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<br />Auger Spacings <br />The results of the auger spacing (web width) calculations are shown on <br />Tables A-1 through A-V. The maximum overburden depth and type of condition <br />(uniform or increasing overburden depth with penetration) is also indicated. <br />Extraction ratios were based upon the full seam thickness. The recommendations <br />for auger spacing vary according to seam, location and penetration. The spacings <br />are dependant on overburden depths derived from the mine plan information <br />available at the time of this report. Prior to beginning each auger phase, we <br />recommend the overburden conditions (assumptions shown on Tables A-II through <br />A-V) be checked to confirm the assumptions regarding overburden depth remain <br />valid. The equations shown on Fig. A-3 can be used to develop web widths for <br />different overburden thicknesses. Figure A-5 shows calculated web widths for <br />various thicknesses of bedrock overburden. <br />• The interburden between seams C and D is relatively thin and auger mining <br />of efther, but not both of these seams is recommended. We considered ways in <br />which smaller auger holes could be aligned in the D-Seam below previously angered <br />holes in the C-Seam. Extraction ratios would be considerably reduced and safety <br />complications introduced which we believe make auger mining both seams <br />unfeasible. <br />As previously discussed the rectangular auger method recommendations are <br />considered preliminary. Additional considerations regarding the depths of <br />penetration and roof stability considerations would need to be addressed prior to <br />implementing this method. Additional investigation consisting of coring of roof rock <br />and mapping of roof conditions in the East Pit should be performed to better <br />evaluate the feasibility of this mining method. <br /> <br />COLOWYO COAL COMPANY, L. P. <br />CTLT 2J,585 7 <br />