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WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2004-0028 -13- WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2004-0028 -14- CITY OF MANTECA,CITY OF LATHROP AND DUTRA FARMS CITY OF MANTECA,CITY OF LATHROP AND DUTRA FARMS WASTEWATER QUALITY CONTROL FACILITY WASTEWATER QUALITY CONTROL FACILITY SAN JOAQUIN COUNTY SAN JOAQUIN COUNTY will provide protection to the benthic community and minimize the impacts of the discharge to calculations outlined in the TSD. The calculated effluent limitations for cyanide are 3.7 ug/1 as a the river. monthly average and 10.0 ug/1 as a daily maximum(see Table 11 of the Information Sheet). The overlap of the plumes from the City of Manteca and the Brown Sand impoundment will 34. Arsenic: Arsenic is an inorganic priority pollutant that produces human health effects and is limit the extent of a mixing zone for arsenic,a constituent of mutual concern between these considered a carcinogen. Data,submitted by the discharger between January 2002 and discharges. Additionally,the receiving water monitoring shows an average arsenic December 2002,indicates arsenic is present in the effluent at levels that exceed the water quality concentration of 3.0 ug/1,exceeding the USEPA recommended water quality criterion for objective for arsenic contained in the Basin Plan(Table 111-1). The Basin Plan numeric protection of human health. The receiving water lacks assimilative capacity for arsenic. There objective for the San Joaquin-Sacramento Delta is 10 ug/l. Also,the new USEPA Primary MCL is no dilution available for arsenic under these conditions. for arsenic is 10 ug/l. The maximum concentration in the effluent is 14 ug/l. The Regional Board finds that there is a reasonable potential for the discharge to cause or contribute to an The assimilative capacity of the receiving water is dependent on the background concentration of excursion above the numeric water quality objective for arsenic. An effluent limitation for the receiving water. Data collected in 2002 indicates that the receiving water has no assimilative arsenic is included in this Order based on the Basin Plan numeric objective and the calculations capacity,and therefore no dilution can be granted for aluminum,electrical conductivity,iron, outlined in Section 5.4.4 of the TSD. The effluent limitation for arsenic is 10 ug/1 as a monthly manganese,and mercury. average(see Table 11 of the Information Sheet). Human health-based criteria that are based on safe-exposure levels for lifetime exposure(e.g., 35. Total Trihalomethanes and Chloroform: Information submitted by the Discharger indicate cancer risk estimates)utilize the harmonic mean flow to represent the receiving water flow. A that the effluent contains trihalomethanes(THMs)and chloroform. The Basin Plan contains the steady state analysis utilizing the harmonic mean flow at Vernalis provides a dilution of 222:1. "Chemical Constituent"objective that requires,at a minimum,that waters with a designated The Regional Board is not required to grant a mixing zone or allocate the full assimilative MUN use not exceed California MCLS. In addition,the Chemical Constituent objective capacity of the receiving water. For limitations based on these human health criteria,dilution is prohibits chemical constituents in concentrations that adversely affect beneficial uses. The limited to the amount required to maintain compliance. Where the ambient background California's Drinking Water Standard primary MCL for total THMs is 100 ug/1. The USEPA concentrations are lower than the applicable human health criterion,the dilution credits primary MCL for total THMs is 80 ug/l,which was effective on 1 January 2002 for surface determined in Table 12 of the Information Sheet apply for the determination of effluent water systems that serve more than 10,000 people. Pursuant to the Safe Drinking Water Act, limitations for carcinogens. DHS must revise the current total THMs MCL in Title 22 CCR to be as low or lower than the USEPA MCL. The State Board,in WQO No 2003-0002,stated that the Drinking Water PRIORITY POLLUTANTS Standard primary MCL for total THMs,which includes chloroform,of 80 ug/l could be applied to address chloroform in the discharge regulated in that Order. In addition,the Cal/EPA Office 32. Copper: The Report of Waste Discharge submitted by the Discharger indicates the presence of of Environmental Health Hazard Assessment(OEHHA)has published the Toxicity Criteria copper at levels that exceed the numeric water quality objective for copper contained in the Database,which contains cancer potency factors for chemicals,including chloroform,that have Basin Plan(Table III-1). Based on twelve effluent samples,the maximum reported copper value been used as a basis for regulatory actions by the regional boards,departments and offices within is 13 ug/l,which is within a range that may cause the receiving stream to exceed the water Cal/EPA. This cancer potency factor is equivalent to a concentration in drinking water of 1.1 quality objective for copper. Copper toxicity is hardness dependent and data submitted by the ug/l(ppb)at the 1-in-a-million cancer risk level with the consumption of the drinking water over Discharger indicates a worst-case effluent hardness concentration of 170 mg/1 as CaCO3. Based a 70-year lifetime. This risk level is consistent with that used by the Department of Health on a hardness of 170 mg/l,the calculated hardness dependent copper effluent limitations are 7.9 Services(DHS)to set de minimis risks from involuntary exposure to carcinogens in drinking ug/1 as a monthly average and 10.4 ug/1 as a daily maximum. Effluent limitations for copper are water in developing MCLS and Action Levels and by OEHHA to set negligible cancer risks in included in this Order for the protection of freshwater species,and are based on the Basin Plan developing Public Health Goals for drinking water. The one-in-a-million cancer risk level is objective. The determination of the final effluent limitations,which are hardness dependent,are also mandated by USEPA in applying human health protective criteria contained in the National summarized in Table 11 of the Information Sheet. Toxics Rule and the California Toxics Rule to priority toxic pollutants in California surface waters. 33. Cyanide: The Report of Waste Discharge submitted by the Discharger indicates the presence of cyanide at levels that exceed the water quality objective for cyanide contained in the Basin Plan Municipal and domestic supply is a designated beneficial use of the receiving water. However, (Table III-1). Based on twelve effluent samples,the maximum reported cyanide value is 31 ug/l, there are no known drinking water intakes on the San Joaquin River within several miles which may cause the receiving stream to exceed the Basin Plan objective of 0.01 mg/l. Effluent downstream of the discharge,and chloroform is a non-conservative pollutant. Therefore,to limitations for cyanide are included in this Order based on the Basin Plan objective and protect the MUN use of the receiving waters,the Regional Board finds that,in this specific circumstance,application of the USEPA MCL for total THMs for the effluent is appropriate,as