Loading...
HomeMy WebLinkAboutAFFORDABLE SELF STORAGE - PDP - PDP170005 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTFINAL DRAINAGE AND EROSION CONTROL REPORT FOR AFFORDABLE STORAGE (LOT 9, BLOCK 4, EVERGREEN REPLAT 1) FINAL DRAINAGE AND EROSION CONTROL REPORT FOR AFFORDABLE STORAGE (LOT 9, BLOCK 4, EVERGREEN REPLAT 1) Prepared for: Affordable Storage Prepared by: North Star Design 700 Automation Drive, Unit I Windsor, Colorado 80550 (970) 686-6939 March 26, 2017 Job Number 177-10 ii March 26, 2017 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 Dear Dan, I am pleased to submit for your review and approval, this Final Drainage and Erosion Control Report for Affordable Storage (Lot 9, Block 4, Evergreen Replat 1). 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 .....................................................................................................7 5.2 SWMP Contact Information .................................................................................10 5.3 Identification and location of all potential pollution sources ................................11 5.4 Best Management Practices (BMP’s) for Stormwater Pollution Prevention .........11 5.5 Material Handling & Spill Prevention ...................................................................14 5.6 BMP Implementation .............................................................................................15 5.7 Soil Amendments, Permanent Seeding & Mulching .............................................16 6. CONCLUSIONS 6.1 Compliance with Standards ..................................................................................18 6.2 Drainage Concept ..................................................................................................18 7. REFERENCES ..................................................................................................................19 APPENDICES A Vicinity Map B Hydrologic Computations C Hydraulic & BMP Sizing Calculations D Detention Pond Sizing Calculations E BMP Schedule and Cost Estimate F Excerpts from Previous Reports G 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 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 and easement and an 8” diameter pipe for conveyance of the attenuated runoff from the east half of Lot 6. Proposed development on-site will include six storage buildings, private drives between 2 the buildings, a parking area and sidewalks. Existing drainage patterns will be altered to route flow to a proposed detention pond in the southeast corner of the site which will release into the existing storm system near this location. 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. 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 historic 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 flow 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 detention pond and be released at the composite release rate of 1.57 cfs into the storm system in Conifer. 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 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 water quality. The release rate from the site will be at the calculated composite release rate of 1.57 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 1.57 cfs. The FAA method for detention pond 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 detention pond. 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. An 8” pipe will also convey (future) detained runoff from Lot 6 to this 15” storm pipe and into the storm system in Conifer. 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 rain gardens to promote infiltration and biological uptake. 4  Routing flows through filter material in the rain gardens 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 rain gardens and then to a pond that will provide detention prior to release into the public storm system to 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 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 south into the detention pond. The runoff from the site will either flow on the surface or enter a storm pipe via an inlet. On-site runoff will also be conveyed to the detention pond via flows in Rain Garden #3 along the south 5 property boundary to an area inlet and storm pipe. 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 7 basins which described in the following paragraphs. 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 be collected in an area inlet. The storm pipe then conveys the flows to the south into the detention pond. Basin 2 is located in the central portion of the site. This Basin contains the middle drive aisle, a portion of Building E, 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 flow will be combined with the runoff from Basin 3 and then be directed south and into Rain Garden #1. The flow will then enter the detention pond. Basin 3 is located in the central portion of the site. This Basin contains the southmost drive aisle, a portion of Building E, the south half of Building B and the west half of Building F. The runoff from this basin will flow east in a concrete pan to the north-south drive aisle. The flow will be combined with the runoff from Basin 2 and then be directed south and into Rain Garden #1. The flow will then enter the detention pond. Basin 4 is located in the southern portion of the site. This Basin contains Building A and a landscape area south of Building A. The roof of Building A is sloped to drain to the south where the runoff will enter Rain Garden #3 in the landscape area. The flow will then be directed east where it will enter an area inlet and be directed to the detention pond. Basin 5 is located in the east portion of the site. This Basin contains the east drive aisle, the east half of Building E, a small portion of Building D, the trash enclosure and the east half of Building F. The runoff from this basin will flow south in a concrete curb to a curb 6 opening. The flow will then be directed south and into Rain Garden #2. The flow will then enter the detention pond. Basin 6 is located in the southeast portion of the site and contains the detention pond (landscape area). The the bottom of the detention area is sloped to drain southeast. This basin accepts runoff from Basins 1, 2, 3, 4 and 5. The detained runoff will enter the existing storm system via a new storm pipe with an orifice to restrict flows to 1.57 cfs. Basin 7 is the site area that drains 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. 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 700 square feet per City criteria. Drainage design for this site has been designed to convey on-site runoff to the proposed detention pond and incorporate the required LID enhancement features. On-site runoff will be conveyed to the detention pond via surface flow in the drive aisles, in the proposed storm system and subsurface in the perforated pipes. The detention pond will release the detained runoff from the site at the rate of 1.57 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 historic runoff (1.7 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 2.266 cfs but this rate was reduced by the free release from Basin 7 (0.7 cfs) giving a composite allowable detention release of 1.566 cfs. 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 detention pond while minimizing future maintenance. The site incorporates LID (Low Impact Development) treatment areas including three rain garden areas south of the proposed building and at the edge of the detention area. Rain Garden #1 treats runoff from Basins 2 and 3 which is a total of 0.93 acres, Rain Garden #2 treats runoff from Basin 5 which is a total of 0.24 acres and Rain 7 Garden #3 treats runoff from Basin 4 which is a total of 0.82 acres and a total of 1.99 acres of the site being treated in an LID system. The remainder of the site (1.24 acres) will not be treated. Refer to the end of Appendix E for a table indicating the size of each LID treatment area and the area of the site that drains to each LID treatment area. All drainage facilities proposed with this project, including the detention pond, LID features, area inlets, storm pipe and outlet structure are private and will be owned and maintained by the property owner. The pipe and the storm manhole in the right of way will be owned and maintained by the City of Fort Collins. The 8” pipe to be installed from Lot 6 to Conifer Street will be maintained by the owner of Lot 6. 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, 8 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. • 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 detention pond 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 9 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 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. 10 5.2 SWMP contact information Permit holder: Name: Address: Phone Number: Email Address: Appointed agent: Name: Address: Phone Number: Email Address: 11 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. 12 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 In the detention Pond X 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 13 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 14 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 15 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 16 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 detention 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 17 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. 18 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 detention area. Conveyance elements exist 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. 19 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 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: 3/27/2017 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 0.58 25060 13790 11270 0 0 0 94% 0.95 2 0.38 16404 6674 9,730 0 0 0 96% 0.95 3 0.55 24125 5322 16670 1,125 0 1,008 93% 0.92 4 0.82 35744 29464 0 0 0 6,280 74% 0.82 5 0.24 10355 4097 6258 0 0 0 96% 0.95 6 0.41 17828 0 640 0 0 17,188 4% 0.23 7 0.26 11,275 0 493 0 0 10,782 4% 0.23 Total to pond 2.97 129,516 59,347 44,568 1,125 0 24,476 76% 0.81 Total 3.23 140,791 59,347 45,061 1,125 0 35,258 71% 0.76 Historic 124 0.40 17,410 0 1,540 665 3,780 11,425 21% 0.36 Historic 624 2.83 123,381 0 0 0 36,112 87,269 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 At = total area over which C is applicable; the sum of all Ai's Flow.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: 3/27/2017 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 0.58 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 0.38 0.95 25 2.0 1.1 388 1.0 0.016 2.0 3.30 4.4 413 12.3 5.0 3 3 0.55 0.92 25 2.0 1.3 328 1.0 0.016 2.0 2.79 4.1 353 12.0 5.0 4 4 0.82 0.82 125 1.0 5.7 327 0.5 0.030 0.8 7.19 12.9 452 12.5 12.5 5 5 0.24 0.95 15 2.5 0.8 168 1.0 0.016 2.0 1.39 2.2 183 11.0 5.0 6 6 0.41 0.23 16 20.0 2.3 105 0.5 0.016 1.4 1.23 3.5 121 10.7 5.0 7 7 0.26 0.23 25 2.0 6.2 53 6.5 0.016 5.1 0.17 6.4 78 10.4 6.4 All to Pond 2.97 0.81 Total 3.23 0.76 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.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: 3/27/2017 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 0.58 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 0.38 0.95 1.00 25 2.0 0.7 388 1.0 0.016 2.0 3.30 4.0 413 12.3 5.0 3 3 0.55 0.92 1.00 25 2.0 0.7 328 1.0 0.016 2.0 2.79 3.5 353 12.0 5.0 4 4 0.82 0.82 1.00 125 1.0 2.0 327 0.5 0.030 0.8 7.19 9.2 452 12.5 9.2 5 5 0.24 0.95 1.00 15 2.5 0.5 168 1.0 0.016 2.0 1.39 1.9 183 11.0 5.0 6 6 0.41 0.23 0.28 16 20.0 2.2 105 0.5 0.016 1.4 1.23 3.4 121 10.7 5.0 7 7 0.26 0.23 0.29 25 2.0 5.8 53 6.5 0.016 5.1 0.17 6.0 78 10.4 6.0 All to Pond 2.97 0.81 1.00 Total 3.23 0.76 0.95 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.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: 3/27/2017 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 0.58 0.95 5.0 2.85 1.6 1.6 To area inlet 1 2 2 0.38 0.95 5.0 2.85 1.0 1.0 To Rain Garden 1 3 3 0.55 0.92 5.0 2.85 1.5 1.5 To Rain Garden 1 4 4 0.82 0.82 12.5 2.02 1.4 1.4 To Rain Garden 3 5 5 0.24 0.95 5.0 2.85 0.6 0.6 To Rain Garden 2 6 6 0.41 0.23 5.0 2.85 0.3 0.3 Det Pond 7 7 0.26 0.23 6.4 2.61 0.2 0.2 To Street All to Pond 2.97 0.81 Total 3.23 0.76 Historic 124 0.40 0.36 6.2 2.64 0.4 0.4 To Existing Pond Historic 624 2.83 0.29 12.1 2.05 1.7 1.7 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.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: 3/27/2017 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 0.58 1.00 5.0 9.95 5.7 5.7 To area inlet 1 2 2 0.38 1.00 5.0 9.95 3.7 3.7 To Rain Garden 1 3 3 0.55 1.00 5.0 9.95 5.5 5.5 To Rain Garden 1 4 4 0.82 1.00 9.2 7.97 6.5 6.5 To Rain Garden 3 5 5 0.24 1.00 5.0 9.95 2.4 2.4 To Rain Garden 2 6 6 0.41 0.28 5.0 9.95 1.2 1.2 Det Pond 7 7 0.26 0.29 6.0 9.31 0.7 0.7 To Street All to Pond 2.97 1.00 5.0 9.95 29.6 29.6 Total 3.23 0.95 5.0 9.95 30.6 30.6 0 Historic 124 0.40 0.45 5.5 9.63 1.73 1.7 To Existing Pond 0 Historic 624 2.83 0.36 12.1 7.14 7.3 7.3 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.xls Q100 C APPENDIX C HYDRAULIC & BMP SIZING CALCULATIONS Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia = 95.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.950 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.36 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 41,609 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 1,241 cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 0.0 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum) DWQCV = 12 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin = 791 sq ft D) Actual Flat Surface Area AActual = 799 sq ft E) Area at Design Depth (Top Surface Area) ATop = 1833 sq ft F) Rain Garden Total Volume VT= 1,316 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided? B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y = ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft iii) Orifice Diameter, 3/8" Minimum DO = N/A in Design Procedure Form: Rain Garden (RG) PPK North Star Design, Inc. March 27, 2017 Affordable Storage Rain Garden #1 (Basin 2 and 3) UD-BMP (Version 3.06, November 2016) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO UD-BMP_Basin 2 and 3.xlsm, RG 3/27/2017, 12:19 PM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW THE LINER IF THE SUBGRADE IS ANGULAR 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) PPK North Star Design, Inc. March 27, 2017 Affordable Storage Rain Garden #1 (Basin 2 and 3) Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO UD-BMP_Basin 2 and 3.xlsm, RG 3/27/2017, 12:19 PM Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia = 96.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.960 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.37 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 10,355 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 316 cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 0.0 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum) DWQCV = 12 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin = 199 sq ft D) Actual Flat Surface Area AActual = 230 sq ft E) Area at Design Depth (Top Surface Area) ATop = 542 sq ft F) Rain Garden Total Volume VT= 386 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided? B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y = ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft iii) Orifice Diameter, 3/8" Minimum DO = N/A in Design Procedure Form: Rain Garden (RG) PPK North Star Design, Inc. March 27, 2017 Affordable Storage Rain Garden #2 (Basin 5) UD-BMP (Version 3.06, November 2016) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO UD-BMP_Basin 5.xlsm, RG 3/27/2017, 12:20 PM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW THE LINER IF THE SUBGRADE IS ANGULAR 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) PPK North Star Design, Inc. March 27, 2017 Affordable Storage Rain Garden #2 (Basin 5) Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO UD-BMP_Basin 5.xlsm, RG 3/27/2017, 12:20 PM Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia = 74.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.740 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.24 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 35,744 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 701 cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 0.0 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum) DWQCV = 8in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin = 529 sq ft D) Actual Flat Surface Area AActual = 707 sq ft E) Area at Design Depth (Top Surface Area) ATop = 1732 sq ft F) Rain Garden Total Volume VT= 762 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided? B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y = ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft iii) Orifice Diameter, 3/8" Minimum DO = N/A in Design Procedure Form: Rain Garden (RG) PPK North Star Design, Inc. March 27, 2017 Affordable Storage Rain Garden #3 (Basin 4) UD-BMP (Version 3.06, November 2016) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO UD-BMP_Basin 4.xlsm, RG 3/27/2017, 12:18 PM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) PPK North Star Design, Inc. March 27, 2017 Affordable Storage Rain Garden #3 (Basin 4) Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO UD-BMP_Basin 4.xlsm, RG 3/27/2017, 12:18 PM Project = Inlet ID = Design Information (Input) MINOR MAJOR Type of Inlet Inlet Type = Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 0.50 0.50 inches Number of Unit Inlets (Grate or Curb Opening) No = 2 2 Water Depth at Flowline (outside of local depression) Ponding Depth = 5.0 7.5 inches Grate Information MINOR MAJOR Length of a Unit Grate Lo (G) = 3.00 3.00 feet Width of a Unit Grate Wo = 2.00 2.00 feet Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = 0.70 0.70 Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = 0.50 0.50 Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = 2.41 2.41 Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = 0.67 0.67 Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening Lo (C) = N/A N/A feet Height of Vertical Curb Opening in Inches Hvert = N/A N/A inches Height of Curb Orifice Throat in Inches Hthroat = N/A N/A inches Angle of Throat (see USDCM Figure ST-5) Theta = N/A N/A degrees Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = N/A N/A feet Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = N/A N/A Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = N/A N/A Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = N/A N/A MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition) Qa = 2.1 5.7 cfs WARNING: Inlet Capacity less than Q Peak for MAJOR Storm Q PEAK REQUIRED = 1.6 5.7 cfs INLET IN A SUMP OR SAG LOCATION Affordable Storage Inlet 1-1 CDOT Type C Grate H-Vert H-Curb W Lo (C) Lo (G) Wo WP Override Depths Inlet No.1.xlsm, Inlet In Sump 3/27/2017, 10:34 AM 3/27/2017 UDSEWER Math Model Interface Results: Storm 2 03/27/2017 14:26 file:///C:/Users/Patricia/Documents/report0.html 1/2 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 0.00 0.00 0.00 0.00 Storm Manhole 0.00 0.00 0.00 0.00 5.70 0.00 0.00 0.00 5.70 Inlet 1­1 0.00 0.00 0.00 0.00 5.70 0.00 0.00 0.00 5.70 Surface Water Present (Upstream) 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 3/27/2017 UDSEWER Math Model Interface Results: Storm 2 03/27/2017 14:26 file:///C:/Users/Patricia/Documents/report0.html 2/2 Sewer Sizing Summary: Existing Calculated Used Element Name Peak Flow (cfs) Cross Section Rise Span Rise Span Rise Span Area (ft^2) Comment Storm Manhole 5.70 CIRCULAR 18.00 in 18.00 in 18.00 in 18.00 in 18.00 in 18.00 in 1.77 Inlet 1­1 5.70 CIRCULAR 15.00 in 15.00 in 15.00 in 15.00 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): 70.72 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 Manhole 67.00 67.67 0.00 0.00 70.72 70.98 70.88 0.26 71.14 Inlet 1­1 67.67 69.54 0.02 0.00 71.00 72.60 71.33 1.61 72.94 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 22.30 44.60 66.90 89.20 111.50 133.80 156.10 178.40 200.70 66.49 67.09 67.69 68.29 68.89 69.49 70.09 70.69 71.29 71.89 HGL EGL Project = Inlet ID = Design Information (Input) MINOR MAJOR Type of Inlet Inlet Type = Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 1.00 1.00 inches Number of Unit Inlets (Grate or Curb Opening) No = 1 1 Water Depth at Flowline (outside of local depression) Ponding Depth = 5.0 12.0 inches Grate Information MINOR MAJOR Length of a Unit Grate Lo (G) = 3.00 3.00 feet Width of a Unit Grate Wo = 2.00 2.00 feet Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = 0.70 0.70 Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = 0.50 0.50 Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = 2.50 2.50 Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = 0.60 0.60 Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening Lo (C) = N/A N/A feet Height of Vertical Curb Opening in Inches Hvert = N/A N/A inches Height of Curb Orifice Throat in Inches Hthroat = N/A N/A inches Angle of Throat (see USDCM Figure ST-5) Theta = N/A N/A degrees Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = N/A N/A feet Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = N/A N/A Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = N/A N/A Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = N/A N/A MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition) Qa = 1.7 7.6 cfs Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED = 1.4 6.5 cfs INLET IN A SUMP OR SAG LOCATION Affordable Storage Inlet 2-1 CDOT Type C Grate H-Vert H-Curb W Lo (C) Lo (G) Wo WP Override Depths Inlet No.1.xlsm, Inlet In Sump 3/27/2017, 10:24 AM Project: Inlet ID: Design Information (Input) MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') aLOCAL = 0.0 0.0 inches Total Number of Units in the Inlet (Grate or Curb Opening) No = 1 1 Length of a Single Unit Inlet (Grate or Curb Opening) Lo = 3.00 3.00 ft Width of a Unit Grate (cannot be greater than W from Q-Allow) Wo = 2.00 2.00 ft Clogging Factor for a Single Unit Grate (typical min. value = 0.5) Cf-G = 0.50 0.50 Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1) Cf-C = N/A N/A Street Hydraulics: WARNING: Q > ALLOWABLE Q FOR MAJOR STORM MINOR MAJOR Total Inlet Interception Capacity Q = 0.15 0.37 cfs Total Inlet Carry-Over Flow (flow bypassing inlet) Qb = 0.0 0.3 cfs Capture Percentage = Qa/Q o = C% = 76 53 % INLET ON A CONTINUOUS GRADE Affordable Storage Inlet 2-2 (Vaned Grate inlet) Directional 45-Degree Bar Grate Inlet No.1.xlsm, Inlet On Grade 3/27/2017, 10:27 AM 3/27/2017 UDSEWER Math Model Interface Results: Storm 2 03/27/2017 12:42 file:///C:/Users/Patricia/Documents/report0.html 1/2 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 0.00 0.00 0.00 0.00 Inlet 2­2 0.00 0.00 0.00 0.00 0.35 0.00 0.00 0.00 6.85 Surface Water Present (Upstream) Inlet 2­1 0.00 0.00 0.00 0.00 6.50 0.00 0.00 0.00 6.50 Surface Water Present (Downstream) Sewer Input Summary: Elevation Loss Coefficients Given Dimensions Element Name Sewer Length (ft) Downstream Invert (ft) Slope (%) Upstream Invert (ft) Mannings n Bend Loss 3/27/2017 UDSEWER Math Model Interface Results: Storm 2 03/27/2017 12:42 file:///C:/Users/Patricia/Documents/report0.html 2/2 Sewer Sizing Summary: Existing Calculated Used Element Name Peak Flow (cfs) Cross Section Rise Span Rise Span Rise Span Area (ft^2) Comment Inlet 2­2 6.85 CIRCULAR 18.00 in 18.00 in 18.00 in 18.00 in 18.00 in 18.00 in 1.77 Inlet 2­1 6.50 CIRCULAR 18.00 in 18.00 in 18.00 in 18.00 in 18.00 in 18.00 in 1.77 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): 70.72 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 2­2 67.00 67.38 0.00 0.00 70.72 70.93 70.95 0.21 71.17 Inlet 2­1 67.38 67.65 0.01 0.00 70.97 71.10 71.18 0.14 71.31 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 6.50 13.00 19.50 26.00 32.50 39.00 45.50 52.00 58.50 66.48 67.08 67.68 68.28 68.88 69.48 70.08 70.68 71.28 71.88 HGL EGL D APPENDIX D DETENTION POND 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: 3/27/2017 Equations: A trib. To pond = 2.97 acre QD = CiA C100 = 1.00 Vi = T*CiA = T*QD Developed C*A = 3.0 acre Vo =K*QPO*T QPO = 1.57 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 29.6 8865 471 8394 0.193 10 7.72 22.9 13757 942 12815 0.294 20 5.60 16.6 19958 1884 18074 0.415 30 4.52 13.4 24164 2826 21338 0.490 40 3.74 11.1 26659 3768 22891 0.525 50 3.23 9.6 28779 4710 24069 0.553 60 2.86 8.5 30579 5652 24927 0.572 70 2.62 7.8 32682 6594 26088 0.599 80 2.38 7.1 33929 7536 26393 0.606 90 2.22 6.6 35604 8478 27126 0.623 100 2.05 6.1 36531 9420 27111 0.622 110 1.93 5.7 37832 10362 27470 0.631 120 1.80 5.3 38491 11304 27187 0.624 130 1.60 4.8 37066 12246 24820 0.570 140 1.40 4.2 34927 13188 21739 0.499 150 1.20 3.6 32076 14130 17946 0.412 160 1.15 3.4 32789 15072 17717 0.407 170 1.10 3.3 33323 16014 17309 0.397 180 1.05 3.1 33680 16956 16724 0.384 Required Storage Volume: 27470 ft3 0.631 acre-ft STAGE - STORAGE TABLE (100-YEAR) LOCATION: Affordable storage PROJECT NO: 177-10 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 8/1/2008 100 yr Detention Volume Required = 0.631 Water Quality Volume Required = 0.000 Total Volume Required= 0.631 Surface Incremental Total Stage Area Storage Storage (ft) (ft2) (ac-ft) (ac-ft) 4766.00 0 4767.00 4,035 0.031 0.03 4768.0 5,650 0.086 0.09 4769.0 7,227 0.255 0.29 4770.0 8,945 0.185 0.47 100 yr WSEL 4770.72 10,306 0.160 0.631 4771.0 10,825 0.227 0.70 <==SPILLWAY ELEV 4772.0 18,345 0.331 1.03 Detention Pond Outlet Sizing (100 yr event) LOCATION: Affordable Storage PROJECT NO: 177-10 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 3/27/2017 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 = 1.57 cfs outlet pipe dia = D = 15.0 in Invert elev. = 4766.00 ft Eo = 4766.22 ft h = 4770.7 ft - 100 yr WSEL Co = 0.62 solve for effective area of orifice using the orifice equation Ao = 0.149 ft2 = 21.4 in2 orifice dia. = d = 5.22 in Check orifice discharge coefficient using Figure 5-21 (Hydraulic Engineering ) d / D = 0.35 kinematic viscosity, u = 1.22E-05 ft2/s Reynolds no. = Red = 4Q/(pdu) = 3.77E+05 Co = (K in figure) = 0.62 check Use d = 5.25 in A o = 0.150 ft 2 = 21.65 in 2 Q max = 1.59 cfs Emergency Overflow Spillway Sizing LOCATION: Affordable Storage PROJECT NO: 177-10 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 5/24/2005 Equation for flow over a broad crested weir Q = CLH3/2 where C = weir coefficient = 2.8 H = overflow height L = length of the weir The pond has a spill elevation 0 ft above the maximum water surface elevation in the pond Spillway will be designed with 0725 ft flow depth, thus H = 1 ft Size the spillway assuming that the pond outlet is completely clogged. Q (100) = 29.6 cfs Spill elev = 4971.00 ft 100 yr WSEL = 4970.2 ft Top of berm elev.= 4972.00 Weir length required: L = 11 ft Use L = 20 ft v = 1.35 ft/s 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 1.00 922 1.00 0.27 Watershed Imperviousness = 76.0% percent 2.00 4,107 2.00 0.40 Percentage Hydrologic Soil Group A =0.0%percent 3.00 10,813 3.00 0.50 Percentage Hydrologic Soil Group B = 0.0% percent 4.00 19,049 4.00 0.58 Percentage Hydrologic Soil Groups C/D = 100.0% percent 4.90 27,776 4.90 0.64 5.00 28,823 5.00 0.65 User Input 17 5.50 35,968 5.50 11.15 6.00 43,112 6.00 31.10 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 = 0.060 0.181 0.271 0.357 0.511 0.661 0.860 acre‐ft OPTIONAL Override Runoff Volume = acre‐ft Inflow Hydrograph Volume = 0.059 0.181 0.271 0.357 0.510 0.661 0.859 acre‐ft Time to Drain 97% of Inflow Volume = 368 10 13 16 20 hours Time to Drain 99% of Inflow Volume = 36810131620 hours Maximum Ponding Depth = 1.56 2.51 2.91 3.21 3.64 4.00 4.40 ft Maximum Ponded Area = 0.062 0.172 0.233 0.288 0.369 0.436 0.526 acres Maximum Volume Stored = 0.034 0.136 0.216 0.295 0.437 0.581 0.776 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 3/27/2017, 12:29 PM 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 3.5 4 4.5 5 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 3/27/2017, 12:29 PM E APPENDIX E BMP SCHEDULE & COST ESTIMATE Project: Disturbed Acres: 3.23 EROSION CONTROL BMPs Units Estimated Quantity Unit Price Total Price L.F. 1295 $3.00 $3,885.00 each 12 $85.00 $1,020.00 each 1 $180.00 $180.00 each 4 $255.00 $1,020.00 each 2 $1,500.00 $3,000.00 each 1 $1,200.00 $1,200.00 Sub-Total: $10,305.00 1.5 x Sub-Total: $15,457.50 Amount of security: $15,457.50 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: $15,457.50 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 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 3/27/2017 10:13 AM N:\177-10 Affordable Storage\drainage\FC Escrow.xls 2/28/2017 Calculation for Required LID Treatment New Impervious Area 106730 sq. ft. Required Minimum Impervious Area to be Treated (75%) 80048 sq. ft. Impervious Area Treated by LID Treatment Method #1 (Rain garden #1) 40601 sq. ft. Impervious Area Treated by LID Treatment Method #2 (Rain garden #2) 10355 sq. ft. Impervious Area Treated by LID Treatment Method #3 (Rain Garden #3) 29464 sq. ft. Total Impervious Area Treated 80420 sq. ft. AFFORDABLE STORAGE LID Summary Table 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. Lateral Loss Cross Section Rise (ft or in) Span (ft or in) Inlet 2­2 37.70 67.00 1.0 67.38 0.015 0.03 0.00 CIRCULAR 18.00 in 18.00 in Inlet 2­1 27.00 67.38 1.0 67.65 0.015 0.05 0.00 CIRCULAR 18.00 in 18.00 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 2­2 9.13 5.17 12.16 5.39 11.64 5.67 1.09 Pressurized 6.85 37.70 Inlet 2­1 9.13 5.17 11.83 5.28 11.22 5.61 1.11 Pressurized 6.50 27.00 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. Cross Section Rise (ft or in) Span (ft or in) Storm Manhole 66.60 67.00 1.0 67.67 0.015 0.03 0.00 CIRCULAR 18.00 in 18.00 in Inlet 1­1 156.00 67.67 1.2 69.54 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 Storm Manhole 9.13 5.17 11.05 5.01 10.30 5.45 1.14 Pressurized 5.70 66.60 Inlet 1­1 6.15 5.01 11.60 5.60 11.41 5.69 1.03 Pressurized 5.70 156.00 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.