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✓= b, <br />Huddle,tsut -Bern' <br />1.0 INTRODUCTION <br />As part of their operations, Bowie Resources, LLC currently stockpiles some <br />coverfill on top of gob pile #2 and additional stockpiles are proposed. As part of the <br />design development process, Huddleston -Berry Engineering and Testing, LLC (HBET) <br />was retained by Bowie Resources to evaluate the impacts of stockpiling coverfill on the <br />stability of gob pile #2. <br />1.1 Referenced Documents <br />As pant of our assessment, HBET reviewed the following documents. <br />• klonthly Sumnuuy of Vibrating Wire Piezometers August 2014, Botivie Mine No. <br />2, Coal Waste Disposal Area No. 2 by Buckhorn Geotech, Inc., August 26, 2014 <br />• 11onthly Sunnnaty of Vibrating Wire Piezometers July 2014, Bowie Mine No. 2, <br />Coal Waste Disposal Area No. 2 by Buckhorn Geotech, Inc., August 1, 2014. <br />• Stability Evaluation, Proposed Full Buildout, Gob Pile #2, Bowie No. 2 Mine by <br />Huddleston -Berry Engineering & Testing, LLC for Bowie Resources, LLC, July <br />30, 2014. <br />• Stability Evaluation, Technical Revision #85, Gob Pile #2 Drying Area, Bowie <br />No. 2 Mine by Huddleston -Berry Engineering & Testing, LLC for Bowie <br />Resources, LLC, June 3, 2014. <br />1.2 Scope <br />As discussed above, Bowie Resources, LLC currently stockpiles some coverfill <br />soil on a portion of gob pile #2 and additional coverfill is proposed to be stockpiled on <br />the gob pile. The purpose of our evaluation was to determine the impacts on the existing <br />gob pile #2 associated with stockpiling coverfill on top of the existing pile. The scope of <br />the work included the following components: <br />• Reviewing available data to define engineering parameters, piezometric <br />surface elevation, etc. <br />• Setting up models which represent the existing gob pile #2, existing coverfill <br />stockpile, and proposed coverfill stockpile. <br />• Evaluating the impacts of the coverfill stockpiles to the stability of gob pile #2. <br />The evaluation was completed by a Colorado registered professional engineer in <br />accordance with generally accepted geotechnical engineering practices. This report has <br />been prepared for the exclusive use of Bowie Resources, LLC. <br />2.0 BACKGROUND <br />The available reference documentation indicates that the original geotechnical <br />investigation was completed by Lambert and Associates (Lambert) in 2003 and that <br />placement of coal mine waste at gob pile #2 began in 2004. Additional evaluation of the <br />stability of gob pile #2 was completed by Lambert and Buckhorn Geotech, Inc. <br />(Buckhorn) in 2005. Based upon the results of these analyses, maximum slopes of <br />5H:1 V were specified for gob pile #2. However, this was based upon the assumption that <br />undrained (total stress) conditions would exist within the gob pile. <br />X X2008 ALL PROJECTS 01349 - Bo%%ie Resources. LLC 013.19 -0001 BOA %ic \Iine'\200 - G.o' Gob 2 Co%"Il Stabditj 01349.0001 R091914 doc <br />