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spread beyond MW-2 , MW-3 , and MW-4 . Halocarbon contamination is still more widespread, encompassing all of the monitoring wells and the domestic well. The concentrations of the gasoline compounds are highest in MW-2 , which is the farthest of the three wells from the former UST cavity and is presently up-gradient from the cavity. There are several possible explanations for this contradiction. As noted in section ' 4 . 3 above, the unusually low groundwater gradient could be easily reversed by groundwater withdrawal. Pumping of the domestic well and/or other industrial wells to the south or west could have created a local cone of depression and caused flow of contaminated groundwater from the tank cavity toward MW-2 . Alternatively, the UST leak may have occurred when natural groundwater flow was to the southwest, prior to the development of the groundwater depression east of the site. It is also possible, though less likely, that the UST was not the source of the contamination. In contrast to the petroleum hydrocarbons, halocarbon ' concentrations show no clear pattern in the monitoring wells, suggesting they may have a source and lateral limit that are different from that of the benzene and TPH. The presence of halogenated hydrocarbons in the domestic well suggests that the plume of HVOC-contaminated groundwater is at least 250 feet long in a north-south direction. HVOC concentrations are higher in the ' domestic well than in the monitoring wells, suggesting further that the source of the halocarbons may be closer to the domestic well than to the monitoring wells. Halocarbons are highly mobile in groundwater, however, and are known to form very large plumes that ' may migrate long distances from their source, which may be a dense liquid that is heavier than water. GeoAudit believes that further assessment of the nature and extent of the plume is advisable ' before proposing any groundwater remediation. Concentrations of volatile halocarbons in the domestic well exceed Maximum Contaminant Levels (MCL's) or Action Levels (AL's) for drinking water in California. It .is our understanding that the well is no longer being utilized as a source of drinking water. This practice should continue, in view of the potential health risks. I 6. 0 LIMITATIONS Ourrofessional services ervices were performed using that degree of care and skill ordinarily exercised by environmental consultants practicing in this or similar localities. The findings were mainly based on analytical results provided by an independent laboratory. Evaluations of the geologic conditions at the site for the purpose of this investigation are made from a limited number of available data points (i. e. monitoring wells) and subsurface conditions may vary away from these data points. No other warranty is made as to 13