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Home My WebLink AboutGOLDEN MEADOWS BUSINESS PARK - PDP - 14-03 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTIt 14 -63 67 Mez;,Av We-3 iu. a� 1 i PROJECT LOCATION 0 �Y M VICINITY MAP APPROXIMATE SCALE: 1' - 600- I i i APPENDIX A I VICINITY MAP I I 11 I I I I a A j I 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 and the Storm Drainage Design Criteria Manual. Requirements placed on the site related to the new rainfall criteria have been followed. No variances are required for the project. 6.2 Drainage Concept The proposed drainage concepts presented in this report and on the construction plans adequately provide for stormwater quality treatment of proposed impervious areas. Conveyance elements have been designed to pass required flows and to minimize future maintenance. If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit will be required. 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 June 2001, and Volume 3 dated September 1999. 3. "Fox Meadows Basin Drainage Master Plan Update Baseline Hydrology Report" by ICON Engineering dated January 31, 2002. 5 i I channel running through the basin. This basin will not reach the proposed detention and water quality pond. The pond has been sized to account for this area free releasing. 4.3 Drainage Summary Drainage facilities located outside of the right of way (including the water quality pond, existing and proposed storm drain system and the pond outlet) will be maintained by the owners of the property. 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. The potential exists for silt movement from the site and into the existing swale along Harmony Road. Potential also exists for tracking of mud onto existing streets which could then wash into existing storm systems. The required performance standard for the site is 79.4%. During construction and after final paving and building construction, this figure has been exceeded with the use of silt fence, straw bales and by using the water quality pond and a sediment trap during construction. The erosion control escrow amount is $8,385. 5.2 Specific Details To limit the amount of silt leaving the site several erosion control measures shall be implemented during construction. Straw bales will be used where appropriate, and the south and east boundaries shall have silt fence installed. A vehicle tracking pads shall be installed at the proposed connection to McMurray Avenue 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. The water quality pond will be used as a sediment trap during construction. 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. Detention volume was determined using the FAA or Rational Method. Water quality volume was calculated using the method recommended in the "Urban Storm Drainage Criteria Manual". 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 included in Appendix C of this report. 1 4. DRAINAGE FACILITY DESIGN 4.1 General Concept The majority of the proposed development will be routed via sheet and gutter flow to the proposed detention and water quality pond in the northeast comer of the site. The pond releases to the existing channel on the south side of the site. The remaining portion of the site sheet flows to this channel. 1 4.2 Specific Flow Routing A summary of the drainage patterns within each basin is provided in the following paragraphs. Basin 1 includes the majority of the improvements to the site. The north half of the building and all of the proposed parking is within this basin. This basin sheet flows to the north to a concrete pan. The pan discharges into the detention and water quality pond. This pond discharges to the existing swale on the south side of the site. Basin 2 includes the south half of the building and the existing 80' utility and drainage easement on the south side of the site. This basin drains via sheet flow to the existing 1 3 I 2.2 Sub -basin Description This site drains to the Golden Meadows Detention Pond by way of the swale on the south side of the site. This drainage path will be maintained with the development of this site. In the Fox Meadows Master Plan, this site is in basins 400 and 405. These basins appear to be delineated incorrectly in the master plan. This entire site as well as a portion of the site to the north drains to the swale along Harmony Road. This discrepancy does not change the requirements for this site. 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 the requirements of the City Stormwater Department. Detention is provided for this site in the Golden Meadows Detention Pond, but this facility was sized with the old rainfall criteria. This site is required to detain to the 100-year rate as calculated with the old (pre-1999) rainfall criteria. Water quality facilities are required for the new construction proposed on the site. It was determined that the "old" 100-year release for the site was 12.3 cfs. The detention pond was designed so that the proposed release from the site will match this value. 3.3 Hydrologic Criteria Runoff computations were prepared for the 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 1 2 I 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location Golden Meadows Business Park, Filing 2 is located in southeast Fort Collins. Filing 2 is a replat of Lot 5 and a portion of Lot 4, Golden Meadows Business Park. This project is located in the southeast quarter of Section 31, Township 7 North, Range 68 West of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. See the location map in Appendix A. The project is located at the northeast corner of Harmony Road and McMurray Avenue. The project is bounded on the north by a vacant office building and parking lot, on the east by the existing Grainger building, on the south by Harmony Road and on the west by McMurray Avenue. 1.2 Description of Property The entire project consists of approximately 1.9 acres of land; only 1.3 acres of the property is developable because of an existing 80' utility and drainage easement on the south side of the property. This easement contains an 8" waterline, a 36" waterline, a major drainage swale running east to the Golden Meadows Detention Pond and several other utilities. One commercial building is proposed for the site with associated parking and drives. The land currently slopes to the south and west at a range of approximately 0.5% to 1.0%. There are existing swales on the south and east sides of the property that convey all existing flows to the southeast corner of the site. There are no mapped floodplains on the property. 1 2. DRAINAGE BASINS AND SUB -BASINS 1 2.1 Major Basin Description The proposed development lies within the Fox Meadows Master Drainage Basin. The Updated Master Drainage Plan for this Basin has been completed by Icon Engineering, Inc. I E TABLE OF CONTENTS ITABLE OF CONTENTS............................................................................................................... iii 1. 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..................................................................................................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 ' 5. EROSION CONTROL 5.1 General Concept......................................................................................................4 5.2 Specific Details........................................................................................................4 6. CONCLUSIONS 6.1 Compliance with Standards....................................................................................5 6.2 Drainage Concept.....................................................................................................5 7. REFERENCES....................................................................................................................5 APPENDICES A Vicinity Map B Hydrologic Computations C Hydraulic Calculations D Detention and Water Quality Pond Sizing E Erosion Control Calculations F Figures and Tables Ill North Star �`, de -sign, inc. L IMarch 11, 2003 Basil Hamdan City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522-0580 RE: Final Drainage and Erosion Control Study for Golden Meadows Business Park, Filing 2 Dear Basil, I am pleased to submit for your review and approval, this revised Final Drainage and Erosion Control Study for Golden Meadows Business Park, Filing 2, a Neighborhood Convenience Shopping Center proposed at Harmony Road and McMurray Avenue. 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. ISincerely, I Michael Oberlander, P.E., L.S.I. I ii 700 Automation Drive, Unit I Windsor, Colorado 80550 970-686-6939 Phone • 970-686-1188 Fax FINAL DRAINAGE AND EROSION CONTROL STUDY GOLDEN MEADOWS BUSINESS PARK FILING 2 Prepared for: Stoner and Company 2815 East Harmony Road Fort Collins, CO 80528 Prepared by: North Star Design 700 Automation Drive, Unit I Windsor, Colorado 80550 (970) 686-6939 March 11, 2003 Job Number 186-01 w