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Methane : The coal seams in Coal Basin rank among <br /> the most gassy seams in- the world in terms of <br /> cubic feet of methane liberated per ton of <br /> coal mined . <br /> Outbursts : At depths greater than 1, 500 feet high- <br /> intensity stress relief can occur in develop- <br /> ments in virgin coal that still contains all <br /> of the inherent methane. Methane liberation <br /> during an outburst is extremely high. <br /> Bounces : Stress adjustments in pillars and around <br /> mine openings are common during mining and <br /> are normally accompanied by bottom heaving . <br /> The heaving tends to restrict airways , <br /> requiring periodic correction. <br /> Friable The coal is friable (soft) . Hardgrove <br /> Coal : Index is + 108 . Additional rock dust and <br /> dust suppression is needed in the underground <br /> operations because considerable dust is <br /> generated . <br /> The Middle Bed lies stratigraphically 450 ` <br /> • (more or less) above the B Bed . A heavy sandstone member , <br /> the Middle Sandstone, lies at the top of the interburden <br /> measure, immediately beneath the Middle bed. <br /> Coal quality of the Middle bed is similar to <br /> that of the B bed , although content of volatile matter is <br /> greater . Coal qualities of the Middle bed average : <br /> Fixed Carbon 64 . 8 percent <br /> Volatile Matter 26. 0 <br /> Ash 9. 2 <br /> Sulfur 0. 59 <br /> Btu 14, 000+ <br /> Moisture free <br /> Extensive underground mining development in <br /> the Middle bed over mined-out areas in the B bed has thus <br /> far indicated that interaction between the beds is minimal _ <br /> • <br /> 17 <br />