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REVISED CLEANUP AND ABATEMENT ORDER NO. 5-01-703 • -2- CITY 2-CITY OF RIVERBANK WASTEWATER TREATMENT PLANT STANISLAUS COUNTY RBAAP proposed to cease all treatment of groundwater and to discharge untreated groundwater to the facility. Staff determined that the proposed discharge modification would violate the RBAAP Record of Decision and pose a threat to groundwater quality at the facility. RBAAP was notified of this determination. 7. Influent flow to the facility is typically highest in the summer due to the cannery discharge. Order No. 94-100 prescribes an average daily dry weather flow of 7.9 mgd. In 1999, the peak daily flow was 5.9 mgd and the average daily flow was 2.1 mgd. In 2000, the peak daily flow was 5.7 mgd and the average daily flow was 2.3 mgd. 8. In 1996, the Discharger applied for a State Revolving Fund loan to finance facility improvements to prevent odor problems during the tomato processing season, rehabilitate the Winter Aeration Cell to allow emptying and cleaning of the Summer Aeration Cell, and prevent overflows at the headworks. The project included replacing the plant's motor control center, which was inadequate to provide reliable power for the aerators. Several aging aerators were to be replaced, and additional aerators were to be added to restore treatment capacity to the Winter Aeration Pond. The project also included reconstruction of the plant headworks to eliminate the hydraulic bottleneck caused by the current solids screening system. The State Water Resources Control Board approved the Discharger's Facilities Plan on 29 March 2000. 9. As a separate project with funding provided by the City of Riverbank, the Discharger undertook a storm water segregation project to provide separate storm drains for the older part of the City, which were served by a combined sewer. During heavy precipitation events, the combined sewer sometimes discharged hydraulic loads that overwhelmed the headworks. The purpose of the project was to reduce winter flows and potential headworks overflows during high-precipitation events. 10. On 10 September 1999, staff received the Discharger's verbal report of a spill of untreated waste from the plant headworks that occurred on 6 September 1999. The spill was caused by an electrical overload that stopped the screening mechanism within the headworks. Approximately 10,000 gallons of raw sewage (primarily tomato processing waste) was discharged to a contained land area below the headworks. The discharger cleaned out and disinfected the spill area as soon as practical after power was restored to the headworks. The Discharger also installed an auto dialer alarm system to inform the treatment plant operator of headworks power failure. A Notice of Violation (NOV) was issued for the spill on 15 November 1999. 11. On 25 January 2000, the Discharger reported that the headworks overflowed during a high- precipitation event due to sewer flows in excess of the headworks hydraulic capacity. Approximately 40,000 gallons of raw sewage diluted with storm water runoff was discharged to the contained land area below the headworks. Once equipment access was possible, the Discharger pumped the effluent back to the headworks and disinfected the spill area. Staff understands that most of the waste percolated into the ground. 12. An NOV was issued for this violation on 4 February 2000. The NOV required that the Discharger submit a report that specified the timeline for completion of the stone drain segregation project. The Discharger stated that the electrical improvements and some of the replacement aerators