Laserfiche WebLink
2004 Geologic Hazard Field Observations <br />Sarlh of Divide Mining Area <br />• longwall panel 1'n and in the upper parts of Sylvester Gulch (above mined longwall panels 14 <br />1~. <br />The probable reason for the lack of cracking in alluvium is that the fine silt- to clay-sized <br />material and overlying soil can yield without cracking or bulging as it defomrs as a discrete unit <br />in the subsidence process. The estimated thickness of the alluvium observed dining geologic <br />mapping activities ranges from about 25 feet to as much as 150 feet in the West Elk mining <br />area-including the South of Divide mining area. <br />Based on annual field subsidence observations in the Apache Rocks and Box Canyon mining <br />areas, the maximmn crack depth in bedrock outcrops and weathered bedrock areas in the South <br />of Divide mining area is estimated to be: 1) 5 to 15 feet in terrain sloping less than, or equal to, <br />30 percent, and 2) 10 to 35 feet in the same terrain sloping more than 30 percent (Table 1). <br /> <br />• <br />831-032.627 Wright Water Engin~rs, Inc. Page 77 <br />November 2004 <br />