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CENTRAL VALLEY TtEGIONAL WATER QUALITY`!'ONTROL BOARD INSPECTION REPORT 14 February 2001 DISCHARGER: Stockton Regional Wastewater Control Facility LOCATION & COUNTY: 2500 Navy Drive, Stockton, San Joaquin County CONTACT(S): Ms. Diane Hinson, Regulatory Compliance Officer Mr. Mark Von Aspren, Tertiary Plant Operations Supervisor Mr. Morris Allen Director MU/Wastewater INSPECTION DATE: 8 December 2000 10:00— 1230 hrs INSPECTED BY: Robert Fagemess ACCOMPANIED BY: Ms. Hinson, Mr. Von Aspern and Mr. Allen, City of Stockton OBSERVATIONS AND COMMENTS: On 8 December 2000, I met with Mr. Allen, Mr. Von Aspem, and Ms. Hinson who accompanied me during an inspection of the Stockton Regional Wastewater Control Facility(RWCF), Tertiary Treatment Facility. The inspection was conducted to follow up the 7 December 2000 reported release of non-disinfected secondary effluent to the San Joaquin River through a faulty gate valve. At the time of the inspection,the plant was operational and discharge was occurring to the San Joaquin River as allowed by the conditions of the existing NPDES permit. The inspection involved meeting with the RWCF staff, inspection of the equipment at fault, review of the 15 December 2000 incident report prepared by RWCF staff and review of the December 2000 discharger monitoring report. Mark Von Aspern, Supervising Plant Operator of the Stockton Regional Wastewater Control Facility (RWCF) Tertiary Treatment Facility described to me how the leakage of the recirculation gate valve was discovered and what steps were taken to correct the problem. Figure 1 illustrates the various valves and other equipment discussed in this report. On 7 December 2000 at approximately 0900, a low tide lowered the elevation of the wastewater in the chlorine contact chamber(CCC) to a level that exposed the top half of the recirculation gate valve. Mr. Von Aspern noticed that water from the reverse side of the gate valve was leaking into the CCC through the top portion of the gate valve. The leaking could only have occurred when the elevation of the treated wastewater in the CCC was lower than the non-disinfected wastewater on the reverse side of the recirculation gate valve. The recirculation gate is used to allow the RWCF staff to recirculate disinfected wastewater back to the ponds prior to discharging to the San Joaquin River(SJR). This allows the RWCF staff to verify effluent limits are met prior to discharge to the SJR. The water that is located on the reverse side of the