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2-10-1999 12:34PM FROM HORIZON ENVIRONMENTL 916 939 2172 P. 7 <br /> f - <br /> S U <br /> California Regional Water Quality Control Board <br /> Central 'valley Region <br /> �imtnn H.Hick,, Steven T.$utkr,Acting Clair - <br /> G.4orvnrxral s7icraamntu main Orae Cmmn. <br /> P.orrrrion lnamu AWftu: hnp7/.-r- lwbm, off-�q <br /> rb5 <br /> d <br /> 3c43 Rwrkr awQ Su;:e A,$$R.,,F�w,Gtitprya 95527-3003 <br /> Phare(916)255.30N•FAX(916)255-3015 <br /> pft <br /> TO: Gordon L. Boggs FROM: Mark R.List I <br /> UST Program Manager Engineering Geologist <br /> DATE: 27 January 1999 S1C.NATUR1:: <br /> SUBJECT; FILE REVIEW FOR CLOSURE CONCURRENCE DETERMINATION,ANTIOCH <br /> TOYOTA,DISCOVERY CHEVROLET SITE, 1615 WEST 11TH STREET TRACY, <br /> SAN.IOAQUIN COUNTY <br /> At the request of the San Joaquin County Environmental Health D.vision(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 /> ca5cfilc,and during discussions with Mr.Jeff Wong of San Joaquin County. <br /> Background: <br /> On 2 April 1993,three underground storage tanks(USTs)were reraoved 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 mon.,toring 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 l I 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 GeoProbeO <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 Brits. <br /> Between 10 and 17 August 1998,corrective action and soil removed 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 prxess,MWA 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 o a-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 Landf ill on 20 August 1998.Additionally, <br /> on 13 August 1998,the on-site domestic well was destroyed by pressure grouting. <br /> California Enr&9nmelttal Protectiotr Agency <br /> R RrevaLe P<nrr <br /> - i <br />