As Milwaukee deals with an onslaught of rain this week, the Milwaukee Metropolitan Sewerage District (MMSD) is working in overdrive.
It’s releasing some untreated wastewater into area waterways, because the treatment plant can’t keep up with the volume. To find out more, WUWM spoke with Bill Graffin, public information manager with MMSD, on Thursday.
Graffin told WUWM that the district had to release untreated wastewater, because as of midday Thursday, there were at least three areas of the community that had more than six inches of rain since Sunday. Many others had five inches of rain.
"We are having a combined sewer overflow right now," says Graffin. "And that is multiple overflow points. They're all located in the river system, for the most part, in the Milwaukee, the Menomonee, and Kinnickinnic [Rivers]. Of course, all those rivers flow to Lake Michigan. There are only one or two direct overflow points to Lake Michigan. Those overflow points are relief valves in the sewer system."
"And when you get too much water into the sewer system, it can start backing up in the sewer and into people's homes and businesses," he says. "That's the highest priority we have during a storm — is trying to prevent that from happening. The only way to do it is with the relief valve that lets excess water out of that sewer and into the nearest river untreated."
This conversation has been edited for length and clarity.
WUWM's Maayan Silver: When you do have to release untreated sewage into the lake, how long does it take the natural world even that all out?
Graffin: I know anecdotally from talking with scientists in the past that they, you know, talk about Lake Michigan as an extremely hostile environment for bacteria to live. So in many cases, bacteria can only survive three to 10 days, is what I've heard. Again, that's just anecdotal from talking to scientists over the years in doing this job.
MMSD does capture and treat, what is it, 98.4% of the sewage?
Yeah, out of every drop of water that has gotten into our system, the regional system, since 1994, we've captured and cleaned 98.5% of everything.
The Sewerage District has issued a water drop alert. What can people do in that scenario to prevent the kind of overflows that you're talking about?
Yeah, water drop alert is a pretty simple concept. Just try to use less water. We're not saying don't use water. We're not saying, you know, don't take a shower or don't flush the toilet. We're saying if you can hold off on doing the dishes until tomorrow, till the storm passes and the systems, you know, had a chance to recover a little bit. And just, some of those ways to try and use a little bit less water — that helps keep water out of the sewers.
What's the system's ability to keep up with the volume of rain this week? We still have more rain in the forecast.
Yeah, it's pretty full right now. The tunnel's at 91% capacity. South Shore is at 83% capacity and Jones Island is at 100% right now.
What does that mean for handling all this? What are you expecting?
We're cleaning and storing as much as we can. But again, there are overflows going on, those relief valves out in the sewer system to get excess water out into the rivers untreated — that helps keep it out of people's basements.
