U Researchers Contribute to Hudson River Cleanup

A river running through upstate New York, finally emptying into the New York Harbor, still harbors industrial by-products in the sediment lining its bottom.

The Hudson River is the nation?s largest hazardous waste site.

A cleanup of the same scale is in the works to scrub 40 miles of the polluted waterway.

Don Hayes, a University of Utah associate professor of civil and environmental engineering, is helping the Environmental Protection Agency evaluate the impact that removing contaminated sediment will have on the river?s water quality.

The effort remains controversial even as the EPA puts the final touches on a plan to scrape sediment from the river?s bottom.

General Electric objects heartily to the $460 million plan the EPA is holding it responsible for, according to a statement on its Web site.

For about three decades, the company released PCBs?the primary target of the cleanup?as part of the manufacture of electrical devices.

GE contends that plans to dredge up the contaminated sediment will only increase the concentration of PCBs in the water, slowing the river?s recovery and increasing concentration of the contaminant in fish.

For the EPA?s final plan, Hayes is assessing the amount of sediment and PCBs re released into the water by removal efforts called dredging.

?Our research has shown that dredging can effectively remove contaminated sediment from the waterways,? he said. ?The amount of release is relatively low when dredging is done properly.?

But the success of past dredging projects is still the subject of discussion, he said.

PCBs are oil-like and settle into the sediments, avoiding the water. Efforts to remove them could disturb and re release them into the river.

PCBs collect in the bodies of organisms, becoming more concentrated as they move up the food chain?ultimately making the river?s fish a risky meal.

?One area of debate is how toxic they really are,? Hayes said.

The EPA says PCBs are probable culprits for cancers. Some studies have linked PCBs to developmental and nervous system problems and indicated that they can be passed from mother to child through breast milk.

But GE disagrees. A study it conducted found no indication that PCBs caused diseases in humans.

GE contends that the river is recovering naturally as new sediment is laid down by the water flow, covering the contaminants.

?It does cover PCBs,? Hayes said. ?The question is the time frame?how long it may take for that to happen.?

The EPA felt this natural process was too slow.

PCBs do break down?but slowly. Decades after release into the river, they still reside in its sediment.

Though his involvement in the Hudson River project is limited to small-scale assessments, Hayes? experience with other cleanups has shown him that dredging usually has less impact than leaving the sediment in place, he said.

As part of the assessment, Hayes is looking at different scenarios for dredging. The goal is to make sure that even the worst-case scenario falls within the EPA?s standards.

A bucket dredge scoops the sediment from the river bottom. Meanwhile, a hydraulic dredge sucks it up. But both release about the same amount of sediment back into the water, he said.

Tom Borrowman, a master?s student in civil and environmental engineering, is working to model how sediment is released from a bucket dredge and where it goes.

A bucket dredge uses a fairly simple scooping mechanism. But a global positioning system and sonar maps at the bottom can make bucket dredging highly precise.

?It?s a combination of low- and high-tech,? Borrowman said.

After an area of the Hudson is dredged, the EPA plans to deposit new sediment to cover any contaminants left behind.

The 2.65 million cubic yards of sediment to be dredged will probably end up in landfills.

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