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1 The analytical results for the samples collected on 13 February are presented in boldface type in Table 1, along with previous data The laboratory analytical report and chain-of-custody ' documentation are included as Appendix B Detectable concentrations of TPH-g in the samples ranged from 190,ug/L (MW 1) to 78,000 kig/L ' (RW4) Detectable benzene concentrations ranged from 4 4/,Zg/L (MW4) to 4,800,ug/L (RW3) The concentration of TPH-g in the sample collected from MWS, located adjacent to the Shell ' service station and upgradient of the site, was 57,000µg/L MTBE was found in the sample from well V3, at a concentration of 1,900µg/L Groundwater sample analytical results are shown in Figure 1 ' Petroleum hydrocarbon concentrations in the extracted soil vapor have decreased significantly since the startup of the vapor extraction and treatment (VET) system at the site, suggesting ' considerable progress in the remediation of the vadose zone As can be seen in Figure 4, the monthly monitonng of TPH-g concentration in the extracted soil vapor entering the VET system oxidizer indicates a 20-fold decline since startup The monthly monitonng of benzene ' concentration in the extracted soil vapor entering the VET system oxidizer indicates a more drastic decline of two orders of magnitude since startup (Figure 4) During the current quarter, petroleum hydrocarbon concentrations in the extracted soil vapor entering the VET system ' oxidizer have remained near the values observed during the previous quarter 88-140µgAL for TPH-g and 0 18-0 86,ug/L for benzene 3. WORK PROPOSED FOR NEXT QUARTER Groundwater elevations will be measured and groundwater samples will be collected in May 1996 The samples will be analyzed for TPH-g, BTEX, and MTBE The air sparging and soil vapor extraction system will continue to be operated and its progress monitored ' Because of the proximity of wells TWI and MW4, well P1 will be sampled only twice a year Similarly, because of the proximity of wells IW 1 and RW2, well MW2 will be sampled only ' twice a year On the same basis, well MW I will be sampled only twice a year, because of its proximity to well P2 Because concentrations of petroleum hydrocarbons in wells MW 12 and MW 13 have been consistently below method detection limits for at least the last five quarterly sampling events, those wells will only be sampled once a year Next quarter, in May 1996, all wells will be monitored for liquid-phase hydrocarbons, and groundwater monitoring wells MW3 through MW 10 will be sampled Recovery wells RW 1 through RW4 will also be sampled Piezometers PI and P2 will be sampled, along with infection well IW i Submerged vapor wells V2—V4 will be sampled if there is no sheen present In August 1996, the above wells will be sampled, along with P1, MW1, and MW2 In IFebruary 1997 all wells will be sampled WP61 73942Q296 4 2