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the Regional Board failed to consider the available dissolved/total ambient data and <br /> effluent data that demonstrate no such exceedances exist and instead applied a"worst <br /> case" total/dissolved metal translator to conclude dissolved levels were excessive. The <br /> Regional Board's approach is not supported by either (1) the available data or (2) the best <br /> scientific information on development of translators. <br /> First, there is no valid dissolved data for the receiving waters showing that <br /> exceedances exist or that a negligible translator (i.e., a translator near 1.0) should be used. <br /> Thus, there is no reliable basis to claim that the discharge is causing a water quality <br /> criteria exceedance. The available, reliable dissolved metals data for the City's effluent <br /> indicate that dissolved zinc does not exceed 100 ug/1 and that when elevated total <br /> recoverable zinc occurs (i.e., greater than 100 ug/1) the dissolved fraction decreases. (See, <br /> dissolved and total zinc monitoring data attached hereto at Table 1, Effluent Metals <br /> TestinD ta.) Thus, the Regional Board's assumed translator of 1.0 is not reasonable. <br /> Second, application of EPA's translator method would yield an effluent <br /> limitation for zinc that is at least twice that included in the proposed Permit. The Metals <br /> Translator: Guidance for Calculating a Total Recoverable Permit Limit from a <br /> Dissolved Criterion, USEPA OW 823-B-96-007 (June 1996), pp. 5-10 ("Translator <br /> Guidance") (Attachment 2). See also, Attachment 3 (application of Translator <br /> Guidance). Site-specific coefficients may be different than those used in calculation, but <br /> the principle is the same and the results should not differ drastically. If a zinc limitation <br /> is to be included in the permit, it should reflect the best estimate of the translator, not the <br /> most conservative. <br /> Third,it should be noted that there is no apparent toxicity caused by metals in the <br /> effluent based on the WET results obtained to date. The organisms used to conduct the <br /> chronic toxicity test (Ceriodaphnia) are extremely sensitive to zinc. If the zinc in the <br /> City's effluent were toxic, mortality impacts would be occurring. As such effects are not <br /> demonstrated by the whole effluent test results, it is apparent that the zinc in the effluent <br /> is not a threat to organisms in Dredger Cut. Therefore, there is no basis to conclude that <br /> the proposed zinc limitations are necessary to comply with narrative criteria. <br /> NPDESPermitCommenu Exhibit 2 Page 6 12/17/99 <br />