Dirty water released into Lake Michigan to reduce flooding

Dirty water containing a mixture of rain and raw sewage was released into Lake Michigan early Thursday following a deluge of overnight rain that overwhelmed area sewer systems.

The filthy water entered the lake in north suburban Wilmette when the gates separating the North Shore Channel from Lake Michigan were opened and the flow of the channel — which is connected to the Chicago River’s North Branch — was reversed.

The gates were open from 2:08 a.m. to 6 a.m., Pat Thomas, a spokesman for the Metropolitan Water Reclamation District, which controls the gates, said in an email.

“Approximately 2.71 inches of rain fell in a short amount of time late last night and early this morning at the North Branch Pumping Station, with the majority falling between 11 p.m. and 1:30 a.m. This rainfall is in addition to the recent wet weather events we have experienced over the last few weeks,” Thomas said.

Reversing the flow to send water into the lake is a last-resort measure taken to protect homes and buildings from flooding.

The amount of liquid, including raw sewage, that was sent into the lake cannot yet be estimated, Thomas said.

It was the first time since 2017 that the MWRD has released untreated water into the lake.