USING SEDIMENT TREND ANALYSIS TO UNDERSTAND PATTERNS OF EROSION AND DEPOSITION IN THE LOWER FOX RIVER, GREEN BAY, WISCONSIN IN SUPPORT OF CONTAMINANT LIABILITY ASSESSMENT

The Lower Fox River, located in northeastern Wisconsin, begins at Lake Winnebago and flows northeast for 63 km (39 miles) where it enters Green Bay and Lake Michigan. The river has numerous dams and has been divided into four operable units (OUs) with OU-4 the lowermost stretch between the De Pere Dam and Green Bay. The Fox River includes the highest concentration of pulp and paper mills in the world and from 1954 until the early 1970s, these mills used PCBs in their operations, releasing about 250,000 pounds of PCBs and contaminating 11 million tons of sediment. An agreement made in 2006 between the EPA and Wisconsin Department of Natural Resources with NCR Corporation and other paper companies resulted in a multi-year cleanup effort that included dredging to remove sediment and capping the river bottom with sand and gravel. Since the initial agreement, dredging has continued and companies EPA considers responsible for PCB contamination have been required by judicial order to complete the cleanup. A trial in 2013 involving the Department of Justice Environment & Natural Resources Division (DOJ) and the State of Wisconsin versus NCR Corporation et al. resulted in a ruling (currently in the appeal process) that the companies must comply with the earlier decision requiring them to continue cleaning up the Lower Fox River. Our involvement in this landmark case included serving as an expert witness (Singer) and using STA to establish the dynamics of sediment transport (sources, transport pathways and behavior) in OU-4. This work supported the DOJ's contention that contaminated sediment particles originating in the vicinity of the pulp and paper mills are not simply transported downriver, to become permanently deposited in its lower reaches. Rather the STA pointed to a much more complex system where sediments entering OU-4 are subject to continual recycling throughout the reach as a result of both down-river and up-river transport processes, the latter caused by seiche waves entering the Fox River from Green Bay.