2014-03-06_REVISION - C1996083 (3)

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Bowie No. 2 Mine C 1996083 Technical Revision No. 84- Second Adequacy Review Page 4 of 15 be 2.92 cfs. Adding that to Drainage Area D (3.47 cfs), W Diversion Ditch #1 (4.44 cfs) and the Mine Water Discharge (0.5 cfs) indicates a total flow of 11.33 cfs. Please verify the flow value used for the 1% segment of the East Clean Water Diversion and revise the channel size accordingly. 31. Response accepted. BRL provided the requested design information for Culvert H1. 32. Buckhorn's response, while it does include a single block failure analysis, fails to make a compelling argument for excluding total strength (Undrained) conditions from consideration and does not discuss the dissipation (or lack thereof) of pore pressures. The Mar -2007 Buckhorn report is the stability analysis for Gob Pile #3 currently approved in the permit, and any proposed changes to the models and variables evaluated in that report should be accompanied by a thorough rationale that references the original study and incorporates any new information. Please address the requirements of Rule 4.10.4(2) (minimum static factor of safety of 1.5) for the proposed reconfiguration of Gob Pile #3 including a consideration of undrained conditions resulting from a lack of dissipation of pore pressures. Alternatively, a detailed rationale supporting elimination of Undrained analyses from consideration may be provided. 33. Buckhorn's response focused exclusively on the compaction aspect of this item (the Division agrees that the required compaction is being achieved), but failed to address the issues of undrained shear strength and elevated pore pressures. These topics of concern are addressed in greater detail in the attached 25- Feb -2014 Memo and Summary that was also transmitted to BRL under TR -85. As requested in Item 32, above, BRL needs to provide a stability analysis for the proposed modifications to Gob Pile #3 that considers undrained conditions, or justifies their being excluded from consideration. 34. A copy of the 26 -Oct -2006 Buckhorn report was provided with the Feb -2014 adequacy response. The Division's permitting records indicate that this report was submitted with the original TR -45 application, which was deemed Incomplete. The 29- Mar -2007 report, which included a site investigation, was submitted later (effectively replacing the earlier version) and was subsequently approved as part of the permit. The Division recommends that the Oct -2006 report not be included in the permit, and that the permit text not reference that particular study. Our original comment was in error regarding the Mar -2007 Buckhorn report's referencing of the Oct -2006 report. Instead, Buckhorn's list of references included a 15- Feb -2006 stability evaluation. That analysis was prepared for TR -42, which was later withdrawn. As discussed in the TR -85 review process, information provided in the 15- Feb -2006 Buckhorn report is foundational to a number of the later analyses. Because that report (Feb -2006) was prepared to address Gob Pile #2, it should be incorporated into Volume IX of the permit. BRL has proposed, under TR85, to include the 15- Feb -2006 report in Volume IX. Therefore, this item is resolved. Revised Maps 35. Map 15 -1 Mine Facilities: Response accepted. Items a -e were resolved with revised Map 15 -1. 36. Response accepted. BRL revised the map as requested. 37. Response accepted. BRL revised the map as requested. a. New Item — Map 18, both the revised version and the currently approved version, include a purple line (one long two short pattern) that is not identified in the legend. Please revise the map legend to include the unidentified purple line. CIRCES Cost Estimating Soffi are