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• Potential damage to powerlines in areas of retreat mining can be mitigated <br />by measures conducted both prior to coal extraction and following initial <br />subsidence. Measures which may be conducted prior to coal extraction will <br />include reduction of line tension to allow for anticipated elongation of <br />lines within affected areas. Mitigation measures which can be most <br />effective following initial subsidence will include re-tensioning lines <br />and/or raising or straightening pawerpoles where subsidence has reduced <br />powerline clearances. These measures are commonly utilized and have <br />proven effective in underground mining areas in the eastern portion of the <br />United States. Locations where these mitigation measures may be required <br />can only be estimated based on theoretical predictions at this time. <br />Ongoing monitoring will enable more accurate prediction of the location <br />of potential extension/compression strains, allowing timely mitigative <br />actions. EFCI will work closely with Southern Colorado Power to evaluate <br />subsidence trends and implement appropriate mitigation measures to <br />maintain power transmission capabilities and prevent any material damage <br />or diminution of reasonable foreseeable use. <br />• The Florence waterline has recently been repaired and relocated. Repairs <br />focused on replacement of deteriorated clay pipe with more flexible PVC <br />pipe. Relocation involved eliminating certain high maintenance elevated <br />and gradient sections and shifting overall alignment to avoid areas with <br />extensive abandoned underground mine workings. <br />EFCI will conduct room and pillar mining operations in the vicinity of the <br />waterline as projected on the Mine Plan Map, (Map 17). Because of the <br />depth of the coal, surface subsidence effects are realistically expected <br />to be minimal. No barrier pillars or other special modifications in <br />mining techniques are considered necessary. Specific monitoring measures <br />have been implemented and will continue so long as necessary to insure <br />protection of the waterline. The eight (8) subsidence monitoring <br />monuments depicted on the Mine Plan Map (Map 17) have been and will <br />continue to be monitored quarterly to identify the location, nature, and <br />magnitude of subsidence which could potentially impact the waterline. <br />• <br />2.05.6-65 <br />