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Mr. Jim Mattern March 19, 2007 Page 10 Table 2. Assumed Bedding Plane Orientations Dip Dip Direction Applied Coordinate Range ('I I~l 8.0 5.0 X = 7,400 to 9,800 Y = 2,200 to 6,200 12.0 5.0 X = 7,400 to 9,800 Y = 0 to 2,200 10.0 25.0 X = 4,900 to 7,400 model base had azero-displacement condition to simulate rock to an infinite depth. Vertical stresses were determined based on gravitational loading of the material and horizontal stresses assumed lithostatic loading from vertical stresses according to Poisson's effect (v/1-v). G-Pit Mining Sequences There were four states simulated which correspond to conditions prior to any mining, conditions prior to summer of 2005, conditions after Gs-6 Cut was made and the September 2005 failure occurred in the strike pit, and conditions at the time of the landslide failure. The modeling sequences are as follows: Pre-Mining Conditions: In situ stresses are applied to the model before any excavations are made. The ratio of horizontal to vertical stresses is assumed 0.45 and stresses equilibrate depending on topographic geometry and material layer densities. Compute equilibrium condition. Geometry is as shown in Figure 3b. 2. Previous Minine Conditions: Mining of H-Seam to the east and G Strike Cuts Gs-4 and 5 are simulated to a depth below Q-Seam. Spoils are placed above the H-Seam area and Gs-4 Cut area. Compute equilibrium condition. Geometry is as shown in Figure 5. 3. Gs-6 Cut Pre-Failure Conditions: Mining of Gs-6 excavation is simulated to bottom of M-Seam. Spoils are placed in Cut Gs-5 cut from above Q floor mudstone to 7,070 ft elevation where the dragline was situated at the time of the September 2005 highwall failure. Compute equilibrium condition. Geometry is as shown in Figure 6. 4. Gs-6 Cut Failure Conditions: Add pore water pressure to simulate precipitation leading to failure. Compute equilibrium condition. Geometry is same as shown in Figure 6. 5. Gd-2 Box Cut Pre-Failure Conditions: Place spoils in Gs-6 Cut to buttress highwall. Remove pore water pressures to simulate long time without high precipitation. Mine G-Dip Box cuts to top of I2-Seam on north and K-Seam on south and remove overburden from H-Seam south of box cut. Compute equilibrium condition. Geometry is as in Figure 7. 6. Gd-2 Cut Precipitation Conditions: Add pore water pressure to simulate precipitation. Compute equilibrium condition. Geometry is same as shown in Figure 7. Agapito Associates, Inc.