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01 September 1999 • AGE-NC Project No 97-0301 ' Page 2 of 10 concentrations up to 9,000 mg/kg(milligrams per kilogram) Volatile aromatic compounds berizene, toluene, ethylbenzene and xylenes(BTEX)were detected at concentrations up to 520 mg/kg, methyl tertiary butyl ether (MTBE) was detected ;n two stockpiled soil samples at concentrations up to ' 0 012 mg/kg Analytical results of soil samples collected during tank removal activities are summarized in Table 1 23 PREVIOUS SUBSURFACE INVESTIGATION ' On 03 June 1999, four soil bonngs (P-1 through P-4) were advanced at the site to assess the lateral and vertical extent of impacted soil and ground water A total of 14 soil samples and four "grab" ' ground water samples were collected during the investigation and were submitted for laboratory analysis TPH-g and TPH-d were detected to soil samples collected from probe boring P-1 at concentrations ranging as high as 330 mg/kg BTEX compounds were detected in soil samples collected from P-1 and P-4 at concentrations ranging as high as 9 5 mg/kg, fuel oxygenated compounds were not detected during the laboratory analysis of any selected soil samples lie TPH-g and TPH-d were detected in "grab" around water samples collected from P-1 P-2 and P-4 at concentrations ranging as high as 350,000 micrograms per liter (,Ug/1), BTEX compounds were ' detected in ground water samples collected from P-1 though P-4 at concentrations ranging as high as 3,300 kegll, the greatest benzene concentration was detected in P-1 at a concentration of 1,900 ,ugll Tert butanol (TBA) was detected in ground water samples collected from P-1, P-2 and P-4 at ' concentrations ranging as high as 140 µgll ds-isopropyl ether (DIPS) was detected in a sample collected from P-2 at a concentration of 12 µg/1 No other fuel oxygenated compounds were detected by laboratory analysis of ground eater samples Results of the June 1999 investigation were reported in Prehminmy Investigation and Evaluation Repo,t (PIER) dated 26 July 1999, prepared by AGE Analytical results of soil and grab ground water samples collected during the June 1999 investigation are summarized in Tables 2 and 3 The estimated extent of petroleum hydrocarbon-impacted soil is depicted in cross sectional view A -A ' ' in Figure 4, the estimated extent of dissolved TPH-g concentrations and of dissolved TPH-d concentrations are depicted in plan view in Figure Nos 5 and 6, respectively Based on Figures 4, 5 and 6,the horizontal and vertical extent of petroleum hydrocarbon-impacted soil has not been fully ' delineated toward the north, northeast and east, the horizontal and vertical extent of petroleum hydrocarbon-impacted ground water has not been fully delineated in any direction ' 24 REGIONAL GEOLOGIC SETTING ' The property is situated within the Great Valley Geomorphic Province of California, a large, ' 4dt&need GeoEmironmentaI,Inc