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EXECUTIVE SUMMARY Groundwater samples were collected from seven of the eight monitoring wells on November 4, 2005 One well was dry and could not be sampled At the request of San Joaquin County Environmental Health Department, the samples were analyzed for gasoline and its volatile aromatic compounds(BTEX), diesel, gasoline oxygenates, and total lead Most samples in recent years have been analyzed only for gasoline and BTEX 1 Low molecular weight hydrocarbons that elute within the gasoline range and are reported as Total Petroleum Hydrocarbons as gasoline (TPH-g) were detected in four of six wells, but in two of the four samples the laboratory noted that the elevated result was due to a single compound within the gasoline range None of the common gasoline compounds(benzene,toluene,MTBE, etc) was detected at elevated concentrations, so a non-gasoline compound such as trichloroethane(TCE) or perchloroethane (PCE) is the most likely candidate, because both were detected at elevated concentrations on four occasions in 1995-1997 In the other two samples (VM-2 and VM-4),the chromatogram indicates that several hydrocarbons are present, but whether these represent gasoline or multiple chlorinated hydrocarbons (TCE, PCE, vinyl chloride, etc) is uncertain Over time,the concentration of these low molecular weight hydrocarbons has declined In five of the wells (VM-1, VM-2, VM-3, VM-6, and VM-7), the concentration declined by at least 35% since January 2005, and between June and November it declined by 25% in VM-1 and VM-3 and by 90% in VM-2 The only well that registered a net increase was VM-4, where the concentration • increased from 950 to 4,660 parts per billion(a net increase of slightly less than 500%) Gasoline oxygenates were not detected in any of the samples, and neither was lead However, heavier hydrocarbons that elute within the range of diesel fuel (TPH-d) were reported in VM-1 VM-2, VM-4 and VM-7 As in the case of the TPH-g result, however,the chromatograms were not typical of diesel fuel (the higher molecular weight hydrocarbons within the diesel range, which are the most stable and therefore most likely to be present, are not evident) This suggests that the TPH- d results are more likely representative of degraded gasoline or non-gasoline (solvent) compounds So far as is known, diesel fuel was not stored in the underground storage tanks at this site i he water table sloped eastward from 20 5 to 21 feet below sea level, which was fairly similar to the situation in June This implies that the groundwater flow direction continues to be east Mobilization of the propane tank to fuel the vapor extraction system was delayed through the summer months due to funding problems The situation has now been corrected, and the tank was mobilized to the site in late November The tank has been plumbed to the vapor extraction unit and -remediation is expected to begin by the middle of December 2005 The results will be reported in the next quarterly monitoring report, probably near the end of January 2006 i 1