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 cree
