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1 <br /> 19 March 2001 <br /> AGE-NC Project No 98-0492 <br /> ' Page 2 of 7 <br /> UST excavation Soil samples were analyzed for total petroleum hydrocarbons quantified as gasoline <br /> (TPH-g), total petroleum hydrocarbons quantified as diesel (TPH-d), volatile aromatic compounds <br /> (benzene, toluene, ethylbenzene and total xylenes - BTE&X), five fuel oxygenates and total lead <br /> TPH-g was reported in soil samples S-7 and S-9 collected from beneath each dispenser Island at <br /> concentrations of 2 4 milligrams per kilogram (mg/kg) and 2 1 mg/kg (Figure 2) Benzene was <br /> ' detected in soil sample S-7 at a concentration of 0 0065 mg/kg Methyl tertiary butyl ether(MTBE) <br /> was detected in soil samples S-7 and S-9 at concentrations of 4 5 mg/kg and 4 3 mg/kg <br /> ' <br /> 23 PREVIOUS SUBSURFACE INVESTIGATIONS <br /> ' It is our understanding that a previous subsurface Investigation was performed in 1993 Two soil <br /> borings and three ground water monitoring wells were drilled and sampled at the site According to <br /> Ms Pontes, no hydrocarbon-impacted soil or ground water were encountered during that <br /> ' investigation However, AGE was not provided with copies of the report of previous investigation <br /> for review <br /> ' In October 1998, AGE advanced six soil borings at the site to determine if petroleum hydrocarbons <br /> had impacted the soil and ground water at the site Soil and ground water samples were analyzed for <br /> ' TPH-g, TPH-d, BTE&X compounds, and the five fuel oxygenates None of the target analytes were <br /> detected above Iaboratory reporting limits in any of the samples analyzed TPH-d was detected in <br /> the ground water samples collected from P-2 and P-5 at concentrations of 120 micrograms per liter <br /> ' (/.cg/1) and 2,000 ,ug/l, respectively (Figure 2) Methyl tertiary-butyl ether(MTBE) was detected at <br /> a concentration of 4 5 µg/l In the ground water sample collected from probe bormg P-2 No other <br /> analytes were detected above laboratory reporting limits in the ground water sample analysis Results <br /> ' of this Investigation are summarized on Table I <br /> ' 2 4 REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING <br /> The site Is located within the southern San Joaquin Valley which comprises part of the Great Valley <br /> geomorphic province of California The San Joaquin Valley is formed by the Great Valley <br /> geosyncline, which is a large, elongate, northwest-trending asymmetrical structural trough(basin) <br /> It is bordered by the Coast Ranges to the west, the Klamath Mountains and Cascade Range to the <br /> ' north, and the Sierra Nevada to the east This trough has been filled with sediments derived from <br /> both marine and continental sources Thickness of the sedimentary fill ranges from thin veneers <br /> ' along the valley edges to more than 20,000 feet in the south central portion of the valley The <br /> sedimentary formations range in age with the older deposits being primarily marine in origin and the <br /> . younger deposits being primarily continental Continental-derived sediments were primarily <br /> ' Advanced GcoEnvironmcntal,Inc <br /> 1 <br />