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1100318 R0T0 0811 JRW1 42 <br />6 Other Landslide Causes Ruled Out <br />Exponent performed engineering analyses to determine the cause of the December 2, 2008 <br />landslide. The scientific methodology utilized identifies other potential causal mechanisms of <br />the landslide identified by Exponent and other investigators58, 59 and methodically analyzes each <br />mechanism using the available data and established engineering analytical tools. When the <br />analytical results are incongruous with the available data, the mechanism is deemed non-viable. <br />6.1 Overly Extensive Excavation of Area H <br />Over excavation of Area H, either vertically or horizontally outside the limits established in the <br />1994 Amendment, has been considered as a possible cause of the slope failure.60 Discussions <br />with the Pikeview Quarry staff indicated that the bench configuration was modified for the two <br />deepest benches in Area H to be 10 feet wider than originally planned. This description of the <br />bench condition is consistent with the data contained in the topographic survey (Appendix 46) <br />and photographs in the appendices taken starting in 2007. The wider bench condition is <br />beneficial for stability of the slope. <br />The target bottom elevation for the deepest portion of Area H was reported by Pikeview Quarry <br />staff to be 7110 feet. The elevation survey in Appendix 46 indicates that the elevation of the <br />lowest area of Area H was not excavated below an elevation of 7010 feet. The surveyed spot <br />elevations of this area vary between 7113.1 and 7115.1 feet. <br /> <br />58 J. Davidson, United States Department of Labor, Mine Safety and Health Administration, Technical Support, <br />Slope Stability Evaluation, Pikeview Quarry – (ID No 05-1443), September 17, 1986 (Appendix 49) <br />59 State of Colorado, Colorado Geological Survey, Quarry Wall Rockslide at Pike View Mine – Summary Report, <br />January 7, 2009 (Appendix 48) <br />60 State of Colorado, Colorado Geological Survey, Quarry Wall Rockslide at Pike View Mine – Summary Report, <br />January 7, 2009 (Appendix 48)