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w <br /> r <br /> . MW-6 (247 ppb gasoline, 26 ppb benzene, 3 4 ppb toluene, 2 9 ppb ethylbenzene, and 46 1 ppb xylenes) <br /> Lower concentrations of hydrocarbons were found in the samples collected from MW-4 (225 ppb gasoline, <br /> 3 7 ppb benzene, and 0 8 ppb xylenes), MW-7 (73 ppb gasoline), MW-8 (52 ppb gasoline and 2 ppb <br /> benzene), and MW-9 (103 ppb gasoline and 2 5 ppb benzene) Hydrocarbons were not detected in the <br /> samples collected from MW-10 MTBE was detected in the sample collected from MW-4 at 10 9 ppb, <br /> however, it was not detected in any of the other samples Table 2 in the attached report summarizes <br /> 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 MW-3) When compared to the July 1997 sampling event, groundwater concentrations decreased in <br /> MW-1 and MW-5, while they remained relatively unchanged in the remainder of the wells Changes in <br /> hydrocarbon concentrations may be a result of a changes in groundwater elevation Additional monitoring <br /> data will be collected to further evaluate the extent of the dissolved hydrocarbon plume <br /> Future Site Activities <br /> A copy of SECOR's "Work Plan for Soil Vapor Extraction Pilot Test' dated June 26, 1997, was forwarded to <br /> the appropriate regulatory agencies on July 9, 1997 Approval of the workplan was received from the County <br /> on October 6, 1997 Upon submittal of the pilot study costs for pre-approval, the Cleanup Fund determined <br /> that a 2-day vapor extraction test would be more appropriate than the proposed 5-day test Pre-approval of <br /> costs for the 2-day pilot test was received from the Cleanup Fund on January 15, 1998 <br /> SECOR will schedule the vapor extraction test as soon as possible You will be notified of field activities in <br /> advance should you wish to observe them If you have any questions regarding these matters, please do not <br /> 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 /> jan98WG49133 doe <br /> 2 <br />