Combined Sewer Overflows FAQ
City of Toledo Wastewater Treatment
Sanitary Sewer System
In Toledo, after water has been used in homes and businesses, it moves from toilets and drains into sanitary sewer lines to be transported to the Bay View Wastewater Treatment Plant, where it is filtered and processed to remove bacteria and other contaminants before being returned to the Maumee River to flow back out to Lake Erie.
Storm Water System
The City’s storm water system collects water from rain events, melting snow, and roadway run-off and returns this water to our creeks, rivers, and Lake Erie through a series of ditches and piping.
What are Combined Sewer Overflows?
In older areas of Toledo, portions of the sanitary sewer and storm water collection systems are combined. During heavy rain events, combined sewers can become completely filled with rainwater, with the water flowing into Swan Creek, and the Ottawa and Maumee Rivers through relief points designed to reduce basement flooding-- These relief points are called Combined Sewer Overflows or CSOs. To learn more, click here.
Where are the CSOs located?
During heavy rain events, portions of the system that have combined sanitary and storm sewers can become completely filled with rainwater, with the water having nowhere to go but to overflow into the waterways. These points of relief are called Combined Sewer Overflows and are located along Swan Creek and the Ottawa and Maumee Rivers.
How is the City of Toledo managing and lessening the impact of CSOs?
The Toledo Waterways Initiative (TWI) has increased the wastewater collection system’s capacity to capture and hold the combined flow during heavy rains until the waste water treatment plant can process it. To learn more, click here.
TWI is doing this through the construction of underground storage tunnels and basins and sewer separation. The City is also eliminating 8 CSO locations.
How do CSOs affect the Toledo community?
The City is permitted to have a limited number of CSOs in order to protect public health. Without Combined Sewer Overflows, the incidence of sewer water backups into roadways and basements would be greatly increased.
How much untreated sewage is in these outfalls?
CSOs consist of a combination of untreated, but highly diluted, sewage and storm water. These overflows are regulated by the Ohio EPA and on average contain less than 25 milligrams per liter of suspended solids (waste material).
What is the impact of the CSO outfall on public health?
Overflows are meant to protect public health by reducing backups into basements during heavy rains by relieving pressure on the system at specified locations.
What is the impact to our watershed from these outfalls?
Both the incidence of outfalls and volume will be significantly reduced upon completion of the TWI program in 2020. Combined sewer overflow events per location will be reduced on average from 34 to 3 annually. There will be on average 650 million gallons less pollution entering our waterways each year.
What can I do to help reduce water pollution?
Individual households and businesses can combine with others to make a huge difference in water quality through sustainability practices that are sensible and cost-effective. Click here to learn more about environmental practices for everyday activities that can help to protect our water.
Combined Sewer Overflows (CSOs) are caused by heavy or extended wet weather events. These can be heavy downpours or slow steady rainfall over many hours or days, and can also occur with significant amounts of melting snow. These and other weather-related activities can exceed the capacity of the wastewater collection system to capture all water for treatment.
- The Toledo Waterways Initiative (TWI) is increasing capacity in the system to capture and hold the combined flow during heavy rains until the Bay View Wastewater Treatment Plant can process it. It is doing so through the construction of underground storage tunnels and basins, such as those beneath Joe E. Brown and International Parks, and sewer separation projects, such as those in the Lockwood/Devilbiss and Junction Avenue neighborhoods.
- The TWI program is eliminating 8 CSOs in the City of Toledo.
- Combined sewer overflow events per location will be reduced on average from 34 to 3 annually.
- When the TWI program is complete in 2020, there will be 650 million gallons less pollution entering the waterway each year on average.