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available storage volume is filled. Very little of the impounded water will re- <br /> enter the ground water system due to the clay subsoils which comprise the pond <br /> bottoms. Losses from the D-Portal pond will be insignificant when compared <br /> to total runoff from the Scullion Gulch watershed. The pond is designed to <br /> store runoff from 44 acres, while Scullion Gulch has a contributing drainage <br /> area of 7,552 acres at its confluence with the White River. The refuse disposal <br /> area ponds receive runoff from approximately 98 acres, which is a very small <br /> portion of the 2,950 acres drained by the Red Wash tributary through the <br /> northern sector of the permit area. Based on this information, the net loss of <br /> surface water quantity to Red Wash and the White River will be negligible. <br /> Water supply for the mine will come from the White River Lagoon. Combined <br /> water use and evaporative loss at full production is projected to consume 552 <br /> acre-feet per year at a withdrawal rate of .763 cubic feet per second. This <br /> translates to less than 0.2 percent of the average annual flow in the river of 672 <br /> cfs. Even during low flow conditions, when the average flow is 245 cfs, the <br /> withdrawal rate will only be 0.31 percent of the available flow. Therefore, <br /> adverse impacts on flow in the White River as a result of proposed withdrawal <br /> should be minimal. Furthermore, the permittee has secured water rights <br /> downstream of the mine that may be used if necessary to replace a depleted <br /> water source. <br /> Construction of surface facilities in the permit area will cause temporary <br /> increases in the amount of suspended solids in the surface water system. <br /> Furthermore, concentration of chemicals associated with increased sediment <br /> load, such as iron and manganese, will also increase. At the Deserado Mine, <br /> mitigation of sediment load will be accomplished primarily by sedimentation <br /> ponds. Although sediment increases will occur in the early phases of <br /> construction, the long-term sediment yield may actually decrease below the <br /> already high natural occurrence of sediment concentrations due to the <br /> installation of control measures. <br /> Effects on the surface water system from the refuse disposal area should be <br /> minimal. Analysis of the waste material does not indicate that toxic or acid- <br /> forming characteristics are present, so the disposal areas will not be lined to <br /> prevent percolation into the ground water system unless further monitoring <br /> results indicate that this is necessary. The waste will be covered with 30 inches <br /> of non-toxic, non-combustible material (48 inches on RP-1), thereby reducing <br /> infiltration of water into the pile and further reducing the potential for water <br /> quality degradation. The size of the non-reclaimed disturbed area at the refuse <br /> disposal area will be a maximum of approximately 120 acres at any one time. <br /> All runoff from the disturbed area will be routed to properly sized sediment <br /> ponds; therefore, any impacts of the disturbance on surface water quality will <br /> be minimal. Darwin Reservoir, a large stock pond situated along the Red Wash <br /> tributary, is approximately 800 feet from refuse subarea R-9, which will be <br /> developed in future permit terms. Due to the distance of the stock pond from <br /> 23 <br />