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1 <br /> 1 <br /> • <br /> 1 <br /> GEOTHASE <br /> ENVIRONMENTAL <br /> 1 REPORT <br />' Remedial Action Pilot Study <br /> 1 Former Manna Pro Site <br /> 4004 S. El Dorado <br /> Stockton, California <br /> 1 July 31,2000 <br /> Project No 207 3 <br /> 1 Geo-Phase Environmental Inc conducted a pilot level vapor extraction and air sparge test <br /> to evaluate the feasibility of using this in-situ remedial technology to mitigate soil and <br /> 1� groundwater contamination at the subject site Results of the pilot test in conjunction <br /> with prior work have shown that contaminant hydrocarbons can be removed by vacuum <br /> vapor extraction The effectiveness of a vapor extraction system (VES) as a stand-alone <br /> 1 method is partially dependent on the elevation of the groundwater surface At appears <br /> that infection of air into the saturated zone (air sparging) will tend increase the <br /> effectiveness of the vapor extraction Field observations suggest that air sparging may <br /> 1 have increased the levels of dissolved oxygen in observation wells near the air sparge <br /> well The field data also suggest that air sparging increased the vapor concentration into <br /> the air stream of the vapor extraction well, however, analytical data seemed to be <br /> 1 equivocal In total, the available data suggests that vapor extraction in conjunction with <br /> air sparging is a viable remedial method <br /> 1 1.0 INTRODUCTION <br /> Field work and groundwater monitoring completed at the site since 1990 show that <br /> 1 former leaking underground storage tanks impacted the soil and groundwater with <br /> gasoline range petroleum hydrocarbons It has been estimated by Groundwater <br /> Technologies Inc (GTI) that over 30,000 pounds (13,600 kg) of gasoline are present in <br /> 1 the subsurface This is equivalent of about 9,000 gallons of gasoline Over the past <br /> several years, groundwater monitoring data have been collected from 14 monitoring, <br /> extraction, and observation wells situated through and around the contaminant plume <br /> The available data suggests that the contaminant plume is stable and has not migrated off <br /> of the Property except in a small area to the west under El Dorado Street The continued <br /> 2937 Veneman Ave,##8240 Geo-Phase Environmental Inc Phone (209)569-0293 <br /> Modesto, CA 95356 Fax (209) 569-0295 <br /> 1 <br />