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This story was originally published at Prism.

In Yigo, the northernmost village in Guam, there is a well that cannot be shut down.

Known as Y-15, the well sits atop the island’s northern aquifer, which supplies around 80% of the island’s drinking water. Even if contaminants are detected, Y-15 has to keep pumping. There is simply no alternative.

The well also sits just below a hill near Upi Elementary School — attended by around 400 children — and just outside the back gates of Andersen Air Force Base, which hangs over the community like a permanent shadow. Generations of Indigenous CHamoru families have called Yigo home, relying on these waters for drinking, cooking, and other daily activities.

But in September 2025, one such family learned that the well supplying their home of 17 years was contaminated with high levels of dieldrin, a pesticide once widely used on crops and for termite control beginning in the 1950s. The Environmental Protection Agency (EPA), which classifies dieldrin as a probable human carcinogen, banned all uses of the pesticide in 1987 over concerns about its damage to the environment and links to serious health effects, including cancer, Parkinson’s disease, and reproductive issues such as decreased fertility and increased numbers of stillbirths. Because dieldrin accumulates in the body, long-term exposure — even in small amounts — can cause serious harm, according to the EPA.

More than 1,200 residents of Yigo were told not to drink water from Y-15 because of dieldrin contamination.

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The news hit Leevin Camacho, the homeowner who learned of the contamination, with a mix of anger and fear. He thought immediately of his two young sons. Although members of his family don’t drink straight from the tap, the water touches nearly everything they do: cooking meals, brushing their teeth, showering at the end of long, humid days.

“While we were there feeding our kids, doing a lot of stuff, there was pesticide in the water,” he told Prism in November.

Camacho knew his family could adjust to the “do not drink” order issued by Yigo officials. As a lawyer and former attorney general of Guam who grew up in a military household, he had the resources to install a costly home filtration system or buy bottled water each week. But he worried about everyone else in Yigo — especially fellow CHamorus who, unlike him, didn’t have as many options.

Dieldrin is just one piece of a much larger and troubling environmental legacy in Guam.

Per- and polyfluoroalkyl substances (PFAS) — better known as “forever chemicals” — have also been detected across the island’s water systems. These compounds can persist in soil and groundwater for decades, and they have been linked to a range of health effects, including cancer, immune and thyroid dysfunction, liver and kidney disease, and serious reproductive issues.

For Monaeka Flores, an advocate with the grassroots environmental organization Prutehi Guåhan, the island’s environmental problems are inseparable from the military buildup that has reshaped the island. From hazardous waste dumping, base construction, and open-air detonations of munitions to live-fire exercises in sensitive habitats, advocates say that Guam’s land and water bear the toxic legacy of the U.S. military.

“Questions That We Couldn’t Answer”

In September 2025, local officials gathered Yigo residents at a village gymnasium to share the alarming details of their water’s contamination: Dieldrin at the Yigo well measured 1.76 micrograms per liter — more than eight times the threshold that Guam EPA considers within the acceptable cancer-risk range. Two other wells on the island also showed elevated levels of the pesticide, though not as high as the one in Yigo. Unlike Y-15, these two wells were shut down.

Once the information was made public, Yigo Mayor Frances Lizama said her phone rang nonstop.

“A lot of the calls were about health, about when we are going to get our safe drinking water — questions that we couldn’t answer,” Lizama said during an interview at her office late last year.

The discovery also raised questions about the timing of when residents were told dieldrin was in their drinking water.

Dieldrin has been detected in Guam’s groundwater for years. In 2012, the EPA notified Guam authorities of its presence in several wells. But because dieldrin is not federally regulated in drinking........

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