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1 <br /> • wells Since the Initiation of remediation efforts, hydrocarbon concentrations across the site have <br /> substantially decreased <br /> Remediation Activities—First Quarter 2002 <br /> In August and September 1999, SECOR Installed a vapor extraction/air sparging system at the subject site to <br /> remediate hydrocarbon-Impacted soils and groundwater The vapor extraction system consists of ten wells <br /> (W-1 through W-8, MWA and MW-3) manifolded within the remediation compound Vapors are extracted <br /> with a blower and destroyed with a catalytic oxidizer with a destruction efficiency of at least 95% The air <br /> sparging system consists of 4 wells (AS-1 through AS-1) An air compressor is used to introduce air Into the <br /> sparging wells, and recovered vapors are destroyed with the SVE system System operation began <br /> December 13, 1999 <br /> Based on the analysis of influent samples, SECOR estimates that 139 pounds of gasoline-range <br /> hydrocarbons were removed and treated during the reporting period at an average extraction rate of 86 scfm <br /> SECOR estimates that 37,304 pounds of hydrocarbons have been removed since system startup <br /> Approximately 62 gallons of free product have been balled from MWA since its detection in February 2000 <br /> Tables A-1 and A-2 In SECOR's report include sod vapor analytical results and system efficiency results <br /> On January 21, 2002, a 72-hour dual-phase extraction event was Initiated on MW-1 to assist in free product <br /> removal A liquid ring vacuum pump was used to perform the test and recovered vapors were treated with a <br /> thermal oxidizer before discharge to the atmosphere The SJVAPCD was notified prior to the initiation of field <br /> activities <br /> Based on the measured concentration of extracted vapors, SECOR estimates that 26 16 pounds of TPH-g <br /> and 0 09 pounds of benzene were removed during the event Approximately 2,807 gallons of groundwater <br /> were also recovered from the well during the test Free product has not returned to MWA since the <br /> • completion of the dual-phase extraction event <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 /> 4Ana E Duarte-Wilkinson <br /> Environmental Toxicologist <br /> cc Ms Elizabeth Thayer <br /> California Regional Water Quality Control Board <br /> iletterslcald/4049/4049155 doc <br /> 2 <br />