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Williams Fork.Fotmations are sepazated by impermeable interbedded shales within <br />the Mesaverde. The sandstones are lenticular in nature, pinching out laterally in <br />both directions from the mine site and aze characterized as fine- to medium- <br />grained, calcite cemented units. <br />The deepest sandstone, the Sego of the Iles Formation (Collins, 1976) pinches out <br />from a maximum thickness of 40 feet neaz Piceance Gap (northwest of the <br />minesite) toward New Castle to the southeast. The Trout Creek Sandstone, in the <br />upper portion of the Iles Formation, lies approximately 800 feet above the Sego <br />and consists of 50 to 145 feet of silty, calcite-cemented, massively bedded buff to <br />white sandstone. <br />The overlying Williams Fork Formation contains numerous predominantly non- <br />marine sandstones, interbedded with siltstones, coals, claystones, and shales. The <br />Wheeler is generally considered the lower-most coal of the Williams Fork <br />Formation in the area. The E Seam to be mined within this permit term lies within <br />the upper-most portion of the Iles Formation. Together, these seams lie within the <br />lower 1200 feet of the Mesaverde Group, stratigraphically covered by 3700 feet of <br />interbedded sediments. The low permeability of these interbedded units effectively <br />isolates the coal seams from shallow ground water south of the Grand Hogback. <br />Three domestic wells have been completed in the shallow bedrock aquifers of the <br />azea. These wells have been drilled in the Upper Williams Fork Formation. The <br />Gamber Well is located approximately 7 miles southeast of the minesite; the <br />Becker Well is located approximately 1 mile southwest of the life-of--mine permit <br />boundary and 3 miles southwest of the 5-year permit term. Both of these wells, <br />from the indicated depth of completion, appear to tap the uppermost sandstone <br />units of the Williams Fork Formation. The Seivers Well is located approximately <br />2'k miles southeast of the portal area and 1'fz miles south of the life-of--mine <br />permit boundary. This well has a total depth of 55 feet. This well is located only <br />'b mile south of the outcrop of the Wheeler Seam. However, due to the extreme <br />dip in the area, the well is separated from the seam by several hundred feet of low <br />permeability units. The proposed mining operation will not impact these wells, as, <br />at a minimum, the producing unit will be separated from the coal seams by 200 <br />feet of low permeability units. <br />There are numerous alluvial wells south of the permit azea along the Colorado <br />River. The alluvium thickness is projected to be up to 87 feet. The ground water <br />provides domestic and livestock water for 26 wells in the vicinity of the minesite. <br />Water yields of these alluvial wells range from 2 to 50 gpm. <br />Alluvial aquifer potential also exists along the Elk Creek Drainage north of the <br />Grand Hogback. This alluvium is perched on Mancos Shales and is isolated from <br />the coal seams at the Eastside Mine by this impermeable unit. <br />The alluvium fringing the Colorado River is separated from the Mesaverde <br />Formation by relatively impervious units of the Wasatch Formation. There is the <br />12 <br />