In the U.S., we apply approximately 20 million tons of salt to the roads every year. And in New York, 15 tons of salt are applied for every mile of roadway.
"There’s an enormous amount of salt being applied and it all has to go somewhere. When we have rain or snow melt, all that road salt that you see piled up on the sidewalks or piled up on the roadway runs off gets into our storm drains and ultimately discharges into our local rivers and streams," said Dr. Laura Lautz, an earth science professor at Syracuse University.
That’s especially problematic in channelized streams through urban neighborhoods as researchers documented by taking samples along this creek every one or two weeks for a year.
For example, in Meadowbrook in December, after a big rain event or a big run off event, you can see chloride concentrations in that creek that are 2,000 milligrams per liter.
That level can be toxic for aquatic organisms and plants.
More normal streams might have chloride concentrations of 10 milligrams per liter.
Salt occurs naturally in our water systems, so it’s not surprising to find sodium chloride in any waterway. Even in the middle of a forest you would expect to see sodium chloride in the water. It’s really just the degree which we elevate the concentration by our really efficient delivery of salt to streams from roadways.