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r SECOR rConceptual Site Model . Chevron Service Station#9-6171 March 25, 2005 rPage 17 ranging from 35 mg/kg to 170 mg/kg Concentrations of benzene In soil samples collected r from B-8 ranged from 0 033 mg/kg to 0 68 mg/kg, toluene from 0 26 mg/kg to 5 3 mg/kg, ethyl benzene from 0 79 mg/kg to 1 9 mg/kg, and total xylenes from 1 7 mg/kg to 17 mg/kg Six soli borings (B-9 to B-14) were drilled in the area of the proposed replacement tank r basin Petroleum hydrocarbons were not detected at or above method detection limits In the nine sal samples submitted for laboratory analysis r Twelve additional soil samples were collected from the native soils beneath the excavated USTs, product piping, and from the soil stockpile The sods collected from the tank basin, designated TS, contained unspecified types of hydrocarbon volatiles Concentrations r reported as "petroleum hydrocarbons volatile", analyzed using laboratory method 5030, ranged from 1 2 mg/kg (TS-3) to 19,000 mg/kg (TS-6) Ethylene dibromide concentrations range from below the method detection limits to 830 mg/kg (TS-5) Concentrations of BTEX were also detected ranging from 0 13 mglkg (TS-3) to 280 mg/kg (TS-5), 0 081 mg/kg (TS-3) to 800 mg/kg (TS-5), 0 024 mg/kg (TS-3) to 190 mg/kg (TS-5), and 0 098 mg/kg (TS-3) to 1,000 mg/kg (TS-5), respectively Analytical results show the soils from the r product piping trenches, designated TR, contained unspecified "petroleum hydrocarbons volatile" ranging from below the method detection limits to 21 mg/kg (TR-4) and no ethylene dibromide at or below method detection limits Concentrations of BTEX were also detected ranging from below method detection limits to 337 mg/kg (TR-2), 10 mg/kg (TR-2), 7 0 mg/kg (TR-2), and 20 mg/kg (TR-2), respectively Soil stockpile samples reported concentrations below the method detection limits for ethylene dibromide, benzene, toluene, r and ethylbenzene Concentrations of 0 930 mg/kg of xylene, 77 mg/kg of unspecified volatile hydrocarbons, and 1 5 mg/kg of organic Pb were detected in the soil stockpile samples There were 15 soil samples collected during the July 1990 installation of9 roundwater monitoring and vapor extraction wells Vapor extraction well VEW-1 was installed through the previously characterized backfill material No soil samples were collected from this boring Soil samples from vapor extraction well VEW-2 contained the highest concentrations of unspecified hydrocarbon volatiles These ranged from 2,800 ppm at 25 feet bgs to 12,000 ppm at 45 feet bgs In groundwater monitoring well MW-1, total xylenes were detected at a concentration of 0 0042 ppm at 50 feet bgs In groundwater monitoring well MW-2, toluene and total xylenes were detected at concentrations of at 0 0043 ppm and 0 0059 ppm, respectively, at 40 feet bgs In groundwater monitoring well MW-3, the concentrations of unspecified hydrocarbon volatiles were reported at 28 ppm at 55 feet bgs Concentrations of BTEX from 55 to 60 ft bgs were reported as follows benzene from 0 380 ppm to 0 0058 ppm, toluene from 0 790 ppm to 0 022 ppm, ethylbenzene from 0 180 ppm to 0 0047 ppm, and total xylenes from 0 990 ppm to 0 24 ppm In September 1995, Fugro West, Inc (FWI) drilled four sod borings GE01 to GE04 Nine soil samples and four groundwater samples were collected during completion of these N1Fde3lProjects\Chevron,Reta,R#9-61711s,te conceptual ModeI1FINAL CSM doc