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INFORMATION SHEET7• WASTE DISCHARGE REQUIRMENTS ORDER NO.R5-2002-XXXX MARLEY COOLING TOWER COMPANY STOCKTON, SAN JOAQUIN COUNTY These constituents and/or parameters include; copper,hexavalent chromium, total chromium, arsenic, total dissolved solids (TDS), chlorine residual, and toxicity. Effluent limitations have been established or retained for these constituents as discussed in the following Findings of this Order Copper Previous Order No. 93-221 included daily maximum and monthly average effluent limitations for copper based upon water quality objectives established by the California Inland Surface Waters Plan. Order No. 93-221 included a daily maximum limitation for copper of 6.5 µg/L (ppb), and a monthly average limitation for copper of 6.5 µg/l, (ppb), which were adjusted based upon the observed receiving water hardness. New limits for copper have been established in this new Order based upon the reasonable potential to exceed freshwater aquatic life criteria in the CTR(new information). These new water quality based effluent limitations have been calculated based upon methodologies in the SIP. Results of final effluent monitoring indicate maximum effluent concentrations (MEC's) of total copper concentrations as high as 23 µg/L(ppb) (8/15/01) and 80 µg/L(ppb) (10/19/01). Without regard to dilution, these MEC's exceed the acute aquatic life Criterion Maximum Concentration (CMC) and the chronic aquatic life Continuous Criterion Concentration(CCC) for copper (total), adjusted using the minimum observed receiving water hardness (6.5 µg/L(ppb) and 4.6 µg/L (ppb) respectively @ 44 mg/L (ppm) hardness as CaCO3(12/20/01)). Since the Stockton Diverting Canal provides, at times, little or no dilution, there is a reasonable potential for the discharge to cause or contribute to an excursion above water quality standards. Section 1.3 of the SIP requires a water quality based effluent limitation when the MEC exceeds appropriate pollutant criterion. When required, Section 1.4 of the SIP provides four methods that may be used to develop effluent limitations. These four methods include: (1) assigning a loading allocation based upon a completed TMDL; (2)use of a steady state model; (3) use of a dynamic model; or, (4) establishing effluent limitations that consider intake water pollutants. Considering that the Stockton Diverting Canal may at times provide little or no assimilative capacity for copper, final water quality based effluent limitations have been developed using the steady state model, with no credit provided for dilution. Since a site-specific translator has not been developed for copper as described in the SIP Section 1.4.1,the USEPA conversion factor was used in expressing the dissolved copper criterion as total recoverable. Acute and chronic effluent concentration allowance's (ECA's) were set equal to the adjusted acute and chronic copper criterion, and the most limiting long-term average (LTA) discharge condition for copper was determined using Table 1 of the SIP, using a 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 as shown below: