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<br /> Well Installation Report 2
<br /> 7-Eleven Inc., Store#14117,2725 Country Club Boulevard Stockton,CA August 12, 1999
<br /> was also collected from beneath each of the USTs. All soil and groundwater sampling was conducted
<br /> at the direction and observation of Mr. Michael Kith of the SJCPHS. All samples were submitted to a
<br /> California state-certified laboratory for analysis under legal chain-of-custody.
<br /> ' The soil samples were analyzed for benzene, toluene, ethylbenzene, total xylenes (BTEX), methyl tert-
<br /> butyl ether (MTBE), and total petroleum hydrocarbons-as-gasoline (TPH-G) by EPA methods
<br /> 8020/8015 modified and oxygenates tent-butanol (TBA), MTBE, diisopropyl ether(DIPE), ethyl-tert-butyl
<br /> ' ether(ETBE), tert-amyl methyl ether(TAME) by EPA method 8260. Two soil samples were also
<br /> analyzed for total lead by EPA method 6010. Maximum benzene and TPH-G concentrations of 63
<br /> ' milligrams per kilogram (mg/kg) and 7,200 mg/kg, respectively were detected beneath the south end of
<br /> the central UST. The highest MTBE concentration (40 mglkg) was detected beneath the southern end
<br /> of the western UST. TAME was detected in one sample at 2 mg/kg. TBA, DIPE, ETBE, and total lead
<br /> were not detected.
<br /> The former tank pit was subsequently over excavated to a depth of 14 feet below grade, removing the
<br /> majority of the soil hydrocarbon source. About 230 (total) cubic yards of soil from the former tank pit
<br /> was removed by Belshire Environmental, a licensed waste hauler, to TPS (Richmond, California), a
<br /> licensed soil recycling facility_ About 280 cubic yards of clean soil (as verified by analytical results)
<br /> removed from the new tank pit area were used as backfill material in the former tank pit. The remaining
<br /> ' clean soil from the new tank pit (about 700 tons, or approximately 500 cubic yards) was hauled by a
<br /> licensed waste hauler to a licensed disposal facility as it was unsuitable for recompaction purposes.
<br /> One soil sample was collected on July 30, 1998, from the southwest corner of the base of the new tank
<br /> pit area. Benzene and TPN-G levels were 0.092 mg/kg and 1.5 mg/kg, respectively. MTBE, TBA, and
<br /> ' methanol concentrations were 23 mg/kg, 98 mg/kg, and 240 mg/kg, respectively.
<br /> The groundwater samples from beneath the former underground storage tanks were analyzed for
<br /> ' BTEX, MTBE, and TAH-G by EPA methods 8020/8015 modified, and the oxygenates TBA, MTBE,
<br /> DIPE, ETBE, and TAME by EPA method 8260. In addition, one sample was analyzed for total lead by
<br /> ' EPA method 6010. Maximum dissolved benzene, TPH-G, and MTBE concentrations were 5,000
<br /> micrograms per liter (lag/L), 140,000 pg/L, and 68,000 pg1L, respectively. Concentrations of TBA and
<br /> TAME ranged up to 23,000 lag/L and 1,200 lag/L, respectively. Total lead concentrations ranged up to
<br /> 0,82 milligrams per liter(mg1L). DIPE and ETBE were not detected. The highest levels of dissolved
<br /> constituents were observed beneath the western UST.
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