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Foidel Creek underground mine. The Wadge Coal seam historically has been <br />and presently is being strip mined within Colorado Yampa Coal Company's <br />adjacent Energy No. 1, No. 2 and Eckman Park Mines. CYCC has recently <br />submitted an application to mine the Wolf Creek seam. <br />The Wadge coal seam, in the area of the Foidel Creek Mine, is separated <br />from the underlying Trout Creek sandstone by about 250 feet of <br />interbedded sandstones, siltstones, shales and coals. The Wadge coal <br />seam is separated from the overlying Twentymile sandstone by 700 feet of <br />massive shale and interbedded sandstones, siltstones, shales and coals. <br />Overburden depths in the proposed permit area range from 0 to 1,700 feet <br />(see Map 6 of the permit application). <br />The stratigraphy and geologic structure within the Twentymile Park <br />Synclinal Basin control the ground water flow within the permit and <br />adjacent areas. There are three regional bedrock aquifers within the <br />permit and adjacent areas of the Foidel Creek underground mine. These <br />aquifers are the Trout Creek sandstone, the Twentymile sandstone, and the <br />Wadge coal-overburden zone. All three aquifers exhibit artesian <br />conditions in central portions of Twentymile Park Basin. The quality in <br />all aquifers is moderately poor and is tolerable for use as a drinking <br />supply. <br />The folding and faulting (geologic structure} within the Twentymile Park <br />Synclinal Basin affects the direction of flow within the rock aquifers. <br />In the permit and adjacent areas, the ground water flow in the bedrock <br />aquifers is down the dip of the strata into the Twentymile Park Basin. <br />Faults in the area produce localized fracture zones within the rock <br />strata. These zones of increased permeability, in turn, increase the <br />potential for vertical and horizontal movement of ground water within the <br />rock strata. <br />The Twentymile sandstone is separated from the Wadge coal-overburden <br />aquifer by up to 700 feet of impermeable shale within the permit and <br />adjacent areas. The underlying 700-foot shale and the overlying shales <br />and siltstones of the upper Williams Fork Formation and the Lewis Shale <br />Formations produce the confined artesian conditions within the Twentymile <br />sandstone aquifer. To the northeast, the Twentymile sandstone recharges <br />the alluvial aquifer and provides base flow to the tributaries of Trout <br />Creek down gradient of the mine. Salts in the Twentymile sandstone <br />waters are predominantly sodium bicarbonate and result in TDS levels of <br />150 mg/1. This aquifer is occasionally used for domestic needs. <br />The alluvia of Trout Creek and its tributaries are important sources of <br />ground water. The alluvial bodies are used as water supplies, provide <br />subirrigation to vegetation, and supply base flow to the streams. The <br />alluvial bodies are recharged by both the streams and the bedrock <br />aquifers. <br />-6- <br />