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CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD CENTRAL VALLEY REGION REVISED CLEANUP AND ABATEMENT ORDER NO. 5-01-703 FOR CITY OF RIVERBANK WASTEWATER TREATMENT PLANT STANISLAUS COUNTY This Order is issued to the City of Riverbank based on provisions of California Water Code Section 13304 which authorize the Regional Water Quality Control Board, Central Valley Region (hereafter known as "Board")to issue a Cleanup and Abatement Order. The Board finds that, with respect to the City of Riverbank's acts, or failure to act, the following: 1• The City of Riverbank owns and operates a municipal wastewater treatment plant west of County Road J7 and adjacent to the north bank of the Stanislaus River in San Joaquin County. The facility(Assessor's Parcel Nos. 247-25004, 247-26002, 249-07022, and 249-06009) is in Section 23, T2S, R9E, MDB&M. 2. The facility is subject to Waste Discharge Requirements (WDRs) Order No. 94-100, and is pennitted to treat up to 7.9 million gallons per day(mgd) of domestic and industrial wastewater. 3. Wastewater is conveyed to the treatment plant via a sewer main that crosses the Stanislaus River. Following gross solids removal at the headworks, influent is discharged to the Summer Aeration Cell. From there, it flows to the Summer 1 Pond, which also has aerators at the eastern end. Treated effluent then flows through a series of percolation/evaporation ponds (Summer 2, Summer 3 and Winter 1, 2, 3, and 4 Ponds). There is a smaller pond known as the Winter Aeration Cell between the headworks and the Summer Aeration Cell, which is used during the winter when influent flows are lowest. 4. The treatment plant receives discharges from two major industrial dischargers: the Sun Garden- Gangi tomato cannery and the Riverbank Army Ammunition Plant(RBAAP) groundwater treatment system. The Discharger issues industrial discharge permits to these entities each year, which limit the flow rate, BOD mass loading rate, and concentrations of various other constituents, as applicable to the discharge. 5. The tomato cannery discharge is seasonal, occurring typically from July through September. The industrial discharge permit for the year 2000 did not limit the flow rate, and the flow ranged from 1.7 to 3.8 mgd. The maximum daily BOD loading was limited to 40,000 pounds per day as a daily maximum and 30,000 pounds per day as a 30-day average. The cannery discharge has frequently exceeded the BOD loading rate limits, resulting in major plant upsets that caused strong odors every year for the past several years. 6. The RBAAP groundwater treatment system was originally designed to remove nitrate, cyanide, and chromium. Prior to the year 2000, RBAAP discharged only ion exchange regeneration brine, which contributed significant salt but little flow to the Discharger's treatment plant. In 2000, with concurrence of Board staff, RBAAP ceased use of the ion exchange system, thereby reducing the salt load to the facility. Concurrently, RBAAP began discharging the treated groundwater to the Discharger's facility at a constant rate of 250,000 gpd, increasing the nitrate load. In early 2001,