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INFORMATION SHEET ORI0 NO. R5-2004-0028 • 12 <br /> CITY OF MANTECA, CITY OF LATHROP AND DUTRA FARMS <br /> WASTEWATER QUALITY CONTROL FACILITY <br /> SAN JOAQUIN COUNTY <br /> provide municipal water supply with an acceptable TDS, any increase in salt concentration effectively <br /> reduces the available water supply in Southern California(Metropolitan Water District of Southern <br /> California, Salinity Management Study, 1998). <br /> Chloride concentrations in the effluent ranged from 100-230 mg/l with an average of 138 mg/1 based <br /> on 16 samples collected during 2002. Background concentrations in the San Joaquin River ranged <br /> from 51-170 mg/l with an average of 98 mg/l based on results from eleven samples collected during <br /> 2002. Both the receiving water and the effluent exceed the agricultural use-protective water quality <br /> limit of 106 mg/l,based on the narrative objective. <br /> Electrical conductivity(EC) shows reasonable potential to exceed water quality objectives in both the <br /> effluent and in the receiving water. A review of the Discharger's monitoring reports from January <br /> 1998 through December 2002 shows the annual average effluent EC is 1099 umhos/cm,the lowest <br /> monthly average is 819 umhos/cm, and the highest monthly average is 1300 umhos/cm. These levels <br /> exceed the applicable objectives. EC data collected at receiving water sample location Rl from <br /> January 2002 through December 2002 show that the conductivity in the receiving water ranged from <br /> 380 umhos/cm to 1100 umhos/cm and averaged 686 urnhos/cm in 12 sampling events. Hourly EC data <br /> collected at the Department of Water Resources (DWR)Mossdale monitoring station(RSAN087) from <br /> December 2000 through September 2002 show that the conductivity in the San Joaquin River ranged <br /> from 299 umhos/cm to 1131 umhos/cm and averaged 721 umhos/cm. San Joaquin River monitoring <br /> for electrical conductivity at Vemalis between 1985 and 1998 showed frequent exceedances of the EC <br /> water quality objectives (Reference Figure 1-3, Total Maximum Daily Load for Salinity and Boron in <br /> the Lower San Joaquin River (January 2002)). These data show that the receiving water frequently <br /> has no assimilative capacity for EC. An Effluent Limitation for electrical conductivity is included in <br /> this Order and is based on the Basin Plan water quality objective for electrical conductivity in the <br /> South Delta. <br /> The TDS, chloride, and electrical conductivity objectives and recommended levels are all measures of <br /> the salt content of the water. Compliance with the Effluent Limitations for electrical conductivity <br /> based on the Basin Plan seasonal water quality objectives of 700 umhos/cm and 1000 umhos/cm will <br /> be protective of the chloride and TDS recommended levels; therefore,no limitations are included for <br /> chloride and TDS. <br /> 9.3 Aluminum <br /> Aluminum concentrations in the effluent were detected in the range from 70 ug/l to 350 ug/1 in <br /> sampling conducted in 2002. Aluminum was detected in the receiving water(R-1) in the range from <br /> 420 ug/1 to 2200 ug/I in 12 samples collected between January 2002 and December 2002. Dissolved <br /> concentrations of aluminum in the effluent and the receiving water were significantly less than the <br /> totals listed above. The Basin Plan's chemical constituents water quality objective prohibits chemical <br /> constituents in concentrations that exceed state MCLS or that adversely affect beneficial uses. MUN is <br /> a beneficial use of the San Joaquin River. The Primary and Secondary MCLS for aluminum are 1000 <br /> ug/1 and 200 ug/l respectively. The Basin Plan contains a narrative toxicity objective. Consistent with <br /> 40 CFR 122.44(d),USEPA's Ambient Water Quality Criteria for protection of freshwater aquatic life <br />