FIELD DOCUMENTS AND WORK PLANS 2000-2003

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WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2002-XXXX 9 MARLEY COOLING TOWER COMPANY SAN JOAQUIN COUNTY (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 µg/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 allowance's (ECA's)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. 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. 21. Previous Order No. 93-221 included effluent limitations for total chromium based upon the protection of human health. For Chemical Constituents at page III-3.00, the Basin Plan states `At a minimum, water designated for use as domestic or municipal supply (MUN) shall not contain concentrations of chemical constituents in excess of the maximum contaminant levels (MCLS) specified in the following provisions of Title 22 of the California Code of Regulations...' As a result, and considering the fact that the Stockton Diverting Canal provides little or no dilution, this Order retains the 50 µg/L (ppb)monthly average effluent limitation for total chromium which is necessary to comply with the primary California MCL contained in Title 22, California Code of Regulations (CCR) and incorporated as chemical constituent water quality objectives in the Basin Plan. The Discharger operates treatment facilities specific to the removal of chromium. Results of effluent monitoring indicate the treatment facilities, when properly operated, are capable of reducing concentrations of total chromium below this existing limitation. 22. Previous Order No. 93-221 included effluent limitations for arsenic based upon the protection of human health. The Basin Plan.states that waters shall not contain chemical constituents in concentrations that adversely affect beneficial uses. At a minimum, water designated for use as domestic and/or municipal supply shall not contain concentrations of chemical constituents in excess of maximum contaminant levels (MCL's). The new USEPA primary MCL for arsenic is 10 µg/L (ppb). Federal regulations at 40 CFR Section 122.44(d)(1)(vi)(A) allow the state to establish effluent limitations using an explicit state policy interpreting its narrative objectives. Use of the USEPA Primary MCL is appropriate to implement the narrative chemical constituent objective. Results of effluent monitoring indicate concentrations of arsenic in the final effluent are below this existing limitation. Therefore,the existing monthly effluent limitation of 10 µg/L (ppb) for arsenic is retained in this new Order.