Posted: Sep 17, 2009 7:56 AM by Associated Press
Many urban streams have become salty enough to harm aquatic life, largely because of salt used for deicing roads in the winter, according to a new government study released Wednesday.
The U.S. Geological Survey studied urban streams and groundwater for levels of chloride, a component of salt, in 20 states spanning from Alaska to the Great Lakes and Northeast.
It found chloride concentrations above federal recommendations designed to protect aquatic life in more than 40 percent of urban streams tested. The highest levels were measured in those streams during the winter - as much as 20 times the federal guidelines - when salt and other chemicals are commonly used for deicing.
The problem was less serious in groundwater, and fewer than 2 percent of the drinking-water wells sampled had chloride levels higher than federal standards for human consumption. Chloride levels generally were much higher in urban than rural areas.
High chloride levels can slow plant growth, impair reproduction and reduce the diversity of organisms in affected waters. It also can affect the taste of drinking water drawn from them.
Matthew Larsen, the federal agency's associate director for water, said road safety is a top priority when state and local officials decide to use salt.
Not surprising, but a reminder
"And clearly salt is an effective deicer that prevents accidents, saves lives, and reduces property losses," Larsen said in a statement accompanying the report. "These findings are not surprising, but rather remind us of the unintended consequences that salt use for deicing may have on our waters."
For those reasons, Larsen noted, transportation officials continue to develop innovations that reduce the need for road salt without compromising safety.
The study found the rising levels were consistent over the last two decades with more use of road salt and the expansion of road networks and parking lots that get deicing.
Some of the highest concentrations of chloride were found in two creeks in the Twin Cities and four creeks in suburban Chicago, but Lincoln Creek in Milwaukee exceeded the federal guidelines the most out of all the streams cited in the study.
The findings are consistent with several other studies that blamed road salt, and its increased use, for water quality problems in streams and aquifers.