Salt of the earth? Great. Salt in the earth? Not so great.

And salt in the water? Well, that’s even worse.

“Salt is toxic to aquatic life. It’s toxic to us,” Sam Briggs told me on a recent morning.

We were near Muddy Branch Road in Gaithersburg, Md., a road named for the creek that flows underneath it. Briggs is the clean water program director for the Izaak Walton League of America.

The environmental group’s headquarters is nearby, making it pretty convenient for Briggs to do what she was about to do: test the water in Muddy Branch to see how salty it was. She held a small plastic vial in one hand and a narrow plastic test strip in the other, its length marked with horizontal lines.

Briggs and her colleagues have sent thousands of similar test strips out across the country, where they form the backbone of its Winter Salt Watch program.

The effort was inspired by something that stared the league in the face in the winter of 2017: a big pile of road salt that appeared one day on the side of Muddy Branch Road, near a storm drain. You’ve probably seen piles like these: big berms that are left where a plow or a salt truck spilled some of its cargo after hitting a pothole or making a sharp turn or changing gears.

“People kept driving over it,” said Emily Bialowas, the league’s Chesapeake Monitoring Outreach coordinator.

Like a Popsicle in the sun, the berm got smaller over time, as it slowly eroded from the road and trickled into the gutter, then from the gutter into the storm drain, and from the storm drain into Muddy Branch.

The league decided to test the water in the creek, a stone’s throw from its offices.

“We saw chloride levels off the charts,” Bialowas said. “It sparked us to think about how we could do something. It can’t be a problem just at Muddy Branch. How can we get it to all the states?”

And thus Salt Watch was launched. The program invites the public to test the water in their area. The Izaak Walton League will send out a free kit with test strips and instructions on how to use them.

Salt Watchers upload the results via an app that geotags the location and adds the information to a database. The program is in 20 states now. More than 3,000 kits have been sent out this season to individuals, schools, community groups and other organizations. (For information, visit saltwatch.org.)

“This is a good socially distant activity,” Bialowas said as Briggs ambled down a snowy bank to the edge of Muddy Branch. Briggs filled the vial with creek water, then dropped a test strip into it.

Ice and snow are the enemies of locomotion. They’re difficult to walk on, dangerous to drive on. Humans deal with them in various ways, but the most common is to apply salt, which lowers the freezing point of water.

But salt is bad for the environment. Alternatives have their appeal, but also their shortcomings. Gritty sand provides traction on ice, but won’t melt it. Beet juice is more eco-friendly than salt, but when it washes into a body of water like the Chesapeake, it can contribute to algae blooms.

Other compounds — magnesium chloride, potassium chloride — are advertised as “greener” than sodium chloride, but, said Bialowas, “It’s all salt. All can put chloride in the water.”

Bialowas and Briggs say they aren’t anti-salt. They’re anti too much salt.

“There is rampant oversalting everywhere,” Bialowas said. “Salt is just to make it easier to plow. It’s not to melt it all away.”

“There’s a misconception that you want it crunchy underfoot,” Briggs said. “That’s way too much.”

If it’s scattered properly, a single coffee mug of salt is enough to treat a 20-foot driveway, she said.

The road salt industry has been responsive — its Smart Salt program encourages municipalities to apply salt properly — but reducing the spread of salt can be an uphill battle. People think that because a little is good, more must be better.

“People call the DOT and say there isn’t enough salt,” Bialowas said.

After five minutes, Briggs pulled out the test strip. A pale line had crept up the strip to nearly the top, stopping around the No. 9, indicating a chloride level over 618 parts per million. A reading of above 100 ppm is considered elevated for our region, Briggs said. Prolonged exposure to levels above 230 ppm is toxic to aquatic life.

“Last year was a mild salt year,” Briggs said. “With this year’s snow and thaw, there’s been some major spikes. It’s the worst year to date.”

Twitter: @johnkelly

For previous columns, visit washingtonpost.com/john-kelly.