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Subsidence Evaluation for the <br />Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 41 <br /> <br />831-032.923 Wright Water Engineers, Inc. <br />December 2021 <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.