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At this period the well headspace analysis technique was still being developed. Originally it was anticipated that soil gas vapors would be drawn through the screened portion of the well above the water table and into the sampling apparatus. Subse- quent experience with coupled well headspace and vadose zone gas measurements have shown inconsistencies that suggest that the two measurements are probably not representing the same medium. Contaminants in well headspace measurements may be more directly related to levels of volatile hydrocarbons in the water within the well than to volatiles in the vadose zone gas. .. For example, there is a reasonable qualitative relationship between well head- �space data and water analysis results for former Exxon-RS 7-1050 for the period June 1987 to February 1983 (Table 5: . The headspace data from'.h1ovem):,er 1987 are not sufficiently well- constrained that they tay_ be considered representative of current (February 1989.) soil vapor or. gioundwr:ter conditions. In July 1989 EA supervised the .drilling of . threes soil borings on the site. Numerous soil samples collected from soil borings penetrating .the entire unsaturated zone is locations specified by RWQCB (Figure 2) were found to not contain' TPH at concentrations I greater than, i '6 mg/kg,..or BTEX compounds at greater than .0. 14 mg/kg :(,Table b). Benzene was not detected in any of the soil I samples t levels :greater than the laboratory detection limit of { l 0 .005 mg%meg: . Routine OVA (FID) screening.of all of the soil samples.: at. the surface at the time of collection detected only - low-concentrations of organic vapors ( <30 ppm): in SB6 at 30 to 55 feet, and in''SB7 at- 30 to 40. feet (lithologic .logs, Appendix D) . . 6r 1 .3 PROPOSED' WO,K --WE The response to comments section above may be summarized .as fOIlow5 E fti; z e35%71450/2-90/�x 11. r ' r is ( - •;-. :. !