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Feasibility of Construction <br />of <br />Chimney and Toe Drains <br />at the Cedar Mesa Dam <br />1.0 Introduction (Need for the Project) <br />The Cedar Mesa Ditch and Reservoir Company (CMDRC) is applying for a$1OQ000 Small <br />Project Loan to rehabilitate the Cedaz Mesa Dam on Grand Mesa. The estimated cost of the <br />project is $131,962. <br />The CMDRC operates the Cedaz Mesa Reservoir located in Delta County approximately <br />12 miles north of the city of Cedaredge, Colorado, as a source of irrigation flow for its <br />shazeholders and other downstream users. The CMDRC has 24 shareholders who collectively <br />have the right to draw flows generated by the release of waters from the Cedar Mesa Reservoir. <br />Operation of the reservoir typically consists of collection of spring runoff to the maximum <br />decree volume of 903 acre-feet and disbursement of the water reserve over the course of the <br />imgation season on an as-needed basis. <br />The reservoir is situated behind the Cedar Mesa Dam, which is a 47-foot-high, 1,200-foot- long <br />homogeneous earthfill structure. The outlet works consists of an upstream knife gate valve and <br />outlet piping. The outlet works valve is operated from the crest of the dam using a manual <br />actuation stem. In addition to the outlet works, the dam has a spillway on its left abutment, <br />which has the capacity to pass 8,550 cfs. The spillway has a concrete crestwall at a gauge height <br />of 37.0 and a 130-foot bottom width. The dam was constructed in 1894 and has been repaired a <br />number of times through the yeazs. <br />The Cedar Mesa Dam was placed under restriction by the State of Colorado Dam Safety <br />Engineer following inspections that identified a number of issues that point to potential <br />instability of the structure. The issues that were identified by the Dam Safety Engineer include <br />seepage observed at the downstream toe and on the right abutment and wetting observed on the <br />downstream face. The restriction will remain in effect until adequate investigation and remedial <br />work can be performed to mitigate and/or address potential dam safety issues identified by the <br />State. Copies of the State Engineer's inspection reports and restriction letter aze included in <br />Appendix A. <br />This feasibility study is aimed at identifying remedial altematives and addressing issues raised <br />by the State Dam Safety Engineer. Information used for this feasibility study includes a <br />geotechnical study performed by Smith Engineering of Ft. Collins, Colorado, in 2000, a Phase I <br />dam safety report performed by Hydro-Triad, Ltd. in 1980, and subsequent investigations <br />performed by Knight Piesold and Co. of Denver, Colorado, which are currently nearing <br />completion. <br />f_.:�µpwoM\18005\1835A\CeCarMesaFwsiDili�yReport.0oc 1 Ju1y2001 <br />