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Home My WebLink About302 N. MELDRUM ST., CHANGE OF USE - MINOR AMENDMENT - 23-99 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORT3.2 Drainaze Plan Develooment 7A The proposed drainage plan consists of placing vertical curb and gutter across the entire site along Maple Street. From the top back of curb there will be a decorative rock area approximately 10 feet wide. From the north edge of the rock area will be a 5 foot detached walk. North of the 5' detached walk will be a 10' wide strip of turfed landscape. By the east existing stairway, a 16' x 30' landscape area with walkway is proposed. The asphalt parking area will have a high point at the northeast corner. Approximately 20% of the parking lot will drain west to Meldrum Street. The other 80% will drain south and southwest to a 4 foot pan that enters a 4 foot sidewalk culvert (refer to Appendix B for design of this culvert). After the culvert it enters a 4 foot pan that travels south to a 4 foot curb cut in Maple Street. The runoff will then proceed east down Maple Street. It was determined that the flow during a 100-year event was approximately 0.96 cfs within -� the area of proposed improvements. Please refer to Appendix A for the calculations on this data. 3.3 Erosion/Sediment Control Plan This site is extremely small and flat so we do not anticipate a problem with erosion and water quality during construction. However, gravel curb inlet filters will be placed and maintained at the nearest inlets on Meldrum Street and Maple Street to keep any sediment from entering the storm sewer. 3.0 Developed Conditions Plan 3.1 Design Criteria The drainage system presented in this report has been developed in accordance with the guidelines established by the City of Fort Collins Storm Drainage Design Criteria Manual (SDDCM) with the latest revision dated November 4, 1998. Developed condition hydrology was evaluated based on the 100-year storm frequency as dictated by Section 3 of the SDDCM manual. Minor storm calculations were not performed due to the extremely small size of the site. The Rational Method was selected to calculate runoff for street capacity analysis. The Rational Method utilizes the SDDCM manual equation: Q = C,CIA where Q is the flow in cfs, Cf is the storm frequency adjustment factor, C is the runoff coefficient, I is the rainfall intensity in inches per hour, and A is the total area of the basin in acres. Since the calculations are for the 100-year storm, Cf was taken from Table 3-4 of the SDDCM. The runoff coefficient, C, was selected from Table 3-3 of the SDDCM manual based on the developed condition land use. The appropriate rainfall intensity was taken from the revised rainfall intensity duration table provided by the City of Fort Collins. To obtain the rainfall intensity, the time of concentration had to be determined. The following equation from section 3.1.7 of the SDDCM manual was utilized to determine the time of concentration: T� = [1.87(l.1 — CQDosj/(S)o.33 where D is the length of basin in feet, S is the average basin slope in percent, C is the Rational Method runoff coefficient, and Cf is the frequency adjustment factor. This procedure for computing time of concentration allows for overland flow as well as travel time for runoff collected in streets, gutters, channels, pipes, or ditches. Using these parameters and equations, the peak flow was calculated for the site runoff. Please refer to Appendix A for the calculations. 0 I ° 4 3 ZO Historic Conditions The site is an existing vacant building with approximately 7,188 square feet of gravel parking to the south of the building which lies entirely within the Downtown Basin. The site is bounded to the West by Meldrum Street which has existing curb and gutter flowing north and a 5' detached walk. The site is bounded to the South by Maple Street which has an existing crosspan flowing east across the entire site. The current drainage pattern is difficult to determine because the site is relatively flat. The topography of this site ranges from 0.5% to 1.5% with several depressions where there is a possibility of no drainage. It appears that the historic drainage flows approximately 20% to Meldrum Street and 80% to Maple Street. This site was analyzed for historic runoff for the 100-year storm. It was determined that the flow during a 100-year event q was approximately 1.02 cfs within the area of proposed improvements. Please refer to Appendix JA for the calculations on this data. 9 FIGURE I OWN IN I soon 1111mmomn" INV" Nip 5,MELIA a polip 1 His as owl m gmagg MO4'�:�11■�Ym►l�`\\\\t1. RMONISM= VICIAll T Y MAP Scale r -= 2000' 1.0 1 Introduction 1.1 Scope and Purpose This report presents the results of a Final Drainage Evaluation for the Change of Use at 302 North Meldrum Street in the City of Fort Collins, Colorado. In accordance with the requirements of the City of Fort Collins, the purpose of this report is to present a storm drainage plan that identifies peak runoff conditions and provides a means by which to safely collect and convey runoff across the site. This report will evaluate hydrologic conditions for the existing site and will use that information for hydraulic analysis of the proposed parking and landscape facilities. 1.2 Proiect Location and Description The project consists of an existing building and gravel parking lot on the west half of Lots 15 and 16, Block 43, of the City of Fort Collins, County of Larimer, State of Colorado. The total area of Lots 15 and 16 is approximately 24,563 square feet. The portion of this site where improvements will be made consists of approximately 7,188 square feet. The site is bounded on the West by Meldrum Street, the South by Maple Street, the North by residential, and the East by Hefner Dean Printing. A vicinity map illustrating the project location is provided in Figure 1.Figure 1 Vicinity Map 1 TABLE OF CONTENTS 1.0 Introduction Page 1.1 Scope and Purpose.........................................................................................................1 1.2 Project Location and Description..................................................................................1 2.0 Historic Conditions................................................................................................................3 3.0 Developed Conditions Plan . 3.1 Design Criteria...............................................................................................................4 3.2 Drainage Plan Development..........................................................................................5 3.3 Erosion/Sediment Control Plan.....................................................................................5 Figures Figure1 - Vicinity Map...................................................................................................................2 Technical Appendices Appendix A - Historic / Developed Runoff Appendix B — Sidewalk Culvert Design Sheets Grading and Drainage Plan ii ' April 30, 1999 �1 Mr. Basil Hamden City of Fort Collins Utilities P.O. Box 580 Fort Collins, CO 80522 I Re: Change of Use at 302 North Meldrum Street Project No. 0900-041 Dear Mr. Hamden: We are pleased to submit this Final Drainage Report for the Change of Use at 302 North Meldrum Street. The report was prepared based on City of Fort Collins drainage criteria and we believe it satisfies the criteria for a final report. We look forward to your review and comments and will gladly answer any questions you may have. Respectfully, TST, INC. C( Mike R.10 MRJ/tdy Enclosure ENGINEERS David B. Lindsay, P.E. TST, INC. 748 Whalers Way - Building D 102 Inverness Terrace East Fort Collins, CO 80525 Suite 105 ConsuRing Engineers (970) 226-0557 Englewood, CO 80112 Metro (303) 595.9103 i (303) 792-0557 Fax (970) 226.0204 Fax (303) 792-9489 *-z Email info@tstinc.com www.tstinc.com I FINAL DRAINAGE REPORT FOR 302 NORTH MELDRUM STREET Submitted to: CITY OF FORT COLLINS APRIL 30, 1999