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Powerlines <br />Twentymile successfully undermined and subsided the powerlines during the mining of panel 9 Right. The <br />powerlines were monitored per the approved plan; this data is presented in the semi - annual subsidence report. <br />The results of the monitoring show that the lines subsided, but the did not fail or experience foundation failure. <br />This verifies the contention that no impacts will be realized due to undermining and subsiding the lines. <br />The subsidence prediction for powerlines is presented in Exhibit 7E, Prediction of Subsidence, Eastern Expansion <br />of Foidel Creek Mine, prepared by Sub Terra, Inc. in March 1993. As is shown, the subsidence will vary from 0 <br />to 73 inches over the various panels. For panels 4 Right through 9 right, maximum subsidence is 67 inches, while <br />maximum subsidence for panels 2 Right and 3 Right is 73 inches. It should be noted that the mine plan for the <br />Northern Mining District has been revised; this results in locating the powerlines outside the subsided zone. The <br />power lines lie to the west of the mining outside of the projected angle of draw. No impacts are anticipated to <br />these lines during this five -year permit term. <br />The powerlines will be monitored, as described in the subsidence control plan, on the basis of distance from the <br />active longwall mining face to the powerlines. The monitoring will allow for rerouting power in the event the <br />Hayden -Gore Pass (metal structure) is impacted temporarily. Once the line is stabilized, power would be <br />returned to the line. A copy of the subsidence agreement, which includes rerouting power and ground -fault <br />interruption processes, has been forwarded to the Division. <br />The wooden structures supporting the other three powerlines should react the same as the wooden structures <br />undermined and subsided in the Southwest Mining District. The line experienced up to 3.1 feet of subsidence <br />without failure to the line or the pole(s). This line has been visited by the DMG inspector during prior <br />inspections conducted at the mine. The subsidence data for this line is presented in Exhibit 7G, Subsidence <br />40 Report for YVEA Power Poles. <br />The gang switch for the Wolcott Tap - <br />Wolcott 230 KV transmission line was relocated during 1996 to an area <br />outside the mine area. No problems were encountered when the line was subsided by the 9 Right panel. It is <br />anticipated the line will continue to respond to future subsidence. <br />All .R O V'C JUN 2 3 <br />?000 <br />PR 99 -05 2.05 -183 8/27/99 <br />