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FALL 2017 SUBSIDENCE AND GEOLOGIC FIELD OBSERVATIONS <br />SOUTH OF DIVIDE AND DRY FORK MINING AREAS <br />1.0 BACKGROUND <br />This subsidence report is the second of two detailed documents on this subject to be generated <br />based on 2017 calendar year observations. These biannual reports of subsidence -related <br />observations at the West Elk Mine have occurred continuously since spring 2007 and annually <br />between 1996 and 2006. In accordance with Mountain Coal Company, LLC's (MCC) Colorado <br />Division of Reclamation, Mining and Safety (CDRMS) permit, these subsidence reports are to be <br />submitted by April 30 (for preceding fall monitoring) and September 30 (for preceding spring <br />monitoring). <br />Prior field observations and experience in the West Elk Mine area over the last twenty-two years 1 <br />(1996 to 2017 inclusive) indicate that subsidence -related features (cracks and bulges) are most <br />visible on roads, well pads, and trails, where the ground is more compact and free of brush. These <br />areas have been, and will continue to be, the focus of the biannual observations to most efficiently <br />obtain subsidence information. Other subsidence features such as rockfalls and landslides are <br />generally observable from overview locations along roads or on well pads and have been, and will <br />continue to be, noted when they occur. <br />Fall 2017 subsidence observations were performed on October 6, 2017, in the South of Divide <br />(SOD) and Dry Fork mining areas with specific focus on the most recently mined longwall panels <br />(i.e., Longwall Panels E5, E6, and E7). As a result, the previously established traverse names have <br />been changed and will likely change with each successive report. Observations associated with E - <br />seam longwall mining of Panels E 1 through E4 (mined and subsided more than two years previous) <br />can be found in reports prior to 2016. Observations of the Apache Rocks and Box Canyon B - <br />seam mining areas are covered in reports prior to 2013. <br />' Annual subsidence and geologic hazard reports are kept at Mountain Coal Company, LLC, and at the Colorado <br />Division of Reclamation, Mining and Safety, as well as exhibits to the permit document (Exhibits 60, 60A, 60B, <br />60C, 60D and 60E). <br />831-032.799 Wright Water Engineers, Inc. Page 3 <br />February 2018 <br />