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Spring 2009 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• <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 May 2009 field visit are <br />included as figures in the text of this report. Where these images have notable differences from <br />comparable photographs taken in previous years, the older images are also included as figures for <br />comparison purposes. In cases where little or no significant change occurred from previous <br />observation and photographs, only the latest photograph is typically 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 />(also A' of Traverse A -A'). As a result, there were no signs of the commonly observed sloughing <br />and slumping along the cut -slope side of the roadway along most of the traverse. <br />Because of the roadway location relative to the source area of the October 2008 rockfall, WWE <br />was unable to stop and make a close inspection. However, photographs were taken from along <br />831 - 032.791 Wright Water Engineers, Inc. Page 17 <br />November 2009 <br />