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-zo- <br />Total dissolved solid (TDS) levels in surface waters will increase during <br />mining through the leaching of exposed materials, concentration of TDS due to <br />evaporation in sediment ponds and mine pit, and through the operation of the <br />coal processing plants. The surface water discharges must meet the effluent <br />limitation imposed by NPDES permits prior to discharge. Therefore, the <br />impacts to surface water quality will be minimized during the mining <br />operation. After the site has been reclaimed, water qualities will return to <br />pre-mining conditions over time. <br />During and after mining, the exposed disturbed soils and rock strata will <br />impact the quality of ground water in aquifers within the permit and <br />hydrologically adjacent areas. Pit waters and deep percolation through spoils <br />and the fill will impact ground water qualities during mining. The degree of <br />impact to ground water quality depends on: 1) the residency time of water <br />exposed to disturbed soils and rock strata and 2) the residency time of spoils <br />waters and pit waters within the recharge area of the aquifers. <br />The coarse fill and spoils materials will allow rapid infiltration and deep <br />percolation of surface waters. Water which infiltrates the spoils will flow <br />down the dip of the spoils-bedrock contact to the low end of the pit during <br />mining, be discharged to sediment pond 1 and then to the stream. The flow <br />rate of infiltrating waters to the pit will be rapid and exposure time will be <br />minimal. Thus, water quality degradation will be minimal. <br />The residency time of spoils and pit water over aquifer recharge areas will be <br />minimal during the mining operation, since water collecting in the pit and <br />water stored in sediment ponds will be discharged to the surface stream. <br />After the pit and fill slopes have been backfilled and reclaimed, a spoils <br />water aquifer will be established within the recharge area of the bedrock <br />aquifers. Infiltration will be minimized due to the construction of a <br />compacted impermeable layer of clay and silt beneath the reconstructed stream <br />channel. The extent of degraded spoil water incursion into the aquifers will <br />be minimal. Dilution and dispersion by ground water within the aquifers will <br />fu~~ther diminish the water quality impacts. <br />Wastes from the coal wash plant/breaker facility could potentially impact the <br />quality of surface and ground water. The sulfur content of the coals and <br />their associated over and underlying strata range between 1 and 3 percent. <br />These levels are higher than any recorded levels for active coal mines in the <br />State of Colorado. Also, abandoned coal mine records for the Durango, <br />Colorado area document problems with acid mine waters and barren and burned <br />spoil piles. Both of these facts indicate that the coal processing wastes <br />generated by the Carbon Junction Mine will be acid-forming and have a high <br />probability of being combustible and toxic-forming. <br />