Low-salt diet for roads aims at keeping drinking water from tasting briny

Woodbury wants to make its golf course environmentally friendly by reusing rain from ponds to keep the fairways green, rather than sucking up underground supplies needed for the kitchen tap.

But the city is finding it can't always do that until well into the spring. That's because, after the city has spent the winter flinging salt onto the roads, the water is too briny for the grass.

So Woodbury is buying more sophisticated anti-icing gear, hoping to prevent what it warns could otherwise happen: a tripling of the cost of household drinking water because of the need to remove salt.

"We have seen elevated chlorine even in deep aquifers," said Brooke Asleson, metro watershed project manager for the Minnesota Pollution Control Agency, or MPCA. "That's not a health issue, but taste matters. If peoples' water gets salty, they are not going to be happy."

A 2015 study showed that chloride concentrations in Frost Belt streams doubled from 1990 to 2011, posing threats to aquatic life. As the brininess of our water rises, Minnesota state officials are devising ways to show local street maintenance crews how what they do now can affect the environment later.

Hundreds of local jurisdictions are taking part in an online exercise that rates what's going on out there now on a scale from "poor" to "advanced."

A PowerPoint presentation prepared for a national conference shows that St. Paul's self-assessment turned up 86 "poor" practices as recently as 2010. The city pledges to wrench that back to just two by the winter of 2020-21.

Improvement isn't going to be instantaneous, said Matthew Morreim, assistant street maintenance engineer for St. Paul Public Works, partly because it costs a lot to upgrade equipment beyond just flinging chunks of salt.

"We've already spent a lot to upgrade the way we do our operations," Morreim said.

For instance, retrofitting 40 salt trucks to pre-wet salt to make it work better and control its dispensing via electronics can run $20,000 a vehicle.

St. Paul also is getting a fifth, 2,000-gallon tanker truck to spray a better de-icer than salt onto the roadways. "Those vehicles cost about $40,000 apiece," he said.

But there's a savings, too: Salt costs money, and St. Paul is using less.

The city has decreased usage by 20 percent, from about 20,000 tons a year to 16,000. For a light dusting of snow, the amount of salt used has plummeted from up to 100,000 tons back in the day to less than 10,000 tons today.

Woodbury is buying a small tank, said spokesman Jason Egerstrom, and hopes to reduce its $300,000 annual salt tabby 10 percent as a result. The new anti-icing gear should cut costs by reducing frost on bridge decks and limiting infrastructure damage from salt corrosion. In addition, it will help manage pollutants in the water, he said.

Three-quarters of the state's 600 plow trucks — which treat 30,000-plus lane-miles — have advanced anti-acing technology, said Susan Lodahl of the Minnesota Department of Transportation. The technology reduces the corrosion of roads and trucks.

Statewide, the MPCA's Asleson said, cities, counties and other de-icing jurisdictions can be divided into "shining stars who've done amazing things" such as Richfield and Shoreview, and many more that have made "some progress, but are not where we need to be."

Regulators apply pressure on local governments whenever analysis finds that bodies of water are either over or nearing acceptable thresholds for chloride concentrations.

That's true of Woodbury, where the City Council was warned by its staff this fall that of the nearly 40 bodies of water in the metro area that exceed permissible chloride levels all or parts of three were within city limits.

Although road salt is a major contributor to the problem, it isn't the only one, said Carmelita Nelson, water conservation specialist for the Minnesota Department of Natural Resources.

Residential water softeners also take a toll, Nelson said, adding that some cities also soften their water before distributing it.

On roads themselves, officials aim to reduce not just salt but also sand, which they say looks more effective than it really is.

MnDOT does use sand at times when it does some good, Lodahl said, but the list of shortcomings is long.

"Sand has no ice-melting capacity," she said. "Sand is only efficient for traction if it is on top of the ice surface. Sand is expensive to clean up. Sand gets in our storm sewers, lakes, streams and ditches, which can negatively impact the environment. And sand can give drivers a false sense of security."

David Peterson • 651-925-5039