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

Area of Science:

• Environmental Science
• Risk Assessment
• Environmental Modeling

Background:

• Computer simulation models are crucial for decision-making at contaminated sediment sites.
• The reliability of these models in remedial decision-making requires validation through post-audits.
• The Neal's Landfill site presents a case study for evaluating model accuracy.

Purpose of the Study:

• To conduct a post-audit of a chemical fate, transport, and bioaccumulation model used at the Neal's Landfill site.
• To assess the model's accuracy in predicting polychlorinated biphenyl (PCB) concentrations in fish tissue and surface water.
• To demonstrate the utility of simulation models in guiding remedial actions for contaminated sediment.

Main Methods:

• Development of a chemical fate and transport and bioaccumulation computer simulation model.
• Post-audit analysis using several years of post-remediation data.
• Comparison of model predictions with actual observed PCB concentration declines over a decade.
• Inclusion of uncertainty analysis and a statistical Remedy Confirmation Clause.

Main Results:

• The model accurately predicted declines in surface water and fish tissue PCB concentrations.
• The post-audit confirmed the model's successful prediction of both natural recovery and remedial action impacts.
• The model correctly indicated that less extensive remediation would achieve risk-based goals.
• Uncertainty analysis and the Remedy Confirmation Clause supported decision-making.

Conclusions:

• Computer simulation models are valuable tools for guiding remedial decision-making at contaminated sediment sites.
• Retrospective studies (post-audits) are essential for validating model reliability.
• The Neal's Landfill case study validates the successful application of simulation modeling in environmental remediation.