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1 reading for temperature and electrical conductance, and 0 2 pH units or less change from the previous reading for pH) and a minimum of 3 casing volumes of groundwater were removed, ' purging was stopped and samples were collected using factory-cleaned disposable polyethylene bailers The samples were poured into 40 ml glass VOA vials, which were then preserved in an ice-filled cooler A field-prepared sampling equipment rinse blank and a laboratory-prepared trip ' blank were stored and transported in the cooler with the groundwater samples The samples were handled and transported under chain of custody ' The groundwater samples were delivered to Sequoia Analytical and analyzed for TPH-g by Cal EPA-modified EPA Method 8015 and for BTEX and MTBE by EPA Method 8020 Table 2 lists the analytical results for this quarter (in boldface type) and for all previous quarterly samplings TPH-g was detected in the samples collected from MW3, MW5, and MW7, at concentrations ranging from 67 µg/L (MW3)to 100µg/L (MW5) BTEX compounds and MTBE were not ' detected in any of the samples at concentrations equal to or greater than the method detection limits Analytical results are shown in Figure 1 Laboratory data sheets and chain-of-custody documentation are presented as Appendix B 1 3 REMEDIATION SYSTEM STATUS ' An SVE system was installed at the site by a previous consultant (Fugro) and operated for approximately 5 months, from November 1995 to March 1996 Performance data collected by Fugro are presented in Table 3 A new soil vapor extraction (SVE) system was installed by EA and was started on 21 February 1 1997 During this quarter, soil vapor was extracted out of two wells (VEW1 and VEW2), because the screened intervals for the other wells used in the past for vapor extraction (MW2, MW3, and MW5) were nearly completely submerged Influent TPH-g concentrations and the estimated total pounds of hydrocarbons removed by the system are shown in Table 3 and Figure 2 As can be seen in Table 3, as of 30 March 1998 the SVE system has removed approximately ' 1,551 pounds of TPH-g since the system was originally installed in November 1995 Laboratory analytical results for samples of the extracted soil vapor collected by EA are shown in Table 4 The SVE system was shut down from 5 February to 26 March 1998 for replacement of the activated carbon and to determine whether a rebound in extracted petroleum hydrocarbon concentrations would occur upon system restart The SVE system was sampled on 30 March ' 1998, three days after restart As can be seen in Table 4, the sample of extracted soil vapor had non-detectable concentrations of TPH-g and BTEX This result indicates that the SVE system has effectively removed the petroleum hydrocarbon from the vadose zone A clear asymptotic ' trend in the cumulative mass of TPH-g removed can be seen in Figure 2 The system will be operated on a pulse mode until regulatory approval is granted to cease its operation WP61 70137 Q198 TX 3 2