2012-10-05_REVISION - M1977342 (12)

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TR -18 to Permit M- 1977 -342 Environmental Protection Plan the tailings storage facility. This line is constructed of 36" concrete pipe on a nominal grade of 1.2% from the mill building to 3 -Dam. At the south abutment of 3 -Dam, the line transitions to 30" HDPE pipe, then to 24" HDPE once it reaches the Number 7 leadoff on 1 -Dam. Where grades are in excess of 1.2 %, concrete drop structures have been installed. The tailings slurry is delivered to the tailings storage facility dam via lead off pipes used predominantly during winter months, and via a larger quantity of smaller diameter spigots during the summer months. Effectiveness: Process water and slurry is contained within the enclosed mill building during processing. Any spills within the mill building will be transported via floor launders, sumps and pumps to either the thickener or the tailings delivery line. Slurry escaping from the tailings delivery line would drain towards the tailings storage facility, where it would be fully contained. Monitoring: The tailing delivery system EPF is routinely inspected by Mill personnel to assess effectiveness and integrity. Maintenance and /or updates to facilities, systems, equipment, or procedures are performed as needed to be protective of the environment and to prevent releases. Mill EPF 1.4 - Tailings Storage Facility: The tailings storage facility, dams (1 and 3 Dam), barge pump, and barge return pipeline are located in Ute Park on Ute Creek, north - northwest of the Mill site. The tailings storage facility contains tailings material, process water, and pumped back seepage water. This impoundment and its final configuration of approximately 1300 acres is described in Section 9 of the Mining and Reclamation Permit as modified by AM -04, TR -02, TR -04 related proposals approved 7/23/98 and 7/18/06, TR -09, TR -11, TR -12, TR -14 and TR- 15 Tailings slurry is deposited at the dam, and the water is recycled. Process water is reclaimed from the tailings storage facility for reuse in the mill through a barge pump system which extracts clarified water from the tailings storage facility surface and delivers it directly to the East Branch Reservoir. Tailings material from the Henderson Mill circuit is potentially acid producing. The beach area on the tailings storage facility can generate fugitive dust during periods of high winds following periods of minimal precipitation in the spring, summer and fall. Consequently, an interim method of suppressing wind -blown tailings dust has been employed at the Henderson Mill site. Coherex is used for controlling fugitive dust from the tailings storage facility. Effectiveness: As discussed in TR -14, the tailings storage facility has been designed, engineered, and constructed to contain the flow from a probable maximum storm event without sacrificing dam stability. TR -14 also addresses operational plans which are now in place to handle post storm event operations. Upon termination of operations, the impoundment will have a storage capacity of 21,000 acre -feet for flood waters including a 10 foot freeboard. Under emergency provisions of the CDPS Permit where the stability of the dam may be threatened, storm waters can be pumped from the tailing storage facility to East Branch Reservoir and bypassed directly the Williams Fork River via the East Branch Emergency Bypass line. This situation has not occurred in Henderson's history. Climax Molybdenum Company Henderson Operations October, 2012 Page 18 of 40