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I <br /> lz@ " 2AAN@ <br /> • <br /> 6.2 Conclusions <br /> 6.2.1 Soil <br /> The results of the onsite shallow soil sampling and review of historic aerial photographs indicate <br /> that there do not appear to be groundwater contamination source areas at the 541 Site The low <br /> concentrations of TPH-diesel and motor oil in some soil samples appear to be the result of <br /> groundwater contamination in the capillary fringe <br /> 1 6.2.2 Groundwater <br /> ' The groundwater plume generally extends from West Grant Line Road north to at least Cardoza <br /> Lane, approximately 600 feet, and west beneath the 541 Site The full extent of the plume is <br /> unknown The highest concentrations of TPH, MTBE, and BTEX compounds were consistently <br /> found west and southwest of the 541 Site This distribution indicates an offsite source of <br /> lie contamination <br /> The northward groundwater flow direction and the shape of the groundwater plume suggest a <br /> Chevron pipeline release in the general vicinity of TR-17 and TR-18 According to Chevron, the <br /> ' 6-inch steel pipeline has carried various refined fuel products including jet fuel, gasoline, and <br /> diesel since it was installed in 1965, however jet fuel has not been run though the pipeline for <br /> several years (Pratt and Myers, 2003) The Chevron pipeline is the only known source of jet fuel <br /> in the vicinity of the 541 Site <br /> 1 <br /> In addition, the former Chevron, Mobil, and Scotties Service Stations have documented <br /> ' groundwater contamination with gasoline, diesel, motor oil (or oil and grease), MTBE, and <br /> BTEX The lateral and vertical extent of the commingled plumes from these former service <br /> stations has not been fully defined The service stations have likely contributed to the plume in <br /> the vicinity of the 541 Site due to the general northward groundwater flow direction <br /> 1 <br /> Fzeld lnvesttganon Report1 S December 2003 <br /> ' TREADWLLL&ROLLO,INC <br />