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• and MW-6 (310 ppb gasoline, 24 6 ppb benzene, 1 9 ppb toluene, 7 6 ppb ethylbenzene, 55 5 ppb xylenes) <br /> Lower concentrations of hydrocarbons were found in the samples collected from MW-8 (1 8 ppb benzene) <br /> and MW-9 (76 5 ppb hydrocarbons and 2 8 ppb benzene) Hydrocarbons were not detected in the samples <br /> collected from MW 7 and MW-10 Low concentrations of MTBE were detected in the groundwater sample <br /> collected from MW-4 (41 2 ppb), however, it was not detected in any of the other samples Table 2 in the <br /> attached 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) The groundwater plume does not appear to be migrating <br /> to any great extent When compared to the August 1998 sampling event, hydrocarbon concentrations <br /> increased somewhat in MW-2 and decreased slightly in MW-4, while they remained relatively unchanged in <br /> the remainder of the wells Changes in hydrocarbon concentrations are most likely a result of changes in <br /> groundwater elevation Additional monitoring data will be collected to further evaluate the extent of the <br /> dissolved hydrocarbon plume <br /> Additional Site-Activities <br /> SECOR has been selected to design, install, operate, and maintain a soil vapor extraction/air sparging <br /> system at the subject site Costs for the scope of work to be completed have been pre-approved by the <br /> Underground Storage Tank Cleanup Fund At this time, SECOR is preparing a system design document <br /> which will be used for system installation Upon completion, the design document will be used to solicit <br /> subcontractor bids for system installation Time intends to seek pre-approval of subcontractor costs from the <br /> Underground Storage Tank Cleanup Fund prior to system installation <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 /> • 1an9914649139 doe <br /> 2 <br />