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City of Stockton and County of San Joaquin Page 28 <br /> NPDES Permit CAS0083470 <br /> Response to Comments <br /> concentrations of PCBs in catfish and large mouth bass collected from Smith Canal contain about <br /> 100 ng/g wet weight of the PCB Aroclors, which is about five times the allowed screening value for <br /> protection of humans who use PCB contaminated fish as food. The San Joaquin County <br /> Department of Public Health has issued a no-consumption health advisory for the Deep-Water <br /> Channel because of PCBs, dioxin and furans. The California Office of Environmental Health <br /> Hazard Assessment has issued a Delta-wide health advisory for mercury. <br /> Recent tests confirm that sediments collected from Yosemite Lake at the head of Smith Canal are <br /> toxic to benthic amphipods. These sediments contain about 1,000 ng/g dry weight of PCB <br /> congeners and aroclors. Analysis shows that PCBs have bioaccumulated in Lumbriculus <br /> (anoligoehaete-worm). The higher concentration of sediment PCBs at the head of Smith Canal as <br /> compared to the confluence with the San Joaquin River demonstrate that the likely source of the <br /> PCBs are the storm sewers that drain several areas of Central Stockton into Yosemite Lake. <br /> Preliminary Assessment of the Bioaccumulation ofPCBs and Organochlorine Pesticides in <br /> Lumbriculus variegatus from City of Stockton Smith Canal Sediments and Toxicity of City of <br /> Stockton Smith Canal Sediments to Hyatella azteca, G. Fred Lee and Assoc., July 2002. <br /> Delta waterways are listed on the 1998 California 303(d)List and TMDL Priority!Schedule as a <br /> Water Quality Limited Segment because of chlorpyrifos,DDT, diazinon, electrical conductivity, <br /> group A pesticides, mercury, organic enrichment/low dissolved oxygen and unknown toxicity. The <br /> San Joaquin River is listed as impaired because of selenium, boron, electrical conductivity, <br /> diazinon, chlorpyrifos, DDT, group A pesticides and unknown toxicity. Five-Mile and Mosher <br /> Sloughs are identified as impaired because of diazinon and chlorpyrifos. The Deep-Water Channel <br /> is identified as impaired because of PCBs, dioxin and furans. The identified source of impairment <br /> caused by chlorpyrifos, diazinon and low dissolved oxygen in Delta waterways includes"Municipal <br /> Point Sources and Urban Runoff/Storm Sewers." The identified source of diazinon, chlorpyrifos <br /> impairment in Five-Mile and Mosher Sloughs are"Municipal Point Sources and Urban <br /> Runoff/Storm Sewers." <br /> Regional Board staff has proposed significant additional listings of impairment (Staff Report on <br /> Recommended Changes to California's Clean Water Act Section 303(d)List, September 2001). <br /> Mosher Slough is proposed to be added because of dissolved oxygen and pathogens; Five Mile <br /> Slough because of dissolved oxygen and pathogens; the Calaveras River because of diazinon, <br /> dissolved oxygen and pathogens; Smith Canal is because of dissolved oxygen and <br /> organophosphorus pesticides; Mormon Slough because of dissolved oxygen and pathogens; the <br /> Stockton Deep-Water Channel because of pathogens; Walker Slough because of diazinon and <br /> pathogens and the San Joaquin River because of mercury. State Board staff have accepted these <br /> Regional Board recommendations. Staff Report, Volume I, Revision of the Clean Water Act Section <br /> 303(d)List Of Water Quality Limited Segments (draft), April 2002. The sources of impairments to <br /> urban waterways are identified as"Urban Runoff/Storm Sewers." <br /> The Delta and San Joaquin River are identified as Toxic Hot Spots pursuant to California's Bay <br /> Protection and Toxic Cleanup Program because of oxygen demand constituents, diazinon and <br /> chlorpyrifos (Consolidated Toxic Hot Spots Cleanup Plan, Volume I.Policy, Toxic Hot Spots List <br /> and Findings, SWRCB, June 1999). Mosher,Five-Mile and Mormon Sloughs and the Calaveras <br />