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Home My WebLink AboutRIVERBEND - PDP - 39-01 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTI I I I S I I I I SCALE: 1" = 300' PROJECT SITE BENCHMARK: NORTHWEST CORNER OF SECTION 17—T7N—R68W FOUND 3-1/4" ALUMINIUN 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: 08/28/01 %North Star SCALE: 1" = 300' RIVERBEND ��. design, inc. CONDOMINIUMS 700 Automation Drive, Unit I DRAWN BY: TDS Windsor, Colorado 80560 VICINITY MAP Phone: 970-686-6939 JOB NO.: 157-01 Fax:970-686.1188 APPENDIX A VICINITY MAP 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. 7 0 11 I I G k I I I 11 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. C L r efficient measures wherever and as necessary proper 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. 1 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. 1 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. 1 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 is not substantial. Detention is being provided to meet requirements set by the City of Fort Collins Natural Resources Department. Sub -basin C contains % of the roof from the six-plex and the detention pond. The flow is detained and then released into the Poudre Ponds at a rate equal to the 2-yr historic storm event. - 4.3 Drainage Summary The 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 property owners. 4.4 Variance Requests INo 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 from 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. 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, vehicle -tracking pads 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 4 I 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. 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 is split by a high point near the entrance in the cul-de-sac. The street will slope to the west at approx. 2.0% and to the east at approx. 0.50%. A concrete tpan on Countryside Road will intersect the runoff flowing west. The flow is conveyed to the detention pond by a berm, constructed at the end of the street, to divert runoff from the street, under the sidewalk into the west portion of the detention pond. Flow to the east will be conveyed to the detention pond by an inlet located at the low point in the site. The runoff is conveyed through storm pipe along the east side of the building and into the northeast comer of 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 end of the cul-de-sac. Flow enters a Type-R inlet and is conveyed to the detention pond in a 15" RCP. Sub -basin B 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 the street north of the proposed property. Runoff from Sub -basin B is diverted at the south end of the street by a berm into a sidewalk culvert and into the detention pond. 3 l I 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), 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 east of this site in Countryside Road, however this site is designed to drain south into a detention pond and release to the Poudre Ponds. As currently proposed, this site will receive off -site flows from the east half of Countryside Road west of the proposed site. Countryside Road flows to the south and into the proposed detention / water quality pond. The west half of Countryside Road flows south to 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 0.76 cfs runoff in the 2 year storm, this is the proposed release rate for the detention pond. The site as it is 1 proposed will generate 9.8 cfs in the 100 year event. The site as designed has a 68% imperviousness. 3.3 Hydrologic Criteria Runoff computations were prepared for the 2-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 ' 2 1 I I 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location This site is located in a tract of land in the North %2 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. I I 1 2. 1 1 1 L 1 1 The project is located south of State Highway 14 and east of Timberline Road. The site is . bounded by Countryside Road to the north and west, 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 a two structures; one six unit building and one two unit building. Countryside Street will be the access point to this site. A cul-de-sac is included in the plans for proper traffic control. The developed site will include buildings, street and irrigated lawn. DRAINAGE BASINS AND SUB -BASINS 2.1 Major Basin Description The proposed development lies within the Poudre River Drainage Basin. The Stormwater Utility requires no detention. The Natural Resources Department has required that the site detain the 100 year developed runoff at 2 year historic rates and provide water quality. This requirement has been made by Natural Recourses because the outfall from the site is to a City Natural Area. 2.2 Sub -basin Description Sub -basins are described thoroughly in Section 4.2. 1 1 TABLE OF CONTENTS ' TABLE OF CONTENTS.............................................................................................................................iii 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location...............................................................................................................................I 1.2 Description of Property ........................................................................................................ I 2. DRAINAGE BASINS AND SUB -BASINS 2.1 Major Basin Description ...................................... '................................................................. 1 2.2 Sub -Basin Description.........................................................................................................1 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 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....................................................................................................................4 5.3 Dust Abatement...................................................................................................................4 . 5.4 Tracldng Mud......................................................................................................................5 5.5 Maintenance........................................................................................................................5 6. CONCLUSIONS 6.1 Compliance with Standards................................................................................................5 6.2 Drainage Concept................................................................................................................5 6.3 Water Quality and Erosion Control Concept.......................................................................6 7. REFERENCES.................................................................................................................................7 APPENDICES B C D I I Vicinity Map Hydrologic Computations Hydraulic Calculations Detention and Water Quality Calculations Figures and Tables iii I North Star �Atm., design, inc. August 28, 2001 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, Tro . Spraker, E.I.T. North Star Design, Inc. Reviewed By: k— &P4*claKroetc ii ' 700 Automation Drive, Unit I Windsor, Colorado 80550 970-686-6939 Phone • 970-686-1188 Fax FINAL DRAINAGE AND EROSION CONTROL REPORT RIVERBEND CONDOMINIUMS Prepared for: HARTFORD HOMES 1218 West Ash Windsor, CO 80550 Prepared by: North Star Design, Inc. 700 Automation Drive, Unit I Windsor, Colorado 80550 Ph# (970) 686-6939 Fax# (970) 686-1188 August 28, 2001 Job Number 157-01