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Work Plan for Site Assessment
<br /> Former Texaco Service Station
<br /> `" Chevron Site ID 309075
<br /> September 30,2009
<br /> In May 2001, Condor Earth Technologies, Inc. (CETI) issued an environmental site assessment
<br /> report for the former Texaco site and the adjacent property located at 3331 East Clark Road.
<br /> CETI concluded that due to the historical use of the site as a service station and that no records
<br /> could be located concerning the removal of the USTs, the USTs, therefore, were most likely
<br /> abandoned in place (AGE Quarterly Mbnitoring Report, 2007).
<br /> In March 2002, AGE conducted a subsurface investigation of the site which included the
<br /> installation of four soil borings (P1, P2, P3 and P4). A report documenting the subsurface
<br /> investigation cannot be located, however, an historical analytical soil sample table, containing
<br /> analytical results for the soil samples from P1, P2, P3 and P4, has been located. The soil
<br /> samples collected from borings P1, P2 and P4 did not contain concentrations of petroleum
<br /> hydrocarbon constituents above their respective method detection limits (MDL). Concentrations
<br /> of total petroleum hydrocarbons as gasoline (TPH=GRO), toluene, ethylbenzene and total
<br /> xylenes were detected in the soil samples collected from P3, at depths of 15, 25 and 40 feet
<br /> below ground surface (bgs). Concentrations of methyl tertiary butyl ether(MTBE)were detected
<br /> in the soil samples collected from P3 at depths of 15 and 25 feet bgs. The soil sample collected
<br /> from P3, at a depth of 40 feet bgs, contained the highest concentrations of TPH-GRO, toluene,
<br /> ethylbenzene and total xylenes; 6,300, 500, 250 and 1,600 milligrams per kilogram (mg/kg),
<br /> respectively. The greatest concentration of MTBE was detected in the soil sample collected
<br /> from P3 at 15 feet bgs, 10 mg/kg.
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<br /> In June 2002, the San Joaquin County Environmental Health Department(SJCEHD)filed a UST
<br /> Unauthorized Release (Leak)/Contamination Site Report for the site. An unknown quantity of
<br /> gasoline spillage was reported. At this time the SJCEHD placed the site in the Local Oversight
<br /> Program and required that a work plan be submitted, one which would investigate the lateral
<br /> and vertical extent of contamination at the site (AGE Quarterly Monitoring Report, 2007).
<br /> In November 2005, AGE conducted a limited subsurface investigation which included advancing
<br /> two soil borings (131 and 132) to collect soil and groundwater water samples. Only the soil
<br /> samples collected from 61 at 50 and 60 feet bgs contained concentrations of petroleum
<br /> hydrocarbon constituents above their respective MDLs. The soil sample collected from B1 at 50
<br /> feet bgs contained toluene, ethylbenzene and total xylenes at concentrations of 0.020, 0.014
<br /> and 0.070 mg/kg, respectively. The soil sample collected from 61 at 60 feet bgs contained
<br /> toluene, ethylbenzene and total xylenes at concentrations of 0.026, 0.040 and 0.220 mg/kg,
<br /> respectively. The only petroleum hydrocarbon detected in the groundwater samples collected
<br /> from 131 and B2 was 1,2-dicholoethane (1,2-DCA), at concentrations of 100 and 20 micrograms
<br /> per liter(Ng/L), respectively.
<br /> In August 2006, one groundwater monitoring well (MW-1) was installed at the site. The
<br /> groundwater sample collected from MW-1 contained TPH-GRO, toluene, ethylbenzene and total
<br /> �. xylenes concentrations of 2,900, 240, 79 and 390 pg/L, respectively(AGE, 2006). MwyNstall•�e�✓t
<br /> 11(13'ob
<br /> In June 2008, ARCADIS supervised Spectrum Geophysics (Spectrum) during a geophysical
<br /> two survey to evaluate probable locations of closed (abandoned in-place) USTs and other remaining
<br /> subsurface facilities. Upon review of all electromagnetic (EM-61) and ground penetrating radar
<br /> (GPR) profiles, no definitive UST signatures were observed (ARCADIS 2008).
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