Thursday, May 19, 2005

Illinois River Sediment: Two Environmental Problems, One Highly Innovative Solution

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This is a story of two problems.

Problem number one is the buildup of sediment in parts of the Illinois River system over the past hundred years. In that time some sixty thousand acres of side channels and backwater lakes have become so shallow that they’ve lost almost all value for fish and wildlife, or recreation. These areas were formerly six to eight feet deep, but now average less than eighteen inches, thanks to accumulated sediment.

Problem number two: large expanses of land that have been degraded by various past uses—including strip mines, former industrial sites, and landfills—that need to be covered with fertile soil before they can again be useful for people or wildlife.

Enter John Marlin, senior scientist at the Waste Management Research Center, a non-regulatory service organization affiliated with the University of Illinois, and a division of the Illinois Department of Natural Resources. In cooperation with numerous others, including Illinois Lieutenant Governor Pat Quinn, Congressman Ray LaHood, the U.S. Army Corps of Engineers, Illinois EPA, and the City of Chicago, Marlin has pursued a plan that addresses both issues. His idea--move the soil from where it’s a problem to where it’s a solution, transporting it on the river in barges.

Of course there were questions to be answered before anyone began loading soil. Chief among these was whether Illinois River sediment was suitable as a substitute for topsoil from other sources. Greenhouse experiments and field studies conducted by UIUC soil scientist Robert Darmody and colleagues confirmed that sediment excavated from the river was highly fertile, and that it possessed physical properties similar to those of native Illinois topsoil. These findings are not surprising since most of the sediment in Illinois waterways is soil that has eroded from agricultural fields.

Other studies determined that levels of chemical contaminants in the river sediment were acceptable for the types of redevelopment projects that Marlin and others envisioned.

After smaller trials in 2002 and 2003, the idea of using excavated sediment to redevelop degraded landscapes, or mud-to-parks, as it came to be called, was tested on a larger scale last summer. More than a hundred thousand tons of sediment was dredged from the Illinois River at Peoria, loaded onto barges, and shipped up upriver to a former U.S. Steel facility on Chicago’s south side, a slag-covered site on the Lake Michigan shore devoid of topsoil. There the excavated sediment was unloaded and spread atop the slag, covering seventeen acres to a depth of two to three feet. The site was later planted with native grasses and should begin to look like a natural area by summer 2005.

As of now, prospects for the future of the mud-to-parks idea look quite good. There’s no shortage of sediment to be removed from the Illinois River, and there are sites that material could reach by barge all the way from northwestern Indiana to New Orleans.