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Soil vapor samples were collected at depths of 10 and 15 feet from borings SV-2,-3, -5, -8, -9, -10, -11, -12, -13, and-15. VOC concentration trends with depth indicated a decrease in concentration in some borings and an increase in others. Several borings showed a reversal in concentration trends with depth. Deeper soil vapor samples were collected from four borings (SV-1, SV-613, SV-7, and SV-14). The results of these samples are shown on Figure 10. The highest concentrations of VOCs including TCE, TCA, DCA, and DCE (concentrations of 340, 5,700, 620, and 680 ppbv, respectively)were detected at boring SV-7 at a depth of 29 feet, which may have partially penetrated the fine grained unit (Figure 11). The detections at SV-7 were also notable in that they were greater for all detected constituents than the shallower samples collected at 6 and 20 feet. The concentration of VOCs in samples from the other deep borings did not follow a clear pattern. A subsurface cross section of the LNC site depicting the lithology, soil gas analytical sample results, and sample results for groundwater is shown on Figure 12. Figure 12 also contains data from soil vapor samples collected in 1996 (WZI, 1996) and 2006. Geomatrix (2006) concluded that the 1996 WZI soil gas survey analytical laboratory results had significant uncertainty with respect to comparison of the 2006 soil gas analytical laboratory results because the original 1996 WZI analytical laboratory reports were not available for Geomatrix to review. The data shown on Figure 12 depict several possible VOC contaminant distribution patterns. Samples collected in 1996 by WZI at a depth of approximately 10 feet bgs were reported to indicate VOC concentrations that are typically one to two orders of magnitude higher than concentrations from nearby soil borings sampled by Geomatrix in 2006. This comparison of analytical results may suggest VOC concentrations in shallow soils at the LNC site are decreasing over time as suggested by Geomatrix (2006). Conversely, it may be possible that M ain\D:AEnvironmentaI\LN CV\10152007.wpd 28