUBBASE SOILS CAN BE USED TO REPLACE THE MATERIAL REQUIREMENTS OF LAYER 'C' OR 'D' AT THE SITE DESIGN ENGINEER'S DISCRETION. ACCEPTABLE FILL MATERIALS: STORMTECH SC-160LP CHAMBER SYSTEMS NOTES: 1.CHAMBERS SHALL MEET THE REQUIREMENTS OF ASTM F2418, "STANDARD SPECIFICATION FOR POLYPROPYLENE (PP) CORRUGATED WALL STORMWATER COLLECTION CHAMBERS". 2.CHAMBERS SHALL BE DESIGNED, TESTED AND ALLOWABLE LOAD CONFIGURATIONS DETERMINED IN ACCORDANCE WITH ASTM F2787, "STANDARD PRACTICE FOR STRUCTURAL DESIGN OF THERMOPLASTIC CORRUGATED WALL STORMWATER COLLECTION CHAMBERS". LOAD CONFIGURATIONS SHALL INCLUDE: 1) INSTANTANEOUS (<1 MIN) AASHTO DESIGN TRUCK LIVE LOAD ON MINIMUM COVER 2) MAXIMUM PERMANENT (75-YR) COVER LOAD AND 3) ALLOWABLE COVER WITH PARKED (1-WEEK) AASHTO DESIGN TRUCK. 3.THE SITE DESIGN ENGINEER IS RESPONSIBLE FOR ASSESSING THE BEARING RESISTANCE (ALLOWABLE BEARING CAPACITY) OF THE SUBGRADE SOILS AND THE DEPTH OF FOUNDATION STONE WITH CONSIDERATION FOR THE RANGE OF EXPECTED SOIL MOISTURE CONDITIONS. 4.PERIMETER STONE MUST BE EXTENDED HORIZONTALLY TO THE EXCAVATION WALL FOR BOTH VERTICAL AND SLOPED EXCAVATION WALLS. 5.REQUIREMENTS FOR HANDLING AND INSTALLATION: ·TO MAINTAIN THE WIDTH OF CHAMBERS DURING SHIPPING AND HANDLING, CHAMBERS SHALL HAVE INTEGRAL, INTERLOCKING STACKING LUGS ·TO ENSURE A SECURE JOINT DURING INSTALLATION AND BACKFILL, THE HEIGHT OF THE CHAMBER JOINT SHALL NOT BE LESS THAN 1.5” ·TO ENSURE THE INTEGRITY OF THE ARCH SHAPE DURING INSTALLATION, a) THE ARCH STIFFNESS CONSTANT AS DEFINED IN SECTION 6.2.8 OF ASTM F2418 SHALL BE GREATER THAN OR EQUAL TO 400 LBS/FT/%. AND b) TO RESIST CHAMBER DEFORMATION DURING INSTALLATION AT ELEVATED TEMPERATURES (ABOVE 73° F / 23° C), CHAMBERS SHALL BE PRODUCED FROM REFLECTIVE GOLD OR YELLOW COLORS. D C B *TO BOTTOM OF FLEXIBLE PAVEMENT. FOR UNPAVED INSTALLATIONS WHERE RUTTING FROM VEHICLES MAY OCCUR, INCREASE COVER TO 20" (510 mm). 14" (350 mm) MIN* 10' (3.0 m) MAX 6" (150 mm) MIN 12" (300 mm) MIN 25" (635 mm) 12" (300 mm) MIN DEPTH OF BASE STONE TO BE DETERMINED BY SITE DESIGN ENGINEER 6" (150 mm) MINA 12" (305 mm) EXCAVATION WALL (CAN BE SLOPED OR VERTICAL) PERIMETER STONE (SEE NOTE 4) SC-160LP END CAP SUBGRADE SOILS (SEE NOTE 3) NO SPACING REQUIRED BETWEEN CHAMBERS PAVEMENT LAYER (DESIGNED BY SITE DESIGN ENGINEER) ADS GEOSYNTHETICS 601T NON-WOVEN GEOTEXTILE ALL AROUND CLEAN CRUSHED, ANGULAR STONE IN A & B LAYERS StormTechChamber System888-892-2694 | WWW.STORMTECH.COM® Appendix D APPENDIX D – CAPACITY CALCULATIONS 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10Capacity (cfs)Head (ft) Nyloplast 24" Drop In Grate Inlet Capacity Chart 0.80' HeadAvailable4.9 cfs Capacity 3.6 cfs 10-yr Peak Flow 0.43' HeadNeeded