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• shear tests for this investigation. Tests for this investigation were performed <br />on California liner samples (2 tests) and on remolded samples of the <br />composite Shelby tube samples at two different densities and moisture <br />contents (Appendix B). The results of all the previous and current tesls are <br />fairly consistent. The results also compare well with minimum and average <br />values from the Mining Enforcement and Safety Administration (MESA) <br />manual, Reference 15. <br />The results are shown on Fig. 5 and provide a basis from which typical <br />or minimum strength estimates can be made. The normal strength value used <br />in our current stability analysis (m = 32 degrees and Cohesion = 200 <br />psf) is shown on the plot. <br />• Summary of Existing RDA Conditions <br />The information we obtained regarding initial site preparation procedures <br />(including stripping of overburden soils near the toe, keyway buttress construction, <br />drain installation and cover on the face) indicates they were performed adequately. <br />These conclusions are based primarily upon discussions with the contractor and <br />previous mine manager but were also confirmed to a degree by the results of the <br />exploratory borings. The borings found 4 feet of clay cover on the benches and did <br />not encounter an extensive soil layer below the RDA. Compaction of the refuse <br />appears to be inconsistent prior to 1992. The subsequent testing and investigations <br />indicate conditions have improved and satisfactory compaction has been achieved <br />since 1992. <br />• <br />15 <br />