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INFORMATION SHEET OR:NO. R5-2004-0028 14 CITY OF MANTECA, CITY OF LATHROP AND DUTRA FARMS WASTEWATER QUALITY CONTROL FACILITY SAN JOAQUIN COUNTY calculating Effluent Limitations for MBAS (see Table 6). Because of the observed foaming at the outfall, no dilution is available for MBAS. An Effluent Limitation for MBAS is included in this Order and is based on the Basin Plan water quality objectives for chemical constituents, floating material, and tastes and odors. 9.7 Molybdenum The recommended agricultural water quality goal for molybdenum, that would implement the narrative "Chemical Constituent"objective, is 10 ug/l based on Water Quality for Agriculture, Food and Agriculture Organization of the United Nations—Irrigation and Drainage Paper No. 29, Rev. 1 (R.S. Ayers and D.W. Westcot,Rome, 1985). Molybdenum was not monitored in the effluent or in the receiving waters. Because of the uncertainty associated with the lack of monitoring, additional studies of this constituent are warranted to more thoroughly evaluate reasonable potential for this constituent to exceed criteria. MRP No. R5-2004-0028 specifies monitoring for this pollutant. If the monitoring shows a reasonable potential to cause or contribute to an exceedance of a water quality objective, this Order may be reopened for addition of appropriate effluent limitations. 9.8 Carbofuran The Basin Plan contains a narrative objective for toxicity that prohibits concentrations of toxic substances that could produce detrimental physiological responses in humans. Public Health Goals published by OEHHA provide a measure of an amount of a toxic substance that, if exceeded could contribute to toxicity in humans who consume the water for municipal or domestic supply(MUN). MUN is a designated beneficial use of the receiving water. Carbofuran was detected in the effluent and receiving water at concentrations greater than the Public Health Goalof 1.7 ug/l. Because the data were greater than the method detection limit but less than the laboratory's reporting (quantitation) limit,the data were flagged as"detected but not quantified". Additional monitoring is required. If the monitoring shows a reasonable potential to cause or contribute to an exceedance of a water quality objective,this Order maybe reopened to consider incorporation of appropriate effluent limitations. 9.9 Nitrate and Nitrite Nitrate and nitrite are known to cause adverse health effects in humans. The Basin Plan's chemical constituents water quality objective prohibits chemical constituents in concentrations that exceed drinking water Maximum Contaminant Levels (MCLs)published in Title 22 of the California Code of Regulations or that adversely affect beneficial uses. Municipal and domestic water supply is a beneficial use of the San Joaquin River. The California Department of Health Services (DHS)has adopted Primary Maximum Contaminant Levels (MCLs) for the protection of human health for nitrite and nitrate that are equal to 1 mg/1 and 10 mg/l (measured as nitrogen), respectively. Title 22 CCR, Table 64431-A, also includes a primary MCL of 10,000 ug/l for the sum of nitrate and nitrite, measured as nitrogen. The discharge from the WQCF has a reasonable potential to cause or contribute to an in-stream excursion above water quality standards for nitrite and nitrate because of the nitrification and denitrification processes. Effluent limits for nitrite and nitrate are based on the MCLs. Effluent Limitations for nitrite and nitrate are included in this Order to assure the treatment process