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f Extended Site Characterization Report: 7500 West Eleventh Street, Tracy, CA. Page 29 7.2.2 7777 West Eleventh Street An underground, 350-gallon, unleaded gasoline storage tank formerly located at 7777 West Eleventh Street was removed in July 1996 (John P. Cummings and Associates 1997). That site, which today forms part of the Piedmont Lumber (Truss Division) property at 7675 West Eleventh Street, was used from 1952 through the early 1990s as an auto wrecking yard and tire service facility. The soil found beneath the tank at the time it was removed contained 4,300 mg/Kg and 540 mg/Kg of TPH(g) at depths below grade of 6.5 ft and 10 ft., respectively. The tank pit was over-excavated to a depth of approximately 10 ft. BGS and the affected soil treated on site by aeration. A total of four groundwater-quality monitoring wells were installed at the site in November 1997; results obtained from those wells revealed that soil in the approximate area depicted on -a Figure 12 was affected, to depths not exceeding 5 ft., by concentrations TPH(g) that did not exceed 51 mg/Kg, with associated very low concentrations of the BTEX compounds. The concentration of gasoline in groundwater recovered in March 1999 from the monitoring well installed furthest down gradient from the former tank location (i.e., Well JCMW-3) was 650 µg/L, with commensurately low concentrations of the BTEX __. compounds. No MTBE was detected in the sample recovered from that well at that time, but concentrations of MTBE were recorded in groundwater beneath the site at concentration up to 5.6 µg/L (John P. Cummings and Associates 1999). 1 The SJCEHD and the RWQCB closed the case file for this site on November 9, 1999. Given the small area of the subsurface that was affected by fuel hydrocarbons and the low concentrations of analytes of concern detected in soil and groundwater, its distance from the 7500 West Eleventh Street site, and its essentially co-gradient location relative to that site, it is SJC's opinion that any the release of gasoline at the 7777 West Eleventh Street property has not intermingled with or come into close proximity with the plume of affected groundwater emanating from the 7500 West Eleventh Street site. 7.2.3 7685 West Eleventh Street On October 15, 1986, two underground storage tanks were removed from another location on what is today the Piedmont Lumber (Truss Division) property at 7685 West Eleventh Street. Their former locations are shown on Figure 12, just to the east of the building at 7685 West Eleventh Street. Those tanks had been owned by the Fayette Manufacturing Corporation, which had used the site to manufacture windmills for -r agricultural pumping and other applications. A hydrocarbon fuel product was found in the tank pit when the southermnost of the two tanks was exhumed (ATC Associates Inc. 1998). Subsequently, exploratory borings were drilled at the site and six groundwater- quality monitoring wells were installed. I Results of a round of groundwater sampling and analysis performed on June 14, 200.1 -. showed that groundwater in Monitoring Well ATCMW-2, at the location from which the storage tanks had been removed (see figure 12), was affected by 7,600 µg/L of TPH(g) with benzene, toluene, ethyl benzene and total xylene isomers at 1,300 µg/L, 69 µg/L, 34 µg/L and 150 µglL, respectively. In ATCMW-3, located some 40 ft. north of the former tanks, the concentration of TPH(g) was 950 µg/L, with benzene, ethyl benzene and total sic