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Subsidence Evaluation for the <br /> Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 4 <br /> overburden above panels SS 1 to SS4 ranges in thickness from approximately 280 feet up to 1,300 <br /> feet. <br /> All longwall panels are planned to be separated by two or three rows of chain pillars. The pillars <br /> on both the headgate and tailgate sides of the panels are typically on centers of about 125 feet wide <br /> by 200 feet long. The headgate for the adjacent panel becomes the tailgate panel on the subsequent <br /> panel. These mine plans and pillar designs may change as mining experience, geological- <br /> geotechnical conditions, and/or mine operational procedures dictate. This exhibit focuses on <br /> subsidence projections over the mined longwall panels. <br /> 831-032.912 Wright Water Engineers, Inc. <br /> December 2020 <br />