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' Supplemental Investigation Report,Problem Assessment Report and Work Plan Cleanup and Abatement Order No 5-00-707 _ PAI Proiect No 1232 On September 12 and 13, 1991, 12 slant borings were hand augered to depths of approximately four feet bgs Soil samples PL-1 to PL-12 were collected along the product lines which ' extended between the former fuel islands and the former USTs locations (see Figure 3) No detectable concentrations of TPH were present in any soil samples tested, except for soil sample PL-7 (see Table 1) TPH (844 ppm), toluene (0 95 ppm) ethylbenzene (0 65 ppm) and xylenes (9 55 ppm) were detected in soil sample PL-7 @ 4-4 5' (see EAI, 1991A) In July 1992, EAI drilled and sampled four additional bonngs (Borings B-7 through B-10) Borings B-7 and B-8 were located in the vicinity of the sewer line and former gasoline USTs, and Borings B-9 and B-10 at the former fuel islands (see Figure 3) No TPH-G were detected in the samples collected from Boring B-8 (see Table 1) Only one sample from Boring (B-7 @ 5') contained a TPH-G concentration (43 ppm), and only one sample from Boring B-10 (B-10 @ 5') contained a TPH-G concentration (8 ppm) TPH-G concentrations encountered in Boring B-9 ranged from 1,220 to 3,490 ppm The total lead concentrations detected in samples collected from these four borings ranged from 5 72 to 13 4 ppm (see Table 1) (see EAI, 1992) Further, selected soil samples were also analyzed for carbon chain breakdown In February 1993, three borings (Borings B-11, MW-1 and MW-2) were drilled Two of the borings (Borings MW-I and MW-2) were converted into ground water monitoring wells MW-1 and MW-2 (see Figure 2) The analytical testing results of the soil samples obtained from borings drilled as part of this investigation show that TPH-G concentrations ranging from 6 9 to 3,110 ppm were encountered The highest concentrations of TPH-G were detected in samples collected from boring location MW-2 at depths ranging between 20 and 60 feet bgs (see Table 1) Elevated concentrations also were detected in the samples collected from Boring B-11 between 40 and 50 feet bgs BTXE were detected in many samples Several chlorinated hydrocarbons not associated with gasoline also were detected at selected sample locations, e g, tetrachloroethene (PCE), trichloroethane (TCE), and 1,1,1-tnchloroethane (1,1,1-TCA) The source of these chlorinated hydrocarbons is unknown (see EAT, 1993) Subsequent investigations were completed which consisted of collecting ground water samples from hydropunches (see Figure 5) and the installation of ground water monitoring wells MW-3 through MW-7 (see Tables 1 and 4) Table 3 presents well construction details for all wells on the Wards site, including those discussed in Section 2 2 3 Appendix A contains copies of the boring logs and well construction details 2 2 3 Remediation In July 1998, EAT on behalf of Wards submitted a Corrective Action Plan (CAP) for the Wards site (see EAI, 1998), which was reviewed and conditionally approved by the San Joaquin County PHS-EHD on August 12, 1998 The CAP called for implementation of air sparging coupled with vapor extraction to address the remediation of petroleum hydrocarbons present in soil and ground water beneath the Wards site BS 32J2P IRW_WP -5- ENVIRONMENTAL AUDIT, INC.®