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mine plan area to White River, increased sediment loads from disturbed areas, <br />and water quality degradation from the Refuse Disposal area. Long term impacts <br />will center on the effects of subsidence under Scullion Gulch and Red Wash. <br />See the Subsidence section of this TEA for further discussion of subsidence <br />impacts. <br />Short term surface water loss will occur as a result of two things: retention <br />of water in ponds and removal of water fran the White River alluvium by the <br />well field. Runoff from disturbed areas will be routed through sedimentation <br />ponds, thereby reducing the amount of flow to the White River. Evaporation <br />losses will occur because the ponds will not discharge run-off until some of <br />the available storage volume is filled. The impounded water may, however, <br />percolate through the reservoir to re-enter the ground water and surface water <br />systems. Losses from the D-portal pond will be insignificant when compared to <br />total run-off from the Scullion Gulch watershed. The pond is designed to store <br />run-off from 44 acres while Scullion Gulch has a contributing drainage area of <br />7,552 acres at its confluence with the White River. The Refuse Disposal area <br />ponds receive run-off 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 White River will be negligible. <br />The water supply for the mine will come from the White River at a withdrawal <br />rate of 1.34 cubic feet per second. This translates to 0.2 percent of the <br />average annual flow in the river of 672 cfs. Even during low flow conditions, <br />when the average flow is 245 cfs, the withdrawal rate will only be 0.55 percent <br />of the available flow. Therefore, adverse impacts on flow in the White River <br />as a result of proposed withdrawal should be minimal. Furthermore, the <br />applicant has secured water rights downstream of the mine that may be used if <br />necessary to replace a depleted water source. <br />Construction of surface facilities in the permit area will cause temporary in- <br />creases in the amount of suspended solids in the surface water system. Fur- <br />thermore, concentrations of chemicals associated with increased sediment load, <br />such as iron and manganese, will also increase. At the Deserado Mine, mitiga- <br />tion of sediment load will be accomplished primarily by sedimentation ponds. <br />Although sediment increases will occur in the early phases of construction, the <br />long-term sediment yield may actually decrease below the already high natural <br />32 <br />