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Appeal Deciding Officer <br />10 <br />coal annually (Section 3.1 and Appendix M, North Fork Coal FEIS, Tab 4). This section of the <br />FEIS identifies the permitted mining processes at Oxbow Mine and the emission increases <br />included in the modeling (Section 3.1.3). <br />Methane emissions in working mines arise when methane is released as a direct result of the <br />physical process of coal extraction and from the collapse of the surrounding rock strata after a <br />section of the coal seam has been mined and the artificial roof and wall supports are removed as <br />mining progresses to another section. The debris resulting from the collapse is known as gob and <br />also releases methane or `gob gas' into the mine. <br />All aspects of the atmosphere in underground mines, including methane concentration and <br />removal, are regulated by the Mine Safety Health Administration (MSHA) under the Federal <br />Mine Safety & Health Act. The specific regulations cover such subjects as ventilation plans, <br />permissible methane limits, fire prevention, drilling, and electricity, use of equipment, personal <br />protection, and control of air quality. <br />Mining underground coal deposits releases large quantities of methane into the mine workings, <br />which must be removed by diluting the methane with large volumes of air. In -mine methane <br />concentrations must be maintained well below the lower explosive limit, so ventilation air <br />exhausts at mines carry only very dilute concentrations of methane (typically below 1% and <br />often below 0.5 %). Because of mine safety concerns, there are no federal or state regulations <br />which control or prohibit the venting of mine methane into the atmosphere Efforts to put the gas <br />to any beneficial use, or to reduce its impact on the environment, are strictly voluntary y the <br />mine operator <br />The ventilation systems move the diluted methane out of the working areas of the mine into <br />shafts leading to the surface. The methane removed from working mines via this technique is <br />known as Ventilation Air Methane (VAM). The VAM is released through the ventilation shafts <br />and can then be destroyed or captured for utilization rather than allowing it to be released <br />directly into the atmosphere, as may have occurred in the past. VAM has the lowest <br />concentration levels of all forms of recoverable methane from coal seams because of its high <br />exposure to air; often displaying levels of 0.05 -0.8 %. <br />Many mines also drain methane by drilling boreholes into the coal seams and surrounding strata <br />in advance of mining. The mines then pipe this methane to the surface. To pre -empt the release <br />of gob gas from post mining collapse, it is possible for vertical gob wells to be drilled directly <br />into the coal seam's surrounding strata before mining activities pass through that section. These <br />pre- drilled wells can then remove the gob gas once the collapse takes place, thus avoiding the <br />release of methane directly into the mine. The gob gas can then be destroyed or captured for <br />utilization via the wells, rather than allowing it to be released directly into the atmosphere. As <br />gob gas is exposed to significantly lower volumes of air than VAM, it displays much higher <br />methane concentration levels - typically between 35 -75 %. <br />Discussion: <br />