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Spring 2008 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• <br />• <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 M-M' is provided <br />below (see Maps 1 and 2). In many circumstances, photographs of locations observed during the <br />June, 2008 field survey has been compared to photographs taken in previous years. The <br />photographs taken during the most recent field observations are included as figures in the text of <br />this report. Where these images have significant differences relative to comparable photographs <br />taken in previous years, the older images are also included as figures for comparison purposes. <br />In cases where little or no significant change occurred from previous observation and <br />photographs, only the latest photograph is included. <br />5.1 Traverse A-A' <br />Traverse A-A' begins at a fork in the main Sylvester Gulch road, winds above planned Longwall <br />Panel 25, mined Longwall Panels 19 to 21, and typically ends at MDW 21-18 and Photographic <br />Observation Point 8. However, during the spring 2008 field visit a small surface slump blocked <br />the road approximately 200 yards above the switchback over mined Longwall Panel 21. An <br />earthwork contractor was clearing the road at the time of our visit and the access was restricted <br />such that no observations could be made even of the small slump itself. <br />Locally deep soil and colluvium, from clay- to boulder-size, derived primarily from the Barren <br />Member of the Mesaverde Formation, and local bedrock outcrops of the Barren Member were <br />observed in the road cuts along this traverse. The overburden depth to the B-seam ranges from <br />about 500 to 1,150 feet. The numerous rocks on the drill road indicate recent sloughing along <br />much of the traverse. <br />No cracks were noted in the road along this traverse even though the latter half is mostly over the <br />central portion of mined Longwall Panels 19 to 21. A few slumps were observed in over- <br />steepened cutbanks in the road. It is assumed that the small slump above the switchback over <br />mined Longwall Panel 21 was similar to those observed at lower elevations. The possibility that <br />831-032.790 <br />August 2008 <br />Wright Water Engineers, Inc. <br />Page 14