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The Huerfano-Cucharas Irrigation Company May 12, 2009 (UPDATED May 22, 2009) Page 4 of 7 Agenda Item 17h Alternative No. 2- Sediment remova[ in conjunction with dam repair: In the 2006 feasibility report by URS, it was estimated that over eight million cubic yards of deposited sediment exist in the Reservoir basin. This equates to roughly 500 AF of lost storage. The determination was made that the costs, environmental concerns and required permitting made removal of the sediment unfeasible. Alternative No. 3- Construct a new RCC dam downstream of the existing dam: This was the recommended alternative of the 2006 URS feasibility report and remains a long-term goal of the Company. The estimated $30 million price tag of this alternative is beyond the current financial capability of the Company. A[ternative No. 3- Rehabilitate the existing dam to allow full reservoir storage: Preliminary cost estimates associated with rehabilitating the existing dam to restore full Reservoir storage indicate that this alternative would have a greater cost than construction of a new RCC dam downstream of the existing dam. For this reason, no further evaluation of this alternative was considered. SELECTED ALTERNATIVE No. 4- Lower the emergency spillway to allow storage at a reduced storage level: The selected alternative is to structurally lower the existing emergency spillway, permanently limiting the reservoir storage capacity to a level that will safely pass the SEO required inflow design flood. Since the initial feasibility study, the SEO has promulgated new Rules and Regulations for Dam Safety and Dam Construction that allow reductions in Probable Maximum Precipitation (PMP) values for altitude and the use of a site specific weather model developed by the SEO for high altitude precipitation. Based on the new permitted reductions in PMP values, 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 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. 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. This alternative is expected to maintain approximately 7,500 AF of storage. 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. No additional embankment consolidation or displacement has been measured and only minor increases in seepage have been noted at the maximum restricted storage level. Permanently lowering the spillway and restricting the maximum storage level could have an additional benefit by reducing the hazard classification from high to significant hazard.