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• -32- <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. Sediment contribution from underground mine <br /> dewatering should have little impact on the surface water quality as this <br /> water will be stored in a holding tank and treated for use in surface <br /> facilities (where it will be monitored) or re-used in the mine. <br /> Probable Cumulative Hydrologic Impacts <br /> Probable cumulative hydrologic impacts at the Deserado Mine will occur in <br /> response to continued operations at the site. Currently there are no other <br /> operating or proposed mines in the area which could add to the hydrologic <br /> impacts at Deserado. <br /> The proposed life of mine operations at Deserado include the construction of <br /> the B-Portal area in Scullion Gulch and continued extraction of D-Seam coal <br /> via the existing D-Portal facility. These are expected to result in a slight <br /> increase in the impact resulting from the operations during the life of the <br /> mine. These impacts are discussed below as they are presented in the surface <br /> and ground water sections of this findings document. <br /> Impacts of the Mining Operation on Surface Water <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 <br /> acid-forming characteristics are present, so the disposal areas will not be <br /> lined to prevent percolation into the ground water system unless further <br /> monitoring results indicate that this is necessary. The waste will be covered <br /> with four feet of non-toxic, non-combustible material , thereby reducing <br /> infiltration of water into the pile and the potential for contamination of <br /> surface waters. All run-off from the disposal areas will be routed through <br /> sedimentation ponds and monitored for degradation of quality before being <br /> released into the Red Wash tributary, and treated if necessary. The size of <br /> the disturbed area at the refuse disposal area will be a maximum of <br /> approximately 50 acres at any one time. All runoff from the disturbed area <br /> will be routed to properly sized sediment ponds, therefore any impacts of the <br /> disturbance-oa surface water quality will be minimal . Darwin Reservoir, a <br /> large stock pond situated along the Red Wash tributary, is approximately <br /> 800 feet from refuse subarea No. R-9 which will be developed in future permit <br /> terms. Due to the distance of the stock pond from the area of disturbance, no <br /> surface water impacts are anticipated. <br /> Impact of the Mining Operation on Ground Water <br /> The impact of the proposed mine on ground water will be very localized, with <br /> no significant impact expected on a regional basis. This is due primarily to <br /> the small quantity of ground water in the area. <br /> Water encountered within the mine will be utilized underground for dust <br /> • suppression. As a result, only those inflows which temporarily exceed storage <br /> capacities and mine use requirements should be discharged to the surface and <br /> lost from the ground water system. However, since this water would normally <br /> have been destined for the White River, its discharge to the surface will not <br /> remove it from the hydrologic system. <br />