On August 9–10, 2025, severe flash flooding impacted southeastern Wisconsin, including Wauwatosa and the Milwaukee County Grounds. Cemetery 3, in particular, was inundated by several feet of sewage-contaminated floodwater for approximately 24 hours.
The flooding caused slumping throughout the cemetery, where the collapse of weakened coffins disturbed the ground. Most graves at Cemetery 3 are unmarked, but in some locations the flooding revealed a few headstones that had been obscured over time.
Even a single severe storm can alter the landscape, disturb burials, and expose what has long rested beneath the surface, demonstrating the cemetery’s physical vulnerability to future extreme weather. In keeping with our mission to honor and preserve the dignity of those interred at the Milwaukee County Grounds Cemeteries, the Descendant Community is documenting these physical impacts. Understanding how the flooding affected both the landscape and the historic gravesites is essential for guiding restoration, protection, and long-term stewardship efforts.
Cemetery 3 is located near the Menomonee River and Underwood Creek, as well as sewerage and floodwater management facilities operated by the Milwaukee Metropolitan Sewerage District (MMSD) and Milwaukee County. Members of the Descendant Community met with MMSD representatives to understand how the flooding occurred. While MMSD began studying the potential impacts of 1000-year flood events in 2023, its infrastructure remains designed for 100-year floods. During the August 2025 event, sewerage facilities related to the Menomonee River watershed were overwhelmed, resulting in sewage flow onto Cemetery 3 and into the Menomonee River.
According to the National Weather Service, multiple rounds of extremely heavy rain fell across eastern Waukesha County and northern and western Milwaukee County between the evening of August 9th and early morning of August 10th. Between 10–13 inches (25–33 cm) of rain fell within several hours, causing significant flash flooding across Wauwatosa, West Allis, Menomonee Falls, Elm Grove, and New Berlin. The Milwaukee, Fox, Menomonee, and Root Rivers all rose to flood stage, with record levels observed along the Milwaukee River.
Explanation of the Flooding
During the event, MMSD experienced a sewage overflow at its Menomonee River facility on the County Grounds. Water entered the Northwest Side Relief Sewer (NWSRS) system from the north and moved southward, following the natural grade toward Cemetery 3. Similar to the Deep Tunnel system, this system is designed to temporarily store stormwater until it can be safely treated. It was, however, constructed to withstand a 100-year flood—not the extraordinary 1000-year event that occurred.
The pressure within the system was so extreme that it displaced two sewer grates, each weighing approxing 28 tons, causing uncontrolled surface flow toward low-lying areas, including the cemetery and the Menomonee River.
Other Nearby Water Management Facilities
To the west of Cemetery 3, large basins help divert excess flow from Underwood Creek to reduce the strain on the Menomonee River. The Underwood Creek watershed experienced a 100-year flood event and these basins performed within design parameters during the event, filling to roughly 50 percent of capacity. The water quality basin to the east of Cemetery 3 also functioned as expected, improving water quality before release.
Next Steps and How You Can Help
Portions of Cemetery 3 are within the official FEMA-designated floodplain. While flood maps are being updated to account for MMSD’s projects in the Menomonee River watershed, MMSD prioritizes buildings in its flood-management plans, and its projects do not materially impact Cemetery 3.
The Descendant Community continues to work with Milwaukee County and MMSD to advocate for infrastructure improvements that balance public health, historic preservation, and protection of these vulnerable sites. Preserving the resting place of those buried at the County Grounds is central to our mission. As climate variability increases the likelihood of extreme weather, this work has never been more urgent.
You can play a vital role in these efforts. Whether through volunteering, donating, or helping share our mission, your support allows us to document burials, maintain and restore affected areas, and protect the dignity of those interred. Volunteers assist with research, cemetery care, and community outreach, and training is provided to ensure meaningful participation. Donations help fund genealogical research and ongoing preservation work, tools essential to honoring lives that were once marginalized and largely unmarked. Contact us to learn more.