2011-08-08_REVISION - M1977493 (36)

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Water Quality Monitoring Plan Climax Molybdenum Company Version: R1 Permit No. M- 1977 -493 • 3.3.2 Location and Description of Classified Stream Segments Blue River basin, Segment 13, contains the mainstem of Tenmile Creek from the Climax Parshall Flume (Outfall 001) to the point immediately above the confluence of West Tenmile Creek. Also included are all tributaries and wetlands from the source of Tenmile Creek to the point immediately above the confluence with West Tenmile Creek. Exceptions include: Segment 15, the mainstem of Clinton Creek from the source to the confluence with Tenmile Creek. • Segment 13 of the Blue River basin is classified as Aquatic Life Cold 1, Recreation P, and Agriculture. 3.3.3 Potential Contamination Sources As described more fully in the EPP, potential sources of contamination in the Tenmile Creek Watershed include: • Designated chemicals (stored and used) for production of concentrates; • Mill water reclaim circuit (including storage tanks and supply system); • Process facility /mine yard (aka: camp area) run -off and seepage; ■ Underground mine and open pit water; ■ OSF run -off and seepage (North 40 and McNulty); • Tailing and process water delivery systems (new Tailing Delivery Line (TDL) and East Tailing Delivery Line (ETDL)); • Water treatment chemicals (stored and used) for treatment of mine water (including the Lime Station and SDP); • Robinson TSF; • Tenmile TSF and 3 Dam seepage; and • Mayflower TSF and 5 Dam seepage. 3.3.4 Hydrogeology Groundwater in the Tenmile Creek valley primarily occurs in a veneer of alluvium and glacial till which overlay bedrock consisting of Paleozoic sedimentary and Tertiary quartz monzonite formations. Data from seismic refraction surveys and monitoring well logs (Climax Molybdenum Co., 1984) indicate that the alluvium and glacial till range in thickness from 0 to over 90 feet. The alluvium consists of deposits ranging in size from clays and silts to boulders. Depth to water data collected in monitoring wells GWM -1 and GWM -2 indicate that groundwater occurs between 10 and 30 feet below ground surface with a seasonal flux in elevation. The direction of ground -water flow in the Tenmile Creek valley is controlled by the bedrock topography. Hydraulic conductivity data of the bedrock and the overlaying soils are summarized in Table 1. These data were measured as part of the construction of the Mayflower Tailings Dam. A total of 44 tests in eight holes were conducted using both slug and packer testing methods (Kumar & Assoc., 1994). EPP — Appendix C August, 2011 9