Storm Sewer

Storm sewers capture rainwater or snowmelt from residential and commercial properties. This water flows into nearby watercourses or the lake. Watercourses include creeks, streams and rivers - natural, concrete channels or underground pipes - that carry water, including stormwater and snowmelt from catchbasins into Lake Ontario. In a combined sewer, there is only one pipe which carries both sanitary and storm drainage. During wet weather, the volume of water may exceed the treatment plant's capacity and some of the water overflows untreated into the lake. Toronto has a program aimed at installing storm sewer pipes beside existing combined sewers. The storm sewers will carry stormwater and snowmelt and the old combined sewer will handle sanitary sewage only, eliminating the overflow in wet weather.