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retention of water in ponds and removal of water from the White River Lagoon. <br />Runoff from disturbed areas will be routed through sedimentation ponds, thereby <br />reducing the amount of flow to the White River. Evaporation losses will occur <br />because the ponds will not discharge runoff until some of the available storage <br />volume is filled. Very little of the impounded water will re -enter the ground <br />water system due to the clay subsoils which comprise the pond bottoms. Losses <br />from the D -Portal pond will be insignificant when compared to total runoff from <br />the Scullion Gulch watershed. The pond is designed to store runoff from 44 <br />acres, while Scullion Gulch has a contributing drainage area of 7,552 acres at its <br />confluence with the White River. The refuse disposal area ponds receive runoff <br />from approximately 98 acres, which is a very small portion of the 2,950 acres <br />drained by the Red Wash tributary through the northern sector of the permit area. <br />Based on this information, the net loss of surface water quantity to Red Wash and <br />the White River will be negligible. <br />Water supply for the mine is supplied by the White River. Combined water use <br />and evaporative loss at full production is projected to consume 552 acre -feet per <br />year at a withdrawal rate of .763 cubic feet per second. This translates to less <br />than 0.2 percent of the average annual flow in the river of 672 cfs. Even during <br />low flow conditions, when the average flow is 245 cfs, the withdrawal rate will <br />only be 0.31 percent of the available flow. Therefore, adverse impacts on flow in <br />the White River as a result of proposed withdrawal should be minimal. <br />The 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 installation <br />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 the presence of toxic <br />or acid - forming characteristics. The waste will be covered with 30 inches of non- <br />toxic, non - combustible material, thereby reducing the potential for water quality <br />degradation. The size of the non - reclaimed disturbed area at the refuse disposal <br />area will be a maximum of approximately 120 acres at any one time. All runoff <br />from the disturbed area will be routed to properly sized sediment ponds. <br />Subsidence from underground mine workings could potentially impact both Red <br />Wash and Scullion Gulch. The effect on Red Wash is of greatest importance <br />because it drains approximately 122 square miles at the location where mining <br />will exist beneath it. Although predictions indicate that maximum vertical <br />subsidence could approach six feet, large crevasses or collapse of the surface <br />29 <br />