De-Icers Impact on Streams in areas of high impervious cover.

 De-icers pose a serious threat to freshwater ecosystems in the Northeast - and not just in the winter. The road salt crunching under car tires in winter will be around a lot longer than drivers think. Once the snow is gone,  the salt will likely appear in nearby streams, and possibly drinking water.  The problem is made worse by the growing amount of roads and parking lots that have spread throughout vulnerable watersheds.

 According to a report published by the National Academy of Sciences, the long term presence of salt in freshwater streams and rivers has risen dramatically over the last 30 years, in both rural and urban areas. The research study also demonstrates that the highest salinity occurs in watersheds with the most roads and parking lots.

 Winter readings showed concentrations of chloride, an element of salt, at levels up to 25 percent of the concentration in seawater. But salinity levels do not just rise with winter weather.   They are higher year round. Summertime chloride levels are up to 100 times greater than unimpacted forested streams.

 Increased salinity levels in freshwater systems can harm aquatic life and contaminate human drinking water. If salinity continues to grow at the current rate, scientists warn that much of the region's water may become toxic to freshwater life and unfit for human consumption within the next 100 to 200 years without desalinization processes.

 U.S. Geological Survey satellite data revealed that the salinity levels of the Chesapeake Bay watershed is up 41% during the 1990's. 

 The article revealed that in Pennsylvania and Maryland alone in excess of one million tons of road salt are applied annually. This is in addition to the tons of salt applied by counties, local entities, homeowners and businesses.

 With as little as 10% impervious cover in a watershed, the variety of stream life may begin to decline. Salinity may be one of many factors that trigger this decline, because this latest research shows that relatively small areas of paved surface can generate a notable increase in salinity. At 40% impervious cover, high salinity levels can deliver chronic problems for freshwater plants and animals.

 The use of salt for de-icing is not regulated, although the EPA recommends that chloride levels in water reach no higher than 250 milligrams per liter.

Source Bay Journal, Volume 15, Number 10, January, 2006 - Alliance for the Chesapeake Bay

salinitylevels.doc