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INTEROFFICE MEMORANDUM <br />Date: 06 November 2014 <br /> <br />To: Susan L. Burgmaier, Lead Specialist <br /> <br />From: Marcia L. Talvitie, P.E. <br />Subject: Bowie No. 2 Mine (Permit No. C-1996-083) <br /> TR-94 Material Storage Area on Gob Pile #2 <br /> Adequacy Review – Geotechnical <br /> <br />As requested, I have reviewed the TR-94 application submitted by J.E. Stover & Associates on behalf of <br />Bowie Resources (BRL). With TR-94, BRL proposes to stockpile Coverfill material on the outslope of Gob <br />Pile #2. The application includes a Stability Evaluation performed by Huddleston-Berry Engineering & <br />Testing (HBET). <br /> <br />HBET’s evaluation determined that the requisite Static Factor of Safety of 1.5 can be maintained, <br />assuming that pore pressures (as measured by Vibrating Wire Piezometers already installed) do not rise <br />significantly. I do, however, have a few comments that should be addressed. <br /> <br />1. The configuration of the Proposed Coverfill Stockpile is provided graphically on Figure 1 of the <br />HBET document. Based on the contour spacing, it appears that an outslope of approximately <br />2h:1v is being proposed. However, neither the revised permit text nor HBET’s report describe <br />the proposed configuration of the coverfill. Please revise the permit text to describe <br />approximate dimensions (width and height), outslope, and volume for the Proposed Coverfill <br />Stockpile. <br /> <br />2. Please revise HBET Figure 1 to show the locations of the various VWP installations; HBET’s study <br />refers to the piezometers, and depicting their locations will add clarity to the report. <br /> <br />3. The Pore Pressures subsection of HBET’s evaluation (page 5) speaks to “increases” in pore <br />pressures that would be necessary in order to reduce the Factor of Safety to less than 1.5. <br />These numbers fail to inform the reader unless the reader knows the pressures in existence at <br />the time of writing. Please revise this section to identify the actual pore pressures likely to <br />result in the Factor of Safety being reduced below 1.5. <br />This concludes my adequacy review for TR-94. Please let me know if you have any follow-up questions. <br /> <br /> <br />Cc: Dan Hernandez, DRMS <br />