Study finds elevated chloride levels in streams, points to road deicing as a culprit
An increase in the use of salt for road deicing over the past two decades may be contributing to increased levels of chloride — a component of salt — in streams and groundwater, where it can have an adverse effect on drinkingand wildlife, according to a new study from the U.S. Geological Survey (USGS). The USGS study, released in September, found chloride levels above the recommended federal criteria established to protect aquatic life in more than 40 percent of the urban streams tested in the study.
However, few of the tested areas had chronically high chloride levels, and most of the high chloride levels discovered by USGS were related to major storm events requiring exceptionally high road salt use in urban areas, not the result of routine discharges from deicing programs, according to the Alexandria, Va.-based Salt Institute. "Although regrettable, it can be understood that, after particularly intense snow and ice events, the amounts of deicers added toand consequently found in runoff will be greater than usual," Mort Satin, the Salt Institute's technical director, wrote in an article on the institute's Web site.
Mark DeVries, maintenance supervisor for the McHenry County, Ill., Department of Transportation, also has had concerns about the overuse of road salt for some time. "We've been preaching sensible salting and really trying to use only what's needed in any given situation for years," he says. DeVries says salt use by his agency has decreased by about 40 percent over the last decade.
The Beloit, Wis., Public Works Department practices the same techniques and monitors chloride levels in groundwater through specially drilled wells, says Director of Operations Chris Walsh. The effects of recent salt reduction methods will not be known for a couple of decades because salt enters groundwater very slowly. "We don't have a decrease yet, but we're in the parts per million where we need to be," Walsh says.
Annemarie Mannion is a Willowbrook, Ill.-based freelance writer.