SITE INFORMATION AND CORRESPONDENCE FILE 2

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The depth to groundwater in well VEW-3 has been decreasing from 7.25 feet bgs in March 2002 to 8.68 feet bgs in September 2002. Correspondingly,the concentrations of the MTBE TBA and TPHG has been decreasing, again suggesting a sorption and desorption relationship between soil and groundwater. However,available soil analytical data does not indicate the presence of a NAPL source in the soil that could have contributed to the petroleum hydrocarbon concentrations observed in well VEW-3. In addition,limited over-excavation was performed during removal of the former USTs(soil excavated from base of pit)and during installation of existing USTs (excavation at northern end of pit,including destruction of well VEW-2). Even so,a small amount of impacted soil unidentified during the over- excavation could lead to a potential problem in the groundwater in the future. C. The consultant evaluated the scenario where the Palisades facility could have had a new release. Review of the concentration of petroleum hydrocarbons in well VEW 3 indicates that MTBE, TBA, and TPHG were detected in high concentrations,but BTEX components were not. Ifthere was a release from the Palisades facility,BTEX components should also have been detected in well VEW-3 along with TPHG and oxygenates. These were not detected in well VW-3 in the first quarter 2002. However, the fourth quarter 2002 data for the site indicates the presence of benzene(183 ppb)and high concentration of TBA(96,300 ppb)in well VEW- 3. This recent increase in benzene and TBA concentrations could be interpreted as delayed arrival of these compounds. Yet,typically,one would expect to observe higher concentrations of aromatic hydrocarbons from a new release in a well located so close to the UST complex. Also,if the recently detected MTBE concentrations in well VEW-3 were from a release at the Palisades facility,it would be expected that the MTBE plume should be seen migrating downgradient of the site. To date,however, an increase of TPHG or MTBE concentrations in downgradient wells MW- 5, W5,MW-6,or MW-10 have not been detected In conclusion,it is Palisades'position that it is the responsibility of the current responsible party(Exxon)to conclusively prove that there has been a new release. Palisades suggests that Exxon perform the following actions to further clarify if this is a old or new release: (i) Collect and analyze a groundwater sample from well VEW 3 for fuel fingerprint.This analysis should allow the relative age of the dissolved hydrocarbons in the well to be estimated