It’s impossible to discuss Long Island’s groundwater without addressing Northrop Grumman.
The Long Island aeronautics industry was a key asset to the United States armed forces in the last century, testing and manufacturing nearly 30,000 airplanes for the U.S. Navy starting in the 1930s, and later producing the lunar module for Apollo 11’s landing on the moon. For over 50 years, the Northrop Grumman Bethpage Facility and Naval Weapons Industrial Reserve Plant Site was at the center of American defense and innovation — and one of the largest chemical contamination sites in New York.
According to the state Department of Environmental Conservation, the degreasing agent trichloroethene leaked from NWIRP’s plumbing and dumping sites into the Magothy Aquifer — which provides water to much of Nassau County — creating the Navy Grumman groundwater plume.
The plume is a two-mile-by-four-mile body of TCE with the potential to leach into Long Island’s South Shore waters and the Great South Bay, according to Jason Pelton, director of Remedial Bureau D in the DEC’s Division of Environmental Remediation.
“As plumes go, it’s probably the largest in New York state,” Pelton said. “It may be one of the largest in the country.”
Bethpage’s tarnished legacy
Shortly after the plume was identified in 1983, the DEC formed a partnership with both the responsible parties, the Navy and Northrop Grumman, to begin restoration efforts. The two groups operate extraction wells, large structures that siphon water out of the aquifer, filter out TCE, and send the water back underground by way of recharge basins.
“I’ve been very impressed with the Navy and Northrop Grumman’s ability to locate these wells precisely where they need to be, and to see the contaminant numbers that are coming out in these locations,” Kristin Granzen, DEC project manager for the U.S. Navy Bethpage site, said.
The joint cleanup effort processes about 10 million gallons of contaminated water per day, according to DEC documents provided to the Herald. The agency estimates that about 80 percent of the contamination — 276,000 pounds — has been removed from the Magothy Aquifer and destroyed in chemical reactions or captured in granulated carbon, preventing any future leaks.
The DEC’s 2019 Record of Decision was the first formal plan for cleaning up the site. Before then, there were around 10 extraction wells in the affected area. Since the ROD, the number of wells has risen to 26, supported by five water-treatment plants. The aggressive plan to stop the plume’s southward migration was motivated by the DEC’s zero-tolerance attitude toward chemical contamination, Pelton said.
“Groundwater exists in these voids between grains of sand and soils in what we call pore spaces,” Granzen explained. “Water moves in between those pore spaces. When the contaminants get mixed with the groundwater, that causes movement.”
“The water districts should not have to address this,” Pelton said. “That’s the primary driver here: removing the TCE from the aquifer system so that we’ve got a better drinking water source.”
The DEC’s goal is to reduce the aquifer’s TCE levels to 5 parts per billion, the groundwater safety standard, though much of the plume’s area is still over 50 ppb, according to DEC map data from May 2025.
“The fact that it’s predominantly TCE makes it a little bit easier,” Pelton added. “The challenge is the magnitude of the contamination … I would say maybe we’re pumping in the interior of the plume for 30 or 40 more years.”
Chemicals linger, at what cost?
While the cleanup continues, the plume’s public health effects have been a topic of endless discussion. Its cleanup is made possible by collaboration with local municipalities, home to the county’s hundreds of monitoring wells collecting data on groundwater. They are a strict quality-control measure assessing whether the water is safe to consume or to use in irrigation.
Kevin Reilly, who oversees the monitoring of the Massapequa Water District as its superintendent, told the Herald that if the chemicals posed no real health risks to the community, there would be no need for the decades-long cleanup effort. The district serves parts of Massapequa, Massapequa Park and North Massapaqua, all areas just south of Bethpage, where the plume originated.
After filtration, there are no risks to residents’ health, the DEC maintains. “I would say the overall health of the aquifer is healthy,” Pelton said. “It’s important that people know that their drinking water is really high quality, and it’s absolutely safe to drink that water.”
According to a chemical profile from the Agency for Toxic Substances and Disease Registry, a division of the Centers for Disease Control and Prevention, TCE can be a carcinogen with high exposure, and the state Department of Health conducted an environmental health investigation in Bethpage, finalized in 2013, on whether long-term exposure to contamination from the sites had affected local cancer rates.
According to the department’s report, there was no correlation between the presence of TCE in the aquifer with cancer rates on Long Island. The most commonly diagnosed cancers in the areas affected by the plume were those typically seen most often in adults, and no single rare cancer type appeared more than once. Most diagnoses occurred at ages when cancer is generally most common. There was no indication that the cancers were linked to environmental findings.
The health department continues routine monitoring of drinking water and remediation efforts to protect public health as the cleanup progresses.
At the request of the Bethpage community, the department is revisiting the 2013 study, and its work is expected to be completed by the end of this year. In a written statement, the department told the Herald that the update cannot provide a direct link between cancer cases and environmental exposure, including the plume. Evaluations of environmental exposure can draw some health associations, but they cannot determine causality.
“There is no new threat to public health, and prior exposures have been addressed for more than a decade due to the efforts of New York State,” the statement read. “The Department is currently working on the study and upon completion of the report will announce findings and host a public meeting.”
The race against the spread
The state continues its effort to clean up the plume while keeping the affected communities informed. The DEC facilitates regular community meetings through its Community Participation Working Group, comprising elected officials, agencies, businesses and experts that meet on a quarterly basis. The group was established to foster dialogue, improve public understanding, and encourage discussion of the cleanup.
The DEC staff also provides regular project updates at Bethpage Community Council meetings, which are held at the Bethpage Public Library and open to the public.
According to the DEC’s January Groundwater Plume Cleanup Update, public water suppliers treat groundwater using established methods to contain regulated contaminants before they reach homes and businesses. Water is drawn from designated sources, treated to meet all federal and state drinking water standards, and distributed through a network of mains and storage tanks. Throughout the process, water quality is continuously monitored to ensure that it remains safe to drink.
“We work really closely with the water districts in Nassau County,” Pelton said. “Every single day they provide high-quality drinking water that meets all of the New York State Department of Health drinking water requirements.”
The system relies on multiple safeguards to maintain high water quality and protect public health. This approach ensures that if standards are not met, suppliers notify customers and take corrective action, which can include temporarily taking wells out of service.
Negotiations among public water suppliers, the DEC, Northrop Grumman and the Navy have focused on funding the treatment systems used to maintain safe drinking water. The Bethpage Water District, for example, operates treatment systems that are considered among the most advanced in the nation, according to the DEC.
Though it is currently not affected, the Massapequa Water District is just outside the current spread of the plume. “We are not an active part of the cleanup yet,” Reilly said. “We monitor — there’s monitoring wells that we get the data from the Navy and their consultants and the DEC. But we don’t have any contamination in our wells from the Grumman Navy plume at this time.”
Common misconception has led many Long Island residents to believe the entirety of the South Shore has been impacted, which is not the case. Nonetheless, Reilly said, “The plume is migrating and flowing towards our district.”
He explained that while large-scale, permanent systems for treating the underground water are currently under construction, temporary systems have been installed along the leading edge of the plume. They operate on a smaller scale, but they are designed to be mobile, and can be relocated as needed to respond to changing conditions while the permanent treatment infrastructure is being completed.
“The water districts to the north of us are already treating their wells for the contaminants, and they’ve spent millions upon millions of dollars to get these treatment systems in place,” Reilly said. “We haven’t had to do that yet — we’re watching. We don’t want to have to do that, and we’re constantly involved in pushing to get these Navy treatment systems up and running, to treat the groundwater.”
Northrop Grumman did not respond to requests for comment.
The plume persists — but containment continues
The Navy Grumman groundwater plume is a case study that shows local governments and corporations working together to protect communities. The plume’s development and spread also show that the consequences of a mistake can be challenging to deal with, and that decades of damage require as much or more time to repair. The DEC’s expertise, Northrop Grumman and the Navy’s willingness to take responsibility, and the help of local water districts, were essential in making the restoration effort possible.
The public can receive updates about the plume cleanup effort at the DEC’s Bethpage Community Council meetings at the Bethpage Public Library, the Navy’s semi-annual Resident Advisory Board meetings online at NAVFAC.Navy.Mil/Divisions/Environmental, and Northrop Grumman’s website, NorthropGrumman.com/Sustainability.
