Laserfiche WebLink
West Elk Mine <br />U <br />Methane Concentrations in tke OliverNo. 2 PortalArea <br />Methane was also encountered in the portal area of the Oliver No. 2 Mine during exploration <br />drilling for the State Highway 133 roadbed. Boyd Emmons, State Coal Mine Inspector, stopped <br />drilling in one hole north of the Oliver No. 2 portal when 100 percent methane was detected. It was <br />14 to 15 days before CDOT could remove steel from one hole (Boyd Emmons, Oral <br />Communication, November 6, 1996). Acwrding to Emmons, methane still is likely to be present in <br />the roadbed. <br />Water and Methane Potential in the BSean:--Oliver No. 2 Mine Area <br />Based on the history of mining the Oliver No. 2, water and methane aiso 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 neaz 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 neaz the mouth of the unnamed, drainage west of Box Canyon, neaz the <br />haulageway of the Oliver No. 2 Mine, was observed to exhaust gas and water vapor in a volume <br />• of 5 to 10 cubic feet per minute (5-10 cfm) at atmospheric pressure during field studies in <br />October 1996. The shut-off pressure was estimated to be 20 psi. The source of the methane and <br />water vapor was reported to be mainly from the A and B Seams. This would indicate that water <br />and methane may be encountered during mining of the B Seam in the Oliver No. 2 Mine area. <br />Potential Impact of Water on Subsidence in Wet Mining Areas <br />As discussed in a previous section, Geologic Factors Influencing Subsidence (2.05.6 (6)(e)(i)(B)), <br />the moisture content of the caved and downwazped rocks controls the amount of subsidence that can <br />be expected. In mining azeas where water might be encountered in an area equal to, or greater than, <br />the width of the proposed longwall panels, maximum vertical displacement may be expected to <br />approach 0.8 times the coal-extracfion thickness. Based on available information, the E Seam <br />overburden in the South of Divide mining area is not expected to contain significant volumes of <br />water within the strata. <br />Potential Impacts of Subsidence and Mine-Induced Seismic Activity on Landslides and <br />Rockfalls <br />Landslides <br />Box Canyon Mining Area - In October 1496, large, composite landslides with numerous scarps <br />were observed between the unnamed drainage west of Box Canyon and Box Canyon and also to the <br />east of Box Canyon. As discussed in Section 2.04.6, the slides are compartmented into essentially <br />separate slides by competent sandstone ledges. Grabens, sag ponds (complete with small wetlands), <br />2.05-129 RevisedNavember 2004 PRIO <br />