Portland’s first snowstorm of the winter storm season hit mid-day prompting thousands of people to head home early. Unfortunately, roadways were clogged for hours leaving many to abandon their cars. Cautious motorists decided to stay home from work when the second snowstorm that left roadways icy for days. Portland is now looking at adding road salt to their arsenal to make road ways safer.
The city is concerned with the damaging effects of road salt. It would ultimately get washed into storm drains which flow to a sewer treatment plant. Will the salt corrode old metro-area pipes? It affects the roads, the steel in the bridges and the concrete and it affects your car. And, the salt that stays on the roads will eventually get washed into the environment.
Minnesota is beginning to see some of the environmental effects of road salt use. In the Twin Cities metro area, the level of salt (chloride) in 39 surface waters now exceeds water quality standards. An additional 38 surface waters are almost above the standard and many others remain untested. Data shows that salt concentrations are continuing to increase in both surface waters and groundwater across the state.
The fact is that it only takes one teaspoon of road salt to permanently pollute 5 gallons of water. Once in the water, there is no way to remove the chloride. At high concentrations, chloride can harm fish, aquatic plant life, groundwater and drinking water supplies.
In 2013 U.S. officials applied about 17 million tons of salt to roads. Salt lowers the freezing temperature of water and thus melts street-clogging snow and ice. But its public safety benefits do come with some ecological drawbacks.
Salt not only damages metal and concrete, it contaminates drinking water, kills vegetation, and accumulates in streams, lakes, reservoirs, and groundwater, harming aquatic plants and animals. As much as 70% of salt spread on roadways stays within the watershed.
Now that we know where the salt goes, where does it come from?
The U.S. is the second-largest road salt producer worldwide after China, but we also import a good deal of the salt it uses to coat its streets. At 12 million tons per year, America is the biggest salt importer in the world. Most salt imports come from Canada and Chile.
Rock salt is formed in the ocean. The chlorine coming from the volcanoes at the bottom of the ocean mixes with the sodium washing off the continents with rainwater to create salt. There is a lot of salt in the oceans, but it is only about 3½% of the worlds salt supply. Areas with thick salt deposits was probably one where an ocean was, but has since evaporated.