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11) A section of the northeast wall of the main pit originally experienced planar <br />failure along the foliation planes in 1998. Following removal of the next <br />bench in 1999, a larger section of the wall that is approximately 350 feet <br />wide by 250 feet high experienced planar failure. The north wall pit slopes <br />were modified in response to these failures, and based on continued photo <br />documentation and visual monitoring since that time, no additional <br />movement has been detected (Photo 7). As described in previous annual <br />reports, the failure is believed to have occurred when a continuous foliation <br />plane was intersected by two or more existing discontinuities, and <br />daylighted in the exposed highwall. (See the Wedge Stability Analysis <br />section of this report for a complete description of this type of failure). <br />Based on the latest topographic map (December, 2003) of the quarry <br />provided to us, the overall effective angle of the north pit walls has been <br />modified over the last three benches to an angle of 35° per L&A <br />recommendations in the May 2003 report. The failure surfaces (i.e. the <br />surfaces along which movement has occurred) remain at a "residual <br />strength" and therefore are less resistant to additional loading. Although <br />the slope configuration is currently stable, the failure mechanism could <br />potentially be reactivated upon removal of subsequent benches, resulting in <br />movement of additional material. <br />12) The highwall adjacent to the lower asphalt plant facilities and the area <br />above the highwall were visually inspected as part of the field <br />reconnaissance inspections performed in January 2007. Unlike the <br />highwalls for the areas currently being mined, the bedrock in the highwall of <br />the asphalt plant is sedimentary, consisting of shales and sandstones <br />upturned to near vertical orientations, striking almost north-south. The <br />highwall located immediately west and north of the bottom plant facility is <br />currently stable, with no evidence of highwall instabilities. No major cracks, <br />settlement, or ponding areas were observed at the ground surface above <br />-13- <br />