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West E1kMine <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). According to Emmons, methane still is likely to be present in <br />the roadbed. <br />Water and Methane Potential in the BSeam-Oliver No. 2 Mine 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 azea 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 of <br />5 to 10 cubic feet per minute (5-10 cfin) 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. 2 Mine azea. Potential Impact <br />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)(BJJ, <br />the moisture content of the caved and downwarped rocks controls the amount of subsidence that can <br />be expected. In mining areas where water might be encountered in an azea 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-extraction 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. No water was encountered in shafts 1, 2, and 3 in E Seam or layers above <br />the E Seam. No water has been encountered during E Seam development. No water has been <br />encountered in drilling the Methane Drainage Wells through E Seam which are north of and down- <br />dip from the South of Divide Area. However, because water has been identified in E Seam <br />monitoring wells in the SOD area, water maybe encountered as a result of E Seam mining. <br />The water in the E Seam wells is described at 2.04 Groundwater Quality and Characteristics of the <br />E Seam. Monitoring' Wells and Table 7. A summary of water characteristics of groundwater that <br />could be encountered is found in Exhibit 71 Appendix G which details the quantity and quality <br />anticipated to be encountered. Basically, the water quality of the E Seam waters aze similaz to the B <br />Seam waters. For instance, wells in SOM 3E and SOM 23-H-2 exhibit sodium bicarbonate type <br />water with a slightly alkaline PH, (8.2 to 8.4) moderately high TDS (1330 to 1,540 mg/L). <br />Modern Methods of Ventilation <br />Under modem methods of ventilation, high capacity fans exhaust return 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 />2.05-143 Revised Jane 2005 PR/0, Rev. March 2006; May 1006 PR/0 <br />