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However, pit inflow waters will be discharged to the surface stream, and the overall impact to the <br />quantity of surface water during mining will be minimal. Following mining, ground water levels will <br />return topre-mining levels. This will result in the reestablishment ofspring and seep flows consistent <br />with pre-mine rates. <br />The mining and processing of coal at the Carbon Junction Mine will impact the quality of both surface <br />and ground waters during and after mining. Mining will disrupt the natural soils and rock strata in <br />the disturbed areas of the mine operation. Disruption of soils and rock strata will increase the <br />exposure of previously unexposed materials to both surface and ground waters. This exposure will <br />result in increased leaching and weathering of these materials, with a corresponding increase in <br />suspended solid and dissolved solid loads in surface waters and increased dissolved solid loads in <br />ground waters. <br />Suspended sediment levels will be minimized during mining by routing disturbed drainages through <br />sediment ponds. Sediment ponds will remain in place until reclamation of the spoils and fill have been <br />completed. <br />Total dissolved solid (TDS) levels in surface waters will increase during mining through the leaching <br />of exposed materials, concentration of TDS due to evaporation in sediment ponds and mine pit, and <br />through the operation of the coal processing plants. The surface water discharges must meet the <br />effluent limitation imposed by NPDES permits prior to discharge. Therefore, the impacts to surface <br />water quality will be minimized during the mining operation. After the site has been reclaimed, water <br />qualities will return to pre-mining conditions over time. <br />During and after mining, the exposed disturbed soils and rock strata will impact the quality of ground <br />water in aquifers within the permit and hydrologically adjacent areas. Pi[ waters and deep percolation <br />through spoils and the fill will impact ground water qualities during mining. The degree of impact <br />to ground water quality depends on: 1) the residency time of water exposed to disturbed soils and <br />rock strata and 2) the residency time of spoils waters and pit waters within the recharge area of the <br />aquifers. <br />The coarse fill and spoils materials will allow rapid infiltration and deep percolation of surface waters. <br />Water which infiltrates the spoils will flow down the dip of the spoils-bedrock contact to the low end <br />of the pit during mining, be discharged to sediment pond 1 and then to the stream. The flow rate of <br />infiltrating waters to the pit will be rapid and exposure time will be minimal. Thus, water quality <br />degradation will be minimal. <br />The residency time of spoils and pit water over aquifer recharge areas will be minimal during the <br />mining operation, since water collecting in the pit and water stored in sediment ponds will be <br />discharged to the surface stream. <br />After the pit and fill slopes have been backfilled and reclaimed, a spoils water aquifer will be <br />established within the recharge area of the bedrock aquifers. Infiltration will be minimized due to the <br />construction of a compacted impermeable layer of clay and silt beneath the reconstructed stream <br />9 <br />