2011-01-13_PERMIT FILE - C1981038A (6)

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2.05 APPLICATION FOR PERMIT FOR SURFACE OR UNDERGROUND MINING ACTIVITIES - MINIMUM REQUIREMENTS FOR OPERATION AND RECLAMATION PLANS. • Panel designs for specific development geometries and mining heights vary within these buffer zones and are optimized for MER, however the minimum safety factor criteria for all panels developed within these buffer zones remains constant at 2.0. Secondary extraction or retreat mining is limited to the recovery of floor coal within previously developed entries. All development entries are roof - bolted in accordance with the approved roof control plan. 600 to 800 feet of overburden Protective pillars in these buffer zones are designed to provide safety factors in excess of 1.5 using the Wilson pillar design method. (See Pillar Stability Calculations in Volume 2) ' Panel designs for specific development geometries and mining heights vary within these buffer zones and are optimized for MER, however the minimum safety factor criteria for all panels developed within these buffer zones remains constant at 1.5. • Secondary extraction or retreat mining is limited to the recovery of floor coal within previously developed entries. All development entries are roof - bolted in accordance with the approved roof control plan. The remaining permanent protective pillars have a safety factor adequate for permanent support, but a smaller safety factor than the pillars directly under the Renewable Resource Lands (refer to Pillar Stability Calculations, Volume 2). Because of this, pillar yielding will occur at the distance greatest from the Renewable Resource Lands should unexpected and excessive loading occur. The Operator and its assigns indemnifies the United States against any liability for damage to life or property arising from the undermining of Stevens Gulch Road as the result of Technical Revision 17 and 19 to the mining permit application. Mine Layout and Design Both the East and West mines extracted coal from what was thought to be the "D" Seam. The Bowie No. 2 Mine refers to this seam as the "B" Seam. The mine was layed out in a series of main, submain and panel entries. The orientation and distance of the workings were designed for maximum economic recovery and mining efficiency with respect to the in -situ features such as faults and the strike and dip of the coal seam. Overall design also maximized the efficiency of the mine ventilation system. • Specific pillar and section dimensions were engineered to provide adequate ground support and pillar recovery efficiency. PR -4 -2- 06/10 1/13/t/