Panel Finds Fox River Dredging Effective
Technology for removing PCBs called “very clean, precise.”

The 1998-99 Fox River dredging demonstration project at Kimberly, Wis., showed that dredging is an effective mechanism for removing contaminated sediments from the river, according to a report by the Fox River Remediation Advisory Team (FRRAT).

The five-member FRRAT, including Philip Keillor, UW Sea Grant Advisory Services coastal engineer, and David Armstrong, coordinator of UW Sea Grant’s sediment remediation thematic area, also concluded that "shoreside processing was an effective means of concentrating and permanently removing contaminated sediments from the river."

The advisory team’s report focused on Phase One of the dredging demonstration project on the west lobe of "Deposit N" on the Fox River near Kimberly conducted between Nov. 1998 and Jan. 1999 by the Wisconsin Dept. of Natural Resources (WDNR).

"The demonstration project showed that in 32 days nearly 38 pounds of PCBs and five pounds of mercury were permanently removed from the Fox River," said FRRAT chair James Hurley of the UW- Madison Water Resources Institute. "This is a substantial amount that will not be transported downstream to Green Bay [Lake Michigan] and possibly enter the food chain."

According to Hurley, the advisory team’s analysis also showed that "once the PCBs and mercury reached the shoreside processing facility, greater than 99.99% of the contaminants were removed and trucked to the landfill." The FRRAT report estimates that effluent from the processing facility returned less than a gram of PCBs to the river.

The advisory team estimates that four pounds of PCBs were lost to the river during Phase One dredging at Kimberly, which it called "small" compared with the 9-11 pounds of PCBs that the deposit would likely have released over the following year had no dredging taken place.

"The dredging demonstration at Deposit N was clearly a success," said FRRAT member Jon Manchester of the UW-Madison Water Chemistry Program.  "This was not your dirty, clam-shell type dredging operation. Some loss to the river is unavoidable and to be expected, but our data indicate the high-tech hydraulic dredge used for this demonstration was very clean, precise, and effective in vacuuming up contaminated sediments from the site."

While the dredging reduced the surface concentration of PCBs at the site by only one-third, the FRRAT concluded that 89% of the mass of PCBs in Deposit N was removed and that the remaining PCB mass in the deposit area amounts to less than six pounds of PCBs, which is less than the area had been releasing into the Fox River and the atmosphere annually. About 81% of the mercury in Deposit N also was removed, the FRRAT report says.

The FRRAT was formed in April 1998 at the request of the WDNR to review plans by the Fox River Group, a coalition of seven paper mills, for monitoring the effectiveness of dredging at the Deposit N site at Kimberly. Besides Hurley, Armstrong, Keillor, and Manchester, the team also included Jeffrey Steuer of the U.S. Geological Survey, Middleton, Wis.

 Copies of the FRRAT report are available free of charge from the UW-Madison Water Resources Institute, 1975 Willow Dr., Madison, WI 53706-1177, phone (608) 262-3577.  It can also be read online or printed from the WRI Website, www.wri.wisc.edu.

-- Stephen Wittman, UW Sea Grant Assistant Director for Communications

Last updated 24 October 2000 by Karl
All contents copyright 2000 University of Wisconsin Sea Grant Institute

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