Thousands of tons of rock salt and hundreds of thousands of gallons of calcium chloride, brine and other sodium-based products were spread over the state’s roadways during last week’s blizzard. Salt is crucial to motorists’ safety but the amount that’s put down each year concerns environmentalists because of the long-term effects on drinking water. What’s dumped on the road spills into waterways, seeps into groundwater and eventually flows into wells and home faucets. Up to 60 percent of road salt infiltrates ground water, according to the state Department of Environmental Protection. And with more snow and rain coming today, those concerns are growing.

Another sloppy storm is expected to blow through New Jersey tonight, bringing up to six inches to the state’s northern counties, but hopefully giving South Jersey — still feeling the effects of two major storms within a week — a break.

Morris, Sussex and Warren counties are expected to get the brunt of today’s storm, with the northeast and the central parts of the state getting two to three inches, according to the National Weather Service.

In many areas, the snow may mix with rain, followed by plummeting temperatures. That means commuters’ least favorite condition: ice.

Road salt already has caused problems in some drinking-water supplies in Bergen and Morris counties. Mahwah stopped using one of its 12 municipal wells years ago because of a high sodium content officials believe came from road salt dumped on Route 17.

“In high doses salt is a toxin, so you want to limit the amount that goes into the ground,” said Ella Filippone, executive director of the Passaic River Watershed Coalition. “It’s not a major problem yet, but as salt is more frequently used by road crews there is a need to start finding an alternative for the roads.”

Pequannock plans to spend more than $3 million for a salt dilution plant, Mayor Edward Engelbart said. Salt levels increased in recent decades after Route 287 was completed, and he suspects runoff from the interstate is the culprit. The dilution plant will blend pristine water from the Newark watershed with Pequannock well water, he said.

“It’s a trade off. We definitely want safer roads but there is also a concern that too much salt in the water could be a health issue,” Engelbart said.

United Water, whose Oradell reservoir serves 750,000 people in 60 towns in Bergen and Hudson counties, said its water reached 51 milligrams per liter — one milligram above the DEP’s recommended upper limit of sodium.

While that amount is two to three times less sodium than in a liter of Diet Coke, the company advised customers with high blood pressure and salt-restricted diets to consult their doctors about the levels.

Salt-contaminated runoff can also damage nearby trees and shrubs. Birds and aquatic life, especially young fish, also are at risk from salt runoff, according to the DEP.

Still, salt is an essential winter tool for road crews. Morris County pre-wets rock salt with water and calcium chloride to enhance rock salt’s melting ability, said road supervisor Greg St. John. “There is nothing else out there right now that efficiently melts snow,” said St. John. “And the public has an expectation of clear roads.”

Environmentalists also point out that there are chemicals — including industrial waste and runoff of gas, oil, lawn pesticides — that are much more worrisome than salt. Star Ledger.