2006-06-02_PERMIT FILE - C1980007A (3)

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West Elk Mine Ohio Creek Member The Ohio Creek Member is the uppermost member of the Mesaverde Group. This unit is approximately 700 feet in thickness and consists primarily of interbedded sandstone, mudstone, and shale. The sandstones range from a few feet to more than 100 feet in thickness and aze generally lenticulaz in nature. Although typically fine to coarse-grained, the sandstones may locally be conglomeritic. Tertiary Wasatch Formation The Wasatch Formation of Tertiary age lies unconformably atop the Upper Cretaceous Mesaverde Formation. Rocks of the Wasatch Formation aze only exposed in the easternmost portions of the West Elk Mine coal lease azea where they cap the highest mesas, including West Flatiron in the Box Canyon permit revision area, Atop West Flatiron Mesa, the Wasatch Formation is represented by brownish-gray to reddish mudstone and its characteristic basal conglomerate of sandstone, chert, and volcanic rocks. Other Rocks and Deposits Further to the south and east, igneous intrusives of Tertiary age form the laccoliths of Mt. Gunnison and West Beckwith Peak. There is a low probability of intrusive dikes/sills within the permit azea, based on an aerial magnetic survey completed in 1997. Unconsolidated deposits of sand, gravels, and boulders (Pleistocene age) derived from the tertiary intrusives and Wasatch Formation may cover the Barren and Ohio Creek Members of the Mesaverde locally. These deposits are the result of more recent erosion and mass-gravity movements. Coal Seams and Related Strata B Seam The B Seam is the lowermost potentially mineable coal seam within the lease area. This seam constitutes a portion of the recoverable reserves and is of economic importance. Multiple rock partings and subsequent thinning of mineable B Seam coal benches in the South of Divide permit area do not allow for economic recovery of the coal. Future mine plans do not include mining the B Seam in the lease area at this time. A brief description of the geologic setting is included. The B Seam and adjacent strata gently dip to the northeast at approximately 3.5 degrees (Map 11). In the South of Divide permit revision area the strike is southeast to northwest. In the Box Canyon lease area, the strike swings to nearly east-west and the dip flattens to approximately two degrees to the north. This change of strike and lessening of the dip is significant because it reduces the concern about block glide instability over the Oliver No. 2 Mine and bedding plane failures in the Box Canyon azea. Photo mapping by Intraseazch indicated numerous flat and even some gentle south dips of surface outcrops in the Box Canyon azea. B Seam outcrops occur along the North Fork of the Gunnison River to the north and west of the mine portal and along 2.~~1-22 Revised November 2004 PRIO