Water control project: Going, but on flood hold, Emiquon Preserve

A levee-testing flood builds on the Illinois River for the second time in three years.

On Thursday, Anthony Heddlesten, Peoria Flood Area Engineer for the US Army Corps of Engineers, notified, “If you’re on the Illinois River from Peoria to LaGrange, the current forecast is for a top 5 flood event (Havana is top 3).’’

For Emiquon Preserve, The Nature Conservancy’s floodplain restoration downstream of Peoria, the flooding literally gave pause. It halted, temporarily, construction of a controversial water control structure, which TNC initiated in May.

“Not a good time to be running Caterpillars on levees,’’ said Doug Blodgett, director of river conservation for TNC’s Illinois chapter. “Even when the flood crests, it is going to stay high for a long time.’’

Now there are more more plants and trees to slow the water. That’s different from the great flood of 2013 (pictured right) when there was little vegetation in April to slow the flow.

The original project brought a storm of criticism, because of planned use of public funds and partnership with Corps to connect Emiquon with the Illinois; and because of fears of problems flowing in, particularly from carp.

It was not push back from climate-change deniers. It was legitimate disagreement from people with pedigrees in Illinois outdoors, including Brent Manning and Mike Conlin.

But TNC downsized the project slightly and forged ahead alone, based on science and financial backers willing to fund the $5-6 million.

It is a mix of gravity drainage with two 8 x 7-foot cement culverts and two submersible pumps, which can pull 30,000 gallons per minute each out. If Emiquon was filled, it would take 400 days for pumps to drain and cost $200,000 in electricity. Thus the need for gravity flow help.

“Once in a while, we will have to turn on the pumps,” Blodgett said. “We do not know how often. It used to happen [naturally] every 5 to 7, 10 years. We will mange [by] adaptive management, where we look at what plants and animals are telling us, rather than a prescriptive decision to do it every five years.’’

He compared it to mowing the lawn, where weather and time dictate how often.

“If things are looking OK, we are not drawing down,’’ he said. “But we are not going to fight the river, if it is a flood year. The next year may not be as good, but we can deal with it. In general, there’s more water in spring than in August, but we are not going to fall on sword trying to create that.”

As to carp, Blodgett said, “With a structure, I think we have a lot better chance of dealing with them. I think we are going to have a problem with common carp; and if we do have a problem with bighead and silver carp, this gives us a better way to deal with it.’’

Carp, especially commons, were in. Silvers jumped occasionally. But TNC’s science indicates that black, silver, bighead and grass carp will not take over Emiquon because they need the turbulent waters of rivers to reproduce.

Science will be tested. And there will be a learning curve. That’s why I think this is important.

“We designed a structure that gives us as much flexibility as possibility,’’ Blodgett said. “We can learn from this and share that with [other restoration projects].

“We think collectively it will make a big difference in the Illinois, but it is not going to put it back the way it was.’’