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WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2003-XXXX • 9 SPX CORPORATION MARLEY COOLING TOWER COMPANY SAN JOAQUIN COUNTY included in this new Order. However, results of monitoring are not sufficient to determine if the Discharger can meet the new monthly average effluent limitations for copper of 3.3 ug/L(ppb) (0.02 pounds per day) @ 44 mg/L(ppm) hardness as CaCO3. Data submitted by the Discharger indicates that, when the facility is properly operated, final effluent concentrations of copper are reported to be less than the detection limit of 5 gg/L(ppb). Historical data are not of sufficient quality to determine compliance with the new monthly average limitation. Detection of copper to 0.5 ug/L(ppb) is feasible in accordance with the SIP. This Order includes a Provision which requires.the Discharger to collect data sufficient to determine compliance with this new monthly average effluent limitation for copper. As provided in Section 2.1 of the SIP, a time schedule is included in this Order to allow the Discharger to achieve compliance with the new monthly average effluent limitations for copper. In accordance with the SIP, Sections 2.2, a numeric monthly average interim limitation for copper is established in this Order based upon current treatment facility performance. Since the treatment facilities can, when properly operated, produce an effluent with copper concentrations less than 5 ug/L (ppb), this Order includes a performance based interim average monthly effluent limitation for copper set at this historical limit of detection of 5 µg/L (ppb). If a compliance schedule justification is submitted by 31 May 2003, this interim limitation shall be an enforceable limitation until the final monthly average effluent limitation becomes effective on 1 February 2008. 21. Previous Order No. 93-221 included daily maximum and monthly average effluent limitations for hexavalent chromium based upon water quality objectives established by the California Inland Surface Waters Plan. Order No. 93-221 included a daily maximum limitation for hexavalent chromium of 11 pg L (ppb), and a monthly average limitation for hexavalent chromium of 11 gg/L (ppb). New limits for hexavalent chromium have been established in this new Order based upon the reasonable potential to exceed the chronic freshwater aquatic life criterion in the.CTR (new information). Results of final effluent monitoring indicate maximum effluent concentrations (MECs)of hexavalent chromium have been high as 17 µg/l,(ppb) (9/15/00). Without regard to dilution, this MEC exceeds the acute aquatic life Criterion Maximum Concentration(CMC) and the chronic aquatic life Continuous Criterion Concentration (CCC) for hexavalent chromium (16 ug/L(ppb) and 11 µg/L (ppb) respectively). New water quality based effluent limitations have been calculated based upon methodologies in the SIP. The specific calculations are further described in the attached Information Sheet. Considering that the Stockton Diverting Canal may at times have little or no flow and provide little or no assimilative capacity for hexavalent chromium, final water quality based effluent limitations have been developed using the steady state model in the SIP, with no credit provided for dilution. The acute and chronic effluent concentration allowances (ECAs) were set equal to the aquatic life criterion for hexavalent chromium, and the most limiting long-term average (LTA) discharge condition was determined using Table 1 of the SIP, using a default coefficient of variation of 0.6. The average monthly effluent limitation (AMEL) and maximum daily effluent limitation (MDEL) were then calculated using multipliers in Table 2 of the SIP.