2011-08-08_REVISION - M1977493 (33)

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• • Technical Revision (TR -18) Climax Molybdenum Company Environmental Protection Plan Permit No. M- 1977 -493 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 (H 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 inside the Nokes building. In the new mill, Nokes is planned to be stored in the Reagent Area of the Mill Building. Phosphorous pentasulfide is a reactive and ignitable greenish - yellow solid with a "rotten egg" smell which can affect the human body through inhalation, ingestion, and dermal contact. While solid phosphorous pentasulfide can cause dermal irritation, the primary health hazard associated with this material is the release of hydrogen sulfide gas upon contact with water. Hydrogen sulfide can be a primary health hazard which acts as an irritant to mucus membranes and can produce severe breathing difficulties. High concentrations can stop breathing immediately. Phosphorous pentasulfide, if released to the environment where it contacts water, will react by producing hydrogen sulfide gas and phosphoric acid. Both of these by- products can be injurious to aquatic and terrestrial biota. Phosphorous pentasulfide can be neutralized with an alkaline substance such as lime, NaOH, or soda ash. Anticipated usage rates are 0.30 to 0.40 lb of Nokes solution per ton of ore processed. EPP: Revision R1 T -9 July 2011