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hour. Applying the rational method produced a peak runoff of 3.3 cfs. Subbasin RB 15 would be <br />captured by Pond 5B and would no longer contribute runoff to DP5. <br />Subbasin RB16 will be predominately grassland with an area of 4 acres. The imperviousness of the <br />subbasin is 0 percent. The runoff coefficient was calculated to be 0.480 for the 100-year storm. A <br />time of concentration of 78 minutes would result in a 100-year rainfall intensity of 2.35 inches per <br />hour. Applying the rational method produced a peak runoff of 4.7 cfs. Subbasin RB 16 would be <br />captured by Pond 5A and would no longer contribute runoff to DP5. <br />Subbasin RB17 will be predominately grassland with an area of 12 acres. The imperviousness of <br />the subbasin is 0 percent. The runoff coefficient was calculated to be 0.440 for the 100-year storm. <br />A time of concentration of 88 minutes would result in a 100-year rainfall intensity of 2.16 inches <br />per hour. Applying the rational method produced a peak runoff of 11.2 cfs. Subbasin RB 17 returns <br />to the Cache la Poudre River as overland flow at DP5. Elimination of Subbasin RB15 and Subbasin <br />RB 16 runoff from contributing to DP5 is the major cause of the reduction from the historical peak <br />flow rate of 20.2 cfs down to the reclaimed peak flow rate of 11.2 cfs. <br />Pond 1B has a surface area of 5 acres and an available storage volume for storm water capture of <br />16.8 acre-feet above the normal pool. The contributing drainage area to this pond includes <br />Subbasin RB6 for a total drainage area of 57 acres. <br />Pond 2A has a surface area of 14 acres and an available storage volume for storm water capture of <br />30.5 acre-feet above the normal pool. The contributing drainage area to this pond includes <br />Subbasin RB4 for a total drainage area of 52 acres. <br />Pond 4A has a surface area of 5 acres and an available storage volume for storm water capture of <br />10.8 acre-feet above the normal pool. The contributing drainage area to this pond includes <br />Subbasin RB8 for a total drainage area of 8 acres. <br />Pond 4B has a surface area of 9 acres and an available storage volume for storm water capture of <br />31.9 acre-feet above the normal pool. The contributing drainage area to this pond includes <br />Subbasin R139 for a total drainage area of 18 acres. <br />Pond 4C has a surface area of 16 acres and an available storage volume for storm water capture of <br />36.8 acre-feet above the normal pool. The contributing drainage area to this pond includes <br />Subbasins RB2 and RB 18 for a total drainage area of 62 acres. <br />Pond 5A has a surface area of 2 acres and an available storage volume for storm water capture of <br />18.2 acre-feet above the normal pool. The contributing drainage area to this pond includes <br />Subbasin RB16 for a total drainage area of 6 acres. <br />Pond 5B has a surface area of 7 acres and an available storage volume for storm water capture of <br />52.9 acre-feet above the normal pool. The contributing drainage area to this pond includes <br />Subbasin RB15 for a total drainage area of 9 acres. <br />-12- Revised Preliminary Drainage Report.doex