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Three economically important coal seams, the Lennox, Wadge, and Wolf Creek coals, are located within the locally important Middle Coal Group of the Williams Fork Formation. At this time, the Wadge coal seam is the only seam being mined in the Foidel Creek underground mine. The Wadge Coal seam was strip mined in CYCC's adjacent Energy No. I and Eckman Park Mines (No. C-81-071) and Energy Mine No. 3 (C-84-062). The Wadge coal seam, in the area of the Foidel Creek Mine, is separated from the underlying Trout Creek sandstone by about 250 feet of interbedded sandstones, siltstones, shales and coals. The Wadge coal seam is separated from the overlying Twentymile sandstone by 700 feet of massive shale and interbedded sandstones, siltstones, shales and coals. Overburden depths in the current permit azea range from 0 to 1,700 feet. The stratigraphy and geologic structure within the Twentymile Park Synclinal Basin control [he ground water flow within the permit and adjacent areas. There are three regional bedrock aquifers within the permit and adjacent areas of the Foidel Creek underground mine. These aquifers aze the Trout Creek sandstone, the Twentymile sandstone, and the Wadge coal-overburden zone. All three aquifers exhibit artesian conditions in central portions of Twentymile Park Basin. The quality in all aquifers is moderately poor but is tolerable for use as a drinking supply. The geologic structure created by folding and faulting within the Twentymile Park Synclinal Basin affects the direction of flow within the rock aquifers. In the permit and adjacent areas, the direction of ground water flow in the bedrock aquifers is down dip toward the center of the Twentymile Park Basin. Faults in the area produce localized fracture zones within the rock strata. These zones of increased permeability, in turn, increase the potential for vertical and horizontal movement of ground water within the rock strata. However, experience to date in the Foidel Creek mine shows little to no inflow along the fault zones at the level of the Wadge coal seam. Some inflows were encountered in 9R, and 6R gateroad as they were developed into the Eastern Mining District. These inflows appeared to be localized, and tapered off over time. The Twentymile sandstone is separated from the underlying Wadge coal-overburden aquifer by up to 700 feet of impermeable shale within the permit and adjacent areas. The underlying 700-foot shale and the overlying shales and siltstones of the upper Williams Fork Formation and the Lewis Shale Formations produce the confined artesian conditions within the Twentymile sandstone aquifer. To the northeast, the Twentymile sandstone recharges the alluvial aquifer and provides base flow to the tributaries of Trout Creek down gradient of the mine. Salts in the Twentymile sandstone waters are predominantly sodium bicarbonate and result in TDS levels of 150 mg/I. This aquifer is occasionally used for domestic needs. The alluvium of Trout Creek and its tributaries is an important source of ground water. The alluvial bodies are used as water supplies, provide subirrigation to vegetation, and supply base flow to the streams. The alluvial bodies are recharged by both the streams and the bedrock aquifers. The mine is located in the upper reaches of the Yampa River Basin. The permit area and adjacent areas are drained by Foidel Creek, an intermittent stream ,and Fish Creek and Middle Creek, both perennial streams. Fish Creek drains east into Trout Creek whereas Foidel Creek drains northeast to Middle Creek before Middle Creek joins Trout Creek. The quality of water in the Fish Creek and Foidel Creek drainages have been affected previously by surface mining upstream and downstream of the underground mine's existing surface facilities. Alluvial valley floors are identified downstream of the mining area at the confluence of Foidel and Middle Creek, and on Trout Creek from its confluence with Middle Creek downstream to the Yampa River. Permit Revision No. 3 declassified portions of Foidel and Middle creeks