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Goodmiller #2 Pit <br />Figure 2 — Slopes for Analysis at Goodmiller #2 <br />112 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 31 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 31 ° .60 <br />FOS = _ = 1.65 <br />Tan 2U" .364 <br />Using more detailed programs in the analysis, such as Galena or SB SLOPE, the factor of safety <br />still attains a value over 1.3. <br />This factor of safety 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 1.6H: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 />I, Greg Lewicki, P.E., with over 28 year of experience in mine slope safety analysis in Colorado, <br />certify that the mine plan and reclamation plan presented in this application will lead to stable <br />slopes during and after mining and that there is no realistic threat of failure or to the stability of <br />any structures outside of the permit area. <br />Goodmiller #2 Pit Nov 2014 U -5 <br />