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2.05.2 <br />Cyprus Orchard Valley Coal Corporation and its assigns shall indemnify the United States against <br />any liability for damage to life or property arising from the undermining of the Steven's Gulch <br />Road as proposed under technical revision 19 (Panel C) for Permit No. C-81-038. <br />The remaining permanent protective pillars have a safety factor adequate for permanent support, <br />but a smaller safety factor than the pillrs directly under the Renewable Resource Lands (refer to <br />Pillar Stability Calculations, Volume 2). This indicates yielding would occur at the distance <br />greatest from the Renewable Resource Lands if unexpected excessive loading should occur. <br />The "D" coal seam is developed by a series of main, sub-main, and panel entries. The orientation <br />and distance of the workings are designed for maximum recovery and mining efficiency with <br />respect to the in-situ features such as faults. Overall design also maximizes the efficiency of the <br />mine ventilation system. Specific pillar and section dimensions are engineered to provide <br />adequate ground support and pillar recovery efficiency. <br />Room and pillar panels are developed off the main and sub-main entries with barrier pillars left for <br />protection. Pillar recovery of all workings and barrier pillars will proceed to the extent that safe <br />mining conditions allow. Where hazardous conditions preclude total extraction, the pillars will be <br />partially removed, which keeps the cave-Gne at a greater distance from the active work area. The <br />• safety advantage of partial pillaring is the temporary delay of planned roof falls. <br />Ventilation <br />The current and planned ventilation system use exhausting ventilation by means of large fans on <br />the surface. Requirements to minimize the ventilation pressure to control spontaneous <br />combustion, limited number of portals, and length of mains and sub-mains ultimately constrains <br />production capacity. Muting is performed in districts which can be sealed to m;n;m;~e the size of <br />mine workings that aze ventilated. The West Mme portals and ventilation shaft will be required <br />through the life of the mine for ventilation to the East Mine. Computer modeling is used to <br />optimize ventilation planning. Using this information, the location of the proposed intake shafts <br />aze shown on Map 2-5. The locations of the current West Mine ventilation shaft is shown on <br />Map 8-7. The MSHA ventilation plan is provided in Volume 2, Geology and Mine Planning <br />appendices. <br />Roof Control <br />Acceptable roof conditions are established when 3-foot of top coal is left as a beam to support the <br />mudstones found immediately above the coal roof. Roof bolts are used to support the roof, along <br />with timbers, cribs and other devices where needed. <br />The mudstone is unacceptable as the immediate roof. It is thinly laminated clay and silt which is <br />commonly rooted and vertically fractured by the dense cleat system and sGckensides. Used as <br />immediate roof, this material spans out in large chunks before roof bolts are installed. Once <br />exposed, the mudstone deteriorates as air and water m the mine atmosphere cause it to air slack. <br />TR-032 - 3 - 9199 <br />2/ S/o0 <br />