CHICAGO (WLS) -- As Chicago braces for more rain, this is why the city decided to reverse the flow of the Chicago River Sunday to prevent major downtown flooding.
Wednesday, staff at the Metropolitan Water Reclamation District of Greater Chicago was bracing for more rain.
"When we have a severe weather event coming it's a little stressful, a little nerve-wracking," said Assistant Director of Maintenance and Operations Ed Staudacher.
ABC7 visited the MWRD's Waterway Control Center on one of those stressful days, as engineers try to make room in the system for today's anticipated storm.
Heavy rain over the weekend caused MWRD to make a rare and hazardous decision to allow untreated floodwater from the Chicago River into Lake Michigan to relieve pressure on the system.
As it was, some residents still experienced flooding in their homes and neighborhoods.
Staudacher explained they had to wait until the river level was higher than the lake to make the call; opening too earlier, he said, would cause catastrophic flooding with a tsunami effect.
"The lake is the source of our drinking water, so you want to protect that drinking water at all costs," he said. "Then you turn to protecting the public from flooding, then we have to do what we do to protect them."
"We are issuing an overflow action day alert, basically our McCook Reservoir and tunnel are still full from the last extreme rain event," said MWRD president Kari Steele.
Steele asked all Chicagoans to get in the habit of conserving water use when there is heavy rain in the forecast.
"Hold off on running that dishwasher or doing laundry, take shorter showers, conserve water to make sure we are able to capture as much storm water we as we can to keep it out of those unwanted places," she said. "Basically, we are asking everyone to be a good neighbor."
Overflow action day goes until the storm system passes.