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West Elk Mine <br />Antic i ated ffLects — 2.05.6 L6 iii A <br />Long-term impacts on the surface are predicted to be minimal above the mined longwall panels. <br />The few surface cracks over the mining panels that may occur are expected to close once the <br />longwall face moves past the surface area of influence. Surface cracks present above the chain <br />or barrier pillars or mine boundaries may remain open where permanent tensile strains remain <br />after mining is completed. However, at least several hundred feet of unfractured rock will <br />typically exist between any mine -induced surface fractures and the upper part of any mine - <br />induced fractures above the caved zone in the mining panels. Therefore, from a practical <br />standpoint, no interconnection between the surface fractures and the mine workings is <br />anticipated. Again, under a worst case scenario, if a surface fracture were to occur concurrently <br />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 <br />likely not 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 <br />the eleven longwall panels (panels LWE1-8, SST1-4, LWE10-12 and LWE15-17) within the <br />South of Divide mining area (see Map 51). The northern portions of panels LWE16 and <br />LWE17, which are nearest to the reservoir. The minimum horizontal distance between the <br />Reservoir and the projected longwall mining is 1600 feet, which occurs in the north west corner <br />of Panel 17. Assuming the most conservative angle of draw estimate of 19 degrees and a <br />conservative depth of cover of 350 feet, the limit of possible subsidence is 120 feet, well below <br />the minimum distance of 1600 feet. The angle of draw to this nearest area of mining is 79°. <br />Reduction Measures (Underground - 2.05.6 (6} O(iii}(B}(I-fIJ <br />Underground measures that may be taken to reduce surface strains above the chain pillars could <br />include, but are 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 pillar 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 are affected by market demands (or lack there of) for constant, high volumes of coal. <br />MCC will notify CDRMS if plans that may affect the subsidence profile are implemented. <br />As discussed in previously in section 2.05.6, Wright Water Engineers has completed detailed <br />subsidence modelling and evaluations from longwall mining in the SOD, Southern Panels, Apache <br />Rocks West, Dry Fork and Sunset Trail mining areas and provided recommendations for longwall <br />mining heights and cover depths. MCC will adhere those recommendations as detailed in Exhibit <br />60E, including not longwall mining where actual overburden depths are less than 250'. E seam <br />overburden depths are shown on Map 19 and were based on surface topographic surveys <br />compared to top of seam elevations derived from nearby drillhole data. MCC will continue to <br />survey actual roof elevations in the mine as each longwall panel is developed and adjust the <br />panel length as necessary to ensure that no longwall mining occurs where actual overburden <br />depths are less than 250'. <br />2, 05-121 Rer. 06/05- PR10, 03./06- PRIG, 05/06- PRIO, 111060- TRI07, 04/07- TRI081 09/07- PR12, 02/08- PR12; 11/10- A4R372; 10/20- AIR-452; <br />12/20- TR1491 1221- TRI50 <br />