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• ENGINEERING ANALYSIS AND RECONIMENDATION5 <br />SITE GRADING <br />Preliminary site grading plans were available at the time of our study and were used to <br />locate boreholes and target depths. We anticipate site grading to be extensive. In order to <br />minimize settlement in embankment fills, we recommend the use of modified Proctor moisture- <br />density compaction criteria (ASTM D155~. The fills will generally have higher shear strength <br />and lower moisture content than fills compacted using standard Proctor criteria. The fills will <br />also be more similar to the native soils, which are relatively dry and high strength. The <br />drewback to using modified Proctor criteria is that the fi]Is will also be sensitive to volume <br />increase upon wetting. Considering the use of this site as a mine facility, where surface <br />• drainage can be controlled, this should not be a problem unless wet benefication processes are <br />used that can wet large areas of the subsurface. <br />Slope stability analysis was performed using computer modeling of the previously planned <br />cut slopes and generalized subsurface strength parameters determined from our study. Slope <br />sections in the portal bench area generated factors of safety in the Lange of 1.2 to 1.4, <br />considered marginal [o acceptable for a project of this type. Based on our experience in this <br />area, and these results, we have modified slightly the recommended cut and fill slopes for this <br />project. Based on the conditions identified at this site, we recommend the following: <br />Site Preparation: The following recommendations should be followed For site preparation. <br />(1) Permanent cut slopes should be no steeper than 2:1 (horizontal to vertical) overall, <br />including benches. Although, for areas where the owner can accept an increased risk of <br />i <br />• 13 <br />