2010-08-02_REVISION - M1977300 (25)

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Environmental Protection Plan, Schwartzwalder Mine 11-1 • 11. SURFACE WATER QUALITY DATA Surface water quality in Ralston Creek has been monitored by the Operator since the water treatment plant began discharging in 1983. Water quality in Ralston Creek is affected by natural runoff and groundwater inflow, upgradient abandoned mines, and by fill material in the valley at the Schwartzwalder mine. Prior to 2002, water quality in Ralston Creek was also influenced by discharge from the Schwartzwalder water treatment plant. This section of the EPP summarizes the water quality standards for Ralston Creek, the locations of historical monitoring stations, the available surface water quality data, and trends in uranium concentrations in the creek. (a) Surface Water Quality Standards (i) Discharge Permit Limits Discharge permit limits have changed over time. The original discharge permit (#CO-000 1 -244) issued by the State of Colorado listed effluent limits for water discharged from the water treatment plant operated at the site. When the water treatment plant was operating during mining (and up to the time of treatment plant shutdown in 2002), those limits included specific metals, uranium (0.776 mg/L), and radium 226/228 (3 pCi/L), as shown in the Table 11-1. The resumption of water treatment in 2010 is subject to revised effluent limits (Table 11-2) which are currently undergoing review and public comment. The most significant modifications to the effluent limits include a reduction in allowable uranium concentrations from 0.776 mg/L to 0.03 mg/l and the addition of monitoring requirements for arsenic, cadmium, chromium VI, iron, mangangese, mercury, nickel, selenium, chloride, and sulfate (Table 11-2). • Alluvial groundwater that was treated during the period from July 2 to July 30, 2010 in the interim (50 gpm) water treatment system described in Section 15(b)(i) was subject to interim effluent limits. Those limits were identical to the limits shown in Table 11-1 except that the daily average and maximum limits for total recoverable uranium were set at 0.03 mg/L (30 µg/L). Table 11-1. Existing Discharge Permit Effluent Limitations • Effluent Parameter Effluent Limitations Maximum Concentrations 30-Da Avera a Dail Maximum Flow, MGD 0.288 Re ort COD, m g/1 100 200 Total Suspended Solids (TSS), mg/1 20 30 Potentially Dissolved Uranium, ug/1 776 1243 Radium 226 +228 (total), Ci/1 3 10 H, s.u. minimum-maximum NA 6.5-9 d/ Oil and Grease, mg/1 NA 10 d/ Total Recoverable Antimony, u g/1 6 Report Boron, m g/1 0.75 Report Total Recoverable Chromium, u g/1 11 16 Potentially Dissolved Copper, u g/1 5.4 7.7 Potentially Dissolved Silver, u g/1 0.027 0.73 Potentially Dissolved Zinc, u 1 71 71 Weak Acid Dissociable Cyanide, u 1 NA 5 Fluoride, mg/1 NA 2 Total Recoverable Thallium, u 1 0.5 NA Whole Effluent Toxicity, Chronic Lethality Cerioda hnia species NA IWC = 100% Fathead Minnow Pime hales romelas NA IWC = 100% 4109C.100731 Whetstone Associates