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2705 Country Club, Stockton <br /> Page 2 <br /> The following information indicates that a new release occurred. The closest well downgradient <br /> of the current operating UST system is VEW3. Water samples collected from VEW3 in <br /> February 2001 when depth to groundwater was 6.82 feet below ground surface (bgs) and May <br /> 2001 when depth to groundwater was 7.41 feet bgs were non detect for MTBE using EPA <br /> Method 8260. In August and November 2001 VEW3 was dry. In March 2002 groundwater from <br /> VEW3 had 30,300 ug/I of MTBE using EPA Method 8260. In May 2002 the concentration of <br /> MTBE in the groundwater sample from VEW3 was 16,350 ug/I, in September 2002 the well was <br /> dry, in December 2002 the concentration of MTBE in the groundwater from VEW3 was 54,000 <br /> ug/I. Groundwater samples from the other wells on site don't have these high concentrations of <br /> MTBE. <br /> It is unlikely that Safeway or 7-Eleven are the source of the MTBE in VEW3 at the USA <br /> Petroleum site. Concentrations of MTBE in groundwater samples from MW7, VEW 1 and MW 1 <br /> are low compared to VEW 3. These wells are all located on the USA Petroleum site and are <br /> between the Safeway and 7-Eleven sites and USA Petroleum UST's. In addition, the January <br /> 30, 2003, report of the fourth quarter 2002 monitoring for the adjacent 7-Eleven site states <br /> "Historic flow gradients have fluctuated, with flow directions ranging from the south to the east, <br /> to the northwest. The fluctuation of flow directions may be due to tidal action; thus the net <br /> gradient may be near zero." This indicates the predominant direction of groundwater flow from <br /> Safeway and 7-Eleven has not been towards the USA Petroleum site and water sample results <br /> from wells between the sites do not indicate a migrating plume. <br /> After reviewing the site information it was and still is suspected that the current UST system had <br /> an unauthorized release. Therefore, Palisades Gas and Wash, Inc. as current owner and <br /> operator of the UST system is a primary responsible party required to investigate and remediate <br /> the contamination at this site. <br /> If you have any questions contact Michael Infurna at(209)468-3454 or Margaret Lagorio at <br /> (209)468-3449. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> Margaret Lagorio, Supervising REHS <br /> LOP/Unit IV <br /> C: CVRWQCB—Jim Barton <br /> Exxon Mobil Corp—Darin Rouse <br /> 7-Eleven—Bob DeNinno <br /> Charles Patmon III <br />