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MLRB M 84-041 <br />waste <br />rock <br />tOp <br />waste <br />rock <br />slope <br />19 APRIL 1990 <br /> <br />PAGE 2 <br />1 3.0 300 10.0 20 .17 2.4 .45 1 3.67 11.0 <br />2 4.0 50 25.0 20 .17 4.5 .45 1 6.90 27.0 <br />38.0 691 <br />mine 1 20.0 1000 2.0 20 .17 .4 .45 1 .60 12.0 218 <br />The following table summarizes the results of the TR-20 <br />determinations and the Universal Soil loss Equation: <br />AREA PEAK DISCHARGE RUNOFF VOLUME SEDIMENT VOLUME <br /> cfs cubic feet cubic feet (annual) <br />Mine 111.63 281,597 415 <br />Waste 46.42 114,757 691 <br />Process 69.01 167,700 218 <br />The sedimentation-check basins will be provided with a marker to <br />indicate when one-half of the anticipated sediment has <br />accumulated, at which point the basin will be cleaned, with the <br />material removed to the waste rock storage area. The volume of <br />sediment removed will be reported in the annual report. <br />b. Riprap comprised ~ onsite cobbles and boulders will be <br />placed at the junction of the rock cut spillway channel and the <br />natural gulch channel. As illustrated on the typical basin <br />drawing, it is intended to construct the spillways 10 feet wide <br />with 1.5 to 1.0 side slopes for a full cross-section area of 11.5 <br />feet. This section on a 10~ slope through the spillway with an n <br />factor of 0.025 will carry a flow of 193 cubic feet per second, <br />which is greater than any of the design flows noted in the table <br />above. The actual hydraulic characteristics of the as-built <br />structures will be reported with the as-built drawings. <br />c. As-built drawings of each of the sedimentation-check basin <br />structures will be provided to the MLRB within 60 days of the <br />completion of the construction of the structures. <br />d. The basins will not have a storage capacity greater than 2 <br />acre feet, and therefore will not need an application for a stock <br />tank from the State Engineer's Office. <br />JEROME GAMBA & ASSOCIATES, INC. <br />CONSUUING ENGINEERS & LAND SURVEYORS <br />