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Method 8015) BTEX analysis was performed using EPA Method 8020 All analyses were performed at a DHS-certified hazardous waste laboratory. Analytical results for soil samples are summarized in Table 2 and presented on Figure 5. Complete, certified analytical reports and chain-of-custody records are ' presented in Appendix B Soil Sample Analytical Results - A total of four soil samples were collected and submitted for laboratory analyses. ' Soil samples collected from each borehole were screened using a photoionization detector (PID), which measures total ionizable vapors (TIV) The sample from each borehole having the highest TIV measurement was submitted for chemical analysis rThe sample with the highest TIV measurement was also screened in the field using an Immunoassay Screening Kit for TPHD This screening was performed to determine if further soil borings were warranted to define the horizontal extent of contamination. ' The test kit range of 100 and 1,000 ppm was chosen based on the results of the leaching potential analysis All of the samples tested in the field contained less than✓ 100 ppm TPH. Benzene, ethylbenzene, xylenes and TPHD were not detected above the reporting limit in any of the samples submitted for laboratory analysis (Table 2) The reporting ' limits were 0 5 ug/Kg (BTEX) and 100 mg/Kg (TPH) Toluene was detected in each of the soil samples with concentrations ranging ✓ between 0.7 and 3 4 µg/Kg. REGULATORY ASSESSMENT ' The Regional Water Quality Control Board (RWQCB) uses 100 mg/Kg TPH as the minimum criterion for characterization of groundwater in leaking underground fuel tank cases The DHS uses 1,000 mg/Kg as a minimum criteria for remediation One ' thousand (1,000) mg/Kg TPH is considered hazardous by virtue of its potential igmtability Many local implementing agencies (LIAs), such as SJCPHS/EHD, use the LUFT ' Manual (1989) as guidance in the assessment and cleanup of UFST sites The LUFT Manual recognizes three site investigation categories: Category 1, no evidence of soil contamination, Category 2, known soil contamination, and Category 3, known or ' suspected groundwater pollution. Analytical results for soil samples obtained during the removal of the UFSTs (Groundwater Technology, 1991) and this investigation indicate that the site can be classified under Category 2 (known soil contamination)✓ 23 During the initial site investigation, a leaching potential analysis for diesel (Table G 2-1, LUFT Manual was performed for the sample collected from B-1 at a depth of 25 0-26.5 feet below ground surface This sample contained 6,800 mg/Kg TPHD and ' 0 600 mg/Kg ethylbenzene According to the leaching potential analysis, the maximum allowable TPHD levels that may be left in the subsurface is 100 mg/Kg (Appendix D, Preliminary Site Investigation Report, November 1991) The general risk assessment criteria (Tables 2-2 and 2-3, LUFT Manual) indicate �n that the following concentrations of aromatic hydrocarbons are acceptable j �I FJSISY356 0510005 4