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' l <br />t <br />l <br />h <br /> appear more preva <br />en <br />a <br />ong t <br />e south wall possibly due to the north facing <br />' exposure. <br />' 10) The small surficial slide located in the exposed highwall face along the west <br /> wall, which was noted in previous annual reports, appears unchanged from <br />' over multiple years of observation. The slide does not have any impact on <br /> the overall stability of the wall, as it is limited to less than a single bench in <br />' height, and is considered a localized wedge failure. <br />' 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 that is approximately 350 feet wide by 250 <br />feet high, experienced planar failure. The north wall pit slopes were <br />' 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 10). 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 current topographic map (December, 2003) of the quarry, the <br />overall effective angle of the north pit walls has been modified over the last <br />' three benches to an angle of 35° per L&A recommendations in the May <br />2003 report. The failure surfaces (i.e. the surfaces along which movement <br />' has occurred) remain at a "residual strength" and therefore are less <br />resistant to additional loading. Although the slope configuration is currently <br />' stable, the failure mechanism could potentially be reactivated upon removal <br />of subsequent benches, resulting in movement of additional material. <br /> <br />-13- <br />1