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Fall 2008 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />The overburden depth to the B-seam ranges between 1,625 and 2,175 feet. Observed subsidence <br />related features along this traverse included a crack at Location 2 and a rockfall at Location 3 <br />(Map 1). <br />5.4.1 Location 2 <br />A subsidence crack is located primarily in soil and colluvium in and above the roadcut (Figure 8) <br />at this location. The crack trends roughly parallel to the long direction of mined Longwall Panel <br />14 near the headgate entries. At this location, the exposed crack in the sandstone bedrock <br />decreases in width downward from approximately 0.25-inch to a hairline over a vertical distance <br />of about 3.5 feet. The crack trend is approximately N70°W for a distance of about 50 feet <br />upslope and changes to a N5 5'W trend over the next 100 feet or more. Where this crack occurs <br />in the soil and colluvium above the exposed bedrock, it appears to be 6 to 12 inches wide with a <br />depth of as much as 12 to 24 inches. Considerable sandy material was observed in and around <br />the crack trace, suggesting heavy runoff had occurred in this area, thus contributing to the erosion <br />0 and widening along this crack trace. <br />A photographic comparison to the previous photograph taken at.this location (i.e., Figure 10 of <br />the spring 2007 report) show there to be few observable differences. <br />• <br />831-032.790 Wright Water Engineers, Inc. Page 22 <br />December 2008