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INTEROFFICE MEMORANDUM <br />Date: 11 March 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 />As requested, I have reviewed the application for TR -98 prepared by J.E. Stover and Associates on behalf <br />of Bowie Resources, LLC (BRL). With this revision, BRL seeks to increase both the footprint and storage <br />volume of the northeastern portion of "Gob Pile #2 ", a permitted coal mine waste disposal area <br />( CMWDA). Three "borrow' areas are also proposed just east of Gob Pile #2, providing a source of <br />coverfill material to be used in reclamation of the mine's coal mine waste disposal areas. <br />History <br />This CMWDA was originally permitted in 2003, under TR -30. The design of Gob Pile #2, including <br />geometry and surface drainage, was subsequently modified through a number of permitting actions: <br />TR -36, TR -44, TR -56, TR -76, TR -81, and TR -85. <br />With TR -89, relocation of the East and West Diversion Ditches was approved, shifting them further up <br />the slope to create additional available area for the storage of coal mine waste. Based on my review of <br />recent aerial photos of the site, construction of the TR -89 ditch alignments appears to have been <br />completed earlier this winter (2014- 2015). <br />Geotechnical Reports / Stability Analyses <br />1. In a report dated July 29, 2013, submitted with TR -81, BRL's geotechnical consultant analyzed <br />the stability of a proposed expansion of Gob Pile #2. Results for Sections A -A' and F -F' were <br />presented, showing that the minimum static Factor of Safety (FoS) of 1.5 could be achieved. <br />With TR -98, a somewhat different configuration for the pile is being proposed, and although the <br />peak elevation will not change, the thickness of material proposed for placement along the axis <br />of the original valley is increasing (as shown on revised Section E -E' of Volume IX Figure 1). <br />Material parameters utilized in 2013's TR -81 analysis differ slightly from those used in later <br />analyses (for TR -84, MR -171, and TR -94) which were conducted by a different geotechnical <br />consultant. Please analyze the stability of the proposed configuration depicted on Section A -A' <br />of Volume IX Figure 1, to determine whether a minimum static safety factor of 1.5 can be <br />achieved, in accordance with 4.10.4(2). If material properties used in this new analysis differ <br />from those assumed in the recent revisions listed above, please provide a justification for the <br />change, such as the coal mine waste's being blended with coverfill material to reduce the <br />moisture content. <br />