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..i <br /> WASTE DISCHARGE REQUIREMENTS -5- <br /> CITY OF STOCKTON <br /> REGIONAL WATER QUALITY CONTROL PLANT <br /> SAN JOAQUIN COUNTY <br /> of this permit, until such time as a full study has been conducted of all sources of oxygen <br /> demanding substances impacting this reach of the San Joaquin River, and appropriate corrective <br /> action is taken against other parties contributing to the problem. Accordingly, until such time <br /> as this study is completed and appropriate action is taken against other contributing parties, the <br /> Board does not intend to take action against the Discharger if the river fails to meet the <br /> dissolved oxygen objective, as long as the Discharger consistently achieves compliance with the <br /> new effluent Carbonaceous Biological Oxygen Demand and Ammonia effluent limitations in <br /> this permit. After completion of such a study, the Board may reconsider the Discharger's <br /> relative contribution to any remaining dissolved oxygen problem, and may make further <br /> adjustments in the Discharger's effluent limitations as is appropriate for the then-existing <br /> conditions. <br /> 19. The Department of Health Services recommended that wastewater discharged to receiving <br /> waters used for water contact recreation be sufficiently disinfected so that swimming would <br /> result in no more than 20 intestinal virus infections per 10,000 recreationist-days. It also <br /> provided a preliminary health risk assessment for contact recreation in the San Joaquin River in <br /> the vicinity of the discharge. The assessment indicated there may be a significant health risk <br /> due, in part, to minimal dilution flows. This Order requires a comprehensive health risk <br /> assessment be completed, and includes a reopener for addition of more stringent effluent <br /> limitations for disinfection, along with a time schedule for implementation. <br /> 20. This Order contains daily maximum effluent limitations for BOD, suspended solids, settleable <br /> solids, ammonia, total coliform organisms, and oil and grease, as allowed under state law. <br /> The daily maximums for BOD and TSS are based on professional judgement, having been <br /> found to be technically achievable at a properly operating treatment facility, and providing a <br /> maximum cap on the quantity of these substances which can be discharged within one day. <br /> 21. Order No. 86-088 required that, whenever a water quality based limitation for BOD of 10 mg/l <br /> was in effect, the limit for TSS also was set at 10 mg/1. The Discharger requested that TSS <br /> requirements remain at the technology-based limit (30 mg/1) during the entire year, and not <br /> continue to be decreased to 10 mg/I whenever water quality-based limitations were in effect for <br /> BOD, CBOD, or ammonia. Dissolved oxygen in the receiving water can be adequately <br /> regulated in the permit with the water quality-based limitations for CBOD and ammonia. <br /> Increasing the monthly average limitation for TSS to 30 mg/l is consistent with the <br /> antidegradation provisions of 40 CFR 131.12 and State Water Resources Control Board <br /> Resolution 68-16. Any impact on existing water quality will be insignificant. <br /> 22. The U.S. Environmental Protection Agency (EPA) and the Board have classified this discharge <br /> as a major discharge. <br /> 23. Federal regulations require effluent limitations for all pollutants that are or may be discharged at <br /> a level that will cause or have the reasonable potential to cause, or contribute to an in-stream <br />