In a Speech Alexi Giannoulias spoke about reversing the flow of the Chicago river so it flowed back into Lake Michigan.
Wow, so we should spend billions upon billions of dollars so we could undo a system that has basically worked for 100 years.
Why would it cost billions of dollars? Well right now deep tunnel does not prevent raw sewage from having to be dumped into the Chicago river, there is no way the rest of the great lakes compact would allow that to happen if there was a chance it would end up in the lake. So you would have to spend billions upgrading deep tunnel (and remember it's been underway for 30 years and it is not done yet).
Even sending treated water into the lake at those volumes would likely require more treatment of water by Chicago resulting in higher costs as well.
Everything else that is based upon the river flowing the 'wrong' way would have to be updated as well.
For what benefit? None to speak of.