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an effluent limitation in the City's permit of 700 µmhos/cm EC for April through August at this <br /> time is not supported by the record." Our conclusion is based on the unique background and <br /> facts in this case, and this order shall not be regarded as precedential with respect to other <br /> proceedings or with respect to actions that may be appropriate at a future time. <br /> B. Relationship Between Total Concentrations and Dissolved Concentrations of Regulated <br /> Pollutants <br /> Contentions: The City contends that the numeric water quality objectives in the <br /> Basin Plan for iron and manganese are expressed as dissolved concentrations, but the permit <br /> applies the numeric objectives from the Basin Plan as limitations on the total concentration of the <br /> regulated constituents. The City contends that the effluent limitations for iron and manganese <br /> should be modified to account for the relationship between the total concentrations of the <br /> regulated constituents and the dissolved concentrations of those constituents. <br /> Findings: The effluent limitations for iron and manganese in the City's permit <br /> are the numeric water quality objectives listed in Table HL I of the Basin Plan, which is <br /> expressed as a limitation on the dissolved concentration of each constituent. Federal regulations <br /> require that NPDES permit limits must be expressed as limits on total recoverable metal. <br /> (40 C.F.R. § 122.45(c).) A chemical translator can be applied to make the conversion between <br /> the limits on the dissolved concentration of a regulated constituent and the total concentration in <br /> the effluent. Use of a translator does not modify the water quality objective in the Basin Plan, <br /> but it serves to translate the objective for the dissolved form of a constituent to a corresponding <br /> limit in the total recoverable form in order to comply with federal regulations. <br /> In the absence of evidence of proper site-specific translators for iron and <br /> manganese, the Regional Board applied a"default translator of 1"to develop the effluent <br /> limitations in the City's permit." The Regional Board response to the petition states that, if the <br /> City submits data that shows that the iron or manganese in the City's effluent has no reasonable <br /> 25 The effluent limitations on EC that may be included in the City's permit at a future time may be influenced by a <br /> number of factors including applicable water quality objectives, the EC of the receiving water, actions of other water <br /> users and dischargers to reduce salinity in the lower San Joaquin River and southern Delta,the effectiveness of <br /> source control measures implemented by the City,and the potential for further reductions of EC in the City's effluent <br /> through additional source control or other measures. <br /> " Application of a"default translator of I"assumes that the concentration of the dissolved concentration of a <br /> regulated constituent is equal to the total concentration of the constituent in the effluent. <br /> 15. <br />