Fence goes up to keep Asian carp out of Chicago canal

The latest weapon in the fight against Asian carp doesn't look much like a weapon at all: It's a 13-mile concrete and steel mesh fence that splits the narrow divide between the Des Plaines River and the Chicago Sanitary and Ship Canal as they meander through the southwest suburbs.

The $7 million project, paid for from the federal Great Lakes Restoration Fund, is a relatively low-tech solution to keep the dreaded carp from breaching the low-lying strip of land between the river and the shipping canal during heavy rains.

It may look simple, but state and federal officials say this fence in Illinois and a similar one recently erected in Indiana are vital to the national effort to keep the invasive species out of the Great Lakes.

"This was absolutely critical," said John Rogner, assistant director of the Illinois Department of Natural Resources. "We knew that during high flood events that Asian carp, if they're in the river, could easily span the gap and get into the Sanitary and Ship Canal."

A native of China with no known predators in the U.S., Asian carp have overwhelmed native fish populations by out-competing them for food in a 30-year migration up the Mississippi and Illinois rivers. Many fear the carp could soon enter the Great Lakes, jeopardizing its estimated $7 billion a year commercial and recreational fishing industry.

With a bill in Congress and a verdict soon expected in a divisive court case aimed at closing Chicago-area shipping locks to halt the northward migration of the fish, officials say the fence is a reminder that the daily battle against carp continues unabated.

"We just keep using every tool that we have to try and make sure they don't come any closer and to eradicate them eventually," said U.S. Rep. Judy Biggert, R-Ill.

Though it's unclear how many Asian carp exist in the Des Plaines River, the winding tributary connects to the Illinois River where Asian carp are known to be abundant. The fence is designed to work in partnership with a more sophisticated carp weapon -- the underwater electrical barriers installed a decade ago in the shipping canal near Romeoville.

The fence is only 3 feet tall in some spots along the route, but rises to 8 feet in areas prone to deeper flooding. Though the fence looks like something you might see around a construction site, officials say it is actually a product of sophisticated engineering. Its mesh wiring is designed to allow passage of water to relieve flooding but is small enough to block out all but the smallest fish and eggs.

The fence begins just north of the electrical barriers and follows along the Centennial biking trail toward Chicago. The gap between the Des Plaines and the shipping canal is so narrow outside of Joliet, just a couple of hundred feet in some spots, that fish could easily slip between the river and the canal, officials said, a scenario that could render the electrical barriers useless.

"It was obvious with floods in the last couple of years that there are several points around the Great Lakes where floodwaters could possibly allow Asian carp to move into the Great Lakes," said John Goss, an Indiana wildlife expert who was recently tapped to coordinate the federal government's Asian carp plan.

Goss, the White House's "carp czar," was on hand Friday when the U.S. Army Corps of Engineers unveiled the new carp fencing at a brief ceremony under the Interstate 355 overpass near Lemont. Goss said the government's plan calls for a series of similarly designed fences in vulnerable areas around the Great Lakes.

"The long-term challenge is how are we going to reduce those populations in rivers so that they don't have a negative impact on our native fish," Goss said. "Hopefully, this will at least slow them down."

(c) 2010, Chicago Tribune.
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