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RESPONSE TO WRITTEN COMMENTS -12- City Of Stockton - Regional Wastewater Control Facility NPDES No. CA0079138 26 April 2002 Board Meeting Additionally, the suggestion that ammonia limits greater than 2.0 mg/1 would somehow implicate antibacksliding is unfounded. These limits have been stayed and remanded. If challenged effluent limits trigger antibacksliding, the State Board's appeal process is a nullity. This makes no sense. RWQCB Response: Ammonia is a significant source of oxygen demand in the receiving water; therefore, a discussion of the dissolved oxygen (DO) impacts in the tentative order is relevant, especially considering the 303(d) listing of the Deep Water Ship Channel for DO. The Fact Sheet is in agreement with the City's comments, but the City's interpretation of the Board's conclusion is incorrect, "The Board's conclusion that the year-round limits on ammonia are necessary for DO protection is conclusory and not supported by any facts or data in the record." The Board has not made this conclusion. The Fact Sheet @ 28 states, "...evidence suggests that the Discharger is a seasonally significant contributor to the River's DO problem. It is likely that improvements for the removal of nitrogenous oxvgen demanding substances will be recommended at the end of the TMDL process. However, the final effluent limitations are not known at this time." The City states, "Additionally, the suggestion that ammonia limits greater than 2.0 mg/1 would somehow implicate antibacksliding is unfounded." This presumption by the City is not evident in the tentative order. IV. Other Parameters Stockton Comment No. IV.A (Chlorine Limitations): The existing permit contains stringent chlorine limitations that were approved by the Board as protective of aquatic life. See, Order 94-324. The new permit (Finding 32) seeks to impose a more restrictive averaging period and effluent limits with respect to chlorine. This action is proposed even though there is no information presented in the record indicating that the current limitations are, in any way, inadequately protective. Thus, the finding is conclusory and insufficient to justify a change in effluent limitations. RWQCB Response: The chorine residual limitations in the 1994 Permit were based on receiving water studies performed by the Sacramento Regional Wastewater Authority for its discharge into the Sacramento River, because similar studies had not yet been performed by Stockton. The USGS SJR flow gauge at Stockton has since been installed and much more information is available regarding the Stockton discharge conditions. The tidal conditions in the SJR at Stockton are vastly different than in the Sacramento River in the vicinity of the Sacramento Regional discharge. Chlorine can cause toxicity to aquatic organisms when discharged to surface waters. U.S. EPA recommends, in its Ambient Water Quality Criteria for the Protection of Fresh Water Aquatic Life, that chlorine concentrations not exceed 0.02 mg/1 as a 1-hour average and 0.01 mg/1 as a 4-day average. The use of chlorine presents a reasonable potential that it could be discharged in toxic concentrations. The federal regulations at 40 CFR section 122.44(d)(1)(vi)(B), allows the state to establish the effluent limitation using EPA's water quality criteria. Water Code Section 13241 does