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GEOTECHNICAL STABILITY EXHIBIT EXHIBIT U <br />There are no buildings or any structures outside the permit area which could be affected by the <br />excavation. A minimum thirty foot buffer will be maintained from the permit boundary line to all <br />excavations. All reclaimed areas will be restored to relatively flat (5-15%) slopes except for the <br />side slope, which be mined to a 3H: IV and reclaimed to a 3H: IV slope. The surface material of <br />these slopes will be topsoil or wash fines. <br />The side slopes will range from sand-silt-clay with slightly plastic fines to silty gravels, poorly <br />graded gravel-sand-clay. <br />Desk factors <br />In the extremely remote case that a slope failure would occur, if the slope failed up to BLM <br />Access Road (the closest man made structure to the operation), Figure U-1 shows the slope angle <br />that would occur. The horizontal distance from the edge of the excavation to the road is 8 feet. <br />The failure angle would be 13 degrees or 4.2H:1 V. This angle is far milder than normal failure <br />angles in material that gets strength from internal angle of friction. Figure U-2, from Huang, <br />shows typical internal angles of friction for various materials. Assuming that the gravel is <br />classified as GC, clayey gravels, poorly graded gravel - sand - clay, this material has an internal <br />angle of friction of approximately 34 degrees. <br />Craig Ranch Pit, March 2011 U-1