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resulted in no one residing in the dwelling when the dwelling was subsided. This dwelling was a mobile home and <br />• it was moved from the site prior to undermining it. The occupants were relocated to a house on the north side of <br />Fish Creek. <br />The other dwelling, owned by a Twentymile affiliate, currently is housing an employee of TCC. Prior to <br />undermining the house the employee will be given the option of relocating to another dwelling, or remaining in the <br />current dwelling. The employee vacated the dwelling prior to undermining it, so there was no safety issues <br />involved. <br />Additional dwellings lie to the north of Fish Creek in sections 26 and 35 of TSN, R87W. TCC did not subside these <br />structures but did conduct some monitoring of the structure located in section 26. TCC did repair the dwelling in <br />section 26 due to damage resulting from seismic associated with longwall mining. <br />Roads <br />There are several dirt roads that traverse the longwall panels, and these roads were subsided. Local ranchers use <br />these roads or surface owners and access to these roads were limited to those specific owners. No significant <br />impact to the roads resulted from TCC's mining activities. No control plan was contemplated for these roads. <br />County Road 27 <br />TCC plans to subside Routt County Road 27 (CR 27) when longwall mining commences in panels 1~', 2nd and 3'd <br />Southwest Panels. It is anticipated that approximately 5 to 5.5 feet of subsidence will be experienced in panel 1" <br />Southwest and the 2°d Southwest Panel, and subsidence measured at 5.9 feet. The magnitude of subsidence is related <br />to overburden depth, and CR 27 is located in areas where the overburden depth is diminished due to the erosion of the <br />Twentymile Sandstone. TCC relocated a segment of RCR27 to allow for construction of the safety berm on the north <br />• side of the road. <br />TCC enlisted the services of Science Applications International Corporation (SAIC) to conduct a stability <br />investigation of the Twentymile Sandstone cliffthat parallels the county road. Their report is presented in Exhibit 7A. <br />The subsidence control plan for the road is discussed in the following section. <br />In 1994, SubTerra Inc. was contracted to further analyze the stability of the Twentymile Sandstone cliff and develop <br />mitigation measures to protect County Road 27 in the event of structural failure of the cliff face due to subsidence <br />caused by longwall mining. The analysis and mitigation design was based on the Colorado Rockfall Simulation <br />Program (CRSP). SubTerra's scope included field mapping, data collection, data collation and interpretation, CRSP <br />model calibration, failure analysis of the project area using the CRSP model, and engineering and design of the <br />mitigation techniques. SubTerra's report is included as Exhibit 7F. Twentymile Coal Company is committed to <br />provide an as-built certification to the Division upon completion of construction of specified mitigation measures. <br />Yampa Vallev Electric Association Powerlines and Associated Facilities <br />Two powerlines, a 69kv and a 7.2 kv line, were subsided by TCC. A substation located adjacent to County Road 27 <br />also was subsided. Discussions were held with Yampa Valley Electric Association (YVEA), concerning its mining <br />activities, and no significant problems will result from TCC's subsiding the powerlines or substation. <br />The 7.2kv line were inspected periodically by YVEA and they were able to make any repairs or arrange to have the <br />repairs made if so required. TCC coordinated with YVEA to conduct periodic inspections of the substation <br />installation. The substation and associated structures (switch gear, meter, lightning arrestors) serve TCC facilities <br />exclusively and could be quickly isolated from the associated powerlines in the event damage occured due to <br />• subsidence. The structures are built upon small concrete footers. TCC did not see any differential settling causing <br />structural damage to the footers to the degree that the substation facilities themselves were physically damaged. The <br />APPRO!/LD APR 2 4 2 <br />Permit Renewal No. 3 2.05-176 1171/99 <br />