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INFORMATION SHEET • • 12 WASTE DISCHARGE REQUIRMENTS ORDER NO. R5-2003-XXXX SPX CORPORATION MARLEY COOLING TOWER COMPANY STOCKTON, SAN JOAQUIN COUNTY "Where States have not developed chemical specific numeric criteria, States may interpret their narrative standards for specific chemicals by using EPA criteria updated with current quantitative risk values." The TSD further states on page 1 "The integrated approach must include the control of toxics through implementation of the "no toxics" criterion and/or numeric criteria for the parameter of toxicity, the control of individual pollutants for which specific chemical water quality criteria exist in a state's standard, as well as the use of biological criteria. Reliance solely on the chemical specific numeric criteria or the narrative criterion or biological criteria would result in only a partially effective State toxics control program." For determining whether there is reasonable potential for an excursion above this narrative objective, the Regional Board used the second method prescribed by 40 CFR 122.44(d)(vi) for determining reasonable potential, which relies on USEPA criteria and other information. The Regional Board chose this method because USEPA's recommended ambient water quality criteria for chlorine have been developed using methodologies that are subject to public review, as is the individual recommended criteria guidance document. USEPA's ambient water quality criteria for protection of aquatic life are 11 µg/L(ppb) as a 4-day average (chronic) concentration, and 19 µg/L(ppb) as a 1-hour average (acute) concentration for total residual chlorine. Based upon results of monitoring, the Regional Board finds that the discharge does have a reasonable potential to cause or contribute to an in-stream excursion above a water quality objective. This Order includes new maximum daily(0.02 mg/L(ppm)) and average monthly(0.01 mg/L (ppm)) effluent limitations for residual chlorine based upon the USEPA criteria. Previous Orders did not include effluent limitations for chlorine, and it is unknown whether the Discharger can immediately comply with these new limitations. Toxicity In the past, results of effluent chronic toxicity testing using EPA/600/4-91/002 have indicated sporadic instances of sub lethal test organism impacts. Also,previous Order No. 93-221 included an effluent limitation for acute toxicity. This new Order retains an effluent limitation for acute toxicity, and includes continued monitoring of effluent and receiving water for chronic toxicity. SRT/JMEAgenda