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GoodMiller #2 Pit 112c Permit <br />The Factor of Safety (FOS) for gravel with a 21 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° .67 <br />FOS = _ = 1.7 <br />Tan 21" .4U <br />This factor of safety far exceeds the normal long term safety factor of 1.3, therefore the plan of <br />extraction, as presented in Figure 2, is acceptable. In addition, the exposed 1.5H:1 V gravel slopes <br />will only be present for a short period of time, since the mine will be conducting contemporaneous <br />reclamation. These backfilled slopes are at a slope of 3H:1 V. The backfilled material will consist <br />of overburden from previously excavated areas or reject fines, which is similar to the overburden. <br />GoodMiller #2 Pit Dec 2014 U -5 <br />