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Fall 2019 Subsidence and Geologic Field Observations <br /> Southern Panels Mining Area <br /> 2.0 GENERAL SUBSIDENCE OBSERVATION AND REPORTING <br /> Based on field observations between 1996 and fall 2019, the effects of longwall mining above the <br /> West Elk Mine have been less than initially projected as reported in Exhibit 60 (Dunrud et al., <br /> 1998 rev.) and 60E (Wright Water Engineers, Inc. [WWE], 2012). Rockfalls and/or landslides <br /> have generally been observed only sporadically in the Box Canyon mining area since 2006 where <br /> the steep, upper reaches of Sylvester Gulch and Box Canyon abut the large geographic feature <br /> known as West Flatiron. In the flatter and more rounded topography of the Apache Rocks and <br /> Southern Panels mining areas, the rockfall and landslide potential is much smaller. However, <br /> subsidence-related tension cracks have occurred in these mining areas, particularly above the <br /> active longwall mining face. <br /> E-seam longwall mining in the Southern Panels Mining Area was initiated on Panel E1 in <br /> December 2008 beginning at the east end and progressing westward. All mining in the Southern <br /> Panels Mining Area is planned to progress from the east end of the panels toward the west. As of <br /> the time of our fall 2019 field visit, mining was complete in E-seam Longwall Panels E1 through <br /> ET Mining of Longwall Panel E8 was initiated in late December 2018 and was approximately <br /> seventy-five percent(75%) complete as of the time of our fall 2019 field visit. <br /> Beginning with the Spring 2011 Subsidence Report, an effort was made to reduce the size of the <br /> semi-annual subsidence reports by eliminating much of the regularly included background and <br /> historical information (e.g., subsidence projections). For this reason, specific details associated <br /> with subsidence projections and field recognition of subsidence and non-subsidence features were <br /> eliminated. Since that time, readers have been directed to Sections 1.0 and 2.0, respectively, of <br /> the Spring 2011 Subsidence Report and to Exhibits 60 and 60E of the West Elk Mine permit for <br /> this information. <br /> Also, in keeping with the goal of a reduction in report size, this and future reports will focus on <br /> the identification and discussion of those locations that reflect an obvious change in the conditions <br /> (including follow-up observations of previously-discussed conditions)overlying the active portion <br /> of the mine and on documenting baseline conditions in areas that have yet to be mined. For this <br /> reason, observations from our fall 2019 field visit were focused on areas above mined E-seam <br /> 831-032.910 Wright Water Engineers, Inc. Page 5 <br /> February 2020 <br />