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HomeMy WebLinkAboutRIVERBEND - FDP - 39-01B - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTF1 Ci I I 0 I 1 1 i PROJECT SITE BENCHMARK: NORTHWEST CORNER OF SECTION 17-T7N-R68W FOUND 3-1/4" ALUMINUM CAP IN MONUMENT BOX MARKED IS 17497" PROPERTY DESCRIPTION: A TRACT OF LAND IN THE N. 1 /2 OF SECTION 17, TOWNSHIP 7 NORTH, RANGE 68 WEST OF THE 6TH P.M., COUNTY OF LARIMER, STATE OF COLORADO. SHEET 1 OF 1 DATE: 03/28/03 %North Star SCALE: 1" = 300' RIVERBEND '�.. design, inc. CONDOMINIUMS 700 Automation Drive, Unit I DRAWN BY: TDS VICINITY MAP Windsor, Colorado 80550 Phone: 970-686-6939 JOB NO.: 157-01 Fax:970-686-1188 APPENDIX A VICINITY MAP i t . A 7. REFERENCES 1. City of Fort Collins, "Storm Drainage Criteria Manual", (SDCM), dated March, 1986. 2. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria Manual", Volumes 1 and 2, dated March, 1969, and Volume 3 dated September, 1992. i III rl I 5.4. Tracking Mud Wherever construction vehicles access routes intersect paved public roads, provisions shall be made to minimize the transport of sediment (mud) by runoff or vehicles tracking onto the paved surface. A stabilized construction entrance is required per the detail shown on the Detail Sheet with base material consisting of 6" coarse aggregate. The contractor will be responsible for clearing tracked mud on a daily basis. 5.5. Maintenance 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 fences will require periodic replacement. Maintenance is the responsibility of the contractor. 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 Storm Drainage Design Criteria Manual. 6.2. Drainage Concept The proposed drainage concepts presented in this report and on the construction plans adequately provide for the detention and transmission of developed on -site runoff to the Poudre Ponds. The impact of the development of this site on existing downstream facilities has been minimized by the use of detention and water quality ponds. Detention is provided to meet Fort Collins Natural Resources Department requirements. If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit would be required. 6.3. Erosion Control Concept Since the site is less than 5.0 acres, a NPDES permit is not required. During construction, erosion control shall be maintained to minimize erosion on this site and transport of silt downstream. 5 I 1 4.3. Drainage Summary tThe storm conveyance system is a surface and sub -surface system and has been designed for minimal maintenance. The, storm sewer system and the detention pond will be owned and maintained by the homeowners association. 4.4._ Variance Requests No variances are being requested at this time. 5. EROSION CONTROL 5.1. General Concept This site lies within the Moderate Rainfall and Wind Erodibility Zone per the City of Fort Collins Zone Maps. A potential exists for silt movement trom the site to be transported into the existing ponds located to the south of the site. All erosion control measures necessary to minimize sediment transport have been shown on the Erosion Control Plan, included in this report. 5.2. Specific Details To limit the amount of silt leaving the site, several erosion control measures shall be implemented during construction. Silt fence shall be installed along the southern side of proposed site. Also, a vehicle -tracking pad shall be installed at the entrance off Countryside Road to control the mud being tracked onto the existing pavement. During overlot grading, disturbed areas are to be kept in a roughened condition and watered to reduce wind erosion. 5.3. Dust Abatement During the performance of the work required by these plans, the contractor shall carry out proper sufficient measures wherever and as necessary to reduce dust nuisance, and to prevent dust nuisance, which has originated from his operations from damaging crops, orchards, cultivated fields and dwellings, or causing nuisance to persons. The Contractor will be held liable for any damage resulting from dust originating from his operations under these plans, on right-of-way or elsewhere. 4 3.4. Hydraulic Criteria All hydraulic calculations within this report have been prepared in accordance with the City of Fort Collins Drainage Criteria and are also included in Appendix C of this ' report. 4. DRAINAGE FACILITY DESIGN 4.1. General Concept The runoff from this site flows east from a high point at the entrance into the cul-de-sac. The flow line slopes to the east at. approximately 0.5% to a low point. Runoff flow will be collected in an inlet located at the low point and conveyed through a storm pipe ' along the east side of the building .and into the northeast comer of the proposed detention pond. Runoff generated by Countryside Road will flow south to a sidewalk culvert located near the entrance to the natural areas parking and will be conveyed to the ' proposed detention pond. 4.2. Specific Flow Routing A summary of the drainage patterns within each.basin is provided in the following paragraphs. 'For more specific details see the calculation located in Appendix B of this report. Sub -basin A contains the northeast portion of the site and runoff from this basin flows to the east to a low point located on the east portion of the cul-de-sac. Flow enters a ' Type-3 combination inlet and is conveyed to the detention pond in a 15" RCP. Sub -basin B contains '/z of the roof from the two southern buildings and the detention area. The flow is detained and released into the Poudre Ponds at a rate equal to the 2-yr historic storm event. Sub -basin C contains a portion of the site but primarily consists of the east half of Countryside Road from the south edge of the site to the intersection of Countryside Road and Countryside Drive. Runoff from Sub -basin C flows to a low point and is conveyed into the detention pond by a sidewalk culvert. Runoff is discharged into the northwest corner of the proposed detention pond. 3 i'^ I 3. DRAINAGE DESIGN CRITERIA t3.1. 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), 1984, developed by the Denver Regional Council of Governments, has been used. 3.2. Development Criteria Reference and Constraints The runoff from this site has been routed to conform to existing site constraints. Since this is an "established" area, with adjacent streets, natural areas and buildings already constructed, there is little room for varying from existing site conditions. ' The street and associated drainage systems surrounding the site are existing. The ' nearest storm system is approximately 150'to the west of this site on Countryside Road, however this site is designed to drain south into a detention pond and release into the Poudre Ponds. As currently proposed, this site will receive off -site flows from the east 1 half of Countryside Road west of the proposed site. The east half of Countryside Road flows to the south and into the proposed detention and water quality pond via a sidewalk ' culvert and grassed swale. The west half of Countryside Road flows to the west and into the Poudre Ponds through the existing storm sewer system without being detained. Detention is proposed for this site. The existing site (based on the rainfall criteria adopted by the City of Fort Collins on March 26, 1999) generates 0.96 cfs runoff in the 2-yr storm event; this is the proposed release rate for the detention pond. The site as it is proposed will generate a peak flow of 9.1 cfs in the 100-yr storm event. The site as designed has 63.5% imperviousness area. 3.3. Hydrologic Criteria Runoff computations were prepared for the 2-yr minor and 100-yr major storm frequency utilizing the rational method. All hydrologic calculations are included in Appendix B of this report. Standard Form 8 (SF-8) provides time of concentration calculations for all sub -basins. Standard Form 9 (SF-9) provides a summary of the ' design flows for all sub -basins and design points associated with this site. 1 2 1. GENERAL LOCATION .AND DESCRIPTION 1 1.1. 'Location This site is located in a tract of land in the North %z of Section 17, Township 7 North, Range 68 West of the Sixth Principal Meridian, in the City of Fort Collins, County of Larimer, State of Colorado. See the location map in Appendix A. The project is located south of State Highway 14 and east of Timberline Road. The site ` is bounded by Countryside Road to the west, an existing landscape business to the north, Erick Street to the east and the Poudre Ponds to the south. ' 1.2. Description of Property ' The entire project consists of 0.99 acres (43,153 sq.ft) of land. The land is currently undeveloped and slopes to the south at approximately 1%. The site currently drains ' overland to the Poudre Ponds to the south of this site. The project will consist of three structures including one 4 unit building and two 2 unit 1 buildings. The site will access Countryside Road on the western boundary of the site. A private cul-de-sac is included in the plans for proper traffic control. The developed site ' will include'buildings, street and irrigated lawn. 2. DRAINAGE BASINS AND SUB -BASINS 2.1. Major Basin Description The proposed development lies within the Poudre River Drainage Basin: The Natural Resources Department has required that this site detain the 100-yr developed event. This site shall also include water quality treatment before being discharged into the Poudre Ponds at a release rate equal to the 2-yr historic event (0.96 cfs.). This requirement has been made by the City of Fort Collins Natural Resources Department, a. due to the outfall from the site discharging directly into the City Natural Wetlands Area. 2.2. Sub -basin Description Sub -basins are described thoroughly in Section 4.2. 1 P IJ i 1 TABLE OF CONTENTS TABLEOF CONTENTS.............................................................................................................................iii GENERAL LOCATION AND DESCRIPTION 1.1 Location...............................................................................................................................1 1.2 Description of Property ........................................................................................................ I 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..............................................................................................................3 3.4 Hydraulic Criteria................................................................................................................3 4. DRAINAGE FACILITY DESIGN 4.1 General Concept..................................................................................................................3 4.2 Specific Flow Routing.........................................................................................................3 4.3 Drainage Summary ..............................................................................................................4 4.4 Variance Requests...............................................................................................................4 5. EROSION CONTROL 5.1 General Concept..................................................................................................................4 5.2 Specific Details....................................................................................................................5 5.3 Dust Abatement...................................................................................................................5 5.4 Tracking Mud......................................................................................................................5 5.5 Maintenance........................................................................................................................ 5 6. CONCLUSIONS 6.1 Compliance with Standards................................................................................................6 6.2 Drainage Concept................................................................................................................ 6 6.3 Water Quality and Erosion Control Concept.......................................................................6 1 7. REFERENCES.................................................................................................................................7 7 u APPENDICES A Vicinity Map B Hydrologic Computations C Hydraulic Calculations D Detention and Water Quality Calculations E Figures and Tables iii North Star �Aft., design, inc. July 17, 2003 Basil Hamdan City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522-0580 RE: Final Drainage Report for Riverbend Condominiums Dear Basil, I am pleased to submit for your review and approval, this Final Drainage & Erosion Control Report for Riverbend Condominiums. I certify that this report for the drainage design of Riverbend Condominiums 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, Troy D. Spraker, E.I.T. North Star Design, Inc. 700 Automation Drive, Unit I Windsor, Colorado 80550 970-686-6939 Phone 9 970-686-1188 Fax IFINAL DRAINAGE AND EROSION CONTROL REPORT RIVERBEND CONDOMINIUMS i Prepared for: [ HOORAZ, LLC. 1218 West Ash, Suite A Windsor, CO 80550 ' Prepared by: North Star Design, Inc. 700 Automation Drive, Unit I I Windsor, Colorado 80550 Phone: (970) 686-6939 Fax: (970) 686-1188 I July 17, 2003 Job Number 157-01 ..