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1500 feet thick. The basal unit of the Iles Fotmation is the Tow Creek Sandstone, a 35-125 foot <br />thick massive, fine-grained, well-sorted sandstone. Overlying the Tow Creek Sandstone is a 1200 <br />foot thick interval of interbedded shales, sandstones and coals known as the lower coal group. The <br />Des Formation is crowned by the Trout Creek Sandstone, which is a massive fine-grained sandstone <br />with a thickness of approximately 100 feet. <br />The Late Cretaceous Mancos Shale underlies the lies Formation and outcrops southwest of the <br />permit boundary along Sage Creek and the Sage Creek Anticline. The Mancos Shale is a dark grey <br />marine shale with interbedded sandstones near the top and interbedded sandstone and limestone near <br />the bottom. <br />Overlying the Mesaverde Group is the Lewis Shale, a homogeneous marine shale with a thickness <br />of between 1000 and 1500 feet. The Lewis Shale is overlain by the Cretaceous Lance Formation and <br />the Tertiary Fort Union Formation. The Wasatch Formation of Eocene age unconformably overlies <br />the Fort Union Formation. It is comprised primarily of fresh water stream-laid sandstone and shale <br />deposits. Unconsolidated alluvial, terrace, and surficial deposits of Quaternary age overlie the <br />exposed geologic formations in some azeas, particularly along larger streams. <br />The proposed permit area lies structurally between the parallel, south-southeast trending Sage Creek <br />and Fish Creek anticlines. The axis of the Sage Creek Anticline is situated about one to two miles <br />west of the western edge of the Yoast permit area. The axis of the Fish Creek Anticline originates <br />near Scotchman's Draw and extends south-southeasterly dividing the northern first five-year mine <br />block from the neck portion of the permit area. <br />The rock units in the proposed permit area dip predominantly 15 to 20 percent to the north in the <br />north mine block, to the northwest in the neck area, and to the west in the south mine block. More <br />extreme dips of 25 to 35 percent occur locally in the northwest and northeast parts of the north mine <br />block. The rock units are apparently unaffected by any significant faulting within the permit area. <br />Surface Water <br />The Yoast Mine drains to Sage Creek on the west side, and to Grassy Creek on the east side. Sage <br />Creek and Grassy Creek are perennial tributaries to the Yampa River. Annand Draw and Scotchmans <br />Gulch are intermittent drainages which drain from the northern side of the proposed permit area into <br />Grassy Creek. The Yampa River then flows to the Green River and eventually the Colorado River. <br />Refer to Figure 3 for more detail. <br />Sage Creek <br />Sage Creek is a perennial stream to the west of the proposed permit area. Flows upstream from the <br />proposed permit area range from an average 0.7 cubic feet per second (cfs) in the spring to near 0 <br />in late summer and fall. Approximately two miles downstream from the permit area, average flows <br />of 1.5, 0.09, and 0.04 cfs were observed during baseline data collection in the spring, summer, and <br />fall respectively. <br />Yonsi Mine 10 March 6.?001 <br />