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f -. <br />999 <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />I J 1 {Shaman St., Room 215 <br />Dcnvcr. Colorado 80203 <br />Phunc: (tf) fl N66-3567 <br />FA%~ 110.71 b3?-A I06 <br />April 8, 1996 <br />Mr. Jim Kiger <br />Colowyo Coal Co. L.P. <br />5731 State Hwy 13 <br />Meeker, CO 81641 <br />RE: Colowyo Coal Mine (C-81-019) <br />TR-36; Addition of Auger Mining Area #2 <br />Dear Mr. ICiger, <br />~~~~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />Roy Romer <br />Governor <br />lames S Luchhead <br />E~ecuuve Director <br />Michael 8. Long <br />Division D~reaor <br />The Division of Minerals and Geology received Colowyo's adequacy comments for TR-36. <br />Mr. Jim Pendleton of our office reviewed Colowyo's response, and his letter is attached for <br />reference. <br />The Division believes that the potential subsidence of the fill warrants the installation and <br />occasional monitoring of subsidence monuments by Colowyo. Colowyo should install a half <br />dozen steel fence post monuments above the Auger Area 2 bores on the West Pit Fill <br />outside the low wall of the pit, in addition to the proposed perimeter posts. The top <br />elevation of these posts should be surveyed immediately following installation and <br />resurveyed within one to three months after auger extraction has occurred beneath it. <br />Resurveying would only be required if visual inspections determine that subsidence impacts <br />may be occurring, at the direction of the Division. The posts need to be surveyed one final <br />time when Phase I release is requested. <br />As an alternative to the monitoring noted above, Colowyo could elect to reanalyze it's <br />original design stability analysis of the West Pit Fill to include the potentially destabilizing <br />effects of auger bore caused subsidence. <br />Please revise the permit and maps as necessary to take into account the additional <br />monitoring requested above, or reanalyze the potential subsidence impacts upon the West <br />Pit Fill. <br />