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• Water and Methane Potential in the B-Seam-Oliver No. 2 Muse Area <br />Based on the history of mining the Oliver No. 2, water and methane also may locally be expected to <br />be encountered during the mining of the B-Seam in that area at least. Appazently most of the water <br />and methane encountered in the Oliver No. 2 Mine was present in fractures, joints, bedding planes, <br />or in permeable rocks near the coal seam mined. However, with about 250 feet of shale, siltstone, <br />and sandstone between the B-Seam and the E/DO-Seam, the extent and volume of water and <br />methane cannot be predicted without drilling. <br />One drill hole located near the mouth of the unnamed drainage iwest of Box Canyon, neaz the <br />haulageway of the Oliver No. 2 Mine, was observed to exhaust gasi and water vapor in a volume of <br />5 to 10 cubic feet per minute (5-10 cfm) at atmospheric pressure during field studies in October <br />1996. The shut-off pressure was estimated to be 20 psi. The source of the methane and water vapor <br />was reported to be mainly from the A and B-Seams. This would indicate that water and methane <br />may be encountered during mining of the B-Seam in the Oliver No. j2 Mine area. <br />Potential Impact of Water on Subsidence in West Minine Areas <br />As discussed in a previous section, Geologic Factors Influencing Subsidence, the moisture content <br />of the caved and downwarped rocks controls the amount of subsidence that can be expected. In <br />the Oliver No. 2 Mine area, and in other areas where water might ibe encountered in an area equal <br />to, or greater than, the width of the proposed longwall panels, maximum vertical displacement may <br />• be expected to approach 0.8 times the coal-extraction thickness. <br />Modern Methods of Ventilation <br />Under modern methods of ventilation, high capacity fans exhaustreturn air from the mine. This <br />procedure keeps the mine air pressure less than the outside air pressure. The mine is less likely to <br />"gas up" because methane is continually removed from fractures in this negative-pressure <br />environment. In the case of the Oliver No. 2 Mine, fresh air reportedly was blown into the mine <br />with a 4-foot squirrel-cage blower (Boyd Emmons, Oral Commuriication, November 6, 1996). In <br />this type of positive-pressure environment, the mine workings become more and more gassy if the <br />fan does not have a sufficient air-moving capacity to ventilate sudden inflows of methane. <br />Potential Impacts of Subsidence on Landslides <br />In October 1996, large, composite landslides with numerous scarps were observed between the <br />unnamed drainage west of Box Canyon and Box Canyon and also to the east of Box Canyon. As <br />discussed in Section 2.04.6, the slides are compartmented into essentially separate slides by <br />competent sandstone ledges. Grabens, sag ponds (complete wiih small wetlands), and tension <br />cracks occur between the scarps. The tension cracks could easily be confused with subsidence <br />cracks, but no mining has been done in the azea. The landslides are located in or near the northern <br />boundary of the Box Canyon permit revision area. The southern limit of the landslides is located at <br />least 650 feet north of the nearest planned longwall panel-well outside of the conservative angle of <br />• draw. ~ <br />2.05-129 March 1005PR71 <br />~ ~g.a4 <br />