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Home My WebLink AboutSTODDARD PROPERTY - OVERALL DEVELOPMENT PLAN - 42-00 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTStoddard Property ODP. Jim Sell Design, Inc.. J2017 916/00 EMS - Table A.5: DetenUon Pond Volume Calculations Note: 100-year intensity data referenced from City of Fort Collins Stone Drainage Design Criteria and Construction Standards Manual, revised 1999 Pond 1 Duration min Composite C Cf 100 Yr. Intensity inRu Area (ac) Q100 cfs) In1 Volume cu-ft Released Volume @ lcfs per acre 41.09 Pond Detention Volume cu-ft 5 0.59 1.25 9.95 41.09 301 90,412 - 12,328 78.084 10 0.59 1.25 7.72 41.09 234 140,297 24,656 115.642 15 0.59 1.25 6.52 41.09 197 177,734 36,983 140,751 20 0.59 1.25 5.60 41.09 170 203.540 49.311 154,229 25 .0.59 1.25 - 4998 41.09 151 226.256 61,639 164.617 . 30 0.59 1.25 4.52 41.09 137 246,429 73,967 172,462 35 0.59 1.25 4.08 41.09 124 259,513 86,295 - 173,219 40 0.59 1.25 3.74 41.09 113 271,871 96,623 173,249 45 0.59 1.25 3.46 41.09 105 282,957 110,950 172.006 50 0.59 1.25 3.23 41.09 98 293,497 123.278 170,219 55 0.59 1.25 3.03 41.09 92 302,857 135.606 167,250 60 0.59 1.25 2.86 41.09 87 311.852 147,934 163,918 Required Storage Volume = 173,249 or In Acre Feet = 3.98 :Stoddard Property ODP Jim Sell Design, Inc. J2017 9/6/00 EMS Table AA: Storm Drainage System Design: Rational Method Procedure: 100-Year Developed 100 YEAR DEVELOPED STREET DESIGN POINT DIRECT RUNOFF TOTAL RUNOFF OVERLAND PIPE TRAVEL TIME COMMENTS Area ID Area (ac) Runoff Coeff. Cf tc (min) CA (ac) I (in/hr) Q (cfs) tc (min) CA (ac) 1 (inRv) 0 (cfs) Slope (%) Street Flow (cfs) Design Flow (cfs) Slope (%) Pipe Size Length (ft) Velocity (ft/sec) Tt (min) 1 1 41.09 0.59 1.25 17.78 24 8.01 182.00 14.12 24 6.01 182 2.0 1000 1.18 14.124 Stoddard Property ODP Jim Sell Design, Inc. J2017 9/6/00 EMS Table A.3: Intensity -Duration Interpolations Stone Duration 2yr 5yr 100yr (in/hr) (in/hr) (in/hr) 5 2.85 4.87 9.95 10 2.21 3.78 7.72 15 1.87 3.19 6.52 20 1.61 2.74 5.60 25 1.43 2.44 4.98 30 1.30 2.21 4.52 35 1.17 2.00 4.08 40 1.07 1.83 3.74 45 0.99 1.69 3.46 50 0.92 1.58 3.23 55 0.87 1.48 3.03 60 0.82 1.485 2.86 Design Point Area ID Area (ac) Runoff Coefficient CC tc (min) Intensities 2yr (in/hr) 5yr (in/hr) 100yr (in/hr) 1 1 41.09 0.59 17.78 1.73 2.94 6.01 Design Point Area ID Area (ac) ff ient ;Of..f5c(,9 tc (min) Intensities 2yr (in/hr) 5yr (in/hr) 100yr (in/hr) 1 41.09 17.78 1.62 2.72 5.60 Stoddard Property ODP Jim Sell Design, Inc. J2017 9/6/00 EMS Table A.2: Standard Form: Developed Time of Concentration Timn of r:nnr Sub -Basin Data Initial / Overland Time (f i) Travel Time (TO Final Tc Urban Basins Tc Check Final Tc Design Pt. Coeff. CC Area (ac) Length 00 Slope (°h) Ti (min) Length (ft) I Slope (%) Grass or Pavement Velocity (ftlsec) Tt (min) (min) Length c=(LI180) +10 (min) 1 0.59 41.09 100 2.00 7.3 1300 1.00 p .00 10.8 18.1 1400 17.8 17.8 Stoddard Property ODP Jim Sell Design, Inc. J2017 9/6/00 EMS Table A.1: Composite Runoff Coefficients Sub -Basin ID Surface Description Area (sq ft) Area (ac) Total Area (ac) Area N 2-year Runoff Coefficienl CC Weighted Runoff Coefficien CC 1 Residential 1,100,000 25.25 61.45 1 0.65 0.40 Commercial - 0.00 0.00 1 0.95 0.00 Streets/Parking 240,000 5.51 13.41 0.95 0.13 Landscaping 450,000 10.33 25.14 0.25 0.06 41.09 100.00 0.59 Vicinity Map Tor the Lower Dry Creek Basin . Overall Drainage Report Stoddard Property ODP REFERENCES Major Drainage way Planning, Dry Creek. Gingery Associates, Inc, April 1980. Hydrologic Model Update for the Lower Dry Creek Basin Master Drainage Plan, Lidstone & Anderson, Inc, September 1997 Storm Drainage Design Criteria and Construction Standards, Department of Public Works and Water Utilities, City of Fort Collins, Colorado, May, 1984 Urban Storm Drainage Criteria Manual, Denver Regional Council of Governments, dated 1969, Volumes 1, 2, & 3 Overall Drainage Report 2 Stoddard Property ODP Drainage and Flood Control District, was also referenced in the preparation of this report. Drainage and Pond sizing calculations are presented in Appendix A. Required pond volumes presented in the Lidstone report were modified for the site to reflect increases in rainfall intensity curves and imperviousness. For preliminary sizing requirements, the Rational Method was used. The Rational Method, widely accepted for design of sub -basins less than 160 acres, was appropriate for the site, as the total area is approximately 41 acres. According to the City of Fort Collins Storm Drainage Design Criteria and Construction Standards Manual, runoff volumes are to be calculated for the major event (100 year return period for commercial and/or residential land use) for detention storage. 1-hour, 5-minute storms, as referenced from Figure 3- 1a from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards Manual, were used to calculate intensities. DETENTION PONDS In addition, there have been updates to the City of Fort Collins Rainfall Intensity - Duration Frequency Curves in 1999. As a result, rational method calculations are presented with this report to conceptually size detention facilities necessary for the proposed development. A revised SWMM model sensitive to the aforementioned changes will be developed for accurate detention pond sizing and runoff routing for the preliminary and final drainage analyses. CONCLUSIONS The Stoddard Property ODP, overall drainage report has been designed to comply with present City of Fort Collins Storm Drainage Design Criteria and Construction Standards Manual. The drainage calculations presented in this report are intended conceptual sizing of necessary on -site detention facilities for the Stoddard Property ODP site. Overall Drainage Report 1 Stoddard Property ODP INTRODUCTION This report was prepared to meet requirements for the Overall Drainage Report as specified in the City of Fort Collins Development Manual, and is in accordance with the City of Fort Collins Storm Drainage Criteria Manual. Included herein are the project description, identification of previous studies, historic and developed conditions, and a detention storage analysis for the 100-year event. LOCATION AND DESCRIPTION The Stoddard Property ODP lies in the Northwest Quarter of Section 8, Township 67 North, Range 68 West of the V' Principal Meridian in the City of Fort Collins in Larimer County, Colorado. The site is approximately 41 acres, and has multi -family residential, and single-family residential proposed uses. The site is presently being used as a grazing pasture, with the Lake Canal. winding near the east edge of the property towards the South. The site is bounded on the south by the Industrial Business Park International PUD, on the East by The Collins Air -Park Mobile Home Court, on the North by Burlington Northern Railroad's switching yard and to the west by The Dry Creek Mobile Home Park. Access is currently only available by the proposed extension of Morocco Drive north into the site from Zuric Drive. Previous Studies The project lies within the Dry Creek Drainage Basin. This basin was analyzed in 1980 by Gingery Associates, Inc. in the Major Drainage way Planning, Dry Creek. Lidstone & Anderson, Inc performed a Hydraulic Model Update for the Lower Dry Creek Basin, Master Drainage Plan in 1997. It incorporated a SWMM model including runoff and detention storage calculations for developed conditions for the areas downstream of the Larimer & Weld Canal, which includes the Stoddard Property ODP site. Relevant information from the Lidstone 1997 report has been included in the appendix of this report. Existing Conditions Currently, the site is used for grazing and/or agricultural purposes. Areas not used for agricultural purposes primarily contain natural grasses. Some wetlands have developed offsite to the south. Much of the Basin maintains open space and agricultural use to the north, however significant residential and commercial land use exists on all other sides of the site. The Stoddard Property ODP site generally slopes to the south and west with slopes ranging from roughly 1 to. 2 percent. Historically, drainage patterns on the property directed runoff to the southeast to Dry Creek. Drainage Plan Development This drainage report was prepared to conform with the City of Fort Collins Storm Drainage Design Criteria and Construction Standards Manual (May 1984, revised in April 1999). The Urban Storm Drainage Criteria Manual, prepared by the Urban CONCEPTUAL DRAINAGE LETTER REPORT FOR STODDARD PROPERTY ODP North of Zuric Drive and Morocco Drive Fort Collins, .Colorado Prepared for John W. Stoddard 6051 Happy Canyon Dr. Englewood CO 80111 JIM SELL DESIGN, INC. 153 W. Mountain Avenue Fort Collins, Colorado 80524 (970) 484-1921, FAX (970) 484-2443 Jim Sell Design, Inc. Project No. J2017 September 2000 September 11, 2000 Mr. Basil Harridan City of Fort Collins Storm Water Utilities Department P. O. Box 580 Fort Collins, Colorado 80522-0580 RE: Stoddard Property ODP Dear Mr. Hamdan, Please refer to our enclosed "Conceptual Drainage Letter Report for Stoddard Property ODP." This report was prepared to meet requirements for the Overall Drainage Report as specified in the City of Fort Collins Development Manual. The report has been prepared to be in accordance with the City of Fort Collins Storm Drainage Criteria Manual. Included herein is a project description, identification of previous studies, historic and developed conditions, and a detention storage analysis. Please call if you have any questions regarding this report. We thank you for your time and consideration in reviewing this drainage report submittal. Sincerely, JIM SELL DESIGN, INC. Les Crawford, P.E. Director of Engineering CC: file Enclosure OVERALL DRAINAGE LETTER REPORT FOR STODDARD PROPERTY ODP North of Zuric Drive and Morocco Drive Fort Collins, Colorado Prepared for John W. Stoddard 6051 Happy Canyon Dr. Englewood CO 80111 Lanr,unpe Ardxiecture E Planaigq