2012-10-05_REVISION - M1977342 (12)

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TR -18 to Permit M- 1977 -342 Environmental Protection Plan 5. DESIGNATED CHEMICAL EVALUATION The designated chemicals discussed in this EPP are exclusive to the extractive metallurgical processing of molybdenite ore to produce MoS and are thus only located at the Mill. The Henderson Mine does not use designated chemicals as a part of mining activities. The designated chemicals, listed quantities, and use concentrations are presented as the best information available at the time of the submittal of this EPP. These chemicals, quantities, and concentrations may vary based upon production needs and processes. For example, brand name chemicals such as (but not limited to) Syntex, Cytec OrePrep F -579 or Witconate may be changed out for different brands of similar chemicals based on factors such as effectiveness, cost and availability. Changes in brands and reagent usage are a part of the production process and are not considered to be grounds for notification to the DRMS. However, notification to the DRMS will be made in the event that: • New types of designated chemicals, not discussed herein, are added to the process; • The storage location of a designated chemical is changed; or • The containment facility for a designated chemical must be modified. 5.1. List of Chemicals and Specific Locations Table 1 - Designated Chemicals Used at the Henderson Mill - provides a summary of the estimated quantity, locations and fate of the designated chemicals used in processing at Henderson. Note that the Mine is not included in Table 1 as there are no designated chemicals employed at that location. 5.2. Known Potential to Affect Human Health and the Environment The following is a brief narrative description of the known potential to affect human health and the environment for the designated chemicals at Henderson. Material Safety Data Sheets (MSDSs) for these chemicals can be found in Appendix C. Nokes Reagent — Phosphorous pentasulfide is a principal ingredient in Nokes Reagent. Nokes Reagent is a mixture of sodium hydroxide and phosphorous pentasulfide in solution with water. The addition of sodium hydroxide maintains the solution at pH 11 to prevent the release of hydrogen sulfide gas. The reagent is incorporated into the mill circuit as a lead and copper depressant. It is mixed at the Mill site in a Nokes mixing tank and stored for use inside the mill building. Phosphorous pentasulfide is a reactive, ignitable, greenish- yellow solid with a "rotten egg" smell that 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 (H gas upon contact with water. H can be a primary health hazard that 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, sodium hydroxide, soda ash, etc. Climax Molybdenum Company Henderson Operations October, 2012 Page 9 of 40