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WASTE DISCHARGE REQUIREMENTS -10- CITY OF STOCKTON REGIONAL WASTEWATER CONTROL FACILITY SAN JOAQUIN COUNTY LATE REVISIONS additional studies of these constituents are warranted. The Monitoring and Reporting Program (MRP) No. R5-2002-_specifies monitoring for these pollutants. Based on the results of monitoring, this Order maybe reopened for addition of appropriate effluent limitatioi,s :or these pollutants. Dioxin/Furans and PCBs 29. There are insufficient monitoring data for dioxin/furans and PCBs at this time to determine if there is a reasonable potential for the discharge to cause, or contribute to an in-stream excursion above a narrative or numerical water quality standard for these pollutants. This Order includes a provision to require monitoring and evaluation of these pollutants for a designated amount of time. Upon completion of the monitoring the Order may be reopened for addition of effluent limitations for these pollutants. Mercury and GroUA A Pesticides 30. The Delta waterways are 303(d) listed as impaired for mercury and Group A organo- chlorine pesticides (Group A pesticides) based on bioaccumulation of these pollutants in fish tissue. The CTR contains criteria for mercury and Group A pesticides, however, those criteria do not address bioaccumulation in the river(Fact Sheet, 11.1). The RWCF effluent contains concentrations of mercury and Group A pesticides below CTR priority pollutant criteria, however, since the CTR criteria are not based on bioaccumulation, the discharge was evaluated based on the Basin Plan's narrative toxicity objective. Furthermore, the Basin Plan requires that Group A Pesticides not be present in the water column in detectable concentrations. Any loading of those pollutants from the discharge may have the reasonable potential to cause or contribute to an excursion above the narrative toxicity objective by causing bioaccumulation in fish tissue. As discussed further in the Fact Sheet, health advisories by the Department of Health Services remain in effect for human consumption of fish in the Delta, including the SJR at Stockton, due to excessive concentrations of mercury and G_,..,. ^ Pestioia in fish flesh. These current warnings and available fish tissue data confirm that there is currently no assimilative capacity for these pollutants. Therefore, water quality based effluent limitations for mercury, and Group A pesticides that properly address bioaccumulation and the non-detect Basin Plan objective are required. The TMDL for mercury is scheduled to be completed by December 2005. For situations like this, the SIP recommends that limiting mass loading of the bioaccumulative pollutant should be considered in the interim at representative, current levels pending development of the TMDL. For Group A Pesticides, the Basin Plan non-detect objective becomes the final effluent limitation. This Order also requires the Discharger to construct Title 22 tertiary treatment, or equivalent. facilities for pathogen removal by 1 May 2006. These facilities will provide improve, i 1s removal, and ther_:ore are likely to significantly reduce existing mercury and Gro. :;sticides muss u8 in the discharge.