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INFORMATION SHEET • 9 WASTE DISCHARGE REQUIRMENTS ORDER NO.R5-2003-XXXX SPX CORPORATION MARLEY COOLING TOWER COMPANY STOCKTON, SAN JOAQUIN COUNTY 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. Hexavalent Chromium 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 l lµg/L (ppb), and a monthly average limitation for hexavalent chromium of 11 µg/L (ppb). New limits for hexavalent chromium have been established in this nen-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 pg/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 gg/L(ppb) and 11 µg/L (ppb)respectively). New water quality based effluent limitations have been calculated based upon methodologies in the SIP. 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 allowance's (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 (NOEL) were then calculated using multipliers in Table 2 of the SIP as shown below: WATER QUALITY BASED EFFLUENT LLNITTATIONS Hexavalent Chromium Number of Observations >20 Effluent Maximum 1; Dilution Credit 0 ECA acute 16 p,L Percent of Observations Below Detection >900/0 Coefficient of Variation(Default) 0.6 Limiting LTA(acute)= ECA acute 'Table 1 Acute Multiplier) 5.1 SamplingSamphng Frequency n <41110 A.MEL LTA•Table 2 AMEL Multiplier) ! 8.0 gzL b MDEL LTA'Table 2 MDEL Multiher) 1 16.0 ugL b New final average monthly(8.0 µg/L(ppb)) and daily maximum (16 µg/L (ppb)) effluent limitations for hexavalent chromium have been established in this Order in accordance with Sections 1.3 and 1.4 of the SIP. With proper operation of the existing treatment facilities, the Discharger is capable of meeting these new limitations, therefore a time schedule for compliance is not included in this new Order.