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RESPONSE TO WRITTEN COMMENTS -13- City Of Stockton -Regional Wastewater Control Facility NPDES No. CA0079138 26 April 2002 Board Meeting not apply to this circumstance. The RWCF has the ability to continuously monitor chlorine residual and can comply with the new limitations. Stockton Comment No._IV.B (Total Dissolved Solids): Permit Finding 36 concludes that a pollution prevention plan is necessary to ensure that the receiving water achieve water quality objectives for TDS. This conclusion is directly contradicted by other statements in Finding 36, in particular that (1) this segment of the river, unlike upstream segments, is not on a Section 303(d) list for TDS and therefore meets applicable objectives, (2) the data presented show that water quality objectives are achieved and (3) that assimilative capacity for TDS exists in the San Joaquin at Stockton. Given these findings, there is no basis to impose a pollution prevention plan as the current TDS discharge meets all applicable requirements. RWQCB Response: Finding 36 adequately documents the reasons for requiring a pollution prevention plan for TDS. Stockton Comment No. IV.0 (Disinfection Requirements): In the prior Order (94-324), the Board agreed that it was appropriate to defer imposition of more restrictive, Title 22-based coliform objectives and to implement a study to evaluate whether or not current plant performance posed a significant unacceptable health risk. These studies confirmed that the current Stockton discharge does not present any significant threat to public health. RWQCB Response: The bases for the disinfection requirements are adequately explained in Sections 9.1 and 9.2 of the Fact Sheet. Stockton Comment No. IV.D (Section 303(d) List Pollutants): The tentative order proposes stringent limits for a number of parameters, based upon the claim that downstream waters are impaired by these pollutants and that no assimilative capacity exists, therefore justifying either(1) end of pipe limits or(2) restrictive interim limits. In general, the Board is required to present the basis for the Section 303(d) listing in the record so that the need for an interim limit and the availability of assimilative capacity may be assessed. (See, Napa and Tosco decisions) RWQCB Response: The permit presents the basis for the reasonable potential determination for each constituent with a water quality based effluent limitation that is also on the 303(d) list. In each instance there is evidence in the record that assimilative capacity is not available for that constituent. In addition, the Department of Health Services has issued a health advisory for human consumption of fish from the Delta, due to concentrations of mercury, PCBs and other chemicals. Stockton Comment No. IV.D(1) (Diazinon): Limitations regarding this constituent are being imposed based upon recommendations from the Department of Fish and Game. The basis for the DFG recommendations are not in the record and the information showing when assimilative capacity may be limited is also not present. Because diazinon is generally an intermitter- non-point source problem -,,, x f ated with wet N,:<ather conditions, assimilative canacity wo, .d n cted to exist under dry „ _ather conditions. .ys dilution has been demons, .. .,i to exist in th. a,- Joaquin River,