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West Elk Mine mass above them. The material above the plane of weakness then slides as a block (block glide; decollement-type movement). Block Glide Potential in the Oliver No. 2 Mine Area The Oliver No. 2 Mine was an E/D Seam coal mine operated east of Sylvester Gulch during the 1940s and eazly 1950s (See Map 5). Based on information contained in the Oliver No. 2 Mine closure report dated October 1953, water-and methane-filled fractures within the mine E/DO Seam were encountered in the floor of the Oliver No. 2 Mine, (Both water and methane were reportedly under high pressure). The fractures (with a reported trend N77°E) were encountered during pillaz development before any fractures produced by floor-heave would likely have occurred. For block glide to occur, the sheaz strength must be less than the sheaz stress generated by overburden load and any unbalanced lateral stresses. At the very gentle dip of 2.2 to 3.2 degrees, a high pore-fluid pressure would be necessary to cause the sheaz strength to be less than the shear stress. It is very unlikely that sheaz strength along bedding planes in the coal seam (or seams) mined at Oliver No. 2 could be reduced to this extent because: 1. There is no high pre-fluid pressure; the water can drain out the Oliver No. 2 Mine portals even though seals of cinder blocks, arranged in double rows, were constructed 700 to 800 feet south of the portal azea. This is evidenced by the lack of spring development in the overburden. 2. The dip of bedding is 2 to 3 degrees-much less than the 8 to 17 degree angle of friction for any clays that might be present in the coal-bearing rocks of the Mesaverde Formation. 3. No indication of block glide has been observed in the 42 years since the mine was closed. 4. All of the Oliver No. 2 Mine workings aze outside the angle of draw of planned B Seam mining,with the exception of the fast Box Canyon panel. 5. State Geologists from most coal-producing states were wntacted regarding the lmown occurrence of any block glide in such gently-dipping rocks as in the Oliver No. 2 Mine azea. Not one could recall an occurrence of block glide, including those from eastern states where coal seams typically overly a soft underelay making block glide more likely (John Rold, Written Communication, November 15, 1996). Block Glide Potential Due to Mining in the B Seam in the Oliver No. 2 Mine Area Block glide due to MCC mining of the B-Seam will not occur in bedrock beneath the coal wne mined at the Oliver No. 2 Mine. This is based on two factors: (1) these rocks oceur beneath the • North Fork valley and aze, therefore, laterally constrained; and (2) the B Seam in this area has a dip angle of 2.6 percent which is less than that of the E/DO Seam. 2.05-l15 RevisedN°vember 2004 PRIO