SITE INFORMATION AND CORRESPONDENCE_CASE 2

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CENTRAL VALLEY WATER BOA - RESPONSE {SWRCB/OCC File A-1846 -3- PETITIONS FOR REVIEW OF WA-,TE DISCHARGE REQUIREMENTS ORDER NO. R5-2007-0036 (NPDES NO. CA0079154) AND TIME SCHEDULE ORDER NO. R5-2007-0037 CITY OF TRACY, WASTEWATER TREATMENT PLANT In addition to the average weekly and average monthly effluent limitations required in 40 CFR Part 133, a daily maximum effluent limitation for BODS and TSS was included in the Tracy Permit to ensure that the treatment works are not organically overloaded and operate in accordance with design capabilities. The Central Valley Water Board made the requisite impracticability finding in the permit findings; see Fact Sheet page F-13. Aluminum, Total Residual Chlorine, Ammonia, Dissolved Oxygen, Copper, Dichlorobromomethane, and Chlorodibromomethane. Title 40 CFR 122.45 (d) requires average weekly and average monthly discharge limitations for publicly owned treatment works (POTWs) unless impracticable. However, for toxic pollutants and pollutant parameters in water quality permitting, the USEPA Technical Support Document for Water Quality-Based Toxics Control (EPA/505/2-90-001) (TSD) recommends the use of a maximum daily effluent limitation in lieu of average weekly effluent limitations for two reasons. "First, the basis for the 7-day average for POTWs derives from the secondary treatment requirements. This basis is not related to the need for assuring achievement of water quality standards. Second, a 7-day average, which could comprise up to seven or more daily samples, could average out peak toxic concentrations and therefore the discharge's potential for causing acute toxic effects would be missed." (TSD, pg. 96.) The Tracy Permit utilizes maximum daily effluent limitations in lieu of average weekly effluent limitations for ammonia, aluminum, chlorine residual', copper, iron, dichlorobromomethane, chlorodibromomethane, and dissolved oxygen as recommended by the TSD for the achievement of water quality standards and for the protection of the beneficial uses of the receiving stream. Furthermore, copper, dichlorobromomethane, and chlorodibromomethane are priority pollutants, the regulation of which is subject to the State Water Boards' Policy for Implementation of Toxics Standards for Inland Surface Waters, Enclosed Bays, and Estuaries of California (State Implementation Policy or SIP). Section 1.4 of the SIP require water quality-based effluent limitations for priority pollutants to be set as average monthly and maximum daily effluent limitations, including human health criteria that are based in part on long-term exposure. The SIP clearly states that this applies to POTWs in Section 1.4, step 5, which states that "maximum daily effluent limitations shall be used for publicly-owned treatment works (POTWs) in place of average weekly limitations." The State Water Board has ruled that instantaneous or daily maximum limits are appropriate for toxic pollutants because longer-term limits are impracticable for the reasons stated above. (Order WQO 2002-0012 [East Bay Municipal Utility District], pp. 20-21.) The Central Valley Water Board included the necessary findings in the Fact Sheet. (See page F-53.) Iron. The Water Quality Control Plan, Fourth Edition (Revised August 2006), for the Sacramento and San Joaquin River Basins (hereinafter Basin Plan) contains a site-specific numeric objective for the Delta of 300 Ng/L for iron, which is expressed as a maximum The Tracy Permit applies the USEPA National Ambient Water Quality Criteria for chlorine directly as effluent limitations (1 hour average, acute, and 4-day average, chronic).