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<br />.~ -4-- <br /> <br />. <br /> <br />. <br /> <br />MROED-HE <br />SUBJECT: <br /> <br />(1 Ju1 82) <br />Evaluation <br />Colorado <br /> <br />29 September 1982 <br />of Potential Water Supply Storage at Chatfield Reservoir in <br /> <br />c. Bear Creek. <br /> <br />(1) The original design of the flood storage space in the Bear Creek <br />reservoir was based On providing enough capacity to contain runoff from the <br />standard project flood and base flow with the outlet works shut down. To avoid <br />the risk of using the emergency spillway during a more frequent low inflow high <br />volume snowmelt flood and to reduce the cost of the rock excavation, the emergency <br />spillway crest was perched at 5667. <br /> <br />(2) Reevaluation of the flood storage requirement was based on controlling <br />the 500-year 60-<lay in!',~w wit:~ the release criteria presented in the DM. The 500- <br />year yo1ume was based on an updated analysis of "n" day volumes at the Morrison and <br />Sheridan gaging stations. Total storage required for the 500-year routing was <br />40,000 acre-feet. Total storage available at 5667 is 55.300 acre-feet. Storage <br />excess is 15,300 acre-feet. <br /> <br />2. Any questions concerning the results of these studies should be directed to <br />Wally Stern, ext 4582. <br /> <br />/ <br /> <br />/~/Sd~i! <br /> <br />R. G. BURNErf . <br />Chief, Engineering Division <br /> <br />4 <br />