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1 <br /> CeoCogccal Technics Ptc. <br /> 1101 711,Street <br /> Modesto,California 95354 <br /> (209)522-4119/Fax(209)5224227 <br /> Work Plan Addendum - <br /> 1 <br /> BIO-VENTINGNAPOR EXTRACTION <br /> ' George's Service <br /> 1600 Durham Ferry Road <br /> Tracy, California <br /> Project No 425 3 <br /> May 10, 2002 <br /> ' 1.0 INTRODUCTION <br /> The site, located at the intersection of Highway 33 and Durham Ferry Road, has been <br /> owned and operated by George and Mei Teranishi since the 1940's as an automobile repair <br /> {� facility and market Gasoline was sold at the site until 1990, when the tanks were removed <br /> The site has been undergoing site characterization work commencing in 1995 by Del Tech <br /> ' Geotechnical Support Services Three monitoring wells were installed in early 1995 and <br /> elevated levels of petroleum hydrocarbons were detected on the northern and western slides <br /> of the property <br /> t In January of 1997 Geological Technics Inc (GTI) contracted with Mr and Mrs Teranishi <br /> to provide additional site characterization work regarding the definition of the lateral and <br /> vertical extent of petroleum hydrocarbons in the soil and groundwater In early April 1997, <br /> GTI installed five new water-table monitoring wells and one intermediate depth discretely <br /> screened monitoring well In mid 1998, GTI installed two additional intermediate depth <br /> discretely screened monitoring wells and one deep discretely screened monitoring well <br /> ' Quarterly groundwater monitoring reports have been submitted throughout the project <br /> In late July of 2001 GTI and Del Tech performed a limited soil excavation at the site and <br /> removed approximately 500 cubic yards of contaminated soil Analytical data show that <br /> ' approximately 4,900 pounds of TPH-G were removed from the site At the end of October <br /> 2001 the stockpiled soil was transported to and disposed of at Forward Landfill GTI <br /> submitted a report on the soil excavation activities on January 28, 2002 <br /> ' During the backfill of the excavation, the County inspector reviewed the work in progress <br /> and discussed the issue of the residual contamination left under the building, around the <br /> ' monitoring wells and under Durham Ferry Road It was concluded that piping should be <br /> installed for use in a bio-venting project that could extract at a slow rate the vapors emitted <br /> from the residual contamination Subsequently, two pipes were installed to allow for the <br /> operation of a low flow bio-venting/vapor extraction system in and around the excavation <br />