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REGIONAL BOARD RESPONSE (SWRCB/OCC FILE A-1483) -19- PETITION FOR REVIEW OF WASTE DISCHARGE REQUIREMENTS ORDER NOS. R5-2002-0083 AND R5-2002-0084 CITY OF STOCKTON REGIONAL WASTEWATER CONTROL FACILITY results in new water quality objective not adopted in accordance with Porter-Cologne, CEQA, and the APA. There are no findings of evidence to support this limit." This comment apparently stems from an error in the tentative permit. The tentative permit included 30- day average receiving water limitations for ambient pH, both for the required range (6.5-8.5) and the allowable change (0.5 units). However, this error was corrected in the late revisions. The 6.5-8.5 pH range must be applied instantaneously, whereas the 0.5 pH change can be applied over an averaging period. This is because the effects of change of pH within the optimum range have been shown to have a negligible impact on aquatic life as long as the optimal range is maintained. Information from the Stockton USGS flow monitoring station has shown that short-term "acute" dilution is very limited during tidal reversal and low net flow conditions. Therefore, the Basin Plan pH receiving water objectives were applied at end-of-pipe. "82. The Permit includes effluent limitations for copper, applied as total recoverable rather that: dissolved criteria. There are no findings and no evidence in the record to support this." Federal regulations require copper effluent limitations to be expressed in terns of total recoverable metals. 40 CFR 122.45(c) states, "All permit effluent limitations, standards, or prohibitions for a metal shall be expressed in terms of'total recoverable metal'as defined in 40 CFR part 136 unless: (1)An applicable effluent standard or limitation has been promulgated under the CWA and specifies the limitation for the metal in the dissolved or valent or total form; or (2)In establishing permit limitations on a case-by-case basis under§ 125.3, it is necessary to express the limitation on the metal in the dissolved or valent or total form to carry out the provisions of the CWA; or(3)All approved analytical methods for the metal inherently measure only its dissolved form (e.g., hexavalent chromium)." None of the exceptions to the use of total recoverable metals are applicable to this situation. FIFTH BASIS: EFFLUENT LIMITATIONS FOR HUMAN CARCINOGENS Stockton requests that the State Board direct the RWQCB to modify the effluent limitations for chloroform, dichloromethane, DBCM, BDCM, PCE,TCE, 1,1-DCE, and bis-2 ethylhexyl phthalate, and modify the findings and conclusions. "84. The Permit includes effluent limitations for chloroform, dichloromethane, DBCM, BDCM, PCE, TCE, 1,1 DCE, and bis-2 ethylhexyl phthalate based oil the CTR, the SIP, and the narrative toxicity objective. "85. The RWQCB acted arbitrarily and unreasonably in calculating the effluent limitations for chloroform, dichloromethane,DBCM,BDCM, PCE, TCE, 1,1-DCE, and bis-2 ethylhexyl phthalate, by adjusting the statistical procedures contained in the SIP. Additionally, the RWQCB acted arbitrarily and unreasonably when calculating the harmonic mean flow dilution to develop these effluent limitations." The Regional Board was not arbitrary or unreasonable in calculating effluent limitations. The SIP stipulates that the harmonic dilution is the harmonic mean river flow divided by the long-term average arithmetic mean effluent flow. The Regional Board determined that the arithmetic mean effluent flow