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GVest Elk Mine <br />. Sandstone Channel Deaosits <br />Zones of abrupt lithologic changes, such as those created by sandstone channels, historically <br />coincide with azeas of unstable roof. Numerous slickensided fractures in weak shales, <br />claystones, and coal neaz sandstone channels can result in localized mine roof control problems. <br />Based on MCCs prior mining experience, the two primary conditions of concern aze: 1) <br />Rapid changes in lithology from the resistant sandstones and siltstones of channel deposits to <br />claystones, and 2) Shales and sandstones subject to differential compaction and stresses, <br />producing slickensides. The presence of perched ground water in the sandstone channels <br />aggravates these conditions by weakening the associated shales. <br />The 40-foot zone above the F Seam appears to contain channel deposit trends or systems. About <br />30 percent of the lease block may be affected in the E Seam. The channel systems have a <br />generally downward concavity and have been found to range from 1,500 feet to 3,000 feet in <br />width. These systems may be made up of many channels or a single, meandering channel. If the <br />interface between sandstone and shale is a gentle slope, the affects on mining will be less than a <br />steeply inclined interface. An assessment of these roof conditions and cracks is contained in <br />Exhibit 16. Similaz features are rare or absent in the B Seam mine. Although these channels <br />may cause roof problems, it should be pointed out that previous mining has been conducted <br />safely and effectively in nearby mines. <br />Rolls <br />• Rolls aze a steep undulation on the mine floor that is greater than the regional dip. Rolls are <br />normally too small to be delineated from core hole data. Such structures could be present in any <br />seam in the West Ells Mine coal lease area. Anomalous dips in the F Seam in the Sylvester <br />Gulch indicate at least a minor roll with an apparent northeast trending axis. The degree of dip <br />of the B and E Seam is not constant and localized variations in the regional dip do occur, but <br />have little or no impact on mining. <br />Rock Spars <br />Rock spazs aze present in the West Elk Mine B Seam, the Beaz Mine C Seam, the Somerset Mine <br />in the B and C Seams, and the Sanborn Creek B Seam Mine. They aze generally vertical, up to <br />four feet in thickness and usually thinning upward. The spars aze from a few feet to over ahalf- <br />mile in length. There has been no evidence from in-mine or core hole data of their presence in <br />the F Seam, or the E Seam. Clay dikes were observed in the B Seam test adit, on the north end <br />of the property, and spars have been encountered underground in the B Seam mine. Rock spars <br />in the E Seam are possible from the overlying sandstone channels but should be of limited <br />thickness and lateral extent. Little to no impact to mining is expected from the rock spars. <br />Seam Discontinuities <br />Seam discontinuities (i.e., rapid seam thinning due to non-deposition, channel cutouts, or <br />• faulting) can occur anywhere in the coal lease azea. Small faults (<10 feet displacement) have <br />been encountered in the F and B Seam workings. These have not caused any major problems <br />1.04-48 Revised November 2004 PRI G <br />