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Martin Marietta Materials <br />Spec -Agg Project <br />8) The sump installed in the past year has been pumping approximately 81,000 gallons per day to keep <br />the main pit dry (Photo 5). This process has been successful at keeping the main pit operational so <br />far. <br />9) A section of the northeast wall of the main pit originally experienced planar failure along the foliation <br />planes in 1998. Following removal of the next bench in 1999, a larger section of the wall that is <br />approximately 350 feet wide by 250 feet high also experienced planar failure. As described in previous <br />annual reports, the failure is believed to have occurred when a continuous foliation plane was <br />intersected by two or more existing discontinuities, and daylighted in the exposed highwall. (See the <br />Wedge Stability Analysis section of this report for a complete description of this type of failure). The <br />north wall pit slopes were modified in response to these events, and based on continued photo <br />documentation and visual monitoring since that time, no additional movement has been observed <br />(Photo 7). <br />Based on the latest topographic map of the quarry provided to us (December, 2007), the overall <br />effective angle of the north pit walls has been modified over the last three benches to an angle of 35 °, <br />which is consistent with the 2003 Lachel geotechnical evaluation (L&A, 2003). The failure surfaces <br />(i.e. the surfaces along which movement has occurred) remain at a "residual strength" and therefore <br />are less resistant to additional loading. Although the slope configuration is currently stable, the failure <br />mechanism could potentially be reactivated upon removal of subsequent benches, resulting in <br />movement of additional material. <br />10) The highwall adjacent to the lower asphalt plant facilities and the area above the highwall were visually <br />inspected as part of the field reconnaissance inspections performed during our site visits. As <br />discussed in Section 2.0, the bedrock in the highwall of the asphalt plant is sedimentary, consisting of <br />shales and sandstones upturned to near vertical orientations, striking almost north- south. The highwall <br />located immediately west and north of the plant facility is currently stable, with no evidence of highwall <br />instabilities. No major cracks, settlement, or water ponding areas were observed at the ground surface <br />above the highwall, and it appears that the highwall is stable under the current conditions. <br />In addition to the inspection of the highwall, observations along the access road to the upper asphalt <br />plant facilities were also made with no surface cracks or settlement noted. The road is aligned <br />perpendicular to the strike of the nearly vertical bedded sedimentary rock, which is a favorable <br />orientation for slope stability along the access road. <br />February 13, 2012 <br />Project 11361017.00 <br />Page 7 <br />Lachel & Associates, Inc. <br />©2012 All Rights Reserved <br />