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Where Does Pollution Come From?

Litter, dirt, oil and antifreeze from cars, pet waste and anything else on the ground is picked up in stormwater and goes into the city’s creeks and rivers. That contaminated stormwater ends up in Lake Ontario. The lake is the source of our drinking water. The more polluted the lake water gets, the more difficult and expensive it is to clean it.

Laws and new technology have done a lot to improve the environment. Today, most stormwater pollution comes from a lot of small actions, commercial and residential, added together.

What the City is Doing

The City works hard to reduce pollution in stormwater and is continually improving the ways it protects water quality. Stormwater flows into Lake Ontario which is the source of our drinking water. Preventing stormwater pollution is very important.

After the winter season, the City's Transportation and Works Department clears sand and debris left behind on roads, sidewalks, and other areas. From June to the end of October, Business Improvement Areas (Streetsville, Port Credit, Malton, Clarkson) are swept weekly, main roads are swept bi-weekly and industrial roads are swept monthly. With less litter on the streets, there's less for the stormwater to pick up.

Streetsweeping cannot protect water quality from oil and antifreeze from cars, bacteria from pet waste, and excess lawn fertilizer and pesticides.

In some areas of Mississauga, we do have treatment facilities. Devices like oil and grit separators and wet ponds trap some sediments and oils, reducing contamination.

In storms with a lot of rainfall, however, these facilities can overflow. Unfortunately, the majority of stormwater is not treated before it flows to Lake Ontario.


You may not see it when it rains but erosion is also one of the biggest sources of pollution. A lot of fast-moving water can wash away the banks of natural creeks and rivers. Too much dirt makes the water cloudy and changes which fish and other species can live in the water. To prevent erosion, the City has reinforced creek banks with large stones and planted species with strong roots to hold back the soil.

Enforcement of Pollution By-law

By-law 259-05 makes it illegal to put anything or any chemical into the City's stormwater drainage system that does not belong there. The City's by law makes sure that people are held accountable if they pollute. Pollution harms everyone. If convicted of violating the Storm Sewer By-Law, you could be held liable for cleanup and repair costs and face a fine of up to $100,000 per offence.

Private drainage systems that connect to the City stormwater drainage system must be maintained by the property owner.

Read this Storm Sewer By-law brochure for more information.

How to Help

You may think that just a few drops of oil or antifreeze on your driveway aren't a problem but with more than 150,000 driveways in the city, those few drops add up to hundreds of litres of polluted runoff entering our streams and Lake Ontario.

When we work together, we can all help protect Lake Ontario from pollution. Pollution in stormwater can come from many sources. There are a lot of ways you can help reduce pollution like picking up pet waste, washing your car at a car-wash that is connected to the sanitary sewer, and checking your vehicle for fluid leaks.

Yellow Fish Road™ Program

The Yellow Fish Road™ Program educates the community about the dangers of dumping or flushing unwanted household hazardous wastes into roadside and backyard storm drainage inlets, called catch basins.

For more information about what you can do: