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' 03 April 2002 AGE-NC Project No. 97-0333 ' Page 2 of 12 ' three USTs at concentrations ranging up to 2,600 milligrams per kilogram(mg/kg); in soil samples beneath the west ends of the USTs at concentrations ranging up to 25 mg/kg; and in soil samples beneath product piping at concentrations ranging to 8,000 mg/kg. ' Benzene, toluene, ethylbenzene and xylene (BTEX) constituents were detected in soil samples collected 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. ' Methyl tertiary butyl ether(MTBE), tert-amyl methyl ether(TAME) and tert-butanol (TBA)were detected in soil samples collected beneath the east ends of the three USTs at concentrations as high as 16 mg/kg;beneath the west ends of the USTs at concentrations as high as 3.1 mg/kg;and beneath ' product piping at concentrations ranging up to 690 mg/kg. Analytical results are summarized in Table 1. ' 2.3. PREVIOUS SUBSURFACE INVESTIGATION The following is a summary of previous investigations at the site due to the unauthorized release of petroleum to the subsurface: ' April 1999 - Six shallow soil borings(P-1 through P-6)were advanced at the site as part of preliminary investigation to assess petroleum-impact to soil and ground water (Figure 2). TPH-g and total petroleum hydrocarbons quantified as diesel(TPH-d)were detected in soil samples and grab ground water samples at concentrations as high as 390 mg/kg and 310,000 micrograms per liter(µg/1),respectively. BTEX constituents were detected in selected soil samples and water samples at concentrations as high as 51 mg/kg and 48,000 µg/1, respectively. MTBE, TAME and TBA were detected in selected soil samples and grab groundwater samples at concentrations as high as 0.36 mg/kg and 310,000µg/1,respectively. Analytical results are summarized in Tables 2 and 3.Results of the April 1999 investigation were reported in Preliminary Investigation and Evaluation Report (PIER) dated 11 June 1999 prepared by AGE. ' • June 2000-Ground water monitoring wells MW-1,MW-2,MW-3,MW-4 and MW-5 were installed on- and off-site to depths of approximately 32 feet bsg to assess the extent of petroleum-impacted soil and ground water. TPH-g was detected in soil samples collected from borings MW-1, MW-2 and MW-4 at concentrations as high as 85 mg/kg; BTEX constituents were detected in soil samples collected from MW-1, MW-2 and MW-4 at ' concentrations as high as 6.7 mg/kg; MTBE and TAME were detected in soil samples collected from MW-1, MW-2 and MW-3 at concentrations as high as 110 mg/kg. Initial water samples collected from wells MW-1, MW-2, MW-3 and MW-4 detected TPH-g at ' Advanced GeoEnvironmental,Inc. 1