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<br />. <br /> <br />a. Chdcfielg.:n tile original reservoir design scu'Jies, chree hydrologic <br /> <br />conditions I.vl=re evaluated for this project. TivO conditions assumed rare COfn- <br /> <br />binations of rainfall runoff and mountain sno'..mJelt. Tne third condition <br /> <br />assun~j a standard project flood on top of 3 high starting pool. It was con- <br />cluded from these early 3tudies that 215,000 acre-feet flood storilge stJould be <br /> <br />the design flood control capacity in Chatfield. As a result of the reevalua- <br /> <br />tion by using the degree of protection discussed at the outset, the standard <br /> <br />project rainfall flood became the most critical event requiring a total flood <br /> <br />storage capacity of 182,000 3cre-feet. <br /> <br />b. B<2ar Creek. Th,e original reservoir design flood for "lp.ar Creek.. \./as <br /> <br />based on controlling the standard project rainfall flood event. Tnis required <br /> <br />a storage capacity of 26,300 acre feet. Sin2e the emergency spillway \vas <br /> <br />perched to reduce construction cost, the actual amo~nt of storage capacity <br /> <br /> <br />. provided at this project is substantially in excess of that required to <br /> <br /> <br />control the standard project flood. A check was made in the reevaluation to <br /> <br />determine llOW this project 'Would perform during a SOD-year mountain snowmelt <br /> <br />inflow. The results indicated that this condition produced a storage require- <br /> <br />ment of 38,000 acre feet which is more critical than that required for the <br /> <br />standard project rainfall flood. <br /> <br />4. [Jpdat.cd Stnrgl"e C:3p8citips. Updated capacity 2urves h'lv'O b2en pUblished <br /> <br />since the 3torag.;? re'~valu::ltion studies were made. The ne\-1 curve fer Chatfield <br /> <br />Reservoir was published in October 1982, \'Ihile the new cur'!e for Bear Creek <br /> <br /> <br />ResC'rvoir .vas publish,~d .in ;~arch 19[13. Bot.h~f th"!s8 cur'!es are more refin"d <br /> <br /> <br />than the pr'2vious curves clOd sho'" enough chan,~e to justify 21 teration of <br /> <br />storage allocations. rlese ere sho'~ on plate 2. <br /> <br />. <br /> <br />2 <br />