Hydraulic dredge is doubtful here
Thursday, June 23, 2005 JEREMIAH STETTLER THE SAGINAW NEWS
It hums like an air conditioner, sucks like a steam cleaner and looks like the answer to PCB pollution in a river system not too far from the troubled Tittabawassee watershed.
James J. Hahnenberg, project manager for the U.S. Environmental Protection Agency's cleanup of the Fox River, said a hydraulic dredge promises a long-term fix for water contamination in northeast Wisconsin.
By 2018, the machine will have sucked about 7.2 million cubic yards of sediment from the Fox River -- enough to fill a football field three-quarters-of-a-mile high -- removing most of the PCBs that now keep people from eating the fish.
The question is whether a similar solution could exist for the Tittabawassee River.
The topic drew about 60 people to a lecture Wednesday at Delta College sponsored by the Lone Tree Council and state environmental groups.
"We aren't trying to draw conclusions," said Michelle Hurd Riddick, Lone Tree spokeswoman. "Our whole goal is to get that discussion started. We have to have the vision that someday we can have clean, fishable rivers in the Saginaw-Bay watershed."
The lecture focused on a $400 million dredging project along the Fox River that ultimately will scrape about 60,000 pounds of polychlorinated biphenyls, or PCBs, from the river.
The pollution is linked to seven paper mills along the upper Fox near Lake Winnebago. Beginning in 1954, the companies dumped PCBs into the river as part of their carbonless copy paper business.
Now those same companies must dredge almost half of the 39-mile channel.
Hahnenberg, who oversees the project, said the hydraulic dredge has proved effective. The machine, which works much like a snowblower with a vacuum attached, has removed up to 96 percent of PCBs during demonstration runs.
But the technology probably won't work along the Tittabawassee River, state Department of Environmental Quality officials say. The river is too shallow.
The Fox River is about 15 feet deep on average. The Tittabawassee River is about 7 feet deep.
A waterborne dredge would find it difficult to operate in such shallow waters, said Al Taylor, senior geologist for the state's Waste and Hazardous Materials Division. But another kind of dredge might work.
"It probably isn't practical by the boat technology," he said. "But it certainly is very practical in a dry method. You build a road essentially. You divert the water, dig it up in the dry and then remove it."
But Taylor said any speculation on how to clean the Tittabawassee River is premature. He said the state and polluter Dow Chemical Co. are several years from making that decision.
"We are quite early in the process," Taylor said. "We don't understand the distribution of the contamination yet or where the contamination is. There are some fundamental questions that need to be answered before you can even begin talking about what's appropriate for cleanup."
Dow is to submit strategies for developing a long-range cleanup plan by the end of the year.
Cleanup within the upper Fox River began in September and likely will take about six years, Hahnenberg said. The agency then will burrow into the more contaminated channel downstream -- a process that will continue until 2018.
Depending on where the pollution lies, Hahnenberg said the dredge will dig anywhere from one foot to 10 feet into the river bottom. Here's how the process works:
The sediment, sucked through a pipeline onto shore, is pumped into tubes that resemble giant sausages. These geotextile tubes capture the river spoils but allow the water to drain out onto a gravel pad where it is collected, treated and released back into the river.
The tubes, measuring 200 feet long and 30 feet wide, sit for a month until they are dry. Finally, the sediment is sent to a landfill engineered with a lining and water collection system to handle such waste.
Were dredging to occur along the Tittabawassee River, state officials say the spoils could go to a disposal site along the border of Frankenlust and Zilwaukee townships.
While the 281-acre facility is designed for a navigational dredging project along the Saginaw River, Taylor said the site is engineered to handle contaminated sediment.
As for keeping the water clean, Hahnenberg said the hydraulic dredge captures most of the sediment it stirs, preventing pollutants from drifting downstream.
"You really don't lose that much," he said. "It wasn't zero, but it was very, very small."
No odor is noticeable and the noise from shore is no more than what you would hear from your air conditioner, Hahnenberg said.
While plants and river-bottom critters take a beating during the process, he said both generally will re-establish themselves within a year or two. v
Jeremiah Stettler is a staff writer at the Saginaw News. You may reach him at 776-9685.
© 2005 Saginaw News
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