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SELECTED ALTERNATIVE <br />A) DESCRIPTION <br />The selected alternative is to structurally lower the existing emergency spillway, <br />permanently limiting the reservoir storage capacity, to a level that will safely pass the SEO <br />required inflow design flood. <br />B) DESIGN CRITERIA <br />1. A detailed hydrologic model will be developed for the reservoir drainage basin and the <br />required inflow design flood will be routed through the reservoir and emergency <br />spillway. Iterative model runs will be performed to determine at what elevation the <br />lowered spillway can safely pass the inflow design flood with adequate freeboard. <br />2. After determination of this lowered spillway elevation, a detailed Failure Modes and <br />Consequences Analysis (FMCA) will be performed to determine if there are structural <br />concerns relating to the proposed reservoir storage level. If problems are identified, <br />possible remedies and mitigation measures will also be identified. Design solutions <br />would be submitted to the SEO for review and approval as required. <br />3. Based on the results of the two prior tasks, detailed designs, plans and specifications <br />would be developed for lowering the existing spillway. <br />4. A detailed dam break model and dam break inundation map would be developed to <br />verify the dam hazard class based on the reduced reservoir storage level and for use in <br />the updated Emergency Action Plan (EAP). <br />5. Leakage and operational reliability of the two existing and operable 30-inch diameter <br />outlet valves has been an ongoing problem. These valves and operators would be <br />inspected and evaluated and in all likelihood, replaced with new valves and operators. <br />6. A detailed and thorough instrumentation and monitoring program would be developed <br />and implemented which would transmit data at~regular intervals via the SEO satellite <br />monitoring system. It is envisioned that this program would allow for daily monitoring <br />and evaluation of the performance of the dam. Should problems begin to develop at the <br />dam, early detection of the problems will be possible with the envisioned system. <br />7. An updated Emergency Action Plan will be developed around the newly configured <br />dam and reservoir for prudent use during the development of any possible emergent <br />condition. <br />C) RIGHT-OF-WAY <br />No additional land or right-of-way will be required for the selected alternative. <br />D) COST ESTIMATE <br />Please refer to Appendix A for the detailed cost estimate. <br />E) ECONOMIC ANALYSIS <br />If completion of the selected alternative allows the current restricted storage level to be <br />maintained, this results in savings of approximately 7,400 AF of storage in lieu of an SEO <br />Cucharas Feasibility Study ~ Selected Alternative <br />