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:~ iii iiiiiiiiiiiii iii , STATE OF COLORADO MINED LAND RECLAMATION DIVISION Department o} Natural Resources 1313 Sherman S[., Room 21 S Denver. CO 80203 303 866-3567 Fnx: 303 832.8106 June 17, 1991 Mr, Terrell Johnson Cyprus Empire Corporation P.O. Box 68 Craig, Colorado 81626 RE: Preliminary Ad eauacy Review, TR-19, Permit C-81-044 Dear Mr. Johnson: pF Cpl R~~ ~~ HOB *«~~y~' a ~ /ele ~ Ray Romer. Governor Fred R. Banta. Drvis~on Director The Division has completed the preliminary adequacy review of TR-19 for CEC's Eagle No. 6 mine. The revision proposes to allow development mining only under structures and renewahle resource lands. Spec ificall.y, CEC is requesting permission to extend its mains and submains beneath the Denver Rio Grande and Western Railroad spur, Colorado State Highway No. 13, and the Williams fork River and its associated alluvial valley floor, during its present five year mining permit term, The Division has reviewed and concurs with the subsidence calculations and predictions presented with the application. As a portion of the permit revision application CEC proposed to monitor the performance of the underground pillars which might present a hazard within the mine. However, the requirement to monitor subsidence could extend beyond the closure of the underground workings, at which point access to the pillars would no longer be possible. Further, it is also of value to verify the surface stability of the potentially affected structures and renewable resource lands separate from the effects of subsidence. In previous cases at other mines in Colorado, monitoring has detected factors other than subsidence affecting the stability of structures and renewable resource lands. For the above stated reasons, the Division would request that eight single subsidence monitoring monuments be installed at the following locations Adjacent to Colorado Highway No. 13 above each submain. Adjacent to DRW&W Railroad spur and the mine water treatment ponds. Adjacent to DRGBrW Railroad spur where it closely approaches the Yampa River approximately 1,000 feet northeast of the confluence of the Yampa and Williams Fork Rivers. Adjacent to the double track portion of the DRG&W Railroad spur where it closely parallels the Yampa River, approximately 3,400 feet northeast of the confluence of the Yampa and Williams Fork Rivers.