Summer Tests To Find River Cleanup Solutions Scientists Try To Balance Cost Against Environmental Concerns

Along the clover-covered banks of the South Fork of the Coeur d’Alene River, small flags mark the site of a cleanup contest about to begin.

The 50-by-50-foot plots between the dredge piles and the river are test sites for entrepreneurs, engineers and scientists who have proposed various methods of cleaning up decades of mine waste.

After a summer of field testing, University of Idaho scientists and other experts will decide whose method is best based on performance, cost, long-term stability and environmental risk.

“We are looking at it from the industry’s viewpoint of limited financial resources and the environmental viewpoint of, ‘We need to do something and not just argue about it,”’ said Idaho Water Resources Institute Director Roy Mink.

The request for proposals already has drawn broad interest, from local Cataldo ranchers banking on a combination of phosphates and red top grass, to a Pasadena, Calif., company specializing in chemical “soil washing.”

“We are letting people’s ambition drive the process,” UI soil scientist Steve McGheehan said. “It gives us different ideas, different approaches and a spectrum of technologies - some low-tech, some high-tech.”

UI scientists believe cleanup efforts on the South Fork should be different from those at more polluted areas closer to the Superfund site. Here, contaminated soil is mixed with healthy organic sediment washed down from the North Fork. Ideally, cleanup efforts wouldn’t disturb the “good” sediment helping to revegetate the area.

The UI is coordinating the $60,000 competitive testing project for the Environmental Protection Agency. Interested parties must fund their own testing.

Moscow scientists also are working on adjacent projects funded by the state and the mining industry.

UI scientists believe heavy metals contaminate the river from ground water draining through mine tailings and through streambank erosion from flooding, the wave action of boats and personal watercraft and fluctuating water levels at the Post Falls dam.

Researchers are working on two projects aimed at solving these problems: streambank stabilization and an underground iron barrier intended to filter metals from the ground water.

To keep the bank from sloughing, a section of the river’s edge has been sloped and planted with willow trees and grasses. The bank is further supported by wooden pilings lined with biodegradable fiber matting that is rolled up and used for erosion control.

For the ground water problem, researchers constructed an iron barrier and an 8-foot-deep, several yards wide trench that is filled with iron filings. The hope is that the iron will chemically filter the lead, zinc and cadmium from the water as it flows toward the river.

A small well above the barrier tests the water before it arrives. A well below will show if the ground water is cleaner after passing through the “iron curtain.”

It isn’t known at what point the barrier will become clogged or how it will perform during flood stages, Williams said.

But researchers are hopeful the new technologies are aiding cleanup efforts.

“Strategies utilized so far in the Coeur d’Alene Basin have relied largely on removal, dredging or bulldozing,” Williams said. “This is taking a different approach for a different geographical area.”