In the 1870s, the Chicago River was dumping commercial and industrial waste into Lake Michigan, which quickly became a threat to the public’s health. With the completion of the final major engineering project in 1928, the river’s direction was reversed. Today, it flows away from the lake.

Recently, Mayor Richard M. Daley said while on the lakefront with his brother, he thought about re-reversing the flow of the Chicago River. Returning the river to its natural flow could help clean up the river as well as divert invasive species such as the Asian carp, according to Friends of the Chicago River.

“I said, ‘Boy, that’s a great project,’” Daley told the Tribune. “Instead of diverting all that water, maybe we should reverse it. That could be the salvation of the Great Lakes.”

Dick Lanyon, executive director of the Metropolitan Water Reclamation District of Greater Chicago, does not think the project is feasible or likely because of engineering problems and cost. The city has not approached the district to begin work on the project.

“The rivers, both the Chicago and the Calumet, were reversed with good purpose,” Lanyon said. “It’s to provide drainage for the city so it does not go back into Lake Michigan and pollute our water source.”

Dumping and pollution in Lake Michigan currently comes from the surrounding states of Indiana, Michigan and Wisconsin, according to Lanyon.

The Prairie Rivers Network, a non-profit focused on river protection, conservation, and restoration, supports the idea.

“The waterway is a supportive superhighway for invasive species,” said Glynnis Collins, executive director of the network. “A lot of smart people are working on it. If we could figure out how to do it a hundred years ago, surely we can figure out how to undo it, and to undo it in a way that could solve other problems.”

The current system in place includes various man-made canals, dug on a grade to use gravity to reverse the flow, as well as a deep tunnel to divert the storm water. Flooding is a major concern should the system be reversed back to its natural flow.

“If the river were to flow into the lake, it would be privy to the fluctuations of the lake,” said Kim Rice, outreach program coordinator for the Friends of the Chicago River group. “If the river is at a high point and we get rain, there is nowhere for the overflow to go except into streets and basements and all the places we don’t want it.”

Rice thinks the idea of undoing the reversal is possible and could have many important benefits, including alleviating the state’s ongoing problem with Asian carp. The invasive species damages the ecosystem and food web, as well as cause physical harm to people on the Illinois River, as these fish jump out of the water.

“The hydrological separation would curb the invasive species,” Rice said. “You would have to create an actual, physical divide [between canals].”

In order to stop the flow and switch directions, Rice said there would have to be a creation of new locks and the existing ones would be opened. The current locks regulate the water flowing in from the lake.

The other major benefit would be an improvement of the river’s water quality because it would be forced to meet Lake Michigan’s higher standard of cleanliness of wastewater dumped into the lake.

“They would have to make the river much closer to pristine,” Rice said. “A cleaner waterway would draw more people to it. The key would be to not disrupt the commercial and industrial traffic.”

However, according to Lanyon, the river does not just affect the Chicago River, it affects its connections—another reason he does not support the change.

“Whatever we put into the south end of Lake Michigan stays there awhile,” Lanyon said. “The fact that we’re drawing water out of Lake Michigan is a benefit now because it counterbalances the in-flow from all these neighboring states.”

Lanyon said parts of the river could become stagnant, especially during dry weather because the river would not be flowing out the mouth near Lockport.

Any major project requires money, and cost was a concern for all of the groups.

“We’re talking about billions,” Lanyon said. “There’s the extra cost of treatment and overflows.”

He said there would be more detailed estimates in upcoming months  as a change this big is hard to estimate.

“If we just think outside the box and look at a totally new way of doing things, I think we can benefit the rivers, the lakes, the citizens and the businesses in the Chicago area,” Collins said.

Rice said the feasibility is there, and a cost benefit study would be conducted before any work begins.

Regardless, Rice said, “This is Chicago, we can do anything.”