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. . I .(/ 71/..(1,/ I? ( Fact Sheet Chatfield & Bear Creek Water Supply 1. The reevaluation study of Tri Lakes Reservoirs started in July of 1982 in conjunction with the Denver Water Board SEIS. The specific request asked for an investigation of the Reservoir Design Flood and the adequacy of the Probable Maximum Flood at each project. 2. The results of the Reservoir Design Flood reevaluation were discussed and presented in comment 2 dated 29 Sep 82 (see inclosure 1) to the Chief of Planning Division. A discussion of the adequacy of the Probable Maximum Flood for each reservoir was overlooked in that DF. .-~ However, special report entitled Hydromet 844 (HM #44) was prepared for Chatfield to dete~ine the appropriate probable maximum precipitation at this location prior to the design and its adequacy should be acceptable to even the most critical review. The criteria in IIMt44 was also applied to the basins above Bear Creek and Cherry Creek to obtain the P1IT inflow. 3. Effect of Using Updated Information. Since the reevaluation was based on the original design configuration, the available storage figures shown in inclosure 1 do not reflect the changes in reservoir capacities or changes that have taken place in conservation storage allocations since the projects were designed: Chatfield Design Capacity Top of Flood Pool (Elevation 5500) 235,000 Ac.Ft 20,000 Ac. Ft 100-year Sediment Conservation Storage (El. 5426) Available for Flood Storage 215,000 Ac Ft Flood storage required under reevaluation is 182,000 Ac ft - which leaves 33,000 Ac Ft vacant for water supply. Chatfield Capacity update '(Oct1982) Top of Flood Pool (Elev. ,5500) 231,400 Ac Ft Conservation Storage - Foot Hills Agreement (E1 5432) 26,700 Ac Ft 204,'700 Ac Ft Available for Flood Storage 204,700 - 182,000 leaves 22,700 Ac Ft vacant for water supply.