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Martin Marietta Materials Spec-Agg 2017 Annual Report representative discontinuity orientations of these joint and foliation sets in this area to evaluate their potential to contribute to large-scale slope failure modes. As shown in Figure 8, the stereonet plot for East Walls 1 and 2 do not indicate the possibility of planar failure. 6.4.3 Northern Walls For the 2017 Annual Report, we analyzed four northern wall orientations based on the locations shown in Figure 2 and Table 2: Northeast Walls 1 through 3, and the Northwest Wall correspond to the same wall locations and orientations analyzed in the previous 2013-2016 annual reports (Figure 2). The stereonet plot for Northeast Wall 1 indicates that with the slightest variation of joint sets P-2 or P-3 a potential planar failure mode along foliation F-1 exists for this slope orientation (Figure 9). This is the same foliation orientation that was believed to contribute to the 1998 slope instability(Photo 5). The stereonet plot for Northeast Wall 1 also shows two discontinuity intersections that fall within the failure envelope, suggesting that wedge failures are kinematically possible for this slope orientation (Figure 9). The intersecting sets that may result in wedge failure include foliation F-1 and joint P-2, and foliation F-1 and joint P-3. The stereonet plot for Northeast Wall 2 shows one discontinuity intersection that falls within the failure envelope, suggesting that wedge failure is kinematically possible for this slope orientation (Figure 9). The intersecting sets that may result in wedge failure include foliation F-1 and joint P-3. Planar failure is not indicated in the stereonet plot for Northeast Wall 2. As described above, the development and size of wedge failures will be controlled by the variability and limited lateral extent of the discontinuities. As excavation proceeds in the Northeastern walls, additional measurements are needed to refine the representative discontinuity orientations of these joint and foliation sets in this area to evaluate their potential contribute to large-scale slope failure modes. The stereonet plot for Northeast Wall 3 indicates that with the slightest variation of joint sets P-2 or P-3 a potential planar failure mode along foliation F-1 exists for this slope orientation (Figure 9). This is the same foliation orientation that was believed to contribute to the 1998 slope instability. The stereonet plot for Northeast Wall 3 shows two discontinuity intersections that fall within the failure envelope, suggesting that wedge failure is kinematically possible for this slope orientation (Figure 9). The intersecting sets that may result in wedge failure include foliation F-1 and joint P-3, and joint sets P-2 and P-7. Based on the current as well as previous year's data set,joint P-7 has weak signatures represented by relatively few measured orientations representing these features (Figure 6). The Northeast Wall 3 was not accessible for direct measurements or observations during our site visits. Additional measurements and observations are needed to assess the potential for large scale planar sliding along foliation F-1 as excavation continues to extend below the Northeast Wall 3 in the future (there is currently no mining activity). The stereonet plot for the Northwest Wall (Figure 10) shows one discontinuity intersection that may fall within the failure envelope, suggesting that wedge failure is kinematically possible for this slope orientation. The intersecting sets that may result in wedge failure include foliation F-1 and joint P-2. Planar failure is not indicated in the stereonet plot for the Northwest Wall (Figure 10). However, even a slight variation of the foliation F-1 would create the potential for planar sliding. February 27,2017 Page 9 Lachel & Associates, Inc. Project 16C64003 00 ©2017 All Rights Reserved