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e, lo./ STAFF REPORT -6- STOCKTON REGIONAL WASTEWATER CONTROL FACILrrY SAN JOAQUIN COUNTY issue, at this point in time it is unclear how the TMDL process will eventually influence the mercury discharge limitation of this facility. 8. Pesticides The presence of pesticides within the San Joaquin River has led to a 303(d) listing for the organo-chlorine pesticide DDT and the organo-phosphate pesticides diazinon and chlorpyrifos. The Basin Plan objective for organo-chlorine pesticides is non-detect and will need to be considered for permit renewal as the discharger reported detections of DDT and lindane. The Discharger has not analyzed diazinon and chlorpyrifos in the effluent. Board staff has requested Stockton to analyze organo-phosphate pesticides in the effluent prior to issuance of a tentative permit. Board staff will use the generated data that to evaluate if there is reasonable potential for the effluent to cause or contribute to violations of any narrative or numeric receiving water objectives for these constituents. 9. Pretreatment DeltaKeeper has expressed a concern with the pretreatment program currently in place. They are concerned that the existing pretreatment program is insufficiently staffed and is accepting wastewater that could severely impact the wastewater treatment facility and result in discharge of pollutants. Staff may need to conduct a pretreatment audit prior to renewal of the NPDES permit. If flaws are noted during the pretreatment audit, the permit or an appropriate enforcement order could be used to correct these problems. 10. Miscellaneous Issues In addition to the items discussed above, there are numerous miscellaneous issues that will also need to be addressed with the permit renewal. One such issue is the acidification of the effluent. Acidification of the effluent is performed by the Discharger to reduce the toxicity of the ammonia that is discharged. However, acidification has an additional side effect of increasing salt loading. Staff must consider whether additional salt loading should continue to be allowed into receiving waters. Other issues include compliance with the Thermal Plan, the possibility of incorporation of a flexible monitoring program,evaluation of the effect of the remaining combined sewer collection system, and numerous Delta water usage/management programs. TIME SCHEDULE As has been summarized, there are numerous complex issues that are required to be carefully reviewed and considered by staff as part of the Stockton's NPDES permit renewal. The existing workplan recommends that the Stockton NPDES permit be renewed within fiscal year 2000-2001. Staff estimates that a draft permit should be complete by December 2000.