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Placement of additional coal waste shall commence from the bottom and proceed up the slope. <br />Additional coal waste must be keyed or benched into the existing (previously placed) coal <br />waste. The vertical cut for each key into the existing coal waste should be on the order of 4 to <br />6 feet high. Keying the additional coal mine waste into the existing waste will eliminate a <br />potentially weak surface along the previous and newly placed waste. If any zones of seepage <br />are encountered during the benching/keying operations, we recommend construction of a <br />gravel drain to allow drainage and relieve pore pressures. Care should be taken during fill <br />placement, keying and benching to not damage the vibrating wire piezometers or inclinometers <br />installed at the CWDA. The piezometers have cables that are routed through the coal waste to <br />the bench located 50 feet above the toe of the waste bank. <br />We recommend on-going monitoring of piezometers and inclinometers on roughly a quarterly <br />basis. Depending on the rate of coal waste placement, it may be warranted to monitor <br />piezometers more frequently. Monitoring of pore pressures and waste deformation allow for <br />verifying the results of this stability evaluation as~well as a better characterization of the <br />behavior of coal waste at Bowie's No. 2 mine. <br />Proper management of coal waste moisture content during placement will reduce the pore <br />pressures within the fill and enhance stability. As practical, waste materials in excess of the <br />optimum moisture content should be allowed to dry prior to placement. Blending wet material <br />with drier material may also prove to be an effective moisture content management strategy. <br />• 7.0 REFERENCES <br />Buckhorn Geotech, Inc. (BGI), 2006. 'Geotechnical Report Stability Evaluation of Coal Waste <br />Disposal Area, Bowie No. 2 Mine, Delta County, Colorado", Professional Report dated <br />February 15, 2006. <br />Colorado Division of Reclamation Mining and Safety (DRMS), 2005. "Regulations of the <br />Colorado Mined Land Reclamation Board for Coal Mining", Denver, Colorado, Revised <br />September 14, 2005. <br />Colorado Division of Minerals and Geology (DMG), 2006. ~~Bowie No. 2 Mine, Permit No. C-96- <br />083, Bowie Resources LLC, Technical Revision No. 42, Revised Gob Pile No. 2 Stability <br />Report", letter from DMG to Bowie Resources LLC dated April 3, 2006. <br />J.E. Stover and Associates, 2003. "Bowie Resources Limited, Coal Mine Waste Disposal Area <br />No. 2, Detailed Design, Construction, Operation, and Reclamation Plan", dated <br />November 12, 2003. <br />Lambert and Associates, 2003. °Geotechnical Engineering Study, Bowie #2 Mine, Gob Pile, <br />Paonia, Colorado", professional report dated November 10, 2003. <br />Lambert and Associates, 2005. "Geotechnical Engineering Study, Bowie #2 Mine Gob Pile, <br />Paonia, Colorodo", professional report dated March 17, 2005. <br />• <br />Bowie No 2 2008 Reevalution of Coal Mine Waste Stability.doc <br />Project #OS-126-GEO <br />Page 14 of 15 <br />