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GoodMiller #2 Pit 112c Permit <br />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 20 foot buffer will be maintained from the permit boundary line to all <br />excavations. All reclaimed areas will be restored to relatively flat ( <3.5 %) slopes except for the <br />side slope, which be mined to a 1.5H:1 V and reclaimed to a 3H:1 V slope. The surface material of <br />these slopes will be topsoil. During placement of the backfill material, the operator will compact <br />using standard earthmoving techniques. <br />The soil type of the overburden and waste fines used in the backfilling of the side slopes will range <br />from sand - silt -clay with slightly plastic fines to inorganic silts and clayed silts. <br />Design factors <br />In the extremely remote case that a slope failure would occur, if the slope failed up to the overhead <br />power line east of the permit area (the closest man made structure to the operation), Figure 2 shows <br />the slope angle that would occur. The horizontal distance from the edge of the excavation to the <br />power line is 20 feet. The failure angle would be 21 degrees or 2.51-1:1V. This angle is far milder <br />than normal failure angles in material that gets strength from internal angle of friction. Figure 1, <br />from Huang, shows typical internal angles of friction for various Aggregates, Inc.. Assuming that <br />the gravel is classified as GC, clayey gravels, poorly graded gravel — sand - clay, this material has <br />an internal angle of friction of approximately 34 degrees. <br />GoodMiller #2 Pit Dec 2014 U -3 <br />