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Ground water samples collected from Well S-4 contained 99 ppb TPPH, 130 ppb TEPH, 1 3 ppb benzene, and non-detectable levels of MTBE Fuel oxygenates were not detected in the ground water samples collected from this well Ground water samples collected from Wells S-5 and S-6 did not contain detectable levels of TPPH, TEPH, benzene, and MTBE Fuel oxygenates were not detected in the ground water samples collected from these wells Ground water analytical data are summarized on Tables 3 and 4 and presented on Plate 3 The certified analytical reports are presented in Appendix C CONCLUSIONS Soil samples collected from the CPT borings drilled adjacent to the potential former source areas indicate that vertical migration of petroleum hydrocarbons and fuel oxygenates in soil has not taken place Soil samples collected from these borings did not contain TPPH, benzene or fuel oxygenates TEPH was detected at the 51 to 52 foot depth range, but concentrations in soil were just slightly above the detection limit The soil samples from above and below this depth did not contain TEPH Ground water samples collected from the CPT borings contained low levels of petroleum hydrocarbons and MTBE However, based on the soil analytical results it appears that the source of ! the petroleum hydrocarbons and MTBE in ground water may not be the former USTs located on-site Ground water samples collected from the on-site Wells S-1 through S-4 contained TPPH at concentrations ranging from 99 to 23,000 ppb, TEPH at concentrations ranging from 130 to 7,800 ppb, and benzene at concentrations ranging from 1 3 to 190 ppb The highest concentrations of petroleum hydrocarbons were detected in Well S-2 located on the western property line Down gradient wells S-5 and S-6 did not contain detectable levels of petroleum hydrocarbons and fuel oxygenates, delineating the lateral extent of petroleum hydrocarbons to the north Fuel oxygenates (by EPA Method 8260) were detected in ground water samples from S-1, S-3, and CPT-2 Operations at this former Shell service station ceased in 1974 prior to use of oxygenating compounds in gasoline Therefore it is unlikely that fuel oxygenates detected at this site are due to a petroleum hydrocarbon release from the Shell service station formerly located at this site RECOMMENDATIONS Based on the findings of this investigation Cambria recommends that a quarterly ground water monitoring program be initiated at this site to collected additional ground water chemical data and to evaluate variations in ground water flow direction at different times of the year In addition, Cambria 240-0943 7