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INFORMATION SHEET ORM NO. R5-2004-0028 22 CITY OF MANTECA, CITY OF LATHROP AND DUTRA FARMS WASTEWATER QUALITY CONTROL FACILITY SAN JOAQUIN COUNTY not protective of actual bioaccumulation conditions in the River. Health advisories by the Department of Health Services remain in effect for human consumption of fish in the Delta, including the San Joaquin River at Manteca, due to excessive concentrations of mercury in fish tissue. These current warnings and available fish tissue data confirm that there is currently no assimilative capacity in the Delta for mercury. Group A organo-chlorine pesticides, which include lindane, endrin aldehyde and DDT are also on the 303(d) listing. The Basin Plan sets forth a water quality objective that requires that organo-chlorine pesticides not be present in the water column in detectable concentrations. The SIP designates acceptable minimum laboratory detection levels for lindane, endrin aldehyde and DDT at 0.02 ug/1, 0.01 ug/1 and 0.01 ug/l, respectively. The organo-chlorine pesticide effluent concentrations and corresponding reporting levels are at or below the SIP minimum levels and meet the Basin Plan objective. Based on these considerations, effluent limitations for Group A pesticides are not required in this Order. Effluent samples collected from January 2002 to December 2002 contained mercury concentrations ranging from 0.013 ug/1 to 0.028 ug/l. Receiving water monitoring for mercury over the same period provided results ranging from 0.0036 ug/1 to 0.0093 ug/l. Table 14 summarizes the mercury data and statistics associated with the mercury results. The effluent and receiving water have also been monitored for Group A pesticides and PCBs on four occasions during 2002. Dioxin (2,3,7,8-TCDD)was monitored twice during 2002. These constituents were not detected in the effluent or receiving water samples. Detection limits for DDT, PCB and the 2,3,7,8-TCDD were not adequate to determine compliance with the water quality criteria, therefore continued monitoring is required in this Order. Table 10 summarizes these results. 11.3.1 Interim Requirements - Bioaccumulative Priority Pollutants The SIP recommends that the Regional Board consider whether the mass loading of bioaccumulative pollutants should be limited in the interim to "representative current levels"pending development of applicable water quality standards or TMDL allocation. The intent is, at a minimum, to prevent further impairment while a TMDL for a particular bioaccumulative constituent is being developed. Any increase in loading of mercury to an already impaired water body would further degrade water quality. An interim effluent mass limitation for mercury has been determined using the WQCF design flow of 8.11 mgd and the maximum observed concentration. The data and calculation, as summarized in Table 14,provided an interim yearly mass limitation for mercury of 0.69 pounds/year(as total recoverable). To track the Discharger's compliance with the interim mass limitation, the Discharger is required to calculate a 12-month consecutive running average of the mass loading for mercury. Starting on the 12`h month after adoption of this permit, and for every month thereafter,the total mass pollutant loading for the previous twelve months will be reported in the monthly discharge monitoring reports and compared against the interim mass limitation calculated in the previous section. In addition to the