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Home My WebLink AboutFEEDER SUPPLY - PDP - PDP130012 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTPRELIMINARY DRAINAGE AND EROSION CONTROL REPORT FEEDER SUPPLY PROJECT PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT FEEDER SUPPLY PROJECT Prepared for: Jon Prouty Lagunitas Fort Collins, CO 80216 Prepared by: North Star Design 700 Automation Drive, Unit I Windsor, Colorado 80550 (970) 686-6939 July 3, 2013 Job Number 173-10 July 3, 2013 Glen Schlueter City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522 RE: Preliminary Drainage and Erosion Control Report for Feeder Supply Project Dear Glen, I am pleased to submit for your review and approval, this Preliminary Drainage & Erosion Control Report for the Feeder Supply project. I certify that this report for the drainage design of the Feeder supply 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. Prepared by: Patricia Kroetch P.E. Project Manager 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 1.3 Major Basin Description ..........................................................................................2 1.4 Sub Basin Description .............................................................................................2 2. DRAINAGE DESIGN CRITERIA 2.1 Regulations ..............................................................................................................2 2.2 Development Criteria Reference and Constraints ...................................................2 2.3 Hydrologic Criteria ..................................................................................................3 2.4 Hydraulic Criteria ....................................................................................................3 3. DRAINAGE FACILITY DESIGN 3.1 General Concept ......................................................................................................3 3.2 Specific Flow Routing .............................................................................................3 3.3 Drainage Summary ..................................................................................................4 4. STORM WATER MANAGEMENT CONTROLS 4.1 SWMP contact information ....................................................................................3 4.2 Identification and location of all potential pollution sources ..................................4 4.3 Best Management Practices (BMP’s) for Stormwater Pollution Prevention ...........5 4.4 BMP Implementation ...............................................................................................8 5. CONCLUSIONS 6.1 Compliance with Standards ..................................................................................11 6.2 Drainage Concept ..................................................................................................11 6. REFERENCES ..................................................................................................................12 APPENDICES A Vicinity Map B Hydrologic Computations 1 1. GENERAL LOCATION AND DESCRIPTION 1.1. Location The Feeder Supply redevelopment project, hereafter referred to as the Feeder Supply, is located at 359 Linden. The proposed project is located on a portion of Blocks 6 & 7, City of Fort Collins Old Town in the Northeast Quarter of Section 12, Township 7 North, Range 69 West of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. See the location map in Appendix A. This project is bounded on the northeast by Willow Street, on the southeast by Linden Street, on the northwest by Schrader Oil Company, and on the southwest by existing office and commercial development. 1.2. Description of Property The project consists of approximately 1.4 acres of land. There is currently one original historic building on site that has several additions which were added after the original building and gravel drives and parking. There is no existing vegetation on site. The original historic building will be preserved and the additions will be removed with this project. The original building will be expanded and an additional residential and retail building with parking on the main floor will be located northwest of the existing structure that will remain. Willow Street will be widened with this project and internal drives and parking will be paved with asphalt. All elevations given in this report and in the construction plans are based on the 1929 NGVD unadjusted datum. See the grading sheet for specific elevations on the site and elevation of the building at each entry point. Stormwater from the Cache La Poudre Drainage Basin is ultimately routed to the Poudre River in the existing streets and existing storm pipes in historic flow routes. Runoff from this site will flow to a storm pipe that will be relocated with this project. This storm system will convey the runoff to an existing inlet at the intersection of Willow and Linden. From this point the runoff will be routed through a Baysaver water quality structure and into a regional detention facility. Because of this, no on site detention is being provided. 2 Currently water quality and detention measures have not been provided for the existing development. With this project, it is proposed to construct approximately 22,000 sq.ft of additional roof area, 16,600 sq. ft. of additional asphalt pavement area and no additional concrete area. The original development (historic condition) had approximately 5230 square feet of roof area, 1760 square feet of concrete and no asphalt. The entire site (except for the building area that will remain) is expected to undergo clearing, excavating and grading. Since there additional impervious area being constructed, water quality and detention would normally be required for the new impervious area. With this project the City will allow the runoff from the site to enter the existing storm system without detention because detention for this area is provided in a regional facility downstream. Even though the runoff from the site is directed through a Bay saver water quality structure, additional water quality enhancement is proposed for site in the form of water quality enhancement (L.I.D.) swales and approximately 3500 square feet of porous concrete. 1.3. Major Basin Description This site is located in the Cache La Poudre Drainage Basin and all runoff from the site will reach the Poudre River. The site is not located within the FEMA designated 100 year floodplain or the City designated flood plain. 1.4. Sub-basin Description The majority of the site will be collected in an onsite L.I.D. and storm system and conveyed to the existing inlet located at the intersection of Willow and Linden. A small portion of the entry drives will directly enter the adjacent streets and flow in the streets to the same storm system. See Section 3 of this report for specific details. 2. DRAINAGE DESIGN CRITERIA 2.1. Regulations Drainage for this site has been designed to meet or exceed the “City of Fort Collins Stormwater Criteria Manual” specifications, the City of Fort Collins Cache la Poudre Basin Master Plan and the update to Chapter 26 of the City Code. Where applicable, the criteria established in the “Urban Storm Drainage Criteria Manual” (UDFCD), 2001 has 3 been used. 2.2. Development Criteria Reference and Constraints Stormwater runoff from this site has been routed to conform to the requirements of the City Stormwater Department. Detention would normally be required for this site but because the runoff will enter the storm system and be conveyed to a regional facility, detention will not be provided. Water quality facilities are required for the improvements and are being provided by an existing off site Bay Saver water quality structure, 3500 square feet of porous concrete and proposed water quality swales (LID) on the site. These water quality enhancement measures serve to meet the City criteria for new developed runoff. 2.3. Hydrologic Criteria Runoff computations were prepared for the 2 year and 10 year minor and 100 year major storm frequency utilizing the Rational Method. All hydrologic calculations associated with the basins are included in Appendix B of this report. 2.4. Hydraulic Criteria Necessary hydraulic calculations will be provided with the final drainage report for this site and will be prepared in accordance with the City of Fort Collins Drainage Criteria and the Urban Area Drainage Criteria Manual. 3. DRAINAGE FACILITY DESIGN 3.1. General Concept All of the runoff from this site historically sheet flows to the adjacent streets and is intercepted by the existing inlets located in Willow and Linden Streets. With the construction of these proposed improvements, onsite stormwater will be collected in an onsite storm and LID system and conveyed to the existing storm system in Willow Street. 3.2. Specific Flow Routing A summary of the drainage patterns within each basin is provided in the following paragraphs. 4 Basin 1 encompasses the entire site. This basin includes a majority of the asphalt drives on site and all of the buildings (existing and proposed) on site. Improvements proposed in the right of way for Willow or existing improvements along Linden are not included in this basin. Runoff from this basin will sheet flow to proposed 4’ concrete pans on site and into two proposed L.I.D. swales. Roof runoff will be collected in an onsite storm system and piped to the relocated storm system in Willow. Water quality is provided for this basin by the L.I.D. swales, porous concrete and a downstream Bay Saver structure. 3.3. Drainage Summary Drainage for this site was designed to conform to the City of Fort Collins stormwater and water quality requirements. Water quality is provided for a majority of the site utilizing water quality swales and porous concrete. Water quality for the site is also provided by routing runoff through a Bay Saver sediment trap downstream. 4. STORMWATER MANAGEMENT CONTROLS 4.1 SWMP contact information Permit holder: Name: Address: Phone Number: Email Address: Appointed agent: Name: Address: Phone Number: Email Address: 5 4.2 Identification and location of all potential pollution sources Potential Pollutant Source Activity Potential Pollutant Generated Applicable to this project Disturbed Areas Sediment X Soil stockpiles Sediment X Travel to adjacent public streets Tracked sediment X Contaminated soils Sediment, chemicals Loading and unloading chemicals Chemicals Outdoor storage of chemicals Chemicals On site equipment maintenance Oil, grease On site equipment fueling Diesel, gasoline X Dust generating activities Particulates, sediment X Use of fertilizer, pesticides, herbicides Fertilizer, pesticides Use of detergents, solvents, oils Detergents, solvents, oil X Waste dumpsters, waste piles Chemicals X Concrete washout Concrete, sediment X 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 4.3 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. Silt fence and rock sock filters shall be in place prior to commencement of construction activities. During demolition, 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 6 implemented in the existing curb line of Linden Street as shown on the Drainage & Erosion Control Plan. Inlet Protection shall be located around the existing curb inlet in Linden. Once construction of Willow is complete, rock socks will be placed in the curb line and inlet protection will be placed around the existing inlet. All BMP's shall be installed per the details shown on the construction plan set. Temporary & Permanent Structural BMP’s: Structural BMP Approximate location on site Applicable to this Project Silt Fence Site perimeter, refer to site map X Straw bale dams Rock Socks At existing curb, refer to site map X Earthen diversion dams Vegetated swales Sediment trap/pond Pipe slope drains Geogrid Inlet/outlet protection Existing inlet, refer to site map X Culverts Riprap Erosion control mats Inlet protection At inlets, refer to site map 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 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. 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. 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 7 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: 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 Minimization of site disturbance Mulch Seed & mulch stockpiles after 30 days Stockpile toe protection (silt fence, wattles or ditch) Preservation & protection of existing vegetation & trees Good site housekeeping (routine cleanup of trash & constr debris) Entire Site X Heavy equip staged on site, properly maintained & inspected daily (no onsite maintenance) Staging area X 4.4 BMP Implementation 1) 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. 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. Because this is an Infill and redevelopment site, natural BMP’s will be difficult to implement. 8 The following phase depictions and erosion controls are suggestions to the contractor only and are in no way intended to dictate construction phasing or control of the work on site. The contractor shall be responsible to control construction phasing and provide adequate erosion control associated with each phase in order to comply with the SWM Plan and Permit that is obtained by the contractor (or owner) for the site. Phase 1 – Mobilization Install silt fence, Install storm drain inlet protection at existing inlets, install rock socks in existing curb flowline, set dumpster. Phase 2 – Demolition Demo existing building section slated for demolition, remove debris from site. Demo existing pavements and remove debris from site. Phase 3 - Overlot Grading Cut and fill on site to achieve subgrade elevations Phase 4 - Utilities Excavate and install for water and sewer, excavate and install dry utilities, install storm and pipe for LID swales. Phase 5 – Exterior concrete Establish temporary concrete washout area, cut for curb and gutter and walks, place concrete curbs and walks. Phase 6 – Site Paving Install sub base, install Asphalt pavement, install additional rock socks in new curb. Phase 7 – Building construction Install concrete foundation, remove concrete washout. Complete building construction Phase 8 – Landscape installation Backfill curbs and final shape planting areas, complete LID swale construction, Install irrigation system, Landscape plant installation, Install mulch ground cover, remove silt fence. Phase 9 – Final Stabilization Final stabilization is complete when constructed improvements are in place, Inspect completed construction for possible sources of erosion and amend the plan as required to trap sediments. Remove rock socks and inlet protection 2) Materials Handling and Spill Prevention: Materials Handling & Spill Prevention BMP Approximate location on site Applicable to this Project Portable toilets, anchored & located away from drainages Refer to site map X Fuel storage located in bulk tanks with secondary containment & spill kit Mobile fueling performed at least 200 feet away from drainages & fully attended Refer to site map X 9 Fertilizers, form oil, solvents, cleaners, detergent stored in 55 gal or smaller containers, kept in storage units Refer to site map X Dumpsters containing used chemicals containers & liquid wastes kept covered Refer to site map 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 Construction Trailer X 3) Dedicated Asphalt or Concrete Batch Plant: Not proposed with this development. 4) 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 or by the State of Colorado. 10 5) 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 management company. Concrete waste will be allowed to harden and then will be removed from site. No 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. 6) Groundwater and Stormwater Dewatering: No groundwater encountered during soils exploration therefore 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. 7) 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 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. 11 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. CONCLUSIONS 5.1. Compliance with Standards All computations that have been completed within this report will be in compliance with the City of Fort Collins Erosion Control Reference Manual for Construction Sites and the City of Fort Collins Stormwater Criteria Manual. 5.2. Drainage Concept The proposed drainage concepts presented in this report, in the final drainage report and on the construction plans, will adequately provide for stormwater quality treatment for the proposed improvements. Conveyance elements have been designed to convey required flows to the proposed water quality swales and the existing regional detention facility and ultimately to the Cache la Poudre River. If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit will be required. 12 6. REFERENCES 1. City of Fort Collins, “Storm Drainage Criteria Manual”, (SDCM), dated March 1999. 2. Urban Drainage and Flood Control District, “Urban Storm Drainage Criteria Manual”, Volumes 1 and 2, dated June 2001, and Volume 3 dated September 2001. A APPENDIX A VICINITY MAP B APPENDIX B HYDROLOGIC COMPUTATIONS North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: Feeder Supply PROJECT NO: 173-09 COMPUTATIONS BY: PPK DATE: 4/9/2013 Recommended % Impervious from Urban Storm Drainage Criteria Manual % Impervious Roofs: 90% Streets and Parking (Asphalt) 100% Concrete Drives and Walks 90% Packed Gravel: 40% Landscaped Areas (Clayey soil, 0-1% slopes): 0% SUBBASIN TOTAL TOTAL ROOF ASPHALT CONCRETE GRAVEL LANDSCAPE % RUNOFF RUNOFF RUNOFF RUNOFF ID AREA AREA AREA AREA AREA AREA AREA Impervious COEFF. COEFF. COEFF. COEFF. (ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) C2 C5 C10 C100 historic basin 1.14 49,853 5,233 0 1,760 18673 24,187 28% 0.21 0.29 0.37 0.56 Basin 1 1.14 49,853 27,575 16,626 1,536 0 4,116 86% 0.67 0.69 0.72 0.79 RUNOFF COEFFICIENTS & % IMPERVIOUS Flow.xls Cval North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: Feeder Supply PROJECT NO: 173-09 COMPUTATIONS BY: PPK DATE: 4/9/2013 SUB-BASIN DATA INITIAL / OVERLAND TIME TRAVEL TIME / GUTTER OR CHANNEL FLOW tc CHECK FINAL REMARKS (ti)(tt) (URBANIZED BASIN) tc DESIGN SUBBASIN Area C5 Length Slope ti Length Slope Chan. Cv Vel. tt tc = Total L tc=(l/180)+10 POINT ID (ac) (ft) (ft/ft) (min) (ft) (ft/ft) Type (ft/s) (min) ti + tt (ft) (min) (min) (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) historic basin historic basin 1.14 0.29 35 0.010 8.7 305 0.005 D 10 0.7 7.2 15.9 340 11.9 11.9 Basin 1 Basin 1 1.14 0.69 26 0.030 2.6 205 0.005 F 20 1.4 2.4 5.1 231 11.3 5.1 EQUATIONS: Channel Type Cv tc = t i + tt A 2.5 B 5.0 ti = [0.395 (1.1 - C 5 ) L 0.5 ] / S 1/3 C 7.0 D 10.0 tt = L/V V = C v*S 0.5 E 15.0 F 20.0 final tc = minimum of t i + tt and urbanized basin check minimum tc = 5 minutes TIME OF CONCENTRATION Paved Grassed Waterway Bare Ground Short Pasture/ Lawn Tillage / Field Heavy Meadow Flow.xls TOC5 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: Feeder Supply PROJECT NO: 173-09 COMPUTATIONS BY: PPK DATE: 4/9/2013 DIRECT RUNOFF TOTAL Inlet Capacity REMARKS DESIGN SUBBASIN A C2 tc iQ2 Q2 Total POINT ID (ac) (min) (in/hr) (cfs) (cfs) (cfs) historic basin historic basin 1.14 0.21 11.9 2.08 0.5 0.5 Basin 1 Basin 1 1.14 0.67 5.1 2.84 2.2 2.2 Q = C i A Q = peak discharge (cfs) C = runoff coefficient i = rainfall intensity (in/hr) from IDF curve A = drainage area (acres) RATIONAL METHOD PEAK RUNOFF (2-YEAR) Flow.xls Q2 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: Feeder Supply PROJECT NO: 173-09 COMPUTATIONS BY: PPK DATE: 4/9/2013 DIRECT RUNOFF TOTAL Inlet Capacity REMARKS DESIGN SUBBASIN A C10 tc iQ10 Q10 Total POINT ID (ac) (min) (in/hr) (cfs) (cfs) (cfs) historic basin historic basin 1.14 0.37 11.9 3.56 1.5 1.5 Basin 1 Basin 1 1.14 0.72 5.1 4.85 4.0 4.0 Q = C i A Q = peak discharge (cfs) C = runoff coefficient i = rainfall intensity (in/hr) from IDF curve A = drainage area (acres) RATIONAL METHOD PEAK RUNOFF (10-YEAR) Flow.xls Q10 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: Feeder Supply PROJECT NO: 173-09 COMPUTATIONS BY: PPK DATE: 4/9/2013 DIRECT RUNOFF TOTAL Inlet Capacity REMARKS DESIGN SUBBASIN A C100 t c iQ100 Q100 Total POINT ID (ac) (min) (in/hr) (cfs) (cfs) (cfs) historic basin historic basin 1.14 0.56 11.9 7.26 4.7 4.7 Basin 1 Basin 1 1.14 0.79 5.1 9.91 9.0 9.0 to LID swales Q = C i A Q = peak discharge (cfs) C = runoff coefficient i = rainfall intensity (in/hr) from IDF curve A = drainage area (acres) RATIONAL METHOD PEAK RUNOFF (100-YEAR) Flow.xls Q100