2020-03-20_REPORT - M1977342 (3)

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= Climax Molybdenum COLORADO OPERATIONS 68 Henderson Mine&Mill P.O A Freeport-McMoRan Company Empire,CO 80438 Phone(303)569-3221 Fax(303)569-2830 October 31, 2019 Mr. Peter Hays Environmental Protection Specialist 1313 Sherman Street, Room 215 Denver, CO 80203 Re: Climax Molybdenum Company, Henderson Mill, Permit No. M-1977-342 Proposed Technical Revision No.31, Additional 3 Dam Seepwater Return Line Clean-out Ports Dear Mr. Hays, The 3-Dam Seepwater Return Pipelines, which consist of two 10-inch HDPE lines routing seep water from the toe of 3-Dam to the main seep water collection system at the toe of 1-Dam and Ute Park Pump station, were installed in 2000 and included a total of ten installed cleanout access locations, five on each pipe. It was determined that six additional cleanout access locations, three per pipe, were required to allow for greater access of future cleaning and maintenance. In September of 2019 the Henderson Mill successfully installed the additional cleanout access locations. The purpose of this letter is to state that the new cleanout access locations were constructed in conformance with the design plans and specifications. Each new HDPE cleanout was installed with a molded tee with a riser pipe to the surface and all joints connected with HDPE electrofusion couplings. Once all cleanouts were installed, a 24- hour pressure test was conducted along with visual inspections of each new joint. The pressure test was finished on September 19, 2019. Before acceptance of the test, each new fused joint was visually inspected for leaks with no leaks being found in any of the new joints. The pressure gauge at the discharge of each pipeline was verified to continually hold pressure throughout the 24-hour test. After the inspection and pressure test, the pipelines were deemed acceptable for continued use, and put back into service. Sincerely, Dillon Benbow, P.E. Chief Mill Engineer Climax Molybdenum Company Henderson Operations