The Western Beaches storage tunnel prevents combined sewer overflows from going directly in Lake Ontario by intercepting them from the storm sewers and combined sewers. Four kilometres long with three huge holding tanks, the tunnel helps clean up pollution of near-shore waters in the western beaches area of the city.
There are two underground detention tanks at Toronto’s Eastern Beaches which capture and hold combined sewer overflows and stormwater. The wastewater then goes for treatment before being returned to the lake. The tanks have significantly improved water quality and reduced the number of days the eastern beaches are posted unsafe for swimming in the summer.