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<br />1.0 GENERAL <br />• Seneca Coal Company (SCC) has previously auger mined at Seneca II, Yoast, and II-W. Augering <br />occurred in the mid- to ]ate 1980's at Seneca II and from June 2000 to December 2001 at Yoast and II <br />-W. Seneca proposes highwall mining at Yoast shown on Exhibit 12-1A, Operations Plan Mining. <br />Since the final highwall is the economic limit at which the dragline can uncover coal, other coal <br />extraction methodology has to be utilized. <br />Potentially recoverable reserves under and beyond the highwall would be lost if alternative recovery <br />methods are not implemented. SCC has used augenng in the past and experienced an unacceptably <br />low recovery rate, therefore SCC is proposing to employ a highwall miner in place of the auger. The <br />highwall miner is expected to have a higher in-place recovery rate and deeper seam penetration than <br />experienced with the auger. It is proposed to highwall mine both the ~~/adge and Wolf Creek seams. <br />Per regulation 4.23.2(1) (there are no highwall miner regulations, therefore auger regulations will be <br />followed) any auger (lghwall miner) mining associated with surface mining activities shall be <br />conducted to maximize recoverability of the coal reserves remaining after the surface mining activities <br />are completed. Therefore, highwall mining operations shall leave areas of undisturbed coal to provide <br />access for removal of those reserves by future underground mining activities. These undisturbed azeas <br />of coal shall be a minimum of 250 feet wide at any point between each group of highwall miner <br />openings to the full depth of the highwall miner hole. They also are to be no more than 2,500 feet <br />apart measured from the center of one section to the center of the next section. As shown on Exhibit <br />12-1A, Operations Plan Mining, SCC is proposing to highwall mine these four areas, with existing <br />pillars of unmined coal being left in place between each highwall mined area. SCC and Peabody <br />Holding Company, Inc. have looked at underground mining at the Yoast Mine and the entire <br />• surrounding area and have deternvr~ed that these proposed highwall miner areas would not be an ideal <br />location for a future underground portal. There are other areas that would be better suited for <br />potential portal locations. <br />Rule 4.23.2 (2) is being complied with already, since there are no abandoned or active underground <br />workings within 500 feet of the proposed auger (highwall miner) operations. <br />In the interest of contemporaneous reclamation for Rule 4.23.2(3), auger (highwall miner) mining will <br />be initiated and completed as soon as possible after the surface coal has been removed. The highwall <br />miner operations will be following the dragline stripping operations along the entire length of the Fnal <br />highwalls as shown on Exhibit 12-1A, Operations Plan Mining. <br />For Rules 4.23.2(4) and 4.23.2(5), special plugging procedures are not proposed for this set of auger <br />(highwall miner) holes. The holes will be plugged by backfilling operations as a normal pazt of the <br />highwall miner and reclamation operations. Drainage from these holes will not be a problem as <br />discussed in the Hydrology Section. <br />For Rule 4?3.2(6) (d), subsidence resulting from auger (highwall miner) mining to any powerlines, <br />buildings, or other surface facilities is not predicted occur based on the engineering design analysis <br />conducted by SCC. If subsidence does occur there no structures that will be highwall mined <br />underneath. If cracks do occur on the surface SCC will repair them. As per accordance with the <br />MSHA ground control plan, SCC will design pillaz strength with a minimum safety factor of 1.5. <br />Finally, Rule 4.23.2(7), requires that auger (highwall miner) mining shall be conducted in accordance <br />• with approved backfdling and grading requirements of Rule 4.14. <br />72-2-1 'IR-21 <br />