SITE INFORMATION AND CORRESPONDENCE_2005-CURRENT

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objective (which incorporates the secondary maximum contaminant level (MCL)" for foaming agents) and on the Basin Plan narrative water quality objective for floating material, tastes and odors. The effluent limitation for aluminum was based on the narrative toxicity water quality objective in the Basin Plan and the narrative chemical constituents objective. In implementing the narrative water quality objective for aluminum, the Regional Board applied the numerical effluent limitation for aluminum specified in the USEPA Water Quality Criteria for the protection of Freshwater Aquatic Life as authorized by 40 Code of Federal Regulations part 122.44(d)(1)(vi)(B). Finally, the effluent limitation for EC was based on the water quality objective for the southem Delta referenced in Table III-5 of the Basin Plan (which was taken from the State Board's May 1991 "Water Quality Control Plan for Salinity, San Francisco Bay/Sacramento-San Joaquin Delta Estuary"). Water Code section 13263(a)provides that the requirements governing the discharge of waste under permits issued by the Regional Board must implement relevant water quality control plans. Water Code section 13377 requires that NPDES permits must ensure compliance with the Clean Water Act and with effluent limitations necessary to implement water quality control plans or protect.beneficial uses. Thus, in acting on the City's application for renewal of its NPDES permit, the Regional Board focused on implementation of established water quality objectives and other provisions of the Basin Plan rather than on re-examination of Basin Plan provisions. To implement previously adopted water quality control plans,permits must include effluent limitations for all pollutants that have a reasonable potential to cause or contribute to an excursion of water quality standards.12 Order No. R5-2004-0028 and the accompanying Information Sheet (Attachment"A" to the order)cite evidence in the record to support the Regional Board's findings that the City's discharge of treated effluent has a The secondary maximum contaminant level for MBAS is 0.5 mg/l. (Cal.Code Regs, tit. 22, § 64449.) 12 The term"reasonable potential"is based on 40 C.F.R. § 122.44(d)(1)(i),which requires that permit issuers include effluent limitations for all pollutants that"are or may be discharged at a level which will cause,have the reasonable potential to cause, or contribute to an excursion above any State water quality standard,including State narrative criteria for water quality." If a pollutant does not require a limit under this test,the pollutant is said not to have"reasonable potential." 5.