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Powerline Subsidence Mitigation <br />Power structures start to tilt due to subsidence will be guyed for added support. These guys would be <br />to support the tilt, not to eliminate it. Structures that retain a permanent tilt will be examined after <br />subsidence is complete and evaluated to determine if any further mitigation is necessary. Those poles <br />within the panel outline will undergo a net tilt of approximately zero, and will simply be lowered. <br />Powerline Monitoring <br />Power structures in areas of active subsidence were monitored periodically until essentially all residual <br />subsidence was complete. No problems were identified. Future monitoring of the powerline due to <br />subsidence concerns is no longer warranted. <br />III.A.7.1 Subsidence Monitoring Program. subsidence related impacts to selected archeological <br />sites will be monitored. The monitoring plan agreed to by BME is included in Section II.A. <br />As part of the initial mine development a program was designed to provide subsidence data to verify <br />the accuracy of initial predictions under actual ground conditions, and which could predict future effects <br />after monitoring the first longwall and the first room and pillar panel. <br />BME monitored subsidence over the first longwall panel (LW1) using state -of- the -art analytical <br />photogrammetry. LW1 was mined in calendar year 1987 and the first two months in 1988. <br />Four flights recorded the surface over LW1. The first flight was flown during August, 1986 to establish <br />baseline conditions and base drawings for both LW1 and RP5 for comparison with the future flights. <br />The second and third flights occurred in May 1987 and September 1987. Data and drawings from <br />these flights were presented to Colorado Mined Land Reclamation Division (CMLRD), now DRMS, in a <br />report in December, 1987 for review. The fourth flight occurred in June, 1988. The fourth flight <br />information and drawings were assembled into a final report and presented to DMG in October, 1988. <br />Residual subsidence may occur after June, 1988, above panel LW1. It is important, for purposes of <br />verifying the accuracy of subsidence projections contained within the permit document, to accurately <br />document the magnitude of subsidence which occurs above this test panel. Conventional semi - annual <br />survey monitoring of the five control points located within the zone of subsidence (see description <br />below) continued until cessation of subsidence was accurately documented. In the event that any of <br />these conventional survey monuments experienced more than 1.0 foot of residual subsidence, an <br />additional aerial photographic flight, subsidence map and report would have been prepared for <br />Permit Revision #8 (06/2013) III -22 <br />