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Geotube dewatering containers help in cleanup of the Fox River

August 1st, 2006 / By: / Containment, Feature, Geotextiles

Cleansing the Fox: Decades of PCB contamination in Wisconsin’s lower Fox River will take decades to clean up. Today, geotextile dewatering containers are helping with that job at the Fox’s Little Lake Butte des Morts

The largest river cleanup project ever attempted in North America is using geotextile tubes as a key component in the process.

The EPA Superfund site in northeastern Wisconsin encompasses a 40-mile stretch of the Fox River and more than 1,000 mi.2 of Green Bay. Sediments in the river and bay are contaminated with an estimated 700,000 lbs. of PCBs. The chemicals were discharged into the river in connection with past production and reprocessing of carbonless copy paper containing PCBs at multiple manufacturing facilities along the river, primarily from the mid-1950s to the early ‘70s.

Geotextile tubes

The geotubes are instrumental in the process of dewatering the dredged contaminated river bottom sediment. The sediment slurry dredged from the riverbed is piped to a handling facility onshore where it is pumped into massive, porous, geotextile tubes. The fabric is porous enough to allow the water to run through, but traps the solids, compacting them, and making their removal and disposal easier. Water seeping from the bags is treated and returned to the river. The sediment, when sufficiently dry, is trucked to a landfill.

Currently, the project involves more than 75,000 linear ft. of 60-ft.-circumference x 200-ft.-long geotextile container bags. Previously, geotubes as large as 80 ft. in circumference were used. After dewatering, each 60-ft.-circumfrence geobag will contain approximately 1,000 yds.3 of sediment ready for the landfill.

To date, judgments directed at the cleanup remedy for different sections of the river and bay would require removal of 7.25 million yds.3 of contaminated sediment at an estimated total cost of more than $400 million.

PCB contamination

PCBs (polychlorinated biphenyls) are a group of manufactured chemicals. They were widely used in electrical equipment, in industrial processes, and in the manufacture and recycling of carbonless copy paper until research in the early 1970s demonstrated that they pose risks to human health, wildlife, and the natural environment. Their use and discharge into the environment were outlawed by federal environmental regulations in 1976.

The ban was successful, but because PCBs bind to dirt and break down slowly, they are still found today in the sediment of the lower Fox River and in Green Bay, which forms the northwest portion of Lake Michigan.

“The Fox River is the biggest source of PCBs flowing into Lake Michigan,” said EPA regional administrator, Thomas Skinner. “Cleaning up this hot spot [at the De Pere Dam] is a major step toward eventually removing the Fox and lower Green Bay from the EPA’s list of Great Lakes Areas of Concern.”

PCBs bioaccumulate, concentrating up the food chain as smaller species containing the chemicals are eaten by larger species. PCB levels in top predators such as bald eagles, lake trout, and humans can be millions of times those found in surface water. The PCBs at this Superfund site have caused adverse health effects and reproductive effects in fish and birds. Health advisories have been issued in the area regarding consumption of fish and waterfowl from the river.

After two decades of studies, state and federal regulators in 2002 and 2003 ordered seven paper companies to clean up the PCB-contaminated lower Fox River. Cleanup plans called for the removal of all river sediments with concentrations of PCBs greater than 1 part per million. With more than 7 million yds.3 of contaminated sediments identified, this is the largest river cleanup ever attempted in North America. It will take about 15 years and cost an estimated $400 million to complete the entire job.

The lower Fox flows north and east for 39 miles from the dam at Menasha to the mouth of the river at Green Bay. It is the largest source of PCBs flowing into Lake Michigan. For cleanup purposes, the lower Fox River is divided into 4 “operable units” (OU 1, 2, 3, and 4), with the bay (Green Bay) being a fifth OU.

Cleaning Little Lake Butte des Morts

Two paper companies — Glatfelter and WTM 1 (formerly Wisconsin Tissue Mill) — agreed to remove an estimated 784,000 yds.3 of contaminated sediment from Operable Unit 1, known as Little Lake Butte des Morts, a 6-mile-long widening of the Fox River downstream from the Menasha Dam. Full-scale dredging began in the summer of 2004. During 2006, more than 150,000 yds.3 of contaminated lake sediment is scheduled for dewatering.

Engineers estimate it will take another 5 years to entirely meet complete cleanup standards set for the lake. A total of nearly 800,000 yds.3 of sediment is expected to be dredged, dewatered, and landfilled. The OU-1/Little Lake Butte des Morts cleanup will cost the paper companies an estimated $66 million.

Future dredging and capping

The vast majority of the PCBs in the Fox River are situated in OU 4, the final 7 miles of the river, from the dam at De Pere to the outflow into Lake Michigan at Green Bay.

Two companies, Georgia-Pacific and NCR Corp., are completing advanced engineering inspections and tests on this downstream portion of the cleanup. Government regulators originally estimated there were nearly 6 million yds.3 of contaminated sediment in the 7 miles of river below the De Pere Dam, containing more than 90% of all PCBs in the lower Fox.

But after examining more than 1,400 core samples, engineers increased that estimate by at least 1 million yds.3 Additionally, engineers found a PCB hot spot, just below the De Pere Dam, with PCB concentrations of up to 3,000 parts per million.

Company engineers, with a more-detailed understanding of the sediments, have convinced state regulators that some areas of the river can be more effectively capped than dredged. In capping, layers of sand and rock are placed over the contamination, isolating it from the aquatic ecosystem.

Even areas that are dredged to specifications might receive a “blanket” of clean sand to speed the river’s recovery, said Bruce Baker of the Wisconsin DNR.

Future plans: While Georgia-Pacific and NCR have agreed to do the engineering, there is no agreement yet on who will conduct the cleanup or in what manner the paper companies will apportion costs among themselves. Other companies considered responsible include: Appleton, formerly Appleton Papers; Riverside Paper Co.; Sunoco, formerly U.S. Mills; and Arjo Wiggins, a French corporation that once owned Appleton Papers.

Sources

Glenn M. Lundin, Market Manager Pulp & Paper, Miratech (TenCate Geosynthetics)

Kris Naidl, Executive Vice President, Zeppos & Associates Inc.

Little Lake Cleanup Team

Lower Fox River Intergovernmental Partnership

U.S. EPA (Environmental Protection Agency)

Wisconsin DNR (Department of Natural Resources)

The Little Lake Cleanup Team, the Wisconsin DNR, and Ron Bygness, editor of Geosynthetics (formerly GFR), contributed to this article.

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