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~J As discussed elsewhere, the waterline will be protected from subsidence either by relocating underground or constructing an offset line to bypass any affected portion of the waterline. However, relocation of the 138-Kv powerline was not economically feasible and portions of the powerline were allowed to subside with mitigative measures in place. In actuality no effect of subsidence was noted on the waterline during the mining of LW-1 to LW-5. An analysis of subsidence effects on the 138-kV powerline indicated that some of the pole structures would be affected by the subsidence. The worst possible consequences of subsidence to the power line would be the interruption of power supply to the mine. The consequences of such a power failure would be the same as those experienced in past power failures -the mine would be evacuated of all personnel until the power supply is reestablished and all safety procedures determine that the mine is safe to reenter. There are a total of 28 structures within the permit boundary on the 138-kV powerline. Of this total, 11 structures are in positions where they may be affected by subsidence. The structures are bolted wooden two-pole structures with connecting crossbraces. BME owns the structures and lines and is the only customer served by the powerline. On the north-south leg of the powerline, lwo structures and possibly a third were expected to be affected by longwall subsidence. One structure overlies room-and-pillar area 2 (RP-2). Two structures are within the outline of longwall panels 1 and 2 (LW-1 and LW-2) and initial tilting toward the southwest was expected as the subsidence wave passed them. As subsidence is completed they were expected to return to a vertical or near vertical orientation. The third structure was on the edge of the subsidence. The three structures over the longwall panels, as discussed above, were to be affected in 1987, 1988 and 1989. No tilting of the structures due to longwall mining was observed during active subsidence. Powerline Subsidence Mitigation Power structures that start to tilt due to subsidence will be guyed to prevent excessive tilting. These guys will be constructed to limit the tilt, not to eliminate it. Those structures that undergo a permanent tilt will be examined after all subsidence is complete and evaluated to determine if any further mitiga- tion is necessary. Those poles within the panel outline will undergo a net tilt of approximately zero, and will simply be lowered. Permit Renewal #3 (Rev, 8/99) III-22