The Illinois Department of Natural Resources is investigating the removal of the Carpentersville Dam and has fielded inquiries about eliminating other Fox River dams in North Aurora and Montgomery for public safety and environmental reasons.
The Fox River’s dams were once a source of power for nearby communities, but that is no longer the case for most of the 13 dams on the river. Low-head dams, in particular, cause strong recirculating currents and have led to multiple drownings over the years. And the dams have disrupted the river’s ecosystem, causing excess algae and other environmental issues, experts say.
The IDNR began removing more dams in 2012 when then-Gov. Pat Quinn announced an initiative to eliminate or modify 16 low-head dams throughout the state.
“Our focus is public safety, and in addition to that … is the river connectivity and ecosystem restoration, improvement to the aquatic life of the river,” said Rick Pohlman, division manager at IDNR.
Contractors hired by the IDNR use heavy equipment to break up concrete dams into smaller pieces and remove the debris. The cost can vary depending on the width of the dam or the river.
For example, the Milhurst Dam on the Fox River was partially removed at a cost of $50,000, according to IDNR’s website.
The North Avenue dam in Aurora and the South Batavia dam were both removed from the Fox River during the last 15 years. Plans for removal of the Carpentersville Dam are contingent on getting state funding.
Other dam removals along the Fox River, such as in North Aurora and Montgomery, are only ideas at this point, with no indication whether such plans might move forward.
About half the Fox River is impounded into ponds due to the dams, creating ideal fishing spots but also causing disruptions within the ecosystem.
The Fox River, a tributary of the Illinois River that runs from Colgate, Wis., to Ottawa, Illinois, has the same problems as many bodies of water in the Midwest: an excess of phosphorus and nitrogen. These elements are commonly found in agricultural fertilizers, manure and organic wastes in sewage and industrial run-off, according to the U.S. Geographical Survey.
Phosphorus is essential for plants to thrive, but too much of the element can suffocate aquatic plants and animals.
This excess phosphorus, and the toxic algae blooms it creates, has landed the Fox River on the Illinois Environmental Protection Agency Impaired Waters List since 2004. The list is updated every two years, and the Fox River was named again this year. for its levels of phosphorus, mercury .
“The problem is that we have too many nutrients, nitrogen and phosphorus, the main nutrients that feed plants, and when they get into the river they see aquatic plants in the river, and also algae in the river,” said Cindy Skrukrud, Chair of the Fox River Study Group.
When river flow is slowed by dams, it causes sediment to build on the river’s rocky bottom, which can hurt fish such as walleye and smallmouth bass that need those rocky floors to survive. Rocky bottoms are also a better habitat for shellfish and aquatic insects, which provide sustenance for many fish.
One fish that thrives with a muddy river bottom is carp, an invasive species that has made its way through some rivers in Illinois, including the Fox. Carp out-compete other fish for food and space, and have no natural predators.
“There are a lot of relationships between different species. So that web of life has a lot of rich connections,” said Gary Mechanic, executive director of Friends of the Fox River. “When you put a dam in the river, that’s disrupting and eliminating a lot of that network. It’s almost like having a stroke in your brain.”
The number of dams in the Fox River makes it seem more like a series of lakes than a free-flowing river, Skrukrud said. Those ponds, as well as silt build ups around dams, are ideal for algae growth.
“We have 300,00 people who get their drinking water from the Fox River, and when algae levels get too high in the river, especially during this time of the year when algae grows best on hot summer days, it can cause taste and odor problems in drinking water,” Skrukrud said.
The U.S. Army Corps of Engineers and the IDNR set out to identify the Fox River dams that no longer serve their original purpose, but that study was halted in 2016 due to funding constraints. It’s not clear whether that study might resume.
A possible solution to replace low-head dams are drop structures, which are made up of natural boulders placed in a U-shape instead of stretching straight across the river. Drop structures allow water to flow at all levels, and would be able to preserve any necessary impoundment ponds that the dams had previously created.
Drop structures also allow fish to swim more freely up and down rivers and reduce erosion by better connecting rivers.
“So we design them so that the water passes through, as opposed to being captured in this dangerous hydraulic [roller] that causes the drowning,” said Scott Shipley, president of S2O Design, a company that builds whitewater rafting parks and drop structures.