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The Factor of Safety (FOS) for gravel with an 8 degree slope in GC classified material with an <br />assumed internal angle of friction of 34 degrees can be approximated by ignoring the cohesion <br />component of the stability and simply evaluating the internal angle of friction as follows: <br />FOS = <br />Tangent of Internal Angle of Friction <br />Tangent of Actual Angle of Failure Surface <br />Tan 34° .6745 <br />FOS = 4.8 <br />Tan 8° .1405 <br />This factor of safety far exceed the normal long term safety factor of 1.3, therefore, the plan of <br />extraction, as presented in Figure U-1, is acceptable. In addition, the exposed 1.51-1: IV gravel <br />slopes will only be present for a short period of time, since the mine will be conducting <br />contemporaneous reclamation. These backfilled slopes are at a slope of 3H:1 V. The backfilled <br />material will consist of overburden from previously excavated areas or reject fides, which is <br />similar to the overburden. <br />Simmons Pit, March 2009 U-2