Chlorides in Capisic Brook
What happens to the salt we use to deice our roads winter?
As anyone in a cold climate knows, salt is used all winter to keep our roads safe and ice-free. As winter transitions to spring and our snowbanks melt away, the salt seems to disappear too. Unfortunately, that couldn’t be farther from the truth.
Road salt is made of sodium chloride. As the weather warms, the melting snow dissolves the sodium chloride salt and the salty water flows into our rivers and streams.
Elevated levels of chloride is a serious threat to the entire ecosystem that calls our waterways home. Aquatic environments begin to show signs of low levels of stress when the amount of chloride in the water from road salt reaches 0.23 parts per thousand (ppt). When freshwater reaches 0.86 ppt, we see significant levels of stress. You can think of 1 ppt as one dollar in $1000, meaning that 0.86 ppt is equivalent to 86 cents in $1000. In other words, only a little bit of chloride in an aquatic environment is very toxic.
Capisic Brook runs thorugh Westrbook and Portland, where it feeds into the Fore River. All 4.1 miles of the brook are designated as an impaired stream due to decades of stormwater pollution. The Capisic Brook watershed contains 31% impervious cover, meaning 31% of the snow and rain that falls in the Capisic Brook watershed lands on hard surfaces where it is unable to filter into the ground. Many impervious surfaces such as roads and parking lots are heavily salted all winter long. During the spring melt as our streams are inundated with polluted snowmelt, chloride concentrations in Capisic Brook rises well over 0.86 ppt and causes significant levels of stress..
Capisic Brook is unfortunately only one of many impaired streams in Cumberland County. Learn more about chlorides and aquatic life here: