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West Elk Mine <br />State-of-the-art longwall mining technology will continue to be utilized for extraction of the B Seam and <br />for the extraction of the E Seam in the permit area. Although longwall mining may initially induce more <br />caving and fracturing of the roof rocks, as compared to the room-and-pillar method, it offers the <br />advantages of maximizing resource recovery; more complete subsidence; equilibrium conditions <br />occurring in a shorter period of time; more uniform and predictable parameters necessary for the <br />evaluation of probable hydrologic consequences; and in general, fewer and less significant adverse <br />hydrologic impacts than room-and-pillar mining. <br />A small portion of Deep Creek Ditch (about 250 feet)lies over the southern gate pillars near the end of the <br />panel (see Sketch A). The base of the ditch at this location is primarily shale. With the ditch being <br />located over the gate pillars impacts from subsidence will be reduced. As mining approaches the ditch, <br />the pre-mining condition of the ditch will be documented in a pre-subsidence survey. This survey will be <br />added to the permit application in the semi-annual subsidence reports. Before, during and after mining, <br />the amount of the ditch that is subsided will be determined by surveying reflector stations in the ditch, as <br />set forth in Section 2.05.6(6) (c). In addition to the surveying, changes in the ditch caused by subsidence <br />will be detected by visually inspecting the ditch on a weekly basis while active longwall mining is within <br />1000 feet of the ditch. MCC will repair any mining-caused damage found during the monitoring or <br />during visual inspections, in accordance with the agreement between MCC and the Minnesota Canal and <br />Reservoir Company. If mining activity disrupts flow in the ditch, MCC will apply methods set out in the <br />subsidence mitigation plan or injured parties will be compensated with water resources that are owned by <br />MCC. These are identified in Exhibit 52. <br />Anticipated Effects - 2.05.6 (6)(1)(M) (A) <br />` Long-term impacts on the surface are predicted to be minimal above the longwall panels. The few <br />surface cracks over the mining panels that may occur are expected to close once the longwall face moves <br />past the surface area of influence. Surface cracks present above the chain or barrier pillars or mine <br />boundaries may remain open where pennanent tensile strains remain after mining is completed. <br />However, at least several hundred feet of unfractured rock will typically exist between any mine-induced <br />surface fractures and the upper part of any mine-induced fractures above the caved zone in the mining <br />panels. Therefore, from a practical standpoint, no interconnection between the surface fractures and the <br />mine workings is anticipated. Again, under a worst case scenario, if a surface fracture were to occur <br />concurrently within an area controlled by faults or bedrock lineaments, there could be interconnection <br />between adjacent sandstones. However, even under these conditions, the fractures would most likely not <br />extend through the claystones and shales present in the overburden. <br />Monument Dam and Minnesota Reservoir are located outside of the angle of mining influence of the nine <br />projected panels (panels E1 through E9) for the South of Divide mining area (see Map 51). The <br />northwest corner of panel E9, which is nearest to the reservoir, is located '000 feet away. The angle of <br />draw to this nearest area of mining is 69'. The angle is much greater than -ie nna. irnum of 20° projected <br />for the SOD mining area. This means that Minnesota Reservoir will not be affected by longwall mining <br />in projected panel E9. <br />Reduction Measures (iltrde,: round) - 2.0 .6 (6)(f)(0)(B)(IIII) <br />Underground measures that :nay be t'kln to reduce surface strains above the chain pillars could include, <br />but are not limited to; (1) Designing the pillars to yield and crush after mining (thus minimizing humps in <br />the subsidence profile), and/or (2) Planning a rapid and uniform mining rate. Any plans in order to <br />reduce chain pillar dimensions to reduce subsidence impacts must, of course, be balanced with health and <br />safety conditions in the mine. Plans for a rapid and uniform mining rate are affected by market demands <br />2.05-169 Revised June 2005 PRIG, Rev. Harch 2006.• Ala), 2006 PRIG, Nov. 2006TR107,Apri1 2007TR108;Sep. 2007PR12; Feb. 2008 PR-12