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Ile Site Background Information Continental Grain Company Page 2 of 2 1 Less consistently, ground water samples have been reported to show detections of total petroleum ' hydrocarbons quantified as gasoline (TPH-g) Infrequent detections of one or more of the aromatic hydrocarbon compounds (benzene, toluene, ethylbenzene, and xylenes, collectively referred to as BTEX)also have been reported in these wells (Table 2) TPH-d and TPH-g have been detected in ground water samples collected from wells MW-2 through MW-4 at concentrations that exceed water quality objectives(WQOs)established by the Central Valley Regional Water Quality Control Board (CVRWQCB) The WQOs for TPH-d and TPH-g are 100 micrograms per titer (µg/1) and ' 5 µg/1,respectively,and are based on taste and odor thresholds for drinking water Methyl tertiary- butyl ether(MTBE)has not been reported as detected in any soil or ground water samples collected from the site With the exception of the June 2004 ground water sampling event,where reported laboratory results are considered anomalous and not representative of historic conditions, and the initial sampling of well MW-1,ground water samples collected from perimeter monitoring wells MW-1 and MW-6 are not reported by the laboratory to have contained detectable concentrations ofpetroleum hydrocarbon 1 constituents Monitoring well MW-5 was reported as having low TPH concentrations in June and November/December 2004 Comparison of the historic ground water sampling events to those from June 2004 demonstrate the anomalous nature of the June 2004 results ' A free product sample was collected from MW-2 in August 2004 The laboratory characterized the sample as a substantially degraded middle distillate such as diesel#2 or heating oil that lacked the ' common water soluble, aromatic components such as BTEX, and is thus considered relatively soluble in water Based on the chemistry of the petroleum sample collected at the site, the detected TPH-d in the ground water samples from shallow wells MW-2 through MW-4,which are screened within the zone of apparent petroleum hydrocarbon affected soil, is likely due to small globules of petroleum collected within the water sample and/or petroleum entrained on soil and not dissolved phase petroleum hydrocarbons 1 r i • ' Advanced GeoEnvironmentai,Ine.