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Description of [he Environment <br />The Yoast Mine plan area is located approximately 8.5 miles southeast of the town of Hayden, and <br />is positioned between three existing coal mining operations. The Yoast Mine plan area is <br />approximately 4 miles southwest of the Seneca II Mine, 3.5 miles east of the Seneca II-W mine, and <br />one mile west of the reclaimed Grassy Gap Mine. See Figure 1 for further detail. The mining area <br />is located between Sage Creek and Grassy Creek and is found on USGS Mount Harris and Dunkley <br />maps. <br />Mining is proposed in two separate areas, and in the neck pit connecting the two azeas. During the <br />first five year permit term, mining will develop in Section 17 of Township 5 North, Range 87 West. <br />Mining during the second and third terms is proposed in Sections 17, 19, 20, 29, and 30. <br />Geology and Topoaraphy <br />The proposed Yoast permit area is located within the Wyoming Basin Physiographic Province. <br />Elevations within the permit area range between 6530 feet along the northern end of Haul Road A <br />and 7980 feet at the summits of ridges within the southeastern portion of the proposed permit area. <br />Slopes range from 1° in Scotchman's Gulch to 100° at isolated sandstone bluffs. The terrain is <br />characterized by broad west and northeast facing moderately sloping benches and ridges that are <br />deeply incised, and barren, brush covered, southwestward facing cliffs where the more resistant <br />sandstone outcrops. The long, sloping landforms of these areas roughly coincide with the strike and <br />dip of the underlying bedrock. <br />The proposed permit area is dissected by several small, ephemera] drainages which flow into two <br />principal stream systems; Sage Creek on the southwest, Grassy Creek on the southeast. A detailed <br />discussion of the Yoast surface water system is presented in Tabs 7 and 16 of the permit application <br />package. <br />The Yoast permit area is in the Williams Fork Mountains, within the southeastern synclinal portion <br />of the Sand Wash structural Basin of northern Colorado and central Wyoming. The stratigraphy of <br />the permit azea is illustrated in Figure 2. <br />The coal seams to be mined are the Wadge and the Wolf Creek. These seams are contained within <br />the Middle Coal Group, an interval of interbedded sandstones, sandy shales, shales and coal within <br />the Williams Fork Formation. The Middle Coal Group also contains the Lennox Coal seam which <br />is non-commercially mined in the Yoast mine. Above the Middle Coal Group is the Twentymile <br />Sandstone, a 100-200 foot thick fine-grained, massive sandstone. The upper unit of the Williams <br />Fork Formation, which contains the Upper Coal Group of the Mesaverde group, consists of layers <br />of sandstone, sandy shale, shale, and coal. The thickness of this unit varies from approximately 200 <br />to 850 feet throughout the region. The Williams Fork comprises the upper 200 to 850 feet of the <br />Cretaceous Mesaverde Group. <br />Underlying the Williams Fork Formation is the Iles Formation which is the lower member of the <br />Mesaverde and the oldest unit to out crop in the permit area. The Des Formation is approximately <br />Yoaxt Mine O Match 6, ?001 <br />