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• 1.0 INTRODUCTION <br />The Bowie Mine No. 2 is a subsurface coal mine owned and operated by Bowie Kesources, LLC <br />(Bowie). The Bowie Mine No. 2 is located north of Colorado State Highway 133B, <br />approximately 3.5 miles northeast of Paonia, Colorado. The mine produces approximately 5 <br />million tons of coal per yeaz. Coal waste from the prepazation plant as well as some high ash <br />coal is disposed at a coal waste disposal area located immediately north of Colorado State <br />Highway 133B. Buckhorn Geotech, Ina (BGI) was retained by Bowie to evaluate stability of <br />the proposed Coal Waste Disposal Stockpile No. 4 ("Gob Pile No. 4") and provide <br />recommendations for stable excavation and stockpile configurations. We are pleased to present <br />this report summarizing our field investigation, laboratory testing, and stability evaluations. <br />1.1 Scope of Services <br />As part of the stability evaluation for the Gob Pile No. 4, BGI conducted a geotechnical site <br />investigation, laboratory testing, and limiting equilibrium stability analyses. The site <br />investigation included two drilled boreholes at the footprint for Gob Pile No. 4, three drilled <br />boreholes in gob at Gob Pile No. 2, and collection of in-situ samples of coal waste from Gob Pile <br />No. 2 for strength testing. Laboratory testing included index testing to characterize the <br />foundation soils and triaxial testing to characterize strength parameters of the coal waste. <br />Previous UU and CU triaxial shear tests were also used for the stability evaluation. <br />Conventional two-dimensional limiting equilibrium analyses were conducted to evaluate various <br />subgrade excavation configurations and gob configurations. <br />2.0 PROJECT BACKGROUND <br /> <br />2.1 Project Location <br />Gob Pile No. 4 is to be located north of State Highway 133B on the slopes of the North Fork of <br />the Gunnison River valley. The new gob pile will be located immediately west of Gob Pile <br />No. 2, immediately east of Gob Pile No. 1 and north of Topsoil Pile "E". Gob Pile No. 4 will <br />essentially be a western expansion of Gob Pile No. 2. The approximate location of the new gob <br />pile is presented on Drawings 1 and 2 in Appendix A of this report. General locations of Gob <br />Pile No. 4, along with Gob Piles No. 1 and No. 2, are indicated on the photos below. <br />2.2 Site Conditions <br />Slopes of the native ground surface at the Pile No. 4 footprint (prior to disturbance) were <br />approximately 15 to 20 degrees. Slopes above the proposed gob pile steepen to approximately <br />35 to 40 degrees. Bedrock outcrops are observed on the steeper portion of the slope. <br />At the writing of this report, topsoil has been stripped from the Gob Pile No. 4 footprint and <br />stockpiled. The footprint area is serving as a borrow source for native soils to be used as cover <br />material for Gob Pile No. 2 and to mix with gob at Gob Pile No. 2 to reduce moisture content <br />and improve workability. Borrow operations were on-going at the time of the geotechnical site <br />Bowie Gob Pile No. 4 stability report <br />Project #OS-126-GFA <br />Page 4 of I S <br />