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Home My WebLink AboutHUGH M WOODS PUD - PRELIMINARY - 26-88D - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT;LIMINARY DRAINAGE STUDY FOR 'FH M. WOODS DEVELOPMENT, ORT COLLINS, COLORADO ■ ■ ■ 0 ■ L a RBD, Inc. Engineering Consultants 209 South Meldrum Fort Collins, Colorado 80521 (303) 482-5922 RBD Job No. 638-001 0 IWIMC. Engineering Consultants 209 S. Meldrum Fort Collins, Colorado 80521 303/482-5922 FAX:303/482-6368 September 12, 1994 Mr. Glen Schlueter City of Fort Collins Utility Services Stormwater 235 Mathews Street Fort Collins, Colorado 80522 RE: Preliminary Drainage Study for Hugh M. Woods Development Dear Glen: We are pleased to submit to you, for your review and approval, this Preliminary Drainage Study for the Hugh M. Woods Development. All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. We appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Respectfully, RBD Inc. Engineering Consultants Prepared by: David K. Thaemert, E.I.T. Water Resources Engineer Ms. Kay Force Mr. Barry Hilton Reviewed by: Stan A. Myers, P.E. Project Manager in Denver 303/458-5526 TABLE OF CONTENTS DESCRIPTION PAGE I. GENERAL LOCATION AND DESCRIPTION 1 A. Location 1 B. Description of Property 1 H. DRAINAGE BASINS 1 A. Major Basin Description 1 B. Sub -basin Description 1 III. DRAINAGE DESIGN CRITERIA 2 A. Regulations 2 B. Development Criteria Reference and Constraints 2 C. Hydrological Criteria 2 D. Hydraulic Criteria 2 E. Variances from Criteria 2 IV. DRAINAGE FACILITY DESIGN 2 A. General Concept 2 B. Specific Details 3 V. STORM WATER QUALITY 3 A. General Concept 3 VI. EROSION CONTROL 3 A. General Concept 3 VII. CONCLUSIONS 3 A. Compliance with Standards 3 B. Drainage Concept 4 REFERENCES 4 APPENDIX VICINITY MAP 2 HYDROLOGY 3 DETENTION 1 DESIGN OF INLETS, STORM SEWER AND SWALES 14 CHARTS, FIGURES AND TABLES 28 PRELIlVIINARY DRAINAGE STUDY FOR THE HUGH M. WOODS DEVELOPMENT, FORT COLLINS, COLORADO I. GENERAL LOCATION AND DESCRIPTION A. Location The Hugh M. Woods development is bounded by Foothills Gateway on the west, Skyway Drive on the north, South College Avenue (U.S. Highway 287) to the east, and by Trilby Road and the remaining Timan P.U.D. on the south. The site location can also be described as situated in Section 11, Township 6 North, Range 69 West of the 6th P.M., City of Fort Collins, Larimer County, Colorado. The site location can be seen on page 2 of the Appendix. B. Description of Property The Hugh M. Woods development contains approximately 16.4 acres, more or less. Presently, the property is undeveloped. The property is being proposed for commercial development within the City of Fort Collins Zoning District and will be developed consistent with the Timan P.U.D. Master Plan. Native grasses presently cover the property. The topography of the site generally slopes from west to east at approximately 5.1 percent. H. DRAINAGE BASINS A. Major Basin Description The proposed development lies within the Fossil Creek Drainageway. A lateral of the Louden Irrigation Ditch runs along the upper, western boundary of the project. Runoff from the project area is routed by open channels and culverts along the western edge of College Avenue or under College Avenue by existing culverts. B. Sub -basin Description The Hugh M. Woods development has been divided into 12 sub -basins. All 12 basins will be developed consisting of proposed commercial buildings and street improvements. These sub -basins are shown on the Preliminary Grading and Drainage Plan in the back pocket of this report. 4 A M. DRAINAGE DESIGN CRITERIA A. Regulations The City of Fort Collins Storm Drainage Design Criteria is being used for the subject site. B. Development Criteria Reference and Constraints Runoff from this site is limited to the 2-year undeveloped flow condition. Additional runoff is detained on -site and released at the 2-year undeveloped flow rate. C. Hydrological Criteria The Rational Method for determining surface runoff was used for the project site. The 2-year, 10-year, and 100-year storm event criteria, obtained by the City of Fort Collins, were used in calculating runoff values. The 2-year storm event was used only to determine allowable runoff based on historic conditions. These calculations and criteria are included in the Appendix of this report. D. 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 the Appendix. E. Variances from Criteria No variances are being sought for the proposed project site. IV. DRAINAGE FACILITY DESIGN A. General Concept The on -site runoff produced by the proposed Hugh M. Woods development will flow easterly to the potential on -site detention pond. The outflow from this potential detention pond is then routed east via the existing culvert underneath College Avenue. The proposed drainage, erosion control, and grading plans are included in the back pocket of this report. Pa �7 B. Specific Details The Hugh M. Woods development has been broken down into 12 sub -basins. Runoff from sub -basins 1 through 7 and 11 will be conveyed northeasterly towards College Avenue by a combination of gutter flows and a storm sewer system. Runoff from sub -basins 8 through 10 will be conveyed southeasterly towards College Avenue by gutter flows. At College Avenue, all developed runoff will be detained in an existing wetland area, then released in an existing culvert underneath College Avenue at the 2-year historic rate. The downstream culvert and storm improvements have the available capacity for the Hugh M. Woods development. V. STORM WATER QUALITY A. General Concept Beginning in October 1992, the water quality of storm water runoff was required to be addressed on all final design utility plans. The Hugh M. Woods development is anticipating construction beginning in 1995. Therefore, final design for this project will determine applicable Best Management Practices for the treatment of storm water runoff. Existing wetlands on the downstream portion of the Hugh M. Woods site will provide a mechanism for pollutants to settle out of the storm water runoff before flows are directed further downstream. VI. EROSION CONTROL A. General Concept During final design for this site, appropriate measures will be designed to control erosion from the site. The first of these measures to limit erosion is to properly reseed all disturbed areas which will not be paved. All construction activities must comply with the State of Colorado permitting process for Stormwater Discharges Associated with Construction Activity. A Colorado Department of Health NPDES Permit will be required before any construction grading can begin. aVII. CONCLUSIONS A. 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 3 2. Sites and the Storm Drainage Design Criteria Manual. In addition, all computations are in compliance with the Timan P.U.D. Master Plan prepared by RBD, Inc. B. Drainage Concept The proposed drainage concepts presented in this report and on the construction plans adequately provide for the transmission of developed on -site runoff to the existing wetlands and drainage facilities at the eastern property line of the subject site. The combination of onsite street capacities in the curb and gutter and the onsite storm sewer system will provide for the 10-year and the 100-year developed flows to reach the existing wetlands and proposed detention pond. If, at the time of construction for some unforeseen reason, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit would be required. REFERENCES 1 2 Storm Drainage Design Criteria and Construction Standards by the City of Fort Collins, Colorado, May 1984, Revised January 1991. Timan P.U.D. Master Drainage and Utility Plan by RBD, Inc. Engineering Consultants. In u 4 4 APPENDIX 4 4 Ll 3 ----- vv yy . 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