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In-depth look at deep tunnel: Overflows after flooding create health concerns in Milwaukee

Milwaukee-metro area residents: Try not to do your dishes, laundry, or take long showers the next few days.
Posted at 7:59 PM, Sep 12, 2022

MILWAUKEE -- The torrential rain this weekend has wreaked havoc on our water treatment systems.

As of 11:15 p.m. Sunday, leaders with the Milwaukee Metropolitan Sewerage District say the overflow of dirty water from the excess rain began to release into our area rivers, and flow into Lake Michigan.

TMJ4 News went in-depth to learn how the Milwaukee Metropolitan Sewerage District's 19-mile-long deep tunnel works to prevent this from happening as often, and why it became overwhelmed this time.


Bill Graffin with MMSD points out that three decades ago, our old system would average about 50 to 60 overflow events a year. That is when dirty untreated water is released into Lake Michigan, which includes "shower water, it's what you use to wash your dishes the sink."

And yes, some of the water during these overflow events includes what you are flushing down the toilet.

But thanks to our deep tunnel, Graffin says, "We're now down to one or two overflows a year." In fact, this was the only overflow event to take place so far this year.

The deep tunnel is more than 19 miles long. Graffin says to think of it like a big bathtub about 300 feet underground. It can hold up to 521 million gallons of water, which provides relief when our water treatment plants become overwhelmed by weather events like what we just experienced.

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But because of our unrelenting rain from this weekend, our deep tunnel was about 90 percent full as of Monday morning. The more water people are using in the Milwaukee area today is exacerbating the problem.

Graffin explained further, "We have to reserve room in the tunnel for separate sewer flow that's going to come at us sometimes not until 12 hours after the storm hits."

Starting at about 11:15 p.m. Sunday night, the overflow of dirty water began to overflow into our area rivers, which feed into Lake Michigan.

Graffin says there is no question this will result in higher levels of bacteria in Lake Michigan, which could lead to beach closures. We asked exactly how much untreated water could be going into Lake Michigan right now. He said at this point, "That's a really hard question to answer," but reiterated that, "90 percent or more [of this overflow] is rainwater and groundwater."

So with all of this excess water, leaders say they are stuck between a rock and a hard place. It's either letting the water back up into our homes and businesses or releasing some of the dirty water into our rivers which leads to our beautiful Lake Michigan. This event may serve as a reminder that we all need to do our part.

Graffiin's ask for Milwaukee-metro area residents for the next few days is to, "Use less water if you can."

What do you do when an alert is issued? According to MMSD:

  • Hold off on washing dishes and laundry
  • Take a shorter shower 
  • Empty your rain barrel

Erin Povak saw the sewerage district's water drop alert on her phone this morning, which texted her to "Please Use Less Water to Help Reduce Sewer Overflows."


You can visit MMSD's website to sign up for the same text alert to be sent on your smartphone.

As a program director at the non-profit conservation organization called Sweet Water, Povak shares some ways you can help protect our lake year-round.

"One thing that I have on my property is a rain barrel, anda rain garden and that really does help slow the flow of water," said Povak.

She also has adopted two storm drains to prevent flooding. You can do the same on Sweet Water's website.

The City of Milwaukee has also invested in green alleyways, to help absorb the rainfall, and prevent polluted overflow from going into our storm drains.

Graffin believes all of this makes a huge difference, "Oh absolutely. If we manage that water where it falls we're going to have fewer problems."

At the end of the day, it may be up to all of us to keep our precious water resources safe. Check out MMSD's website to learn even more ways to keep our waters safe.

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