SITE INFORMATION AND CORRESPONDENCE_2005-CURRENT

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numerical water quality objectives established in a Basin Plan for various reasons.20 Where there is substantial assimilative capacity available in the receiving water, effluent limitations established in individual permits may allow for concentrations of pollutants in effluent that exceed water quality objectives for the receiving water. For instances in which a receiving water has been classified as impaired pursuant to section 303(d) of the Clean Water Act, federal law provides for establishing a total maximum daily load (TMDL) for the pollutant involved and allocating allowable amounts of the regulated pollutant among the dischargers to the body of water involved.21 The TMDL process may result in allowing permit effluent limitations for some dischargers to exceed a numerical water quality objective in the Basin Plan provided that the TMDL implementation program leads to achieving the water quality objectives for the receiving water. In the present case, the record indicates that the 700 µmhos/cm EC receiving water objective for April through August in the southern Delta frequently is not met, and that requiring the City to comply with an effluent limitation of 700 µmhos/cm EC would not significantly change the EC of water in the southern Delta area. In addition, the State Board's 1991 and 1995 Delta Plans, Revised Water Right Decision 1641, and State Board Resolution No. 2004-0062 all establish that the intended implementation program for meeting the 700 µmhos/cm EC objective was based primarily upon providing increased flows,possible construction of salinity barriers, and reducing the salt load entering the San Joaquin River from irrigation return flows and groundwater. The causes and potential solutions to the salinity problems in the southern Delta are highly complex subjects that have received and are continuing to receive an unprecedented amount of attention from the State Board in the exercise of its coordinated authority over water rights and water quality. The southern Delta water quality objectives for EC referenced by the Regional Board were established in the State Board's 1995 Delta Plan. Although the ultimate solutions to southern Delta salinity problems have not yet been determined, previous actions 2° The"Policy for Implementation of Toxics Standards for Inland Surface Waters,Enclosed Bays and Estuaries of California,2000"(State Implementation Policy or SIP)provides a methodology for establishing numeric effluent limitation for priority pollutants as identified in the California Toxics Rule(CTR)(40 C.F.R. § 131.38). However, EC is not classified as a priority pollutant in the CTR. 21 33 U.S.C. § 1313(d). 13.