SITE INFORMATION AND CORRESPONDENCE 1980-1999

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STAFF REPORT • 0 -2- WHITE SLOUGH WATER POLLUTION CONTROL PLANT SAN JOAQUIN COUNTY the effluent after 1 May 2004, weekly pH monitoring and quarterly priority pollutant monitoring for reclaimed water, daily monitoring of DO for receiving water location R-1, and monthly pH monitoring for the storage ponds. NPDES PERMIT The following is a summary of the major issues involving the NPDES Permit. 1. Dissolved Oxygen The Discharger has completed an expansion of its secondary domestic waste treatment capacity to 8.5 mgd, but the effluent flow rate allowed in the proposed permit has not been increased beyond 7.0 mgd due to concerns regarding the impact of the discharge on dissolved oxygen concentrations in the receiving water. The Basin Plan requires a year-round DO limit of 5.0 mg/1 in all Delta Waters. Self-monitoring receiving waters data have shown the discharge is causing or contributing to the DO violations within Dredger Cut. The proposed permit includes more stringent effluent limits for BOD than were imposed in the existing permit. This alone will not prevent excursions of the dissolved oxygen objective in Dredger Cut. Therefore, the proposed permit also requires the Discharger to maximize land disposal of effluent, and prohibits discharges when dissolved oxygen concentrations in Dredger Cut are less than 5 mg/1 and effluent contains less than 5 mg/l DO. The Discharger is not currently capable of meeting all of these requirements and therefore a CDO for BOD has also been proposed. 2. Disinfection The designated beneficial uses of Dredger Cut, White Slough and Bishop Cut include contact recreation and irrigation. Available data'have shown that minimal to no dilution exists within Dredger Cut and less than 20:1 dilution exists at the confluence of Dredger Cut and White Slough. The California Department of Health Services (DHS) recommends treatment levels to protect public health from both body contact water recreation and food crop irrigation. The DHS recommends that, in cases where relatively undiluted wastewater discharges are permitted to surface waters that have been identified by the Board to have beneficial uses of body contact water recreation or irrigation of vegetables and food crops where the vegetables or fruit may come in contact with the treated wastewater, then the wastewater should be adequately oxidized, coagulated, filtered, and disinfected. In accordance with the recommendations of the DHS, the proposed permit contains a time schedule to require a higher level of treatment for disinfection and includes both and interim and post-construction coliform and turbidity effluent limitation. The Board has considered the factors specified in Water Code Section 13263, including Is considering the provisions of Water Code Section 13241, in view of the higher level of