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GeolaBcca(Tecft ws Inc Page 6 Soil&Groundwater Investigation Report ' Ted Peters-AST Project No 7012 April 20,2001 j ' Table 3 in Appendix A is a summary of water level elevations, gradient slopes and bearings Figures 2 and 2A are groundwater gradient inaps for the February 16 and March 29, 2001 ' events, respectively Figure 3, Groundwater gradient Rose Diagram, illustrates the historical gradient data 3.3 Geology and Field Observations ' The following section discusses the subjective field observations and geology documented during this investigation based on the interpretations of the field geologist ' • Groundwatei was encountered at approximately 8 feet bgs Water depth in the monitoring wells was approximately 8 feet bgs ' • The gradient calculated on March 29, 2001 (using wells MW-4, MW-7 & MW-8) is anomalous when compared to past calculations using wells MW-4, 5 & 6 Additional data is needed before any conclusions can be made • The geology of this area of the site is predominately fine to coarse-grained sands A clay layer was encountered in boreholes MW-7 and MW-8 at a depth of 15 - 20 feet bgs • A diesel-like odor was observed in boring MW-7 at 10 feet bgs A soil sample from this ' depth did not contain detectable contaminants, however gasoline contamination was present in the well • The OVM detected volatile compounds at 10 ppm in the MW-7 @ 10 feet sample 4.0 CONCLUSIONS AND RECOMMENDATIONS 4.1 Conclusions Geological Technics Inc , taking into consideration the data obtained during the above soil and groundwater investigations, makes the following conclusions 1 The vadose zone soils around the former ASTs and dispensers contain elevated levels of ' diesel range petroleum hydrocarbons and volatile organic compounds 2 The groundwater in this area has also been impacted with diesel range hydrocarbons 3 Gasoline range petroleum hydrocarbons are present in groundwater on the western side of the property, but diesel is absent This shows that the gasoline plume has migrated ' further then the diesel 4 Soil contamination decreases rapidly with depth and is almost non-detect by a depth of 15 feet bgs ' 4.2 Recommendations Geological Technics Inc makes the following recommendations based on the conclusions ' outlined above 1 Continued quarterly monitoring of the existing groundwater wells will reveal trends in contaminant concentrations and groundwater gradient changes 2 The adjacent contamination site should be investigated to determine if the gasoline detected in GP-14, GP-21 and MW-7 is from an off site source