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• Erratic pattern and low concentrations of VOC detections. Landfill gas conditions can fluctuate significantly depending on the available biomass and refuse moisture conditions. A liquid-phase release typically results in more consistent VOC detections and concentrations. • Listing of detected VOCs. The listing of VOCs associated with a liquid-phase release is often restricted to only few analytes. The VOC listing for the FSL is relatively extensive and includes fuel-product compounds such as benzene, toluene, and xylene, as well as chlorinated solvents such as DCE, TCE, and PCE. The presence of freon compounds such as dichlorodifluoromethane and trichlorotrifluoromethane are also considered key gas indicators. • Historical concentration of VOCs near upgradient wells MW-5A and MW-513. The groundwater gradient at the site is generally from south to north, and these 2 wells were located adjacent to Little John Creek, upgradient of WMU-B. • Absence of notable inorganic impacts. As described in the 1999 and 2000 Annual Monitoring Reports (Kleinfelder& Associates, 1999 and 2000), the inorganic groundwater quality measured in downgradient monitoring well samples is quite similar to upgradient groundwater quality conditions. The exceedences of inorganic concentration limits are considered minor and representative of natural variation in groundwater chemistry rather than a release from the facility. 4.0 POTENTIAL IMPACTS The potential impacts associated with the low-level VOC impacts to groundwater adjacent to the FSL appear small. Low-level VOC detections at the FSL were evaluated in the past in a groundwater modeling project that was completed by Kleinfelder& Associates (1991). Kleinfelder's work was completed in response to low concentrations of VOCs that were detected adjacent to U-B in monitoring well MW-5A, and included preparation of a RCRA Facility Investigation(RFI). The RFI considered a point-source release of VOCs near the southern border of WMU-B (near wells MW-5A and MW-5B), and concluded that offsite migration of VOCs was unlikely. Recognizing that modeling a source for the VOC release near the southern boundary of WMU-B was not a conservative assumption, LSA&Associates oversaw a modification of Kleinfelder's model by Geotechnical Research &Development(GRD) during development of the Environmental Impact Report (EIR) for expansion of the site (LSA, 1993). The GRD revision placed the source for VOC impacts near the eastern boundary of the site (i.e., near the downgradient border of the landfill). The GRD model concluded that the only VOCs that might reach the nearest offsite well (9690 S. Austin Road) were benzene and cis-1,2-DCE, and that the concentrations of these constituents at the offsite well location would be significantly less than ARARs. As indicated in Table 1, the property(and well) at the nearest offsite well (9690 S. Austin Road) is now owned by Forward Inc., and bottled water is delivered to the tenants that reside there. As indicated in quarterly monitoring reports, and as summarized on the (electronic) tabulated monitoring results, other than methylene chloride (a common laboratory contaminant)no VOCs have been detected in samples from wells at 9621 and 7 Geologic Associates