Posted by Hal Dardick and Joel Hood at 5:16 p.m.; updated at 5:26 p.m.

Mayor Richard Daley today floated the idea of undoing Chicago's greatest engineering feat --- reversing the flow of the Chicago River away from Lake Michigan --- to improve the ecology of the Great Lakes.

“I said boy that’s a great project,” Daley told the Tribune, recalling a conversation he had last week with his brother while at a beach along Lake Michigan. “Instead of diverting all that water, maybe we should reverse it (to flow into the lake).”

“I said that’s a great project, we have to start thinking about it now, and of course go to the business community and set up a committee and work with Water Reclamation District and others and Army Corps of Engineers,” Daley added.”That could be the salvation maybe of the Great Lakes.”

More than 100 years ago, city leaders completed decades of work that reversed the river’s flow, so untreated waste did not flow into Lake Michigan, the city’s drinking water source. The reversal also linked Chicago to the nation’s shipping waterways.



But the project also diverted a significant amount of water from Lake Michigan, and created a way for invasive species, like Asian Carp, to get from the Mississippi River to the Great Lakes ecosystem. So Daley, who once headed up an international coalition to protect the Great Lakes, started thinking about re-reversing the river’s flow, the mayor said today an interview a few days after announcing he would not seek a record seventh term.

Daley went on to say that reversing the river wouldn’t require that the Metropolitan Water Reclamation District to reverse its long-standing opposition to treating sewage before it’s dumped in the river.“I don’t think so,” he said, adding that the massive, ongoing Deep Tunnel project designed to prevent stormwater overflow from contaminating the city’s waterways would have to progress much further before anything could be done. “if we get another tunnel built, which I think will be possible and everybody will support that, it would be possible in the next 20 years that we could have this, and that would really help ecology.”

Daley said he’s considering putting his latest ambitious plan into action, even though his decades in office are winding down. “I hope to put a committee together,” he said.

City leaders pulled off one of the great engineering feats in world history by artificially reversing the flow of the Chicago River and diverting sewage water away from in Lake Michigan. They accomplished this by digging a channel through a small ridge on the western edge of the city, using gravity and the landscape's natural plane to carry water backwards toward the Illinois and Mississippi rivers. In the process, engineers built an entirely new waterway system that included the Chicago Sanitary and Ship Canal and would become a vital and lucrative corridor for boats and cargo ships.



The move angered other Great Lakes states who feared Chicago had disrupted the natural ecosystem of the region and would lower lake levels by diverting too much water the other direction. Subsequent lawsuits limited how much water could be diverted, but Chicago's waterway system remained intact.



Some environmentalists and Great Lakes advocates have long lobbied Chicago to redesign its system to return the Chicago River to its original flow. Though the cost may be high, sophisticated filtration systems and water treatments plants could remove the risk of diverting sewage back into Lake Michigan, the city's primary source of drinking water.



With fears rising about the introduction of Asian carp and other invasive species into the Great Lakes, U.S. Sen. Dick Durbin, D-Ill., asked Congress in June to commission a study looking at re-engineering the region's waterway system to allow for the passage of boats an ships but not invasive species. The study would also look at the feasibility of restoring the Chicago River to its original direction.



Once one of America's most polluted stretches of water, the U.S. Environmental Protection Agency has since introduced the idea of cleaning the Chicago River so that it may be one day used for swimming. Such an undertaking would likely require spending millions on new sewage treatment technologies, but it is perhaps the next logical step as the city remakes the winding river into a second waterfront.