How MMSD’s Deep Tunnel System Operates During Heavy Rain

04/16/26 11:00:am

To reduce the risk of sewage backing up into basements, the Milwaukee Metropolitan Sewerage District (MMSD) started a combined sewer overflow around 8:30 p.m. on 4-15-26. MMSD's water reclamation facilities and deep tunnel system are at capacity, with more rain in the forecast through Friday, 4/17/26. Our region has had up to 7 inches of rain since Sunday in some areas.

Rainfall in Greater Milwaukee, WI from April 12 to April 16, 2026

MMSD's Deep Tunnel System

Watch the video to learn what happens when MMSD opens and closes the Deep Tunnel “gates” to reduce the risk of basement backups.

Do You Have Standing Water in Your Basement?

If you have standing water in your basement, DO NOT go into the basement! Electricity + Water = Danger.

Wait for the water to drain out of the basement before entering. Or, call a qualified electrician to disconnect the power before you enter a flooded basement.

Call your municipal public works department to report local flooding, and call your homeowners/renters insurance agent.

Please fill out the "Report a Basement" form to help track flooding in our area, which is shared with the 29 municipalities MMSD serves.

Report a Wet Basement

What to do if you have property damage

Report all property damage from flooding, lightning, or extreme wind from the storm to 2-1-1.
- You can call 2-1-1 to report damage over the phone.
- You can fill out a form online at 211wisconsin.communityos.org/damage-report to directly submit a damage report.

The Work Ahead: Protecting Our Region from Future Floods

MMSD's Executive Director, Kevin Shafer, shares the accelerated flood management projects, strengthened infrastructure, and community resilience efforts MMSD is planning to reduce the risk of flooding in our region.

Additional Resources:

IMPORTANT! Water in the Basement can be dangerous

Do not go into a basement with standing water. Electricity + Water = Danger.
Call your municipal public works department to report the problem. If your municipality is unable to help you, call MMSD at (414) 272-5100 or report a wet basement.
Call your homeowners/renters insurance agent.
Wait for the water to drain out of the basement before entering. Or, call a qualified electrician to disconnect the power before you enter a flooded basement.

Heavy rains resulting in dangerous Milwaukee area Rivers

Heavy Rains = Dangerous Rivers

Please be safe around our concrete-lined rivers. STAY OUT of the concrete-lined channel since the water is fast-moving and the concrete is slippery. Call 911 if someone is in danger. We need your help in keeping our community safe.

Text: WATERDROP to 414-296-4422 for Española texto GOTADEAGUA a 414-296-4422

Receive Water Drop Alert text messages when heavy rain threatens the area. When a Water Drop Alert has been issued, a reminder is sent to use less water.

What do you do when an alert is issued?

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