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COLORADO OPERATIONS Climax Molybdenum Henderson Mine and Mill A Freeport-McMoRan Company P.O. Box 68 Empire, CO 80438 Phone(303)569-3221 Fax(303)569-2830 August 12, 2021 Submitted Via ePermitting and Email Mr. Peter Hays Division of Reclamation Mining and Safety 1313 Sherman St., Rm. 215 Denver, CO 80203 RE: Climax Molybdenum Company, Henderson Mill, Permit No. M-1977-342, Technical Revision No. 34, Environmental Protection Plan Revision, Response to Adequacy Review Dear Mr. Hays: Climax Molybdenum Company (CMC) is providing this letter in response to DRMS' Adequacy Review letter dated July 7, 2021, in relation to the Henderson Reclamation Permit Environmental Protection Plan (EPP). DRMS comments are included below in italics, followed by Henderson's response. 1. On Page 7 of 40, Section 5—Designated Chemical Evaluation, the Operator states the Henderson Mine does not use designated chemicals as part of the mining activities. The permit boundary for the Henderson Mine was increased to include the URAD WTP and water conveyance pipeline from the Henderson Mine to the URAD WTP in Amendment No. 7(AM-07). The amendment was approved by the Division on May 4, 2020. The URAD WTP is an Environmental Protection Facility (EPF)and uses designated chemicals to removed metals from the mine water. Please update the revised EPP to state designated chemicals are used at the Henderson Mine in the URAD WTP and provide a list, description and storage location for the chemicals. The EPP revisions for designated chemicals at the Henderson Mine include but are not limited to the following sections: • Section 2.3 Site Figures—Figure 1 • Section 5.1—List of Chemicals and Specific Locations • Section 6.1.1—Designated Chemicals Handling • Section 6.1.1.1— Temporary Cessation • Section 6.1.1.2—Final Closure Henderson has revised the EPP to include water treatment chemicals currently in use at the URAD WTP as well as the treatment chemicals that will be used at the new Mill WTP as designated chemicals. Substantive EPP revisions include updates to the following sections and pages: • List of Tables and List of Figures; updated title and description of Figure 1 (Page iii) • Section 2.3 Site Figures—Revised Figure 1 and Figure 3 title and description (Page 3) • Section 5.0 Designated Chemical Evaluation; Updated intro paragraph (Page 7) • Section 5.1 — List of Chemicals and Specific Locations; Updated intro paragraph (Page 7) • Table 5-1: Designated Chemicals Used at the Henderson Mine; Added new table (Page 8) • Table 5-2: Designated Chemicals Used at the Henderson Mill; Revised table (Page 9) • Section 5.2—Known Potential to Affect Human Health and the Environment;Addition of Mine WTP designated chemicals (Page 10); clarification of Quicklime used in the mill