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<br /> Extended Site Characterization Report: 7500 West Eleventh Street, Tracy, CA. Page 30
<br /> xylene isomers at 370 gg/L, 11 gg/L, and 3.6 gg/L, respectively. There were no
<br /> '.� detectable concentrations of toluene.
<br /> Further to the north, and down-gradient from the former locations of the underground
<br /> tanks, no detectable concentrations of analytes of concern were detected in samples
<br /> recovered from Monitoring Wells ATCMW-4 and ATCME-5. Historically, MTBE, at
<br /> ` concentrations up to 31 gg/L, had been detected in samples of groundwater recovered
<br /> from Monitoring Well ATCMW-2 at this site, but none was detected in any of the
<br /> groundwater samples recovered on June 14, 2001. Although that site remains under the
<br /> i oversight of the SJCEHD, given its distance from the plume of affected groundwater
<br /> emanating from the site at 7500 West Eleventh Street, its essentially co-gradient location
<br /> to that site, and the limited area over which the groundwater has been found to be
<br /> affected by analytes of concern, it is SJC's opinion that fuel hydrocarbons released there
<br /> have not commingled with those released at the 7500 West EIeventh Street site.
<br /> 7.2.4 7474 West EIeventh Street
<br /> On June 2, 1988, two underground fuel tanks were removed from the property at 7474
<br /> :-, West Eleventh Street at the locations shown on Figure 12. That site, previously owned by
<br /> C&B Equipment, is now the site of Troy's Body and Paint. Following removal of the
<br /> .:' tanks, concentrations of gasoline at 2,880 mg/Kg, with benzene, toluene, ethyl benzene
<br /> and total xylene isomers at 9.73 mg/Kg, 6.41 mg/Kg, 42.4 mg/Kg and 79.5 mg/Kg,
<br /> respectively, were found in soil at a depth of 5.5 to 6 ft BGS near the former location of
<br /> the tanks. A trace of MTBE, at a concentration of 5.2 gg/L, was detected in groundwater
<br /> recovered from a groundwater-quality monitoring well (Well TGIMW-1 - see Figure 12
<br /> installed a short distance down gradient from the former location of the tanks, but was not
<br /> subsequently detected in groundwater samples recovered from that well or any of the
<br /> others installed at the site.
<br /> Results of a round of groundwater-quality sampling and analysis performed on March,
<br /> - 18, 1998 indicated the presence of 909.0 gg/L of TPH(g), with benzene, toluene, ethyl
<br /> ___ benzene and total xylene isomers at 3.0 gg/L, 3.0 gg/L, 12.0 gg/L and 39.0 gg/L,
<br /> -:. respectively, in groundwater recovered from Well TGIMW-101 located close to the
<br /> former tank pits, but there were no detectable analytes of concern in samples recovered
<br /> from Well TGIMW-4, the most westerly well on that site and the closest to the property
<br /> at 7500 West Eleventh Street. Nor were there any detectable analytes of concern in the
<br /> sample from Well TGIMW-5, the well installed at the greatest distance down the
<br /> hydrogeologic gradient from the former tank pits on the 7474 West Eleventh Street
<br /> property.
<br /> F. The SJCEHD and the RWQCB closed the case file for 7474 West Eleventh Street site on
<br /> November 21, 2000. The area of the subsurface affected by the release of gasoline at the
<br /> 7474 West EIeventh Street site is hydrogeologically co-gradient to the locations on the
<br /> 7500 West Eleventh Street property where fuel hydrocarbons were released and, as
<br /> indicated by the data presented above, is of limited lateral extent. In SJC's opinion, fuel
<br /> lost to the subsurface at 7474 West Eleventh Street has not commingled with the plume
<br /> sic
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