Road salt blamed for contamination that could take NYC's reservoirs out of commission

NEW YORK - The suburban reservoirs that supply 10% of New York City's vaunted drinking water are getting saltier due to decades of road salt being spread near the system — and officials warn that they will eventually have to be abandoned if nothing is done to reverse the trend.

The New York City Department of Environmental Protection’s "Salinity Management Assessment" study reviewed nearly 33 years of data and found steadily increasing salinity levels in all 12 reservoirs and three controlled lakes in the water supply’s Croton System.

New York City’s drinking water getting saltier

The study, published on March 21, found that the plug wouldn't have to be pulled until early next century, but the soaring saltiness could eventually affect the famous taste of the Big Apple’s water, which is sometimes referred to as the champagne of tap water, and poses a challenge to managers of a system that serves more than 9 million people.

What they're saying:

"The conclusion of this study is that if we don’t change our ways, in 2100 the Croton Water System becomes a nice recreational facility, but it ceases to be a water supply," Rohit Aggarwala, the city’s environmental protection commissioner, said in an interview with The Associated Press. "And that will directly impact everybody who drinks New York City water."

The report also found that salinity levels in the system’s main New Croton Reservoir have tripled in just a 30-year time frame.

A view of the Croton Gorge Park, a 97-acre property at the base of the Croton Dam in New York City (Credit: Fatih Aktas/Anadolu Agency via Getty Images)

The report noted salinity increases across the sprawling system of city reservoirs in upstate New York. However, the problem is far less of an issue in the Delaware and Catskill watersheds west of the Hudson River, which supply about 90% of the city’s water. That’s likely because there’s far less development in those watersheds. 

Road salt main issue 

Dig deeper:

The Croton system dates back to 1842, when the first Croton Aqueduct began delivering water to a reservoir in what is now Manhattan’s Central Park.

Road salt is considered a main driver of the increase, along with sewage treatment plant discharges and water softeners. Millions of tons of rock salt are spread on U.S. roads each winter as a cheap and effective way to reduce accidents.

What they're saying:

"It's really a problem across the country in areas with a lot of snow," said Shannon Roback, science director for the environmental group Riverkeeper. "We’ve seen rising levels of salt in water in the Northeast, in the Midwest and in most places that use road salt."

How to reduce salinity

Roback noted that high salt levels in drinking water pose a host of environmental concerns and can be harmful to people on low-sodium diets.

What's next:

The study found winter de-icing of roadways and parking lots, wastewater treatment plant discharges and private water softening systems as likely main contributors to increased salinization. Water filtration plants cannot remove salt from water. Instead, salinity can only be reduced through a costly and heavily energy-dependent desalinization process.

Recommendations to reduce salinity included developing practices for reducing man-made salinity contributions throughout the water supply region, expanding studies on specific sources, and building public awareness to the trends and impacts of salinity infiltration of fresh water supplies.

Aggarwala also said the city has a few options.

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Salt can be removed from water supplies through reverse osmosis systems, though the technology is expensive and requires a lot of energy. The city also could mix Croton water with less salty water from its other two watersheds. But the commissioner said that would not be a solution for the more than a dozen municipalities north of New York City that draw water from the Croton system.

City officials believe reducing the use of road salt locally is the most sensible option. That could involve persuading state and local road crews to use alternatives to salt, or sensors on plows to gauge road surface temperatures, or shutting off the applicators when plows make U-turns or K turns.

State Sen. Pete Harckham, who represents the area, called the new report alarming, but not surprising given a number of community wells taken offline due to high chloride levels. The Democrat is sponsoring bills that would address the road salt issue, including one that would study the issue in the Croton watershed.

"State agencies, local governments, everyone needs to come together on this," he said, "because this is a real challenge."

DEP manages New York City’s water supply, providing more than 1 billion gallons of high-quality drinking water each day to nearly 10 million residents, including 8.8 million in New York City and 1 million more in counties north of the City. The water is delivered from a watershed that extends more than 125 miles from the City, comprising 19 reservoirs and three controlled lakes.