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Technical Revision (TR-28) Climax Molybdenum Company Environmental Protection Plan Permit No. M-1977-493 Tenmile TSF and 3 Dam: The Tenmile TSF, 3 Dam, and ancillary facilities such as Tenmile Decant and Tenmile Tunnel are monitored by Climax personnel in accordance with TR-20. Piezometers are utilized to monitor water levels in the dam. Piezometric water levels are recorded and reviewed by Climax and a third-party engineering consultant. Periodic inspections of the TSF include monitoring seepage to detect unusual flow quantity or clarity changes, monitoring spigot discharge and tailing deposition patterns, periodic evaluation of tailing characteristics, observations of pond level and tailing beach width, inspection for signs of erosion, displacement or cracking, and general observations of the dam and appurtenances. Operational plans for the Tenmile (3 Dam) TSF dam are in TR-20. A third-party engineering consultant will evaluate and provide an annual summary report on TSF operation and monitoring results. Mayflower TSF and 5 Dam: The Mayflower TSF, 5 Dam, and ancillary facilities are monitored by Climax personnel in accordance with TR-23. Piezometers are utilized to monitor water levels in the dam Piezometric water levels are recorded and reviewed by Climax and a third-party engineering consultant. Periodic inspections of the TSF include monitoring seepage to detect unusual flow quantity or clarity changes, monitoring spigot discharge and tailing deposition patterns, periodic evaluation of tailing characteristics, observations of pond level and tailing beach width, inspection for signs of erosion, displacement or cracking, and general observations of the dam and appurtenances. Operational plans for the Mayflower(5 Dam) TSF dam are in TR-23. A third-party engineering consultant will evaluate and provide an annual summary report on TSF operation and monitoring results. The 5 Dam seepwater collection and return system at the Mayflower pump station also is monitored. The pump station contains both stand-by pumps and a stand-by generator set should mechanical or power failures occur. Telemetry to the mill is used to monitor the Mayflower Pump Station remotely. SDP and PDWTP: The SDP has been successfully operated since 2007. The PDWTP began operation in 2014. Both plants have been designed with the level of control and redundancy needed to achieve compliance with the Climax mine CDPS permit requirements and environmental protection of Tenmile Creek. This includes extensive automatic control of systems based on installed instrumentation, while providing operators with alarms and the ability to run systems manually, if required. The PDWTP is fully integrated into the current site-wide SCADA and human-machine interface (HMI) monitoring and control systems via fiber optics. The control strategy is designed for automatic and controlled shutdown in the event of system failures or power outages, and will provide for automatic collection and recycle of off specification water. T-6 Groundwater Groundwater at hardrock mine sites in Colorado is regulated through the DRMS. Climax monitors groundwater in each of the three drainage basins surrounding the site (East Fork Arkansas River, East Fork Eagle River and Tenmile Creek). The groundwater program at the Climax Mine is described in the WQMP (Appendix T-C). Per Rule 3.1.7(2)(a), the Water Quality Monitoring Plan (Appendix T-C) presents a discussion of the hydrogeologic conditions specific to each of the three drainages at the Climax mine site. T-7 Surface Water In addition to the water information provided in Exhibit G of AM-06, information relative to surface water containment and control facilities, surface water quality, the Climax treatment and discharge permit, and surface water monitoring and sampling programs have been discussed in Section T-5.0 and in Appendix T-C. Maps showing water related features are found in the Figures AM-06-T-01 and AM-06-T-02. As discussed previously, Climax lies within the headwater areas of three watersheds — the East Fork of the Arkansas River, the East Fork of the Eagle River, and Tenmile Creek, with most of the mine's water treatment/management activity occurring within the Tenmile Creek drainage area. Discharge to Tenmile Creek occurs in accordance with CDPS Permit No. CO0000248. Water Quality Standards for each of these stream segments are in CDPHE-Water Quality Control Division regulations approved by the Water Quality Control Commission (WQCC Regulations 32 and 33). Before Climax implemented its current water treatment/management system, there was a near complete absence of stream life in Tenmile Creek EPP: Version R4 T-35 August 2018