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Geological re&%icsIn[a Page 6 Site Characterization Report Project No. 1218.2 February 9,2006 ,,,, • The soil samples collected at 28 and 44 depths from SB-5 did not contain petroleum contaminants above the laboratory reporting limits. These samples correspond to 20 and 31 feet bgs, respectively, due to the 45° drill angle. The contaminant concentrations (including from borings GP-1 through GP-3) are superimposed on the cross sections in Figures 6 and 7. See figure 3 for cross section LM locations. GTI's interpretation of the soil plume is indicated in the figures. �.. 4.0 CONCLUSIONS AND RECOMMENDATIONS This investigation was an effort to determine the possibility that a former UST located on the �. west side of the building may have leaked and impacted the soil and groundwater with petroleum hydrocarbons. �. Based on our interpretation of the data collected over the course of this subsurface investigation, GTI have reached several conclusions. These conclusions are based on the premise that the data we considered, although incomplete, are representative of actual site �.. conditions. We acknowledge that there may be undiscovered conditions, which would upon their consideration,change our interpretation and thus our conclusions. .. Our recommendations are based on our knowledge of site conditions, and on the state and limitations of subsurface investigative technology. �. 4.1 Conclusions 1. There is a small amount of diesel and gasoline in the shallow subsurface at this site. The +� contamination appears to be limited to a small area near the former dispenser above 30 feet bgs. • The contamination is defined vertically by the low to non-detect concentrations of 6" TPH-G &TEPH-D that attenuate with depth. • The contamination is defined to the north, west, south and east below 20 feet bgs in borings SB-1, S13-2, SB-4 and SB-5, respectively. • The contamination is limited to soil and is not likely to reach the groundwater table based on the lack of detectable contaminants in the water sample from SB-3 at a depth of 50—60 feet bgs. `" • The diesel contamination in SB-1 at 12 feet bgs may be from a surface spill rather than the northern extent of a UST system release. This is supported by black soils in SB-1 at 0—5 feet bgs depths rather than brown soils as seen in SB-2. • The lateral extent of the plume is shown in Figure 8. 2. The predominantly fine grained silts and clays encountered at the site would tend to restrict the vertical movement of contaminants. 3. Given the data presented above and given that the source was removed years ago, we conclude that even though there is some small amount of gasoline and diesel present in