2021-08-17_REVISION - M1977342 (4)

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TR-34 to Permit M-1977-342 Environmental Protection Plan Monitoring: The tanks are routinely inspected by Mill personnel to assess effectiveness and integrity of the EPF system. 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 1.3—Tailing Delivery System:The TDL conveys tailing slurry,which is a mixture of tailing material and process water consisting of approximately 40 percent solids,via gravity to the TSF. This line is constructed of 42" HDPE 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. Where grades are in excess of 1.2%, concrete drop structures and reinforced concrete pipe (RCP) have been installed.The original RCP between drop towers in this steeper section has been slip-lined with HDPE pipe.The tailing slurry is delivered to the tailing dam via 24"diameter lead-off pipes used predominantly during winter months, and via a higher quantity of smaller, 8" diameter spigots during the summer months. Where the TDL daylights outside the Mill building there is a diversion box which can route the tailings through an Emergency Cutout (ECO) line.This is a RCP which parallels the upper portion of the TDL, passes underneath County Road 3 and discharges tailings into the southernmost area of the TSF.The ECO is utilized during periods of TDL pipeline and drop structure inspections and during emergency conditions. Emergency Cutout No. 1 is the primary location where tailing slurry is diverted from the TDL when there is an upset condition within the delivery or distribution system. This cutout is also used during regular mill shutdowns as the discharge point for process water that continues to flow through the TDL when the mill is not in operation. Bear Paw pipeline routes process water from the wet scrubbers for dust control and the mill site surface drainage to the TSF. The Bear Paw pipeline discharges in the same approximate location as the No. 1 cutout. An engineered drainage channel runs along the alignment of the ECO and TDL and is a part of this EPF. This channel serves as secondary containment to convey slurry and process solution leaks from the pipeline and valves under the county road to the TSF. 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 TDL. Slurry or process water escaping from the TDL or ECO would drain towards the TSF, where it would be fully contained. Monitoring: The tailing delivery system 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-Tailing Storage Facility:The TSF, dams (1-Dam and 3-Dam), barge pump, and barge return pipeline are located in the Ute Creek drainage basin, north-northwest of the Mill site. The TSF contains tailings, process water and seepage water returned from the seepage collection system. This impoundment and its final configuration of approximately 1,500 acres is described in Section 9 of the Reclamation Permit, as modified. Climax Molybdenum Company August,2021 Henderson Operations Page 21 of 45