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<br />reserves Western Fuels stresses that maximizing the resource recovery cannot be <br />overemphasized. <br />The average production from longxall faces is about 800 tons per shift. Many <br />new faces are exceeding a thousand tons without difficulty and nex equipment and <br />technology promises to raise future production eves higher. Because longwall <br />mining is believed to be the only true continuous mining system the tonnage <br />mined by this method is expected to climb during the coming years. Western <br />Fuels' Deserado Mine has the reserves and the coal blocks suitable for this high <br />recovery, high production technology. <br />Longwell mining has a better safety record than continous mining. The danger of <br />roof falls has been removed. The roof supports are set In a atra±ghL line on <br />the face xith skin-to-skin contact. The safest place in the mine is directly <br />under the steel canopies of the self-advancing supports. <br />Longwell mining has two mayor disadvantages. The initial capital investment is <br />extremely high and the system is totally interdependent. The total cost of a <br />longxall system can exceed 10 million dollars. In longxall mining, there are no <br />alternatives, no spare sections, no spare equipment. If any one element shuts <br />doxn, the entire system is down. <br />Western Fuels has designed its mining plan to permit the highest resource <br />recovery Sn the most coat-effective and safe manner. • <br />Longwell panels are planned within the permit boundary wherever it is <br />geologically possible. All other areas will be mined by the more flexible room <br />and pillar mining. <br />There are three factors within the Deserado Mine permit area which prohibits the <br />use of longwall mining: <br />1. Areas where the seam height is less than five feet. <br />2. Mess where the overburden is less than 300 feet. <br />3. Areas xhere the thickness of the interburden <br />between the D Seam and the E Seam above is less <br />than seven feet. <br />1. Five feet has been established as the minimum seam height for longwall <br />mining. This is the height at which the production cost per ton using <br />continuous :ainers becomes more favorable. Longwell mining of coal less <br />than this height would require specialized equipment. The standard <br />supports and equipment used in other areas of the mine would not be <br />applicable. Low-seam longwall mining is more costly and less <br />productive. <br />2. Areas in which the overburden over the extracted seam approaches zero <br />are critical to longwall system. The countrty rock in these areas are <br />usually weathered and fractured because of its proximity to the outcrop. <br />The roof rock can break up right up to the surface placing the total <br />weight on tine longwall roof supports and gate entires. There are no <br />calculable values for the minimum overburden over longwalls as this for <br />the minimum overburden over longwalls as this depends on a wide range of <br />J <br />1050 12 <br />