2010-04-20_REVISION - M1977300 (8)

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Environmental Protection Plan, Schwartzwalder Mine 11-2 U.S. EPA Effluent Limitations for Mine Drainage from Open-Pit and Underground Uranium Mines X40 CFR 440.34 Maximum for any one day 30 day average Ra-226. (dissolved) .........................................._10 pCi/l (0_.37 Bq?l)............... ........... .._3 pCi/l..(0.1._ _1..._Bq/1)..... .......... , Ra ..... -226 (total) 30 P ..Ci/1 _1._ 1._1 ..._Bq/1) ........................._..._......... (0..3.7...B.q/1) . i T ................................................................................................. ................ ...................... ,. 4 mg/1 2 mg/l The discharge permit applied to the single discharge point (Outfall 001), the pipe at which water from the treated water retention pond was released to Ralston Creek. In the 29 reporting periods leading up to the discharge permit renewal in 2005, CDPHE identified only four limit excursions: pH (1 event), thallium (1 event), silver (1 event), and ceriodaphnia WET test results (1 event). The Discharge Monitoring Reports have reported no discharge since the water treatment plant was shut down in June 2002. (ii) Stream Standards The Colorado Department of Public Health and Environment (CDPI--IE) Water Quality Control Commission (WQCC) has published in-stream water quality standards for this reach of Ralston Creek. Located in the Clear Creek Basin, Reach l7b includes the "mainstem of Ralston Creek from the source to the outlet of Arvada Reservoir, including Ralston Reservoir and Upper Long Lake" (5CCR 1002-38). Regulation Number 38 (5CCR 1002-38) lists the specific numeric standards for Stream Segment 17b, while Regulation Number 31 (5CCR 1002-31) gives the basic stream standards and methodologies applicable to all state waters. The applicable water quality standards for cold water biota in Ralston Creek Stream Segment 17b are listed • in Table 11-3. Acute and chronic standards for metals are based on dissolved concentrations, except where noted otherwise in Table 11-3. The numeric criteria for cadmium, chromium III, copper, lead, manganese, nickel, silver, uranium, and zinc are hardness dependent, and are calculated according to the following equations: C(acute) = WER • e mn ln(H}+bn . Ka C(chronic) - WER• emc•1n(H)+bc . KC where WER= Water effect ratio MA = Metal-specific constant for acute toxicity (e.g, MA for uranium is 1.1021) mc = Metal-specific constant for chronic toxicity (e.g, mc for uranium is 1.1021) H = Hardness (mg/L as CaC03) bA = Metal-specific constant for acute toxicity (e.g, bA for uranium is 2.7088) be = Metal-specific constant for chronic toxicity (e.g, bc for uranium is 2.2382) K = Freshwater conversion factor The numeric criteria shown in Table 11-3 have been calculated based on a hardness of 163, which is the low-flow average at station SW-BPL since sump shut-off in June 2002. The calculation assumes a water effect ratio (WER) of 1.0 unless otherwise noted. The uranium standard of 40 pCi/L (0.059 mg/L) applies at a water supply intake. Elsewhere, the hardness- based aquatic toxicity standards apply. Using a hardness of 163 mg/L, the acute toxicity standard for uranium is 4.12 mg/L and the chronic toxicity standard is 2.57 mg/L. The hardness value used in calculating numeric criteria is the average of the calculated hardness values for • station SW-BPL during low flow months from June 2002 to February 2007. The use of average of hardness values during low-flow season is in accordance with the CDPHE WQCCs "Basic Standards and 71 69C. 100419 Whetstone Associates •