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AAGAPITO ASSOCIATES, INC. <br /> Mining& Civil Engineers & Geologists <br /> 1536 COLE BOULEVARD CORPORATE HEADQUARTERS <br /> BUILDING 4,SUITE 310 GRAND JUNCTION <br /> LAKEWOOD,CO 80401 970.242.4220 <br /> USA <br /> VOICE 303.271.3750 <br /> www.agapito.com <br /> May 26, 2019 534-49 <br /> Mr. Steve Hinkemeyer <br /> Manager of Engineering and Business Development <br /> Trapper Mining, Inc. <br /> P. O. Box 187 <br /> Craig, CO 81626 <br /> Re: Evaluation of I- and J-Pit Spoil Pile Stability,Trapper Mine <br /> As requested by Trapper Mining, Inc. (Trapper), Agapito Associates, Inc. (AAI) has <br /> completed a geotechnical evaluation of the proposed spoil pile to be constructed in the valley to <br /> the south of the proposed I-Pit East cut and to the north of the J-Pit cut(Figure 1). Highwall mining <br /> holes will be driven from each of the proposed cuts northward, in the F-Seam in the I-Pit and in <br /> the G2-Seam in the J-Pit. A combined 500,000 to 900,000 cubic yards (bank) of spoils will be <br /> removed from the cuts and will be routed to the proposed storage pile for 6-8 years of storage. <br /> Upon completion of surface mining and highwall mining within both pits, the spoils will be <br /> returned to backfill the pits. The storage pile will be constructed in 20-to 40-foot(ft) lifts and will <br /> be 60- to 80-ft high at its thickest on the west side. The overall side slopes of the pile are laid at <br /> approximately 21 degrees(°). Mining of the J-Pit cut may or may not occur;therefore,the ultimate <br /> size of the spoil pile is uncertain. Given the general sloping nature of the terrain to the west and <br /> the presence of weak soils in the foundation, a global stability analysis was necessary to assess <br /> integrity of the spoils over the storage period in support of Trapper's ground control plan. AAI <br /> chose to analyze the tallest possible geometry for the proposed spoil pile for conservatism, with a <br /> maximum height of 80 ft. <br /> The objectives of the study were as follows: <br /> 1. Assess global stability of the proposed spoil piles,through <br /> a. Numerical modeling of slope stability <br /> b. Foundation stability analysis <br /> 2. Recommend remedial measures, as necessary <br /> DISCLAIMER: This report contains professional opinions based on site visits and information provided by the <br /> Owner.AAI makes no warranties, either expressed or implied, as to the accuracy or completeness of the information <br /> contained herein.Identification and control of hazardous conditions are the responsibilities of the Owner. <br /> GEOENGINEERING•MINING ENGINEERING•CIVIL ENGINEERING <br />