SITE INFORMATION AND CORRESPONDENCE_1998-2000

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OUR The technician arrived at the Site at approximately 2:45 pm. Upon arriving at the Site, the technician noted that the rain had stopped and that the bermed secondary containment area surrounding the treatment system was filled nearly to capacity (less than 0.5-inch of freeboard remaining). The two sump pumps within the bermed area, which work independently of the GWETS to drain fluids from the secondary containment area, were pumping the water out of the drainage sumps and into the surge tank. The sump pumps were re-circulating a mixture of rainwater, untreated groundwater, and treated groundwater, which was then spilling over the top of the surge tank into the surrounding bermed area. The overflowing water from the surge tank splashed into the water within the bermed area adjacent to the tank, over the top of berm, and onto the asphalt immediately adjacent to the berm. The exact volume of water that splashed outside of the berm is unknown. Based on the observations of our technician at the Site and on the duration of the system upset, that the amount of water that splashed over the berm likely is de minimis (on the order of several gallons) and likely would not have reached the storm drain. In the event that any water did reach the storm drain—and there is no evidence to suggest that it did—such water would have contained very low concentrations of chemicals as a result of volatilization and mixing with rainwater. It is LFR's opinion that such water would not constitute a threat tq human health or the environment. Once the system upset had been assessed, the technician restored and rebooted the treatment system in order to pump out the excess water from the berm and tank. This water was fully treated prior to being discharged to the storm drain. The technician obtained samples of the combined mixture of untreated groundwater, treated groundwater, and rainwater from the surge tank and the GWETS effluent. The GWETS was then shutdown pending further investigation into the cause of the upset. The results of these analyses are attached to this letter. Remedial and Follow-un Actions Taken LFR notified the Regional Water Quality Control Board (RWQCB), Lincoln Properties Ltd., and San Joaquin County (SJC) Department of Public Works of the system upset on December 2, 1998. At the request of the RWQCB (on December 3, 1998), LFR also notified the Department of Toxic Substances Control (DTSC) and SJC Public Health Services Environmental Health Division on December 3, 1998. The GWETS remained shutdown so that repairs could be made and a full systems check could be conducted. The following modifications will be made to the GWETS before the system is restarted: • Additional interlocks will be installed into the computer operating system that will shut off the well pumps in case a treatment plant alarm is activated, including the alarms for pumps P-1 and P-2. • A dual-contact run configuration will be established for each of the well pumps, requiring two independent electrical contacts to start and stop the well pumps. GWETS Upset:TA6 2