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<br /> <br /> <br /> 61 C1981-041 RN7 findings <br />control and mitigation plan, upon resumption of mining via the South Portal. The <br />plan will be approved by TGTC, and will be in place prior to mining within the <br />subsidence angle of draw of the gas line. An agreement between PCC and TGTC is <br />included as Appendix 20-9, in Volume 6 of the permit application. The agreement <br />includes the provision that the operator would notify TGTC six months prior to <br />undermining of the gas transmission line. Because no further mining is proposed or <br />approved, this provision is no longer applicable. <br /> <br />Subsidence issues identified in association with PR-02, included updates to the “Man- <br />made Features Map” to include the 345KV Rifle-San Juan transmission line, a house <br />and shop building, and an area of “occasionall y irrigated pastureland”, all within the <br />South Portal mining area. The house and pastureland are on previously undermined <br />areas; the powerline has not been undermined (August 2003). Updated subsidence <br />impact projections were provided in response to Division requests. Projected worst <br />case impact to the occasionally irrigated pastureland is localized dewatering of ponds <br />or ditches due to subsidence cracks, which the operator has committed to repairing if <br />they develop. Foundation floor cracking to the dwelling foundation and shop floor as <br />a result of differential settling were projected worst case impacts for these structures, <br />which were constructed over a previously mined out area. <br /> <br />Worst case impacts to the power line were projected to be minor tilting of transmission <br />towers which could be repaired by shimming under the legs or replacing deformed <br />members, which the operator indicated could be done without disruption of service. <br />Mining beneath the powerline was to be limited to development mining with no <br />secondary extraction, resulting in an extraction rate of 49%. No definitive statement <br />from the powerline owners documenting that potential worst case subsidence damage <br />to the powerline could be repaired without disruption of service was ever submitted. <br />However, South Portal mining operations ceased in 1997, prior to extension of <br />workings to within the subsidence angle of draw associated with the powerline. No <br />further mining within the permit area is proposed or approved. The South Mine <br />Portals were sealed in 2000, and portal entries out-by the seals were backfilled in <br />2007. The possibility of resumption of mining under Permit C -81-041 is essentially <br />nil, and would at minimum require approval of a major permit revision. Stipulation <br />No. 22, previously attached to the permit, had required the operator to submit specific <br />written documentation from the powerline owners prior to mining within the <br />subsidence angle of draw associated with the powerline. Due to the fact that coal <br />extraction operations have ceased and the portals have been sealed and backfilled, the <br />Division finds that Stipulation No. 22 is no longer necessary or applicable, and the <br />stipulation was removed with RN-5 approval. <br /> <br />The Division finds the subsidence control plan, as presented by Powderhorn Coal <br />Company within the permit application document, to be in compliance with the <br />subsidence-related regulations of Rules 2.05.6(6) and 4.20. <br /> <br />On October 31, 2007 the Division issued a proposed decision to approve a Release <br />from Liability of Areas Overlying Underground Workings (SL-3). Upon final