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0 <br />• SCOPE <br />This report presents the results of our Auger Mining Analysis for the West Pit <br />and Streeter Pit and Stability Evaluation for slopes associated wfth the West Pit. The <br />purpose of our investigation was to: <br />1. Provide recommendations for auger mining X-Seam coal in both the <br />West Pit and the Streeter Pit areas. <br />2. Provide recommendations for auger mining the C or D and E-Seams <br />in the West Pit. <br />3. Evaluate the stability of the east, west and north walls of the West Pit <br />for various overall slope angles. <br />The auger mining analysis included recommended auger spacings (web <br />thickness) for various auger sizes, and opinions regarding subsidence, spontaneous <br />combustion, methane, hydrologic concerns and safety. The stability evaluation <br />includes the effects of spoil pile location. Our work was performed in general <br />• conformance with our Proposal No. 95-382, dated May 8, 1995. <br />PREVIOUS INVESTIGATIONS AND REFERENCES <br />Our analyses were based to a significant degree on the results of previous <br />field and laboratory investigations and the experience of Colowyo personnel. The <br />primary reference for geologic conditions and rock properties was the "Report on <br />Preliminary Design of Open Pit Slopes", by W.A. Wahler and Associates, April, 1975. <br />The Wahler report contained the results of drilling, laboratory testing and geologic <br />mapping across the Colowyo site prior to mining. Mr. Ed Moyer and Mr. Gary <br />Rivenes of Colowyo provided considerable information regarding operating <br />condtions in the East Pit and geologic information from the results of reserve <br />evaluation drilling in the West Pit area. A previous study "Auger Mining <br />Implementation", by Norwest Mine Services, Inc., dated October 20, 1993 was also <br />reviewed as part of this investigation. A list of technical references consulted is <br />provided at the end of the report. <br />COLOWYO COAL COMPANY, L. P. <br />crur sa,ses 1 <br />