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In 1998/99, TransColorado Gas Transmission Company (TGTC) installed a gas transmission <br />line across a portion of the permit area, within a portion of the South Portals mine area which <br />would possibly be undermined in the future. The operator has committed within the permit <br />application to develop a subsidence survey or control and mitigation plan, upon resumption of <br />mining via [he South Portal. The plan will be approved by TGTC, and will be in place prior <br />to mining within the subsidence angle of draw of the gas line. An agreement between PCC and <br />TGTC is included as Appendix 20-9, in Volume 6 of the permit application. The agreement <br />includes the provision that Powderhorn would notify TGTC six months prior to undermining <br />of the gas transmission line. <br />Subsidence issues identified in association with PR-02, included updates to the "Man-made Features <br />Map" to include the 34~KV Rifle-San Juan transmission line, a house and shop building, and an area <br />of "occasionally irrigated pastureland", all within the South Portal mining area. The house and <br />pastureland are on previously undermined areas; the powerline has not yet been undermined <br />(January, 2000). Updated subsidence impact projections were provided in response to Division <br />requests. Projected worst case impact to the occasionally irrigated pastureland is localized <br />dewatering of ponds or ditches due to subsidence cracks, which the operator has committed to <br />repairing if they develop. Foundation floor cracking to the dwelling foundation and shop floor <br />as a result of differential settling were projected worst case impacts for these structures, which <br />were constructed over a previously mined out area. <br />Worst case impacts to the power line are projected to be minor tilting of transmission towers <br />which could be repaired by shimming under the legs or replacing deformed members, which <br />the operator indicates could be done without disruption of service. Mining beneath the <br />powerline would be limited to development mining with no secondary extraction, resulting in <br />an extraction rate of 49%. As of January, 2000, no definitive statement from the powerline <br />owners documenting that potential worst case subsidence damage to the powerline could be <br />repaired without disruption of service has been submitted. The following stipulation remains <br />in effect. <br />Stipulation No. 22 <br />AT LEAST 120 DAYS PRIOR TO IMTIATION OF COAL EXTRACTION WHICH COULD <br />POTENTIALLY CAUSE SUBSIDENCE DAMAGE TO THE 345 KV RIFLE-SAIY JUAN <br />POWERLINE, THE PERMITTEE WILL SUBMIT WRITTEN STATEMENTS FROM THE <br />OWNERS OF THE POWERLINE WHICH INDICATE THAT POTENTIAL WORST CASE <br />SUBSIDENCE DAMAGE TO THE POWERLINE COULD BE REPAIRED WITHOUT <br />DISRUPTION OF SERVICE. NO MINING WHICH COULD AFFECT THE POWERLINE <br />BASED ON PROJECTED SUBSIDENCE ANGLE OF DRAW SHALL OCCUR PRIOR TO <br />DMG'S WRITTEN NOTICE OF COMPLIANCE WITH THIS STIPULATION. <br />With the acceptance of Stipulation No.22, the subsidence control plan, as presented by Powderhom <br />Coal Company within the amended application documents, is found to be in compliance with the <br />subsidence-related regulations of Rules 2.05.6(6) and 4.20. <br />46 <br />