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SUBSIDENCE MONITORING REPORT <br />July-December 1991 <br />Twentymile Coal Company, Foidel Creek Mine <br />This report summarizes the results of the subsidence monitoring <br />program at the Foidel Creek Mine of Twentymile Coal Company for the <br />period from July 1991 through December 1991. Surface subsidence <br />occurred only along the southern end of the B-series profile line. <br />Mining for this reporting period, as well as total mining to date, <br />are shown on the attached map. Twentymile Coal Company mined in <br />the 4 Left longwall panel, the 3 Left gateroad and the 2 Left <br />gateroad during this reporting period. <br />Subsidence monitoring results are tabulated on the attached table. <br />The attached subsidence profiles, one for the A-series points and <br />one for the B-series points, illustrate the total measured <br />subsidence. <br />The ongoing analysis of the subsidence data indicated an error in <br />the pre-mining elevation reported previously for monitoring point <br />A-2. The previously-reported elevation of 6858.9 ft was revised to <br />6862.1 ft in this report. <br />