2011-12-15_REVISION - M1977493 (2)

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Technical Revision (TR -18) Climax Molybdenum Company Environmental Protection Plan Permit No. M- 1977 -493 ventilated areas that are not near heat, sparks, or open flames. Anticipated usage rates are 0.025 to 0.045 lb of iron depressant per ton of ore processed. The iron depressant will be stored in one tank with a capacity of 10,000 gallons. The iron depressant will be stored in the reagent storage area of the mill building (see Mill Building Detail - Area 450 on the south side of the mill building on Figures AM- 06 -T -06 and AM- 06- T -07). Secondary containment with a volume greater than that of the tank will be provided in the reagent storage area (see Reagent Storage Area Detail Figure AM- 06- T -07). Tank level indication will be available locally as well as through the control system. The control system will alarm for a given tank low and high level. A local alarm hom will sound for a given tank high level. In the event of a storage tank failure, the iron depressant will be contained in the reagent storage area via secondary containment. The secondary containment area is equipped with a sump but no sump pump. In the event of a release in this area, a pump will be placed in the secondary containment sump and the depressant will be routed back into the process circuit or pumped into a suitable container for proper disposal through direction from the environmental department. A spill that occurs during offloading into the storage tank will be handled similarly using a sump located in the offloading area. In the event of an iron depressant distribution system failure, the iron depressant will be contained within the mill building and will be sent to tailings or the rougher concentrate thickener depending on where the failure occurs. T - 3.2.5 Iron and Copper Depressant Additional depressant products may be utilized at the site in the mill circuit. Sodium cyanide remains a potentially important reagent that may be utilized in low doses in liquid form in the flotation mill circuit to depress pyrite, chalcopyrite, iron, and copper. Although sodium cyanide (cyanide) is not currently utilized at the site, it has been used in the past and may be used in the future. If used, it would be delivered and stored in solid briquettes then mixed with water and caustic soda beads (NaOH) to maintain pH 11 for safety. At acidic pHs, highly toxic hydrogen cyanide (HCN) gas develops. Cyanide is a white solid with a faint almond odor that can affect the human body through inhalation, ingestion, and dermal contact. Cyanide can rapidly cut the flow of oxygen from the blood stream to body tissues. At lower levels of exposure, early symptoms include weakness, headache, confusion, nausea, and vomiting. These symptoms may be followed by unconsciousness and death. Cyanide is rapidly removed from the body by the liver and is neither bioaccumulative nor carcinogenic. Strong solutions of cyanide salts are corrosive and may produce ulcers. Cyanide is a naturally occurring compound that breaks down rapidly in the environment by exposure to oxygen, ultraviolet (UV) radiation (sunlight), and naturally occurring bacteria. In surface waters, however, cyanide can be detrimental because it is more toxic to aquatic life than to humans. Higher concentrations in surface water ponds also can be toxic to terrestrial wildlife and migratory birds. Sodium Cyanide is currently not planned to be used in the Climax reagent scheme. It has been maintained as a possible depressant if other reagents do not perform adequately. If inclusion of sodium cyanide in the milling process enters further planning stages, Climax will notify the Division with additional information regarding the expected concentration, process solution volumes, storage location, fate of designated chemicals, measures taken to prevent and monitor for a release, and measures taken in the event of a release. T - 3.2.6 Lead and Copper Depressant Pre -mixed Nokes Reagent will be incorporated into the mill circuit as a lead and copper depressant. Phosphorous pentasulfide is a principal ingredient in pre -mixed Nokes Reagent. Nokes Reagent is a mixture of caustic soda beads (NaOH) and phosphorous pentasulfide in solution with water. The addition of NaOH to the solution maintains a pH greater than 11 which prevents the release of hydrogen sulfide gas (H2S). Climax uses only pre -mixed Nokes Reagent, which is liquid Nokes pre -mixed with NaOH prior to delivery. During past operations, Climax mixed Nokes Reagent at the mill site in a Nokes mixing tank EPP: Version R2 T -11 December 2011