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1 SI I�HISTORY ' CANEPA'S CAR WASH 6230 Pacific Ave ' Stockton, CA ' Canepa's Car Wash consists of an automated car washing facility, a fuel station and a convenience store Hie site is located at 6230 Pacific Avenue, in Stockton, California The car wash and fuel station has been in operation for over two decades ' Between February 25 and March 3, 1993, three underground storage tanks(USTs), fuel lines and dispensers were removed by WHF Environmental (WHF) and replaced with a doubled walled system The USTs consisted of two 12,000-gallon gasoline USTs and one 5,000-gallon diesel UST As reported by W14F, ' upon removal of the tanks and piping, it was discovered that the fuel Iines had leaked and that the USTs had been overfilled Approximately 600 cubic yards of soil were removed from the UST excavation area The excavated soil was subsequently characterized and disposed of at Forward Landfill in Manteca, California I At least 16 soil saimples were collected from the tank excavation for laboratory analyses The laboratory results indicated predominantly low TPH-G (gasoline at <15 rug/kg) and low BTEX concentrations One (1) soil sample collected from the northeastern sidewall of the tank excavation contained 773 mg/kg TPH-G I and BTEX concentrations up to 170,000 mg/kg (total xylenes) TPH-D (diesel) was detected in one soil sample at 32 mg/kg At least seven soil samples were collected from beneath the former fuel dispenser islands for laboratory analyses Elevated concentrations of TPH-G (up to 3,800 mg/kg) and BTEX concentrations ranging from 26 mg/kg to 560 000 mg/kg were detected in the fuel dispenser soil samples TPH-D (diesel) was not detected at or above the laboratory reported detection limit in the soil samples collected from beneath the former fuel dispenser islands On Mai ch 12, 1993, soil boring(B-1) was installed by R'HF immediately east of the former fuel dispenser islands Gioundwatei was encountered at approximately 56 feet below the ground surface (bgs) Moderate to strong petroleum odors were detected from 15 feet bas to 56 5 feet bgs Elevated TPH-G and BTEX concentrations were detected in soil samples collected from 35 feet bgs to 56 5 feet bgs Following the soil boring installation, a network of nine SVE wells were drilled and installed in the area of I the fuel dispenser islands According to the former consultant, William H Fox of WFIF, the SVE wells were installed without compiling geological logs and without the collection of laboratory samples as agreed upon by the PHS/EI-ID, due to time constraints Mr Fox indicated that based on field obser%ations, all of the SVE wells showed signs of gasoline contamination during installation An internal combustion unit (ICU) was installed at the site for vapor extraction and treatment under the Authority to Construct issued by the San Joaquin Valley Unified Air Pollution Control District (APCD), dated October 7, 1993 'Hie. ICU was started on March 11, 1994, and operated through June 10, 1995 Based on field monitoring notes provided by WHF, average influent organic vapor concentrations, measured with a photo ionization detector (PID), exceeded 2,200 parts per million (ppm) The last influent measurement collected from the Isystenn was 2,145 ppm (May 15, 1995) Bet-ween September 28 and 30, 1993, \ TIF installed four (4) monitoring wells (MW-1 through MW-4) at the site Low to elevated concentrations of gasoline were detected in groundwater samples collected from MW-1 through MW-4 Field observations indicated moderate to strong gasoline odors in the soil at MW-1 frons 20 feet to 55 feet bas and at MW-2 froin 40 feet to 67 feet bgs Soil samples collected from MW-1 and MW-2 rvere not analyzed iii the laboiator} Analyses of soil analyses of samples collected from MW-3 and MW-4 indicated that I'PH-G or BTEN were not detected at or above the laboratory reported detection