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The Slope Stability Drawing Sheet in this section shows a typical case cross section where the <br />planned excavation, permit boundary, water level and other features are shown. This sheet also <br />shows the failure line which would occur assuming that a failure occurred at the permit boundary <br />and the material from the upper part of the slope was deposited on the lower part. This results in a <br />failure angle of 17 degrees. <br />A permanent slope safety factor of 1.3 is desired to prevent damage to any surrounding structures. <br />The Safety factor = tangent of internal angle of friction <br />tangent of the actual angle of material <br />Safety factor =tan 37 deg /tan 17 deg = .7536/.3057 = 2.46 <br />In order to produce a failure to damage a structure, a failure angle of over 37 degrees would have <br />to occur, which is impossible, given the 35 feet horizontal buffer distance on the outside of the <br />excavation to the permit boundary. <br />Based on the above analysis, the slopes presented in the design of this plan, combined with the <br />setbacks outlined, will be easily stable and very conservatively meet the desired slope safety factor <br />of 1.3. I, Greg Lewicki, P.E., with over 20 years of experience in mine slope safety analysis in <br />Colorado, state that Phis is true. <br />o\O~ ~V CE(F~i <br />.w, (~ <br />x' 20335 <br />• : ~. J <br />~~S/pNA ~~G <br />North R-34 Pit 1/07 <br />54 <br />