Winter Salt

Winter salt has become an environmental topic of great concern in our watershed and beyond. Typically made of sodium chloride (table salt) and sometimes including calcium and/or magnesium chloride, winter salt is used to keep ice from forming on roads, sidewalks and parking lots, making them safer for travelling.

How it works

Salt lowers water’s freezing point — the temperature at which it changes from a liquid to a solid state and vice versa. It works best at temperatures between zero and –7°C. It isn’t necessary to melt all the snow and ice on roads, sidewalks, and parking lots for salt to be effective. Once the bond is broken between the pavement and the ice, it’s easier for plows and shovels to scrape the ice off the surface.

The concern

As winter salt melts snow and ice, salt dissolves and the chloride remains the water which then enters our rivers, streams, and eventually Lake Simcoe. And there isn’t an effective way to get it out.

In short, we’re applying more winter salt than is necessary for our immediate safety, which is having a longer-term negative impact on our aquatic environment and as well as our drinking water, infrastructure, cars, and more!

Over the last few years, aquatic monitoring shows a worrying increase of chloride in many of our rivers, streams, and even Lake Simcoe (see graph). Since plants and animals in the watershed are adapted to fresh water, the increasing chloride concentrations are impacting them.

The only way we can address this issue is by reducing the amount of winter salt we use. Since merely destroying or preventing the bond between pavement and frozen water is more than enough to make roads, sidewalks, and parking lots safe, using less winter salt is a more efficient, economical and environmentally sensitive approach to helping our everyone in our communities, including natural ecosystems, stay safe.

A look at the numbers

Conservation Authority researchers estimate that each year, communities in our watershed use 120,000 tonnes of winter salt. Because of this, Lake Simcoe is seeing a steady increase of chloride — 0.7 mg/L per year (see graph). Since they are the first contact, many our streams and rivers are seeing much higher increases.

The Canadian government sets out water quality guidelines that define the levels at which chloride affects aquatic life. There are two different guidelines:

Long-term exposure refers to concentrations that harm aquatic life over a long period of time, such as seeing certain fish species decline over time. This guideline is a maximum of 120 milligrams of chloride per litre of water (120 mg/L).

Short-term exposure means levels are high enough that severe effects to aquatic life can be seen in as little as 24 hours. This guideline is 640 milligrams of chloride per litre of water (640 mg/L).

In our streams and rivers, particularly in urban areas, concentrations regularly exceed both guidelines, often for extended periods and long after winter ends. For example, in February 2025, a concentration of over 26,000 mg/L was found in Newmarket’s Western Creek — higher than typical seawater concentration (which is 19,400 mg/L).

Making a dent in winter salt use

Salt tastes great on your fries… so how bad can it be? Perhaps the reason people don’t associate road salt with an environmental problem is exactly because we put the substance on our food.

The biggest problems are roads and commercial parking lots

To make meaningful progress in reducing winter sale use, we need to focus on the biggest sources: roads and commercial parking lots.

While road authorities must follow established provincial regulations around snow clearing and maintenance, there are ways to use winter salt more responsibly. Our municipal partners are continually looking for ways to further reduce the amount of salt they apply by using new technologies, materials, and decision-making tools.

There are no similar guidelines and protocols for commercial and institutional parking lots. The Smart About Salt® Council has done extensive research and has implemented a best management practices protocol which includes training and a certification program. But the program is voluntary, and few contractors have this training. Due to concerns around costly slip, trip, and fall claims, many apply far more salt than is needed for achieving safe parking lot surfaces.

So how much is the ‘right' amount?

If there is salt crunching under your feet and the sidewalk is dry, there is too much salt.

It takes far less salt to melt snow and ice than many of us think! The appropriate application rate will depend on the conditions (temperature, existing snow and ice cover, how much snow is expected), but more does not mean better. Ideally, there should be no residual salt once the snow and ice on a surface have melted. Anything more than that means that salt is being wasted, which means increased costs, and negative impacts on both infrastructure and the environment.

In the photo on the right the small amount of salt in the bag is all that is needed to melt the ice in the square.

What we're doing

Continued monitoring: We undertake regular monitoring of chloride concentrations throughout the watershed as part of our water quality monitoring program. This enables us to track trends over time and see where issues are emerging.

Partnering for change: Collaboration is key. We’ve created and continue participating in salt working groups, bringing together experts from the public sector, private sector, non-governmental organizations, legal community, regulators and academics.

Research to inform guidelines: Our researchers have done friction testing to track the effectiveness of salt application on various surfaces to determine the right amount of salt to achieve safe conditions. They’ve also evaluated salt use on oversalted commercial parking lots versus best management practices. We regularly partner with other agencies and universities to conduct research on salt and other winter maintenance practices.

Parking lot design with winter in mind: We’ve developed parking lot design guidelines to reduce the amount of salt needed to maintain safe surfaces. We’re also encouraging municipalities to incorporate these guidelines into their policies.

What you can do

You are key to the solution! What you can do for the environment when it comes to winter salt use is best summed up with three P’s:

Prepare: Shovel your driveway and sidewalk as soon as possible so ice doesn’t have a chance to form. Wear sturdy winter boots. Use snow tires. Redirect downspouts away from paved areas so ice can’t form.

Patience: Snow can slow travel down. Consider leaving early or accept that you may be late. This is winter in Canada!

Promote: If you see too much salt being used, speak to the property owner. Tell them about the environmental consequences of applying too much. Ask them to contact us. We can direct them to agencies like Smart About Salt® for training in correct winter salt use.

Get Smart About Salt

Smart About Salt^® is a voluntary not-for-profit organization that offers training to improve winter salting practices and recognizes industry leaders through certification.

Parking Lot Design

When parking lots are designed with winter maintenance in mind, they naturally require less salt application to maintain the same level of service without increasing liability.

Read About Our Parking Lot Design Guidelines

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