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 T -4 Acid - Forming Materials and Acid Mine Drainage The Climax ore body beneath Bartlett Mountain contains unoxidized sulfides that, in the presence of oxygen, water, and bacteria, have the potential to become an acid - forming material as defined in Rule 1, Section 1.1(1). Likewise, waste rock materials deposited in McNulty OSF, North 40 OSF, and tailing material deposited in the TSFs also contain material with acid - forming potential. Climax concurred with this fact in its response to the DRMS (August 31, 1994) when it accepted the DRMS determination that Climax was a DMO under the amended rules. In addition, water that percolates through the open pit area and accumulates in the pit or closed underground workings contacts sulfide bearing material and, in tum, has the potential to become acidified, thus, meeting the definition of "Acid Mine Drainage" in Rule 1, Section 1.1(2). Overburden material will be handled during operations, to the extent practicable, to minimize the generation and impact of acid drainage as well as the volume of water requiring treatment during and after mining. As overburden material is placed as part of ongoing operations, Climax will continually look for and identify opportunities to manage overburden materials to minimize acid rock drainage and the volume of water requiring treatment. Techniques will include, but may not be limited to, material segregation (based on acid generating potential), upgradient diversion of unimpacted water, and Climax's election to implement concurrent reclamation to minimize future acid drainage and the quantity of water requiring treatment. Concurrent reclamation of OSFs is described in Exhibit E. As required under Rule 6.4.21(6), appropriate EPFs have been identified to minimize, capture and treat acid mine drainage (see Section T -5.3), The locations of OSFs have been developed with consideration of existing conditions as well as overall technical and economic feasibility. As described in Exhibit D of Permit Amendment Application AM -06, overburden placement will consist of additional placement in the area of existing E and F dumps as well as the existing McNulty OSF. The scheduling /sequencing of overburden placement is being performed during the summer of 2011 as part of ongoing mine plan evaluations. This investigation and design work is focused on geotechnical stability, but will also include the development of a stockpile operations and monitoring plan. The operations and monitoring plan is anticipated to include recommendations and guidelines for overburden placement, which will be used in the development of EPFs for the OSFs. Seepage collection and run -on and run -off control facilities are identified as EPFs (see Section T- 5.3.2) at these locations to minimize the impact of potential acid drainage associated with these facilities. Designs for these EPFs will be submitted prior to the initiation of construction in accordance with Rule 7.3. The acid - forming materials will remain in -situ at the Climax site following final termination of mining and processing activities. As discussed herein, as long as acidic drainage with the potential to affect the environment is released from these sources, such drainage will be managed according to the stipulations and requirements of the appropriate regulatory permits in place at the time. The geochemical processes at the site are well understood to ensure the effectiveness of the water management and treatment system. Table T -E -6, included in Appendix T -E (Geochemical Data) presents a summary of water quality data from impacted sources, including seepage from the OSFs, TSFs and other sources from around the site that are collected and treated. Samples of impacted water sources will continue to be collected by Climax on an as needed basis. T Temporary Cessation /Prolonged Lack of Mineral Production Surface water discharge at Climax is regulated under the CDPS Permit as discussed in Section T -2.2. Under temporary cessation or a prolonged lack of mineral production scenario, mine waters, storm water, and seepage waters would continue to be managed, treated and discharged according to the conditions of this permit. T Final Closure Upon final closure and reclamation of the Climax Mine as described in the Permit, Technical Revisions, and Amendments, impacted waters from the mine, ponded water on the TSFs, seepwater from TSFs and OSFs, and storm water will be managed according to conditions of the CDPS Permit. This permit EPP: Version R2 T -14 December 2011