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Spring 2008 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• northern edge of this gravity-induced crack is located very close to the southern edge of the <br />`1DW Pad located over Lon4,wall Panel 21 where Huge extensive surface cracking has been <br />observed in the massive sandstone cliffs since lonuwall mining occurred. It \vas easy to <br />determine that this was not a minin-related crack hecause no mining had Occurred in the area. <br />The possibility of gravity-induced cracking in the rug_"cd country ahow planned minin`T activities <br />at the West Elk Mine is a 1200d reason to perform hnsClinC studies of the area prior to 1111111112 SO <br />that thCSC featurCS Can he documented. <br />C7 <br />Figure 4. Gravity-induced tension cracks located above unmined coal <br />in the upper, massive sandstone of the Ohio Creek Member of the <br />Mesaverde Formation, (looking northwest). Joints have opened up a <br />foot or so due to gravitational stresses under little or no lateral <br />constraint. <br />• 831-03'. i 90 Wright Water Engineers, Inc. Page 8 <br />August 2008