2017-02-03_PERMIT FILE - C1980004 (2)

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2.04.6 Geology Description surface evidence, the roof rock appears to consist of either gray to black shales, competent sandstones, or extensive zones of thinly laminated alternating beds of each. This depositional environment appears to be part of the delta system with frequent transgressive and regressive impulses. Because of this very dynamic depositional environment, correlation of specific sands or shales over extensive areas is very difficult or in most cases impossible. The result is rapidly changing roof rock types and competence. Generally, the thinly bedded alternating sands and shales, as well as the shales on the edges of channel sands whose competence is lessened by differential compaction are given the most attention. The floor rock is most often shales, or coal in the thick seam areas, which has few troubles with heaving. Analysis of the roof and floor rock at the McClane Canyon site (in accordance with 30 CFR 783) are presented in Tables 2.1.4 and 2.1.5. Based upon these observations, the roof and floor rock appears to be competent with minor areas of spalling, which is a manageable problem. Overburden thickness in the permit area varies from 0 to 2000 feet (See Figure 2.1.8). Where excessive overburden, over 1,400 feet, was encountered within the graben, considerable deterioration of mining conditions occurred. Whether this condition is exclusive to the graben remains to be seen. Extensive rib sloughage and increased difficulty holding the thinly laminated beds forming the roof contribute to make coal recovery uneconomical. Coal from drill cores in Section 15 and further northeastward in the graben also exhibits extensive slickensides and slips suggesting multidirectional and unpredictable forces. In light of the overburden and graben's influence on mining economics, the operator has adjusted its reserve estimates in a number of areas of the permit. Below is a table summarizing the minable and recoverable reserves. PR -02 2.04-11 08/11