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~ICZ <br />• Ms. Cathy Bcgcj <br />January l4, 1992 <br />Page 6 <br />The static factor of safety requved by Rule 4.10.4(2) is 15. Based on the above results, the existing and <br />planned refuse pile wnfiguralion at the Southfield Minc will meet regulatory favor of safety requirements. <br />4.0 Conclusions and RecommendaUoas <br />The above stability analyses were based on data obtained from previous studies conducted for Southfield and <br />reported construction practices for the refuse pile. The mtical parameters in the stability analyses are the <br />assumed strength properties of the refuse material and the groundwater levels within the refuse pile. We <br />understand that an underdrain system has been installed at the base of the pile to control the buildup of water <br />levels. To date, the system appears to be performing well and there are no reports of seeps on the exterior <br />slopes. <br />The strength parameters used for the fine reface material in the stability analyses indicated a frictional material. <br />The values used are typical Cor non-plastic granular material. We understand that there is some variatoon in <br />the characteristic of the coarse and fine refuse depending on normal changes in the geology and mining <br />practices. Therefore, it maybe prudent to sample and test plasticity characteristic of the fine refuse to identify <br />an acceptable range. If high eay content material is encountered in the mining operations, it could be sampled <br />and compared with this range, with seleuive placement in the pile to avoid adverse stability impacts if high <br />plasticity is indicated. <br />• 5.0 Use of Report <br />This report has been prepared Cor the exclusive use of the Southfield Mine for specific application to this <br />project. Within the limits of the schedule and budget [or our work, [his study bas been performed in general <br />accordance with locally accepted geotechnical engineering prauia to provide information for this site. <br />Assumptions relative to subsurface conditions at the site were based on previous reports supplied by Southfield. <br />The subsurface conditions in the portions of the site that were not sampled could vary from the conditions <br />observed in the borings supplied by Southfield. In addition, variations in the surface conditions between the <br />borings and in the groundwater wndilions with time are possble. <br />We hope this meets your needs. If you Gave any questions or require any additional information, please contact <br />us. <br />Sincerely, <br />ACZ oc <br />Patrick Corser, P.E. <br />• <br />Prinapal <br />J ry N~tone/~!~/ <br />Senio~~engineer <br />PGC:ksp <br />attachments <br />