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Geofogica(Technics Zne: i . <br /> 2741 Rimr Road <br /> Ir Mo&sto,C-f fam=95351 <br /> (209)538-6424/jax#538-5852 <br /> REPORT <br /> Site Characterization <br /> Former Moresco Property <br /> P iK3' <br /> 16865 Gawne Road <br /> Stockton, California <br /> Project No'. 251.2 <br /> ,October 41, 1996 <br /> EXECUTIVE SUMMARY <br /> L The exploratory work at' this site has shown that gasoline was released from the former <br /> residential UST and impacted the subsurface soils down to about 70 feet. The fuel oxygenate <br /> compound Methyl Tertiary Butyl Ether (MTBE) has been found at this site and may account <br /> in part for the center of the highest contaminant mass•to be migrating away from the source <br /> and moving down towards groundwater:` Groundwater monitoring has not occurred. Mass <br /> balance calculations show that approximately 1,675 gallons of gasoline remain 'in the <br /> subsurface. <br /> Site geologic conditions are dominated by sandy sediments with a thin gravel layer at 63 feet. <br /> The presence of MTBE in the gasoline and evidence of chemical mass transfer,through the <br /> subsurface soils away from the source suggest that the gasoline contaminant may encounter <br /> groundwater and potentially impact the property's domestic well located 200 feet east of the <br /> former tank location. <br /> We recommended that chemical fate :and trans ort and risk evaluation modeling be <br /> P g <br /> performed to determine if mitigation measures should be performed and if so, what would the <br /> cleanup goals be to protect human healthy <br /> 1.0 INTRODUCTION <br /> On behalf of Mr. Michael McGranahan, trustee'in bankruptcy, Geological Technics Inc. has <br /> performed environmental assessment work at the former Moresco Property located at 16865 <br /> Gawne Road in Stockton. <br /> The subject property had a 500 gallon Icapacity underground storage tank (UST) once used` for residential automotive fuel supply. The UST was removed on November 15, 1994 and <br /> 1 significant concentrations of gasoline range petroleum hydrocarbons were detected in a soil <br /> sample collected beneath the former tank cradle at depth of 17.5 feet below ground surface <br />