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,,. laboratory-prepared trip blank was 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 in Redwood City 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. Current results are also shown in Figure 1. Laboratory data sheets and chain-of-custody documentation are presented as Appendix B. ry 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 w Fugro are presented in Table 3. A new SVE system was installed by EA and was started on 21 February 1997. Soil vapor was 4 extracted from two wells (VEW I and VEW2), because the screened intervals for the other wells used in the past for vapor extraction (MW2, MW3, and MW5) were submerged. Influent TPH-g concentrations (prior to air dilution) and the estimated total pounds of hydrocarbons removed by I•. 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 had 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 ,v 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. An asymptotic trend in the cumulative mass of TPH-g removed can be seen in Figure 2. This result suggests that the SVE system has ,r effectively removed the volatile petroleum hydrocarbons from the vadose zone. The system operation was ceased on 10 April 1998. A verification boring work plan in pursuit of case closure was submitted for regulatory review. 4. WORK PROPOSED FOR NEXT QUARTER Iwo The seven groundwater monitoring wells and two vapor extraction wells will be gauged and monitored for the presence of LPH. The seven groundwater monitoring wells and two vapor extraction wells will be sampled, and the samples will be analyzed for TPH-g, BTEX, and MTBE. Pending regulatory review, comments, and response, the verification boring work plan will be implemented. 70137.Q 1098.TX.WPD 2 A+