2015-02-17_GENERAL DOCUMENTS - M1977342

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Climax Molybdenum A Freeport- McMoRan Company . February 17, 2015 Via Email and USPS Priority Mail: 7006 2150 0001 8832 6207 Mr. Peter Hays Division of Reclamation, Mining and Safety 1313 Sherman St., Rm. 215 Denver, CO 80203 COLORADO OPERATIONS Henderson Mill 19302 County Road 3 Parshall, CO 80468 Phone (303) 569 -3221 Re: Follow -up Notice for Mill Nokes Building Caustic Spills, Permit No. M- 1977 -342 Mr. Hays: Henderson Mill is providing this written follow -up notice to the two successive phone calls made to you on February 11 and February 12th, 2015 pursuant to Rule 8.1 and 8.2 of the DRMS Rules and Regulations. This notice is regarding two unrelated releases of sodium hydroxide solution (NaOH) which escaped from the Nokes building on February 11 "and February 12th, 2015 sequentially. NaOH is a designated chemical in Henderson's Environmental Protection Plan. NaOH is stored in two 11,250 gallon tanks in the Nokes building and is used to neutralize waters in the Mill's lead leach process and to raise the pH of process water in the milling circuit. February 11th - Following transfer operations on February 10, 2015 two valves on water lines leading to the tank were mistakenly left on by the operator. By approximately 2:00 A.M. on February 11, 2015, the tank began overflowing into the building's secondary containment. The overflow was noticed at approximately 3:00 A.M. Due to a 480 volt line that was submerged in the overflow solution, the operators were not able to safely turn off the water causing the overflow until approximately 7:30 A.M. At approximately 8:30 A.M. a leak was noticed from the secondary containment on both the North and West side of the building. The NaOH had mixed with snow and melt water at the point of the leakage, preventing immediate recognition. We believe that approximately 500 gallons of diluted material was released from the secondary containment during this event. The material released from the secondary containment flowed approximately 100 yards across asphalt to a storm drain. The storm drain flows through a pipeline which ultimately discharges into the tailing impoundment. The residual material on the asphalt was neutralized and rinsed down the storm drain. The material in the secondary containment was pumped into the Mill circuit. February 121h — On February 121h a tanker truck carrying a full load of NaOH was instructed to offload into the NaOH tanks in the Nokes building. One of the tanks did not have sufficient capacity to hold the volume of the truck and in turn overflowed into the Nokes building secondary containment. We believe that approximately 10 gallons of material was released from the secondary containment during this event from the West side of the building. The final disposition of this material was the same as the February 11h release. (a) After discovering the issue on February 11th, the Henderson Mill Emergency Response Team was called to respond to the situation. As soon as it was safe to do so, the valves on the water lines causing the tank overflow were turned off and the material in the secondary