2010-05-07_PERMIT FILE - C2009087 (6)

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and under - burden geochemistry is presented in the following Interpretation of Geochemical Overburden Data section. • Directly elow the Wad e Seam in the planned PSCM area, is a persistent and laterally continuous Y g P P Y layer of material composed of clay -sized particles called underclay. Beneath this underclay is a zone of alternating thick shales, claystones, siltstones, and intermittent lenticular sandstones. The shales are generally continuous and the sandstones discontinuous. Near the base of this zone of alternating beds is the Wolf Creek Seam. Within the proposed PSCM area, the Wolf Creek Seam splits into two or more separate coal beds. The continuity of the lower Wolf Creek Seam, locally mapped as "WC" beds, improves westward. The "WC" beds are clearly correlated using the unique properties of the Yampa Bed, an altered volcanic ash fall tuff bed used throughout most of the Yampa Coal Field. The Wolf Creek seam is separated from the underlying massive Trout Creek Sandstone by alternating beds consisting mostly of shale. Similar to the Twentymile Sandstone, the Trout Creek Sandstone. is fine - grained and is a key marker bed. It defines the bottom of the Williams Fork Formation and the top of the Iles Formation. Immediately beneath the Trout Creek Sandstone is a massive marine shale. Structure The regional geologic structure of the Sand Wash Basin is a complex of folds dominated by the Axial Basin Uplift to the southwest and the Park Range Uplift to the east. The Axial Basin Uplift, an anticline, is a southeastward extension of the larger Uinta Mountain Arch to the west, which • trends west by northwest. Between the Axial Basin Anticline and the Park Range Uplift is a series of synclines, anticlines, and monoclines. The PSCM is located between two of these smaller anticlines: the Fish Creek Anticline to the west and the Tow Creek Anticline to the east. Geological cross sections of the PSCM permit area are presented in Exhibit 2.04.6 -E1, Geologic Information — Geologic Cross Sections (confidential). The western PSCM permit boundary is located on the eastern limb of the Fish Creek Anticline. The Fish Creek Anticline is a north- northwest plunging asymmetrical fold with strata dipping (inclining) steeper on the east side of the fold axis. Outcrops on the eastern limb of the anticline dip 50 degrees to 60 degrees (Robson & Stewart, 1990). The rocks of the anticline have not been stressed sufficiently to cause them to abundantly fracture. The eastern limb of the Fish Creek Anticline is shared with the western limb of the Hayden Syncline. The PSCM permit boundary will be transected by the axial trough of the Hayden Syncline. The Hayden Syncline is a northwest plunging fold that extends well beyond the PSCM permit boundary up to the Cherokee Arch to the north. Bedding orientation on the eastern limb, as measured on surface outcrops, strike east to northeast and dip 10 degrees to 25 degrees. Dips on the shared limb with the Fish Creek Anticline are normally between 50 degrees and 60 degrees (Robson & Stewart, 1990). The eastern limb of the Hayden Creek Syncline is shared with the western limb of the Tow Creek Anticline. The Tow Creek Anticline is an asymmetrical fold plunging south - southwest and is the • largest undulation amongst the regional synclinal structure according to Bass et al. (1955); it has approximately 3,000 feet of vertical relief. The axis of the Tow Creek Anticline will transect the eastern portion of the PSCM permit boundary. The eastern PSCM permit boundary is located on PSCM Permit App. 2.04 -28 6/15/09