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the escape shaft, ventilation fan, and MAC monitoring will be removed from other areas of the mine where they <br />are no longer needed, and reconstructed at the 18-Left site. The 18-Left facility will support the mine workings <br />in the proposed Western Mining District. <br />Locally significant are the rock units of Twentymile Park Basin which dip 5°-30° toward the central portion of <br />the basin. Normal faulting has been identified throughout the permit area, striking generally northwest to <br />southeast, with displacement of zero to 85 feet. A reverse fault running in an arcuate line northward through the <br />west central part of the basin shows displacement of 0-80 feet. Smaller lateral faults were encountered in the 9R <br />and l OR gateroads while driving development into the Eastern Mining District. <br />The near-surface bedrock units are composed of sedimentary rocks of marine and non-marine origin. These <br />sedimentary rocks were formed through the transgression and regression of an epicontinental sea and are <br />comprised of sequences of sandstones, siltstones, shales and coal. Four geologic formations exist in the vicinity <br />of the Eastern Mining District. They are, in ascending order, the Mancos Shale, the Iles and Williams Fork <br />Formations of the Mesaverde Group, and the Lewis Shale. These strata were all deposited during the late <br />Cretaceous Period. Generally, the strata dip to the center of the basin. <br />Three economically important coal seams, the Lennox, Wadge, and Wolf Creek coals, are located within the <br />locally important Middle Coal Group of the Williams Fork Formation. At this time, the Wadge coal seam is the <br />only seam being mined in the Foidel Creek underground mine. The Wadge Coal seam was strip mined in <br />CYCC's adjacent Energy No. 1 and Eckman Park Mines (No. C 1981-071) and Energy Mine No. 3 (C 1984- <br />062). <br />The Wadge coal seam, in the area of the Foidel Creek Mine, is separated from the underlying Trout Creek <br />sandstone by about 250 feet of interbedded sandstones, siltstones, shales and coals. The Wadge coal seam is <br />separated from the overlying Twentymile sandstone by 700 feet of massive shale and interbedded sandstones, <br />siltstones, shales and coals. Overburden depths in the current permit area range from 0 to 1,700 feet. <br />The stratigraphy and geologic structure within the Twentymile Park Synclinal Basin control the ground water <br />flow within the permit and adjacent areas. There are three regional bedrock aquifers within the permit and <br />adjacent areas of the Foidel Creek underground mine. These aquifers are the Trout Creek sandstone, the <br />Twentymile sandstone, and the Wadge coal-overburden zone. All three aquifers exhibit artesian conditions in <br />central portions of Twentymile Park Basin. The quality in all aquifers is moderately poor but is tolerable for use <br />as a drinking supply. <br />The geologic structure created by folding and faulting within the Twentymile Park Synclinal Basin affects the <br />direction of flow within the rock aquifers. In the permit and adjacent areas, the direction of ground water flow <br />in the bedrock aquifers is down dip toward the center of the Twentymile Park Basin. Faults in the area produce <br />localized fracture zones within the rock strata. These zones of increased permeability, in turn, increase the <br />potential for vertical and horizontal movement of ground water within the rock strata. However, experience to <br />date in the Foidel Creek mine shows little to no inflow along the fault zones at the level of the Wadge coal <br />seam. Some inflows were encountered in 9R and 6R gateroads as they were developed into the Eastern Mining <br />District. These inflows appeared to be localized, and tapered off over time. <br />The underlying 700-foot shale and the overlying shales and siltstones of the upper Williams Fork Formation and <br />the Lewis Shale Formations produce the confined artesian conditions within the Twentymile sandstone aquifer. <br />To the northeast, the Twentymile sandstone recharges the alluvial aquifer and provides base flow to the <br />tributaries of Trout Creek down gradient of the mine. Salts in the Twentymile sandstone waters are <br />predominantly sodium bicarbonate and result in TDS levels of 150 mg/l. This aquifer is tapped used for <br />domestic needs, and to a minor extent, for livestock. <br />7