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INTEROFFICE MEMORANDUM <br />Date: 09 June 2015 <br />From: Marcia L. Talvitie, P.E. <br />To: Jason D. Musick, Lead Specialist <br />Subject: Bowie No. 2 Mine (Permit No. C-1996-083) <br />TR -98 Gob Pile No. 2 — Footprint Enlarged and Borrow Areas <br />Third Adequacy Review— Engineering & Geotechnical <br />I have reviewed the June 8, 2015 adequacy response #2 for TR -98 prepared by J.E. Stover and Associates <br />on behalf of Bowie Resources, LLC (BRL). My remaining adequacy comments (and the number assigned <br />in the Division's adequacy review to BRL) are repeated below, and are updated to reflect my review of <br />the revised information. <br />1 (9) DRMS 03/11: Please update the Table of Contents to show pagination changes resulting from <br />TR -98. <br />DRMS 05/26: The Volume IX ToC was updated as requested. However, the date of the TR -98 <br />HBET analysis appears as July 15 rather than July 30, 2014. Please revise the date accordingly <br />both at this location and on revised Volume I ToC page xiii. <br />DRMS 06/09: 1 did not review this portion of the adequacy response. <br />4 (12) DRMS 03/11: Page 5 has been revised to include the East and North expansion proposed under <br />TR -98. The text indicates that no extension of the underdrain is necessary for East and North <br />expansion. According to Section A -A' (Figure 1), the pile is being extending further up valley. <br />Please explain why no extension is necessary. <br />DRMS 05/26: Figure 2 and Map 21-3 were revised to show the extension of the underdrain up <br />the valley, as requested; however, the text on the map directs that the extension will be made <br />only if seeps are encountered. This zone of Gob Pile #2 qualifies as a Valley Fill configuration, <br />bringing the requirements of Rule 4.09.2 into play. Subsection (2) of this rule requires that <br />subdrainage systems shall be constructed along the natural drainage system, from the toe to the <br />head of the fill. (Any associated lateral drains are to be constructed if areas of seepage are <br />found.) Please revise the map text to show that the underdrain will be extended, as required. <br />DRMS 06/09: The June 8, 2015 adequacy response provides a number of arguments against the <br />likelihood of any ground water being present in the colluvium beneath the proposed northward <br />expansion of Gob Pile #2. Based on the steepness of the natural channel, the lack of any <br />discharge from the constructed portions of the underdrain, the presence of a massive sandstone <br />outcrop immediately uphill from the gob pile, and the dip of the strata being northward (away <br />from the drainage), I believe that the requirement of 4.09.2(2) can safely be waived for the <br />upper reaches of Gob Pile #2. <br />This concludes my third adequacy review of TR -98. All of my items have been satisfactorily addressed. <br />Please contact me with any questions you may have. <br />Cc: Dan Hernandez, DRMS <br />