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• 4.3 Laboratory Results A strong gasoline odor was noticeable in KF-2 and KF-3 when they were purged. As shown in Table 2, concentrations of most analytes in KF-3 were lower than previously reported by Blaine- Tech's laboratory (Sequoia Analytical) in August, whereas conentrations in KF-1 and KF-2 were slightly higher. Benzene concentrations are well above the hazardous concentration of 500 µg/l. The water concentrations remain far above those found in soil samples from the borings, possibly suggesting that the contaminant source is continuing to leak or that there are_multiple sources, some of which may be off site. Due to the high gasoline concentration in each sample, the laboratory was forced to dilute the samples prior to running the EPA 8250 analysis, and was therefore unable to attain the specified detection limits for most of the oxygenate compounds. MTBE was detected in two samples, but at significantly lower concentrations than those reported by Sequoia in August using EPA method 8020 (Table 2). Further, tert-butanol was detected with confidence in two samples; it may also be present in the third sample, but not above a concentration of 125 µg/1. It is our understanding that Ns compound has previously been detected in the wells at the Chevron site. Due to the high reporting limts for the other oxygenates, it is not possible to say with confidence whether these chemicals are present or absent. 5.0 CONCLUSIONS AND RECOMMENDATIONS • Based on the groundwater monitoring data collected to date, it is still not possible to determine the source of the gasoline, locate the center of the contaminant plume, or outline the affected area. However, the groundwater flow direction has been consistently in an eastward direction, and this may explain the apparent upward trend in contaminant concentrations in- ICF-2 (Figure 4). If concentrations in this well are in fact increasing, it is very likely that contamination extends beneath the residential property east of the site. Drilling planned for early 1998 should help to answer these questions. Wells are planned to the east and southeast of KF-3, and also to the northeast of KF-2. These wells will also provide a more detailed picture of the groundwater gradicnt. We anticipate performing this work in February 1998. In addition, plans are underway to remove the underground storage tanks from the site. Depending on weather and the time needed to obtain the necessary permits,removal will probably take place in the first quarter of 1998. Groundwater monitoring should continue on a quarterly basis. The next monitoring should be scheduled to coincide with the drilling activities planned for the first quarter of 1998. 4