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Canepa's Car Wash ><� September 23, 1996 Page-2- the ground surface (bgs) Mader to to strong petroleum odors were detected from 15 feet bgs to 56 5 feet bgs Elevated TFH-G and BTE concentrations were detected m soil samples collected from 35 feet bgs ' to 56 5 feet bgs Following the soil boring instal ation, a network of nine (9) SVE wells were drilled and installed in the ' area of the fuel dispenser island According to the former consultant, William H Fox of WHF, the SVE wells were installed without co piling geological logs and without the collection of laboratory samples as agreed upon by the PHS/ , 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), 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) Between September 28 and 30, 1993, WHF installed four (4) monitoring wells (MW-1 through MW-4) ' at the site (Figure 2, Appendix A) Low to elevated concentrations of gasoline were detected in groundwater samples collected from MW-I through MW-4 Field observations indicated moderate to strong gasoline odors in the soil at MW-1 from 20 feet to 55 feet bgs and at MW-2 from 40 feet to 67 feet bgs Soil samples collected from MW-1 and MW-2 were not analyzed in the laboratory Soil analyses of samples collected from MW-3 and MW-4 indicated no detectable TPH-G or BTEX from 20 feet bgs to the capillary fringe A summary of the soil and groundwater analytical data is contained in ' Interim Status Repo?t, 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 fully characterize the groundwater plume The PHS/EHD granted approval of the additional investigation on January 19 1994 Between March 9 and 11, 1994, WHF installed MW-5 through MW-8 (Figure 2, Appendix A) Moderate concentrations of gasoline were detected in the soil from MW-6 at 50 and 55 feet bgs and from MW-7 at 50 feet bgs Low to elevated concentrations of 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 are contained in Phase H Site Chaiacteii:,ation, by WHF The wells were surveyed and gradient calculations indicated that a groundwater mound existed beneath the site indicating that recharge or leakage into the groundwater in the vicinity of MW-1 and MW-2 was occurrin. Three potential sources of recharge were identified 1) the car wash water recycling pit system under the Ibuilding, 2) a leaking or broken sewer line that crosses the area, and 3) a leaking water supply line An viuAL) (i ietli'yi Blue Active 'jur uGtdiits) WM wdS GOHUMAed o[i g[uulldWdLei sdmples (,olleLaed at Life S1Le in July, 1994, to investigate the presence of detergents MBAS was not detected in the samples Aquifer testing (24-hour pump test) was conducted at the site by WHF on December 22 and 23, 1994 MW-I Nvas used as a pumping well, and MW-4 MW-6 MW-7 and MW-8 were used as observation wells The results indicated an optimum pumping rate of 5 gpm with an effective radius of 140 feet Aquifei permeability was estimated at 126 gpd/ft`' CONDOR