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Table 3 in the attached report summarize groundwater analytical data and laboratory reports are included as . Attachment 2 h The highest concentrations of hydrocarbons appear to remain onsite in the vicinity of the pump islands (MW- 1 and MW-3) When compared to the February 2000 sampling event, hydrocarbon concentrations increased very slightly in MW-5 while they decreased in MW-3, MW4, MW-9, and MW-10 Hydrocarbon concentrations remained relatively unchanged in the remaining wells Changes in hydrocarbon concentrations are most likely a result of groundwater elevation fluctuations and remediation efforts Additional monitoring data will be collected to further evaluate the dissolved hydrocarbon plume The appearance of free product in MW-1 appears to be the result of condensed soil vapor due to vapor extraction efforts Site inventory records and leak detection systems were checked to assure that a new release had not occurred, no indications of a release were identified At this time product is being removed from MW-1 by hand bailing and the use of a passive skimmer Vapor extraction efforts at MW-1 have temporarily ceased until free product can be recovered Remediation Activities—Second Quarter 2000 In August and September 1999, SECOR installed a vapor extraction/air sparging system at the subject site to remediate hydrocarbon-impacted sods and groundwater System operation began December 13, 1999 The vapor extraction system consists of ten wells (W-1 through W-8, MW-1 and MW-3) manifolded within the remediation compound Vapors are extracted with a blower and destroyed with a catalytic oxidizer with a destruction efficiency of at least 95% The air sparging system consists of 4 wells (AS-1 through AS-1) An air compressor is used to introduce air into the sparging wells, and vapors are be recovered and destroyed with the SVE system Based on the analysis of influent samples, SECOR estimates that 8,696 5 pounds of gasoline were removed and treated during the reporting period at an average extraction rate of 140 scfm SECOR estimates that 23,626 3 pounds (3,873 2 gallons) of hydrocarbons have been removed since system startup Attachment 3 in SECOR's report includes soil vapor analytical results and system efficiency results If you have any questions regarding these matters, please do not hesitate to contact me at(206) 286-4495 - Sincerely, Time Oil Co COLA(1,�A- Anastasia E Duarte-Wilkinson Environmental Toxicologist cc Ms Elizabeth Thayer California Regional Water Quality Control Board letters/calrY40491404SW8 d0c i