Fox_Riv

LimnoTech applies geostatistical methods, including full indicator kriging and “river straightening,” to estimate depths of PCB contamination in Lower Fox River sediments.

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Success Story

Sensible Solutions for Fox River PCBs

Sediments of the Lower Fox River and Green Bay in Wisconsin contain PCBs that were generated by production and recycling of carbonless copy paper in the mid-20th Century, presenting risks through the aquatic food chain. LimnoTech’s expertise in fate and transport modeling, database management, and geostatistics have helped to shape the remedy and facilitate stakeholder agreement on the trade-off between protectiveness and cost.

Problem

Remedial planning for this vast and complex site requires a sophisticated understanding of relationships between sources and risk-related impacts. LimnoTech’s clients in the Fox River Group needed to understand these links and their implications for alternative remedial strategies. Once a remedy was selected by the agencies, our clients also required recommendations for predesign sampling density, and state-of the-art mapping of contaminated sediment depths using the sample data.

Approach

LimnoTech worked collaboratively with the agencies to develop modeling inputs, and then constructed the FoxSim PCB fate and transport and food web models to illustrate key shortcomings of the incumbent model. LimnoTech also developed and populated a comprehensive site database to support the Fox River Group’s team of consultants. Once the remedy was selected by the agencies, LimnoTech used advanced geostatistical methods to map depths of contamination at varying levels of certainty, and then compute areas, volumes, and costs corresponding to varying degrees of remedial conservatism.

Result

LimnoTech’s input resulted in significant improvements to the agencies’ model and a greater recognition of the role of natural processes in the river’s ultimate recovery. LimnoTech’s database and fate and transport model remain key resources to the responsible companies in allocating remediation cost. Finally, LimnoTech’s innovative geostatistical mapping facilitated agreement between the companies and agencies over a sufficient degree of protectiveness for the dredging and capping remedy design.