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III IIIIIIIIIiIII III ~ ,~ . • STATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY Depanmenl of Natural Recourses 1713 Sherman SI., Room 215 Denver, ColoraEio 80207 Phone: 13071 866-3567 FA%:13031 8128106 August 27, 1996 ~I~~~ DEPARTMENT OF NATURAL RESOURCES Roy Romer Guvernor Mr. J.J. Jones lame~sE«nnead E~ecmive Director Climax Molybdenum Company Mic hael ff Enng P.O. Box 68 D~~~,~~~D~re~ior Empire, CO 80438 RE: Ground Water Monitoring Program, Henderson Mine and Mill, Technical Revision TR-005, Permit No. M-77-342 Dear Mr. Jones: Thank you for your letter detailing Climax Molybdenum Company's (CMC) responses to the Division's remaining concerns related to the ground water monitoring plan for the Henderson Mine and Mill. It is apparent that there are several issues upon which the Division and CMC will have to reach agreement before the ground water monitoring technical revision can be approved. The Division's position on these issues, including rational and suggested resolution, are detailed in this letter. 1. Parameter List for Ground Water Monitoring CMC has stated that the list of parameters to be monitored proposed by the Division is unreasonable. CMC specifically cites molybdenum, gold, sodium, and uranium as unreasonable parameters because none has a ground water narrative standard nor a surface water standard in Segment 4. Inclusion of gold on the Division's proposed parameter list was an error; the Division intended to list silver as a monitoring parameter. Uranium was included on the Division's parameter list because of its potential to be present in ground water affected by the Henderson mining and milling operations (see explanation below) and because there is an aquatic life standard and a proposed drinking water standard for uranium. Please be advised that the Division is not limited in the selection of parameters to be monitored by the constituents that are assigned standards for specific stream segments. Sodium was included on the Division's parameter list because of its potential to be present (sodium hydroxide is used for water treatment at the mine, and sodium may be dissolved from rock in certain natural and man created environments that may be present at the Henderson Mine and Mill) and because sodium may be damaging to soils, and is potentially damaging to drinking water supplies. Molybdenum also may be present in potentially affected ground water, and can cause molybdenosis in livestock and wildlife. The Division would probably not assign numeric protection levels to sodium and molybdenum, but would require reporting of the concentration of these elements to determine