In 1977, the U.S. buried 2.8 million cubic feet of radioactive waste in a Pacific ‘nuclear tomb.’ Nearly 50 years later, the ocean is threatening to expose the Runit Dome.

Surrounded by turquoise waters and coral reefs in the remote Pacific Ocean sits a little-known concrete structure that remains one of the world’s most controversial nuclear waste sites.

Known as “The Tomb” or the Runit Dome, the circular concrete cap measures 377 feet in diameter and is 18 inches thick. For nearly half a century, it has attempted to contain one of the most hazardous remnants of the Cold War.

A Cold War legacy

To understand how the dome came to exist, it’s necessary to go back to the 1940s and 1950s.

During the nuclear arms race with the Soviet Union, the United States selected the Marshall Islands as its primary nuclear testing ground. In total, 67 nuclear tests were carried out in the region, with 43 detonated at Enewetak Atoll, where the Runit Dome is located.

Among them was the devastating Castle Bravo test at neighboring Bikini Atoll, a hydrogen bomb roughly 1,000 times more powerful than the atomic bomb dropped on Hiroshima.

The repeated tests vaporized entire islands, forced local communities from their homes, and blanketed both the land and seafloor with radioactive fallout.

A giant concrete patch

By the late 1970s, amid growing international pressure and demands from displaced islanders, the U.S. government launched a cleanup operation.

Military engineers removed contaminated topsoil, radioactive ash, vegetation and abandoned military debris from across the atoll.

The material was then dumped into the 328-foot-wide Cactus Crater, created by the 1958 Cactus nuclear test on Runit Island.

Finally, workers covered the crater with 358 massive concrete panels, creating the dome that remains today.

But the project contained a critical flaw.

To reduce costs, engineers never sealed the bottom of the crater. Instead of installing an impermeable barrier, they assumed the atoll’s natural rock would prevent radioactive material from escaping.

The assumption proved incorrect.

Unlike solid granite, an atoll is built on porous coral limestone, allowing seawater to move freely through the ground.

Rising seas threaten the structure

Nearly five decades later, time and climate change have exposed the dome’s weaknesses.

Scientists have identified cracks in the concrete cap, water infiltration through the coral beneath the crater and growing concerns over rising sea levels, all of which threaten the long-term stability of the site.

Buried beneath the structure are an estimated 2.8 million cubic feet of radioactive waste, equivalent to roughly 120,000 tons of contaminated material.

The debris includes radioactive ash, contaminated soil, vegetation, military scrap and concrete rubble.

Experts are particularly concerned about plutonium-239, an extremely toxic radioactive isotope with a half-life of more than 24,000 years.

Scientists raise the alarm

The dome’s deteriorating condition has increasingly alarmed researchers.

“The dome was essentially a temporary fix that was never designed to last,” marine physicist Ken Buesseler of the Woods Hole Oceanographic Institution has warned.

“Seawater is literally flowing through the radioactive waste.”

Michael Gerrard, director of Columbia University’s Sabin Center for Climate Change Law, has also questioned the dome’s long-term viability.

“The bottom of the dome is simply the crater left by the explosion,” Gerrard said.

“There is no impermeable barrier underneath, so as sea levels rise, the Pacific Ocean is already washing through the inside of the tomb from below.”

Dispute between the United States and the Marshall Islands

The deteriorating structure has become the center of an ongoing dispute between the governments of the Marshall Islands and the United States.

Officials in the Marshall Islands have called for a long-term containment plan or for the radioactive waste to be removed entirely and transported to the U.S. mainland.

Washington, however, has long maintained that responsibility for maintaining the structure was transferred to the Marshall Islands following the country’s independence agreements in the 1980s.

Today, the Runit Dome still sits silently in the middle of the Pacific.

It remains a concrete reminder of the nuclear age and of a lesson that continues to resonate decades later: humanity may be able to bury its most dangerous mistakes beneath thousands of tons of concrete, but the ocean has a way of finding every crack.

Get closer to the game! Whether you like your soccer of the European variety or that on this side of the pond, our AS USA app has it all. Dive into live coverage, expert insights, breaking news, exclusive videos, and more. Plus, stay updated on NFL, NBA and all other big sports stories as well as the latest in current affairs and entertainment. Download now for all-access coverage, right at your fingertips – anytime, anywhere.

And there’s more: check out our TikTok and Instagram reels for bite-sized visual takes on all the biggest soccer news and insights.