Road Salt Delivering a Toxic Shock to Animals

By LEE BERGQUIST

This winter’s heavy snowfall is responsible for record amounts of salt on Wisconsin roads, but water quality experts are raising concerns about the effects of so much salt on the environment.

In metropolitan Milwaukee, road salt, or sodium chloride, and other melting agents wash into urban streams at levels that potentially kill fish and other aquatic life until it passes.

Last year, a scientist with the U.S. Geological Survey found that water quality at seven of 12 streams in metropolitan Milwaukee showed signs of acute toxicity on fathead minnows and a type of water flea after two storms on Feb. 26 and March 7. Scientist Steve Corsi said the findings of chloride concentrations exceeded the EPA’s toxic standard of 850 parts per million on the Kinnickinnic, Menomonee and Root rivers and on Honey, Underwood, Lincoln and Little Menomonee creeks.

On Feb. 26, 2007, at Honey Creek in Wauwatosa, chloride levels essentially became saline water for a few hours, hitting 6,470 parts per million.

By contrast, Corsi used Parnell Creek in the Kettle Moraine State Forest as a control stream. It was not affected by road salt and registered 20.4 parts per million, he found.

Timothy J. Ehlinger, a specialist in ecology and aquatic habitat at the University of Wisconsin-Milwaukee, called Corsi’s work "very troubling." But it also corroborated his research at various streams in southeastern Wisconsin and elsewhere.

Ehlinger’s water-quality monitoring has included Underwood Creek near Watertown Plank Road. On Feb. 24, 2001, freezing rain was forecast for the morning commute.

Trucks salted the road as a precaution. As the rain hit, chloride levels jumped from about 900 parts per million to almost 11,000 in four hours — creating conditions that were lethal to fish and aquatic life, Ehlinger said.

Such a condition, if it doesn’t kill fish, pushes their tolerances because it forces fish to expend more energy that can weaken their immune systems and affect reproduction, he said.

Corsi also has conducted longer-term monitoring of Wilson Park Creek on the south side to see if de-icing of planes at Mitchell International Airport affected water quality of the stream, which is a tributary of the Kinnickinnic.

De-icing didn’t, but chloride levels reached acute toxic levels on 46% of winter days tested in 2003, 51% in 2004, 54% in 2005, 61% in 2006 and 36% in 2007, Corsi found.

Through mid-February of this year, Corsi found that on 86% of the days, the stream exceeded acute toxic levels.

"A significant number of streams are highly impacted by road salt," he said, especially the first melt after a storm.

Streams and rivers in the Lake Michigan watershed eventually flow into the lake, where salinity has increased by more than a third since 1983, though still well below acceptable levels, according to the U.S. Environmental Protection Agency.

A draft report by the Southeastern Wisconsin Regional Planning Commission corroborated these findings and concluded that chloride levels were rising in the region, but within accepted norms.

The report, however, said the trend was a "cause for concern" and it urged local government units not to apply more salt than necessary.

"This is really a dilemma because we want to keep our roads safe," said Roger Bannerman, a water resources management specialist with the state Department of Natural Resources. "But the problem is real, and it’s going to be growing worse over time."

Public expectations

Road salt provides unquestioned safety — and officials say the public increasingly expects to drive on bare pavement during and immediately after storms.

The Wisconsin Department of Transportation estimated that a record 700,000 tons of salt will be used on state highways this year, compared with 405,000 tons last winter.

County highway departments handle salting for the DOT, and officials at county and state levels try to control overuse and have employed an array of techniques to make salt work better, such as adding water to make a brine that speeds melting.

"Who wants saltwater to contaminate our streams or groundwater?" said Michael Sproul, the DOT’s winter operations engineer.

But he said road departments are under pressure from motorists who demand that highways be free of snow and ice.

"Over time, our level of service has probably crept up," Sproul said.

This winter has proved to be especially troublesome because cold weather requires more salt.

One pound of salt can melt 46.3 pounds of ice when the pavement temperature is 30 degrees, Sproul said.

When the pavement drops to 5 degrees, one pound of salt can melt only a tenth as much — 4.1 pounds of ice.

Madison has felt the effects of road salt more than other communities.

Three drinking-water wells have had sodium levels in excess of the federal recommended maximum standard of 20 parts per million, according to a 2006 report by a city task force.

In 1992, Madison was forced to abandon one of its wells when sodium levels exceeded 45 parts per million.

The report also showed that private contractors spread salt more freely than city crews, underscoring the role that salting on private property has on watersheds.

The city queried contractors about their salting practices and concluded that they applied as much salt on parking lots as the city used on streets.

Madison uses less

Madison salts only about a third of its streets, meaning that many roads are covered with snow and ice over the winter, said Al Schumacher, the city’s street superintendent.

In contrast, Milwaukee has a bare pavement policy, according to Wanda Booker, city sanitation services manager.

Milwaukee used 83,000 tons from November through Friday — a record, according to Department of Public Works spokeswoman Cecilia Gilbert.

On average, Milwaukee uses twice as much salt per lane mile as Madison, according to figures supplied by the two cities.

"In Madison, there is an expectation that they don’t salt their streets," Booker said. "That is not the expectation here in Milwaukee. The public wants bare pavement."

The DNR does not regulate non-point pollutants, including substances applied to roads that end up in streams, but instead encourages parties to use best management practices, said Bob Masnado, who oversees the DNR’s water evaluation efforts.

"Storm water, it comes, it goes, it’s hard to manage," Masnado said.

But Cheryl Nenn of the Friends of Milwaukee’s Rivers thinks that the DNR needs to do more about road salt.

The group’s law firm, Midwest Environmental Advocates, filed comments in November 2007 regarding the City of Milwaukee’s application for a municipal wastewater permit.

It said current standards were vague and unenforceable. It urged the DNR to target chloride as a pollutant, and at a minimum, it should conduct regular monitoring after storms and during spring snowmelt.