The Impact of Road Salt

De-icing salts are among the biggest threats to local waterways. High salt levels after winter storms (or preparation for winter storms that never come) can kill fish and other aquatic wildlife. Salt in streams can impact human health as well. Filtering salt out of water is energy intensive, so salt from roads ends up in downstream drinking water supplies. In Philadelphia, directly downstream from many Lower Merion streams, salt levels in drinking water can reach harmful levels.

The Conservancy and our partner Dr. Steven Goldsmith of the Department of Geography and the Environment at Villanova University have been tracking the impacts of road salt on streams for years. In a previous study, Dr. Goldsmith found that municipalities that use brine instead of rock salt reduce salt levels in streams by 20-40%.

Individual actions matter too. In the same study, salt from parking lots, driveways, and sidewalks accounted for as much or more of the salinity levels in streams as salt from roads. If you salt, follow the instructions on the label to avoid over-salting. Extra salt can be swept up before the next rain storm to keep it out of the nearest stream. Business owners can follow the same advice or talk to the contractors they hire to salt about taking a more judicious approach. 

Click the image to take our salt survey survey

Salt alternatives – whether in the form of a different de-icing substance, roads and sidewalks made of materials that can melt ice, or another developing technology – would be ideal solutions, but Dr. Goldsmith’s research shows that we can meaningfully lower salt levels in streams using existing technology and better practices. 

Two grants from the National Fish and Wildlife Foundation are helping us go beyond our previous efforts to create change. The project involves stream monitoring, a salt-use survey and cost-benefit analysis for municipalities converting from using rock salt to using brine, which requires less salt because it melts ice more effectively. The monitoring equipment will stay in place to track salt levels over time. We will share updates as the project progresses.

Learn more about how salt impacts streams below in the Salty Waters story map and in Dr. Goldsmith’s lecture.

From our streets to our tap water: Consequences of road salt application in an increasingly paved world

Salty Waters StoryMap