2018-08-10_GENERAL DOCUMENTS - C1982056

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TC notified the utility company 30 days prior to undermining the powerline in addition to the Division's requirement to provide six months notification prior to undermining. TC monitored the powerline structures daily. The powerline was subsided without interruption or significant damage to the powerline towers. Power company personnel inspected the powerline after subsidence had occurred and found that deformation of the structures was within company specifications and did not require Twentymile Coal to conduct repairs. Information regarding subsidence of the Hayden -Gore Pass powerline can be found in the 1997 and 1998 Subsidence Reports. Archer -Hayden, Western Area Power Administration, Tri-State, and Public Service Powerlines A monitoring plan for the Archer -Hayden powerline was approved by the powerline operator and incorporated into Exhibit 7e-7 of the PAP. No significant damage or interruption of power was experienced during the subsidence of the Archer -Hayden, Western Area Power Administration, Tri-State and Public Service powerlines. Twentymile Coal subsided portions of powerlines with Western Mining District Longwall panels 13L, 14L, 15L, 16L, and 17L in Township 5 North, Range 87 West, Sections 23 and 26. Twentymile Coal Company has undermined and subsided powerlines in the EMD and NMD without any significant damage or disruption of service. Twentymile Coal anticipates subsidence at portions of the Yampa Valley Electric Line serving the mine located above the SRT, 6RT and 7RT Longwall panels in sections 15, 14 and 11 in Township 5 North, Range 86 West. Monitoring and control plan are included in the PAP. TC may reroute power in the unlikely event the powerline is temporarily impacted. Once the line is stabilized, power would be restored to the line. Existing Residences/Structures Three residences were undermined and subsided during the mining of Eastern Mining District longwall panels 6R and 5R. One residence is occupied year-round; one is inhabited on a limited basis, while the third was vacant and owned by Twentymile Coal. Twentymile Coal has a subsidence agreement with the owners of the residences not owned by Twentymile Coal. Twentymile repaired subsidence damage to the smaller residence and replaced the larger residence. Persons living in the larger residence were relocated while mining and structure replacement occurred in the fall of 1999 and spring of 2000. Foidel Creek/Middle Creek No specific subsidence control plan is approved for Foidel Creek or Middle Creek. Recommendations presented in Exhibit 7i, Subsidence Effects on Streams, call for channel morphology to be evaluated if headcutting or incising of the channel occurs for more than 400 feet from the point of origin of the headcut. Any mitigation would Foidel Creek Mine 35 August 10, 2018