Laserfiche WebLink
XV. Subsidence Control <br />The applicant has predicted that no material damage will result from subsidence. However, numerous <br />structures exist above the mining area. The applicant has presented a subsidence control plan to repair <br />or mitigate damage caused by subsidence for each of the existing structures. Details regarding the <br />subsidence control plan may be found in the approved permit. A brief summary of the subsidence <br />control measures for each structure follows. <br />Countv Road No. 33 <br />When daily monitoring reveals that the asphalt road surface has buckled or been damaged due to <br />subsidence, TCC will temporarily repair the surface using gravel. Once subsidence monitoring <br />indicates that subsidence has ceased, a permanent asphalt overlay or patch will be applied to the <br />damaged road section. This method has successfully been employed during the mining of Longwall <br />panels 9R, 8R, 7R, 6R and SR in the Eastern Mining District. Twentymile Coal Company re-paved <br />segments of Routt County Road No. 33 in the fall of 1999, that had experienced damage due to <br />subsidence of Longwall Panels SR and 6R. <br />Southern Pacific Railroad <br />When daily monitoring indicates the track is damaged or the grade has changed, a slow speed <br />restriction will be instituted. Re-leveling and repair of the track occurred in accordance with <br />mitigation plans required by Southern Pacific Railroad. <br />Havden-Gore Pass Powerline <br />When daily monitoring reveals structural tower damage, TCC will notify power repair crews to <br />stabilize and/or repair the damage. TCC will also notify the utility 30 days prior to undermining, in <br />addition to the Division requirement of 6 months notification of undermining. TCC representatives <br />have held discussions with the utility company and have indicated to DMG that re-routing capabilities <br />and system redundancy will prevent end line user power loss. Ground fault interruption capabilities <br />aze also in place to prevent a downed line from remaining live if it were to fall to the ground or across <br />County Road No. 33. Twentymile Coal Company submitted a letter that confirms that end user power <br />would not be interrupted. This letter has been incorporated into the permit document in exhibit 7D-l . <br />The powerline was subsided without interruption or significant damage to the powerline towers. <br />Power company personnel inspected the powerline after subsidence had occurced and found that <br />deformation of the structures was within company specifications and did not require Twentymile Coal <br />Company to conduct repairs. Information regarding subsidence of the Hayden-Gore powerline can be <br />found in the 1997 and 1998 Subsidence Reports. <br />Existine Residences/Structures <br />Three residences were undermined and subsided during the mining of Eastern Mining District <br />Longwall panels 6R and SR. One residence is occupied year round, one is inhabited on a limited basis, <br />while the third is vacant and owned by Twentymile Coal Company. Twentymile Coal Company has a <br />subsidence agreement with the owner of the residences not owned by Twentymile Coal Company. <br />Twentymile Coal Company has repaired subsidence damage to the smaller residence and replaced the <br />larger residence. Persons living in the larger residence were relocated while mining and structure <br />replacement occurced in the fall of 1999 and spring of 2000. <br />23 <br />