C153607L Feasibility Study - Laserfiche WebLink

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II I I I I I I i I I I I ; I I I I I I I I I I The only additional work considered was to replace the masonry nume at the end of the outlet conduit and to provide an energy dissipation structure. The cost of this alternative Is as follows. MISCELLANEOUS AL TERNA TIVES Description Estimated Cost Replace existing masonry flume with a concrete nume and a concrete energy dissipation structure. $39,500.00 SMITH GEOTECHNICAL recommends Alternative No. IA above and recommends replacing the masonry flume for a total construction cost of $721,350. The total project cost Including 30 percent for engineering, legal fees, and contingencies would be $937,755. Alternative No. lA was chosen based on the engineering merits, the geology, and cost. Alternative No. 2 Is believed to be the best alternative based solely on the engineering merits; whereas, alternative No. 3 Is the least viable alternative based on the potential geologic problems associated with this alternative. Alternative No. lA was chosen over Alternative No. 1 based on the slide block toe being located near where Alternative No. I nows Into Trlnchera Creek. The potential for Induced sliding of the old landslide mass Is less with Alternative IA than with 1. There Is some potential danger with placing the spillway In the location outlined for Alternative No. IA due to the past sliding In the area. However, due to the relatively short duration of the spills through the channel and the relatively steep spillway slope, we expect the Inflltratlon of water Into the subsurface solis to be minimal and the sliding potential to be acceptable at this location. This alternative Is feasible but we recommend a thorough and detailed landslide analysis be conducted of the area prior to final design. Alternative No. 3 could not be recommended at this time due to the potential for subsurface saturation of the old slide zone In the spillway area. The existing sag pond In the area would hold water for weeks after a spill and the potential for sliding would be too great. It Is possible that this alternative could still be viable but would require a thorough and detailed landslide analysis of the area. Alternative No. 2 and 2A would both be feasible from an engineering point of view and would Increase the overall stablllty of the dam. The only drawback to these alternatives Is the cost which Is much greater than Alternative No. 1 or No.3. The Trlnchera Irrigation Company has applied for a $1,000,000 loan from the Colorado Water Conservation Board which will be repaid over a 40 year period at a one (l) percent Interest rate. For a loan of $1,000,000 the annual payment would be approximately $30,435 and would raise the assessments by approximate- ly $2.65 per share of stock. Ill.