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Exhibit 60C <br />Subsidence Evaluation and 2004 Geologic Hazard Field Observations <br />West Flatiron Lease Area <br />• may be affected in a minor way. The rockfall potential in this area is high and therefore the <br />natural rockfall process may be accelerated by at least a minor amount. <br />This potential rockfall acceleration estimate is based on the effects observed in a rockfall- <br />landslide area above mined longwall panel 22. The area is located in the scarp area at the head of <br />the first east drainage of Sylvester Gulch (see Subsidence and Geologic Field Observations - <br />Apache Rocks and Box Canyon Mining Areas, July 12-I5, 2004 for more information). The <br />natural rockfall potential there is very high (the cliffs and underlying steep slopes aze the highest <br />in the Apache Rocks and Box Canyon mining areas). Based on the observations at the head of <br />the first east-trending draw of Sylvester Gulch, the natural rockfall-landslide area located above <br />the southeastern part of un-mined longwall panel 21 may be accelerated when [he pane] is mined. <br />Although the natural rockfall potential is high in rockfall and landslide areas, the safety risk is <br />low because the location is remote from human activities. <br />C~ <br />• <br />831-032.650 Wright Water Engineers, Inc. Page 2 <br />November 2004 <br />