Equipment and procedural improvements have resulted in lower salting rates while maintaining public safety. Understanding the groundwater contamination potential of salt storage, all salt stockpiles are stored indoors. Runoff collection systems are being installed around salt and sand stockpiles and truck washing areas. Maintenance yard housekeeping practices are designed to minimize salt brine runoff.

Mn/DOT snowplow operators from Alexandria to Zumbrota have a new tool in their snow fighting arsenal -an anti-icing solution. Liquid chemicals are applied to the roadway before a storm to prevent ice and snow from bonding with the pavement surface. Consider it a pre-emptive strike before the storm. Mn/DOT first experimented with anti-icing in the 1990's; now it's a standard winter practice statewide.

Does road salt impact Duluth Streams?

All contaminants to our streams are potentially harmful to the organisms that live there. Chloride (one of the components of road salt) is toxic to fish if the level is over 230 mg/L for a tenth of an organisms life span (100 - 200 days for brook trout) or a maximum of 860 mg/L for short periods of time.

DuluthStreams doesn't monitor the chloride levels in its streams, but it does monitor electrical conductivity (EC25); a measure of water's ability to conduct an electric current directly related to the total dissolved chloride content of the water. NRRI developed the following relationship between EC25 and the chloride levels of the road salt used by the city of Duluth:

The chronic chloride level of 230 mg/L is equivalent to a conductivity of about 960 µS/s.
The maximum chloride level of 860 mg/L is equivalent to a conductivity of about 2830 µS/s.

The following graph shows chloride levels in Chester Creek after a early winter snowfall and snowmelt. Before the road salt entered the creek, EC25 was around 300 µS/s, far below the chronic level of 960 µS/s. When runoff entered the creek, EC25 peaked at about 1600 µS/s, far below the maximum level of 2830 µS/s.

To learn more about this graph, and to see similar graphs from Kingsbury and Tisher Creek, go to the Chester Creek Storm Graph page.

As long as the choride levels in the streams remains within these boundaries, road salt isn't causing long-term problems for organisms in the streams.

What else do we know about salt effects in the environment?

More info about salt impacts on organisms is on our second page. You also may want to read about the USGS monitoring of Shingle Creek (a metro-area creek which is thought to be adversely impacted by decades of de-icing salt applications).

Salt Application Rates in Duluth, Minnesota:

These guidelines are used by City of Duluth Employees to determine how much salt (in pounds per mile) they need to apply to the roads to keep them safe. Workers re-evaluate weather conditions several times during the day to keep our roads safe while using the minimum amount of salt necessary.

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