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<br />. <br /> <br />. <br /> <br />waters cut a ten foot wide path over the dam at side slopes of approximately <br />1 to 1. The flood waters cease but the water impounded behind the Buckeye <br />Reservoir Dam is continuing to flow in the eroded cut ilnd eros.Loll continues until <br />all of the stored water has entered Buckeye Creek. <br /> <br />Let us assume that the failure of the Buckeye Reservoir Dam takes six hours from <br />the time the dam was first overtopped until the Reservoir is emptied. Considering <br />1,600 acre feet in the reservoir at the time of overtopping (69,696,000 cubic feet), <br />an average of 3,227 cubic feet per second would be entering Buckeye Creek, which pro- <br />bably would cause damage in the Manti-La Salle National Forest and farm grounds in <br />the Paradox Valley. Consider also, a ten foot wide eroded cut at the bottom sloping <br />back at a 1 to 1 slope through the dam, 7,700 cubic yards of materii'll would be <br />eroded from the dam. <br /> <br />Using the estimated unit cost of $6.30 per cubic yard of compacted material and <br />keeping all other unit prices and quantities the same as shown in Estimated Pro- <br />ject Costs on Page VI-2, the cost of repairing the Buckeye Reservoir would be <br />$137,500.00. It would not be wise to replace only the materIal that had been <br />eroded as plans should be made to excavate into the earthern material perpendicu- <br />1 ar to the axis to the dam at a 5 to I slope. This procedure would reduce the <br />problems of compacting the closure section against steeper slopes which can creA.te <br />planes of higher permability. The existing slope would need to be s"arified and <br />properly moistened, prior to placing the closure layers to achieve a good bond of <br />the closure to the existing embankment sections. To excavate back the slopes to <br />achieve a good bonding surface would require the removal of 4,614 ctiliic yards, <br />to replace the eroded and excavated section with a 3 to I upstream slope, 15 foot <br />wide crest, and 2 to 1 downstream slope, would require 6,256 cubic yards. The <br />reason there would be less cubic yards of compacted embankment replaced in the <br />eroded and excavated section of the dam is that the dam would not necessarIly have <br />to be replaced to the existing configuration since the existing dam is 225 feet <br />wide at the top and approximately 445 feet wide at the bottom. <br /> <br />Using the same unit prices and relative unit prices as used in the Estimated Project <br />Costs on Page VI-2 and based on the assumptions previously supposed the following <br />is the estimated costs of the repair of the Buckeye Reservoir Dam due to overtopping <br />by a flood without benefit of an adequate spillway. <br /> <br />VIII-4 <br />