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INTEROFFICE MEMORANDUM <br />Date: 20 December 2012 <br />To: Susan L. Burgmaier, Lead Specialist <br />From: Marcia L. Talvitie, P.E. <br />Subject: Bowie No. 2 Mine —Permit No. C- 1996 -083 <br />TR -76 — Expansion of Coal Mine Waste Pile No. 2 <br />Preliminary Adequacy Review — Engineering/Geotechnical <br />With TR -76, Bowie Resources, LLC (Bowie) seeks to increase the area available for permanent <br />disposal of Coal Mine Waste (CMW, "Gob ") at the Bowie No. 2 Mine. Specifically, Bowie <br />plans to increase the storage height of CMW Disposal Area No. 2 by approximately 80 feet and <br />expand the structure westward to join it with existing CMWDA No. 4. These changes are <br />projected to increase the available CMW storage volume by 600,000 cubic yards. <br />Text in Volume IX has been revised, and a new Buckhorn Geotech stability analysis has been <br />performed for the proposed expansion of CMWDA No. 2. I have identified only two adequacy <br />items for Bowie's response. <br />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 lindicates <br />that a segment of the hillside will be graded back (steepened) to a slope of 1.5H: IV. On <br />Figure 1, Section F -F' shows a cut slope of 2.OH:1V through this area. Section F -F' in <br />the Buckhorn report also depicts 2.OH: IV. Please clarify the intended slope ratio to be <br />cut at this location. <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 />This concludes my adequacy review let me know if you have any questions or comments. <br />