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