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-6- Four geologic formations exist in the vicinity of the proposed Foidel Creek underground mine. They are, in ascending order, the Mancos Shale, the Iles and Williams Fork Formations of the hlesaverde Group, and the Lewis Shale Formation (see Figures 2 and 3 of this document). These strata were all deposited during the late Cretaceous Period. Generally, the strata dip to the northwest at about 5.7o into the Twentymile Park Basin. The Mancos Shale is the oldest sedimentary formation in the area of the mine. This formation consists of over 5300 feet of marine shale, with minor interbedding of sandstone and limestone. The Iles Formation overlies the Mancos Shale and underlies the Williams Fork Formation and outcrops southeast of the proposed mine workings. The strata generally consist of a massive marine shale and two massive medium- to fine-grained sandstones, the Trout Creek and Tow Creek sandstones. The Trout Creek sandstone is a regional marker bed at the top of the Iles Formation and the Tow Creek sandstone is a regional marker bed at the bottom of the I]es Formation. The Williams Fork Formation overlies the Trout Creek sandstone of the Iles Formation. The Williams Fork Formation consists of massive sandstones and shales; interbedded shales, siltstones, sandstones and coals; and lenticular sandstones. The Twentymile sandstone is the only massive reyional sandstone and is used as a key marker bed within the region. Three mineable coal seams, the Lennox, Wadge, and Wolf Creek coals, are located within the Williams Fork Formation. The Wadge coal seam is either presently being or has previously been strip mined within the adjacent Energy No. 1, No. 2 and Eckman Park mines. The Wadge coal seam will be mined in the Foitlel Creek underground mine. The Wadge coal seam, in the area of the Foidel Creek Mine, is separated from the underlying Trout Creek sandstone by about 25U 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 proposed permit area range from 0 to 1300 feet (see Map 7 of the permit application). The youngest strata in the proposed permit area are located in the Lewis Shale Formation. The massive marine shale unit is stratigraphically situated about 200 feet above the Twentymile sandstone. Near the base of the Lewis Shale is the Fish Creek coal seam. Previous surface coal mining operations at the Energy No. 2 mine near the northwest corner of the proposed permit area have removed a portion of the Fish Creek coal seam. The stratigraphy and geologic structure within the Twentymile Park Synclinal Basin control the ground water flow within the permit and adjacent areas.