(December 21, 2017) – Because road salt can be harmful to our environment - affecting plants, wildlife and water quality - the City of Portland’s plans call for limited, targeted and careful use of road salt – only when needed and only on priority streets. Please see PBOT’s Winter Weather Salt Plan for 2017-2018.
Below are common questions about the environmental impacts of salt as well as tips for homeowners and businesses when considering how to treat sidewalks and driveways.
- What is the concern about road salt and our environment?
- Can road salt affect my property and garden?
- Isn't the salt diluted by rain and snow?
- Doesn’t the salt runoff go to the city’s wastewater treatment plant?
- What is the role of green street planters in filtering pollutants including salt?
- Is Environmental Services monitoring streams to detect salt and other pollutants?
- What can I do to protect streams, fish and wildlife - and my garden?
A: Road salt (sodium chloride of NaCl) and other products such as magnesium chloride (MgCl2) used for deicing or anti-icing purposes can affect the health of stream, plant life and natural areas.
When ice and snow melt from sidewalks and streets, road salts - as well as everyday dirt, grime and other contaminants -- flow into storm drains and green street planters and eventually to local streams and groundwater. The spray from traffic can also land on roadside vegetation.
The chlorides in these compounds can be toxic to aquatic life including fish, frogs and insects, and can affect plant growth and even soil quality. Areas of the country where road salt use is more prevalent also have reported that birds can become sick if they mistake salt crystals for seeds.
A: Yes. Salt can also damage concrete, corrode metal, damage plants in your garden and dry out and even cause cracking of your pets’ paws.
A: 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 are more susceptible to pollution because they have less water flowing through them.
A: That depends on where you are in the city. Roughly one-third of the city has a combined sewer and stormwater system and in those areas (downtown and other older parts of the city), rain and snowmelt flows 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 natural areas and into pipes that lead to local streams as well as seeping 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.
A: The city’s 2,000 green street planters that line city streets and can also be found in parking lots and other private property absorb and filter pollutants, including road salt. But high levels of salt potentially can affect those plantings as well.
Q: Is the Bureau of Environmental Services (BES) monitoring streams to detect the effect of salt and other pollutants?
A: Yes. Environmental Services has a year-round program to monitor stream health. In addition, when PBOT piloted the use of road salt during the severe storms of 2016-17 in the Johnson Creek basin, BES conducted a water quality study on the impacts. Our monitoring showed that salt levels are low – well below state water quality guidelines. We also detected low levels of chloride in areas of the watershed where PBOT didn’t apply salt – indicating that these pollutants are reaching the creek from other sources, possibly including homeowner and business use of road salt on sidewalks.
Environmental Services will continue to work with PBOT on stream monitoring and to evaluate and adapt winter roadway maintenance and storm response as warranted.
Q: What can I do to protect streams, fish and wildlife – and my garden - from being harmed by deicing salts?
A: The best thing 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.
Eco-friendly alternatives to commercial deicing products include 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.
Always store salts and other chemical products in a safe responsible manner. Never disperse chemicals in or near a storm drain or waterway.
You can find more clean river tips here.