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For the temporary nearly vertical bench face (prior to reclamation), additional <br />potential wedges may exist due to the steep overall slope angle. These wedge <br />failures have been observed occasionally on the east wall and are localized in <br />extent. The development and size of these wedge failures will be controlled by <br />the discontinuous nature of the discontinuities mapped in the quarry. <br />6.2.2 North Walls <br />Similar to the previous LF&A annual reports, the north wall has been subdivided <br />' into two separate slopes for analysis: the northeast and the northwest wall. The <br />instabilities observed in the eastern section of the wall and the differing slope <br />orientations necessitated the distinction between the two slopes. To take into <br />account the shallower slope angle of the past three benches as well as the final <br />' mine plan design, a 35° dip angle for the slope was used in the analysis of each <br />of the north walls. <br />As previously documented along the northeast wall, and as described in this <br />report, planar failures can occur when foliation planes that are intersected by two <br />or more joints daylight in the exposed highwall. The stereonet plots shown for <br />the northeast wall (Figure 11) and the northwest wall (Figure 12) indicate a <br />possibility for planar failure along the foliation plane F-1. Planar failure can occur <br />because the dip direction of the F-1 plane falls between the dip direction of the <br />slope face and the trend of the line of intersection formed by F-1 and P-2. In <br />addition, based on the stereonet plots, intersections between discontinuities F-1 <br />and P-2 and F-1 and P-3 will potentially occur, and each of the intersections will <br />fall very close to or within the daylighting envelope. <br />For the 2004 analysis (LF&A, 2004), the long-term impact of foliation F-1 on the <br />stability of both the northeast and northwest walls was further investigated using <br />discontinuity data that include elevation information for the foliation orientation. <br />These data were plotted on a chart showing dip angle in degrees versus <br />20 - <br />