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18. SUMMARY The hydrological interrelationship between the Castlewood and Cherry Creek Reservoirs and the Cherry Creek channel dic- tate that they be considered an integral unit. The Castlewood Reservoir has been formulated with a perched spillway to control the standard project flood volume plus 53 percent of the prob- able maximum flood volume. With this amount of supplemental storage, the deficiencies of the Cherry Creek Reservoir can be corrected by raising the spillway crest 31 feet. The Cherry Creek floodway and channel improvement are provided essentially to assure continued operational capability of the Castlewood and Cherry Creek Reservoirs. The channel has been enlarged, where necessary, to provide additional capacity for carrying floodflows originating downstream from the Cherry Creek Dam. 19. SELECTED PLAN a. General. The selected plan of improvement consists of the construction of the authorized Castlewood Dam and Reservoir, acquisition of a floodway between the Castlewood Dam and the Cherry Creek Reservoir, modification of the Cherry Creek Dam and Reservoir, and improvement of the Cherry Creek channel down- stream from the Cherry Creek Dam. b. Castlewood Dam and Reservoir. The Castlewood Reservoir would provide storage for the standard project flood. An emer- gency spillway, which would be located in the left abutment, would be perched 50 feet above the standard project flood pool level to provide'storage for 53 percent of the probable maximum flood. The reservoir would also provide storage for the accumulation of 100 years of sediment runoff. A gated-outlet works with a low-level inlet would be provided to regulate reservoir releases. The outlet works would consist of a concrete intake structure, a concrete conduit, and a stilling basin at the downstream end of the conduit. Pertinent data for the Castlewood Dam and Reservoir are shown in table 1. 34 '3032