SITE INFORMATION AND CORRESPONDENCE_CASE 2

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CENTRAL VALLEY WATER BOA RESPONSE {SWRCB/OCC File A-1846j,., 10- PETITIONS FOR REVIEW OF WA'S"rE DISCHARGE REQUIREMENTS ORDER NO. R5-2007-0036 (NPDES NO. CA0079154)AND TIME SCHEDULE ORDER NO. R5-2007-0037 CITY OF TRACY, WASTEWATER TREATMENT PLANT decreases the toxic effects to aquatic life) than the water hardness and pH values in which the criterion was developed, USEPA advises that a water effects ratio (WER) might be appropriate to better reflect the actual toxicity of aluminum to aquatic organisms. In May 2006, the Arid West Water Quality Research Project produced a research report, Evaluation of the EPA Recalculation Procedure in the Arid West Technical Report, to update NAWQC based on more recent data, and to recalculate these NAWQC to reflect the resident species observed in and West receiving waters. This research report states that "speciation and/or complexation of aluminum is highly dependent on ambient water quality characteristics and ultimately determines the mechanism of toxicity. [Increased] Concentrations of calcium in the water was shown to decrease toxic effects to fish." Based on the Arid West Technical Report, the Chronic Aluminum (total) Criterion Value is calculated as 911 pg/L for a hardness value of 100 mg/L as CaCO3. The City of Manteca completed an aluminum WER study (12 April 2007) for the San Joaquin River near its discharge point, which is located upstream of the confluence with Old River. The Manteca WER study, which may be used to calculate a WER for the City of Manteca's discharge, indicated that a WER of 22.7 can be applied to the chronic criterion for aluminum. Since the characteristics of the San Joaquin River (e.g. hardness and pH) near Manteca are similar to those in Old River near the City of Tracy discharge, the results of the Manteca WER study call into question the applicability of the chronic criterion recommended by the NAWQC for aluminum. Using the WER adjustment in accordance with the SIP, the applicable water quality criteria for aluminum for chronic exposure would be 22.7 x 87 pg/L or 1975 pg/L. Although the Manteca WER study was issued several weeks before the Central Valley Water Board issued the Tracy Permit, it was not available during the public comment period for the Tracy Permit, and staff had not had a chance to review the study or determine its applicability to Tracy. The Arid West Technical Report has not been approved by USEPA and has not received independent scientific peer review. But information in the Arid West Report and the Manteca WER study suggests that reconsideration of the aluminum limitations is appropriate. Since neither the Arid West Technical Report nor the Manteca WER are in the administrative record, the Central Valley Water Board recommends the State Water Board remand the permit for reconsideration of the aluminum effluent limitations. CONTENTION G: The Central Valley Water Board inappropriately used the Basin Plan's numeric site-specific copper objective rather than the criterion maximum concentration for copper included in the California Toxics Rule. The State Implementation Policy in the fourth footnote on Page 1 states, "If a water quality objective and a CTR criterion are in effect for the same priority pollutant, the more stringent of the two applies." Federal regulations in 40 CFR 131.38(c)(1) state, "The criteria in paragraph (b) of this section apply to the State's designated uses cited in paragraph (d) of