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MEMORANDUM CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 361-5600 Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 TO: Antonia Vorster a W� FROM: Christopher Foe Senior WRC Engineer) I Environmental Specialist Patricia Leary Assoc ate Engineer DATE: 14 August 1990 SIGNATURE: SUBJECT: REVIEW OF THE CITY OF STOCKTON'S 1989-90 BIOTOXICITY TECHNICAL REPORT We have reviewed the Technical Report (Engineering Science Inc, June 1990) which the City of Stockton has submitted summarizing its 1989-90 efforts to determine the cause of aquatic toxicity in its winter effluent. The City has not made any significant progress in completing the Toxicity Identification Evaluation/Toxicity Reduction Evaluation (TIE/TRE) work requested by Regional Board staff. As a result, the City can expect this winter to have violations of its effluent bioassay permit limit and to discharge effluent which is acutely toxic to both its test invertebrate and fish species. This is particularily serious as the City's effluent comprises most, if not all , of the volume of the San Joaquin River at their discharge point during part of the year. Therefore, it is reasonable to expect that the City has caused acute fish and invertebrate toxicity during the last two winters in the San Joaquin River and will continue to do so this year. The following is a more detailed review of past fish (Golden Shiner) and invertebrate (Ceriodaohnia) toxicity data submitted by the City of Stockton for its effluent and its recent TIE/TRE report, several recommendations are made for future work. 1. GOLDEN SHINER TOXICITY A. Background The City of Stockton is regulated under Waste Discharge Requirements, Order No. 86-088 (NPDES No. CA0079138) . Effluent Limitation No. 9 requires that the survival of test fish in 96 hour bioassays of undiluted waste shall not be less than 70% for any one bioassay nor less than 90% for the median of any three consecutive tests. Stockton performs weekly 96 hour static bioassays with Golden Shiner to assess compliance with this provision. Bioassay results are graphed in Figure 1 for the period of May 1988 to June 1990. The data demonstrate a pattern of significantly increased winter toxicity over the past two years, in violation of Waste Discharge Requirements. On 19 October 1989, Board staff requested the City of Stockton to develop a Technical Report outlining a TIE/TRE plan to determine the chemicals causing Golden Shiner toxicity. The plan was to be implemented upon the first indication of problems during the winter of 1989-1990. The City responded on 2 November 1989, promising to undertake a "directed TRE" to confirm or eliminate ammonia as the cause of fish toxicity following the protocols outlined in EPA/600/3-88/034 and additional EPA references as