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MARLEY COOLLNG TOWEh SWIPANY • 4 <br /> GROUNDWATER EXTRACTION AMD TREATMENT SYSTEM <br /> SAN JOAQUINCOUNTY <br /> RESPONSE TO COMMENTS <br /> 30 January 2003 <br /> existing aquatic life and habitat in water bodies, including the SDC, influenced by <br /> the discharge. Therefore Regional Board staff found that aquatic life ber:eucial <br /> uses are existing uses of the SDC. <br /> Regarding municipal and domestic supply beneficial uses, State Board Resolution <br /> 88-63 designates all the waters of the state as sources or potential sources of <br /> drinking water. Consistent with Resolution 88-63,Regional Board staff <br /> considered the SDC to have MCN beneficial use. <br /> A review of the SWRCB Division of Water Rights geographical information <br /> system indicates that there are several active irrigation water rights permits <br /> downstream of the discharge. <br /> Water Quality Standards, Reasonable Potential <br /> Water quality standards and chemical specific criteria were established in the <br /> LiSEPA's California Toxics Rule (CTR) and National Toxics Rule Q TR). <br /> Protocols for implementing the CTR/NIR and assessing reasonable potential and <br /> establishing effluent limitations where required are provided by the State Water <br /> Resources Control Board's (SWRCB's) Policy for Implementation of Toxics <br /> Standards for Inland Surface Waters, Enclosed Bays, and Estuaries of California <br /> (known as the State Implementation Policy or SIP). These documents were the <br /> basis for assessing reasonable potential and establishing effluent limitations for <br /> the MCTC discharge. <br /> Federal regulations and the SIP require effluent limitations for all pollutants that <br /> are or may be discharged at a level that will cause or have the reasonable potential <br /> to cause, or contribute to an in-stream excursion above a narrative or numeric <br /> water quality standard. Considering the presence of freshwater aquatic habitat in <br /> the SDC, a reasonable potential analysis was conducted in accordance with the <br /> SIP Section 1.2 and Section 1.3 for each inorganic pollutant identified in the CTR <br /> using available, representative effluent data. When effluent data were compared <br /> with aquatic life water quality criteria established in the CTR,reported maximum <br /> effluent concentrations of copper and hexavalent chromium were found to exceed <br /> adjusted pollutant criteria. In accordance with the SIP Section 1.3, effluent <br /> limitations for these pollutants are required. <br /> Effluent Limits Based Upon Aquatic Life Beneficial Uses <br /> New- effluent limitations for hexavalent chromium and copper were established in <br /> this TO. Permit effluent limitations for copper and hexavalent chromium were <br /> developed using methodologies prescribed by the SIP Section 1.4. Considering <br /> that the SDC may at times provide little or no assimilative capacity, final water <br /> quality based effluent limitations were developed using a steady state model,with <br /> no credit provided for dilution. <br />