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DEL- MONT CONSULTANTS , INC. <br /> ENGINEERING v SURVEYING <br /> 125 Colorado Ave. . Montrose, CO 81401 v (970)249-2251 . (970)249-2342 FAX <br /> www.def-mont.com • service0del-mont.com <br /> GEOTECHNICAL STABILITY EXHIBIT <br /> There are no buildings or any structures outside the permit area that could be affected by <br /> excavation. Sufficient buffers will be maintained to neighboring property liens. <br /> From Table 2.5 in the SME Mining Reference Handbook, backfill is best classified as loose <br /> sand. This material has an internal friction angle of 28-34 degrees and no cohesion. This is <br /> worst case since the material will most likely be a mixture of sand and gravel which has an <br /> internal friction angle of 45-48 degrees and no cohesion. <br /> The Factor of Safety (FOS) for sides of the pit with a(3H:IV) 18.4 degree slope in loose sand <br /> material with an assumed internal angle of friction of 28 degrees can be approximated by <br /> evaluating the internal angle of friction as follows: RECEsVF:r) <br /> Tangent of Internal Angle of Friction <br /> FOS = Tangent of Actual Angle of Failure Surface MAY 2 4 2019 <br /> DIVISION OF RECLAMATION <br /> FOS = Tan28°/Tan 18.4° = 1.60 MINING AND SAFETY <br /> For a gravel/sand mixture which is mostly likely what will be present the FOS would be: <br /> FOS =Tan 45°/Tan 18.4° = 3.00 <br /> The minimum safety factor in the permanent case is 1.5, therefore the 3:1 slopes will be safe as <br /> the final condition for a worst case scenario of sand only. <br /> The nearest identified fault is more than 7 miles to the west. This permit is in an area of low <br /> seismic activity. <br /> o�pp0 LICFNs <br /> Nicholas Barrett Vp�•o., gq.• ccp <br /> PE 42106 9 ' <br /> ? PE 42106 <br /> P 3803 <br /> F ANDQ�' <br />