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California Regional Water Quality Cbfitrol Board <br /> Central Valley Region <br /> Vinston H.Hickox Steven T.Butler,Acting Chair <br /> Secretary jar Gray Davis <br /> Environmental Sacramento Main Office Governor <br /> Protection InWx=AddMn: hnp://www.swreb,gi.gov/-nvgeb5 <br /> 3443 Rmrier Road,Suite A.Suua EOCatiromia 95827-3003 <br /> Phone(916)255.3000•FAX(916)255-3015 <br /> TO: Gordon L.Boggs FROM: Mark R. List <br /> UST Program Manager Engineering Geologist <br /> DATE: 27 January 1999 SIGNATURE: <br /> SUBJECT: FILE REVIEW FOR CLOSURE CONCURRENCE DETERMINATION,ANTIOCH <br /> TOYOTA, DISCOVERY CHEVROLET SITE, 1615 WEST IITH STREET, TRACY, <br /> SAN J'OAQUIN COUNTY <br /> At the request of the San Joaquin County Environmental Health Division(SJCEHD), a file review was <br /> completed to determine if Regional Board staff concur with the SJCEHD determination of no further <br /> action required at this site. This information was obtained during my review of the Regional Board <br /> casefile, and during discussions with Mr. Jeff Wong of San Joaquin County. <br /> Background: <br /> On 2 April 1993, three underground storage tanks (USTs)were removed from the site,including two <br /> 1,000-gallon gasoline tanks and one 550-gallon waste oil tank. Petroleum hydrocarbons were noted in <br /> all soil samples collected during UST removal activities. Site characterization activities began on <br /> 10 September 1994 with the installation of three groundwater monitoring wells. The analytical results <br /> from monitoring well soil samples revealed TPHg and BTEX soil contamination near MW-1 and MW-2. <br /> Groundwater contamination was also identified in samples collected from MW-1 and MW-2. <br /> Two monitoring wells(MW-4 and MW-5)and 11 hand-auger borings were installed and soil samples <br /> were collected for laboratory analyses on 3 April 1997. On 19 February 1998,a total of 10 GeoProbe® <br /> borings were installed between 14 and 25 feet below ground surface (bgs),with soil and groundwater <br /> sampling,to assess the lateral and vertical extent of contamination. A previously undocumented on-site <br /> domestic well was also discovered on 19 February 1998. The domestic well was sampled on 5 June <br /> 1998 and did not contain TPHg,BTEX or MTBE above laboratory reporting limits. <br /> Between 10 and 17 August 1998,corrective action and soil removal activities were conducted at the site. <br /> Approximately 450 cubic yards of petroleum contaminated soil were overexcavated to 12 feet bgs and <br /> confirmation soil samples collected. During the soil excavation process,MW-1 was destroyed. <br /> Following excavation activities, approximately 5,750-gallons of petroleum impacted groundwater were <br /> pumped from the pit. The contaminated groundwater was stored on-site in a baker tank,treated by <br /> carbon adsorption,sampled(results show no detectable concentrations of petroleum constituents),then <br /> discharged to the city of Tracy Sanitary Sewer after approval from the City of Tracy Utilities <br /> Department. Contaminated soil was disposed of at Forward Landfill on 20 August 1998.Additionally, <br /> On 13 August 1998,the on-site domestic well was destroyed by pressure grouting. <br /> California Environmental Protection Agency <br /> A Rervclyd Pacer <br />