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Subsidence Field Observations <br />West Elk Mine <br />August 28 and 29, 2001 <br />• The cracks in this resistant sandstone outcrop show some signs of aging, but no <br />intilling, sloughing, or sealing. However, cracks and local piping features are now <br />present in surficial material (sand, silt and clay) a few inches to a few feet thick that <br />were not there last year at this time (Figure 4). <br />• One recent crack, which is as much as 6 inches wide in the surficial material and as <br />much as 3'/z inches wide in the underlying bedrock, is about 75 feet long. It is located <br />about 10 feet south of the crack shown in Figure i of the 2000 report, and has roughly <br />the same trend (N65-75°W) (Figure 5). <br />1 <br />831-032.560 <br />September 2001 <br />1 <br />Wright Water Engineers, Inc. <br />Page 8 <br />Figure 4. Eastward view of an extensive crack located al Apache Rocks. <br />This crack is further revealed in the surficial material in the <br />foreground than i[ was last year. <br />