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Based on the latest inspections by the State Engineer, we believe South Gray may be restricted in the <br />near future due to the severity of the seepage. It is our opinion the restriction will be in the range of <br />2'h feet to 3 feet which relates to a loss of storage capacity of 165 acre-feet to 200 acre-feet. The <br />restriction would normally be to an elevation at which the seepage is significantly reduced and the <br />dam is considered safe. That elevation has not been determined by the State Engineer but based on <br />our inspection of the dams and our past experience, we believe the restriction would be in the range <br />indicated. <br />Photographs of the dam embankments are included in Appendix H of this report. The fill charts <br />indicating the reservoir storage are shown in Appendix D. <br />ALTERNATIVES EVALUATED <br />During our study of South Gray and GrayNo. 3 we evaluated the following alternatives: l) breaching <br />Gray No. 3 and adding toe drains and an access road to the outlet works on South Gray, and 2) <br />breaching Gray No. 3 and adding toe drains and an access road on South Gray through with the <br />installation of a ramp from the dam crest to dam toe, and 3) full rehabilitation of Gray No. 3 and the <br />and adding toe drains and an access road on South Gray with a access ramp to the outlet works, and <br />4) no action alternative for both reservoirs. <br />Following is a summary of our assessment of each alternative. <br />Alternative #1 <br />Gray No. 3 <br />If Gray No. 3 is to be taken out of service the State Engineer will require the dam be breached in <br />accordance with Rule 7. This rule 7.A.(2)(a) requires the breach be sized to pass a 100-yeaz flood. <br />Due to this the work required on Gray No. 3 will include the following: <br />1. Provide a breach of adequate size to pass the 100-year flood. <br />2. Dam breach proposed is at a 3:1 slope with a breach bottom width of 65 feet. <br />3. The dam access road will be re-routed to the downstream toe of Gray No. 3 and South Gray due <br />to the breach cutting off the current access. <br />4. Excess excavated material from the breach will have to be spoiled in the reservoir area and the <br />disturbed areas seeded to prevent erosion. <br />5. The existing outlet works will have to be demolished and buried in the reservoir. <br />6. The area downstream of the breach will have to be graded to provide a spillway through the <br />breach to Box Elder Creek. <br />7. Riprap and bedding will be placed at the confluence with Box Elder Creek to limit erosion. <br />The details for this altemative are shown on Drawings 1 and 2 included herein. <br />Gray Reservoirs-Feasibility Study Page 5 <br />