2018-08-22_REVISION - M1977493A - Laserfiche WebLink

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Technical Revision (TR-28) Climax Molybdenum Company Environmental Protection Plan Permit No. M-1977-493 Sulfuric Acid: Sulfuric acid is incorporated into the water treatment system at the PDWTP to lower the pH of discharged water to within the range of pH 6.5 to 9.0. Sulfuric acid is stored in an approximate 4,300 gallon carbon steel tank located within an enclosed room with epoxy-coated concrete floor inside the PDWTP filter building.. Flocculent: Flocculent is received in bags and put into solution onsite at the SDP and PDWTP. At the SDP, the liquid solution is stored in a 2,000 gallon mix tank and a 3,500 gallon feed/storage tank. At the PDWTP, the flocculent is mixed and stored in two approximately 3,000 gallon tanks. The mixing tanks are located within secondary containment inside the SDP and PDWTP buildings. East and West Interceptor Systems: An extensive clean water interceptor system has been established by Climax around the affected areas of the upper Tenmile Creek Watershed. The interceptor canal system conveys storm water around the process facility and TSFs, which limits the amount of impacted waters to be treated and discharged. As agreed upon with DRMS, although these interceptors are considered to be pre-EPF systems and do not contain or control designated chemicals or process solutions, they will be managed as internal EPFs. The interceptor system is closely monitored, inspected and maintained as part of routine site monitoring activities. Other than repair and maintenance/upgrades, any future expansion or modification of the interceptors will be subject to review by DRMS, consistent with Section 6.4.21(10)(a)(ii) of the Rules. The interceptors total approximately 13 miles in length and are labeled as the West Interceptor and the East Interceptor (Figure AM-06-T-01). These interceptors were constructed in the 1970s during construction of the Mayflower TSF to intercept and convey snowmelt and storm water around the three TSFs in the Tenmile Creek Watershed. The West Interceptor begins along the west side of the Tenmile TSF and drains directly into Tenmile Creek within the Climax property line downstream of the Mayflower TSF. The east interceptor begins at the edge of the McNulty OSF and terminates at the Clinton Gulch Reservoir. The Clinton Canal begins at Clinton Reservoir and terminates at Mayflower Creek. The total Interceptor System handles approximately 14,500 acre-feet of water annually. Clinton Reservoir offers flood protection for Mayflower TSF. Pit Dewatering System As described in Section T-5.1.2, the 5-Shaft Pump Station and Storke Pipeline are used to convey impacted storm water that passes through the open pit area and collects in the underground mine workings. The current Climax mine plan will result in deepening the open pit to below the elevation of the 5-Shaft pumps. When this occurs, Climax will need to transition from the current 5-Shaft Pump Station to an in-pit dewatering system to convey impacted storm water to the SDP for treatment. The pit dewatering system will consist of a pumping station located at the bottom of the open pit that will convey water to one or more booster stations up to the rim of the open pit. This water will then be piped through the Camp area to the ETDL or other pipeline that will transmit the mine drainage by gravity flow to the SDP for stage one metals treatment. The pump station and boosters will be powered by an electrical transmission line with emergency generators available in the event of power outages. Preliminary designs of the pit dewatering system were included in the submittal of this Technical Revision 24. Climax will provide final as-built drawings of the system and the EPF certification to DRMS upon completion of the system. Protection of Clinton Reservoir. As the McNulty OSF is expanded, it will become necessary to truncate the upper end of the East Interceptor Canal to direct runoff from the OSF to the water management and treatment system instead of allowing this water to enter the interceptor and Clinton Reservoir as outlined in TR-25. The design of this modification of the East Interceptor was developed to ensure that impacted water will not enter the East Interceptor, and to maximize the amount of clean water intercepted. The tributary area to the East Interceptor is currently estimated at 832 acres. When the East Interceptor is truncated, Climax estimates that the tributary area will be reduced by approximately 240 acres. Although not considered EPFs, Climax will conduct visual inspections and implement other Storm Water Management Plan best management practices (BMPs) in association with its general storm water permit to manage disturbances associated with the open pit, including road construction and pit development activities near the summit of Bartlett Mountain, to prevent water quality impacts to the Clinton Gulch watershed and Clinton Reservoir from erosion and sediment. As part of its storm water management program, Climax also will utilize BMPs for blasting activities to prevent water quality impacts from flyrock EPP: Version R4 T-30 August 2018