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10 August 1999 <br /> . AGE-NC Project No 97-0333 <br /> Page 2 of 9 <br /> quantified as gasoline (TPH-g) were detected beneath the east ends of the three USTs at <br /> concentrations ranging to 2,600 milligrams per ktiogram(mg/kg),beneath the west ends of the USTs <br /> mc0ricentrat'Ons <br /> ranging to 25 mg/kg,and beneath product piping at concentrations ranging to 8,000 <br /> Y/kg <br /> Volatile aromatics(benzene,toluene, ethylbenzene and xylenes BTEX) were detected beneath the <br /> east ends of three USTs at concentrations ranging up to 340 mg/kg, beneath the west ends of the <br /> USTs at concentrations ranging up to 2 7 mg/kg, and beneath product piping at concentrations <br /> ranging up to 880 mg/kg <br /> Fuel oxygenated compounds(methyl tertiary butyl ether MTBE,tert-amyl methyl ether TANS and <br /> tert-butanol,TBA)were detected beneath the east ends of the three USTs at concentrations ranging <br /> up to 16 mg/kg, beneath the west ends of the USTs at concentrations ranging up to 3 1 mg/kg, and <br /> beneath product piping at concentrations ranging up to 690 mg/kg <br /> 23 PREVIOUS SUBSURFACE INVESTIGATION <br /> On 15 April 1999, six sail borings(P-1 through P-6) were advanced at the site to assess the lateral <br /> and vertical extent of impacted soil and ground water A total of 17 soil samples And fi-e ground <br /> water samples were collected during the investigation and were submitted for laboratory analysis <br /> TPH-g and total petroleum hydrocarbons quantified as diesel(TPH-d)were detected to analyzed soil <br /> samples at concentrations as high as 390 milligrams per kilogram (mg/kg), dissolved TPH-g and <br /> TPH-d were detected from grab ground water samples at coAxntrations ranging as high as 310,000 <br /> micrograms per liter (ug/1) BTEX compounds were detected in selected soil samples and grab <br /> ground water samples at concentrations as lugh as 51 rng/kg and 48,000 ug/l, respectively MTBE, <br /> TAME and TBA were detected in selected soil samples and grab ground water samples at <br /> concentrations as high as 0 36 mg/kg and 310,000 4g/l Results of the April 1999 investigation were <br /> reported in the Preliminary Investigation and Evaluation Report(PIER)dated I I June 1999 prepared <br /> by AGE Analytical results of soil 'Samples collected during the June 1999 investigation are <br /> summarized in Table 1 <br /> 24 REGIONAL GEOLOGIC SETTING <br /> The propert) is situated within the Great Valley Geomorphic Province of California, a targe, <br /> elongate, northwest trending, asymrnctnc structural trough The Great Vallev Province has been <br /> filled with thick sequences of sediment ranging in age from Jurassic to Recent,creating a nearly flat <br /> lying alluvial plain,extending from the Tehachapi Mountains in the south to the Klamath Mountains <br /> in the north The western and eastern boundaries of this province are cornpnsed of the California <br /> Adl6anred GfaEn,6ronmtntal,Inc <br />