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..i REGIONAL BOARD RESPONSE (SA'RC&OCC FILE A-1483) -3- PETITION FOR REVIEW OF WASTE DISCHARGE REQUIREMENTS ORDER NOS. R5-2002-0083 AND R5-2002-0084 CITY OF STOCKTON REGIONAL WASTEWATER CONTROL FACILITY REGIONAL BOARD PERMITTING ACTIVITY The Regional Board adopted renewed Waste Discharge Requirements (WDRs) Order No. R5-2002-0083 (NPDES No. CA0079138) and Cease and Desist Order No. R5-2002-0084 at the 26 April 2002 Regional Board meeting. By letter dated 1 May 2002, the Regional Board transmitted the adopted Orders to the City and all interested parties. The administrative record for Order No. R5-2002-0083 was submitted to the State Board on 1 August 2002. The administrative record considered by the Regional Board in adopting Orders Nos. R5-2002-0083 and R5-2002-0084 includes information used in adopting Order No. 94-324, the previous permit for the facility. Records related to the previous permit are relevant to the new Orders because the previous permit was the subject of a State Board Order remanding that permit to the Regional Board. The current permit addresses issues raised in State Board Orders WQ 96-09 and WQ 95-1. In adopting Order No. 94-324, the Regional Board considered available information to determine dilution and the need for effluent limitations for a number of constituents. The permit included, in part, new limitations for ammonia based on that information. The City filed a petition with the State Board requesting review of WDR Order No. 94-324, and a stay of the ammonia effluent and the dissolved oxygen (DO) receiving water limitations: The State Board granted a stay in February 1995 in Order No. WQ 95-1. On 29 May 1996, the State Board issued Order No. WQ 96-09 in response to the City's petition. The State Board determined that the Regional Board made appropriate decisions in the permit given the information available at that time. The State Board,however, agreed that flow conditions in the receiving water had changed due to the adoption of the Bay-Delta Plan. Order No. WQ 96-09 remanded WDR Order No. 94-324 to the Regional Board for review and revision, and adoption of a Cease and Desist Order, but did not alter the stay of the ammonia effluent limitation. Ongoing studies for water quality and flow objectives surrounding the SJR and Delta were in development after the issuance of State Board Order WQ 96-09. The current permit under review addresses the issues of the remand by considering current information regarding available dilution. Based on that evaluation, the Regional Board approved significant changes from the previous permit, including: • Incorporation of Title 22 filtration/disinfection requirements • New ammonia limitations requiring nitrification facilities • New inorganic priority pollutant limitations • New organic priority pollutant limitations • New bioaccumulative priority pollutant limitations • New requirement to develop an offset program for mercury • New organophosphate pesticide limitations • Revised chlorine limitations • Revised pH limitations • Groundwater monitoring requirements • Additional study requirements The current permit includes water quality-based effluent limitations for ammonia, with which the Discharger is unable to comply. A compliance schedule to meet the new limitations was adopted by the