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