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Exhibit 60C <br />Subsidence Evaluation and 2004 Geologic Hazard Field Observations <br />West Flatiron Lease Area <br />1.0 SUMMARY OF MAJOR FINDINGS <br />Alter six years of field observations (1999 to 2004), three years pre-mining and three years post- <br />mining, in Apache Rocks and Box Canyon mining areas, no subsidence cracks have been <br />observed in alluvium above the longwall panels that were mined. In particular, no subsidence <br />features (cracks or bulges) were observed in Deep Creek within the area of mining influence of <br />mined longwall panels 14 through 17, nor were any subsidence features observed in Sylvester <br />Gulch above mined longwall panels 15 and 16. The overburden depth to the B Seam in both <br />lengths of stream that are underarined ranges from about 900 to 1,600 feet. <br />Based on the results of these observations, no subsidence cracks are expected to occur in the <br />alluvium and colluvium in that part of the Raven Gulch tributary if longwall mining panels 18 <br />and 19 were projected to the eastern limit of the West Flatiron Lease area Should this eastward <br />panel extension plan be adopted, and should the eastern boundary of the lease be required to be <br />out of the area of mining influence, the eastern limit of dre panels wuld be detemvned by a <br />buffer zone, established by the angle of draw. Using a very conservative draw angle value of 25 <br />degrees (the maximum angle of draw measured in the West Elk mining area is 20 degrees), the <br />width (horizontal distance) of the buffer zone would be 47 feet for every 100 feet of overburden. <br />The landslides located on the southwest flank of West Flatiron, above mined longwall panels 14 <br />and 15, show no evidence of being affected by the mining. Therefore, the landslides mapped in <br />the West Flatiron Lease area are not expected to be affected by longwall mining. landslide <br />areas, however, may be affected by mining if the mining is done during a period of anomalously <br />high precipitation-such as occurred in the mid 1980s and mid 1990s. <br />The rockfall and landslide area that is located within the area of mining influence above the <br />southeastern part of un-mined longwall panel 21 (but located in the Box Canyon mining area) <br />• <br />831-032.650 Wright Water Engineers, Inc. Page 1 <br />November 2004 <br />