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December 22, 1986 <br />- frrf 9F <br />6.iy <br />2. �jj1 <br />CALCULATIONS: <br />Detention Pend Sub -Watershed Area = 4.43 Ac. <br />100 Yr. - 24 Hr. Rainfall; P100 = 5.9 inches <br />Coefficients of runoff; <br />undeveloped c = 0.1.5 <br />devel-,ied ^. = 0.20 <br />A. Pre -Developed Total Runoff. (100 Yr.) <br />R100 = 0.15 (5.9") (1'/12") (4.43 Ac.) - 0.33 <br />Ac. Ft. <br />This entire volume of water eventually enters <br />the natural low <br />area to the north of the Red Oak Properties. <br />B. Poet -Developed Total Runoff (100 YR.) <br />R100 = 0.30 (5.9") (1'/12") (4.43 Ac.) = 0.65 <br />Ac. Ft. <br />I In the event that outflow from the detention area <br />is prevented by the <br />1 operation of the check valve, the detention area <br />will be able to store <br />0.37 Ac. Ft. (The Detention Area Volume). The <br />remaining runoff will <br />spill over the emergency overflow and enter the natural low area to <br />the north of the Red Oak Property. <br />Remaining Runoff; <br />0.65 Ac. Ft. - 0.37 Ac. Ft. - 0.28 Ac. Ft. <br />Conclusion; <br />Runoff volume to natural lcw area to the north of Red Oak Site, <br />Pre -Development 0.33 Ac. Ft. <br />Post -Development = 0.28 Ac. Ft. <br />In this worst -case scenario we would not be negatively impacting <br />the natural low area.; In fact we would be improving the <br />drainage problem that already exists. <br />