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Samples from DMW-5 (26 feet bgs) and from SB-20 (21 feet bgs) were selected for further analysis, is because they contained the highest levels of contamination The soil analytical results confirmed previous findings that TPH-d is the only organic constituent in sods at this Site The results presented in Table 1 show that only 2 samples exceeded 100 mg/kg TPH-d at 1,900 mg/kg and 2,800 mg/kg, respectively Although nominal concentrations of TPH-g were reported (<50 mg/kg), the chromatograms are not typical of gasoline Low concentrations of BTXE (< 1 ppm) were reported, but those constituents are present in minor concentrations in diesel fuel All three analyses for volatile halogenated hydrocarbons were reported as non-detects The distribution of TPH-d with soil depth is consistent with previous investigations (Kleinfelder, 1987, Dames & Moore, 1988, Dames & Moore, 1994a) The placement of the soil borings and monitoring well was intended to identify the most heavily TPH-impacted soils on the Site, based upon all previous data and field observations During excavation of TPH-d-impacted soil in 1990, confirmation sampling conducted in the base of the excavation indicated that the highest levels of TPH-d concentrations may be encountered . at 20 to 28 feet bgs in excess of 5,000 mg/kg (Dames & Moore, 1992) The results presented in Table 1 suggest that maximum concentrations are somewhat lower, with a maximum of 2,800 mg/kg TPH-d encountered at 21 feet bgs in SB-20 The maximum concentrations of TPH-d in soil boring and monitoring well samples was encountered between 21 and 26 feet bgs From 26 to 36 feet bgs, TPH-d concentration dropped sharply to non-detectable levels (<5 mg/kg) at 36 feet bgs There were no reported detections of any organic constituents between 36 feet bgs and groundwater, which was encountered at 56 feet bgs 4 2 EVALUATION OF HYDROCARBON MOBILITY Additional testing was conducted on the most contaminated soil samples (DMW-5-26 and SB-20-21) to evaluate total and soluble hydrocarbon constituents which may be mobile in the soil column The RWQCB has developed a Leachability Factor (LF) analysis to evaluate the leachable fraction of a soil, sludge or solid material, and this is presented in the Designated Level Methodology (DLM) (Appendix E, p 20) According to the DLM, so long as the soil is not ingested by humans SAC156 14 7 DAMES &MOORE