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F' <br /> . while they decreased slightly in MW-4 and MW-5 Hydrocarbon concentrations remained relatively <br /> unchanged in the remainder of the wells Changes in hydrocarbon concentrations are most likely a result of <br /> groundwater elevation fluctuations and remediation efforts Since the initiation of remediation efforts, <br /> hydrocarbon concentrations across the site have substantially decreased <br /> The appearance of free product in MW-1 appears to be the result of condensed soil vapor due to vapor <br /> extraction efforts At this time product is being removed from MW-11 by continued vapor extraction, hand <br /> bailing, and the use of a passive skimmer <br /> Remediation Activities—Second Quarter 2001 <br /> In August and September 1999, SECOR Installed a vapor extractiontair sparging system at the subject site to <br /> remediate hydrocarbon-impacted soils and groundwater System operation began December 13, 1999 <br /> The vapor extraction system consists of ten wells (W-1 through W-8, MWA and MW-3) manifolded within <br /> the remediation compound Vapors are extracted with a blower and destroyed with a catalytic oxidizer with a <br /> destruction efficiency of at least 95% The air sparging system consists of 4 wells (AS-1 through AS-1) An <br /> air compressor Is used to Introduce air Into the sparging wells, and recovered vapors are destroyed with the <br /> SVE system <br /> Based on the analysis of influent samples, SECOR estimates that 2,2514 pounds (3691 gallons) of <br /> gasoline-range hydrocarbons were removed and treated during the reporting period at an average extraction <br /> rate of 193 scfm SECOR estimates that 33,791 pounds (5,540 gallons) of hydrocarbons have been <br /> removed since system startup Approximately 49 gallons of free product have been bailed from MW-1 since <br /> its detection if February 2000 Tables A-1 and A-2 In SECOR's report include soil vapor analytical results <br /> and system efficiency results <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 /> ,AW ItA (� <br /> Anastasia E Duarte-Wilkinson <br /> Environmental Toxicologist <br /> cc Ms Elizabeth Thayer <br /> California Regional Water Quality Control Board <br /> letterslcahf/404914049148 doc <br /> 2 <br />