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TR -18 to Permit M- 1977 -342 <br />Environmental Protection Plan <br />Tailings storage has been designed, and is being operated, with effective engineering controls <br />and redundancies, including seep water collection and return, a groundwater interceptor <br />system, and regular internal and external monitoring and inspections. <br />Monitoring: Routine monitoring associated with the tailings storage facility includes the <br />following: <br />• Routine inspections are performed on a daily basis by Henderson Tailings personnel <br />and include visual observations of the Mill site, Tailings Dam Storage facility Shop, <br />#1 Dam, #3 Dam, the East Branch Dam, East Branch Reservoir, East Branch Pump <br />House, #1 Dam Seep Water Collection Area, Interceptor Canals, Interceptor Roads <br />and the Ute Park pump station. <br />• Monthly piezometer monitoring and data assessment. <br />• Completion of a detailed monthly inspection of the tailings storage facility and the <br />Seep Water Collection and Return System. <br />Maintenance and /or updates to facilities, systems, equipment, or procedures are performed as <br />needed to be protective of the environment and to prevent releases. Additional Coherex <br />treatments may also be applied on an as needed basis. <br />Mill -EPF 1.5 — Seep Water Collection and Return System: Contact water seeping from the <br />base of the tailings storage facility dams may be acidic and is not discharged to the <br />environment without treatment. Therefore, a system to collect this seepage and return it to the <br />process water and tailings circuit was designed and installed during construction in the 1970s <br />and has been modified through TR -04 related changes, TR -09„ TR -10, and TR -14. The <br />system collects and contains dam seepage and it lowers the phreatic surface in the tailings <br />storage facility and dams. The system is comprised of trenched and piped collection and <br />conveyance structures including foundation drains, horizontal drains, pipelines and ditches that <br />extract and direct seep water to the Ute Park pump station. <br />Effectiveness: This EPF is one of several engineering controls and redundancies to prevent <br />releases of acidic waters and has been effectively operated (as amended and improved) since <br />the beginning of Mill operations in 1976. <br />Monitoring: Routine monitoring associated with the Seep Water Collection and Return <br />System includes the following: <br />• Routine inspections are performed on a daily basis by Henderson Tailings personnel <br />and include visual observations of the Mill site, Tailings Dam Storage facility Shop, <br />#1 Dam, #3 Dam, the East Branch Dam, #1 Dam Seep Water Collection Area, <br />Interceptor Canals, Interceptor Roads and the Ute Park pump station. <br />• Completion of a detailed monthly inspection of the tailings storage facility and the <br />Seep Water Collection and Return System. <br />• Annual leakdown piping integrity test is performed on piping used to convey seep <br />water from #3 Dam to the Ute Park pump station. <br />Maintenance and /or updates to facilities, systems, equipment, or procedures are performed as <br />needed to be protective of the environment and to prevent releases. <br />Climax Molybdenum Company <br />Henderson Operations <br />October, 2012 <br />Page 19 of 40 <br />