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!'age 3 <br />Tom Gi 11 i.s <br />Pl,~rch 12, 1981 <br />In my mean of August 12, 1980, I also briefly stated my concerns regarding <br />tl,e stability oP the proposed reclaimed configuration. CWI's amended <br />application, submitted suhsequent to the writing of that earlier memorandum, <br />includes additional simplistic stability analyses of several of the proposed <br />backfilled benches throughout the mine site. These analyses do not satisfy <br />the regulatory requirements of Rule ,9.27.3(3). Further, the original and <br />amended applications both contain a consultant analysis by Xenneth Madearis <br />and Associates r,•hich presents a comparison of the stability of alternative <br />backfilling and reclamation schemes for the orchard Valley mine site. The <br />schemes analyzed are total backfilling, partial backfilling and no backfilling. <br />The analysis does not, however, determine the static factors of safety for <br />any of the analyzed alternatives. It is merely a comparison of their respective <br />stability. <br />CWI should amend its application to include a thorough geotechnical analysis <br />of the proposed reclaimed configuration of the Orchard valley Mine. The <br />static factor of safety of all cut and fill slopes must achieve static factors <br />of safety of 1.3 or greater. In the event that an adequate factor of safety <br />cannot be achieved, it should be the applicant's design objective to obtain <br />the most stable configuration possible. This objective applies whether or <br />not a variance is granted under Rule 2.06.5. In my opinion, an appropriate <br />geotechnical analysis of any proposed reclaimed configuration for the Orchard <br />valley Coal 14ine should include: <br />1. A geotechnical investigation of the site and adjacent areas, such as the <br />apparent landslide mass above the proposed permanent diversion ditch. That <br />investigation should include a subsurface angering and drilling program, <br />precise survey of the site and its critical slope sections, aero <br />photogrammetric analysis, installation and monitoring of appropriate <br />ground i.•ater rmnitoring wells, and the collection and analysis of appropriate <br />samples of bedrock, colluvium and fill materials. <br />CWI's amended application contains examples of boring logs completed by <br />Lincoln-Divore, Inc., and Fox and Associates, Inc. If either consultant <br />completed a thorough analysis of the mine site, the results may comprise an <br />adequate sampling program. <br />2. A thorough d,ascription of Chn ycoloyy and hydroIo9y of the mine site, <br />including a large-scale geologic map, material cross-section profiles <br />and ground water level observations performed during the site investigation. <br />Geologic descriptions should include material classifications, bedding <br />and fracture orientation and tJre frequency (RQD index), as we1I as any <br />observed mass movement artifacts, such as slickensiding. <br />(cont'd) <br />a {:~ I h <br />