2024-06-25_PERMIT FILE - C1980007A (4)

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West Elk Mine 2.05-121 Rev. 06/05- PR10, 03/06- PR10, 05/06- PR10, 11/060- TR107, 04/07- TR108, 09/07- PR12, 02/08- PR12; 11/10- MR372; 10/20- MR-452; 12/20- TR149; 12/21- TR150, 1/24-TR152 A small portion of Deep Creek Ditch may be undermined by E seam and B Seam longwall panels. (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) (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 per its adjudicated water augmentation plan. These water resources are identified in Exhibit 52. Anticipated Effects – 2.05.6 (6)(f)(iii)(A) Long-term impacts on the surface are predicted to be minimal above the mined longwall panels. 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 eleven longwall panels (panels LWE1-8, SST1-4, LWE10-12 and LWE15-17) within the South of Divide mining area (see Map 51). The northern portions of panels LWE16 and LWE17, which are nearest to the reservoir, are located several hundred feet away. The angle of draw to this nearest area of mining is 79º. The angle is much greater than the maximum of 19º projected for the SOD mining area. This means that Minnesota Reservoir will not be affected by longwall mining in projected panels LWE16 and LWE17. Reduction Measures (Underground) - 2.05.6 (6)(f)(iii)(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 (or lack there of) for constant, high volumes of coal. MCC will notify CDRMS if plans that may affect the subsidence profile are implemented.