We present a case study for a remediation approach to address sediment impacted by NAPL and other contaminants its that minimizes the need for dredging as the go-to option for a former refinery discharge lagoons where residual sediment contamination is topped by cleaner river deposits.

The framework identifies the appropriate remedy for each portion of the lagoons based on contaminant bioavailability, mobility and exposure potential. Areas with low potential will be addressed via risk-based closure, while areas with higher concentrations will be evaluated for contaminant mobility and in-situ capping. If any NAPL present could migrate then additional remedy steps will be considered.

Preliminarily 3 of 6 lagoons meet conditions for risk-based closure, while contaminants in the 3 others are mostly amenable to capping. NAPL migration potential will be determined, which would trigger localized additional remedy. This framework drastically reduces remedial cost and yet is protective of human health and the environment and acceptable to Agencies.

Primary Author / Conference Presenter:
Bjorn Bjorkman
GEI Consultants, Inc.
Fort Collins, Colorado, USA

Thomas Daigle, GEI Consultants; Mike Hawthorne, GEI Consultants; Camille Carter, GEI Consultants (Denver, Colorado office)
Mike Ruetten, GEI Consultants (Green Bay, WI office)