SITE INFORMATION AND CORRESPONDENCE 1980-1999

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i • INFORMATION SHEET CITY OF LODI WHITE SLOUGH WATER POLLUTION CONTROL PLANT SAN JOAQUIN COUNTY The City of Lodi is regulated by Board Order No. 86-041, NPDES No. CA0079243, adopted 11 February 1986. This Order will be rescinded. The City maintains separate sanitary and industrial sewers, although some wastewater, primarily from General Mills, Inc. , is discharged to the domestic sewer. The domestic wastewater is treated at an activated sludge plant. During the previous permit period, flows into the plant exceeded the capacity of 5.8 mgd. Modifications to the secondary aeration basins increased the capacity to 6.2 mgd, and the City imposed a moratorium on new connections until further plant expansion work was completed. Construction to expand the plant capacity to 8.5 mgd is complete, and the moratorium has been rescinded. Effluent from the treatment plant is discharged to Dredger Cut at a point approximately 6,000 feet (1 . 1 miles) to the east of its confluence with White Slough and Bishop Cut. The majority of industrial wastewater is collected in a separate sewer. Untreated industrial wastewater is combined with sludge generated in the mechanical plant and is reclaimed in the summer by irrigating 650 acres of agricultural lands on property owned by the City. The City recently purchased 275 additional acres to allow expansion of the reclamation area. Unchlorinated domestic effluent is mixed with the industrial wastewater and used for reclamation when industrial flows do not meet agricultural needs, when wastewater does not meet effluent limits, or when dissolved oxygen concentrations in the receiving water drop below 5 mg/l and surface water discharges are prohibited. The EIR and Supplemental EIR for the plant expansion indicated the following significant impacts on water quality may occur: 1. Potential health hazard for full water contact recreationists in Dredger Cut. 2. Potential contamination of groundwater or Interstate 5 borrow pits with nitrogen compounds and other pollutants if agronomic rates of effluent and sludge application are exceeded on the City-owned agricultural fields. 3. Potential decrease of dissolved oxygen in White Slough and Bishop Cut due to an increase in pollutants (BOD and suspended solids) discharged. WATER QUALITY IMPACT MINIMIZATION In order to assure that the permitted discharge is consistent with antidegradation provisions of 40 CFR 131 . 12 and State Water Resources Control Board Resolution No. 68-16, the Discharger is prohibited from discharging effluent to Dredger Cut when dissolved oxygen concentrations in the receiving water are less than 5 mg/l . Effluent limitations during the summer period are more stringent than during the winter (as in previous Requirements) in order to