2010-01-25_PERMIT FILE - C1981044A (3)

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fragments and ranges from 15 to 30 feet thick. The shale fragments would seem to indicate a marginal marine to lower delta environment for this sandstone, and therefore, the base of this sandstone probably marks the second unconformity. Above this sandstone is a sequence of shales and sandy shales that grade upward to [he thick cross- bedded Twentymile Sandstone. The interval thickness between the Middle Sandstone and the Twentymile Sandstone is presented in Figure 7, Isopach, Middle Sandstone to Twentymile Sandstone. This coarsening upward sequence probably represents the lower and upper shore face sediments that mark the beginning of a new regression. The Twentymile Sandstone averages about 120 feet thick. In deeper parts of the basin this unit can be a prolific water producer, however, over most of the mine area yields from the Twentymile Sandstone are low. The sediments overlying the Twentymile Sandstone are primarily of continental origin and include numerous coal seams and typical shale-sandstone units. These channel sands, swamp mud, coal and associated lithologies represent deposition in generally higher energy environments that the coals of the lower coal group. Coals found in these units are generally not economically mineable. The "P" Coal Seam does occur in this formation which is historically called the upper coal group. The interval thickness between the Twentymile Sandstone and the "P" coal seam is presented in Figure 9, Isopach, and Twentymile Sandstone to the "P" Coal Seam. The final unconformity is placed at the base of a three (3) sandstone lenses locally known as the While Sandstone. In reality, the base of each of the sandstone lenses is probably non-conformable and the third sandstone may even be a transgressive deposit, which is in itself unusual. Mr. Ed Johnson, (United States Geological Survey, Coal Resouces Division), has mapped these units and believes that the third sandstone is indeed the beach deposit of the advancing Lewis Sea. The total thickness of the White Sandstone is on the order of 310 to 360 feet. Each bench however, is on the order of 90 feet thick. The White Sandstone is remarkably white on the outcrop as well as in the drill hole cuttings. The White Sandstone is clay filled and exhibits a low primary permeability. The interval thickness between the "P" Coal Seam and the White Sandstone is presented in Figure 1Q, Isopach, "P" Coal Seam to the White Sandstone. The thickness of the White Sandstone itself is preserved in Figure 11, Isopach, First White Sandstone. Lewis Shale The Lewis Shale caps the coal bearing sequences and contains the marine fades of the Lewis Sea. Although the Lewis Shale occasionally contains this, discontinuous sandstone lenses, the unit on the whole is an aquiclude. The shale is bentonitic and swells when hydrated. Information o the characteristics of the major lithologic units discussed is presented in Table 8, Characteristics of Major Lithologic Units. STRUCTURAL GEOLOGY The structural characteristics of the coal seams and associated lithotypes in the vicinity of the EC operation are controlled by three (3) major folds; these are 1) The Williams Fork anticline, 2) the Round Bottom syncline, and 3) the Big Bottom syncline. The dip of the beds in the area is strictly governed by these features. Associated with these features are some locally occurring ten[ional faults. Mining operations in the Eagle No. 5 Mine have encountered three (3) relatively small faults. Two (2) of these faults were mapped by aerial photogrammetrics and/or field surveys, however, their third fault does not express itself on the surface. The maximum displacement measured at these faults is on [he order of 40 feet. Three (3) smaller faults were encountered in the now abandoned No. 9 Mine. These were normal faults and exhibit displacement of less than ten feet. The major sandstones show minor jointing patterns aligned along the dip of the units. This jointing is restricted to individual beds within [he sandstones and does not appear to indicate a major structural weakness. The coal seams vary from cleated to non-cleated conditions. The majority of the mine area and certainly the mineable par[ of the area lie on the northeastward dipping limb of the Williams Fork anticline/Big Bottom syncline pair. The average dip of the coal seams in the area range from 8 degrees Permit Revision 04-34 2.04-7 Revised 7/2/04