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Home My WebLink AboutFEEDER SUPPLY - PDP - PDP130012 - SUBMITTAL DOCUMENTS - ROUND 1 - 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 April 9, 2013 Job Number 173-10 April 9, 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. EROSION CONTROL 4.1 General Concept .....................................................................................................4 4.2 Specific Details ........................................................................................................4 5. CONCLUSIONS 6.1 Compliance with Standards ....................................................................................4 6.2 Drainage Concept ....................................................................................................4 6. REFERENCES ....................................................................................................................5 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 and no additional concrete walk. 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 down stream. 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. 1.3. Major Basin Description This site is located in the Cache La Poudre Drainage Basin. 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 4 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 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, 3 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 and proposed water quality swales on the site. 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 L.I. D. 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. 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 a proposed 4’ concrete pan on site and into 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 4 basin by the L.I.D. swales 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. Water quality for the site is also provided by routing runoff through a Bay Saver sediment trap downstream. 4. EROSION CONTROL 4.1. General Concept This site lies within the Moderate Rainfall and Wind Erodibility Zone per the City of Fort Collins. Potential also exists for tracking of mud onto existing streets which could then wash into existing storm systems. See drainage and erosion control plan for proposed measures to control the movement of sediment off site to the public streets and existing storm sewer system. 4.2. Specific Details Specific details regarding erosion control will be provided with the final drainage and erosion control report for this site. 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. 5 If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit will be required. 6 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