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between 0 and 60 feet and has a hydraulic conductivity of <br /> 0.01 cm2. The main concern with the alluvial aquifer is the <br /> total dissolved salt (TDS) content that mining contributes to the <br /> stream flow. The diminished quality of water discharged from the <br /> mine due to salt and sediment loading is improved somewhat by <br /> allowing the water to settle out the solids . The discharged mine <br /> water is given sufficient time to allow gravity to settle the <br /> solids before discharge occurs to the Colorado River . No <br /> flocculents are used in the mine . Three NPDES points discharge the <br /> mine water (Nos . 001 , 002 and 004) and are subject to Colorado <br /> Department of Health water quality standards . Potential impacts on <br /> alluvial water quality due to mine water discharges were discussed <br /> previously in Section II . A. and K. of this document. <br /> Strata Overlying the Cameo Coal Seams <br /> This unit consists of interbedded sandstones and shales of <br /> discontinuous lateral extent. Consequently, the stratigraphy <br /> indicates that the entire sequence of strata overlying the coal <br /> zone in the permit area behaves as a single hydraulic unit which <br /> contains only localized perched aquifers in areas where it is <br /> recharged by the river. Ground water moves slowly through and <br /> between interconnected sandstone and shale lenses and beds . <br /> The Cameo Coal Aquifer <br /> The third aquifer is the Cameo coal seam. By its nature, the water <br /> quality and quantity is poor and unavailable for beneficial use . <br /> Water discharge occurs primarily as virgin coal seams are mined and <br /> drained locally. Discharge rates vary over time, indicating that <br /> this aquifer may be discontinuous over the permit area. <br /> Rollins Sandstone Aquifer <br /> The fourth aquifer is the Rollins sandstone and is geologically <br /> situated below the coal seam to be mined . This aquifer is <br /> comprised of a clean tan-to-cream sandstone that ranges from 89 to <br /> 114 feet thick throughout the permit area. Due to the extreme <br /> depth (from 50 to 1900 feet below surface) and location of the <br /> mining operation, it is believed that no damaging effect to this <br /> aquifer will occur . To date, there has been no significant impact <br /> on this aquifer. <br /> Additional issues that effect the hydrology of the site include <br /> waste pile impact on ground water supplies , in particular leachate <br /> generation . The effect of leachate from the Roadside coal <br /> processing waste pile on water quality is negligible. Using the <br /> worst-case scenario, where all precipitation enters the waste pile , <br /> an average of 0.01 cfs would enter the Colorado River via alluvium <br /> percolation. This would have the effect of raising the total <br /> dissolved solids content of the Colorado River by 0.01 percent. <br /> There is no evidence that leachate from the pile has ever reached <br /> or affected the Colorado River. <br /> _27_ <br />