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WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2003-x= :2 SPX CORPORATION MARLEY COOLING TOWER COMPANY SAN JOAQUIN COUNTY umhos/cm EC during summer months (April through August) and 1000 umhos/em EC dn:�g the remainder of the year. As noted previously, the summer months coincide with the lowe_, reported flows in the SDC, when limited or no water is available due to the diversion for AGR use upstream of the SDC. The appropriate TDS water quality criteria concentration for ACR in the SDC downstream of the discharge may be influenced by other conditions including s specific soil types and precipitation patterns. Evaluation of these factors may result in the protective water quality criteria for the AGR beneficial remaining below, or adjusted abo- e:he criteria concentration protective of the MUN beneficial use. At this time it is not known-,k' ether the criteria for MUN or AGR is controlling. Provisions of this Order allow the Discharg_ ame to; study the hydrologic characteristics of the SDC, consider the Basin Plan amendment process and de-designation of beneficial uses, study site specific conditions that affect the AGR w=,er quality criteria concentration, and/or, evaluate alternative treatment or disposal options. W:rhout new information concerning site specific conditions and water quality criteria concentraticzs protective of the AGR beneficial use, it may be necessary to reduce the current final efflu-t limitation from 500 mg/l to 450 mg/1 during the summer months. Upon conclusion of tLe studies, this Order may be reopened to consider any new information and modification e` effluent limitation. 25. Results of monitoring submitted by the Discharger for the period of January 2001 throu May 2002 indicate effluent chlorine residual concentrations have ranged from less than detec:_'*le concentrations to 0.2 milligrams per liter(ppm) (13 June 2001). The Basin Plan does not provide a numeric water quality objective for chlorine, but the B_=m Plan does contain a narrative toxicity objective. At p.HI-9.00 the Basin Plan provides that rel—t—.- to toxicity: "All waters shall be maintained free of toxic substances in concentrations that-r:,:i;ce detrimental physiological responses in human,plant, animal, or aquatic life." At page 1. e USEPA's Technical Support Document for Water Quality-based Toxics Control (TSD)^-: ides that"Where States have not developed chemical specific numeric criteria, States may in.=ret their narrative standards for specific chemicals by using EPA criteria updated with surra quantitative risk values." The TSD further states on page 1 "The integrated approach mx,: include the control of toxics through implementation of the "no toxics"criterion and/or naneric criteria for the parameter of toxicity, the control of individual pollutants for which speci,- chemical water quality criteria exist in a state's standard, as well as the use of biologics._-r teria. Reliance solelv on the chemical specific numeric criteria or the narrative criterion or b c::gical criteria would result in only a partially effective State torics control program." For determining whether there is reasonable potential for an excursion above this narrativ e objective, the Regional Board used the second method prescribed by 40 CFR 122.44(dkx_, -or determining reasonable potential, which relies on USEPA criteria and other information. _'ne Retdonal Board chose this method because USEPA's recommended ambient water quaL-i criteria for chlorine have been developed using methodologies that are subject to public —.-:,W, as is the individual recommended criteria guidance document. USEPA's ambient water t:_ality criteria for protection of aquatic life are 11 µg/L (ppb) as a 4-day average (chronic)