Milwaukee’s “Combined Sewer” Area

Part of Milwaukee’s water drains into the Combined Sewer Area, where stormwater (from rain falling on rooftops, streets, yards) and wastewater (what we flush down the toilet and what industries send down sewer pipes) are both collected and treated together. Both stormwater and wastewater flow to the sewage treatment plant.

The Combined Area is the older, central area of the city because it was constructed first. As the city and suburbs developed outward, a Separated Sewer Area was added. In the Separated Sewer Area, wastewater and stormwater are designed to flow through different pipe systems. Stormwater drains right into rivers. Wastewater flows to the sewage treatment plant.

This map shows the Combined Sewer Area in red. The City of Milwaukee boundary is also shown in light gray for reference. When heavy rains fall over the Combined Sewer Area, they can overwhelm the system and lead to Combined Sewer Overflows, where wastewater and stormwater are discharged untreated into local waterways. That’s why every gallon of water captured in that area makes a difference to keep our waters clean.

We invite you to explore the web map below and through the Milwaukee Community Map in Google Earth, where you can cross this basemap with other interactive story layers.