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submitted from MW-1 due to the presence of free product Table 2 in the attached report summarizes groundwater analytical data and laboratory reports are included as Attachment 2 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 November 1999 sampling event, hydrocarbon concentrations increased in MWA while they decreased in MW-2 Hydrocarbon concentrations remained relatively unchanged in each of the wells Changes in hydrocarbon concentrations are most likely a result of groundwater elevation fluctuations and remediation efforts Additional monitoring data will be collected to i 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 Additionally, the clear color of the product in the well differs significantly from the color or the product dispensed from the pumps, further suggesting that a release had not occurred At this time product is being removed from MW-1 by continued vapor extraction, hand bailing, and the use of a passive skimmer Remediation Activities—First Quarter 2000 In August and September 1999, SECOR installed a vapor extractionlair sparging system at the subject site to remediate hydrocarbon-impacted soils 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) manifoided 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 System operation and performance will be discussed in the next quarterly groundwater monitoring report Based on the analysis of influent samples, SECOR estimates that 11,421 pounds of gasoline were removed and treated during the reporting period at an average extraction rate of 224 scfm 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 Anastasia E Duarte-Wilkinson Environmental Toxicologist cc Ms Elizabeth Thayer California Regional Water Quality Control Board . letterslcaI414049l4049147 doe