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Subsidence Evaluation for the <br /> Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 41 <br /> 14.0 SUBSIDENCE CONTROL PLAN <br /> Longwall mining has been and is being used for extraction of the B-seam and E-seam in the West <br /> Elk Mine. Although longwall mining may initially induce more caving and fracturing of the roof <br /> rocks as compared to the room-and-pillar method due to the complete removal of coal in the panel, <br /> it offers the advantages of maximizing resource recovery. The longwall method also causes more <br /> uniform subsidence (full extraction of panel) and causes equilibrium conditions to be reached in a <br /> shorter period of time (i.e., there is no additional, lingering pillar crushing in panels). <br /> 14.1 Anticipated Effects <br /> Long-term impacts on the surface are predicted to be minimal above the longwall panels. The few <br /> surface cracks over the mined longwall 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 rigid <br /> chain or barrier pillars or mine boundaries may remain open for many years where permanent <br /> tensile strains remain after longwall mining is completed. However, several hundred feet of rock <br /> will typically exist between any mine-induced surface fractures and the upper part of any longwall <br /> mine-induced fractures above the caved zone in the longwall mining panels. Therefore, from a <br /> practical standpoint, no interconnection between the surface fractures and the longwall mine <br /> 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 <br /> interconnection between adjacent sandstones. However,even under these conditions,the fractures <br /> would not extend through the claystones and shales present in the overburden. <br /> Minnesota Reservoir is located well outside of the area of longwall mining influence of the <br /> projected B-seam and E-seam panels for the Southern Panels, Apache Rocks West, and Sunset <br /> Trail mining areas and, therefore, will not be affected by longwall mining. <br /> 14.2 Reduction Measures (Underground) <br /> Underground measures that may be taken to reduce surface strains above the longwall panel chain <br /> pillars could include: (1) designing the pillars to yield and crush after mining (thus minimizing <br /> humps in the subsidence profile), and/or (2) planning a rapid and uniform longwall mining rate. <br /> Any plans to reduce chain pillar dimensions in order to reduce subsidence impacts must,of course, <br /> be balanced with health and safety conditions in the mine. Plans for a rapid and uniform mining <br /> rate are affected by market demands (or lack thereof) for a constant, high volume of coal. <br /> 14.3 Development Mining <br /> Although subsidence is primarily a result of the secondary recovery of coal from a longwall coal <br /> panel,subsidence-type features may occur when developing main entries/roadways under shallow, <br /> unconsolidated and saturated cover. Such was the case in October 2020 when developing main <br /> entries under South Prong Creek. To avoid similar issues in the future, MCC has performed an <br /> analysis of the minimum depth of cover required for development mining in the West Elk Mine to <br /> avoid the potential for this type of surface subsidence impacts. WWE has included this Technical <br /> Memo as Appendix A to this exhibit. <br /> 831-032.912 Wright Water Engineers, Inc. <br /> December 2020 <br />