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CWCB Loan Narrative Overview 11 <br />of the EPAT process. Since the basin is larger than the 500 square mile cutoff, EPAT would have to be applied for sub-basins and routed appropriately. The GEI report has estimated that a significant increase in the PMF is justified. This large increase and the results of the IDA may allow for first phase spillway improvements to accommodate a smaller IDF. This would be based on the fact that a dam failure at the 10,000 AF of storage level would not impact the downstream reach any more than the 100% PMF. The hydrology report that has been prepared by GEI has not been peer reviewed or accepted by the State Engineer. Part of the future work in design studies would have to address this issue. Based on the new permitted reductions in PMP values, we believe it is feasible to permanently lower the existing spillway to an elevation that could safely route the required inflow design flood. There is sufficient elevation difference between the existing concrete ogee crest spillway, the reservoir basin and the rock cut spillway discharge channel to lower the emergency spillway 25 vertical feet. This elevation roughly corresponds to the current restricted storage level of gauge height 100 feet. Lowering the spillway to this level would produce 57,000 acre-feet of flood routing storage and significantly increase the spillway capacity. The goal would be to only lower the spillway to an elevation that could safely pass the required inflow design flood and maintain as much reservoir storage as possible. A detailed basin and reservoir hydrologic model would be developed in conjunction with appropriate hydrology tools to determine the required spillway control elevation. While there are significant structural issues with the present dam embankment that make permanent reservoir storage at higher elevations not feasible, the dam has performed adequately for the past twenty years at the current restricted level of gauge height 100 feet. No additional embankment consolidation or displacement has been measured and only minor increases in seepage have been noted at the maximum restricted storage level. Lowering the spillway and restricting the maximum storage level in the Phase I will provide adequate protection of public safety while the evaluation of the Phase II work is finalized. A secondary benefit could be the reduction of the hazard classification from high to significant hazard. A Failure Modes and Consequences Analysis study is planned to evaluate the structural issues and the need for a stability/seepage control berm along the downstream toe of the dam will be considered, particularly if storage levels are increased above the current restricted level. Given the two phased approach of dam improvements, the goal would be to minimize Phase I work to meet public safety standards with the major expenditures being made in Phase II. For example, although the outlet works gates are currently in need of repair, they do function safely. Rather than spend money on replacing the gates in the Phase I, it would seem prudent to defer this cost until Phase II when the new dam is rebuilt.