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West Elk Mine <br />8-Seam Reserves <br />Reserves for the B-Seam at year-end 1996, are tabulated in Table 3. Because the combined <br />thickness of the B1 and B2 coal benches locally exceeds the maximum minable thickness, a 12 <br />foot maximum mining height was assumed to estimate the recoverable reserve. The maximum <br />minable thickness is controlled by operational and safety factors. The reserve estimate is <br />based upon current mining plans. <br />Several factors limit the minable B-Seam reserve (Map 13). On the north end of the coal lease azea <br />the recoverable B-Seam reserve is limited by Bear Coal Company's abandoned C-Seam mine <br />workings. Because these mine workings closely overlie the B-Seam (30 to 60 feet), the B-Seam is <br />considered unminable using longwall mining methods. This is to ensure that no connection <br />between the adjacent mines would occur as a result of undermining. <br />Other portions of the reserve are bounded by geologic factors. In the northern portions of the <br />Jumbo Mountain lease tract area, the B-Seam reserve is limited by an ancient landslide deposit. 1n <br />that area, a massive slide has removed the upper minable portion of the B-Seam. To the west, <br />south, and east, the B-Seam minable reserve is limited by excessive parting thickness as the B- <br />Seam coal benches diverge. <br />Access slopes from the F-Seam workings enter the B-Seam in the northwest quarter of Section 28, <br />T 135, R90W, 6th P.M. This location provides ready access to the B-Seam coal in the permit area. <br />•I 8-Seam Overburden and Interburden <br />B-Seam overburden ranges from zero feet at the outcrop along the North Fork and Minnesota <br />Creek drainages to 2,300 feet on the east side of the coal lease azea. Within the West Elk Mine <br />permit area, the average overburden is about 1,000 feet (Map 14). Within the permit area, the <br />overburden ranges from 200 feet to 2,300 feet and averages approximately 1,200 feet. <br />Interburden between the B-Seam and the overlying E-Seam ranges from 170 to 300 feet over the <br />property (Map 15) and between 240 and 260 feet in the Box Canyon permit revision azea. In the <br />area of the Oliver No. 2 Mine, the interburden depth between the B-Seam and the E-Seam is <br />estimated to be 250 feet. The interburden between the B-Seam and the overlying F-Seam ranges <br />from 320 feet to 450 feet (Map 16) and between 350 and 440 feet in the Box Canyon permit <br />revision azea. The B/F-Seam interburden includes the C, D, and E-Seams, of which only the E- <br />Seam is of significant additional economic importance over the permit azea. <br />Lithologies within the B/E-Seam interburden consist of shales, siltstones, and coals. Sandstones <br />are generally lenticulaz, with the exception of the massive "Sub-D" sandstone. This sandstone <br />unit usually lies close under the bottom of the D-Seam, and ranges from 20 to 225 feet thick. It <br />can be divided into two laterally continuous sandstone bodies which have informally been <br />designated as the "Upper Marine Sandstone" and the "Lower Marine Sandstone" (Figure SA, <br />Figure SB, Figure SC, Figure 5D, Figure SE, and Figure SF). In the western portions of the <br />I initial mining area and into the Jumbo Mountain lease tract, only the lower lobe of this sandstone <br />. body occurs (Figure SB, Figure SD, and Figure SF). <br />2.04-28 RevisedJurt. 1995 PR06: RevisedJart. 1998 PR08 <br />