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2022-02-22_PERMIT FILE - C1980007 (5)
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2022-02-22_PERMIT FILE - C1980007 (5)
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Last modified
2/24/2022 2:08:03 PM
Creation date
2/24/2022 2:02:25 PM
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Template:
DRMS Permit Index
Permit No
C1980007
IBM Index Class Name
Permit File
Doc Date
2/22/2022
Doc Name
2.04-12 Thru 2.04-50
Section_Exhibit Name
2.04.6 Geology Description
Media Type
D
Archive
No
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West Elk Mine <br />2.04-33 Rev. 11/04- PR10, 04/06- PR10, 09/07- PR12, 10/08- PR14; 01/22- MR459 <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. Carbonaceous 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 are un-correlatable and not economically recoverable. <br /> <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 permit area, and elsewhere around the coal lease <br />area. The location of these holes is shown on Map 8 and the analytical results are 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 acid- or <br />toxic-forming materials. <br /> <br />F Seam Roof and Floor <br /> <br />Within the West Elk Mine coal lease area, the F Seam roof lithology is somewhat variable in <br />nature. The immediate roof lithology is typically a dark gray mudstone that cont ains abundant <br />slickensides (indicative of compaction) within 5 feet of the coal seam. Roof conditions are 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 /> <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 has scoured into the F <br />Seam top and significantly reduced the coal thickness, mining operations had to be discontinued. <br /> <br />The floor of the F Seam is predominantly shale. Because locally this shale is soft, exhibits <br />rooting, and tends to be water sensitive, floor conditions were frequently poor within the West <br />Elk Mine. Occasionally, more competent coarse-grained lithologies occur immediately below <br />the F Seam. In these areas, improved floor conditions were experienced. <br /> <br />Structural Geology <br /> <br />Because the two economically recoverable seams, B and E, directly and indirectly overlie one <br />another, their structural characteristics are similar. The E and B Seams strike north 60 degrees <br />west and dip 3 to 5 degrees northeast across the lease block. Howev er, 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 area. Locally, more steep undulations in structure occur. These <br />undulations or "rolls" experienced during mining are likely caused by the differential compaction <br />of sediments. <br /> <br />Several major structural faults are known or are projected to occur in the MCC lease. Analysis of <br />these faults has identified them as normal faults formed by a deep pluton in the Mancos Shale <br />displacing existing fractures. The faults vary greatly in offset from inches to 22 feet depending on <br />their relative location to the pluton. The faults are known to diminish vertically toward the surface <br />as strain is partitioned into the weaker strata as horizontal slip planes. Surface expression of the
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