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January 15, 2008 Page 50 <br />mining, but it might be an option in the future depending on overburden thickness and proximity <br />to property boundary. The reserves uphill from A-Pit (referred to as East-Panel) will eventually <br />be mined. When East-Panel mining occurs, the hillside will be mined on two sides creating <br />geometry similar to the pre-landslide geometry in the G-Pit area. Thus, global hillside stability is <br />a concern and has been examined. <br />A 3D numerical model was developed6 assuming a 150-ft barrier pillar would be left <br />between A-Pit mining and the future East-Panel mining. The area simulated is shown in <br />Figure 30 where the red lines indicate the assumed extent of mining. Mining of East-Panel was <br />assumed to the Q-Seam; A-Pit mining was assumed only to the H-Seam. The model geometry <br />and mining sequence are shown in Figure 36. This analysis assumed the same rock properties <br />and groundwater conditions assumed in landslide back-analysis study. These conditions are <br />thought to be conservative, especially in the lower portion of the hillside based on borehole logs <br />and laboratory testing performed in 2005. <br />Results of the stability analysis indicate that the East-Panel hillside is expected to remain <br />stable, even under severe groundwater and low L-Roof mudstone strength conditions. This is <br />due in part to flatter bedding in this area than in the G-Pit landslide area. Also, average L-Roof <br />mudstone strength properties appear to be higher and less variable than measured in the G-Pit <br />landslide area. <br />As mining in East-Panel area commences (expected 2015-2017), further characterization <br />should be performed. The objective of characterization would be to identify weak strata and <br />unusual patterns in groundwater behavior. It will be important to monitor behavior of the south <br />end wall in A-Pit as the A-Pit cuts are advanced (expected 2013) in the event that further <br />analysis is required. <br />The role of faulting has not been explicitly considered in the stability analyses. Faults are <br />not known to have played a role in past failure mechanisms. However, in the A-Pit area, two <br />significant offset faults have been mapped. Their characteristics in the eastern portion of A-Pit <br />are not known, but they have not influenced highwall stability in the past. These and other faults <br />should be characterized in this area of the mine, especially for their potential for acting as a <br />groundwater barrier or geometric condition for large-scale block kinematic instability. <br />5.2.3 K-Pit and G-Pit Mining Plan <br />Approximately 70% of the K-Pit and G-Pit areas have been impacted by the G-Pit <br />landslide; there is no evidence of impact in the East-Panel area. The mine plan for this area has <br />been laid out in three areas: K-Pit truck-and-shovel (T & S) area, G-Pit dip-pit combination T & <br />S/dragline area, and East-Panel dip-pit dragline area. Figure 37 shows the cut layouts for these <br />areas. Also shown in this figure are the outline of the landslide area and post-landslide <br />topographic contours. <br />Once mining the Z-Dip Pit cuts is complete the dragline is scheduled to move to the most <br />western cut in K-Pit. The overburden is shallowest here as the strata outcrop along the ridgeline. <br />The T&S fleet will uncover the L-Seam. The dragline will follow behind after the L-Seam is <br />Agapito Associates, Inc.