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Flooding impact: How diluted raw sewage gets into metro Detroit waterways

Posted at 1:40 PM, Jun 29, 2021
and last updated 2022-03-17 20:26:11-04

(WXYZ) — The fast flowing water in the Lower River Rouge is murkier than usual this week, just days after devastating rains flooded metro Detroit.


“This is an unusual event but high water is not unusual to the Rouge," said Sally Petrella, Monitoring Manager with Friends of the Rouge. "With climate change, we’re seeing it a lot more.”

Petrella works for the nonprofit Friends of the Rouge and has spent two decades monitoring the river's ecosystem. During the storm, the river crested well over the river banks, flooding Ford Field Park in Dearborn, damaging the river as it receded.

“That causes a lot of erosion and then you get a lot of sediment in the water, which makes it very difficult for the fish and the bugs that they eat to survive in the river,” Petrella said.

The heavy rain also flooded homes and highways across metro Detroit leading by a backed up sewer system. As numerous pumping stations across the region failed, all that unfiltered sewage was sent somewhere else.

“In an event like this, you have got millions of gallons of diluted raw sewage going into the river,” Petrella said.

That diluted sewage can raise e.Coli and bacteria levels in the water, which flows directly into the Detroit River. Mary Bohling with MSU Extension and Michigan Sea Grant says part of the problem is decaying infrastructure.

“In metro Detroit here, a lot of our sewers are what we call 'combined sewers' where our sanitary system and our non sanitary system, the storm water, goes into the wastewater treatment facility,” Bohling said.

During heavy rain events, that combined system leads to problems.

“When we get a little bit of rain it’s not so bad, because all that water goes into the wastewater treatment facilities," Bohling said. "But when we get inundated and we get several inches of rain, especially in a short period of time, eventually the wastewater treatment facility gets to the point where they have to release that water semi treated but mostly untreated out into our lakes and streams.”

The good news is that our ecosystem will naturally bounce back, bringing e. Coli levels down in a matter of days. However a week-long rain event, like is expected, will keep those levels high.

"When you have several days of rain, especially significant rain like we’re seeing here, it does cause a lot more concern," Bohling said. "It takes longer for the environment to bounce back.”

This is the second major storm to cause flooding in the last 10 years, and those who work in our local waterways are hoping this time serves as a wake up call, to increase investment to keep our rivers clean.

Dearborn recently announced that their sewer separation initiative, mandated by the federal government, will be complete by November of this year. The Combined Sewer Overflow project, according to the city, aims to separate storm water and sanitary water, helping to reduce the amount of pollution that goes into the Rouge River. Officials say the project was not meant to increase the sewer system's capacity to prevent flooding. The City of Dearborn says during the storm this weekend, Dearborn received over seven and a half inches of rain, the largest amount in the area.

“Infrastructure,"Petrella said when asked what was needed. "We need to fund more projects to deal with our sewers so that we’re not diverting the sewage into our rivers in a big storm.”

"It’s a combination of things," Bohling said. "People disconnecting their downspouts, installing rain gardens... more green infrastructure to capture the storm water before it gets into the system.”

County Health Departments monitor E. coli levels at beaches. Just Tuesday, Macomb County closed Memorial Park Beach due to high bacteria counts. You can find all the beaches currently closed by checking out the Michigan Beachguard at