The URL can be used to link to this page

Home My WebLink AboutAFFORDABLE SELF STORAGE - FDP180020 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTFINAL DRAINAGE AND EROSION CONTROL REPORT FOR AFFORDABLE STORAGE of FORT COLLINS FINAL DRAINAGE AND EROSION CONTROL REPORT FOR AFFORDABLE STORAGE OF FORT COLLINS Prepared for: Affordable Storage Prepared by: North Star Design 700 Automation Drive, Unit I Windsor, Colorado 80550 (970) 686-6939 February 22, 2019 Job Number 177-10 ii February 22, 2019 Dan Mogen City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522-0580 RE: Final Drainage and Erosion Control Report for Affordable Storage of Fort Collins Dear Dan, I am pleased to submit for your review and approval, this Final Drainage and Erosion Control Report for Affordable Storage of Fort Collins. I certify that this report for the drainage design was prepared in accordance with the criteria in the City of Fort Collins Storm Drainage Manual. I appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Sincerely, Patricia Kroetch, P.E. 700 Automation Drive, Unit I Windsor, CO 80550 Phone: 970-686-6939 Fax: 970-686-1188 iii TABLE OF CONTENTS TABLE OF CONTENTS ............................................................................................................... iii 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location ...................................................................................................................1 1.2 Description of Property ............................................................................................1 2. DRAINAGE BASINS AND SUB-BASINS 2.1 Major Basin Description ..........................................................................................1 2.2 Sub-Basin Description .............................................................................................2 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations ..............................................................................................................2 3.2 Development Criteria Reference and Constraints ...................................................2 3.3 Hydrologic Criteria ..................................................................................................2 3.4 Hydraulic Criteria ....................................................................................................3 3.5 Four Step Process to Minimize Adverse Impacts of Urbanization ..........................3 4. DRAINAGE FACILITY DESIGN 4.1 General Concept ......................................................................................................4 4.2 Specific Flow Routing .............................................................................................5 4.3 Drainage Summary ..................................................................................................6 5. EROSION & SEDIMENT CONTROLS 5.1 Written Analysis .....................................................................................................8 5.2 SWMP Contact Information .................................................................................11 5.3 Identification and location of all potential pollution sources ................................12 5.4 Best Management Practices (BMP’s) for Stormwater Pollution Prevention .........12 5.5 Material Handling & Spill Prevention ...................................................................15 5.6 BMP Implementation .............................................................................................16 5.7 Soil Amendments, Permanent Seeding & Mulching .............................................17 6. CONCLUSIONS 6.1 Compliance with Standards ..................................................................................19 6.2 Drainage Concept ..................................................................................................19 7. REFERENCES ..................................................................................................................20 APPENDICES A Vicinity Map B Hydrologic Computations C Hydraulic Sizing Calculations D Detention System Sizing Calculations E BMP Schedule and Cost Estimate F LID Summary Table G Excerpts from Previous Reports H Figures and Tables 1 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location This site is located on the north side of Conifer Street, east of Red Cedar Circle in the Northwest Quarter of Section 1, Township 7 North, Range 69 West of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. See the Vicinity Map in Appendix A of this report. This project is bounded on the north and east by existing developed sites, on the west by existing Red Cedar Circle and on the south by existing Conifer Street. 1.2 Description of Property The entire project consists of approximately 3.2 acres. A portion of this property was previously the subject of a Development Plan entitled “Utility Plans for Evergreen Park Replat No. 1, Lots 7 & 8, Block 4” and the remainder of the site is undeveloped, with areas of existing volunteer weeds and grasses. We were able to locate the Utility Plans for Lot 7 & 8 and the preliminary drainage report that accompanied the utility plans but no final drainage report was available. It appears that Lot 7 & 8 were developed in conjunction with the east half of Lot 6 and was used for vehicle parking and storage for the existing uses on the west half Lot 6. The preliminary drainage report referenced above is included in Appendix F of this report. A detention pond exists on Lots 7 & 8 and with this development, the outlet structure and pipe will be removed. It is difficult to discern if this pond accommodates runoff from only Lots 7 & 8 or if it also accommodates runoff from the east half of Lot 6 also. Currently, there is a detention pond on Lot 6 along Red Cedar that accommodates the runoff from the west half of Lot 6 but the drainage report for Lot 6 does not address the east half of Lot 6 (see Appendix F). The lot to the east of Lot 6 (Lot 13) was developed without regard to conveyance for the runoff from Lot 6 therefore accommodations must be made through this development for this runoff or the east half of Lot 6 will be ‘landlocked’ without a path for runoff. It is anticipated that Lot 6 will provide detention for the east half of the lot, similar to the accommodations made for the west half of the lot. This development (Affordable Storage) will provide an easement and a 12” diameter pipe for conveyance of the current and future runoff from the east half of Lot 6. 2 Proposed development on-site will include six storage buildings, private drives between the buildings, a parking area and sidewalks. Existing drainage patterns will be altered to route flow to a proposed underground detention system in the central and southeast portions of the site which will release into the existing storm system near the southeast corner of the site. 2. DRAINAGE BASINS AND SUB-BASINS 2.1 Major Basin Description The proposed development lies within the Dry Creek Drainage Basin. Stormwater detention is required for this basin but water quality extended detention is not required because it is provided in the North East College Corridor Outfall (NECCO) detention pond. It is proposed to provide underground detention using a StormTech chamber system with underdrain. The sizing of this system was provided by Evan Fischgrund at Advanced Drainage Systems, Inc. and is provided in Appendix D. This site falls within Basins 124 and 624 (refer to Appendix A for map). The allowable release rate for the area in Basin 124 is the 100 year existing runoff and the allowable release rate for the area in Basin 624 is the 2 year historic runoff (0.2 cfs per acre). A composite release rate was calculated for this site and is discussed further in Section 4.2 of this report. 2.2 Sub-basin Description Runoff from this site currently flows to the existing street. From there, the runoff flows east on Conifer to an existing inlet near the intersection of Blue Spruce Drive and Conifer. With the proposed drainage concept for this site, the runoff from the site will flow to a proposed on site underground detention area and be released at the composite release rate of 1.50 cfs into the storm system in Conifer. 3 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations This report was prepared to meet or exceed the “City of Fort Collins Storm Drainage Design Criteria Manual” specifications. Where applicable, the criteria established in the “Urban Storm Drainage Criteria Manual” (UDFCD), 2001, developed by the Denver Regional Council of Governments, has been used. 3.2 Development Criteria Reference and Constraints The runoff from this site has been routed to conform to the requirements of the Dry Creek Drainage Basin and the City of Fort Collins Stormwater Department. Both stormwater runoff detention and water quality extended detention are required for this site with on-site detention and offsite (existing) water quality. The release rate from the site will be at the calculated composite release rate of 1.50 cfs. 3.3 Hydrologic Criteria Runoff computations were prepared for the 2-year minor and 100-year major storm frequencies utilizing the rational method. All hydrologic calculations associated with the basins are included in Appendix B of this report. Standard Form 8 (SF-8) provides time of concentration calculations for all sub-basins. Detention volume was calculated using the predetermined composite release rate of 1.50 cfs. The FAA method for detention sizing was utilized to determine the required volume. Refer to the detention calculations included in Appendix C of this report. 3.4 Hydraulic Criteria Hydraulic elements have been designed per City of Fort Collins standards to adequately convey the 100-year storm runoff from this site to the proposed underground detention area. A proposed 15” storm pipe will convey the detained runoff from the site to a new manhole located on the existing 24”storm pipe in Conifer Street. A 12” pipe will also convey existing and future runoff from Lot 6 to this 15” storm pipe and into the storm system in Conifer. 4 3.5 Four Step Process to Minimize Adverse Impacts of Urbanization Step 1. Employ Runoff Reduction Practices – reduction of runoff peaks, volumes, and pollutant loads as the site is developed by implementing Low-Impact Development (LID) facilities including:  Increase time of concentration by routing flows along the drive aisles and increasing the length of the flow path.  Routing runoff from the proposed site into the proposed StormTech system to promote infiltration and biological uptake.  Routing flows through filter material in the proposed StormTech system to increase time of concentration, promote infiltration and provide initial water quality. Step 2. Implement BMPs That Provide a Water Quality Capture Volume with Slow Release - The efforts outlined in Step 1 will facilitate the reduction of runoff; however, this development will also require water quality. Runoff will be routed through the StormTech system that will provide infiltration and detention prior to release into the public storm system which will reduce the amount of runoff generated from the site through infiltration, and also treat the runoff prior to releasing it from the site. The water quality extended detention for this site will occur offsite in the City owned and maintained water quality facility downstream of this site. A table showing the Low Impact Development practices being utilized within this project is provided in Appendix E. Step 3. Stabilize Streams - There are no major drainageways in or near this site therefore Step 3 it not directly applicable this project. However, this project will pay stormwater development fees and monthly stormwater utility fees which contribute to the City’s ongoing efforts to attain stream stability where and as needed. Step 4. Implement Site Specific and Other Source Control BMPs - This step applies to covering storage/handling areas and spill containment and control. Vehicle maintenance and washing will be completed off site to prevent potential spills of vehicle fluids. Any handling of chemicals will be completed inside the building and will be 5 handled per the applicable MSDS (material safety data sheet). Spills will be contained immediately and cleaned up using appropriate absorption materials. 4. DRAINAGE FACILITY DESIGN 4.1 General Concept The runoff from this site will flow primarily west to east in the drive aisle to the main drive aisle where it will be directed into the underground detention area. The runoff from the site will either flow on the surface or enter the underground detention area via an inlet. The detained runoff will discharge into the existing storm pipe located in Conifer Street. 4.2 Specific Flow Routing With this design, the site has been broken into 8 basins which described in the following paragraphs. There is also a 12” pipe on site that is used to convey existing and future runoff from the lot to the north (Lot 6). The area that this pipe serves is the east 0.47 acres according to the previously approved drainage report included in Appendix F of this report. The area is currently gravel and dirt and is used for vehicle storage. This area is called OS1 in the runoff calculations in order to estimate the runoff anticipated in the current conditions. Basin 1 is located in the northmost portion of the site. This Basin contains the northmost private drive, a portion of Building E, the east leg of Building D and the north half of Building C. The runoff from this basin will flow east in a concrete pan will enter the underground detention area via a drain basin. Basin 2 is located in the central portion of the site. This Basin contains the middle drive aisle, a portion of Building F, the south half of Building C, the north half of building B and a portion of the south leg of Building D. The runoff from this basin will flow east in a concrete pan to the north-south drive aisle. The runoff from this basin will flow east in a concrete pan will enter the underground detention area via a drain basin. Basin 3 is located in the central portion of the site. This Basin contains the southmost drive aisle, the south half of Building B, all of the Building A and a portion of the west half of Building F. The runoff from this basin will flow east in a concrete pan to the 6 north-south drive aisle. The runoff from this basin will flow east in a concrete pan will enter the underground detention area via a drain basin. Basin 4 is located in the southern portion of the site. This Basin contains the grassed swale on the south side of Building A. The flow will be collected in two drain basins and will be directed to the underground detention system. Basin 5 is located in the east portion of the site. This Basin contains the east drive aisle, the east half of Building F and a small portion of Building E. The runoff from this basin will flow south in a concrete curb to two vane grate combination inlets. The flow will then be directed south and will enter the underground detention system. Basin 6 is located in the south central portion of the site and contains the entry drive and a small portion of Building F. The runoff will flow to a concrete pan and be directed south to a vane-grate combination inlet and into the underground detention area. Basins 7A and 7B are the site areas that drain to the street undetained. A majority of the area that is draining to the street is a narrow landscape strip located along the perimeter of the site adjacent to the right of way. Basins 7A and 7B cannot be captured and do not drain to the underground LID system and, therefore, will not be treated. The impervious area is a portion of the drive entry that drains to Red Cedar and a portion of the drive entry that drains to Conifer Street. Each drive entry area is restricted to less than 750 square feet per City criteria. Drainage design for this site has been designed to convey on-site runoff to the proposed underground detention chamber system and incorporate the required LID enhancement features. On-site runoff will be conveyed to the underground detention system via drain basins. The underground detention chamber system will release the detained runoff from the site at the rate of 1.50 cfs. This rate was calculated by determining the area of the site that falls in NECCO Basin 124 (0.40 acres) and calculating the 100 year existing runoff (1.73 cfs). The remainder of the site (2.83 acres) falls within NECCO Basin 624 and is allowed to release at the rate of 0.2 cfs per acre which gives an additional allowable release of 0.566 cfs. This totals an allowable release rate of 2.296 cfs but this rate was 7 reduced by the free release from Basins 7A and 7B (0.8 cfs) giving a composite allowable detention release of 1.496 cfs. If the outlet structure for the underground detention system becomes plugged or otherwise inundated, the water would back up in the system and back charge the inlets. The water would then flow out of the inlets and eventually flow out the access point on Conifer Street. The elevations of the interim high points in the pans are such that this overflow can occur without flooding the adjacent buildings. 4.3 Drainage Summary This site has been designed to meet or exceed the “City of Fort Collins Storm Drainage Design Criteria Manual” specifications. The proposed drainage design for this site has been designed to convey on-site runoff to the underground StormTech detention chambers while minimizing future maintenance. The site incorporates LID (Low Impact Development) volume in the chambers in addition to the detention volume. Refer to the end of Appendix F for a table indicating the sizing of the required volume for LID treatment. All drainage facilities proposed with this project, including the underground detention chambers, drain basins, inlets and storm pipe within the site boundaries are private and will be owned and maintained by the property owner. The existing storm pipe and the proposed storm manhole in the Conifer Street right of way will be owned and maintained by the City of Fort Collins. The pipe connecting the underground detention system to the existing storm pipe in Conifer Street is private and will be owned and maintained by the owner of the Affordable Storage site. The 12” pipe to be installed from Lot 6 to Conifer Street is private and will be maintained by the owner of Lot 6. A maintenance agreement is being negotiated. 8 5. EROSION & SEDIMENT CONTROLS 5.1 Written Analysis An Erosion and Sediment Control Plan is included herewith. It should be noted, however, that any such Erosion and Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of the BMPs depicted, and additional or different BMPs from those included may be necessary during construction, or as required by the authorities having jurisdiction. It shall be the responsibility of the Contractor to ensure erosion control measures are properly maintained and followed. The Erosion and Sediment Control Plan is intended to be a living document, constantly adapting to site conditions and needs. The Contractor shall update the location of BMPs as they are installed, removed or modified in conjunction with construction activities. It is imperative to appropriately reflect the current site conditions at all times. The Erosion and Sediment Control Plan shall address both temporary measures to be implemented during construction, as well as permanent erosion control protection. Best Management Practices from the Volume 3, Chapter 7 - Construction BMPs will be utilized. Measures may include, but are not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways and inlet protection at proposed storm inlets. Vehicle tracking control pads, spill containment and clean-up procedures, designated concrete washout areas, dumpsters, and job site restrooms shall also be provided by the Contractor. Grading and Erosion Control Notes can be found on Sheet 2 of the Utility Plans. In addition to this report and the plan sheets, the Contractor shall be aware of and adhere to the applicable requirements outlined all Development Agreements pertaining to this property. Also, the Site Contractor for this project will be required to secure a Stormwater Construction General Permit from the Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division - Stormwater Program, before commencing any earth disturbing activities. The Contractor shall also develop a comprehensive Storm Water Management Plan (SWMP) conforming to applicable requirements including descriptions of the ongoing activities, inspections and maintenance of construction BMPs. 9 • The site is approximately 3.23 acres all of which will undergo earthmoving operations. The existing site has existing ground cover (volunteer grasses and weeds) on approximate 45% - 50% of the site as the site has been historically used for storage of materials and vehicles for adjacent properties. Runoff from this site currently discharges to Conifer Street on the south side of the site. With the proposed development, this site will also be sloped to drain to the southeast. The runoff will then enter the proposed underground detention system and be released to the existing storm system in Conifer Street as the historic flow path dictates. The soils on this site are classified by the USGS Soil Survey as Caruso Clay Loam (3%) which is classified in the hydrologic group D and Nunn Clay Loam (97%) which is classified in the hydrologic group C. The D soils are described as 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. The rainfall erodibility is deemed to be moderate and the wind erodibility is deemed to be moderate to high. The C soils are described as 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. The rainfall erodibility is deemed to be moderate and the wind erodibility is deemed to be moderate to high. The site is surrounded by developed sites including streets, buildings and paved areas. The construction shall utilize silt fence around the perimeter to control sediment transport from rainfall and from wind. The silt fence that is located in the proposed pavement areas will be removed prior to placing new pavement. Rock socks will be utilized in the existing curb and proposed bio swales to capture sediments that are not fully contained by the silt fence placement. The locations of the rock socks will be in the areas of concentrated flow such as in the existing curb, at the concrete sidewalk chase and on the concrete pans. The site will also utilize a vehicle tracking control pad to minimize sediment from being tracked onto adjacent pavements. Sediment that is tracked will be removed and placed 10 within the site or permanently disposed of offsite. A concrete washout will be used on site during the concrete placement. All hardened concrete will be disposed of offsite. These BMP’s have not been located on the site map due to the fact that the site is very small and these BMP’s will need to be placed by the contractor in locations that are most beneficial and will minimize disruption of adjacent traffic. Permanent erosion control consists of covering the soils with a building, concrete walks, concrete pavement, recycled asphalt pavement and sod. No soil will be left exposed to erosion after the construction is complete. Refer to the landscape plan for areas of and instructions for placement of sod and soil amendments required prior to placement of sod. Refer to Appendix E for the timing of the construction phases and the sequential installation of all BMP phasing for this site. Refer to the Appendix E for the Erosion Control Surety calculations. 11 5.2 SWMP contact information Permit holder: Name: Address: Phone Number: Email Address: Appointed agent: Name: Address: Phone Number: Email Address: 12 5.3 Identification and location of all potential pollution sources Potential Pollutant Source Activity Potential Pollutant Generated Applicable to this project Control Measure Disturbed Areas Sediment X Silt Fence, Rock Socks Soil stockpiles Sediment X Silt Fence, Rock Socks Travel to adjacent public streets Tracked sediment X Tracking Pad, street sweeping Contaminated soils Sediment, chemicals Possible Remove contaminated soils from site ** Loading and unloading chemicals Chemicals Unloading of building materials Trash, debris, track out X Trash dumpsters, Waste Management Firm ** Outdoor storage of chemicals Chemicals On site equipment maintenance Oil, grease On site equipment fueling Diesel, gasoline X Containment berm ** Dust generating activities Particulates, sediment X Water truck Use of fertilizer, pesticides, herbicides Fertilizer, pesticides Use of detergents, solvents, oils Detergents, solvents, oil X If spilled, remove contaminated soils from site ** Waste Chemicals, trash, debris X Waste Management Firm Concrete wash Concrete, sediment, wash water X Remove hardened concrete, dispose of offsite ** On site equipment washing Detergents, oil On site asphalt batch plant Asphaltic cement, sediment On site concrete batch plant Cement, sediment Portable toilets Domestic sewage X Waste Management Firm ** Refer to Section 5.5 for additional Materials Handling & Spill Prevention BMP 5.4 Best Management Practices (BMP’s) for Stormwater Pollution Prevention Structural Practices for Erosion and Sediment Control Structural practices for the site will consist mainly of silt fence and rock sock filters and are described in detail in the following paragraphs. These BMP's are expected to change as the construction progresses and it is the responsibility of the contractor to ensure appropriate BMP's are in place and/or removed at the appropriate time in the construction sequence. All temporary and permanent erosion and sediment control practices must be maintained and repaired as needed to assure continued performance of their intended function. 13 Silt fence and rock sock filters shall be in place prior to commencement of construction activities. During clearing and grubbing necessary for silt fence installation, all cleared material shall be placed on the uphill side so that if erosion occurs from the cleared material, the sediment will be trapped and not transported downstream. Rock socks shall be implemented in the existing curb line as shown on the Drainage & Erosion Control Plan. A vehicle tracking pad will be installed at a location most beneficial to the site construction as determined by the contractor. Vehicles will not be permitted in the excavated area if soil is muddy. Gravel sub base will be placed and compacted in the areas indicated for pavement following excavation. All BMP's shall be installed per the details shown on the construction plan set. Temporary & Permanent Structural BMP’s: Refer to table in Section 5.3 for purpose of Structural BMP noted below Structural BMP Approximate location on site Applicable to this Project Silt Fence Site perimeter, refer to site map X Rock Socks At existing sidewalk culverts, in existing gutters, refer to site map X Earthen diversion dams Vegetated swales Sediment trap/pond Pipe slope drains Geogrid Inlet/outlet protection Culverts Refer to site map X Riprap Erosion control mats Inlet protection Vehicle Tracking Control Pad At site entrance, refer to site map X Concrete Washout To be located by Contractor X Non-Structural Practices for Erosion and Sediment Control: Soils exposed during the earthwork phase and landscape prep phase shall be kept in a roughened condition by ripping or disking along land contours until mulch, vegetation, or other permanent erosion control is installed. No large amount of soils (in excess of 15 yards) will be allowed to be stock piled on site. Overburden from the utility pipe 14 trenching will be piled adjacent to trenches upstream of sediment controls and will be replaced in the trenches within 72 hours. Excess excavated materials from the demolition and grading phases of the project that cannot be reused on site will be exported as it is excavated. This includes any asphalt pavement from the existing site that is to be removed. In the current pre construction state the site enables tracking of silt onto the adjacent streets during wet conditions. During construction activities the street will be monitored for foreign debris tracked out of the site and mechanical sweeping and clean up will be performed as needed. No area shall remain exposed by land disturbing activity for more than thirty (30) days before required temporary or permanent erosion control (e.g. seed/mulch, landscaping, etc.) is installed. Temporary & Permanent non-structural BMP’s: Refer to table in Section 5.3 for purpose of Non Structural BMP noted below Non-Structural BMP Approximate location on site Applicable to this Project Surface roughening Entire site X Soil stockpile height limit (less than 10’) Perimeter vegetative buffer east boundary of site X Minimization of site disturbance Mulch Seed & mulch stockpiles after 30 days Preservation & protection of existing vegetation & trees east boundary of site X Good site housekeeping (routine cleanup of trash & constr debris) Entire Site X Sweeping & scraping of hardscape areas On and off site pavements X Heavy equip staged on site, properly maintained & inspected daily (no onsite maintenance) Staging area X 15 5.5 Material Handling & Spill Prevention Refer to table in Section 5.3 Materials Handling & Spill Prevention BMP Approximate location on site Applicable to this Project Portable toilets, anchored & located away from drainages Contractor to determine X Fuel storage located in bulk tanks with secondary containment & spill kit Mobile fueling performed at least 200 feet away from drainages & fully attended Contractor to determine X Fertilizers, form oil, solvents, cleaners, detergent stored in 55 gal or smaller containers, kept in storage units Contractor to determine X Dumpsters containing used chemicals containers & liquid wastes kept covered Contractor to determine X Equipment cleaning (on site) uses no detergents & flows to onsite retention basin In case of a release of fuel or other chemicals, absorbent booms or earthen berms will be immediately constructed to contain the spill & prevent runoff to adjacent surface waters Location of spill X MSDS sheets for onsite chemicals will be kept at the construction trailer to facilitate spill response & cleanup Contractor to determine X B) Dedicated Asphalt or Concrete Batch Plant: Not proposed with this development C) Vehicle Tracking Pad: Vehicle tracking control pad shall be installed wherever construction vehicle access routes intersect paved public roads. Vehicle tracking control pads shall be installed to minimize the transport of sediment (mud) by runoff or vehicles tracking onto the paved surface. Any mud tracked to public roads shall be removed on a daily basis and after any significant storm that causes sediment to be transported. It is unlawful to track sediment/mud onto public streets and may be enforced by the City of Fort Collins, by the State of Colorado or by the EPA. D) Waste Management and Disposal: Portable toilets will be anchored & periodically maintained by waste management company. Dumpsters on site will be covered & periodically emptied by waste 16 management company. Concrete waste will be allowed to harden and then will be removed from site. No vehicle or equipment washing activities will occur on site. Location of the concrete washout is shown on the site map. The washout will be sufficiently deep to accommodate all anticipated concrete truck wash water. Waste concrete will be allowed to harden and be removed from site periodically as the washout reaches 50% of its capacity. Truck wash water will not be allowed to reach the curb & gutter or any other water course. E) Groundwater and Stormwater Dewatering: No groundwater was encountered during soils exploration therefore ground water is not anticipated to be an issue. If groundwater is encountered a groundwater discharge permit shall be obtained and a detailed report shall be completed describing the location and the route of where pumped groundwater will be conveyed and the measures taken to prevent the transport of any pollutants to downstream waters. 5.6 BMP Implementation A) Phased BMP Implementation BMP’s are expected to change as the construction progresses and it is the responsibility of the contractor to ensure appropriate BMP’s are in place and/or removed at the appropriate time in the construction sequence. A construction sequence schedule has been included on the Drainage & Erosion Control Plan and included in the construction plans for this site. All BMP’s shall be inspected and repaired or replaced as required to satisfy the conditions of the Stormwater Discharge Permit. All BMP’s must be maintained and repaired as needed to assure continued performance of their intended function. Refer to Appendix E for the BMP schedule and estimated costs. B) Inspection & Maintenance: It is required that routine site inspections are performed to effectively address maintenance and repair of Best Management Practices (BMP's). The site inspections are to performed by the contractor or an inspector designated by the administrator at a minimum of once every fourteen (14) calendar days on active construction sites and after 17 any significant storm event (an event causing runoff). As part of the site inspections the inspector is required to keep documentation of all inspections and BMP maintenance, including an updated Site Map indicating new BMP's or the removal of BMP's since the previous inspection. Any maintenance, repair, or necessary installation of BMP's that are noted during the inspection must be completed within seven (7) calendar days from the date of the inspection. 5.7 Soil Amendments, Permanent Seeding & Mulching A) Soil Amendments Soil in the Rain Gardens shall be amended per the City of Fort Collins Bioretention Sand Media Specifications found at: http://www.fcgov.com/utilities/img/site_specific/uploads/Bioretention_Sand_Media_Specs.pdf Soil treatment in the landscape area will be to spread imported or stockpiled topsoil to a minimum depth of four inches over areas to be planted. B) Permanent Seeding The following seed mix shall be applied at the rates indicated in the bioswale and in the water quality pond. Other landscaped areas on site shall be treated per the landscape plan. Mulch shall be applied after seeding as the notes indicate below. Drill seed specified mix in two passes, each at right angles to each other. Drill half of the seed in each pass. If areas are too wet or steep to drill seed, broadcast seed in two 18 opposite directions. Restore fine grade after seeding, and cover seed to depth of 1/4 inch by raking or dragging. Firm seeded areas with a roller weighing maximum of 100 lbs. per foot of width. Ground cover shall be considered established when 70% of the seed has been germinated. At the point that the seed is considered established, the temporary erosion control measures may be removed. C) Mulching All planted areas should be mulched preferably immediately following planting, but in no case later than 14 days from planting. Mulch conserves water and reduces erosion. The most common type of mulch used is hay or grass that is crimped into the soil to hold it. However, crimping may not be practical on slopes steeper than 3:1. The following guidelines should be followed with mulching: • Only weed-free and seed-free straw mulch should be used (grass hay often contains weedy exotic species). Mulch should be applied at 2 tons/acre and adequately secured by crimping, tackifier, netting, or blankets. • Crimping is appropriate on slopes of 3:1 or flatter and must be done so as to tuck mulch fibers into the soil 3 to 4 inches deep. • Tackifier or netting and blankets anchored with staples should be used on slopes steeper than 3:1. • Hydraulic mulching may also be used on steep slopes or where access is limited. Wood cellulose fibers mixed with water at 2,000 to 2,500 pounds/acre and organic tackifier at 100 pounds per acre should be applied with a hydraulic mulcher. 19 6. CONCLUSIONS 6.1 Compliance with Standards All computations that have been completed within this report are in compliance with the “City of Fort Collins Erosion Control Reference Manual for Construction Sites”, the “City of Fort Collins Storm Drainage Design Criteria Manual”, and the “Urban Storm Drainage Criteria Manual”. 6.2 Drainage Concept The proposed drainage concepts presented in this report and on the construction plans adequately provide for the collection and conveyance of on-site runoff to the underground detention system. Conveyance elements exist in Conifer Street to adequately convey detained runoff downstream. If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit would be required. 20 7. REFERENCES 1. Urban Drainage and Flood Control District, “Urban Storm Drainage Criteria Manual”, 2001 Edition Volume 1 updated June 2001, January 2004 and April 2008; Volume 2 updated June 2001 and April 2008; and Volume 3 updated November and December 2010. 2. The Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual, adopted by the City Council of the City of Fort Collins, as referenced in Section 26-500 (c) of the Code of the City of Fort Collins. 3. ORDINANCE NO. 152, 2012 of the Council of the City of Fort Collins amending Chapter 26 of the Code of the City of Fort Collins and the Fort Collins Stormwater Criterial Manual to incorporate provisions implementing Low Impact Development (LID) Principles. A APPENDIX A VICINITY MAP Soil Map—Larimer County Area, Colorado (Affordable Storage site) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/21/2019 Page 1 of 3 4494670 4494690 4494710 4494730 4494750 4494770 4494790 4494670 4494690 4494710 4494730 4494750 4494770 4494790 493670 493690 493710 493730 493750 493770 493790 493810 493830 493850 493670 493690 493710 493730 493750 493770 493790 493810 493830 493850 40° 36' 14'' N 105° 4' 29'' W 40° 36' 14'' N 105° 4' 21'' W 40° 36' 10'' N 105° 4' 29'' W 40° 36' 10'' N 105° 4' 21'' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 40 80 160 240 Feet 0 10 20 40 60 Meters Map Scale: 1:922 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 Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features 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 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 22 Caruso clay loam, 0 to 1 percent slope 0.1 2.0% 73 Nunn clay loam, 0 to 1 percent slopes 3.6 98.0% Totals for Area of Interest 3.7 100.0% Soil Map—Larimer County Area, Colorado Affordable Storage site Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/21/2019 Page 3 of 3 Wind Erodibility Index Map unit symbol Map unit name Rating (tons per acre per year) Acres in AOI Percent of AOI 22 Caruso clay loam, 0 to 1 percent slope 48 0.1 2.0% 73 Nunn clay loam, 0 to 1 percent slopes 48 3.6 98.0% Totals for Area of Interest 3.7 100.0% Description The wind erodibility index is a numerical value indicating the susceptibility of soil to wind erosion, or the tons per acre per year that can be expected to be lost to wind erosion. There is a close correlation between wind erosion and the texture of the surface layer, the size and durability of surface clods, rock fragments, organic matter, and a calcareous reaction. Soil moisture and frozen soil layers also influence wind erosion. Rating Options Units of Measure: tons per acre per year Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Wind Erodibility Index—Larimer County Area, Colorado Affordable Storage site Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/21/2019 Page 3 of 3 K Factor, Whole Soil Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 22 Caruso clay loam, 0 to 1 percent slope .32 0.1 2.0% 73 Nunn clay loam, 0 to 1 percent slopes .32 3.6 98.0% Totals for Area of Interest 3.7 100.0% Description Erosion factor K indicates the susceptibility of a soil to sheet and rill erosion by water. Factor K is one of six factors used in the Universal Soil Loss Equation (USLE) and the Revised Universal Soil Loss Equation (RUSLE) to predict the average annual rate of soil loss by sheet and rill erosion in tons per acre per year. The estimates are based primarily on percentage of silt, sand, and organic matter and on soil structure and saturated hydraulic conductivity (Ksat). Values of K range from 0.02 to 0.69. Other factors being equal, the higher the value, the more susceptible the soil is to sheet and rill erosion by water. "Erosion factor Kw (whole soil)" indicates the erodibility of the whole soil. The estimates are modified by the presence of rock fragments. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Layer Options (Horizon Aggregation Method): Surface Layer (Not applicable) K Factor, Whole Soil—Larimer County Area, Colorado Affordable Storage site Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/21/2019 Page 3 of 3 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 22 Caruso clay loam, 0 to 1 percent slope D 0.1 2.0% 73 Nunn clay loam, 0 to 1 percent slopes C 3.6 98.0% Totals for Area of Interest 3.7 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Hydrologic Soil Group—Larimer County Area, Colorado Affordable Storage site Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/21/2019 Page 3 of 4 Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado Affordable Storage site Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/21/2019 Page 4 of 4 Drainage Class Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 22 Caruso clay loam, 0 to 1 percent slope Somewhat poorly drained 0.1 2.0% 73 Nunn clay loam, 0 to 1 percent slopes Well drained 3.6 98.0% Totals for Area of Interest 3.7 100.0% Description "Drainage class (natural)" refers to the frequency and duration of wet periods under conditions similar to those under which the soil formed. Alterations of the water regime by human activities, either through drainage or irrigation, are not a consideration unless they have significantly changed the morphology of the soil. Seven classes of natural soil drainage are recognized-excessively drained, somewhat excessively drained, well drained, moderately well drained, somewhat poorly drained, poorly drained, and very poorly drained. These classes are defined in the "Soil Survey Manual." Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Drainage Class—Larimer County Area, Colorado Affordable Storage site Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/21/2019 Page 3 of 3 B APPENDIX B HYDROLOGIC COMPUTATIONS North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: Affordable Storage PROJECT NO: 177-06 COMPUTATIONS BY: ppk DATE: 2/12/2018 Recommended Runoff Coefficients from Table 3-3 of City of Fort Collins Design Criteria Recommended % Impervious from Urban Storm Drainage Criteria Manual % Runoff Impervious coefficient C Streets, parking lots (asphalt): 100% 0.95 Sidewalks: 96% 0.95 Gravel: 40% 0.50 Roofs: 90% 0.95 Lawns (flat <2%, heavy soil): 0% 0.20 SUBBASIN TOTAL TOTAL ROOF PAVED SIDEWALK GRAVEL LANDSCAPE % RUNOFF DESIGNATION AREA AREA AREA AREA AREA AREA AREA Impervious COEFF. (ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (C) 1 0.53 23292 11797 11495 0 0 0 95% 0.95 2 0.43 18711 9033 9,678 0 0 0 95% 0.95 3 1.20 52257 36174 14958 1,125 0 0 93% 0.95 4 0.20 8913 0 0 0 0 8,913 0% 0.20 5 0.47 20444 9180 9320 0 0 1,944 86% 0.88 6 0.14 6039 1810 3978 0 0 251 93% 0.92 7A 0.15 6,542 0 793 0 0 5,749 12% 0.29 7B 0.10 4,285 0 273 0 0 4,012 6% 0.25 OS1 (Lot 6) 0.47 20,473 0 0 0 20470 3 40% 0.50 Total to Detention 2.98 129,656 67,994 49,429 1,125 0 11,108 86% 0.89 Total 3.23 140,483 67,994 50,495 1,125 0 20,869 80% 0.84 Historic 124 0.40 17,410 0 1,540 665 3,780 11,425 21% 0.36 Historic 624 2.83 123,073 0 0 0 36,112 86,961 12% 0.29 Equations - Calculated C coefficients & % Impervious are area weighted C =  (Ci Ai) / At Ci = runoff coefficient for specific area, Ai Ai = areas of surface with runoff coefficient of Ci n = number of different surfaces to consider Flow_REV.xls Cval North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: Affordable Storage PROJECT NO: 177-06 COMPUTATIONS BY: ppk DATE: 2/12/2018 2-yr storm Cf = 1.00 FINAL REMARKS tc DESIGN SUBBASIN(s) Area C Length Slope ti Length Slope n Vel. tt tc = Total L tc=(l/180)+10 POINT (ac) (ft) (%) (min) (ft) (%) Manning (ft/s) (min) ti + tt (ft) (min) (min) (1) (2) (3) (4) (5) (6) (7) (8) rough. (9) (10) (11) (12) (13) (14) 1 1 0.53 0.95 25 2.5 1.0 270 1.0 0.016 2.0 2.24 3.2 295 11.6 5.0 2 2 0.43 0.95 25 2.0 1.1 270 1.0 0.016 2.0 2.30 3.4 295 11.6 5.0 3 3 1.20 0.95 138 1.0 3.2 265 1.0 0.016 2.0 2.26 5.4 403 12.2 5.4 4 4 0.20 0.20 15 15.0 2.5 100 1.5 0.030 1.3 1.27 3.8 115 10.6 5.0 5 5 0.47 0.88 70 2.5 2.5 140 0.6 0.016 1.6 1.50 4.0 210 11.2 5.0 6 6 0.14 0.92 56 2.0 1.9 90 1.2 0.016 2.2 0.68 2.6 146 10.8 5.0 7 7A 0.15 0.29 12 2.5 3.7 0 1.0 0.030 1.1 0.00 3.7 12 10.1 5.0 7 7B 0.10 0.25 30 4.0 5.3 0 1.0 0.030 1.1 0.00 5.3 30 10.2 5.3 OS1 OS1 (Lot 6) 0.47 0.50 30 0.8 6.4 145 0.6 0.020 1.2 1.94 8.3 175 11.0 8.3 All to Pond 2.98 0.89 138 1.0 4.5 265 1.0 0.016 2.0 2.20 6.7 403 12.2 6.7 Total 3.23 0.84 Historic 124 0.40 0.36 30 1.6 6.2 0 1.0 0.020 1.6 0.00 6.2 30 10.2 6.2 Historic 624 2.83 0.29 219 1.6 18.5 160 1.9 0.020 2.2 1.21 19.7 379 12.1 12.1 EQUATIONS: tc = ti + tt ti = [1.87 (1.1 - CCf ) L0.5 ] / S 1/3 tt = L/Vel. Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual) final tc = minimum of ti + tt and urbanized basin check min. tc = 5 minutes TIME (ti) TRAVEL TIME / GUTTER OR CHANNEL FLOW (tt) tc CHECK (URBANIZED BASIN) STANDARD FORM SF-2 TIME OF CONCENTRATION - 2 YEAR SUB-BASIN DATA INITIAL /OVERLAND Flow_REV.xls TOC-2 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: Affordable Storage PROJECT NO: 177-06 COMPUTATIONS BY: ppk DATE: 2/12/2018 100-yr storm Cf = 1.25 FINAL REMARKS tc DESIGN SUBBASIN(s) Area C C*Cf Length Slope ti Length Slope n Vel. tt tc = Total L tc=(l/180)+10 POINT (ac) (ft) (%) (min) (ft) (%) Manning (ft/s) (min) ti + tt (ft) (min) (min) (1) (2) (3) (4) (5) (6) (7) (8) rough. (9) (10) (11) (12) (13) (14) 1 1 0.53 0.95 1.00 25 2.5 0.7 270 1.0 0.016 2.0 2.24 2.9 295 11.6 5.0 2 2 0.43 0.95 1.00 25 2.0 0.7 270 1.0 0.016 2.0 2.30 3.0 295 11.6 5.0 3 3 1.20 0.95 1.00 138 1.0 2.1 265 1.0 0.016 2.0 2.26 4.4 403 12.2 5.0 4 4 0.20 0.20 0.25 15 15.0 2.4 100 1.5 0.030 1.3 1.27 3.7 115 10.6 5.0 5 5 0.47 0.88 1.00 70 2.5 1.1 140 0.6 0.016 1.6 1.50 2.6 210 11.2 5.0 6 6 0.14 0.92 1.00 56 2.0 1.1 90 1.2 0.016 2.2 0.68 1.8 146 10.8 5.0 7 7A 0.15 0.29 0.36 12 2.5 3.4 0 1.0 0.030 1.1 0.00 3.4 12 10.1 5.0 7 7B 0.10 0.25 0.31 30 4.0 4.9 0 1.0 0.030 1.1 0.00 4.9 30 10.2 5.0 OS1 OS1 (Lot 6) 0.47 0.50 0.62 30 0.8 5.0 145 0.6 0.020 1.2 1.94 7.0 175 11.0 7.0 All to Pond 2.98 0.89 1.00 138 1.0 2.1 265 1.0 0.016 2.0 2.20 4.3 403 12.2 5.0 Total 3.23 0.84 1.00 0 Historic 124 0.40 0.36 0.45 30 1.6 5.5 0 1.0 0.020 1.6 0.00 5.5 30 10.2 5.5 0 Historic 624 2.83 0.29 0.36 219 1.6 16.9 160 1.9 0.020 2.2 1.21 18.1 379 12.1 12.1 EQUATIONS: tc = ti + tt ti = [1.87 (1.1 - CCf ) L 0.5 ] / S 1/3 tt = L/Vel. Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual) final tc = minimum of ti + tt and urbanized basin check min. tc = 5 minutes TIME OF CONCENTRATION - 100 YR STANDARD FORM SF-2 SUB-BASIN DATA TIME (ti) INITIAL /OVERLAND TRAVEL TIME / GUTTER OR CHANNEL FLOW (tt) tc CHECK (URBANIZED BASIN) Flow_REV.xls TOC-100 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 RATIONAL METHOD PEAK RUNOFF (2-YEAR) LOCATION: Affordable Storage PROJECT NO: 177-06 COMPUTATIONS BY: ppk DATE: 2/22/2019 2-yr storm, Cf = 1.00 TOTAL REMARKS Design Tributary A C*Cf tc i Q (2) from Q (2) Q(2)tot Sub-basin (new) Design Point (ac) (min) (in/hr) (cfs) Point (cfs) (cfs) 1 1 0.53 0.95 5.0 2.85 1.4 1.4 To Inlet 1-1 2 2 0.43 0.95 5.0 2.85 1.2 1.2 To Inlet 1-2 3 3 1.20 0.95 5.4 2.77 3.2 3.2 To Inlet 1-3 4 4 0.20 0.20 5.0 2.85 0.1 0.1 To Inlet 3-1 and 3-2 5 5 0.47 0.88 5.0 2.85 1.2 1.2 To Inlet 2-1 & 2-2 6 6 0.14 0.92 5.0 2.85 0.4 0.4 To Inlet 3-3 7 7A 0.15 0.29 5.0 2.85 0.1 0.1 To Street 7 7B 0.10 0.25 5.3 2.80 0.1 0.1 To Street OS1 OS1 (Lot 6) 0.47 0.50 8.3 2.25 0.5 0.5 To 12" pipe All to Pond 2.98 0.89 6.7 2.54 6.7 Total 3.23 0.84 Historic 124 0.40 0.36 6.2 2.64 0.4 0.38 To Existing Pond Historic 624 2.83 0.29 12.1 2.05 1.7 1.67 To Existing Pond Q = Cf C iA Q = peak discharge (cfs) C = runoff coefficient Cf = frequency adjustment factor i = rainfall intensity (in/hr) from IDF curve A = drainage area (acres) DIRECT RUNOFF CARRY OVER Flow_REV.xls Q2 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 RATIONAL METHOD PEAK RUNOFF (100-YEAR) LOCATION: Affordable Storage PROJECT NO: 177-06 COMPUTATIONS BY: ppk DATE: 2/22/2019 100-yr storm, Cf = 1.25 TOTAL REMARKS Des. Area A C*Cf tc i Q (100) from Q (100) Q(100)tot (new) Design Point Design. (ac) (min) (in/hr) (cfs) Point (cfs) (cfs) 1 1 0.53 1.00 5.0 9.95 5.3 5.3 To Inlet 1-1 2 2 0.43 1.00 5.0 9.95 4.3 4.3 To Inlet 1-2 3 3 1.20 1.00 5.0 9.95 11.9 11.9 To Inlet 1-3 4 4 0.20 0.25 5.0 9.95 0.5 0.5 To Inlet 3-1 and 3-2 5 5 0.47 1.00 5.0 9.95 4.7 4.7 To Inlet 2-1 & 2-2 6 6 0.14 1.00 5.0 9.95 1.4 1.4 To Inlet 3-3 7 7A 0.15 0.36 5.0 9.95 0.5 0.5 To Street 7 7B 0.10 0.31 5.0 9.95 0.3 0.3 To Street OS1 OS1 (Lot 6) 0.47 0.62 7.0 8.68 2.5 2.5 To 12" pipe All to Pond 2.98 1.00 5.0 9.95 29.6 29.6 Total 3.23 1.00 5.0 9.95 32.1 32.1 0 Historic 124 0.40 0.45 5.5 9.63 1.73 1.73 To Existing Pond 0 Historic 624 2.83 0.36 12.1 7.14 7.3 7.26 To Existing Pond Q = C iA Q = peak discharge (cfs) C = runoff coefficient I = rainfall intensity (in/hr) from IDF curve A = drainage area (acres) DIRECT RUNOFF CARRY OVER Flow_REV.xls Q100 C APPENDIX C HYDRAULIC SIZING CALCULATIONS 0.00 56.50 113.00 169.50 226.00 282.50 339.00 395.50 452.00 508.50 565.00 65.80 66.60 67.40 68.20 69.00 69.80 70.60 71.40 72.20 73.00 HGL EGL Program: UDSEWER Math Model Interface 2.1.1.4 Run Date: 3/26/2018 11:12:02 AM UDSewer Results Summary Project Title: Affordable Storage Offsite Project Description: OS1 System Input Summary Rainfall Parameters Rainfall Return Period: 100 Rainfall Calculation Method: Formula One Hour Depth (in): 9.60 Rainfall Constant "A": 28.5 Rainfall Constant "B": 10 Rainfall Constant "C": 0.786 Rational Method Constraints Minimum Urban Runoff Coeff.: 0.20 Maximum Rural Overland Len. (ft): 500 Maximum Urban Overland Len. (ft): 300 Used UDFCD Tc. Maximum: Yes Sizer Constraints Minimum Sewer Size (in): 8.00 Maximum Depth to Rise Ratio: 0.90 Maximum Flow Velocity (fps): 18.0 Minimum Flow Velocity (fps): 2.0 Backwater Calculations: Tailwater Elevation (ft): 67.00 Manhole Input Summary: Given Flow Sub Basin Information Element Name Ground Elevation (ft) Total Known Flow (cfs) Local Contribution (cfs) Drainage Area (Ac.) Runoff Coefficient 5yr Coefficient Overland Length (ft) Overland Slope (%) Gutter Length (ft) Gutter Velocity (fps) Manhole Output Summary: Local Contribution Total Design Flow Element Name Overland Time (min) Gutter Time (min) Basin Tc (min) Intensity (in/hr) Local Contrib (cfs) Coeff. Area Intensity (in/hr) Manhole Tc (min) Peak Flow (cfs) Comment OUTFALL 1 0.00 0.00 0.00 0.00 0.00 0.06 42.72 0.62 2.50 Storm OS4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.50 Storm OS3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.50 Storm OS2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.50 Storm OS1 0.00 0.00 0.00 0.00 2.50 0.00 0.00 0.00 2.50 Sewer Input Summary: Elevation Loss Coefficients Given Dimensions Element Name Sewer Length (ft) Downstream Invert (ft) Slope (%) Upstream Invert (ft) Mannings n Bend Loss Lateral Loss Cross Section Rise (ft or in) Span (ft or in) Storm OS4 118.40 66.50 0.6 67.21 0.015 0.03 0.00 CIRCULAR 12.00 in 12.00 in than the suggested height. Existing width is smaller than the suggested width. Exceeds max. Depth/Rise Storm OS2 2.50 CIRCULAR 12.00 in 12.00 in 15.00 in 15.00 in 12.00 in 12.00 in 0.79 Existing height is smaller than the suggested height. Existing width is smaller than the suggested width. Exceeds max. Depth/Rise Storm OS1 2.50 CIRCULAR 12.00 in 12.00 in 12.00 in 12.00 in 12.00 in 12.00 in 0.79 Calculated diameter was determined by sewer hydraulic capacity rounded up to the nearest commercially available size. Sewer sizes should not decrease downstream. All hydraulics where calculated using the 'Used' parameters. Grade Line Summary: Tailwater Elevation (ft): 67.00 Invert Elev. Downstream Manhole Losses HGL EGL Element Name Downstream (ft) Upstream (ft) Bend Loss (ft) Lateral Loss (ft) Downstream (ft) Upstream (ft) Downstream (ft) Friction Loss (ft) Upstream (ft) Storm OS4 66.50 67.21 0.00 0.00 67.50 68.27 67.66 0.77 68.43 Storm OS3 67.21 68.99 0.01 0.00 68.28 70.21 68.44 1.93 70.37 Storm OS2 68.99 69.69 0.01 0.00 70.22 70.98 70.38 0.76 71.14 Storm OS1 69.69 70.00 0.01 0.00 70.99 71.21 71.14 0.22 71.37 Bend and Lateral losses only apply when there is an outgoing sewer. The system outfall, sewer #0, is not considered a sewer. Bend loss = Bend K * V_fi ^ 2/(2*g) Lateral loss = V_fo ^ 2/(2*g)- Junction Loss K * V_fi ^ 2/(2*g). Friction loss is always Upstream EGL - Downstream EGL. Excavation Estimate: The trench side slope is 1.0 ft/ft The minimum trench width is 2.00 ft Downstream Upstream Element Name Length (ft) Wall (in) 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 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 1.10 Capacity (cfs) Head (ft) Nyloplast 2' x 3' Road & Highway Grate Inlet Capacity Chart 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 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 1.10 Capacity (cfs) Head (ft) Nyloplast 2' x 3' Road & Highway Grate Inlet Capacity Chart 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 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 1.10 Capacity (cfs) Head (ft) Nyloplast 2' x 3' Road & Highway Grate Inlet Capacity Chart 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 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 1.10 Capacity (cfs) Head (ft) Nyloplast 2' x 3' Curb Inlet High Flow Grate Inlet Capacity Chart High Hood Setting (8.47" Curb Setting) Mid Hood Setting (6.47" Curb Setting) Low Hood Setting (4.47" Curb Setting) Manhole Input Summary: Given Flow Sub Basin Information Element Name Ground Elevation (ft) Total Known Flow (cfs) Local Contribution (cfs) Drainage Area (Ac.) Runoff Coefficient 5yr Coefficient Overland Length (ft) Overland Slope (%) Gutter Length (ft) Gutter Velocity (fps) OUTFALL 1 71.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Inlet 2-2 71.00 4.70 2.35 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Inlet 2-1 71.27 2.35 2.35 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Manhole Output Summary: Local Contribution Total Design Flow Element Name Overland Time (min) Gutter Time (min) Basin Tc (min) Intensity (in/hr) Local Contrib (cfs) Coeff. Area Intensity (in/hr) Manhole Tc (min) Existing Calculated Used Element Name Peak Flow (cfs) Cross Section Rise Span Rise Span Rise Span Area (ft^2) Comment Inlet 2-2 4.70 CIRCULAR 15.00 in 15.00 in 15.00 in 15.00 in 15.00 in 15.00 in 1.23 Inlet 2-1 2.35 CIRCULAR 15.00 in 15.00 in 12.00 in 12.00 in 15.00 in 15.00 in 1.23 Calculated diameter was determined by sewer hydraulic capacity rounded up to the nearest commercially available size. Sewer sizes should not decrease downstream. All hydraulics where calculated using the 'Used' parameters. Grade Line Summary: Tailwater Elevation (ft): 66.00 Invert Elev. Downstream Manhole Losses HGL EGL Element Name Downstream (ft) Upstream (ft) Bend Loss (ft) Lateral Loss (ft) Downstream (ft) Upstream (ft) Downstream (ft) Friction Loss (ft) Upstream (ft) Inlet 2-2 66.88 67.04 0.00 0.00 67.57 67.92 68.28 0.04 68.32 Inlet 2-1 67.04 68.50 0.00 0.00 68.27 69.11 68.33 1.03 69.35 Bend and Lateral losses only apply when there is an outgoing sewer. The system outfall, sewer #0, is not considered a sewer. Bend loss = Bend K * V_fi ^ 2/(2*g) Lateral loss = V_fo ^ 2/(2*g)- Junction Loss K * V_fi ^ 2/(2*g). Friction loss is always Upstream EGL - Downstream EGL. 0.00 11.20 22.40 33.60 44.80 56.00 67.20 78.40 89.60 100.80 112.00 66.44 66.94 67.44 67.94 68.44 68.94 69.44 69.94 70.44 70.94 HGL EGL D APPENDIX D DETENTION SYSTEM SIZING CALCULATIONS MINIMUM DETENTION VOLUME REQUIRED FAA METHOD (100-YEAR) LOCATION: Affordable Storage PROJECT NO: 177-10 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 1/21/2019 Equations: A trib. To pond = 2.98 acre QD = CiA C100 = 1.00 Vi = T*CiA = T*QD Developed C*A = 3.0 acre Vo =K*QPO*T QPO = 1.50 cfs S = Vi - Vo K = 1 (from fig 2.1) Rainfall intensity from City of Fort Collins IDF Curve Storm Rainfall QD Vol. In Vol. Out Storage Storage Duration, T Intensity, i (cfs) Vi Vo SS (min) (in/hr) (ft3) (ft3) (ft3) (ac-ft) 5 9.95 29.7 8895 451 8444 0.194 10 7.72 23.0 13803 902 12901 0.296 20 5.60 16.7 20026 1805 18221 0.418 30 4.52 13.5 24245 2707 21538 0.494 40 3.74 11.1 26748 3610 23139 0.531 50 3.23 9.6 28876 4512 24364 0.559 60 2.86 8.5 30682 5414 25268 0.580 70 2.62 7.8 32792 6317 26475 0.608 80 2.38 7.1 34044 7219 26824 0.616 90 2.22 6.6 35724 8122 27603 0.634 100 2.05 6.1 36654 9024 27630 0.634 110 1.93 5.8 37959 9926 28033 0.644 120 1.80 5.4 38621 10829 27792 0.638 130 1.60 4.8 37190 11731 25459 0.584 140 1.40 4.2 35045 12634 22411 0.514 150 1.20 3.6 32184 13536 18648 0.428 160 1.15 3.4 32899 14438 18461 0.424 170 1.10 3.3 33436 15341 18095 0.415 180 1.05 3.1 33793 16243 17550 0.403 Required Storage Volume: 28033 ft3 0.644 acre-ft Project: Chamber Model - SC-740 Units - Imperial Number of chambers - 346 Voids in the stone (porosity) - 40 % Base of STONE Elevation - 4966.00 ft Amount of Stone Above Chambers - 6 in Amount of Stone Below Chambers - 6 in Area of system - 14934 sf Min. Area - Height of System Incremental Single Chamber Incremental Total Chamber Incremental Stone Incremental Ch & St Cumulative Chamber Elevation (inches) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (feet) 42 0.00 0.00 497.80 497.80 30446.99 4969.50 41 0.00 0.00 497.80 497.80 29949.19 4969.42 40 0.00 0.00 497.80 497.80 29451.39 4969.33 39 0.00 0.00 497.80 497.80 28953.59 4969.25 38 0.00 0.00 497.80 497.80 28455.79 4969.17 37 0.00 0.00 497.80 497.80 27957.99 4969.08 36 0.05 19.03 490.19 509.22 27460.19 4969.00 35 0.16 56.37 475.25 531.62 26950.98 4968.92 34 0.28 97.55 458.78 556.33 26419.36 4968.83 33 0.60 208.97 414.21 623.18 25863.02 4968.75 32 0.80 277.39 386.84 664.24 25239.84 4968.67 31 0.95 328.93 366.23 695.16 24575.61 4968.58 30 1.07 371.78 349.09 720.87 23880.45 4968.50 29 1.18 408.45 334.42 742.87 23159.58 4968.42 28 1.27 437.92 322.63 760.55 22416.71 4968.33 27 1.36 468.83 310.27 779.10 21656.16 4968.25 26 1.45 503.12 296.55 799.67 20877.06 4968.17 25 1.52 527.56 286.78 814.33 20077.39 4968.08 24 1.58 547.48 278.81 826.29 19263.05 4968.00 23 1.64 568.23 270.51 838.74 18436.76 4967.92 22 1.70 588.03 262.59 850.62 17598.02 4967.83 21 1.75 606.51 255.19 861.71 16747.40 4967.75 20 1.80 623.77 248.29 872.06 15885.70 4967.67 19 1.85 641.83 241.07 882.90 15013.63 4967.58 18 1.89 655.01 235.80 890.81 14130.73 4967.50 17 1.93 669.17 230.13 899.30 13239.93 4967.42 16 1.97 683.35 224.46 907.81 12340.63 4967.33 15 2.01 695.43 219.63 915.06 11432.82 4967.25 14 2.04 707.57 214.77 922.34 10517.76 4967.17 13 2.07 717.94 210.63 928.56 9595.42 4967.08 12 2.10 728.30 206.48 934.78 8666.86 4967.00 11 2.13 737.60 202.76 940.36 7732.08 4966.92 10 2.15 745.23 199.71 944.94 6791.72 4966.83 9 2.18 753.26 196.49 949.76 5846.78 4966.75 8 2.20 760.63 193.55 954.18 4897.02 4966.67 7 2.21 763.73 192.31 956.04 3942.84 4966.58 6 0.00 0.00 497.80 497.80 2986.80 4966.50 5 0.00 0.00 497.80 497.80 2489.00 4966.42 Detention Pond Outlet Sizing (100 yr event) LOCATION: Affordable Storage PROJECT NO: 177-10 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 1/21/2019 Submerged Orifice Outlet: release rate is described by the orifice equation, Qo = CoAo sqrt( 2g(h-Eo)) where Qo = orifice outflow (cfs) Co = orifice discharge coefficient g = gravitational acceleration = 32.2 ft/s Ao = effective area of the orifice (ft2) Eo = greater of geometric center elevation of the orifice or d/s HGL (ft) h = water surface elevation (ft) Qo = 1.50 cfs outlet pipe dia = D = 15.0 in Invert elev. = 4766.00 ft Eo = 4766.21 ft h = 4770.7 ft - 100 yr WSEL Co = 0.62 solve for effective area of orifice using the orifice equation Ao = 0.142 ft2 = 20.5 in2 orifice dia. = d = 5.11 in Check orifice discharge coefficient using Figure 5-21 (Hydraulic Engineering ) d / D = 0.34 kinematic viscosity, u = 1.22E-05 ft2/s Reynolds no. = Red = 4Q/(pdu) = 3.69E+05 Co = (K in figure) = 0.62 check Use d = 5.10 in A o = 0.142 ft 2 = 20.43 in 2 Q max = 1.50 cfs 12345678910 11 12 13 1415 Req'd Flow Chamber Chamber Chamber Ch. Volume Min # of Total Req'd Volume Min # of # of Chambers Storage Provided Storage Provided # of Isolator Depth to Basin # WQ Volume WQ Type Release Volume w/ Aggregate Chambers Release Rate FAA Method Chambers Req'd in Req'd Chambers in Chambers & Agg Chambers achieve (cf) (cfs) (cfs) (cf) (cf) incl. aggregate (cfs) (cf) chamb. only (Greater of Column 7 (cf) (cf) Provided Req'd (Column 1/ (Column 4* (Column 9/ or Column 10) (Column 5 * Column 11) (Column 6 * Column 11) Volume Column 6) Column 7) Column 5) (in) 1 688 0.72 SC-740 0.0236 45.9 74.9 10 0.24 343 8 10 459 749 14 24.5 2 558 0.58 SC-740 0.0236 45.9 74.9 8 0.19 281 7 8 367 599 14 20 3 & 6 1666 1.76 SC-740 0.0236 45.9 74.9 23 0.54 923 21 23 1056 1723 42 38.6 4 0 0.06 SC-740 0.0236 45.9 74.9 0 0.00 71 2 2 92 150 21 7.5 5 504 0.59 SC-740 0.0236 45.9 74.9 7 0.17 311 7 7 321 524 14 19 Entire System 2134 3.37 SC-740 0.0236 45.9 74.9 29 0.68 1928 26 29 1331 2172 105  StormTec Chamber Summary Table Information provided by StormTec WATER QUALITY VOLUME LOCATION: Affordable Storage PROJECT NO: 177-10 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 3/30/2018 From Urban Storm Drainage Criterial Manual Use: 12-hour drain time a=0.80 Required Storage = Water Quality Capture Volume = WQCV = [required storage] * [Area] 12 Trib. % Req. Storage WQCV WQCV WQ Flow area Imperv. from Fig. EDB-2 (To column 1) (To column 2) (ac) (in. of runoff) (ac-ft) (cu-ft) (cfs) 1 0.53 95 0.358 0.016 688 0.72 2 0.43 95 0.358 0.013 558 0.58 3 & 6 1.34 93 0.343 0.038 1666 1.76 4 0.20 0 0.000 0.000 0 0.06 5 0.47 86 0.296 0.012 504 0.59 TOTAL 2.98 63 0.197 0.049 2134 3.37 For all Flow to the Underground Storage Flow (WQ)= C*i/2*A= 0.89 * 2.54/2 * 2.98 = 3.37 cfs All Chambers are SC-740 Release rate = 0.0236 cfs Chamber volume = 45.9 cf Chamber volume with aggregate = 74.9 cf Minimum No. Chambers req'd = 2134 cf / 74.9 cf = 28.50 = 29 Chambers Total release rate = 29 * 0.0236 = 0.68 cfs a * [0.91 (i 3) - 1.19 (i 2) + 0.78(i)] BASIN 1 REQUIRED WATER QUALITY STORAGE VOLUME FAA METHOD LOCATION: Affordable Storage Basin 1 Equations: A trib. To pond = 0.53 acre QD = CiA C2 = 0.95 Vi = T*CiA = T*QD Developed C*A = 0.5 acre Vo =K*QPO*T QPO (from WQ Calculation)= 0.24 cfs S = Vi - Vo Rainfall intensity from City of Fort Collins IDF Curve Storm Rainfall QD Vol. In Outflow Vol. Out Storage Duration, T Intensity, i (cfs) Vi Adj Factor Vo S (min) (in/hr) (ft3) (ft3) (ft3) 5 1.43 0.7 215 1.00 71 144 10 1.11 0.6 334 1.00 142 192 20 0.81 0.4 486 0.63 178 308 30 0.65 0.3 589 0.58 246 343 40 0.54 0.3 646 0.56 317 329 50 0.46 0.2 695 0.55 389 305 60 0.41 0.2 743 0.54 459 284 70 0.37 0.2 772 0.54 535 237 80 0.33 0.2 798 0.53 600 197 90 0.31 0.2 829 0.53 675 154 100 0.28 0.1 846 0.53 750 95 110 0.26 0.1 864 0.52 810 54 120 0.25 0.1 888 0.52 884 5 Required Storage Volume: 343 ft3 To column 9 0.008 acre-ft Number of Chambers req'd = 2593 cf / 45.9 cf = 7.47 = 8 Chambers  To column 10 BASIN 2 REQUIRED WATER QUALITY STORAGE VOLUME FAA METHOD LOCATION: Affordable Storage Basin 2 Equations: A trib. To pond = 0.43 acre QD = CiA C2 = 0.95 Vi = T*CiA = T*QD Developed C*A = 0.4 acre Vo =K*QPO*T QPO (from WQ Calculation)= 0.19 cfs S = Vi - Vo Rainfall intensity from City of Fort Collins IDF Curve Storm Rainfall QD Vol. In Outflow Vol. Out Storage Duration, T Intensity, i (cfs) Vi Adj Factor Vo S (min) (in/hr) (ft3) (ft3) (ft3) 5 1.43 0.6 175 1.00 57 118 10 1.11 0.5 271 1.00 113 158 20 0.81 0.3 395 0.63 143 252 30 0.65 0.3 478 0.58 197 281 40 0.54 0.2 525 0.56 254 271 50 0.46 0.2 564 0.55 312 252 60 0.41 0.2 603 0.54 367 236 70 0.37 0.1 626 0.54 428 198 80 0.33 0.1 647 0.53 480 167 90 0.31 0.1 673 0.53 540 132 100 0.28 0.1 686 0.53 600 86 110 0.26 0.1 701 0.52 648 53 120 0.25 0.1 721 0.52 707 14 Required Storage Volume: 281 ft3 <-- To column 9 0.006 acre-ft Number of Chambers req'd = 2593 cf / 45.9 cf = 6.12 = 7 Chambers  To column 10 BASIN 3 & 6 REQUIRED WATER QUALITY STORAGE VOLUME FAA METHOD LOCATION: Affordable Storage Basins 3 & 6 Combined Equations: A trib. To pond = 1.34 acre QD = CiA C2 = 0.95 Vi = T*CiA = T*QD Developed C*A = 1.3 acre Vo =K*QPO*T QPO (from WQ Calculation)= 0.54 cfs S = Vi - Vo Rainfall intensity from City of Fort Collins IDF Curve Storm Rainfall QD Vol. In Outflow Vol. Out Storage Duration, T Intensity, i (cfs) Vi Adj Factor Vo S (min) (in/hr) (ft3) (ft3) (ft3) 5 1.43 1.8 544 1.00 163 381 10 1.11 1.4 844 1.00 326 518 20 0.81 1.0 1230 0.63 410 819 30 0.65 0.8 1489 0.58 567 923 40 0.54 0.7 1635 0.56 730 905 50 0.46 0.6 1757 0.55 896 861 60 0.41 0.5 1879 0.54 1055 824 70 0.37 0.5 1952 0.54 1231 720 80 0.33 0.4 2016 0.53 1381 636 90 0.31 0.4 2097 0.53 1553 543 100 0.28 0.4 2139 0.53 1726 413 110 0.26 0.3 2184 0.52 1863 322 120 0.25 0.3 2246 0.52 2032 213 Required Storage Volume: 923 ft3 <-- To column 9 0.021 acre-ft Number of Chambers req'd = 2593 cf / 45.9 cf = 20.10 = 21 Chambers  To column 10 BASIN 4 REQUIRED WATER QUALITY STORAGE VOLUME FAA METHOD LOCATION: Affordable Storage Basin 4 Equations: A trib. To pond = 0.20 acre QD = CiA C2 = 0.20 Vi = T*CiA = T*QD Developed C*A = 0.04 acre Vo =K*QPO*T QPO (from WQ Calculation)= 0.02 cfs S = Vi - Vo Rainfall intensity from City of Fort Collins IDF Curve Storm Rainfall QD Vol. In Outflow Vol. Out Storage Duration, T Intensity, i (cfs) Vi Adj Factor Vo S (min) (in/hr) (ft3) (ft3) (ft3) 5 1.43 0.1 17 1.00 7 10 10 1.11 0.0 27 1.00 14 12 20 0.81 0.0 39 0.63 18 21 30 0.65 0.0 47 0.58 25 22 40 0.54 0.0 51 0.56 32 20 50 0.46 0.0 55 0.55 39 16 60 0.41 0.0 59 0.54 46 13 70 0.37 0.0 61 0.54 54 8 80 0.33 0.0 63 0.53 60 3 90 0.31 0.0 66 0.53 68 -2 100 0.28 0.0 67 0.53 75 -8 110 0.26 0.0 69 0.52 81 -12 120 0.25 0.0 71 0.52 88 -18 Required Storage Volume: 22 ft3 <-- To column 9 0.001 acre-ft Number of Chambers req'd = 2593 cf / 45.9 cf = 0.48 = 2 Chambers  To column 10 BASIN 5 REQUIRED WATER QUALITY STORAGE VOLUME FAA METHOD LOCATION: Affordable Storage Basin 5 Equations: A trib. To pond = 0.47 acre QD = CiA C2 = 0.88 Vi = T*CiA = T*QD Developed C*A = 0.4 acre Vo =K*QPO*T QPO (from WQ Calculation)= 0.17 cfs S = Vi - Vo Rainfall intensity from City of Fort Collins IDF Curve Storm Rainfall QD Vol. In Outflow Vol. Out Storage Duration, T Intensity, i (cfs) Vi Adj Factor Vo S (min) (in/hr) (ft3) (ft3) (ft3) 5 1.43 0.6 177 1.00 50 127 10 1.11 0.5 274 1.00 99 175 20 0.81 0.3 400 0.63 125 275 30 0.65 0.3 484 0.58 172 311 40 0.54 0.2 531 0.56 222 309 50 0.46 0.2 571 0.55 273 298 60 0.41 0.2 610 0.54 321 289 70 0.37 0.2 634 0.54 375 259 80 0.33 0.1 655 0.53 420 235 90 0.31 0.1 681 0.53 473 208 100 0.28 0.1 695 0.53 525 170 110 0.26 0.1 710 0.52 567 143 120 0.25 0.1 730 0.52 619 111 Required Storage Volume: 311 ft3 <-- To column 9 0.007 acre-ft Number of Chambers req'd = 2593 cf / 45.9 cf = 6.79 = 7 Chambers  To column 10 Stormwater Facility Name: Facility Location & Jurisdiction: User (Input) Watershed Characteristics User Defined User Defined User Defined User Defined Watershed Slope = 0.008 ft/ft Stage [ft] Area [ft^2] Stage [ft] Discharge [cfs] Watershed Length‐to‐Width Ratio = 1.00 L:W 0.00 0 0.00 0.00 Watershed Area =2.97acres 0.50 2,882 0.50 0.46 Watershed Imperviousness = 86.0% percent 1.00 8,567 1.00 0.79 Percentage Hydrologic Soil Group A =0.0%percent 1.50 14,027 1.50 1.02 Percentage Hydrologic Soil Group B = 0.0% percent 2.00 19,141 2.00 1.21 Percentage Hydrologic Soil Groups C/D = 100.0% percent 2.50 24,406 2.50 1.37 3.00 27,220 3.00 1.44 User Input 17 3.50 30,102 3.50 1.50 User Input: Detention Basin Characteristics WQCV Design Drain Time = 12.00 hours After completing and printing this worksheet to a pdf, go to: https://maperture.digitaldataservices.com/gvh/?viewer=cswdif, create a new stormwater facility, and attach the pdf of this worksheet to that record. Routed Hydrograph Results Design Storm Return Period = WQCV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year One‐Hour Rainfall Depth = 0.53 0.98 1.36 1.71 2.31 2.91 3.67 in Calculated Runoff Volume = 0.072 0.207 0.300 0.388 0.544 0.699 0.901 acre‐ft OPTIONAL Override Runoff Volume = acre‐ft Inflow Hydrograph Volume = 0.072 0.207 0.299 0.388 0.543 0.698 0.901 acre‐ft Time to Drain 97% of Inflow Volume = 245 57810 hours Time to Drain 99% of Inflow Volume = 24567810 hours Maximum Ponding Depth = 0.69 1.23 1.50 1.71 2.04 2.33 2.66 ft Maximum Ponded Area = 0.116 0.253 0.320 0.371 0.449 0.518 0.580 acres Maximum Volume Stored = 0.034 0.133 0.209 0.285 0.419 0.558 0.741 acre‐ft Location for 1‐hr Rainfall Depths (use dropdown): Workbook Protected Worksheet Protected Stormwater Detention and Infiltration Design Data Sheet Affordable Storage Affordable Storage, Fort Collins, CO Det Pond Drain time check_FC_Rainfall.xlsm, Design Data 1/21/2019, 9:54 AM Doing_Clear_FoYes CountA= 1 0123 #N/A #N/A 0123 #N/A #N/A Check Data Set 1 Check Data Set 1 Area Discharge Stormwater Detention and Infiltration Design Data Sheet 0 5 10 15 20 25 0.1 1 10 FLOW [cfs] TIME [hr] 100YR IN 100YR OUT 50YR IN 50YR OUT 25YR IN 25YR OUT 10YR IN 10YR OUT 5YR IN 5YR OUT 2YR IN 2YR OUT WQCV IN WQCV OUT 0 0.5 1 1.5 2 2.5 3 0.1 1 10 100 PONDING DEPTH [ft] DRAIN TIME [hr] 100YR 50YR 25YR 10YR 5YR 2YR WQCV Det Pond Drain time check_FC_Rainfall.xlsm, Design Data 1/21/2019, 9:54 AM E APPENDIX E BMP SCHEDULE & COST ESTIMATE Project: Disturbed Acres: 3.23 EROSION CONTROL BMPs Units Estimated Quantity Unit Price Total Price L.F. 1430 $3.00 $4,290.00 each 7 $85.00 $595.00 each $180.00 $0.00 each 9 $255.00 $2,295.00 each 2 $1,500.00 $3,000.00 each 1 $1,200.00 $1,200.00 Sub-Total: $11,380.00 1.5 x Sub-Total: $17,070.00 Amount of security: $17,070.00 Total Acres x Price/acre: $3,876.00 $1,200.00 Sub-Total: $3,876.00 1.5 x Sub-Total: $5,814.00 Amount to Re-seed: $5,814.00 Minimum escrow amount: $3,000.00 Erosion Control Escrow: $17,070.00 Erosion and Sediment Control Escrow/Security Calculation for The City of Fort Collins BMP Amount Silt Fence Concrete Washout Reseeding Amount Rock Berm Inlet Protection Miniumum Escrow Amount Affordable Storage Unit Price of Seeding per acre: “The amount of the security must be based on one and one-half times the estimate of the cost to install the approved measures, or one and one-half times the cost to re-vegetate the disturbed land to dry land grasses based upon unit cost determined by the City's Annual Revegetation and Stabilization Bid, whichever is greater. In no instance, will the amount of security be less than one thousand five hundred dollars ($1,500) for residential development or three thousand dollars ($3,000) for commercial development” Rock Sock Vehicle Tracking Control Pad Final Escrow Amount 12/18/2017 12:32 PM N:\177-10 Affordable Storage\drainage\FC Escrow.xls F APPENDIX F EXCERPTS FROM PREVIOUS REPORTS This unofficial copy was downloaded on Mar-22-2017 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 Mar-22-2017 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 Mar-22-2017 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 Mar-22-2017 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 Mar-22-2017 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 Mar-22-2017 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 Mar-22-2017 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 Mar-22-2017 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 G APPENDIX G FIGURES AND TABLES 34 Table RA-8 -- City of Fort Collins Rainfall Intensity-Duration-Frequency Table for Use with the Rational Method (31 minutes to 60 minutes) 2-Year 10-Year 100-Year Duration (min) Intensity (in/hr) Intensity (in/hr) Intensity (in/hr) 31 1.27 2.16 4.42 32 1.24 2.12 4.33 33 1.22 2.08 4.24 34 1.19 2.04 4.16 35 1.17 2.0 4.08 36 1.15 1.96 4.01 37 1.16 1.93 3.93 38 1.11 1.89 3.87 39 1.09 1.86 3.8 40 1.07 1.83 3.74 41 1.05 1.8 3.68 42 1.04 1.77 3.62 43 1.02 1.74 3.56 44 1.01 1.72 3.51 45 0.99 1.69 3.46 46 0.98 1.67 3.41 47 0.96 1.64 3.36 48 0.95 1.62 3.31 49 0.94 1.6 3.27 50 0.92 1.58 3.23 51 0.91 1.56 3.18 52 0.9 1.54 3.14 53 0.89 1.52 3.1 54 0.88 1.5 3.07 55 0.87 1.48 3.03 56 0.86 1.47 2.99 57 0.85 1.45 2.96 58 0.84 1.43 2.92 59 0.83 1.42 2.89 60 0.82 1.4 2.86 36 RAINFALL INTENSITY-DURATION-FREQUENCY CURVE 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 0.00 10.00 20.00 30.00 40.00 50.00 60.00 STORM DURATION (minutes) RAINFALL INTENSITY (inches/hour) 2-Year Storm 10-Year Storm 100-Year Storm Figure RA-16 City of Fort Collins Rainfall Intensity-Duration-Frequency Curves (13) Section 5.0 is deleted in its entirety. (14) Section 6.0 is deleted in its entirety. (15) Section 7.0 is deleted in its entirety. (16) Section 7.1 is deleted in its entirety. (17) Section 7.2 is deleted in its entirety. (18) Section 7.3 is deleted in its entirety. (19) Section 8.0 is deleted in its entirety. (20) Table RA-1 is deleted in its entirety. 40 Table RO-10 Rational Method Minor Storm Runoff Coefficients for Zoning Classifications Description of Area or Zoning Coefficient R-F 0.3 U-E 0.3 L-M-In 0.55 R-L, N-C-L 0.6 M-M-N, N-C-M 0.65 N-C-B 0.7 Business: C-C-N, C-C-R, C-N, N-C, C-S 0.95 R-D-R, C-C, C-L 0.95 D, C 0.95 H-C 0.95 C-S 0.95 Industrial: E 0.85 I 0.95 Undeveloped: R-C, T 0.2 P-O-L 0.25 For guidance regarding zoning districts and classifications of such districts please refer to Article Four of the City Land Use Code, as amended. 41 Table RO-11 Rational Method Runoff Coefficients for Composite Analysis Character of Surface Runoff Coefficient Streets, Parking Lots, Drives: Asphalt 0.95 Concrete 0.95 Gravel 0.5 Roofs 0.95 Recycled Asphalt 0.8 Lawns, Sandy Soil: Flat <2% 0.1 Average 2 to 7% 0.15 Steep >7% 0.2 Lawns, Heavy Soil: Flat <2% 0.2 Average 2 to 7% 0.25 Steep >7% 0.35 (4) A new Section 2.9 is added, to read as follows: 2.9 Composite Runoff Coefficient Drainage sub-basins are frequently composed of land that has multiple surfaces or zoning classifications. In such cases a composite runoff coefficient must be calculated for any given drainage sub-basin. The composite runoff coefficient is obtained using the following formula: ( ) t n i i i A C A C ∑ = = 1 * (RO-8) Where: C = Composite Runoff Coefficient Ci = Runoff Coefficient for Specific Area (Ai) Ai = Area of Surface with Runoff Coefficient of Ci, acres or feet2 n = Number of different surfaces to be considered At = Total Area over which C is applicable, acres or feet2 (5) A new Section 2.10 is added, to read as follows: 42 2.10 Runoff Coefficient Adjustment for Infrequent Storms The runoff coefficients provided in tables RO-10 and RO-11 are appropriate for use with the 2-year storm event. For storms with higher intensities, an adjustment of the runoff coefficient is required due to the lessening amount of infiltration, depression retention, evapo-transpiration and other losses that have a proportionally smaller effect on storm runoff. This adjustment is applied to the composite runoff coefficient. These frequency adjustment factors are found in Table RO-12. Table RO-12 Rational Method Runoff Coefficients for Composite Analysis Storm Return Period (years) Frequency Factor Cf 2 to 10 11 to 25 26 to 50 51 to 100 1.00 1.10 1.20 1.25 Note: The product of C times Cf cannot exceed the value of 1, in the cases where it does a value of 1 must be used (6) Section 3.1 is deleted in its entirety. (7) Section 3.2 is deleted in its entirety. (8) Section 3.3 is deleted in its entirety. (9) A new Section 4.3 is added, to read as follows: 4.3 Computer Modeling Practices (a) For circumstances requiring computer modeling, the design storm hydrographs must be determined using the Stormwater Management Model (SWMM). Basin and conveyance element parameters must be computed based on the physical characteristics of the site. (b) Refer to the SWMM Users’ Manual for appropriate modeling methodology, practices and development. The Users’ Manual can be found on the Environmental Protection Agency (EPA) website (http://www.epa.gov/ednnrmrl/models/swmm/index.htm). (c) It is the responsibility of the design engineer to verify that all of the models used in the design meet all current City criteria and regulations. 4.3.1 Surface Storage, Resistance Factors, and Infiltration Table RO-13 provides values for surface storage for pervious and impervious surfaces and the infiltration rates to be used with SWMM. Table RO-13 also lists the appropriate infiltration decay rate, zero detention depth and resistance factors, or Manning’s “n” values, for pervious and impervious surfaces to be used for SWMM modeling in the city of Fort Collins. 4 0.00 0.00 497.80 497.80 1991.20 4966.33 3 0.00 0.00 497.80 497.80 1493.40 4966.25 2 0.00 0.00 497.80 497.80 995.60 4966.17 1 0.00 0.00 497.80 497.80 497.80 4966.08 AFFORDABLE SELF STORAGE 11696 sf min. area StormTech SC-740 Cumulative Storage Volumes Include Perimeter Stone in Calculations Click Here for Metric Peak Flow (cfs) Comment OUTFALL 1 0.00 0.00 0.00 0.00 0.00 0.11 44.20 0.03 4.70 Inlet 2-2 0.00 0.00 0.00 0.00 2.35 0.00 0.00 0.00 4.70 Inlet 2-1 0.00 0.00 0.00 0.00 2.35 0.00 0.00 0.00 2.35 Sewer Input Summary: Elevation Loss Coefficients Given Dimensions Element Name Sewer Length (ft) Downstream Invert (ft) Slope (%) Upstream Invert (ft) Mannings n Bend Loss Lateral Loss Cross Section Rise (ft or in) Span (ft or in) Inlet 2-2 8.00 66.88 2.0 67.04 0.015 0.03 0.00 CIRCULAR 15.00 in 15.00 in Inlet 2-1 104.40 67.04 1.4 68.50 0.015 0.05 0.00 CIRCULAR 15.00 in 15.00 in Sewer Flow Summary: Full Flow Capacity Critical Flow Normal Flow Element Name Flow (cfs) Velocity (fps) Depth (in) Velocity (fps) Depth (in) Velocity (fps) Froude Number Flow Condition Flow (cfs) Surcharged Length (ft) Comment Inlet 2-2 7.94 6.47 10.55 5.10 8.30 6.74 1.59 Supercritical 4.70 0.00 Inlet 2-1 6.64 5.41 7.35 3.93 6.16 4.95 1.40 Supercritical 2.35 0.00 A Froude number of 0 indicates that pressured flow occurs (adverse slope or undersized pipe). If the sewer is not pressurized, full flow represents the maximum gravity flow in the sewer. If the sewer is pressurized, full flow represents the pressurized flow conditions. Sewer Sizing Summary: Bedding (in) Bottom Width (ft) Top Width (ft) Trench Depth (ft) Cover (ft) Top Width (ft) Trench Depth (ft) Cover (ft) Volume (cu. yd) Comment Storm OS4 118.40 2.00 4.00 4.33 5.44 3.22 1.55 4.33 2.51 0.84 47.11 Sewer Too Shallow Storm OS3 296.10 2.00 4.00 4.33 0.00 2.51 0.84 6.02 3.51 1.84 126.90 Sewer Too Shallow Storm OS2 116.60 2.00 4.00 4.33 6.02 3.51 1.84 5.62 3.31 1.64 66.24 Storm OS1 34.30 2.00 4.00 4.33 5.62 3.31 1.64 7.00 4.00 2.33 21.51 Total earth volume for sewer trenches = 262 cubic yards. The trench was estimated to have a bottom width equal to the outer pipe diameter plus 36 inches. If the calculated width of the trench bottom is less than the minimum acceptable width, the minimum acceptable width was used. The sewer wall thickness is equal to: (equivalent diameter in inches/12)+1 inches The sewer bedding thickness is equal to: Four inches for pipes less than 33 inches. Storm OS3 296.10 67.21 0.6 68.99 0.015 0.05 0.00 CIRCULAR 12.00 in 12.00 in Storm OS2 116.60 68.99 0.6 69.69 0.015 0.05 0.00 CIRCULAR 12.00 in 12.00 in Storm OS1 34.30 69.69 0.9 70.00 0.015 0.05 0.00 CIRCULAR 12.00 in 12.00 in Sewer Flow Summary: Full Flow Capacity Critical Flow Normal Flow Element Name Flow (cfs) Velocity (fps) Depth (in) Velocity (fps) Depth (in) Velocity (fps) Froude Number Flow Condition Flow (cfs) Surcharged Length (ft) Comment Storm OS4 2.40 3.05 12.00 3.18 12.00 3.18 0.00 Pressurized 2.50 118.40 Storm OS3 2.40 3.05 12.00 3.18 12.00 3.18 0.00 Pressurized 2.50 296.10 Storm OS2 2.40 3.05 12.00 3.18 12.00 3.18 0.00 Pressurized 2.50 116.60 Storm OS1 2.94 3.74 8.13 4.42 8.51 4.20 0.91 Pressurized 2.50 34.30 A Froude number of 0 indicates that pressured flow occurs (adverse slope or undersized pipe). If the sewer is not pressurized, full flow represents the maximum gravity flow in the sewer. If the sewer is pressurized, full flow represents the pressurized flow conditions. Sewer Sizing Summary: Existing Calculated Used Element Name Peak Flow (cfs) Cross Section Rise Span Rise Span Rise Span Area (ft^2) Comment Storm OS4 2.50 CIRCULAR 12.00 in 12.00 in 15.00 in 15.00 in 12.00 in 12.00 in 0.79 Existing height is smaller than the suggested height. Existing width is smaller than the suggested width. Exceeds max. Depth/Rise Storm OS3 2.50 CIRCULAR 12.00 in 12.00 in 15.00 in 15.00 in 12.00 in 12.00 in 0.79 Existing height is smaller OUTFALL 1 69.22 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Storm OS4 69.22 2.50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Storm OS3 72.00 2.50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Storm OS2 72.50 2.50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Storm OS1 73.50 2.50 2.50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 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 13, Sep 10, 2018 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Sep 20, 2015—Oct 21, 2017 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. Soil Map—Larimer County Area, Colorado (Affordable Storage site) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/21/2019 Page 2 of 3