C153804 Feasibility Study - Laserfiche WebLink

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I I I I I I I I I I I I I I I I I I I According to the rules and regulations of the Office of the State Engineer, Class I - Intermediate dams must be able to pass the runofffrom a design storm of 75 percent of the Probable Maximum Precipitation without overtopping. Hydrologic analysis (Rocky Mountain Consultants, Inc. 1993, included as Appendix D) concluded that without improvements the design flood would overtop the existing dams byapproximately 2.92 feet. The purpose of this study is to determine the most feasible manner in which to provide sufficient increased spillway capacity to safely pass the design flood. Figure ID-2 shows the area in the vicinity of the north dam of the reservoir, including the dam, the existing spillway, the outlet works, and the extent of the Company's property. B. Water Demands The purpose of this project is strictly limited in scope to providing additional spillway capacity at Left Hand Valley Reservoir. No additional water supplies will be developed in connection with this project. No new or increased diversions will be made from Left Hand Creek and no additional storage capacity is to be created at the reservoir. C. Project Lands The uses of water from Left Hand Valley Reservoir are not changing as a result of this project. This project will not broaden the Company service area and will not provide for the irrigation of any new lands. D. Hydrology and Water Rights The water rights of the Company are briefly described in Chapter II. This project will not provide any additional water rights or water supplies for the Company. The hydrology of importance to this project is the determination of inflow and routed outflow from 75 percent of the PMP as described in detail in Appendix D. The peak inflow to the reservoir from the design storm is 17,938 cfs. 10