Residents in Lyons and Riverside have seen some big changes in the Des Plaines River. In June of this year, the Hofmann Dam was breached, the last of three low-head dams to recently be removed from the River.
The first Hofmann Dam was installed in the early part of the last century, when it was not uncommon for the entire Des Plaines River to dry up. Adding the dam meant that people could still use the water for recreation, even in dry years.
“Over the years, the area has developed and the Des Plaines no longer dries up. It’s no longer a natural system,” said Jeffrey K. Zuercher, Project Manager with the United States Army Corps of Engineers. “People remember hopping across the Des Plaines River in Riverside because it was so small. We had to tell them that that’s not going to happen anymore, because there’s a lot more input from the watershed, from runoff and from waste water treatment plants.”
In addition to no longer serving its original purpose of creating recreational pools, the dam impeded the migration of fish, impaired water quality and converted riverine habitat to stagnant reservoir habitat. The dam also posed serious safety issues, with several people losing their lives going over the dam.
“The main goal of the project was to restore the river to a natural state of a free-flowing river with no obstructions,” said Zuercher.
The landscape change was immediate. The lake-like pool above the dam now has the appearance of a river – and recent testing suggests that it’s functioning like a river as well. The natural habitat is already beginning to reestablish, both upstream and downstream of the former dam.
Upstream, riffles, runs, and pools have been restored throughout the former pool and at the mouth of Salt Creek. And, recent sampling of the fish population by Illinois Department of Natural Resources found a total of 10 species which were not previously found in the upstream pool including northern pike, rockbass, and blackside darter.
“We also collected channel catfish, a species we have not found anywhere upstream of the dam prior to removal ” according to Steve Pescitelli, DNR Streams Biologist. “This species is highly migratory and is often missing upstream of dams. In that way, finding channel catfish upstream of the former Hofmann Dam is a very good indicator of successful reconnection of the river.” He went on to say that this is a very significant project for DNR and the State of Illinois; removing three dams on an urban stream provides increased recreational opportunities and should also relieve some of the common misconceptions and fears regarding dam removals.
“This is part of a larger trend that’s coming,” said Zuercher. “Illinois has been removing dams over the last few years. It’s a product that will give great benefits to the ecosystem.”
“As the land-owners of much of the property along the Des Plaines River, we’re excited about the results that we’re seeing already,” said Dave Kircher, Chief Landscape Architect for the Forest Preserve District of Cook County. “It’s reassuring to see that the project is doing what it was planned to do, increasing the biodiversity of the river, which is a critical element of our mission. We’re also looking forward to the great recreational fishery downstream not only improving, but actually extending into the river upstream.”
“This whole project has been a long, sometimes difficult process, but has been well worth all the effort and would not have been possible without the cooperation and support of the local communities of Riverside and Lyons, the Forest Preserve District of Cook County, and local organizations, particularly John Mack and the Hofmann Dam River Rats,” said Pescitelli.