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• about 25 to 50 feet higher than the top of the ridge at the west side to obtain the <br />desired capacity. The waste pile configuration includes a sloped face with benches <br />and associated ditches at 50-foot vertical intervals. Benches should be sloped <br />approximately 0.5 percent to the south. <br />The calculated maximum capacity for this configuration is on the order of 3 <br />million cubic yards. Figure 6 shows the estimated volume according to stations <br />along the axis of the pile from north to south. The locations of the stationing and <br />sections are illustrated on Fig. 1. <br />The waste pile was designed as anon-impounding embankment fill. The <br />location of the proposed coal waste pile was chosen jointly by CTVT and Twentymile <br />Coal Company based upon volume requirements, location adjacent to portal and <br />• processing equipment, and stability considerations. The pile will be a sidehill fill in <br />p!~ t~.~ a relatively flat area. The 2.8:1 (H:V) maximum slope (3.1:1 average slope with <br />)~i ~ benches) is considered a conservative configuration. Steeper slopes on the order <br />~ W~ ~\~ of 2.5:1 or even 2:1 could be possible. The flatter slopes were chosen to enhance <br />f~~ the stability considering the possible fluctuations in material properties of the coal <br />waste. The conservative slope design is reflected in the results of the stability <br />~ analysis. <br />Stability Analysis <br />StabilRy analysis involved evaluation ofthe geotechnical properties of the coal <br />waste and foundation conditions, a representative cross-section with various <br />soil/waste strengths, and the effects of water and ground accelerations due to <br />~ earthquakes. The section selected for analysis was Section 1 (Figs. 2 and 3). This <br />• section represents the highest slope face. The model analyzed contained three <br />8 <br /> <br />