COMPLIANCE INFO_1990-1998 - Laserfiche WebLink

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u INFO ION SHEET CITY OF TRACY WASTEWATER TREATMENT PLANT SAN JOAQUIN COUNTY The City of Tracy discharges up to 9.0 mgd of treated domestic and industrial wastewater into Old River through a submerged outfall diffuser. The Old River discharge location is about three miles north of Tracy's wastewater treatment plant TP). The City of Tracy's WWTP performs the following treatment operations prior to discharging to Old River: primary clarifiction, activated biotower filtration, aeration,final clarification, chlorination and dechlorination. Sludge is processed through floatation thickening, anaerobic digestion and then dried in sludge drying beds. Recreation in the area near the wastewater outfall consists of boating, fishing and water contact sports of water skiing and swimming. Effluent and Receiving Water Limitations The discharge point is upstream of two major water intake facilities, the Bureau of Reclamation Delta-Mendota Canal and Department of Water Resources Clifton Court Forebay. The major portion of Tracy's diluted discharge is diverted through the Delta-Mendota Canal, which is a domestic water supply source for Tracy. The rest of the discharge is received into the Clifton Court Forebay, which is a domestic water source for much of the State's population. The effluent limits in the permit were developed to protect the use of the surface water as a drinking water supply. The "Water Quality Objectives" for the San Joaquin River Basin,contained in the Basin Plan, were reviewed. Compliance with effluent limits and requirements established in this permit will meet those objectives. Effluent limits are based in part on estimates of dilution in Old River, as described in the following paragraph. The permit establishes monthly average effluent limits for both BODS and suspended solids at 20 mg/l each. These limits are set to protect against potential adverse impacts from the discharge on the dissolved oxygen in Old River. Seasonal low river flows during July,August, and September, when accompanied by high effluent flows,could impact dissolved oxygen in Old River. Old River flows at Tracy are subject to influences of the San Joaquin River flows, local irrigation,municipal, and industrial water demand, pumping at Clifton Court Forebay, and tidal actions. Data on flows in Old River at the City of Tracy diffuser have been estimated using the Department of Water Resources model of the Delta. Effluent limits are partially based on these flow estimates which show a minimum receiving water to wastewater ratio of nearly a 100:1 (monthly basis). Because of difficulties in establishing permanent monitoring stations on Old River, the Discharger has not yet verified the flow regimes and available dilution in Old River used for establishing the effluent limits. This permit renewal requires the City to establish permanent monitoring stations for continuously monitoring of the Old River flow and to report minimum,maximum, and average daily flows. If minimum dilutions are significantly different from the 100:1 estimate, the permit may be reopened and modified. Modifications could include more stringent effluent limits,