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GEOTECHNICAL STABILITY EXHIBIT <br /> There are no buildings or any structures outside the permit area which could be affected by the <br /> excavation. Sufficient buffers will be maintained to neighboring property lines. <br /> From Table 2.5 in the SME Mining Reference Handbook', the backfill is best classified as sand <br /> and gravel, mixed grain size. This material has an internal angle of friction of approximately 48 <br /> 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 material with an assumed internal angle of friction of 48 degrees can be approximated by <br /> evaluating the internal angle of friction as follows: <br /> FOS = Tangent of Internal Angle of Friction <br /> Tangent of Actual Angle of Failure Surface <br /> FOS = Tan 48' _ 1.200 — 3.61 <br /> Tan 18.4° 0.3326 <br /> With a safety factor of 3.61, 3H:1 V slopes will be safe as the final condition. <br /> 'i <br /> e <br /> �s <br /> 04 l l 1 Of <br /> NONA <br /> ' Original source: Houk and Bray 1977 <br /> Yevoli Cobblestone Pit GrN I Vicki and Asmwi.tm P1.11' <br /> August 2018 GS-1 <br />