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The Factor of Safety (FOS) for gravel with a 10 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 = 3.8 <br />Tan 10° .1763 <br />This factor of safety far exceeds the normal long terns safety factor of 1.3, therefore the plan of <br />extraction as presented in Figure U-1 is acceptable. <br />I, Greg Lewicki, P.E., with over 28 years of experience in mine slope safety analysis in <br />Colorado, certify that the mine plan and reclamation plan presented in this application will lead <br />to stable slopes during and after mining and that there is no realistic threat of failure or to the <br />stability of any structures outside of the permit area. <br />p'+ *swie?u +7° <br />Greg Lewicki, P.E. <br />caa ?-,? <br />20335 P.E.# 20335 <br />k. <br />Date: ? 14. <br />Moonscape Pit, July 2009 U-2