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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. A minimum 30 foot buffer will be maintained from the property boundary line to all new <br /> excavations. <br /> Due to the long mine life,two differing potentially coexisting slope scenarios are evaluated: <br /> 1. Scenario 1 —Dredge mining <br /> The first portion of the mine's life will involve mining within the existing dredge piles. These piles <br /> are processed glacial and alluvial rock,making it relatively clean of finer silts. The existing piles <br /> have shown long term stability(>50 years) at 1 H:1 V slopes. The reclaimed slopes at this stage will <br /> be 2H:IV. <br /> From Table 2.5 in the SME Mining Reference Handbook',the dredge material is best classified as <br /> sand and gravel, mixed grain size. This material has an internal angle of friction of approximately <br /> 45 degrees and no cohesion. <br /> The Factor of Safety(FOS) for a(2H:IV)26.6 degree slope in sand and gravel with an assumed <br /> internal angle of friction of 45 degrees can be approximated by ignoring the cohesion component of <br /> the stability and simply 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 /> Tan 45' 1.0 <br /> FOS = — 2.0 <br /> Tan 26.60 0.5 <br /> 'Original source:Houk and Bray 1977 <br /> Trout Valley Ranch November 2016 GEO-1 (,re IAwicki and AsmwiAtm 111AA <br />