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ZClimax Molybdenum <br />A Freeport-McMoRan Company <br />December 29, 2015 <br />Via Email and USPS Tracking #: 9590 9403 0226 5146 2755 06 <br />Mr. Peter Hays <br />division of Reclamation, Mining and Safety <br />1313 Sherman St., Rm. 215 <br />Denver, CO 80203 <br />COLORADO OPERATIONS <br />Henderson Mine <br />1746 County Road 202 <br />Empire, CO 80438 <br />Phone (303) 569-3221 <br />REGEI E§ <br />JAN 042016 <br />Re: Mine Groundwater NPL Exceedance Notification, Permit No. M-1977-342 <br />Dear Mr. Hays: <br />Henderson Mine is providing this written notification of an NPL exceedance for pH at groundwater point of <br />compliance (POC) well MNGW-1, downgradient of the Henderson Mine, in accordance with Section 5.3 of <br />the Henderson Groundwater Management Plan. This written notification is subsequent to the verbal <br />notifications that were made to you on December 22, 2015. <br />MNGW-1 was sampled during the normally scheduled triannual monitoring event on December 8th, 2015, <br />with a pH value of 6.1 standard units (s.u.). This exceeded the numeric protection limit (NPL) of 6.5-8.5. A <br />follow-up pH measurement was taken on December 17, 2015, resulting in a pH of 6.3 s.u. <br />Henderson performed a trend analysis and the results did not appear to be anomalous, or obvious <br />outliers. Henderson is currently working on further evaluation of the pH trends and the underlying water <br />chemistry. <br />Henderson will provide a follow-up report to the DRMS, where results of additional sampling at MNGW-1 <br />will be provided, including a water quality assessment. One of the objectives of the water quality <br />assessment will be to provide further understanding of potential causes of reduced pH which can then be <br />utilized to guide in further monitoring and/or develop a mitigation plan, as appropriate. <br />If you have any additional questions or concerns, please feel free to contact me at 720-942-3480 or <br />Miguel Hamarat at 720-942-3255. <br />Sincerely, <br />Amber Parmet <br />Environmental Engineer II <br />Climax Molybdenum Company <br />Henderson Operation <br />