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The refuse disposal area is underlain primarily by the main entries, however, <br />some portions of the refuse area are underlain by sub - mains. Mining under the <br />main entries was accomplished in two (2) phases. The first phase consisted of <br />development mining. No evidence of subsidence was observed by EFCI in areas <br />where the development phase of mining was completed. The second phase <br />consisted of pillar extraction or retreat mining which approximates extraction <br />conditions for longwall mining. This phase resulted in some subsidence, impacts <br />of which are discussed under the subtitle, "Subsidence Control Plan" later in this <br />section. Impacts to the refuse pile were minimal as detailed in the semi - annual <br />subsidence monitoring reports. <br />Freshwater Pond No. 3 was a partially incised pond located above the main <br />entries. The pond was removed and the associated disturbance area reclaimed in <br />conjunction with mine closure and final reclamation activities. <br />Sedimentation Pond No. 4 is located outside the limits of mining. Although the <br />angle of draw, predicted by RMG to be between 20 to 25 degrees, could extend <br />to the pond area, the magnitude of actual subsidence was not significant and did <br />not result in any impacts to this structure. <br />The possibility existed for power poles and substations within angle of draw limits <br />to be unevenly influenced. Subsidence can reduce electrical clearance due to <br />tilting, and /or vertical displacement. Resulting strains in the powerlines would, in <br />the opinion of officials from Southern Colorado Power who maintain the line, <br />exceed safe limits for the lines. This could possibly result in material damage <br />requiring immediate mitigation. Specific mitigation measures for potential impacts <br />on power transmission lines and associated facilities were developed but were <br />never implemented, as no significant impacts occurred. Most of the potentially <br />affected powerlines were removed during final mine reclamation. <br />The City of Florence waterline within the permit area was originally constructed <br />using 12 -inch diameter clay pipe approximately 100 years ago. Normal <br />deterioration, coupled with historic mining and resulting subsidence caused <br />severe leakage in the line, which was replaced and relocated in the early 1980's. <br />The existing supply pipeline is a 12 -inch PVC line that falls within the County Road <br />15 easement, where it crosses the permit area. <br />TR -36 2.05.6 -58 Revised - October 2003 <br />