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5.2.1 East Wall <br />' Historically, the east wall has had no major instability issues. The stereonet plot for the <br />east wall (Figure 11) was derived from the full dataset and shows multiple plunges of lines <br />' of intersection less than the angle of the slope face and one intersection that falls within <br />the failure envelope. Consequently, the potential for sliding exists, but is unlikely, along <br />' many of these plane intersections, but sliding is only plausible along one. Foliation plane <br />F-3 and joint P-5 are the only planes having a line of intersection that not only daylights <br />' the pit wall, but also plunges at an angle steeper than the angle of friction. Therefore, if <br />this intersection of planes exists in the eastern wall area, sliding is kinematically feasible. <br />' All other plunge lines of intersecting planes that daylight the pit wall are inclined at an <br />angle less than the angle of friction, and therefore are kinematically stable. <br />For the temporary nearly vertical bench face (prior to reclamation), additional potentially <br />unstable wedges may exist due to the steep overall slope angle (e.g. P3:P1 and P4:P1). <br />These wedge failures have been observed occasionally on the east wall and are localized <br />in extent. The development and size of these wedge failures will be controlled by the <br />limited extent of the discontinuities mapped in the quarry, and by the limits on bench <br />height. <br />5.2.2 North Walls <br />Consistent with the previous L&A annual reports, the north wall has been subdivided into <br />two separate slopes for analysis: the northeast and the northwest walls. The instabilities <br />observed in the eastern section of the wall and the differing slope orientations <br />necessitated the distinction between the two slopes. To take into account the shallower <br />slope angle of the past three benches as well as the final mine plan design, a 35° overall <br />dip angle for the slope was used in the analysis of each of the north walls. <br />As previously documented along the northeast wall, and as described in this report, planar <br />failures can occur when foliation planes that are intersected by two or more joints daylight <br />in the exposed highwall. The stereonet plots shown for the northeast wall (Figure 12) and <br />-15- <br />Lachel & Associates <br />4 SCUkkt!f:i FnGln[Fa1Nv 701!PXMY