The world’s largest sediment remediation project is currently taking place in northeastern Wisconsin at the Lower Fox River and Green Bay Superfund Site. The project began in 2008 and will ultimately result in the remediation of 7.5 million cubic yards of contaminated sediment.
Advanced Disposal has partnered with the project’s general contractor, Tetra Tech, to provide environmentally-sound waste disposal of approximately 3.4 million cubic yards of sediment contaminated by polychlorinated biphenyls (PCBs), a toxic substance and probable human carcinogen. From 1954 to 1971, several pulp and paper production facilities released PCBs into the Fox River directly or after passing through the region’s municipal wastewater treatment plants. PCBs have a tendency to sink and adhere to sediments along the river bottom, and the result was a contaminated area stretching for nearly 40 miles from the Lower Fox River through the bay of Green Bay to the point where it enters Lake Michigan. The waterways also contain other contaminants such as dioxins, arsenic, lead, mercury and the pesticide DDT, and the project’s remediation process will address these substances as well.
As part of the remediation program, Tetra Tech is responsible for the removal of 3.4 million cubic yards of PCB-impacted sediment for a 13 mile stretch of the river and placement of nearly 600 acres of capping material to remediate another 4.1 million cubic yards of impacted sediment.
The site has been divided into five operable units by the Response Agencies. The first unit has had 371,600 cubic yards of PCB-contaminated sediment dredged and 260 acres capped with sand and armor stone or covered with sand. Although the effective removal of PCBs from an active river bed poses many technical challenges, a recent EPA-led five year review of the project noted that total PCB concentrations in surface sediments within this unit have already decreased by 94%.
An interesting side story is during the ongoing cleanup, the team discovered river commerce artifacts dating back to the late 1800s and early 1900s. Partially submerged hulls of two steam-powered tugboats – the Bob Teed and Satisfaction – and debris from old barges had to be removed. These vessels were declared historical artifacts under the National Historic Preservation Act and will be part of an interpretative display at Brown County Neville’s Museum set to open in December 2014.
Remedial construction activities in all units are scheduled to be completed by 2017. Long-term monitoring of the area will continue until the PCB concentrations in sediment, surface water and the animals and plants within the region no longer represent an unacceptable risk to human health and the environment.
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