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<br />I <br /> <br />I <br /> <br /> As Site With ~urb With Proposed <br /> Exists Repaired Action <br />Acres 10.15* 6.45 6.45 <br />Runoff Coefficient 0.1 0.39 0.6754 <br />Q2 " Rain** 0.67 0.42 0.73 <br />Q4 " Rain** 1. 35 0.84 1. 45 <br /> <br />I <br /> <br />I <br /> <br />II <br />I I <br />I <br />I <br /> <br />* 6.45 acres on-site + 40% of 9.25 acres off-site = 10.15 acres <br />** Q = runoff volume in acre feet <br /> <br />II <br />I <br /> <br />This rationale would indicate that the proposed <br />action, while not significantly increasing the rate <br />of discharge above tolerable levels, may increase <br />the volume of ultimate runoff above existing condi- <br />tions by 7.4%. If the curb on County Road E is <br />repaired, the runoff volume would be decreased by <br />perhaps 60%. <br /> <br />I <br /> <br />There are numerous other statistics of this nature <br />which may be developed but a final result of most <br />of the statistics are that if the action proceeds <br />as proposed after a 4" rainfall the downstream <br />receiving water will receive about 1.5 acre feet of <br />storage more than it presently does. Spread over <br />the 44 acre surface area of Silver Lake, it would be <br />implied that the elevation of Silver Lake may rise <br />one-half an inch as a direct result of a 4 inch rain- <br />fall on the proposed Windsor Center site. This one- <br />half inch rise would be an absolute maximum and, <br />based on rates of flow in and out of the lake, would <br />rarely occur. A four inch rainfall lasting one <br />day has approximately a 2% to 5% chance of occurring <br />on any given rainy day. That is, a 50 year storm <br />lasting 24 hours is likely to release 4.6 inches of <br />precipitation on the Watershed. By comparison, a <br />15 year, 24 hour storm would have about 3.5 inches <br />of rainfall. <br /> <br />,I <br />I <br />I <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />V-3 <br />