EPA Superfund Site

HOCKESSIN GROUNDWATER

DE | EPA ID DEN000303920

About this site’s exposure pathways: As of May 2025, the Hockessin Superfund Site is considered "Insufficient Data to make a Human Exposure evaluation" (HEID). There is insufficient information to determine sitewide Human Exposure (HE) Control status at the Hockessin Groundwater Site because of a newly identified exposure pathway and/or contaminant(s) associated with Vapor Intrusion (VI) and potential for ingestion of contaminated groundwater.

EPA uses this Human Exposure status when there is a lack of evidence to suggest that actual or reasonably anticipated human exposures are occurring and that those exposures are above acceptable risk-based levels. The planned activities to collect sufficient information to evaluate this new exposure pathway and/or contaminant(s) are installation of shallow groundwater monitoring wells to delineate the PCE contamination in shallow groundwater. Assessment of the VI pathway will be completed based upon the extent of shallow groundwater contamination. Data from the shallow groundwater delineation and VI assessment will be used to conduct a risk assessment and determine whether or not human exposures to unacceptable levels of PCE contamination are occurring. EPA or the Delaware Department of Natural Resource and Environmental Control (DNREC) or potentially responsible party (PRP), or Federal Agency as appropriate, currently anticipates that there will be sufficient data to make a Human Exposure evaluation by September 2027 because of the time necessary to plan, implement and perform data evaluation.

In addition, EPA is currently evaluating the effectiveness of a time critical removal action taken at OU2 to treat the OU2 source area soils intended to eliminate continued contribution of PCE to further contaminate groundwater and elimination of potential VI in buildings adjacent to the source area.