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4.0 CONCLUSIONS <br /> The groundwater samples collected from monitoring well MW-1 contained <br /> 0 64 parts per billion (ppb) benzene, 97 ppb methyl-tertiary-butyl ether <br /> (MTBE) and 81 ppb tert-butonal (TBA) The groundwater samples <br /> collected from monitoring well MW-2 contained 3,600 ppb TPH-G, 120 <br /> ppb benzene, 23 ppb toluene, 92 ppb ethyl benzene, 510 ppb total <br /> xylenes, 1,200 ppb MTBE, 62 ppb tert-amyl-methyl-ether (TAME), and <br /> 360 ppb TBA The groundwater samples collected from monitoring well <br /> MW-4 contained 17 ppb MTBE The groundwater samples collected from <br /> monitoring well MW-5 contained 91 ppb TPH-G, 13 ppb MTBE, and 15 p p b <br /> TBA No other hydrocarbons were detected above laboratory reporting <br /> limits in any of the groundwater samples collected <br /> The hydrocarbon and oxygenate concentrations detected in the <br /> groundwater samples collected from monitoring well MW-2 showed a <br /> slight increase in concentrations this quarter The ozone sparging system <br /> currently in operation at the site was experiencing problems during the <br /> early portion of the last quarter It is likely that the increase in <br /> . concentrations observed in this well this quarter was related to the <br /> decreased amount of ozone reaching the wells Concentrations in the <br /> remaining wells showed either a stable or decreasing trend in <br /> concentrations <br /> 5.0 RECOMMENDATIONS <br /> ASE recommends the subject site remain on a quarterly sampling <br /> schedule The next sampling is scheduled for July 30, 2003 <br /> 6.0 REPORT LIMITATIONS <br /> The results presented in this report represent the conditions at the time <br /> of the groundwater sampling, at the specific locations where the <br /> groundwater samples were collected, and for the specific parameters <br /> analyzed by the laboratory It does not fully characterize the site for <br /> contamination resulting from sources other than the former underground <br /> storage tanks and associated plumbing at the site, or for parameters n o t <br /> analyzed by the laboratory All of the laboratory work cited in this report <br /> was prepared under the direction of independent CALrEPA certified <br /> laboratory The independent laboratory is solely responsible for the <br /> contents and conclusions of the chemical analysis data <br /> Singh's Unocal Service Station Quarterly Report — April 2003 Sampling <br /> -3- <br />