The fate and transport analysis for the lower aquifer will be performed once the Remedial Investigation Reports for AOI 4 and AOI 9 have been approved. Areas beneath the Site where connections exist between the lower aquifer and water table aquifer are less extensive than the areas where we have that important clay layer present. The cross section shown during the August 2020 Public Information Session was just one example from the site model that straddles the Schuylkill River where the aquitard is interpreted to be missing. Other cross sections show the continuity of that clay layer. Even where the aquitard is missing, it does not necessarily mean that water and contaminants will move down into the deeper aquifer. That potential has to do with pressure gradients that the model can simulate. The fate and transport model will simulate future scenarios based upon current conditions.
It is noted that the fate and transport analysis will include mapping of the middle clay unit aquitard. Water quality in the lower aquifer is monitored through routine sampling of groundwater from approximately 80 wells, and to date significant contamination has not been observed in the lower aquifer beneath the Site. Considering the aging and degrading petroleum sources in the water table from historic Sunoco sources, we do not expect groundwater hydrocarbon plumes to expand under current groundwater conditions.