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<br />INTEROFFICE MEMORANDUM <br /> <br /> <br />Date: <br /> 04 January 2013 <br /> <br />To: <br /> Susan L. Burgmaier, Lead Specialist <br />From: <br /> Marcia L. Talvitie, P.E. <br /> <br />Subject: <br /> Bowie No. 2 Mine – Permit No. C-1996-083 <br /> TR-76 – Expansion of Coal Mine Waste Pile No. 2 <br /> Review of BRL Adequacy Response – Engineering/Geotechnical <br /> <br />I have reviewed BRL’s recent package, submitted by J.E. Stover & Associates in response to the <br />Division’s December 2012 preliminary adequacy review. Each of my comments has been <br />satisfactorily addressed, as detailed below. <br /> <br />17. There appears to be an inconsistency regarding the steepness of the hillside cut slope that <br />is proposed for a portion of the expansion area. The third paragraph on Page 1indicates <br />that a segment of the hillside will be graded back (steepened) to a slope of 1.5H:1V. On <br />Figure 1, Section F-F’ shows a cut slope of 2.0H:1V through this area. Section F-F’ in <br />the Buckhorn report also depicts 2.0H:1V. Please clarify the intended slope ratio to be <br />cut at this location. <br /> <br />BRL clarified that the differences in the cut slope steepness represent two different <br /> <br />locations. Item resolved. <br /> <br />2. Subdrainage systems for Valley Fill disposal sites are required by Rule 4.09.2(2)(d). An <br />alternative subdrainage system was previously approved by the Division, as allowed by <br />4.10.3(5). Volume IX page 5 of the current application indicates that the subdrain for <br />CMWDA No. 2 will be extended as shown on Figure 2. While there is nothing to <br />prohibit extension of the subdrain, the proposed expansion of the waste pile in this area <br />does not appear to be a valley fill configuration. The Division suggests that construction <br />of a drain to intercept any groundwater seeps identified would be sufficient. <br /> <br />BRL added a note to Figure 2 and Maps 20 and 21-3 which states that the underdrain <br /> <br />will be extended only if seeps are encountered. Item resolved. <br /> <br /> <br />cc: Sandy Brown <br />