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North, Range 87 West. Mining during the second and third terms is proposed in Sections <br />17, 19, and 20. <br />Geology and Topography <br />The proposed Yoast permit azea is located within the Wyoming Basin Physiographic <br />Province. Elevations within the permit area range between 6530 feet along the northern <br />end of the proposed haul road and 7980 feet at the summits of ridges within the <br />southeastern portion of the proposed permit area. Slopes range from 1° in Scotchman's <br />Gulch to 100° at isolated sandstone bluffs. The terrain is chazacterized by broad west and <br />northeast facing moderately sloping benches and ridges that are deeply incised, and barren, <br />brush covered, southwestward facing cliffs where the more resistant sandstone outcrops. <br />The long, sloping landforms of these azeas roughly coincide with the strike and dip of the <br />underlying bedrock. <br />The proposed permit azea is dissected by several small, ephemeral drainages which flow into <br />two principal stream systems; Sage Creek on the southwest, Grassy Creek on the southeast. <br />A detailed discussion of the Yoast surface water system is presented in Tabs 7 and 16 of the <br />permit application package. <br />The Yoast permit area is in the Williams Fork Mountains, within the southeastern synclinal <br />portion of the Sand Wash structural Basin of northern Colorado and central Wyoming. The <br />stratigraphy of the permit area is illustrated in Figure 2. <br />The coal seams to be mined are the Wadge and the Wolf Creek. These seams are contained <br />within the Middle Coal Group, an interval of interbedded sandstones, sandy shales, shales <br />and coal within the Williams Fork Formation. The Middle Coal Group also contains the <br />Lennox Coal seam which is non-commercially mined in the Yoast mine. Above the Middle <br />Coal Group is the Twentymile Sandstone, a 100-200 foot thick fine-grained, massive <br />sandstone. The upper unit of the Williams Fork Formation, which contains the Upper Coal <br />Group of the Mesaverde group, consists of layers of sandstone, sandy shale, shale, and coal. <br />The thickmess of this unit varies from approximately 200 to 850 feet throughout the region. <br />The Williams Fork comprises the upper 200 to 850 feet of the Cretaceous Mesaverde <br />Group. <br />Underlying the Williams Fork Formation is the Iles Formation which is the lower member <br />of the Mesaverde and the oldest unit to out crop in the permit azea. The IIes Formation <br />is approximately 1500 feet thick. The basal unit of the Iles Formation is the Tow Creek <br />Sandstone, a 35-125 foot thick massive, fine-grained, well-sorted sandstone. Overlying the <br />Tow Creek Sandstone is a 1200 foot thick interval of interbedded shales, sandstones and <br />coals known as the lower coal group. The Iles Formation is crowned by the Trout Creek <br />Sandstone, which is a massive fine-grained sandstone with a thickness of approximately 100 <br />feet. <br />Yoast Minc 7 ~ July 4 1995 <br />