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4.0 CONCLUSIONS AND RECO1VI11'IENDATTONS Soil sampling in November and December 1994 indicated that hydrocarbon contamination is not widespread in shallow soils in the site area.'' Subsequent sampling in November 1995 confirmed RESNA's findings that chlordane and 4,4'-DDT are present at a depth of 6 feet in a very locahized portion of the property, but follow-up sampling in December 1995 and January 1996 has shown that neither of these pesticides is present below a depth of 6 feet or in the groundwater. However, heptachlor epoxide was detected in the water, and low concentrations of diesel were detected both in the water and in the soil between the depths of 8 and 15 feet. The sources of the diesel and pesticides are difficult to identify, but based on both the low concentrations and the limited areal extent, w6linfer that no more than a few gallons were spilled. The spill may have occurred during the initial landscaping of the property in 1980, or during the Naval occupation prior to 1965. In our opinion it is doubtful that the spill is more recent. Due to the hazardous nature of chlordane and DDT, we recommend the excavation of a limited volume of soil in the vicinity of SP-8, SP-10, and SP-11. A backhoe could be used to remove an area approximately 5 feet square to a depth of 7 feet (6.5 cubic yards). In view of the recent shift in the paradyme regarding gasoline and diesel contamination, we see no reason to excavate below 7 feet to remove the minute amount of diesel-range hydrocarbons remaining below that depth. For similar reasons, we do not recommend either further assessment or remediation of the groundwater contaminants detected in SP-10 and SP-11. i i j