ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2004-0028 -19- WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2004-0028 -20- 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 in-stream excursion above water quality standards for nitrite and nitrate because of the Chloride concentrations in the effluent ranged from 100-230 mg/1 with an average of 138 mg/1 nitrification and denitrification processes. Effluent limits for nitrite and nitrate are based on the based on 16 samples collected during 2002. Background concentrations in the San Joaquin MCLS. Effluent Limitations for nitrite and nitrate are included in this Order to assure the River ranged from 51-170 mg/1 with an average of 98 mg/1 based on results from eleven samples treatment process adequately nitrifies and denitrifies the waste stream to protect the beneficial collected during 2002. Both the receiving water and the effluent exceed the water quality uses of municipal and domestic supply. objective of 106 mg/1 based on the narrative objective. 45. Salinity: The discharge contains total dissolved solids(TDS),chloride and electrical Electrical conductivity(EC)shows reasonable potential to exceed water quality objectives in conductivity. These are water quality parameters that are typically indicative of the salinity of both the effluent and in the receiving water. A review of the Discharger's monitoring reports the water. Their presence in water can be growth limiting to certain agricultural crops and can from January 1998 through December 2002 shows the annual average effluent EC is 1099 affect the taste of the water for human consumption. There are no USEPA water quality criteria umhos/cm,the lowest monthly average is 819 umhos/cm,and the highest monthly average is for protection of aquatic organisms for these constituents. The Basin Plan"Chemical 1300 umhos/cm. These levels exceed the applicable objectives. EC data collected at receiving Constituent"objective incorporates state MCLS,contains a narrative objective,and contains water sample location R1 from January 2002 through December 2002 show that the conductivity numeric water quality objectives for electrical conductivity. The secondary California maximum in the receiving water ranged from 380 umhos/cm to 1100 umhos/cm and averaged 686 contaminant level(MCL)for TDS is 500 mg/1 as a recommended level,1000 mg/1 as an upper umhos/cm in 12 sampling events. Hourly EC data collected at the Department of Water level,and Resources(DWR)Mossdale monitoring station(RSAN087)from December 2000 through 1500 mg/1 as a short-term maximum. The recommended agricultural water quality goal for TDS, September 2002 show that the conductivity in the San Joaquin River ranged from 299 umbos/cm that would implement the narrative"Chemical Constituent"objective,is 450 mg/1 as a long-term to 1131 umhos/cm and averaged 721 umhos/cm. San Joaquin River monitoring for electrical average based on Water Quality for Agriculture,Food and Agriculture Organization of the conductivity at Vernalis between 1985 and 1998 showed frequent exceedances of the EC water United Nations—Irrigation and Drainage Paper No.29,Rev.1(R.S.Ayers and D.W.Westcot, quality objectives(Reference Figure 1-3,Total Maximum Daily Load for Salinity and Boron in Rome,1985). The recommended agricultural water quality goal for chloride,that would the Lower San Joaquin River(January 2002)). These data show that the receiving water implement the narrative"Chemical Constituent"objective,is 106 mg/1 based on Water Quality frequently has no assimilative capacity for EC. An Effluent Limitation for electrical for Agriculture,Food and Agriculture Organization of the United Nations Irrigationand conductivity is included in this Order and is based on the Basin Plan water quality objective for Drainage Paper No.29,Rev.1(R.S.Ayers and D.W.Westcot,Rome,1985). The Basin Plan electrical conductivity in the South Delta. water quality objectives for electrical conductivity for the South Delta are 700 umhos/cm(from 1 April to 31 August)and 1000 umhos/cm(from 1 September to 31 March). State Board The TDS,chloride,and electrical conductivity objectives and recommended levels are all Decision 1641(D-1641)requires that the 1000 umhos/cm objective be met year round until measures of the salt content of the water. Compliance with the Effluent Limitations for electrical 1 April 2005 at which time the seasonal objectives will be effective. conductivity based on the Basin Plan seasonal water quality objectives of 700 umhos/cm and 1000 umhos/cm will be protective of the chloride and TDS recommended levels;therefore,no A review of the Discharger's monitoring reports from January 1998 through December 2002 limitations are included for chloride and TDS. indicates an annual average TDS effluent concentration of 634 mg/l,a lowest monthly average of 540 mg/l,and a highest monthly average of 727 mg/l. These concentrations exceed the 46. Aluminum: Aluminum concentrations in the effluent were detected in the range of 70 ug/L to applicable objectives. Limited TDS data collected at receiving water sample location RI from 350 ug/L in 12 samples collected between January 2002 and December 2002. Aluminum was January 2002 through December 2002 showed a TDS concentration range from 210 mg/1 to 1300 detected in the receiving water(R-1)in the range of 420 ug/L to 2200 ug/L in 12 samples mg/1 with an average of 500 mg/1 in 12 sampling events. The Regional Board report Total collected between January 2002 and December 2002. Dissolved concentrations of aluminum in Maximum Daily Load for Salinity and Boron in the Lower San Joaquin River(January 2002) the effluent and the receiving water were significantly less than the totals listed above. The presented monthly average TDS data for the San Joaquin River at Vernalis from October 1976 Basin Plan's chemical constituents water quality objective prohibits chemical constituents in through September 1997. The Vernalis data showed a maximum monthly average TDS of 1024 concentrations that exceed state MCLS or that adversely affect beneficial uses. MUN is a mg/1 with 57 of 252 months having monthly averages greater than 500 mg/l. This data indicates beneficial use of the San Joaquin River. The Primary and Secondary MCLS for aluminum are that the receiving water frequently exceeds water quality objectives to protect its beneficial uses 1000 ug/1 and 200 ug/1 respectively. The Basin Plan contains a narrative toxicity objective. and lacks assimilative capacity for TDS. As water exported from the Delta by the State Water Consistent with 40 CFR 122.44(d),USEPA's ambient Water Quality Criteria for protection of Project is,in part,mixed with Colorado River water to provide municipal water supply with an freshwater aquatic life for aluminum expressed as total recoverable are 750 ug/1(1-hour average) acceptable TDS,any increase in salt concentration effectively reduces the available water supply and 87 ug/1(4-day average),and are appropriate to implement the narrative toxicity objective. in Southern California(Metropolitan Water District of Southern California,Salinity Since both the receiving water and the effluent exceed USEPA's ambient water quality criteria Management Study,1998). and the secondary MCL,no dilution can be granted. The effluent has reasonable potential to cause or contribute to an in-stream excursion above water quality objectives for aluminum.