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S.ESsf 8Y' <br />~9-95 ;12~55AM ; <br />0 ~~ 303 832 8106:# 31 5 <br />~i:1 ~, <br />~3 `~ ,, <br /> <br />is the first north, room and pillar operation 75o feet to the <br />southwest. This portion of the mine was mined with no pillar <br />extraction. Thirty-one percent of the coal was extracted from <br />this portion of the mine using conventional methods. <br />The permit application contains a safety factor analysis (pillar <br />strength/pillar load) of 1.91. This was assuming a maximum <br />extraction ratio of 50 percent. This stability factor was <br />confirmed by oSM using the Surface Deformation Prediction <br />Computer Model. A calculation of the safety factor considering <br />the actual 31 percent extraction ratio would be 2.5 using the. <br />Holland/Grady Prediction Method. <br />The extent of surface deformation (subsidence) was calculated <br />using the computer model. The coal extraction ratio is set at a <br />lower limit of 75 percent for room and pillar mining. The model <br />will not accept a lower extraction ratio although the actual <br />extraction was 31 percent. The model predicts the zero <br />subsidence line to be located 160 feet from the Tatum home. This <br />would put the Tatum home outside of the zone of influence of <br />subsidence associated with the room and pillar mining in the <br />first north portion of the mine. <br />During the investigation no subsidence features were noted on the <br />ground between the Tatum home and the underground workings. The <br />pasture between the residence and the mine showed no signs of <br />TATU2IIiPT . MIK <br />2 <br /> <br />