Why You Should Not Swim During or 48 Hours After Heavy Rain
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It can be unsafe to swim, even at designated swimming beaches, for 48 hours after a rainfall due to the possible presence of high levels of bacteria that could pose a risk to human health. The bacteria could be a result from water pollution, which is a complex issue and can come from many sources, predominantly those listed below.
Improving beach water quality has been a priority for Toronto City Council for many years; eight of the beaches used for swimming have been awarded internationally recognized Blue Flag certification. Learn more about water quality at Toronto’s beaches.
In addition to the Blue Flag beaches, there are dozens of active boat clubs and marinas that are safe for recreational activities such as sailing, canoeing and kayaking. Please note that Toronto Harbour is unsafe for swimming at any time.
Where Water Pollution Comes From
As part of the natural water cycle:
- Rain and melting snow wash over the surface of land.
- What is not absorbed into the ground makes its way into watercourses.
- This is compounded in an urban city like Toronto with little or no place for water to be absorbed.
- Stormwater makes its way into the nearest creek, river or storm sewer, picking up what is left behind, before discharging into the nearest waterway.
- This includes what is on our roofs, roads, cars and sidewalks, such as:
- grease and oil
- bird and animal droppings
- pet waste left on sidewalks
- other pollutants
Learn more about stormwater, including what the City is doing to manage rain and melted snow and how you can help.
Some of the City’s older areas, where the sewer system was built as long as a century ago, have combined sewers in which there is only one pipe that carries both sewage and stormwater. During periods of heavy rainfall, combined sewers may fill beyond capacity, causing a combined sewer overflow.
These can occur when a homeowner or contractor incorrectly connects to a storm sewer rather than a sanitary sewer. In such cases, the discharge can flow directly into a stream, river or Lake Ontario. It is illegal and the City of Toronto actively searches out illegal cross connections.
Spills can include:
- Items discharged directly to the environment, including illegal dumping or even litter that makes its way into water.
- Pollutants that incorrectly enter the sewer system through manholes or catch basins (square grates on the road).
- Nothing other than rain or snow should enter a catch basin.
All spills should be reported to 311 immediately.
Water pollution can flow into Toronto waterways from their tributaries (i.e the many rivers and streams that flow into them). The tributaries – many of which are north of City’s boundaries – pick up pollution and debris from the stormwater runoff process, and through direct littering.