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demonstrates that the mine workings will be stable and that overlying structures will not suffer <br />irreparable damage." The SCCC design is for stable underground workings in both the main <br />entries and the continuous miner development areas, as validated by the evaluation conducted by <br />SubTerra, Inc. <br />In the lower right corner of Exhibit 2.05.6-E3, Illustrated Effects of Mine Subsidence, it is <br />shown that the subsidence effects of the collapse of roof or pillars can be stopped by strong roof <br />rock strata. The roof strata above the Wadge Seam, throughout the permit area, have strong "B" <br />and "C" sandstones in the immediate roof. These units have a compressive strength of 10,000 to <br />30,000 psi and tend to form an arch over any localized roof failures, minimizing the potential for <br />surface subsidence. <br />SCCC recognizes that unknown and unpredicted structures and faults can be encountered in <br />underground mining that can affect mine stability. Extensive drilling and seismic work has not <br />identified any significant structures or faults that could affect stability in the mine portal area. <br />None of these structures have been identified in the mine portal area. SCCC is therefore <br />proposing an underground monitoring and reporting program, focusing on ongoing geologic <br />mapping, rather than monuments on the surface that will only measure subsidence after it has <br />occurred. The underground monitoring program is designed to identify any significant structures <br />or faults, not previously identified that could affect stability and lead to subsidence. This <br />program is section 2.05.6(6) of the PSCM permit application. <br />14