Prevent Pollution: Road Salt and Our Environment

Photo shows rushes, grass-like plants, in a geen street planter surrounded by ice
Road salt, or sodium chloride (NaCl), and other products such as magnesium chloride (MgCl2) are used for deicing or anti-icing purposes. Find information and tips for home and business owners when considering how to treat sidewalks and driveways during icy conditions.
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Road salt can be harmful to our environment – affecting plants, wildlife, water quality, and property. It is best to use none or only the minimum amount needed on sidewalks, driveways, and parking areas, and to use less harmful alternatives to pure chloride salts.

What is the concern about road salt and our environment?

Salts can hurt the health of streams, plants, and natural areas. When ice and snow melt from sidewalks and streets, the salts – as well as everyday dirt, grime, and other pollutants – flow into storm drains, green street planters, and eventually local streams and groundwater. As traffic drives through the melt, it sprays roadside plants and soil.

The chlorides in these compounds can be toxic to aquatic life including fish, frogs, and insects. It can hurt plant growth and even soil quality. Areas of the country where winters are longer and road salt is used more frequently have reported that birds can become sick if they mistake salt crystals for seeds.

Can road salt affect my property and garden?

Yes. Salt can also damage concrete, corrode metal, damage plants in your garden, and dry out and even cause cracking of your pets’ paws.

Isn’t the salt diluted by rain and snow?

Yes. In general, salt products and other pollutants are diluted as they enter waterways. But salt can build up in the environment over time.  So even low levels of salt can result in harmful impacts to the environment over the course of years. In addition, smaller streams can be more affected by this pollution because they have less water flowing through them for dilution.

Doesn’t the City apply salt to the roads?

The Portland Bureau of Transportation winter road maintenance plans call for limited, targeted, and careful use of road salt – only when needed and only on priority streets. Deicing products are selected specifically to meet the needs of street application and traffic. Please see PBOT’s Winter Weather Basics and FAQs for more information.

Doesn’t the salt runoff go to the City’s wastewater treatment plant?

That depends on where you are in the city. Roughly one-third of the city has a combined sewer and stormwater system. In those areas (downtown and other older parts of the city), rain and snowmelt flow through storm drains and pipes to the city’s wastewater treatment plant. While the salt is not removed during the treatment process, it is highly diluted.

But in most of Portland outside of the inner city, stormwater does not go to the wastewater treatment plant. It instead flows to  green street planters, rain gardens, and some wetlands built to manage stormwater, or into pipes that lead to local streams, or it seeps into groundwater. That means that everyone should do their part to minimize the use of products and chemicals that get washed away by rain and snow and ice storms.

What is the role of green street planters in filtering pollutants including salt?

The city’s 2,000 green street planters that line city streets as well as rain gardens that are built in parking lots and on other private property absorb and filter pollutants, including road salt. But high levels of salt potentially can hurt the plants in those gardens.

What can I do to protect streams, fish, and wildlife – and my garden – from being harmed by deicing salts?

The City requires property owners to keep sidewalks clear in front of their homes or other properties. But, there are choices in how to do so. The best thing to protect the environment is to avoid using salt or deicing chemicals altogether. But, if sidewalks and pathways near your home are especially slippery, it may be necessary. In those cases, always follow the product instructions and use only the minimum amount needed. Throwing more salt down won’t speed up the melting process.

Safer alternatives to pure chloride salts exist, including sand or gravel. But even sand and gravel can be harmful to stream health, so be sure to shovel the material back up once the ice melts. Other alternatives include using a salt blend, or trying products with one these deicing ingredients:

  • Urea
  • Carbohydrates (such as beets, corn syrup, or grains)
  • Calcium magnesium acetate or potassium acetate

The Environmental Protection Agency has a website listing specific snowmelt or deicing products that are safer for people and the environment than standard rock salt. Once on the site, search or filter for "deicers" to get a list.

Always store salts and other chemical products in a safe responsible manner. Never disperse, pour, or spread chemicals in or near a storm drain or waterway.