2011-01-28_REVISION - C1980007 (2)

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West Elk Mine State-of-the-art longwall mining technology will continue to be utilized for extraction of the B Seam and for the extraction of the E Seam in the permit area. Although longwall mining may initially induce more caving and fracturing of the roof rocks, as compared to the room-and-pillar method, it offers the advantages of maximizing resource recovery; more complete subsidence; equilibrium conditions occurring in a shorter period of time; more uniform and predictable parameters necessary for the evaluation of probable hydrologic consequences; and in general, fewer and less significant adverse hydrologic impacts than room-and-pillar mining. A small portion of Deep Creek Ditch (about 250 feet) lies over the southern gate pillars near the end of E- seam longwall panel E5. The base of the ditch at this location is primarily shale. With this portion of ditch being located over the longwall gateroad pillars, impacts from subsidence will be reduced. E-seam longwall panel E6 may also be extended under Deep Creek Ditch in the Projected Potential Mining Area (see Map 51). As mining approaches the ditch, the pre-mining condition of the ditch will be documented in a pre-subsidence survey. This survey will be added to the permit application in the semi-annual subsidence reports. Before, during and after mining, the amount of the ditch that is subsided will be determined by surveying reflector stations in the ditch, as set forth in Section 2.05.6(6(0(iii)(C). In addition to the surveying, changes in the ditch caused by subsidence will be detected by visually inspecting the ditch on a weekly basis while active longwall mining is within 1000 feet of the ditch. MCC will repair any mining-caused damage found during the monitoring or during visual inspections, in accordance with the agreement between MCC and the Minnesota Canal and Reservoir Company. If mining activity disrupts flow in the ditch, MCC will apply methods set out in the subsidence mitigation plan or injured parties will be compensated with water resources that are owned by MCC. These are identified in Exhibit 52. Anticipated Effects - 2. 05.6 (6)(n(iii)(A) Long-term impacts on the ground surface above the longwall panels are predicted to be minimal. The few surface cracks over the mining panels that may occur are expected to close once the longwall face moves past the surface area of influence. Surface cracks present above the chain or barrier pillars or mine boundaries may remain open where permanent tensile strains remain after mining is completed. However, at least several hundred feet of unfractured rock will typically exist between any mine-induced surface fractures and the upper part of any mine-induced fractures above the caved zone in the mining panels. Therefore, from a practical standpoint, no interconnection between the surface fractures and the mine workings is anticipated. Again, under a worst case scenario, if a surface fracture were to occur concurrently within an area controlled by faults or bedrock lineaments, there could be interconnection between adjacent sandstones. However, even under these conditions, the fractures would most likely not extend through the claystones and shales present in the overburden. Monument Dam and Minnesota Reservoir are located outside of the angle of mining influence of the nine projected panels (panels E 1 through E9) for the South of Divide mining area (see Map 51). The northwest corner of panel E9, which is nearest to the reservoir, is located 800 feet away. The angle of draw to this nearest area of mining is 69°. The angle is much greater than the maximum of 17° predicted for E-seam mining (see Exhibit 60E). This means that Minnesota Reservoir will not be affected by longwall mining in projected panel E9. Reduction Measures (Under round) - 2.05.6 (6)O i)(B)(I-III) Underground measures that may be taken to reduce surface strains above the chain pillars could include, but are not limited to; (1) Designing the pillars to yield and crush after mining (thus minimizing humps in the subsidence profile), and/or (2) Planning a rapid and uniform mining rate. Any plans in order to reduce chain pillar dimensions to reduce subsidence impacts must, of course, be balanced with health and safety conditions in the mine. Plans for a rapid and uniform mining rate are affected by market demands 2.05-169 Rev. 06105- PRIO, 03106- PRIG, 05106- PRIG, 111060• TR107, 04107- TRIM, 09107- PR12. 02108- PR12, 11/10. TRI24