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To. DRMS Den Page 3 of 5 2017-07-12 22 12 51 (GMT) 13032008630 From Greg Lewicki <br />Geotechnical Stability Exhibit <br />The perrnzugejjt slopes in place at White River City will be 3I-1: IV or shalloiver as shouvn on Map <br />F of the approved. ,permit. <br />From "fable 2.5 in the SME Mining Deference: Handbook', the Nackfill is nest classified as loose <br />sand, mixed grain size. This material has an internal ankle off-riction of approximately 34 degrees <br />and no cohesion. <br />Tlie factor of Safety (FOS) for sand and gravel with a (311:1 V) 18.4 degree slope in loose sand <br />nratenal with an assuaned internal angle of friction of 34 degrees can he approximated by <br />ignoring the cohesion component of the stability and simply evaluating the internal angle of` <br />friction as follows: <br />FOS — Tangent of Internal Angle of Friction — <br />Tangent of Actual Angle of Failure Surface <br />fan 34' 0.6745 <br />Tan 18.4" 0.3326 <br />The pennanent slopes at the White River City Pit Nvill be. stable, and not risk any neig?amning, <br />structures. <br />' C)riginal source: 11oiA and Bray 1977 <br />White River City <br />