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These shallow dipping discontinuities along the foliation can have a significant impact on the stability of the north wall and should be monitored closely as excavation progresses. This indicates that the potential exists for future instabilities to occur on the north walls as the pit is excavated to its final depth. 6.2.3 West Walls No major stability issues currently exist for the west walls of the main pit or middle level of the quarry. Previous analysis indicated that the west highwalls have approximately the optimum orientations for stability. Two west wall orientations were analyzed in this study. The first had a dip direction of 091 °, and with this orientation the stereonet plot (Figure 14) indicated three plunges of line intersections less than the angle of the slope face. Each of the intersections were at angles lower than the critical friction angle indicating that sliding along these surfaces is unlikely. The second western wall analyzed in this study, had a dip direction of 120° (Figure 14). The results for this analysis yielded fairly comparable results, but the intersection of F-1 and P-2 does fall within the shaded region and sliding is assumed to occur as the plunge of the line of intersection exceeds the 33° angle of friction. 6.2.4 South Walls As with the north wall and west wall, the southern wall has also been subdivided ' into separate slopes for analysis: two southwest walls and a southeast wall orientation were selected based on the Projected Lafarge mine plan (Lafarge, ' 2003). This approach differs from the 2002 annual report, in which the southern walls were measured based on configurations in the main pit. Figures 15 and 16 ' present the stereonets for each wall. ' The wedge stability analysis for each of the southwest walls indicates one plunge of line of intersection that is very close to daylighting into the slope face. The -17-