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• mitigation. Specific mitigation measures for potential impacts on power <br />transmission lines and associated facilities are discussed in the <br />subsidence control plan. <br />The City of Florence water line within the permit area was originally <br />constructed using 12 inch diameter clay pipe approximately 100 years ago. <br />Normal deterioration coupled with historic mining and resulting subsidence <br />caused severe leakage in the line, which was replaced and relocated in the <br />early 1980's. The existing diversion pipeline is 12 inch PVC line which <br />follows the alignment shown on the Mine Area Surface and Groundwater <br />Hydrology Map, (Map 12). EFCI's subsidence monitoring and mitigation plans <br />for the water line are presented in the monitoring, and subsidence control <br />plan sections of this revision submittal. <br />RMG's original description of worst case subsidence projections indicated <br />that material damage or diminution of reasonable foreseeable use could <br />result from possible mine subsidence within the permit and adjacent areas. <br />• Consequently, a subsidence survey and subsidence control plan were <br />prepared for the Southfield mining operations. These plans, originally <br />implemented by Dorchester, are being utilized with no significant changes <br />for EFCI's ongoing operations. <br />Subsidence Monitoring Program <br />The purpose of the subsidence monitoring program is to measure surface <br />subsidence and to evaluate the accuracy of subsidence predictions relative <br />to actual ground displacement. The program is designed to yield <br />subsidence data that can be used to evaluate and predict the effects of <br />both development and retreat extraction methods. <br />The subsidence monitoring program developed by RMG in 1983 was prepared <br />in accordance with applicable provisions of Sections 2.05.6 (6) and 4.20 <br />of the Colorado Regulations, and currently is being used by EFCI. This <br />monitoring program effectively meets the operational and regulatory <br />• objectives of subsidence monitoring for the Southfield Mine. Observed <br />subsidence as documented by ongoing monitoring, is comparable to RMG's <br />projections in the initial permit document. EFCI will continue to use the <br />2.05.6-59 <br />