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Memo to Michael Cunningham 2 June 15, 2010 <br />Slope Stability Review File No. M-2009-077 <br />Cross Section No. 2 <br />The applicant's cross section was duplicated for verification; no potential failure surfaces with lower <br />safety factors than the applicant's identified critical slip circle were located. The safety factor produced <br />by Galena is slightly higher than that produced by the applicant's formula. Therefore, the accuracy of the <br />applicant's analysis is confirmed (see attached). <br />Cross Section No. 3 <br />The applicant's cross section was duplicated for verification with the addition of the overburden stockpile; <br />no potential failure surfaces with lower safety factors than the applicant's calculated safety factor were <br />located. The safety factor produced by Galena is slightly higher than that produced by the applicant's <br />formula. Therefore, the accuracy of the applicant's analysis is confirmed (see attached). <br />Conclusion <br />The DRMS agrees with the proposed setback from County Road 189 at the Dill Pit. The excavation along <br />the west side of the pit adjacent to County Road 189 must never exceed a slope of 4H:1V, groundwater <br />will not be intercepted at the proposed maximum mining depth of 25 feet and the site soil profile consists <br />of SP-SM (poorly-graded sand and silty sand) with some SP and SM. If groundwater is intercepted <br />shallower than expected and/or the soils differ from the expected profile, the applicant must contact the <br />DRMS immediately and reevaluate the stability analysis based on the corrected information. The permit <br />applicant must understand that any transgression of the sloping criteria will be considered a serious <br />violation of the permit if it is approved and issued. <br />Enclosures