Laserfiche WebLink
Barr Engineering Company <br />4700 West 77th Street • Minneapolis, MN 55435-4803 <br />Phone: 952-832-2600 • Fax: 952-832-2601 • www.barr.com An EEO Employer <br />BARR <br />Minneapolis, MN • Hibbing, MN • Duluth, MN • Ann Arbor, MI . Jefferson City, MO • Bismarck, ND <br />Memorandum <br />To: Chris Nyikos, Project Manager - Mountain Coal Company <br />Cc: Doug Nolte, Engineering Manager - Mountain Coal Company <br />From: Philip Solseng <br />Subject: Stability Analysis of LRP with Preparation Plant <br />Date: 16 September 2009 <br />Project: 06/26-1004 <br />A stability analysis of the Lower Refuse Pile (LRP) with associated loading from the proposed <br />Preparation Plant was performed by Barr Engineering Co. (Barr) on behalf of Mountain Coal Company <br />(MCC). The stability analysis was performed as part of Permit No. C-1980-007 (TR-118). A <br />memorandum summarizing the results of the stability analysis, signed and dated 8 September 2009, was <br />submitted as part of the permit application for TR-118. <br />A letter dated 14 September 2009 was written in response to the TR-118 application by the Colorado <br />Division of Mining, Reclamation, and Safety (CDRMS). In the letter, the following revisions to the <br />stability analysis were requested: <br />Lower cohesion values for the Colluvial Soils (Colluvium) should be used. Values of 0 or 300 psf <br />were suggested rather than 886 psf. <br />2. Higher moist unit weight values for the Coal Waste (Refuse) should be used. A value of 110 pcf <br />was suggested rather than 91.9 pcf. <br />The analysis was performed again with a cohesion value of zero for the Colluvium and a moist unit <br />weight value of 110 pcf for the Refuse. The analysis included the full parametric modeling to account for <br />variable loading from the proposed Preparation Plant facility. The results of the revised analysis are <br />shown graphically in Figures 1-7 (attached). It can be seen in the figures that the factors of safety in <br />general decreased from the original analysis by 0.02 to 0.09 with an average decrease of 0.05. The lowest <br />factor of safety for static conditions at the assumed Preparation Plant foundation loading (4,000 psf) is <br />1.79. Furthermore, the lowest factor of safety is 1.22 at Cross Section A for the more stringent pseudo-