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r•. • 09'June 2003 <br /> AGE-NC Project No. 98-0440 <br /> Page ; <br /> detected in the samples collected from monitoring wells MW2 and MW6 at concent ations of 64µg/1 <br /> 1' <br /> and-150 µg/1, respectively. <br /> Benzene was 'd'etected in the water.samples collected from wells MW2, MWS and MWS at <br /> concentrations of 1.7 µg/1, 10 µg/1 and 1.5 µg/l, respectively. Toluene was detected in the samples <br /> from wells MW2, MW5, MW6 and MW8 at.concentrations as-high as 2.0 µg/1 while ethylbenzene , <br />' and xylenes were detected as high as 15 ug/1 in these same wells. No,other analytes were:detected <br /> at,or above laboratory reporting limits in the water sampies'collected from the monitoring wells.A <br /> map showing the approximate extent of dissolved benzene is presented in Figure 5. <br />_ Current and previous'analytical results are summarized on Table 2.The laboratory rep ort,(MAI Lab <br /> ID No.0303426-001 through 03034267009),QA/QC report and chain-of-custody form are included <br />' .. in-Appendix F. <br /> I' 4.0. SUMMARY AND CONCLUSIONS <br />' Based ori the data collected during'this monitoring period,.AGE concludes: <br /> r. Ground water elevations at the site in March 2003 ranged from 25.43 feet above mean sea <br /> level (MSL) in well MW8 to '26.43 feet above MSL in well MW i.,The ground water <br />' elevations at the site decreased an average of 0.91 feet between the December ecember 2002 and <br /> March 2003 sampling events.The ground water at the site was inferred to be flowing toward <br /> the north under an average gradient of 0.007 feet/feet-which is consistent with the flow . <br /> direction,determined during previous monitoring events. <br />' + The highest concentration of dissolved hydrocarbons quantified as.TPH-g, TPH-d and BTEX . <br /> compounds extends•northeast from`.USTs No.''.4 and 5. Dissolved hydrocarbons were <br /> encountered .'in the dawn-gradient 'direction .from• the f6rrner USTs ,in samples' from <br /> monitoring wells.MW2, ,MW5, MW6 and•MW8.-Dissolved'hydrocarbon concentrations- <br /> remained non detectable in samples from wells MW1,MW3 MW4 and MW9 and D W5157 <br /> A map showing the-approximate extent of dissolved benzene is presented in Figure 5. <br /> . '�-The concentrations-of benzene detected in the water-samples collected from wells MW2,. <br /> MW5 and MW8 were above the State of California maximum contaminant level (MCL) of <br /> 1.0 µg/l for benzene iri drinking water."; <br /> The'.lateral extent ,of petroleum hydrocarbon-impacted ground water has not been fully <br /> defined toward the northeast beyond MWS. However, concentrations of dissolved TPH-g <br /> and benzene in well MW8 are very low.The conceritration of benzene is just 0.5 �Lig/l above ' <br /> the State MCL. The hydrocarbon plume is-fairly well,defined to the south,.east, west and <br /> • northwest. ; <br /> Advanced GeoEnvironinentai,Inc. <br />