SITE INFORMATION AND CORRESPONDENCE_CASE 2

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CENTRAL VALLEY WATER BOP RESPONSE{SWRCB/OCC File A-1846; �_ PETITIONS FOR REVIEW OF WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2007-0036 (NPDES NO. CA0079154)AND TIME SCHEDULE ORDER NO. R5-2007-0037 CITY OF TRACY, WASTEWATER TREATMENT PLANT concentration. A maximum daily effluent limit of 300 Ng/L for total recoverable metal iron was included in the Tracy Permit, because the Basin Plan site-specific objective is expressed as a maximum concentration. It is impracticable to convert the site-specific numeric maximum concentration objective to weekly average and monthly average effluent limits, because there are no guidelines for converting the objective. pH. The Basin Plan includes numeric water quality,objectives that the pH "...not be depressed below 6.5 nor raised above 8.5. Changes in normal ambient pH levels shall not exceed 0.5 in fresh waters with designated COLD or WARM beneficial uses." (Basin Plan pg. III-6.0) The receiving water is designated as having both COLD and WARM beneficial uses. Effluent limitations for pH were included in the Tracy Permit based on the Basin Plan water quality objective for pH. The Tracy Permit includes instantaneous maximum and minimum pH effluent limitations of 8.5 and 6.5, respectively, which are applied to ensure compliance with the Basin Plan objective. It is impracticable to convert the instantaneous numeric objectives to average weekly and average monthly effluent limits because there are no guidelines for converting the objectives. Turbidity and Total Coliform. Title 22 requires that the effluent total coliform levels not exceed 2.2 MPN/100 ml as a 7-day median. The Tracy Permit includes this requirement as an effluent limitation based on Department of Public Health recommendations, as discussed under "BODS and TSS," above. Therefore, we believe it is appropriate and necessary to set effluent limitations for total coliform and that the Central Valley Water Board acted properly to set the total coliform effluent limitations to ensure compliance with Title 22 reclamation recommendations to protect public health. In addition to coliform testing, turbidity is another indicator of the effectiveness of the treatment process and turbidity monitoring can assure compliance with the required level of treatment. The Central Valley Water Board has typically used turbidity to measure or demonstrate the proper operation of the filtration treatment component. Historically these measurements were set as effluent limits and were reported as such; however, the effluent limitations were not intended to regulate turbidity in the receiving water. The Central Valley Water Board acted to correct the placement of turbidity controls in recent permits by removing the turbidity effluent limitations and establishing operational provisions that set numeric turbidity measures for the filtration system. This will ensure the treatment system is functioning properly and is producing a pathogen free effluent. Therefore, we believe the turbidity limitation should be an operational parameter to determine proper system function and not a water quality-based effluent limitation, as required in the Tracy Permit. Central Valley Water Board staff recommends that the Tracy Permit be remanded to reconsider the water quality-based effluent limitations for turbidity.