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Dames & Moore <br />• Flatiron Companies <br />May 17, 1982 <br />Page 9 <br />and a 50-foot slope height, the factor of safety against slope failure was <br />analyzed. The results of this analysis are presented on Table 2. This table <br />indicates that in the unlikely event of a fully submerged East Dump slope and <br />the worst shear strength design assumption that the factor of safety will be <br />about 1.6. Under normal operating conditions it is estimated that the factor <br />of safety will be between about 2.4 and 3.7. <br />SWELL FACTOR <br />The most accurate method for determining the swell or bulking factor for <br />a specific material excavation ie to use actual before-and-after volume data <br />determined by field survey. We understand that these data are not yet avail- <br />able for the Bourg Mine. <br />• Alternatively, the swell factor can be evaluated by classifying the <br />subject materials and comparing them to materials for which swell factors <br />have been estimated. The materials being placed in the East Dump have been <br />classified by various simple laboratory tests. The results of these tests are <br />presented in the Attachment. Basically, the materials are silty and clayey <br />sands with some gravel (rock fragments). The sandstones and silts tones found <br />in the lower portions of the overburden are quit-e friable.- <br />Based on our experience with similar materials we estimate that the <br />swell factor for the Bourg site is between 10 and 15 percent. For planning <br />purposes, we recommend that a factor of 10 percent be used until an actual <br />factor can be derived from field measurements. <br />Although density tests were performed in the natural and fill materials, <br />the size and number of tests were too small to be representative in determin- <br />ing the swell factor. <br />• <br />