Milwaukee Sewers Overflowed 750 Million Gallons During September Rain

MILWAUKEE, WI — Over 750 million gallons of untreated water from combined sewers were discharged into Milwaukee-area waterways amid record rain in September, according to the Milwaukee Metropolitan Sewerage District.

Milwaukee saw around 4.78 inches of rain by the evening of Sept. 11 and into the morning the rain continued, leaving flooding in certain areas. Rainfall reached 7.65 inches in the Oak Creek area, 5.55 inches near West Allis and 6.7 inches near Mequon, according to MMSD.

To counteract possible basement flooding amid the heavy rain, MMSD initiated the discharge the evening of Sept. 11. By the next morning, Interstate 94 was blocked in Waukesha by flood waters and officials were asking people to use less water to reduce the load on the sewer system.

RELATED: Flooding Closes Interstate 94 In Waukesha; Milwaukee Sewer Overflows

Milwaukee's sewers in many parts are combined with stormwater sewers, meaning surges in rain can cause such overflows. Just one inch of rain on MMSD's service area equates to 7.1 billion gallons of water, the agency says.

Overall, combined sewers overflowed by 771 million gallons, MMSD said. Separate sewer overflows amounted to 4.93 million gallons.

• About 125,000 gallons were discharged for just over 3 hours into Wilson Park Creek near Howell and Grange Avenues.
• About 1.6 million gallons were discharged for just under 3 hours into the Kinnickinnic River near 35th Street and Manitoba.
• About 295,000 gallons were discharged into Lake Michigan near Kinnikinic Avenue and St Francis.
• About 2.9 million gallons were discharged into the Milwaukee River near River road and Green Tree Road.
• Sewer overflows also happened in local systems in Brookfield, Cudahy, Elm Grove and Menomonee Falls.

Amid the heavy rain on Sept. 11 and Sept. 12, flooding was also reported in Greenfield. Police logs show that a car stalled in flood waters and had to be towed out of mud near Brookside Drive and Upham Avenue that morning around 11 a.m.