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t ~_Oa_ ~ gg ~ g :08414 FROt-t ENG. WEST ELY, P7I NE 97C~ 9295C,SG <br />w <br /> <br />Page Eight <br />Mr. Norm Every <br />Mountain Coal Company <br /> <br />F. 9 <br />Hartling lawso~ gr,+paates <br />Both full mitigation alternatives (affecting the entire slide mass) and partial mitigation <br />alteratives (affecting only a portion of the slide mass) were cottsidered_ <br />Results of the evaluation will be found in Table 4.0. <br />5.0 R~eommeudatiotu <br />Based on Tahle 4.0, HLA recommends that MCC seriously look at the option of <br />denatering the bedrock behind the slide using a eombin[tion of horizon[al and vertical <br />wells and look at possibly depressurising the cabbie zone near the toe of the slide with <br />horizontal wells. This would both attack the sower of the slide and relieve the pressure <br />that occurs in the cobble zone under the slide in the spring. If MCC wishes to proceed <br />with this optionloptioas then a set of plate could be developed showing drill layouts for <br />this option and a contractor could tx obtained and get started and get completed this Fall. <br />Also a tieback system utilising both extending the existing buttress to the west to protect <br />the existing stack tubes and a possib]e tieback system to the east ot'the buttress should be <br />designed az a optional item to WL"M az they have proved to be very effective and can act <br />az a fallback if dewatering did not stop this landslide. if you have any questions, please <br />give me a call- <br />Sincerely. <br />HARDIIYG LAWSO ASSOCIATES <br />Charles C. Rehn, P.E. <br />Salt Lake City Principal Enginee_ <br />~'l~. .a <br />.~ -~ <br />Ken Myers, P.E. <br />Mines Group, Reno, Nevada <br />Fsrclosure <br /> <br />