Dirty water released into Lake Michigan to reduce flooding

Millions of gallons of untreated water were released into Lake Michigan over the weekend to ease flooding concerns along Chicago-area rivers swollen by heavy storms.

The water, including raw sewage, flowed freely into the lake — the source of Chicago’s drinking water — for nearly five and half hours from 11:05 p.m. Saturday to 4:30 a.m. Sunday, according to David St. Pierre, executive Director of the Metropolitan Water Reclamation District of Greater Chicago.

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.

Water levels on the river had climbed to three feet above that of the lake — the threshold at which the gates are opened.

The step, a last resort, was taken “in order to protect homes and buildings,” St. Pierre said Monday.

National Weather Service Meteorologist Matt Friedlein said Monday afternoon that the Des Plaines and DuPage Rivers, as well as the North Branch of the Chicago River, were all cresting or expected to crest in the next 12 hours, creating minor flooding around low-lying grassy areas near the banks of the rivers. “Usually there aren’t many structures or roads there,” he said.

Campground Road, which runs parallel to the Des Plaines River, was closed and under water, said Des Plaines Fire Chief Alan Wax. Other than that, he said Monday, “we’re really doing OK here.”

Sending unsanitary water into the lake is an unfortunate scenario that happens about once a year — a rate of occurrence that will hopefully decrease when a new reservoir near southwest suburban McCook, part of the Deep Tunnel Project, becomes operational in December.

Estimates of how much untreated water flowed into the lake over the weekend — and how much raw sewage overflow the water contained — will not be available for several days, St. Pierre said.

An average of three inches of rain fell during storms that lasted from Saturday afternoon until the wee hours of Monday morning, St. Pierre said.

“We’re at this 24/7,” he said of monitoring the area water levels.