Stormwater Runoff and Sewer Overflows
What happens when it rains?
Each year, billions of litres of raw sewage ends up in the Great Lakes. Periods of heavy rainfall or snowmelt can cause the water volume reaching sewer systems to exceed their capacity, resulting in the release of untreated wastewater directly into the Great Lakes. Discharges of partially treated or untreated sewage can contain pathogens, phosphorus and harmful pollutants, with potentially devastating impacts on human health and the environment.
Sewage continues to be among the top pollution sources for the lakes. The number of sewage discharges is not likely to be reduced without a significant investment in infrastructure – a need that will grow more urgent as population density increases and climate change results in more frequent and extreme storms capable of overwhelming existing sewer systems.