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Spring 2008 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />is 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 3 and a rockfall at Location 4 <br />(Map 1). <br />5.4.1 Location 3 <br />A subsidence crack is located primarily in soil and colluvium in and above the roadcut (Figure <br />10). The crack trends roughly parallel to the long direction of mined Longwall Panel 14 near the <br />headgate entries. At this location, the exposed crack in the sandstone bedrock decreases in width <br />downward from approximately 0.25-inch to a hairline over a vertical distance of about 3.5 feet. <br />The crack trend is approximately N70°W for a distance of about 50 feet upslope and changes to a <br />N55°W trend over the next 100 feet or more. Where this crack occurs in the soil and colluvium <br />above the exposed bedrock, it appears to be 6 to 12 inches wide with a depth of as much as 12 to <br />24 inches. Considerable sandy material was observed in and around the crack trace, suggesting <br />heavy runoff had occurred in this area, thus contributing to the erosion and widening along this <br />crack trace. <br />A photographic comparison to the spring 2007 photograph at this location shows there to be <br />minimal observable differences (see Figure 6 of that report). <br />• 831-032.790 Wright Water Engineers, Inc. Page 21 <br />August 2008