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concentrations of hydrocarbons were found in the samples collected from MW-6 (73 ppb gasoline, 5 2 ppb <br /> benzene, 0 8 ppb ethylbenzene, and 5 3 ppb xylenes), MW-8 (78 ppb gasoline and 0 9 ppb benzene) and <br /> MW-9 (91 ppb gasoline and 2 0 ppb benzene) Hydrocarbons were not detected in the samples collected <br /> from MW-7 and MW-10 Low concentrations of MTBE were detected in the groundwater sample collected <br /> from MW-4 (25 8 ppb), however, it was not detected in any of the other samples Table 2 in the attached <br /> report summarizes groundwater analytical data and laboratory reports are included as Appendix B <br /> The highest concentrations of hydrocarbons appear to remain onsite in the vicinity of the pump islands (MW- <br /> 1) and sidegradient of the former tank bed (MW-5) When compared to the January 1999 sampling event, <br /> hydrocarbon concentrations decreased in MW-1 and MW-2 while they decreased in MW4 and MW-5 <br /> Hydrocarbon concentrations remained relatively unchanged in each of the wells Changes in hydrocarbon <br /> concentrations are most likely a result of groundwater elevation fluctuations Additional monitoring data will <br /> be collected to further evaluate the dissolved hydrocarbon plume <br /> Additional Site Activities <br /> SECOR has been contracted to design, install, operate, and maintain a soil vapor extraction/air sparging <br /> system at the subject site The installation of the proposed system's air sparging wells is scheduled for <br /> August 4 and 5, 1999 We hope to begin system construction during the week of August 16, 1999 <br /> If you have any questions regarding these matters, please do not hesitate to contact me at(206)286-4495 <br /> Sincerely, <br /> Time Oil Co <br /> Anastasia E Duarte-Wilkinson <br /> Environmental Toxicologist <br /> cc Ms Elizabeth Thayer <br /> California Regional Water Quality Control Board <br /> Iu19949049142 doc <br /> 2 <br />