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' 10 August 1999 • AGE-NC Project No 97-0333 Page 2 of 9 quantified as gasoline (TPH-g) were detected beneath the east ends of the three USTs at concentrations ranging to 2,600 milligrams per kilogram(mg/kg),beneath the west ends of the USTs at concentrations ranging to 25 mg/kg, and beneath product piping at concentrations ranging to 8,000 ' mg/kg Volatile aromatics (benzene, toluene, ethylbenzene and xylenes BTEX) were detected beneath the ' east ends of three USTs at concentrations ranging up to 340 mg/kg, beneath the west ends of the USTs at concentrations ranging up to 2 7 mg/kg, and beneath product piping at concentrations ranging up to 880 mg/kg Fuel oxygenated compounds(methyl tertiary butyl ether MTBE,Cert-amyl methyl ether TAME and tert-butanol TBA) were detected beneath the east ends of the three USTs at concentrations ranging ' up to 16 mg/kg, beneath the west ends of the USTs at concentrations ranging up to 3 1 mg/kg, and beneath product piping at concentrations ranging up to 690 mg/kg 23 PREVIOUS SUBSURFACE INVESTIGATION lie On 15 April 1999, six soil borings (P-1 through P-G) were adNaiieed aL the site to assess the lateral and vertical extent of impacted soil and ground water A total of 17 soil samples and five ground ' water samplers were collected during the investigation and vvere submitted for laboratory analysis TPH-g and total petroleum hydrocarbons quantified as diesel (TPH-d) were detected in analyzed soil samples at concentrations as high as 390 milligrams per kilogram (mg/kg), dissolved TPH-g and 1 TPH-d were detected from grab ground water samples at concentrations ranging as high as 310,000 micrograms per liter (µg/1) BTEX compounds were detected in selected soil samples and grab ground water samples at concentrations as high as 51 mg/kg and 48,000 Mcg/l, respectively MTBE, ' TAME and TBA were detected in selected soil samples and grab ground water samples at concentrations as high as 0 36 mg/kg and 310 000 pg/l Results of the April 1999 investigation were reported in the Prehminaiy Investigation and Evaluation Repoi t(PIER) dated 11 .Tune 1999 prepared by AGE Analytical results of soil samples collected during the June 1999 investigation are summarized in Table 1 24 REGIONAL GEOLOGIC SETTING ' The property is situated within the Great Valle), Geomorphic Province of California a } rP large, elongate, northwest trending, asymmetric structural trough The Great Valley Province has been ' filled with thick sequences of sediment ranging in age: from Jurassic to Recent creating a nearly flat- 1)ing a]lurial plain, extending from the Tehachapi Mountains in the south to the Klamath Mountains ' in the north The ,�estern and eastern boundaries of this prop trice are comprised of the California 4dtianeedGeoEn%iron mental, Inn