Likely carcinogen 1,4-dioxane found in Liberty Water's Merrick district

Tests of drinking water from two wells in Liberty New York Water’s Merrick district identified the chemical 1,4-dioxane at levels exceeding the state’s standard of 1 part per billion, according to a notice the company sent to all 45,000 Merrick customers in late August.

The district includes Merrick, Bellmore, Wantagh, Seaford and parts of Levittown and Massapequa. Wells 3A and 4 at the Seaman’s Neck Road plant in Seaford are affected. At the levels detected at the wells, “exposure from drinking water and food preparation is well below 1,4 dioxane exposures associated with health effects,” Liberty said. 

“We want to assure our customers that the water being produced at the Seaman’s Neck plant continues to be acceptable for all uses," John Kilpatrick, director of engineering at Liberty, said in an Oct. 12 statement.

In its notice to customers, Liberty said it would use a "last on, first off sequence to minimize exposure to the chemical," which typically means the company would use water from unaffected wells before relying on affected ones. The company said it is working with Nassau County's health department on "a compliance schedule that includes steps to reduce levels of 1,4 dioxane."

1,4-dioxane, considered a likely human carcinogen by the U.S. Environmental Protection Agency, has been used as an industrial solvent, and in adhesives, ink and spray polyurethane foam. Decades of dumping, leaking and spilling from industrial sites across Long Island have allowed the chemical to seep into groundwater.

In 2020, the state Department of Health established a “maximum contaminant level” for 1,4-dioxane in drinking water of 1 ppb, a standard intended to be “protective,” according to the department’s website. That means “the risk for health effects if someone drinks water at or below the MCL is minimal.” A test showing levels that exceed the maximum level generally “does not mean that water is unsafe for use while the public water system takes actions to reduce the levels,” according to the health department. 

But Adrienne Esposito, executive director of Citizens Campaign for the Environment, based in Farmingdale, said, "These drinking water standards are established to protect public health. If it's above the drinking water standard, it's a concern."

All water systems in the state — public and private — must test for 1,4-dioxane and about 100 other contaminants.

Liberty, a private supplier, serves about 45,000 customers in the Merrick operating district via 16 wells, including the two at Seaman's Neck Road. The district is one of many in New York that have been granted temporary exemptions from meeting the legal standard, allowing providers to avoid fines as long as they take mandatory steps to come into compliance and meet the deadlines established by the health department. Fines can vary but cannot exceed $25,000 per day. 

Compliance can take time: 1,4-dioxane cannot be removed with the carbon filtering methods that are effective for PFAS, heavy metals, and other contaminants. Instead, wells that exceed allowable limits have been outfitted with a relatively new technology — the “advanced oxidation process” which uses hydrogen peroxide and ultraviolet light to reduce 1,4-dioxane to undetectable levels.

AOP systems are operational on nearly 30 wells in Long Island, according to James Neri, spokesman for the Long Island Water Conference and senior vice president of H2M architects and engineers. Dozens more are being designed and constructed.

Liberty's AOP facility at its Seaman’s Neck Road plant is expected to be running by the summer of 2024, according to a company official’s testimony submitted to the state Public Service Commission in May.  

The machinery is expensive, and some water districts are raising their rates to cover their costs. In May, Liberty applied for rate increases across Nassau County, including a 42% increase for the Merrick district, which would mean the average residential customer would pay $15.74 more a month, as Newsday previously reported.