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West Elk Mine <br />FSeam Overburden <br />Within the West Elk Mine coal lease azea, an average of about 700 feet of strata overlie the F Seam <br />{Map 23). This interval ranges from 0 to 1,500 feet thick. The lithologies within the overburden <br />consist of shales, siltstones, and sandstones with local thin coals. Sandstones are predominantly <br />lenticular. Shale and siltstone intervals often occur as thin interbedded sequences that show <br />distorted bedding. Cazbonaceous plant fragments occur occasionally within all lithologies in the <br />overburden. The coals above the F Seam are all thin and discontinuous. Because of this lenticular <br />nature, the seams aze un-correlatable and not economically recoverable. <br />Representative samples of the F Seam coal, overburden, roof, and floor strata have been collected <br />and analyzed from core holes drilled within the pemrit area, and elsewhere azound the coal lease <br />azea. The location of these holes is shown on Map 8 and the analytical results aze presented in <br />Exhibit 13. Stratigraphic cross-sections and geochemical analyses indicate that these results are <br />representative of the existing conditions throughout the West Elk Mine coal lease area and that the <br />B, E, and F coal seams and associated roof and floor materials do not contain potential <br />acid- ortoxic-forming materials. <br />FSeam Roof and Floor <br />Within the West Elk Mine coal lease azea, the F Seam roof lithology is somewhat variable in <br />. nature. The immediate roof lithology is typically a dark gray mudstone that contains abundant <br />slickensides (indicative of compaction) within 5 feet of the coal seam. Roof conditions aze often <br />poor where slickensides have weakened the integrity of the roof strata. Within West Elk Mine, <br />the overlying slickensided mudstone commonly fell. <br />Above this mudstone layer, thick fluvial channel deposits often occur. Locally, these channels <br />have scoured into the underlying finer-grained deposits and as a result, sandstone lies directly <br />atop the F Seam coal. Where the erosional base of the channel deposits have scoured into the F <br />Seam top and significantly reduced the coal thickness, mining operations had to be discontinued. <br />The floor of the F Seam is predominantly shale. Because locally this shale is soft, exhibits <br />rooting, and has a tendency to be water sensitive, floor conditions were frequently poor within <br />the West Elk Mine. Occasionally, more competent coazse-grained lithologies occur immediately <br />below the F Seam. In these azeas, improved floor conditions were experienced. <br />Structural Geoloev <br />Because the two economically recoverable seams, B and E, directly and indirectly overlie one <br />another, their structural chazacteristics are similar. The E and B Seams strike north 60 degrees <br />west and dip 3 to 5 degrees northeast across the lease block. However, both the E and B Seams <br />change strike to approximately east-west and the dip flattens to one to two degrees in much of <br />the Box Canyon permit revision azea. Locally, more steep undulations in structure occur. These <br />undulations or "rolls" experienced during mining aze likely caused by the differential compaction <br />of sediments. <br />1.04-33 RevisedNwember 1004 PRIG <br />