When Rising Seas Meet Buried Plumes: Sea-Level-Driven Saltwater Intrusion and Legacy Contaminant Mobilisation at a Coastal Superfund Site

Abstract

Coastal aquifers on the Mid-Atlantic Coastal Plain face compounding threats from sea-level rise (SLR): rising water tables and saltwater intrusion that can disturb decades-old contaminant plumes, yet such interactions are rarely assessed within an integrated framework linking surface hydrology to subsurface flow and transport. As part of a larger framework that couples MODFLOW 6 (GWF-GWT) with EPA’s Stormwater Management Model (SWMM), we focus here on the below-ground system at Dover Air Force Base, Delaware; a Superfund site where legacy chlorinated solvents persist in a shallow, unconfined aquifer subject to tidal and sea-level influence. We simulate variable-density groundwater flow together with the transport of salinity and dissolved contaminants, imposing time-variant water levels and salinity at the tidal boundary under a 1.2 m sea-level-rise scenario. We evaluate how SLR-driven groundwater rise and salinisation alter the extent, flux, and persistence of existing plumes. Because remediation at the site relies on microbially mediated attenuation that is sensitive to salinity, these interactions bear directly on the long-term behaviour and persistence of the plumes. More broadly, the results illustrate how coastal contaminated sites can account for the compounding effects of sea-level rise when planning long-term remediation and site management.

Omowumi Erukubami

PhD Candidate

Austin K. Farnum

PhD Student

Dannielle Pratt

Postdoctoral Researcher

Carolyn B. Voter

Assistant Professor