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Fall 2009 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• 5.0 TRAVERSES AND OBSERVATIONS IN THE BOX CANYON, APACHE <br />ROCKS, AND SOD MINING AREAS <br />A detailed discussion of observations associated with traverses A-A' through N-N' is provided in <br />this section (Maps 1 and 2). Many of the photographs taken during the October 2009 field visit <br />are included as figures in the text of this report. Where these images have notable differences <br />from comparable photographs taken in previous years, some of the older images are also <br />included as figures for comparison purposes. In cases where little or no significant change <br />occurred from previous observation and photographs, only the latest photograph is typically <br />included. <br />5.1 Traverse A-A' <br />Traverse A-A' begins at a fork in the main Sylvester Gulch road, winds above mined Longwall <br />Panel 25, mined Longwall Panels 19 to 21, and ends at the drill pad for MDW 21-18 and <br />• Photographic Observation Point 8 (Map 1). Locally deep soil and colluvium, from clay- to <br />boulder-size, derived primarily from the Barren Member of the Mesaverde Formation, and local <br />bedrock outcrops of the Barren Member were observed in the road cuts along this traverse. The <br />overburden depth to the B-seam ranges from about 500 to 1,150 feet. In places, the drill road is <br />quite unstable where the cut slopes are over-steepened. <br />In October 2008, a significant rockfall (Location 1) occurred along the lower reaches of this <br />traverse in the Sylvester Gulch drainage. This rockfall occurred during the mining of Longwall <br />Panel 25. That rockfall created a blockage of the road which prevented observations along this <br />entire traverse during our fall 2008 site visit. Sometime prior to our spring 2009 field visit, this <br />roadway was graded and cleared of debris over its entire length to the drill pad for MDW 20-19 <br />(Photographic Observation Point 8 and also A' of Traverse A-A'). October 2009 observations <br />found the roadway to remain mostly clear with a few areas of observed sloughing and slumping <br />along the cut-slope side of the roadway along the steepest portions of the traverse. No cracks <br />were observed in the roadway even though the latter half is mostly over the central portion of <br />• mined Longwall Panels 19, 20 and 21. <br />831-032.791 Wright Water Engineers, Inc. Page 17 <br />April 2010