Flint, Michigan – City officials in Flint reported that a release of wet-weather wastewater occurred at the city’s Water Pollution Control Facility early on the morning of March 7, 2026, after heavy inflow into the sewer system overwhelmed treatment capacity at the plant.
According to the Utilities Department’s Water Pollution Control Division, the discharge took place at approximately 8:20 a.m. and consisted of a combination of stormwater and partially treated sewage from the wastewater treatment facility.
The release happened after rainwater and storm runoff entering the sewer system created volumes too large for the plant to fully process through its standard secondary treatment system.
The wastewater treatment plant is equipped with a Retention and Treatment Basin designed to temporarily store excess flows during major wet-weather events. This system allows the facility to hold additional wastewater until it can be properly treated.
However, officials said that when both the basin and the treatment plant reach their maximum capacity, the facility must release disinfected wastewater into the Flint River to prevent backups and flooding within the sewer system.
City officials indicated that the March 7 discharge followed this emergency overflow procedure. The release included wastewater that had undergone disinfection but had not completed the full secondary treatment process due to the unusually high volume of incoming water.
Wet-weather events are a known challenge for many wastewater systems, particularly when rainwater and stormwater infiltrate sanitary sewer lines. These conditions can rapidly increase the amount of water arriving at treatment facilities, sometimes exceeding the infrastructure’s designed capacity.
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The city stated that testing of water samples related to the discharge will be conducted and reported through the State of Michigan’s public reporting system. Results from those tests will be made available on the state’s website once they are finalized.
Officials did not indicate how long the discharge lasted but emphasized that the event was tied directly to excessive inflow from storm conditions that pushed the treatment system beyond its operational limits.