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r response for benzene. Similarly, the column entitled "Total Detected Petroleum Hydrocarbons" or "Total Volatile Hydrocarbons" represents the sum of all V-sec responses, proportioned to for benzene. that The Photovac is operated in backflush mode to prevent contamina- tion of the analytical column with high concentrations of interfering compounds. Blanks are run-'to ensure that the system is free of contamination. As necessary, the instrument is re- calibrated by injecting standards and by running ambient air blanks approximately every two hours through the day. This re- calibration ensures that the system is operating consistently andthat parametric changes caused by temperature changes thou h;"the day are accounted for. data,These da�a, along with multiple standard runs, ensure system reproducibility, s 2.2.2: it i SVCA Results The SVGA chromatograms are in Appendix A; the results o and 24 November survey are summarized in Table 3, Because f the, 23 1 water in this area was reported between 47 and 50 feet in inthe eUund well logs, the soil vapor probes were driven anti encountered, at 15.5 to 23.5 feet 3) :.(see Table untilrefusal was I hydrocarbon contamination was detected at an . No significant sampling locations. The y of the vapor i headspace samples yielded low-to- ; moderate hydrocarbon. concent.rations. Weekly gauging of the monitoring wells has shown no evidence of floating product. ' ]y To verify the absence of hydrocarbons in shallow conduct 4 C -- - conducted a shallow :(3 to 5.5 i feet below land December .suriace) SVGA on 22 1887, These results are presented in. Table 4. locations were chosen" inside of the former :product line trench E at various points between the tank area and the nches. -V11, Fi are 4 pump islands (vi g . ) .. No significant contamination was detected in i the shallow soil vapor samples. p 5 c EXXON9:84L _; 10