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i <br /> I1 3 &ite-HistoEy <br /> The facility at the site has been operating as a gasoline station since 1969 In September 1991, the <br /> underground storage tanks (USTs) and associated piping were removed from the site as part of a <br /> facility upgrade Laboratory analytical results of soil samples collected during the tank removal <br /> activities reported detectable concentrations of total petroleum hydrocarbons as gasoline (TPHg), <br /> benzene, toluene, ethylbenzene, and xylenes (BTEX), and ethylene dibromide (EDB) Based on <br /> these results, an assessment was conducted at the site in August 1992 which included a soil gas <br /> survey, drilling and soil sampling of seven soil borings, and converting four of the borings into <br /> groundwater monitor/extraction wells and three of the borings into soil vapor extraction wells A <br /> soil vapor extraction pilot test was subsequently performed on the vapor extraction wells A copy <br /> of the tank pull report prepared by Canonie Environmental (Canonie) was forwarded to the office <br /> of San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) on <br /> December 17, 1991 A copy of the site assessment report prepared by Canome was forwarded on <br /> May 26, 1993 Based on the PHS/EHD's June 24, 1993 reply, an additional investigation was <br /> Mimplemented by SEACOR in December 1993 Site activities included the advancement of four <br /> verification borings to define the limit of hydrocarbon impacted soils and re-sampling the <br /> groundwater monitor wells A Problem Assessment Report was prepared by SEACOR on May 31, <br /> 1994 <br /> I <br /> 2.0 SITE CHARACTERISTICS <br /> I <br /> 21 HydrQgeoloa <br /> The site is underlain by a yellowish-brown to light olive gray, fine to medium grained sand, to a <br /> depth of approximately 15 feet below ground surface (bgs) The sand overlies a very stiff, dark <br /> yellowish-brown clay which averages 5 feet in thickness A medium brown, fine to medium grained <br /> sand was encountered from approximately 20 feet bgs to approximately 30 feet bgs where a silty <br /> clay was observed by Canonie Groundwater is encountered in this sand under unconfined <br /> conditions <br /> I 1 OC I S74.01 4�COR` <br /> � <br /> NS�u2-0l 2 Augusl 26 199a <br />