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Subsidence Evaluation for the <br /> Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 43 <br /> 4. The South Prong channel in the Sunset Trail mining area overlays panel SS4, where the <br /> overburden is projected to be roughly 300 feet at the western end of the panel. The potential <br /> for hydraulic connection between a surface crack and fractures from the mine are negligible <br /> when overburden is 300 feet or more. If actual conditions show the overburden to be less <br /> than 300 feet, then the mining height should be reduced to continue to minimize the risk of <br /> a hydraulic connection forming. <br /> 5. Mining impacts on rockfalls were not observed during annual subsidence observations in <br /> the Apache Rocks and Box Canyon mining areas over six years (1999 to 2004 inclusive), <br /> in areas where the estimated rockfall potential was moderate to high. The highest estimated <br /> rockfall potential is classified as moderate to high in the Southern Panels mining area, and <br /> many of these are located in areas where no mining is currently planned. Consequently, <br /> the natural rockfall process is not expected to be significantly accelerated by longwall <br /> mining. <br /> 6. The landslides that are located north and south of Minnesota Reservoir and above the <br /> northern part of E-seam longwall panel E9, are not expected to be noticeably impacted by <br /> subsidence or seismic activity caused by longwall mining. Based on field observations, <br /> the major finding is that landslide movement occurs in response to moisture and ground <br /> saturation,and is not noticeably affected by subsidence or any mine-related seismic activity <br /> caused by longwall mining beneath or near the landslides. <br /> 7. There is no historical record from annual observations in the West Elk Mine area regarding <br /> effects of mining on springs and local water-bearing zones, with sources in either surficial <br /> material or bedrock. These observations are documented in the Annual Hydrology <br /> Reports. <br /> 8. Small cracks have occurred on the hard, compacted access roads following longwall <br /> mining. However, these cracks have never affected use of the roads. <br /> 831-032.912 Wright Water Engineers, Inc. <br /> December 2020 <br />