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The groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPH-G), benzene, toluene, ethyl benzene, and total xylenes (collectively known as BTEX), and fuel oxygenates by EPA Method 8260. Analytical data is presented in Table Two. The certified analytical report and chain-of-custody documentation are included as Appendix B. 8 . 1 Groundwater Anal yti c-al--Results • The groundwater samples collected from monitoring well MW-1 contained 16 parts per billion (ppb) methyl-tertiary-butyl ether (MTBE). • The groundwater samples collected from monitoring well MW-2 contained 650 ppb TPH-G, 64 ppb benzene, 7.3 ppb toluene, 33 p p b ethyl benzene, 31 ppb total xylenes, 1800 ppb MTBE, 5.2 ppb tert- amyl-methyl-ether (TAME), and 140 ppb tent-butonal (TBA). • Groundwater samples collected from monitoring well MW-4 contained 61 ppb TPH-G, 1.2 ppb benzene, 62 ppb MTBE, and 2.6 ppb TAME, and 6.1 ppb TBA. • Groundwater samples collected from monitoring well MW-5 contained 160 ppb TPH-G, 15 ppb MTBE and 15 ppb TBA. • No other hydrocarbons were detected above laboratory reporting limits in any of the groundwater samples collected. 9 . 0 CONCLUSIONS Monitoring wells MW-2 and MW-4, within the direct proximity of the remediation zone have shown a one to two order of magnitude drop in hydrocarbon and oxygenate concentrations. The other wells continue to be free of the analytes tested and/or show a decreasing trend in hydrocarbon and oxygenate concentrations. All the compounds analyzed in monitoring wells MW-3 and MW-6 were below laboratory detection limits. At this initial point in time, the ozone sparging operation appears to be an effective means of remediating the petroleum hydrocarbon and oxygenate compounds in the groundwater at the site. Singh's Unocal System Installation and Operation Report — October 2002 -5-