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0 M141 <br /> showed the properties of an older gasoline with the lighter end compounds <br /> _ missing, while the sample collected at the south end, SG-5, was 3000 times <br /> higher and had the characteristics of a fresher gasoline. This extremely higher <br /> reading at SG-5 is in all likelihood a small area possibly caused by leakage <br /> during the tank excavation. Chromatograms of these two samples and a <br /> contoured concentration map are attached. <br /> The remainder of the samples collected had relatively small concentrations and <br /> did not truly resemble gasoline. The small levels of benzene, toluene and <br /> xylenes in these samples, along with there consistency over most of the site, <br /> could represent a breakdown of a heavier contaminant, an older gasoline, or the <br /> breakdown of naturally occurring organics in the clays. <br /> It is unlikely due to soil conditions and the depth to groundwater that any of <br /> the results reported were affected by possible groundwater contamination. <br /> (Recommendations <br /> To prove or disprove the effectiveness of this soil gas survey, additional testing <br /> should be performed at this site. A minimum of three soil boring should be <br /> placed at this location. One boring at each end of the tank excavation and an <br /> additional boring in the vicinity of SG-7 to determine the nature of this <br /> contaminant. Samples should be analyzed for TPH using both sonication and <br /> purge and trap extraction methods to assure both volatile and semi-volatile <br /> compounds are addressed. <br /> Should you have any questions regarding the results of this study, please <br /> contact us at your convenience. <br /> Sincerely, <br /> Timothy L. Theisen <br /> President <br /> Enclosure <br /> o n9=11 4 <br />