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lY <br /> • 4.0 CONCLUSIONS <br /> The groundwater samples collected from monitoring well MW-1 contained <br /> 200 parts per billion (ppb) TPH-G, 3 ppb benzene, 1 2 ppb ethyl benzene, <br /> 16 ppb methyl-tertiary-butyl ether (MTBE) and 8 ppb tert-butonal (TBA) <br /> The groundwater samples collected from monitoring well MW-2 contained <br /> 1,200 ppb TPH-G, 44 ppb benzene, 16 ppb toluene, 56 ppb ethyl benzene, <br /> 100 ppb total xylenes, 1,200 ppb MTBE, 4 5 ppb tert-amyl-methyl-ether <br /> (TAME), and 270 ppb TBA The groundwater samples collected from <br /> monitoring well MW-4 contained 72 ppb TPH-G, 20 ppb benzene, 31 p p b <br /> MTBE, 17 ppb TAME, and 13 ppb TBA The groundwater samples collected <br /> from monitoring well MW-5 contained 99 ppb TPH-G, 19 ppb MTBE, and <br /> 30 ppb TBA No other hydrocarbons were detected above laboratory <br /> reporting limits in any of the groundwater samples collected <br /> The hydrocarbon and oxygenate concentrations detected in t h e <br /> groundwater samples collected from monitoring wells MW-1, MW-2, <br /> MW-4, and MW-5 have shown a slight increase in concentrations this <br /> quarter The ozone sparging system currently in operation at the site was <br /> experiencing problems during the last quarter Ozone from the unit w a s <br /> not making it to the well heads due to cracked and/or broken lines The <br /> lines have since been fixed and the ozone flow has been restored It is <br /> likely that the increase in concentrations observed this quarter was in fact <br /> due to the decreased amount of ozone reaching the wells All the <br /> compounds analyzed in monitoring wells MW-3 and MW-6 continue to be <br /> below laboratory detection limits <br /> 5.0 RECOMMENDATIONS <br /> ASE recommends the subject site remain on a quarterly sampling schedule <br /> The next sampling is scheduled for April 2003 <br /> i <br /> Singh's Unocal Service Station Quarterly Report — January 2003 Sampling <br /> -3- <br />