SITE INFORMATION AND CORRESPONDENCE_1998-2000

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f 0 M. 0� LFR P-2 (during no flow conditions of the system) and subsequently break off when the GWETS was restarted at 6 a.m. on February 9. The water released within the well vault flowed back into the well through the well vent hole. Based on LFR's field observations, it is estimated that the volume of water released outside of the well vault was probably no more than about 400 gallons. Analytical results of a groundwater sample collected from well GEW-16 in December 1998 indicated that the groundwater in well GEW-16 contained 86 micrograms per liter of tetrachloroethylene (PCE) and 93 micrograms per liter of total volatile organic compounds (VOCs). Based on this data, the total mass of PCE estimated to have been released would be no more than approximately 0.003 pounds. The water that drained into the gutter was observed to travel in the gutter in a southerly direction along Pacific Avenue. LFR site maps indicate that the closest storm drain grate is located at the northeast comer of Benjamin Holt Drive and Gettysburg Place (approximately 1,500 feet from the release point). It is not known whether any water reached the storm drain. LFR believes that it is unlikely that such a relatively small volume of water could have reached this storm drain, and that it is more likely that the water would have evaporated before reaching this storm drain. It is LFR's opinion that any PCE or other VOCs would likely have volatized either as a result of being sprayed from the holding pin hole or during its travel along the gutter, and ultimately, as a result of the likely evaporation of the water itself. LFR believes that such released water did not constitute a threat to human health or the environment. In response to the 8:00 a.m. system shut down, LFR's technician arrived at the Site at approximately 10:30 a.m. on February 10. The technician observed and replaced the failed check valve. Following installation of a new check valve, the GWETS was restarted at 11:50 a.m. on February 10 for the purposes of assessing valve performance. At approximately 12:30 p.m. on February 11, the GWETS was again shut down by LFR to assess the valve failure. LFR notified the Regional Water Quality Control Board, Department of Toxic Substances Control (DTSC), San Joaquin County (SJC) Department of Public Works, SIC Public Health Services Environmental Health Division, and Lincoln Properties Ltd., of the upset on February 11. The DTSC was contacted via voice mail on February 11 and 12, and again on February 16 in an effort to report the discharge in person. To help prevent check valve failures at other wells, LFR initiated replacement of all of the check valves at the other wells (GEW-1 though GEW-15 and GEW-17) with a ball valve. On February 11, between 4:00 and 5:00 p.m., the GWETS was shut down to replace two check valves. Following replacement of the valves the system was restarted. On February 12, between at 8:30 a.m. and 5:30 p.m., the GWETS was again shut down again for replacement of the remaining 14 check valves. Following completion of the valve replacement, the GWETS was restarted. Ur-GEW I6Upset-RWQCB-Feb99-06752:SRL 2