Model‐supported decision‐making at a contaminated sediment site: Post‐audit and site closure

Abstract

Computer simulation models have been used to support decision‐making at contaminated sediment sites for decades. Nonetheless, their reliability in remedial decision‐making has been questioned, and there is a need for retrospective studies of the accuracy of model predictions, that is, post‐audits. The Neal's Landfill site near Bloomington, Indiana, provides an example of the successful use of a mathematical simulation model in the selection of a remedy for a site that includes streams with polychlorinated biphenyl (PCB)‐affected sediment, water, and fish. A chemical fate and transport and bioaccumulation computer simulation model was developed to compare the effectiveness of alternative remediation plans in reducing fish total PCB concentrations. A post‐audit of the model, using several years of data collected after remediation, demonstrates that the model successfully predicted declines in surface water and fish tissue PCB concentrations over a decade, including those associated with longer term natural recovery processes as well as the response to remedial actions. The model predicted, and the post‐audit bore out, that risk‐based goals would be met using an alternative less extensive than others under consideration. An uncertainty analysis, based on bounding model calculations, provided important support for decision‐making, as did the inclusion of a statistical Remedy Confirmation Clause in the Consent Decree for the site. This study demonstrates the utility of a computer simulation model to guide remedial decision‐making at a contaminated sediment site. Integr Environ Assess Manag 2022;18:1233–1245. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).