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West Elk Mine <br />• and-pillaz method due to the complete removal of coal in the panel, it offers the advantages of <br />maximizing resource recovery. The longwall method also causes more uniform subsidence (full <br />extraction of panel) and causes equilibrium conditions to be reached in a shorter period of time (i.e., <br />there is no additional, lingering pillar crushing in panels). <br />Preventive Measures - 2.05.6(6)(n(iii) <br />State-of--the-art longwall mining technology will continue to be utilized for extraction of the B <br />Seam and for the extraction of the E Seam in the permit azea. Although longwall mining may <br />initially induce more caving and fracturing of the roof rocks, as compared to the room-and-pillaz <br />method, it offers the advantages of maximizing resource recovery; more complete subsidence; <br />equilibrium conditions occurring in a shorter period of time; more uniform and predictable <br />parameters necessary for the evaluation of probable hydrologic consequences; and in general, <br />fewer and less significant adverse hydrologic impacts than room-and-pillaz mining. <br />Anticipated Effects - 2.05.6 (6)(fl(iii)(A) <br />Long-term impacts on the surface are predicted to be minimal above the longwall panels. The <br />few surface cracks over the mining panels that may occur are expected to close once the longwall <br />face moves past the surface azea of influence. Surface cracks present above the chain or barrier <br />pillars or mine boundaries may remain open where permanent tensile strains remain after mining <br />is completed. However, at least several hundred feet of unfractured rock will typically exist <br />• between any mine-induced surface fractures and the upper part of any mine-induced fractures <br />above the caved zone in the mining panels. Therefore, from a practical standpoint, no <br />interconnection between the surface fractures and the mine workings is anticipated. Again, <br />under a worst case scenario, if a surface fracture were to occur concurrently within an azea <br />controlled by faults or bedrock lineaments, there could be interconnection between adjacent <br />sandstones. However, even under these conditions, the fractures would most likely not extend <br />through the claystones and shales present in the overburden. <br />Minnesota Reservoir is located outside of the angle of mining influence of the nine <br />projected panels (panels El through E9) for the South of Divide mining area. The <br />northwest corner of panel E9, which is nearest to the reservoir, is located 800 feet away. <br />The angle of draw to this nearest area of mining is 69°. The angle is much greater than the <br />maximum of 20° projected for the SOD mining area. This means that Minnesota Reservoir <br />will not be affected by longwall mining in projected panel E9. <br />Reduction Measures (Under rg ound) - 2.05.6 L)(fl(iii~(B)(I-III) <br />Underground measures that may be taken to reduce surface strains above the chain pillars could <br />include, but aze not limited to; (1) Designing the pillars to yield and crush after mining (thus <br />minimizing humps in the subsidence profile), and/or (2) Planning a rapid and uniform mining <br />rate. Any plans in order to reduce chain pillaz dimensions to reduce subsidence impacts must, of <br />course, be balanced with health and safety conditions in the mine. Plans for a rapid and uniform <br />mining rate aze affected by market demands (or lack there of) for constant, high volumes of <br />. coal. MCC will notify CDMG if plans that may affect the subsidence profile are implemented. <br />1.05-146 Revised November 2004 PRIO <br />