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r � • 08 July 1999 AGE-NC Project No. 95-0130 Page 2 of 10 and BTEX were detected in soil samples at concentrations ranging up to 2,200 mg/kg (Table 1). In 02 September 1998, two 4,000-gallon steel USTs, one 550-gallon steel UST and associated dispensers/product piping were removed from a east section of the site (see Figure 2). Upon tank removal, soil samples were collected from the floor of the excavation; soil samples were not collected beneath product piping due to hard backfill material. Total petroleum hydrocarbons quantified as gasoline (TPH-g) were detected beneath the USTs at concentrations ranging as high as 8,200 milligrams per kilogram (mg/kg). Volatile aromatics(benzene,toluene, ethylbenzene and xylenes: BTEX) were detected beneath the USTs at concentrations ranging as high as 1,400 mg/kg. Fuel oxygenates (methyl tertiary butyl ether: MTBE, tert-amyl methyl ether: TAME and tert- butanol: TBA) were detected beneath the USTs at concentrations ranging as high as 13 mg/kg. Analytical results of soil samples collected during tank removal activities are summarized in Table 1. 2.2. PREVIOUS SUBSURFACE INVESTIGATION The following is a brief summary of previous subsurface investigations at the site: • In December 1994, five soil borings (B-I through B-5) were advanced at the site near the former UST area. Soil borings B-1,B-3 and B-5 were advanced to depths of 35 feet;B-2 and B-4 were advanced to depths of 65 feet. Petroleum hydrocarbon impacted soil was encountered in all five soil borings at depths between 10 feet and 65 feet (Table 2). • In January 1995,four additional soil borings(MW-1 through MW-3 and B-6)were advanced at the site as part of the ongoing investigation. Soil boring B-6 was advanced to a depth of 65 feet; MW-1 through MW-3 were advanced to depths of 80 feet and completed as 2-inch diameter ground water monitoring wells. Petroleum hydrocarbon impacted soil was encountered in all four soil borings at depths between 35 feet and 65 feet. Dissolved TPH-g and BTEX compounds were detected in initial ground water samples from all three wells at concentrations up to 11,000 µg/1 (Tables 2 and 3). • In December 1995,three soil borings(VW-1 through VW-3)were advanced near the former UST area and one soil boring(MW-4)was advanced downgradient of the former UST area. Soil borings VW-1 through VW-3 were advanced to depths of 63 feet and completed as soil vapor extraction (SVE) wells. Soil boring MW-4 was advanced to a depth of 75 feet and completed as a 2-inch diameter ground water monitoring well. Hydrocarbon-impacted soil was encountered in all three SVE wells at depths of 15 feet to 60 feet; no petroleum Advanced GeoEnvironmcntal,Inc.