2011-08-08_REVISION - M1977493 (33)

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• Technical Revision (TR -18) Climax Molybdenum Company Environmental Protection Plan Permit No. M- 1977 -493 • Upgradient diversions to prevent storm water runon from coming into contact with OSF material; • Run -off control features to contain and direct impacted storm water to the water management and treatment system; • Underdrains to eliminate contact between shallow groundwater and OSF materials; • Underdrains beneath OSF toe areas to collect and route seepage to the water management and treatment system. PDWTP: The new PDWTP will provide second stage treatment of the impacted waters to comply with discharge permit requirements. The flow capacity of this plant will limit the total discharge capacity of the process water system. As stated previously, when final design of the PDWTP becomes available, appropriate submittals will be made to DRMS. At that time, additional information regarding chemicals for water treatment contained within the PDWTP and their associated EPFs will also be provided. Containment for Water Treatment Chemicals: As discussed, various source waters are treated by lime neutralization to raise the pH and precipitate metal hydroxides. Precipitates (treatment sludges) are primarily contained within the sludge cell on the Tenmile TSF. Additional precipitation and settling occurs in the Tenmile and Mayflower TSFs. Prior to discharge to Tenmile Creek, sulfuric acid is employed to reduce the final pH into the range stipulated by the CDPS Permit. Lime: Slaked lime is currently produced at the Lime Station. The lime station includes conventional silos for storage of lime and lime slakers. Slaked lime is produced by mixing lime from the silos with fresh water from Buffehrs Lake and /or the McNulty Well. Slaked lime is then piped to the SDP and also to the 3 Dam Pump Station located between Tenmile TSF and Mayflower TSF. Sulfuric Acid: Sulfuric acid is incorporated into the water treatment system to lower the pH of discharged water to within the range of pH 6.5 to 9.0. Sulfuric acid is stored in a 7,000 gallon carbon steel tank at the Mayflower Pump Station. The tank is located within an epoxy lined concrete sump designed to contain 120 percent of tank capacity. GreatFloc 5500: GreatFloc 5500 is received in bags and put into solution onsite. The liquid solution is stored in a 2,000 gallon mix tank and a 3,500 gallon feed /storage tank. These tanks are located within secondary containment inside the SDP 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, 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. 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. The design EPP: Revision R1 T -26 July 2011