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Cauepa'sCar Wash (Pacific Avenue) N Problem Assessment Report and Corrective Action Plan Page 2 concentrations up to 170 ,000 mg/kg (total xylenes). TPH-D (diesel) was detected in one soil sample at 32 :i mg/kg. At least seven soil samples were collected from beneath the former fuel dispenser islands for laboratory analyses. Elevated concentrations of TPH-G (tip 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. TPI I-D (diesel) was not detected at or above the laboratory reported detection limit in the soil samples collected fi-run beneath the former fuel dispenser islands. Soil boring B- 1 was installed in March 1993 by WHIP immediately east of the former fuel dispenser islands. Groundwater was encountered approximately 56 feet below the ground surface (bgs) . Moderate to strong petroleum odors were detected from 15 feet bgs 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 the fuel dispenser islands. According to the former consultant, William H. Fox of WHF, the SVE wells were installed without compiling geological logs and without collecting laboratory samples as agreed upon by the PHS/EHD due to time constraints. Mr. Fox indicated that, based on field observations, 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) and dated October 7, 1993 . The 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 system was 2, 145 ppm (May 15, 1995). In September 1993 , WHF 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 in MW- 1 from 20 feet to 55 feet bgs, and in the soil at MW-2 from 40 feet to 67 feet bgs . Soil samples collected from MW- I and MW-2 were not analyzed in the laboratory. Analyses of soil samples collected from MW-3 and MW-4 indicated that TPH-G or BTEX were not detected at or above the laboratory reported detection limits from 20 feet bgs to the capillary fringe. A summary of the soil and groundwater analytical data is contained in Interim Status Report, Phase II Investigation by WHF . Based on the initial data, the vertical and lateral limits of contamination were not sufficiently defined. WHF proposed the installation of four (4) additional monitor wells (MW-5 through MW-8) to more fully characterize the groundwater plume. In March 1994, WI-iF installed MW-5 through MW-8 . TPH-G was detected in the soil sample collected from MW-6 at 50 and 55 feet bgs and from MW-7 at 50 feet bgs. TPH- G and BTEX were detected in groundwater samples collected from MW-6, MW-7, and MW-8 . A summary of the soil and groundwater analytical data is contained in Phase II Site Characterization by WHF. The wells were surveyed and groundwater elevation measurements indicated that a groundwater mound existed beneath the site. This suggested that recharge or leakage into the groundwater in the vicinity of MW- 1 and MW-2 was occurring. Three potential sources of recharge were identified: 1 ) the car wash water recycling pit system under the building, 2) a leaking or broken sewer line that crosses the area, and 3 ) a leaking water supply line. A Methyl Blue Active Surfactants (MBAS) test was conducted on groundwater samples collected at the site in July 1994 to investigate the presence of detergents. MBAS was not detected in the samples. A 24-hour pump test was conducted at the site by WHF in December 1994. MW- 1 was used as a pumping well, and MW-4, MW-6, MW-7, and MW-8 were used as observation wells. The results indicated an 1 n �i l� CONDOR