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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 45 <br /> degrees and no cohesion. <br /> The Factor of Safety(FOS)for sand and gravel with a (3HAV) 18.4 degree slope in loose sand <br /> material with an assumed internal angle of friction of 34 degrees can be approximated by <br /> evaluating the internal angle of friction as follows: <br /> FOS <br /> Tangent of Internal Angle of Friction <br /> = <br /> Tangent of Actual Angle of Failure Surface <br /> Tan 34° 0.6745 <br /> FOS = _ = 2.02 <br /> Tan 18.40 0.3326 <br /> The minimum safety factor in the permanent case is 1.5, therefore the 3H:1V slopes will b afe <br /> as the final condition. <br /> S n <br /> •� \tee• <br /> Ben Langenfeld, P.E. °-' 0047151 <br /> fil• <br /> �J a e <br /> P.E.#0047151 aa'c� <br /> AL <br /> Date: <br /> Base Products Gravel Pit 2 Lewicki&Associates <br /> April 2022 <br />