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GEOTECHNICAL STABILITY EXHIBIT <br /> There are no buildings or structures outside the permit area that could be affected by excavation. <br /> Sufficient buffers will be maintained to neighboring property lines. For the purpose of this <br /> stability analysis, only processed material that is backfilled to the final 3H:1 V slope is evaluated. <br /> All other materials and slopes are either short term (active highwall), medium term but excavated <br /> in more stable material (mining slopes at 2H:1 V that are unbackfilled), or gentler sloped <br /> (>3H:1 V). <br /> The material mined at the Alma Placer is an alluvial sand and gravel deposit. This material is <br /> then processed to remove gold. The removal of gold via sluices reduces the fines content of <br /> native alluvium. Therefore, the cohesive properties of the material are reduced. On this basis, <br /> from Table 2.5 in the SME Mining Reference Handbook', the material that most represents the <br /> processed alluvium that will be used in backfilling is sand and gravel (mixed grain size). This <br /> material has a minimum internal angle of friction of 45 degrees and no cohesion. <br /> The Factor of Safety(FOS) for sand and gravel with a(3H:IV) 18.4 degree slope in sand and <br /> gravel with an assumed internal angle of friction of 45 degrees can be approximated by <br /> evaluating the internal angle of friction as follows: <br /> Tangent of Internal Angle of Friction <br /> FOS = Tangent of Actual Angle of Failure Surface <br /> 0 <br /> FOS = Tan = = 3.01 <br /> Tan 18.4° 0.333 <br /> The 3H:1 V slopes will be safe as the final condition. <br /> Ben Langenfeld, P.E. <br /> ' Original source:Houk and Bray 1977 <br /> Alma Placer Mine ,.r�, �T�u►=.�a�s ��t <br /> December 2017 GS-1 <br />