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s� 4 0 CONCLUSIONS AND RECOMMENDATIONS 1 Soil and groundwater beneath the site are impacted by diesel and gasoline hydrocarbons, in relatively equal proportion Concentrations of benzene are not present or significant in sod and are relatively low in groundwater Except for a couple of trace detectable concentrations, MTBE, ' DIPE, ETRE, TAME, TBA and 1,2-DCA are not present in soil or groundwater The bulk of the petroleum hydrocarbon mass remains concentrated in sod beneath and in close ' proximity to the former USTs The highest concentrations of diesel and gasoline hydrocarbons were detected in the Geoprobe soil boring SB-1, drilled through the former UST excavation The soil samples collected from the vadose (i e , unsaturated) zone and capillary fringe interval contained the highest concentrations Impacts to soil in the vadose zone are defined to the proximity of the former UST excavation Impacts to soil in the capillary fringe interval and zone of groundwater fluctuation, are not fully defined Vertically, the concentrations in sod decline rapidly with depth below the groundwater table, and are defined above 43 feet bgs Impacts to groundwater at the water table are not defined The highest concentrations of diesel and gasoline hydrocarbons in groundwater remain concentrated near the former UST excavation These petroleum hydrocarbons appear to have migrated from the source preferentially to the northwest and west, in an apparent downgradient direction Concentrations in groundwater are lower in samples collected to the south and east of the source Based on these conclusions, Ramage Environmental recommends that additional environmental corrective actions be completed at the site Prior to proceeding with the additional corrective actions, PHSIEHD had requested in their letter dated May 16, 2000 (Appendix A), that the interested parties meet to discuss the site information and to prioritize the work relative to five other county sites In the meantime, Ramage Environmental recommends the following ' 1 Continue to monitor and sample groundwater at the site on a quarterly basis The next groundwater monitoring is scheduled for March 2001 2 Complete the sensitive receptor survey for the site vicinity and include it in the next quarterly groundwater monitoring report, due for publication in early May 2001 3 Complete project tasks outlined in the PHSIEHD May 16 2000 letter for each f P P J Y n the six county ' sites, and meet to discuss site information and priorities 13