The Environmental Quality Institute

Road-Clearing: A Balance Between Safety and Environment
Too Much Could Hurt Waterways

Source: The Asheville Citizen-Times by Nanci Bompey, 01/12/2011

ASHEVILLE – The streams of salt and sand spreading from the back of state Department of Transportation trucks are anything but haphazardly applied.

Road-clearing crews put down 250 pounds of salt and sand per mile of lane, enough to ensure roads are free of ice but not harm the environment.

“For a two-lane road, that's 500 pounds per mile, which really isn't that much,” said Jeff Moore, DOT engineer.

“That is the minimum effective amount,” Moore said.

“It's necessary to keep the roads open, but we have to balance that against making sure we don't damage the environment,” Moore said. “We make sure we use only what we need.”

Studies in other areas of the country have shown salt and sand can be harmful to aquatic life, although there isn't much data in Western North Carolina.

Until last year, there also wasn't much concern, French Broad Riverkeeper Hartwell Carson said.

“It hasn't been one of our things, but if it is going to snow every couple of weeks a foot, it is something we might want to check on,” Carson said. “It would be interesting to answer the question. We know it does (affect water quality) in other places, but does it here?”

Runoff with high levels of salt can harm insects and fish, immediately and in the future.

It also can contaminate soil and harm vegetation.

“It could be toxic depending on the level of the salt that enters the stream, based on the size and the dilution in the stream, the size of the stream, aquatic life in the stream, how long it is exposed to that runoff,” said Roger Edwards, regional supervisor for surface water protection.

“There are a lot of factors taken into consideration,” Edwards said.

Wildlife, including birds, can also be attracted to the salt. When animals eat it, they can be eating other sediment on the road, and it can dehydrate them, Carson said.

Edwards said the state Division of Water Quality hasn't received any reports of fish kills associated with the salt and sand DOT puts on the roads.

The Environmental Quality Institute, which tests water quality monthly in Buncombe County, hasn't done any experiments looking specifically at the concentrations of salt in the water.

But monitoring data show that the highest conductivity readings occur in the winter or early spring, said Ann Marie Traylor, director of EQI.

Conductivity, or how well electricity is transmitted, is a way to measure the amount of dissolved ions in the water. These readings occur more frequently in urban streams, she said.

“We don't measure chloride, which is the main concern of the salt going into the water, but conductivity is an indirect measure of that,” Traylor said. “Other things could be causing high conductivity besides salt, but it does contribute.”

Carson said he wants to start testing local streams for chloride concentrations to get a better idea of how the road treatments are affecting local waterways.

But even with more data on salt and sand entering area waterways, finding ways to limit harm could be difficult.

Carson said new treatments other than traditional salt mixtures might be better for the environment, but they are costlier.

The most cost-effective and environmentally friendly approach might be to reduce the amount of salt used.

“I can understand the predicament we are in,” Carson said. “There is snow all over the place, and we don't want problems.”

Along with using the minimum amount of salt and sand mixture, in recent years the N.C. DOT started spraying a calibrated amount of brine solution on roads before it snows.

The solution, unlike straight salt, adheres better to the pavement, meaning less of it has to be used, and it is less likely to get blown off the roadway.

“We really try to be environmental stewards,” Moore, of DOT, said. “We try to be stewards of taxpayer money also.”

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