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•- 1~ <br />~~,-Nt?~rd~~ <br />vAY 1 8 19yc <br />SIIHSIDENCE MONITORING REPORT <br />June - December 1991 Mined Lan^ <br />Cyprus Empire Eagle Nine No. 6, E-seam wl~'9Ci0n n~•~,,,~„ <br />1.0 INTRODUCTION <br />This report summarizes the survey schedule for and results of the <br />subsidence monitoring of longwall mining panels in the E-seam at <br />the Cyprus Empire Corporation (CEC) Eagle Mine No. 6 for the period <br />from June 1991 through December 1991. <br />Monitoring point locations are shown on the map titled, "E-seam <br />Longwall Subsidence Monitors". This map sheet also shows mine <br />workings, surface topography and overburden thickness. <br />2.0 MONITORING SCHEDULE <br />Subsidence monitoring was performed in July and November 1991. The <br />July 1991 survey included all of monitoring lines "A", "B", "C", <br />and "D", as well as parts of lines "S", and "T". The November 1991 <br />monitoring survey included all of monitoring lines "A", "B", "C", <br />and "D". Monitoring lines "S", and "T" were not surveyed because <br />the snow depth restricted access to the monitoring point locations. <br />3.0 MINING ADVANCE <br />Monthly longwall mining advance for this reporting period, as well <br />as total mining to date, are shown on the map. Average extraction <br />height during the reporting period was 10 ft. <br />On May 13, 1992, the United Mine Workers Local 1799 began a strike <br />against CEC. This strike continued through this semi-annual <br />reporting period. Mining during this period was limited to that <br />longwall mining necessary to meet mine maintenance requirements. <br />4.0 SUBSIDENCE RESULTS <br />The results of the surveys are presented on the attached tables for <br />each of the monitoring lines. The accuracy specification on the <br />monitoring survey is 0.1 ft. Therefore subsidence values of 0.1 ft <br />or less are not considered significant. <br />No subsidence was noted for perpendicular monitoring lines "A" and <br />"B". The eastern ends of monitoring lines "C", and "D" exhibited <br />subsidence of up to 1.0 ft. <br />The monitoring indicated possible subsidence near the middle points <br />of lines "C" and "D" (see points C7, C8, D6, and D7). This <br />subsidence is anomalous as it is occurring approximately 45 deg <br />ahead of the mining face; 500-ft horizontal distance ahead of the <br />