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HomeMy WebLinkAboutVOA SENIOR HOUSING - FDP200015 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTPRELIMINARY DRAINAGE LETTER FOR VOA SENIOR HOUSING AT EAST DRAKE ROAD & JOSEPH ALLEN DRIVE FORT COLLINS, COLORADO PRESENTED TO THE CITY OF FORT COLLINS FORT COLLINS, COLORADO April 3, 2019 April 3, 2019 Wes Lamarque, P.E. City of Fort Collins Utilities – Stormwater Engineering 700 Wood Street Fort Collins, CO 80521 RE: Drake and Joseph Allen Affordable Housing – Preliminary Drainage and Erosion Control Letter JVA Job No. 3027c Dear Wes: This letter has been prepared to summarize the drainage concept, solutions and changes in impervious area associated with the site improvements for the VOA Senior Housing development project located at the intersection of East Drake Road and Joseph Allen Drive in the City of Fort Collins. This letter represents an addendum to the approved Final Drainage and Erosion Control Report for Spring Creek Farms North Filing No. 4, dated January 8, 2014, prepared by Aspen Engineering. Existing Drainage Patterns The property is approximately 2.32 acres and is located in the southern portion of Outlot A within the Spring Creek Farms North Major Site. The site is currently undeveloped and predominantly consists of grassy open space with an existing detention pond. The existing ground surface is relatively flat, generally sloping from south to north at grades ranging from 0% to 1%. The majority of stormwater runoff is conveyed via surface flow into the existing detention pond which then flows into the public storm drainage system in Joseph Allen Drive via an outlet structure. See Figure 1: Historic Drainage Map. The site is located within Basin OS1 per the Spring Creek Farms North Filing No. 4 Final Drainage and Erosion Control Report. See Figure C-006 Erosion Control Plan & Drainage Exhibit. The site is located outside FEMA and City of Fort Collins mapped 100-year and 500-year floodplains, per FEMA Flood Risk Map Panel number 08069C1000F, effective date 12/19/2006. Proposed Drainage Patterns Proposed drainage patterns are to remain generally the same as the current, but will utilize landscaped areas, inlets and underground storage to capture the majority of runoff before discharging into the detention pond. The underground storage system will utilize StormTech technology for water quality and low impact development treatment. The site is graded as such to meet the City’s requirements of treating 75% of the sites modified or added impervious area. In general, the proposed development of the site consists of the proposed VOA National Services building that is approximately 17,840 square feet, an asphalt parking area, an access driveway on Joseph Allen Drive, and an amenity patio on the west side of the proposed building along with new storm infrastructure to facilitate the drainage characteristics of the site. The site has been divided into six hydrologic basins for analysis. Basin A represents the area draining towards the proposed area inlet on the west side of the proposed building. Basin B represents the western half of the proposed parking lot and the northwestern half of the roof and will drain towards proposed VOA Senior Housing Drainage and Erosion Control Letter April 3, 2019 2 of 7 StormTech chambers. Basins C and D represent areas draining around the building to the east, into a proposed storm sewer pipe and ultimately to the existing detention pond. Basin E represents the eastern half of the proposed parking lot and the northwestern half of the roof and will drain towards the proposed StormTech chambers. Basin F represents the northern portion of the site which includes a portion of the detention pond. Basins A, C and D will utilize grassed swales to collect runoff and also include culverts and storm pipe systems. All basins will eventually convey stormwater to Fossil Creek. It follows that the proposed improvements will increase the total impervious area of the basin, from 5.1% to 41.7%. This percentage of imperviousness corresponds to a runoff coefficient of 0.61 for the proposed site. Per the Spring Creek Farms North Filing No. 4 Final Drainage and Erosion Control Report, the existing detention pond was sized using a runoff coefficient of 0.7 for Basin OS1. Therefore, the existing detention pond has enough capacity to detain the runoff from the proposed site. The proposed parking lot encroaches slightly into the existing detention pond area on the northwest side of the site. The site will be graded in a way that the volume of the pond is balanced, and the detention volume will not be decreased. See Figure 2: Developed Drainage Map for the drainage basin boundaries and a summary of the existing and proposed impervious areas. Hydrologic and Hydraulic calculations are attached. Chapter 2 of the Urban Drainage and Flood Control District’s Urban Storm Drainage Criteria Manual Volume 3 (USDCM) provides guidelines for the selection of appropriate structural BMPs for a site that is to be developed or redeveloped. VOA Senior Housing is best characterized as a “conventional development” with just over 1 acre of impervious area on the project site. The BMP decision tree for such sites is provided in Figure 2-2 of the USDCM. The site and surrounding vicinity are comprised of hydrologic soil group Type C & D soils, per the NRCS soil survey. Permeable pavement (with partial or no infiltration) and/or the use of a “green roof”, rain garden, or grass swale/buffer are the recommended runoff reduction practices for this scenario. However, with the proposed configuration of the site underground StormTech Chambers were chosen to perform the LID water quality treatment. The proposed StormTech storm underground chambers located on the private storm system will treat storm runoff for a minimum of 75% of the modified or added impervious area on the site for water quality prior to discharge into the public storm system, satisfying the City of Fort Collins Low Impact Development (LID) requirements. The total impervious area was determined to be approximately 1. 12 acres. The existing impervious area was 0.08 acres, which results in 1.04 acres of added impervious surface area. Therefore, the required treated impervious area is 0.78 acres. The chambers will be designed to treat a minimum of 0.81 acres of the basin’s impervious area which preliminarily includes the parking lot area and a majority of the roof and concrete sidewalk area. The provided chamber sizing worksheet and directions from the City of Fort Collins staff was used to determine that a water quality flow of 0.86 cfs would be directed to the chambers. A restrictor plate on the influent pipe to the chambers will restrict flows to direct the water quality capture volume to the chambers and divert the rest of the flows to the north. The northern diversion pipe invert will be set at the restrictor plate invert elevation. All flows will combine downstream of the chambers before entering the existing outlet structure. The hydraulic capacity of the chambers will be designed to capture and treat the water quality capture volume. The sizing calculations are attached. The chamber design plans will be included with the Final Development Plans. These features will facilitate sedimentation and filtration while limiting erosion, providing both treatment and slowed release of the water quality capture volume. The proposed development of VOA Senior Housing Drainage and Erosion Control Letter April 3, 2019 3 of 7 this site will serve to reduce water quality and quantity impacts to natural drainageways by decreasing the frequency, rate, duration, and volume of runoff. Erosion and Sediment Control During construction, temporary erosion and sediment control practices will be used to limit soil erosion and sediment discharge off the site. Temporary Erosion Control A temporary erosion control plan is to be implemented for the site during construction. Temporary erosion control measures include, but are not limited to, slope and swale protection provided by the use of erosion control wattles/sediment control logs, rock socks, etc. All temporary erosion control measures are to be removed after they are deemed unnecessary. A general erosion control plan will be provided with the Final Development Plans. Permanent Erosion Control Chapter 2 of the Urban Drainage and Flood Control District’s Urban Storm Drainage Criteria Manual Volume 3 (USDCM) provides guidelines for the selection of appropriate permanent structural BMPs for a site that is to be developed or redeveloped. The VOA Senior Housing project is best characterized as a “conventional development” with over 1 acre of impervious area on the project site. The BMP decision tree for such sites is provided in Figure 2-2 of the USDCM. As previously stated, the site and surrounding vicinity is comprised of hydrologic soil group Type C/D soils, per the NRCS soil survey. The water quality capture volume (WQCV) for this site will be accounted for in the StormTech chambers located on the north side of the parking lot. A detention pond is located on the north end of the site. Runoff will be collected in the private storm system before connecting to the public storm system. Stormwater Management Controls The Stormwater Management Plan (SWMP) administrator will be determined at the time the project is bid for construction. According to the CDPHE Stormwater Fact Sheet – Construction, construction activities produce many different kinds of pollutants which may cause stormwater contamination problems. The main pollutant of concern at construction sites is sediment. Grading activities remove grass, rocks, pavement, and other protective ground covers, resulting in the exposure of underlying soil to the elements. The soil is then easily picked up by wind and/or washed away by rain or snowmelt. In addition, construction activities often require the use of toxic or hazardous materials such as fuel, fertilizers, pesticides, and herbicides, and building materials such as asphalt, sealants, and concrete, which may also pollute stormwater. These materials can be harmful to humans, plants, and aquatic life. There are no other known potential pollution sources. However, this condition should be confirmed by the owner/operator or SWMP administrator. Other pollution sources that could be present include: runoff from vehicle washing, vehicle maintenance and/or fueling. There are no VOA Senior Housing Drainage and Erosion Control Letter April 3, 2019 4 of 7 known existing non-stormwater components of discharge (i.e., springs, landscape irrigation return flow, and etc.), or any anticipated during construction. 1. All Disturbed and Stored Soil: The total disturbed area will be approximately 2.60 acres. Soil stockpiles should be kept below the locally mandated maximum height of 10 feet and surrounded with sediment control devices. If the storage of these soils occurs over a period greater than 30 days, then consider temporarily seeding the soil to minimize soil loss to wind and water erosion. 2. Vehicle Tracking of Sediments: The existing site is undeveloped. A temporary stabilized stone pad and/or Trackout Plate (Vehicle Tracking Control pad, VTC) will be provided at points of ingress and egress onto the unpaved area. The VTC is designed to reduce the amount of mud transported onto the public roads by construction traffic. If the site is extraordinarily muddy, then consider designating an area to wash construction vehicles before they leave the site and enter the public right-of-way. A BMP such as this is a good way to avoid the costs associated with street cleaning or accidentally discharging large amounts of sediment into other storm drain systems. When in doubt, choose methods that prevent pollution rather than ones that force clean-up at the downstream end just before the stormwater enters the receiving waters. In other words, the most efficient construction site BMPs are those that prevent erosion from happening. 3. Inlet Protection (IP): gravel inlet protection will be used on all existing downstream inlets to prevent sediment and debris from entering the storm drain system. 4. Street sweeping will be conducted as necessary to remove sediment tracked on to pavement and adjacent streets. 5. Management of Contaminated Soils: If contaminated soils are found, the contractor shall report to the SWMP administrator to be mitigated. 6. Loading and Unloading Operations: The existing entrance to the site is currently paved and loading/unloading activities will occur within the paved area of the site or a temporary gravel staging area will be provided. 7. Outdoor Storage Activities: Materials storage, waste disposal, and vehicle maintenance and fueling can occur within an enclosed and secure area. 8. Vehicle and Equipment Maintenance and Fueling: VOA Senior Housing Drainage and Erosion Control Letter April 3, 2019 5 of 7 Materials should be stored and handled in covered areas to prevent contact with stormwater, and chemicals should be stored within berms or secondary containment devices to prevent leaks and spills from entering stormwater runoff. Spill Management In general, spill prevention and response should include the following: a) Notification procedures to be used in the event of an accident. At the very least, the SWMP Administrator should be notified. Depending on the nature of the spill and the material involved, the Colorado Department of Health, downstream water users, or other agencies may also need to be notified. b) Instructions for clean-up procedures. c) Provisions for absorbents are to be made available for use in fuel areas, and for containers to be available for used absorbents. d) Procedures for properly washing out concrete trucks and other equipment in a manner and location so that the materials and wash water cannot discharge from the site, and never into a storm drain system or stream. 9. Significant Dust or Particulate Generating Processes: Disturbed areas not yet ready to be seeded, landscaped, paved, or otherwise stabilized shall be watered, or ripped as necessary to preclude visible dust emissions. Contractor shall make every effort to minimize particulate emissions from vehicles performing the work, including but not limited to regular maintenance of construction equipment. 10. Routine Maintenance Activates Involving Fertilizer, Pesticides, Detergents, Fuels, Solvents, Oils, Etc: Materials should be stored and handled in covered areas to prevent contact with stormwater, and chemicals should be stored within berms or secondary containment devices to prevent leaks and spills from entering stormwater runoff. 11. On-site Waste management Practices (Waste Piles, Liquid Wastes, Dumpsters, etc): Materials storage, waste disposal, and vehicle maintenance and fueling can occur within an enclosed and secure area. The area can be enclosed with temporary fencing and accessed through a gate with a lock. 12. Concrete Truck/Equipment Washing: A concrete washout facility will be provided onsite. Properly wash out concrete trucks and other equipment in a manner and location (a minimum of 50 feet away from any inlet structures) so that the materials and wash water cannot discharge from the site, and never into a storm drain system or stream. 13. Dedicated Asphalt and Concrete Batch Plants: There will be no dedicated batch plant on site. 14. Non-Industrial Waste Source Such as Workers Trash and Portable Toilets: VOA Senior Housing Drainage and Erosion Control Letter April 3, 2019 6 of 7 Garbage cans shall be located at break areas and portable toilets shall be provided if onsite bathroom facilities cannot be used. Locate dumpsters and portable toilets away from drainage courses (minimum 50 feet from any inlet structures) and stake down toilets to prevent tipping. 15. Other Areas or Procedures where Potential Spills can Occur: Records of spills, leaks, or overflows that result in the discharge of pollutants must be documented and maintained. Record all spills that are responded to, even if they do not result in a discharge of pollutants. Information that should be recorded for all occurrences includes the time and date, weather conditions, reasons for the spill, etc. Some spills may need to be reported to immediately. Specifically, a release of any chemical, oil, petroleum product, sewage, etc., which may enter waters of the State of Colorado (which include surface water, ground water and dry gullies or storm sewers leading to surface water) must be reported. More guidance is available on the web at www.colorado.gov. The Division’s toll-free 24-hour number for environmental hazards and chemical spills and releases is 1-877-518-5608. Sequence of Construction Activities Construction Start Date (This is the day you expect to begin disturbing soils, including grubbing, stockpiling, excavating, demolition, and grading activities): Summer, 2019. Final Stabilization Date (this is when the site is finally stabilized. This means that all disturbed areas have been either built on, paved, or a uniform vegetative cover reaching over 70% of the initial vegetative density has been established.) Even if you are doing one part of the project, the estimated completion date must be for the overall project: Summer, 2020. Construction Sequencing: (Detailed construction sequencing to be determined by the contractor) 1. Installation of temporary erosion and sediment control measures. This includes all sediment control logs, rock socks, erosion control blankets, and silt fence where all land disturbing activities will occur. 2. Sequence of all land disturbing activity. Demolition of existing features in preparation of construction of proposed site features. Installation of Stormtech chambers will occur after demolition. 3. Sediment basins, temporary channel stabilization. Sediment control logs or erosion control blankets will be installed on the banks of the vegetated detention pond and swale on the west part the site. 4. Seeding All disturbed areas will be seeded upon completing of finish grading. Refer to the landscape plans for detailed planting and seeding schedule. 5. Mulching. Spread straw mulch uniformly over seeded areas at a rate of 90 lbs per 1000 square feet of ground. No more than 25% of the ground should be visible. Crimp or pinch mulch into soil 2-4 inches by using either a mulch anchoring tool, a farm disk operating on the contour of the slope, or by cleating with bulldozer tracks operating up and down the slopes (to prevent tracks from forming gullies). VOA Senior Housing Drainage and Erosion Control Letter April 3, 2019 7 of 7 6. Required maintenance activities (e.g. after-storm checks of all BMPs, etc.). All temporary sediment control BMPs shall be inspected after each rain event to ensure proper protection and to determine if cleaning is necessary. Final cleaning of all storm facilities shall be provided upon final stabilization of site. Please feel free to contact me to discuss any questions you may have. Sincerely, JVA, INCORPORATED By: ________________________________ Erik Nakos, P.E. . Project Manager Enclosures: Figure 1: Historic Drainage Map, Figure 2: Developed Drainage Map, Rational Calculations, StormTech Chamber Sizing Calculations, CD1.0 Grading & Drainage Details, Figure C-006 Erosion Control Plan & Drainage Exhibit, and Pond 100 Sizing Calcs HISTORIC DRAINAGE MAP FIG 1 NO. DATE DES'D D'WN REVISION DESCRIPTION DESIGNED BY: DRAWN BY: CHECKED BY: JOB #: DATE: © JVA, INC. VOA NATIONAL SERVICES FORT COLLINS, COLORADO SHEET NO. 3027c 02/20/2019 ETN TWW TWW JVA, Inc. 213 Linden Street, Suite 200 www.jvajva.com Fort Collins, CO 80524 970.225.9099 Boulder ● Fort Collins ● Winter Park Glenwood Springs ● Denver DEVELOPED DRAINAGE MAP FIG 2 NO. DATE DES'D D'WN REVISION DESCRIPTION DESIGNED BY: DRAWN BY: CHECKED BY: JOB #: DATE: © JVA, INC. VOA NATIONAL SERVICES FORT COLLINS, COLORADO SHEET NO. 3027c 02/20/2019 ETN TWW TWW JVA, Inc. 213 Linden Street, Suite 200 www.jvajva.com Fort Collins, CO 80524 970.225.9099 Boulder ● Fort Collins ● Winter Park Glenwood Springs ● Denver JVA Incorporated Job Name: VOA Senior Housing I% C2 C5 C10 C100 213 Linden St, Suite 200 Job Number: 3027c Streets Paved 100% 0.95 0.00 0.95 1.00 Fort Collins, CO 80524 Date: 4/2/19 Concrete Drives/Walks 100% 0.95 0.00 0.95 1.00 Ph: (970) 225 9099 By: MEC Roof 90% 0.95 0.00 0.95 1.00 Gravel 40% 0.50 0.00 0.50 0.63 Landscaping (B soil) 2% 0.15 0.00 0.15 0.19 VOA Senior Housing Landscaping (C/D soil) 2% 0.25 0.00 0.25 0.31 Historic Runoff Coefficient & Time of Concentration Calculations Playground 25% 0.11 0.00 0.11 0.14 Location: Fort_Collins Artificial Turf 25% 0.20 0.00 0.20 0.25 Minor Design Storm: 2 Major Design Storm: 100 Soil Type: C/D Basin Design Data I (%) = 100% 100% 90% 40% 25% 25% 2% 2% I (%) tc Comp tc Final Basin Name Design Point Apaved streets (sf) Adrives/co nc (sf) Aroof (sf) Agravel (sf) Aplygnd (sf) Aart. turf (sf) Alscape (B soil) (sf) Alscape (C/D soil) (sf) ATotal (sf) ATotal (ac) Imp (%) C2 C5 C10 C100 Upper most Length (ft) Slope (%) ti (min) Length (ft) Slope (%) Type of Land Surface K Velocity JVA Incorporated Job Name: VOA Senior Housing I% C2 C5 C10 C100 213 Linden St, Suite 200 Job Number: 3027c Streets Paved 100% 0.95 0.00 0.95 1.00 Fort Collins, CO 80524 Date: 4/2/19 Concrete Drives/Walks 100% 0.95 0.00 0.95 1.00 Ph: (970) 225 9099 By: MEC Roof 90% 0.95 0.00 0.95 1.00 Gravel 40% 0.50 0.00 0.50 0.63 Landscaping (B soil) 2% 0.15 0.00 0.15 0.19 VOA Senior Housing Landscaping (C/D soil) 2% 0.25 0.00 0.25 0.31 Composite Runoff Coefficient Calculations Playground 25% 0.11 0.00 0.11 0.14 Location: Fort_Collins Artificial Turf 25% 0.20 0.00 0.20 0.25 Minor Design Storm: 2 Major Design Storm: 100 Soil Type: C/D Basin Design Data I (%) = 100% 100% 90% 40% 25% 25% 2% 2% I (%) Basin Name Design Point Apaved streets (sf) Adrives/c onc (sf) Aroof (sf) Agravel (sf) Aplygnd (sf) Aart. turf (sf) Alscape (B soil) (sf) Alscape (C/D soil) (sf) ATotal (sf) ATotal (ac) Imp (%) C2 C5 C10 C100 A 1 0 1,607 1,650 0 0 0 0 13,011 16,268 0.37 20.6% 0.39 0.00 0.39 0.45 B 2 8,690 2,040 4,575 0 0 0 0 1,202 16,507 0.38 91.5% 0.90 0.00 0.90 0.95 C 3 0 2,124 6,735 0 0 0 0 13,207 22,066 0.51 37.5% 0.53 0.00 0.53 0.59 D 4 0 938 0 0 0 0 0 4,319 5,257 0.12 18.5% 0.37 0.00 0.37 0.44 E 5 12,670 2,412 4,880 0 0 0 0 1,645 21,607 0.50 93.0% 0.90 0.00 0.90 0.95 F 6 0 502 0 0 0 0 0 30,837 31,339 0.72 1.6% 0.26 0.00 0.26 0.32 Property Boundary OA 21,245 6,276 17,840 0 0 0 0 55,084 100,445 2.31 44.7% 0.57 0.00 0.57 0.62 Overall Basin O1 21,360 9,623 17,840 0 0 0 0 64,221 113,044 2.60 41.7% 0.55 0.00 0.55 0.61 Area to Chambers (B,E) 7 21,360 4,452 9,455 0 0 0 0 2,847 38,114 0.87 90.0% 0.90 0.00 0.90 0.95 Runoff Coeff's 3027c - Rational Calculations 040219 Developed C Page 2 of 11 JVA Incorporated Job Name: VOA Senior Housing 213 Linden St, Suite 200 Job Number: 3027c Fort Collins, CO 80524 Date: 4/2/19 Ph: (970) 225 9099 By: MEC VOA Senior Housing Time of Concentration Calculations Location: Fort_Collins Minor Design Storm: 2 Major Design Storm: 100 Soil Type: C/D Sub-Basin Data tc Comp tc Final Basin Name Design Point ATotal (ac) C5 Upper most Length (ft) Slope (%) ti (min) Length (ft) Slope (%) Type of Land Surface Cv Velocity (fps) tt (min) Time of Conc ti + tt = tc Total Length (ft) tc =(L/180)+ 10 (min) Min tc A 1 0.37 0.00 50 2.0% 11.3 90 2.0% Paved areas & shallow paved swales 20 2.8 0.5 11.8 140 10.8 10.8 B 2 0.38 0.00 80 2.5% 13.3 10 1.0% Paved areas & shallow paved swales 20 2.0 0.1 13.4 90 10.5 10.5 C 3 0.51 0.00 40 2.0% 10.1 200 2.0% Paved areas & shallow paved swales 20 2.8 1.2 11.3 240 11.3 11.3 JVA Incorporated Job Name: VOA Senior Housing 213 Linden St, Suite 200 Job Number: 3027c Fort Collins, CO 80524 Date: 4/2/19 Ph: (970) 225 9099 By: MEC VOA Senior Housing Developed Storm Runoff Calculations Design Storm : 100 Year Point Hour Rainfall (P1 ) : 2.86 Basin Name Design Point Area (ac) Runoff Coeff tc (min) C*A (ac) I (in/hr) Q (cfs) Total tc (min) ΣC*A (ac) I (in/hr) Q (cfs) Inlet Type Q intercepted Q carryover Q bypass Pipe Size (in) or equivalent Pipe Material Slope (%) Pipe Flow (cfs) Max Pipe Capacity (cfs) Length (ft) Velocity (fps) tt (min) Total Time (min) Notes A 1 0.37 0.45 10.80 0.17 7.48 1.26 10.80 0.17 7.48 1.26 24" Area Drain 12 in RCP 1.0% 1.26 3.83 105 3.0 0.58 11.38 B 2 0.38 0.95 10.50 0.36 7.57 2.73 10.50 0.36 7.57 2.73 Combination 12 in RCP 1.0% 2.73 3.83 45 3.0 0.25 10.75 TOTAL DS of A 11.38 0.53 7.42 3.92 12 in RCP 1.0% 3.92 3.83 45 3.0 0.25 11.62 C 3 0.51 0.59 11.30 0.30 7.42 2.21 11.30 0.30 7.42 2.21 12 in RCP 1.0% 2.2 3.8 10 3.0 0.05 11.35 D 4 0.12 0.44 5.50 0.05 9.63 0.51 11.62 0.83 7.42 6.13 12 in RCP 1.0% 6.1 3.8 85 3.0 0.47 12.09 TOTAL DS of D 12.09 1.12 7.42 8.34 12 in RCP 1.0% 8.3 3.8 85 3.0 0.47 12.56 E 5 0.50 0.95 10.40 0.47 7.60 3.57 11.62 0.83 7.42 6.13 Combination 12 in RCP 1.0% 6.1 3.8 80 3.0 0.44 12.06 TOTAL DS of E 12.56 1.95 7.17 13.99 12 in RCP 1.0% 14.0 3.8 80 3.0 0.44 12.99 F 6 0.72 0.32 11.40 0.23 7.42 1.73 11.40 0.23 7.42 1.73 Tota Peak Flow 12.99 2.71 6.97 18.90 Tota Site Flow 20.18 Direct Runoff Total Runoff Inlets Pipe Pipe/Swale Travel Time 3027c - Rational Calculations 040219 Q100 Page 4 of 11 JVA Incorporated Job Name: VOA Senior Housing 213 Linden St, Suite 200 Job Number: 3027c Fort Collins, CO 80524 Date: 4/2/19 Ph: (970) 225 9099 By: MEC VOA Senior Housing Developed Storm Runoff Calculations Design Storm : 2 Year Point Hour Rainfall (P1 ) : 0.82 Basin Name Design Point Area (ac) Runoff Coeff tc (min) C*A (ac) I (in/hr) Q (cfs) Total tc (min) ΣC*A (ac) I (in/hr) Q (cfs) Inlet Type Q intercepted Q carryover Q bypass Pipe Size (in) or equivalent Pipe Material Slope (%) Pipe Flow (cfs) Max Pipe Capacity (cfs) Length (ft) Velocity (fps) tt (min) Total Time (min) Notes A 1 0.37 0.39 10.80 0.15 2.15 0.31 10.80 0.15 2.15 0.31 24" Area Drain 12 in RCP 2.0% 0.31 5.41 56 4.3 0.22 11.02 B 2 0.38 0.90 10.50 0.34 2.17 0.74 10.50 0.34 2.17 0.74 Combination 12 in RCP 0.8% 0.74 3.42 62 2.7 0.38 10.88 TOTAL DS of A 11.02 0.49 2.13 1.04 12 in RCP 2.0% 1.04 5.41 56 4.3 0.22 11.23 C 3 0.51 0.53 11.30 0.27 2.11 0.57 11.30 0.27 2.11 0.57 12 in RCP 0.9% 0.6 3.7 25 2.9 0.14 11.44 D 4 0.12 0.37 5.50 0.05 2.76 0.12 11.23 0.76 2.11 1.60 12 in RCP 1.2% 1.6 4.1 151 3.3 0.77 12.00 TOTAL DS of D 12.00 1.02 2.05 2.10 12 in RCP 1.2% 2.1 4.1 151 3.3 0.77 12.77 E 5 0.50 0.90 10.40 0.44 2.18 0.97 11.23 0.76 2.11 1.60 Combination 12 in RCP 3.7% 1.6 7.3 26 5.8 0.07 11.31 12.77 1.78 2.00 3.56 12 in RCP 3.7% 3.6 7.3 26 5.8 0.07 12.84 F 6 0.72 0.26 11.40 0.19 2.10 0.39 11.40 0.19 2.10 0.39 Tota Peak Flow 12.84 2.45 1.99 4.89 Tota Site Flow 5.21 CHAMBER FLOW WQCV (use 1/2 the Intensity calculated for the 2 year event) Area to Chamb #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A Direct Runoff Total Runoff Inlets Pipe Pipe/Swale Travel Time 3027c - Rational Calculations 040219 Q Minor Page 5 of 11 JVA Incorporated Job Name: VOA Senior Housing 213 Linden St, Suite 200 Job Number: 3027c Fort Collins, CO 80524 Date: 4/2/19 Ph: (970) 225 9099 By: MEC VOA Senior Housing LID AREA Calculations per City of Fort Collins - Option 2 The implementation of LID systems requires one of the following two options: Acres Notes Total Site Area = 2.60 Area within the drainage boundary Total Site Impervious Area = 1.12 Area of impervious surfaces Added or Modified Impervious Area = 1.04 Area of impervious surfaces - existing impervious surface area Required Impervious Area to be treated by LID = 0.78 75% of added or modified impervious area Total Site Area to Chambers = 0.87 Provided Impervious Area to LID = 0.81 3027c - Rational Calculations 040219 LID AREA Page 6 of 11 JVA Incorporated Job Name: VOA Senior Housing 213 Linden St, Suite 200 Job Number: 3027c Fort Collins, CO 80524 Date: 4/2/19 Ph: (970) 225 9099 By: MEC VOA Senior Housing Water Quality Capture Volume (WQCV) Calculations (UDFCD Volume 3 Chapter 3) WQCV=a((0.91I 3 )-(1.19I 2 )+(0.78I)) Where: WQCV = Water Quality Capture Volume (watershed inches) a = Drain Time Coefficient (see table below ) I = Imperviousness (%/100) Drainage Time (hrs) Coefficient, a 12 0.8 24 0.9 40 1.00 a= 0.80 12 hour drawdown time I= 0.900 %/100 WQCV= 0.322 watershed inches V=(WQCV/12)*A*43560 WQCV= 0.322 watershed inches A = 0.87 acre V = 1228 cf V = 0.028 acre-ft Fort Collins Stormwater Criteria Manual Fort Collins Stormwater Criteria Manual 3027c - Rational Calculations 040219 WQCV Page 7 of 11 JVA Incorporated Job Name: VOA Senior Housing 213 Linden St, Suite 200 Job Number: 3027c Fort Collins, CO 80524 Date: 4/2/19 Ph: (970) 225 9099 By: MEC VOA Senior Housing StormTech Chamber Sizing Calculation (per City of Fort Collins Example) 1 2 3 4 5 6 7 8 9 10 11 12 Vault ID Total Required WQ Volume (cf) Flow, WQ (cfs) Chamber Type Chamber Release Rate a (cfs) Chamber Volume b (cf) Installed Chamber Volume w/ Aggregate c (cf) Minimum No. of Chambers d Total Release Rate e (cfs) Required Storage Volume by FAA Method (cf) Minimum No. of Chambers f Storage Provided within the Chambers g (cf) Total Installed System Volume h (cf) Option 1 1228 #N/A SC-160 0.011 6.85 15.0 82 0.94 54 8 55 1230 Option 2 1228 #N/A SC-310 0.016 14.7 29.3 42 0.66 137 10 147 1231 Option 3 1228 #N/A SC-740 0.024 45.9 74.9 17 0.40 300 7 321 1273 a. Release rate per chamber, limited by flow through geotextile with accumulated sediment 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. Number of chambers required to provide full WQCV within total installed system, including aggregate. e. Release rate per chamber times number of chambers. f. Number of chambers required to provide required FAA storage volume stored within the chamber only (no aggregate storage). JVA Incorporated Job Name: VOA Senior Housing 213 Linden St, Suite 200 Job Number: 3027c Fort Collins, CO 80524 Date: 4/2/19 Ph: (970) 225 9099 By: MEC VOA Senior Housing Detention Pond Volume Calculations: Modifed FAA Procedure Opt 1 Modified FAA Procedure (1966) detention sizing method as modified by Guo (1999a) Drainage Basin Area to Chambers (B,E) Design Storm 2 year Composite "C" Factor 0.90 Basin Size 0.87 Release Rate Calculations Allowable Release Rate for Site 0.94 cfs (StormTech Chamber Opt 1) Less Undetained Offsite Flows - 0.00 cfs Allowable Release Rate for Pond 0.94 cfs Rainfall Intensity Calculations Point Hour Rainfall (P1 ) : 0.82 Rainfall Intensity: FortCollinsIDF Volume Calculations Inflow Volume = C * I * A * (60 * T) Outflow Volume = Alowable Release Rate * time (sec) Storage Volume = Invflow Volume - Outflow Volume Time T (min) Time T (sec) Intensity I (in/hr) WQ Intensity I/2 (in/hr) Inflow Vin (ft 3 ) Outflow Vout (ft 3 ) Storage Vstor (ft 3 ) 5.0 300 2.85 1.43 336 282 54 10.0 600 2.21 1.11 521 564 -43 15.0 900 1.87 0.94 661 846 -185 20.0 1,200 1.61 0.81 759 1,128 -369 25.0 1,500 1.43 0.72 842 1,410 -568 30.0 1,800 1.30 0.65 919 1,692 -773 35.0 2,100 1.17 0.59 967 1,974 -1,007 40.0 2,400 1.07 0.54 1,010 2,256 -1,246 45.0 2,700 0.99 0.50 1,052 2,538 -1,486 50.0 3,000 0.92 0.46 1,086 2,820 -1,734 JVA Incorporated Job Name: VOA Senior Housing 213 Linden St, Suite 200 Job Number: 3027c Fort Collins, CO 80524 Date: 4/2/19 Ph: (970) 225 9099 By: MEC VOA Senior Housing Detention Pond Volume Calculations: Modifed FAA Procedure Opt 2 Modified FAA Procedure (1966) detention sizing method as modified by Guo (1999a) Drainage Basin Area to Chambers (B,E) Design Storm 2 year Composite "C" Factor 0.90 Basin Size 0.87 Release Rate Calculations Allowable Release Rate for Site 0.66 cfs (StormTech Chamber Opt 2) Less Undetained Offsite Flows - 0.00 cfs Allowable Release Rate for Pond 0.66 cfs Rainfall Intensity Calculations Point Hour Rainfall (P1 ) : 0.82 Rainfall Intensity: FortCollinsIDF Volume Calculations Inflow Volume = C * I * A * (60 * T) Outflow Volume = Alowable Release Rate * time (sec) Storage Volume = Invflow Volume - Outflow Volume Time T (min) Time T (sec) Intensity I (in/hr) WQ Intensity I/2 (in/hr) Inflow Vin (ft 3 ) Outflow Vout (ft 3 ) Storage Vstor (ft 3 ) 5.0 300 2.85 1.43 336 198 137 10.0 600 2.21 1.11 521 397 124 15.0 900 1.87 0.94 661 595 66 20.0 1,200 1.61 0.81 759 794 -35 25.0 1,500 1.43 0.72 842 992 -150 30.0 1,800 1.30 0.65 919 1,191 -272 35.0 2,100 1.17 0.59 967 1,389 -423 40.0 2,400 1.07 0.54 1,010 1,588 -577 45.0 2,700 0.99 0.50 1,052 1,786 -734 50.0 3,000 0.92 0.46 1,086 1,985 -898 JVA Incorporated Job Name: VOA Senior Housing 213 Linden St, Suite 200 Job Number: 3027c Fort Collins, CO 80524 Date: 4/2/19 Ph: (970) 225 9099 By: MEC VOA Senior Housing Detention Pond Volume Calculations: Modifed FAA Procedure Modified FAA Procedure (1966) detention sizing method as modified by Guo (1999a) Drainage Basin Area to Chambers (B,E) Design Storm 2 year Composite "C" Factor 0.90 Basin Size 0.87 Release Rate Calculations Allowable Release Rate for Site 0.40 cfs (StormTech Chamber Opt 2) Less Undetained Offsite Flows - 0.00 cfs Allowable Release Rate for Pond 0.40 cfs Rainfall Intensity Calculations Point Hour Rainfall (P1 ) : 0.82 Rainfall Intensity: FortCollinsIDF Volume Calculations Inflow Volume = C * I * A * (60 * T) Outflow Volume = Alowable Release Rate * time (sec) Storage Volume = Invflow Volume - Outflow Volume Time T (min) Time T (sec) Intensity I (in/hr) WQ Intensity I/2 (in/hr) Inflow Vin (ft 3 ) Outflow Vout (ft 3 ) Storage Vstor (ft 3 ) 5.0 300 2.85 1.43 336 120 216 10.0 600 2.21 1.11 521 241 280 15.0 900 1.87 0.94 661 361 300 20.0 1,200 1.61 0.81 759 481 278 25.0 1,500 1.43 0.72 842 601 241 30.0 1,800 1.30 0.65 919 722 197 35.0 2,100 1.17 0.59 967 842 125 40.0 2,400 1.07 0.54 1,010 962 48 45.0 2,700 0.99 0.50 1,052 1,083 -31 50.0 3,000 0.92 0.46 1,086 1,203 -117 GRADING AND DRAINAGE PLAN C1.0 NO. DATE DES'D D'WN REVISION DESCRIPTION DESIGNED BY: DRAWN BY: CHECKED BY: JOB #: DATE: © JVA, INC. VOA NATIONAL SERVICES FORT COLLINS, COLORADO SHEET NO. 3027c 02/20/2019 ETN TWW TWW JVA, Inc. 213 Linden Street, Suite 200 www.jvajva.com Fort Collins, CO 80524 970.225.9099 Boulder ● Fort Collins ● Winter Park Glenwood Springs ● Denver This unofficial copy was downloaded on Oct-22-2018 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 55.0 3,300 0.87 0.44 1,129 1,323 -194 60.0 3,600 0.82 0.41 1,159 1,443 -284 65.0 3,900 0.78 0.39 1,195 1,564 -369 70.0 4,200 0.73 0.37 1,204 1,684 -480 75.0 4,500 0.70 0.35 1,237 1,804 -567 80.0 4,800 0.66 0.33 1,244 1,925 -680 85.0 5,100 0.64 0.32 1,282 2,045 -763 90.0 5,400 0.61 0.31 1,294 2,165 -872 95.0 5,700 0.58 0.29 1,298 2,285 -987 100.0 6,000 0.56 0.28 1,320 2,406 -1,086 105.0 6,300 0.54 0.27 1,336 2,526 -1,190 110.0 6,600 0.52 0.26 1,348 2,646 -1,298 115.0 6,900 0.51 0.26 1,382 2,767 -1,385 120.0 7,200 0.49 0.25 1,386 2,887 -1,501 Maximum Volume (ft 3 ) 300 Detention Storage Calculations 3027c - Rational Calculations 040219 Modified FAA WQ (3) Page 11 of 11 55.0 3,300 0.87 0.44 1,129 2,183 -1,054 60.0 3,600 0.82 0.41 1,159 2,382 -1,222 65.0 3,900 0.78 0.39 1,195 2,580 -1,385 70.0 4,200 0.73 0.37 1,204 2,779 -1,575 75.0 4,500 0.70 0.35 1,237 2,977 -1,740 80.0 4,800 0.66 0.33 1,244 3,176 -1,931 85.0 5,100 0.64 0.32 1,282 3,374 -2,092 90.0 5,400 0.61 0.31 1,294 3,573 -2,279 95.0 5,700 0.58 0.29 1,298 3,771 -2,473 100.0 6,000 0.56 0.28 1,320 3,970 -2,650 105.0 6,300 0.54 0.27 1,336 4,168 -2,832 110.0 6,600 0.52 0.26 1,348 4,366 -3,019 115.0 6,900 0.51 0.26 1,382 4,565 -3,183 120.0 7,200 0.49 0.25 1,386 4,763 -3,378 Maximum Volume (ft 3 ) 137 Detention Storage Calculations 3027c - Rational Calculations 040219 Modified FAA WQ (2) Page 10 of 11 55.0 3,300 0.87 0.44 1,129 3,102 -1,973 60.0 3,600 0.82 0.41 1,159 3,384 -2,225 65.0 3,900 0.78 0.39 1,195 3,666 -2,471 70.0 4,200 0.73 0.37 1,204 3,948 -2,744 75.0 4,500 0.70 0.35 1,237 4,230 -2,993 80.0 4,800 0.66 0.33 1,244 4,512 -3,268 85.0 5,100 0.64 0.32 1,282 4,794 -3,512 90.0 5,400 0.61 0.31 1,294 5,076 -3,782 95.0 5,700 0.58 0.29 1,298 5,358 -4,059 100.0 6,000 0.56 0.28 1,320 5,640 -4,320 105.0 6,300 0.54 0.27 1,336 5,922 -4,586 110.0 6,600 0.52 0.26 1,348 6,204 -4,856 115.0 6,900 0.51 0.26 1,382 6,486 -5,104 120.0 7,200 0.49 0.25 1,386 6,768 -5,382 Maximum Volume (ft 3 ) 54 Detention Storage Calculations 3027c - Rational Calculations 040219 Modified FAA WQ (1) Page 9 of 11 g. Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume. h. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required WQCV. *Allowable flow rate thru fabric considering rate is reduced by sedimentation between Isolator Row cleanings 3027c - Rational Calculations 040219 CHAMBER SIZING Page 8 of 11 D 4 0.12 0.00 20 5.0% 5.3 30 2.0% Paved areas & shallow paved swales 20 2.8 0.2 5.5 50 10.3 5.5 E 5 0.50 0.00 60 2.5% 11.5 10 1.0% Paved areas & shallow paved swales 20 2.0 0.1 11.6 70 10.4 10.4 F 6 0.72 0.00 70 5.0% 9.9 275 2.3% Paved areas & shallow paved swales 20 3.0 1.5 11.4 345 11.9 11.4 Property Boundary Total Site OA 2.31 0.00 Paved areas & shallow paved swales 20 0.0 0.0 0.0 0 10.0 5.0 Overall Basin O1 2.60 0.00 Paved areas & shallow paved swales 20 0.0 0.0 0.0 0 10.0 5.0 Area to Chambers (B,E) 7 0.87 0.00 70 2.5% 12.4 10 1.0% Paved areas & shallow paved swales 20 2.0 0.1 12.5 80 10.4 10.4 Initial Overland Time (ti ) Travel Time (tt ) tt =Length/(Velocity x 60) tc Urbanized Check ON 3027c - Rational Calculations 040219 Developed Tc Page 3 of 11 (fps) tt (min) Time of Conc ti + tt = tc Total Length (ft) tc=(L/180)+ 10 (min.) Min tc OS1 1 0 3,532 0 0 0 0 0 109,512 113,044 2.60 5.1% 0.27 0.00 0.27 0.33 137 1.0% 23.6 201 4.4% Short Pasture and lawns 7 1.5 2.3 25.9 338 11.9 11.9 TOTAL SITE 0 3,532 0 0 0 0 0 109,512 113,044 2.60 5.1% 0.27 0.00 0.27 0.33 Basin Name Design Point Time of Conc (tc) C2 C5 C10 C100 2 5 10 100 ATotal (sf) ATotal (ac) Q2 Q5 Q10 Q100 OS1 1 11.9 0.27 0.00 0.27 0.33 2.06 0.00 3.63 7.42 113,044 2.60 1.45 0.00 2.56 6.43 TOTAL SITE 113,044 2.60 1.45 0.00 2.56 6.43 Initial Overland Time (ti) Travel Time (tt) tt=Length/(Velocity x 60) tc Urbanized Check ON Runoff Coeff's Rainfall Intensities (in/hr) Area Flow Rates (cfs) Runoff Coeff's 3027c - Rational Calculations 040219 Historic Page 1 of 11