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~ ChA~ ; <br />n G~ fe" <br />is R,/3 <br />t At present, no construction activities have occurred at the proposed site except for the <br />improvement of an existing road for access to the work area. This existing road will be covered <br />with waste at the western extreme of the disposal area. the remainder of the road will be left intact <br />for access. Anew stretch of road will be constructed along the toe of the fill and is shown in Figure <br />2.2-6. <br />The topography of the proposed disposal site vanes from essentially level near the toe of the fill <br />to slopes of l V:1.6H along the natural slope of the hillside. The sur6cial soils a the site are of Nihill <br />and Torriorthent series. Available topsoil ranges from 12 inches in the area of the proposed road <br />relocation to 0 inches in the higher elevations of the disposal site, see Figure 4.7-1. Topsoil <br />availability is discussed in Section 4.7. <br />The cross-section shown in Figure 2.2-7a is typical of the design fill. A rotational equilibrium <br />analysis was performed on this fill to determine its factor of safety. This factor of safety assumes <br />cylindrical or circular failure and is based upon the normal method. <br />Figure 2.2-7a details the assumptions made with regard to soils. It was assumed the underlying <br />soil depth varied from a few feet on the steeper slopes to approximately 20 feet at the toe of the <br />waste pile. Conservative soil shear strength values were used in the analysis; cohesive strength of <br />0.0 PSF and an internal angle of friction of 25 degrees. The waste rock will be comprised primarily <br />of buff and gray, fine and medium grained sandstones and gray shales from the Mt. Garfield <br />formation. A cohesive strength of 0.0 PSF and an angle of internal friction of 30 degrees was <br />. assumed for this material. A unit weight of 125 lbs./ft3 was assigned to both soils. <br />As described in Section 4.4.2, there are no observed springs or seeps in the area; and no potential <br />aquifer has been developed in the alluvial 611 of Munger Creek. Because of these conditions and the <br />fact that surface water will be diverted from the site, no seepage conditions were considered. <br />Monitoring well GW-6 was established in alluvial material near the base of the site, see Figure 2.3-5. <br />The minimum factor of safety based upon these assumptions was found to be 1.684. The critical <br />circle for this safety factor is shown in Figure 2.2-7a. A copy of the computer analysis with the <br />assumptions made is included in Appendix N. <br />Ins_~ction <br />The waste rock disposal area will be inspected for stability on a quarterly basis by a qualified <br />engineer. In addition, the area will be inspected during the following critical periods: removal of all <br />organic material, large boulders and topsoil as previously described, installation of surface drainage <br />systems, placement and compaction of fill materials, and during revegetation. <br /> <br />M" Page 2.2 - 11 10-13-00 <br />