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Subsidence Field Observations <br />West Elk Mine <br />July 22-24, 2003 <br />1.0 SUMMARY OF MAJOR RESULTS OF THE 2003 SUBSIDENCE STUDY <br />1. As reported last year, no subsidence features (crack or bulges) were observed within the <br />azea of mining influence of mined-out longwal] Panels 14 and 15. This yeaz, no <br />subsidence features were observed on the foot traverse above mined-out longwal] Panels <br />16 and 17. <br />2. Subsidence cracks, which were observed in soil and weathered bedrock during the 2002 <br />field study within the azeas of mining influences of mined-out longwal) Panels 13, 13A, <br />14, and 15, are less visible than last yeaz. There is no longer any trace of them. The <br />processes of mass wasting, weathering, sloughing, and infilling have completely healed <br />and sealed them. <br />3. Subsidence cracks and bulges in softer sandstone that were very abundant during mining <br />in 1999, such as those above longwal] Panel 13, aze less evident than they were in 2002. <br />With the exception of two nearly obliterated, parallel cracks and a branching crack, no <br />cracks aze evident. <br />4. Most of the major cracks that were in durable sandstone at Apache Rocks last year (and <br />since the area was undermined by longwal] Panel 12 in 2000) appeaz similar to their <br />condition in 2002 when they were estimated to be 10 [0 20 percent wider and 20 to 40 <br />percent longer than they were in 2001. Some of the widest cracks are slightly longer than <br />in 2002 because more colluvium and soil has caved and sloughed into the underlying <br />cracks (which were likely present even in 2000). <br />' 831.032.610 Wright Water Engineers, Inc. Page 1 <br />September 2003 <br />