The thousands of tons of salt spread out on roads in the colder areas of the US in late December has not yet reached its final destination, nor had its final effect. As the winter snows melt away, that salt will work its way into storm drains and into local waterways, increasing the salt levels in rivers, lakes, and other municipal water sources.
The problem has been around for at least 60 years, since road crews have been using salt to make roads passable in winter. The average sodium concentration in the Delaware River, for example, has increased three-fold in that span, and its chloride concentration is about five times higher.
Officials with the Philadelphia Water Department, meanwhile, say that water intakes contain sodium concentrations at times that exceed current recommended levels from the American Heart Association and the US Environmental Protection Agency. Thanks to the Department's ability to mix in water with lower salinity, the final product contains acceptable levels, authorities say.
But environmental experts say that if current trends continue, aquatic life will begin to be affected in coming decades, and water supplies could become threatened. Sodium is also a particular concern for people with medical conditions like hypertension. Experts on the subject have called the nation's use of salt on roadways “unsustainable.”
Between December 26th and 28th, PennDot dispersed a reported 8,000 tons of salt in Southeastern Pennsylvania, while the city of Philadelphia added 7,000 tons itself. And that doesn't include the hundreds of smaller municipalities and thousands of businesses and residents who added even more.