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<br />._. <br /> <br />~~I ~~~II~~~~~~~~ ~~~ <br />999 <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Depanmenl of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (3031 866-3567 <br />FA%:13031 83 2-8106 <br />April 21, 1997 <br />Mr. John Hardaway <br />Cripple Creek & Victor Gold <br />2755 State Highway 67 <br />P.O. Box 191 <br />Victor, CO 80860 <br />RE: Cresson Mine (Permit M-8 <br />from the mine and attendant <br />Dear Mr. Hardaway: <br />lames S. Lochhead <br />Mining Company Eaeculive Director <br />M¢hael B. Long <br />Division Director <br />0-244) Potential for acid rock drainage <br />groundwater impacts. <br />Division staff met with you on April 4, 1997 regarding a number of <br />compliance concerns at the Cresson Mine. Among those discussed was <br />the matter of the potential impacts of acid rock drainage (ARD) <br />from the Ironclad and Squaw Gulch overburden dumps. As a result of <br />a commitment made to you during that meeting, Division staff has <br />re-examined the 1993 and 1994 HCI reports supplied by CC&V in order <br />to provide you with the specific concerns had regarding the data <br />considered and conclusions reached by those studies. The Division's <br />efforts, however, were not limited to reviewing the HCI reports but <br />also included study of other aspects of the hydrologic situation at <br />Cresson, the potential impacts of acid rock drainage on ground <br />water other than the Carlton Tunnel discharge as well as the <br />regulatory "fall out" of these potential impacts. <br />In regard to the HCI reports, it is the Division's position that <br />these reports do not adequately consider the actual conditions at <br />the mine and, therefore, do not incorporate the most appropriate <br />input data for their modeling. In summary, the acid production <br />potential of the mine has been underestimated as indicated below: <br />1) The HCI modeling is based on humidity cell test results <br />rather than on long term batch tests which means that the <br />amount of acid assumed to be generated is too low. Humidity <br />cell tests characterize water from a single pass through <br />"weathered" rock rather than the water that results as it <br />passes thru several volumes of rock. <br />2) The volume of sulfide rich rock considered as having <br />potential to generate ARD is underestimated because the model <br />was based on infiltration thru the surface footprint of the <br />Cresson Pit alone. The calculations did not consider <br />infiltration through the Ironclad Pit, Globe Hill Pit and <br />I~~~~ <br />DEPARTMENT OF <br />NATURAI <br />RESOURCE` <br />Roy Romer <br />Governor <br />