As part of the defense bill signed into law by President Donald Trump on Dec. 20, Energy Secretary Dan Brouillette was directed to report back to Congress within six months on “the status of the Runit Dome in the Marshall Islands” and the dangers posed by potential leaks.

The Runit Dome, sometimes called the “Cactus Dome” and referred to locally as “The Tomb,” was constructed in the aftermath of 43 nuclear weapons detonations conducted by the U.S. military in Enewetak Atoll and nearby atolls between 1946 and 1958.

A section of the fiscal 2020 National Defense Authorization Act also required Brouillette to come up with “a detailed plan to repair the dome to ensure that it does not have any harmful effects to the local population, environment, or wildlife, including the projected costs of implementing such plan.”

In May, United Nations Secretary General Antonio Guterres gave support to the claims of Dr. Hilda Heine, president of the Marshall Islands, regarding risks to the dome from rising waters around Runit Island — a phenomenon she attributed to climate change.

In an address on Fiji following tour of the central Pacific, Gutteres said Heine was “very worried because there is a risk of leaking of radioactive materials that are contained in a kind of coffin in the area” on Runit Island.

“The Pacific was victimized in the past as we all know” by the scores of nuclear weapons tests above ground, on the ground and underwater in the Marshalls, Guterres said.

“The consequences of these have been quite dramatic, in relation to health, in relation to the poisoning of waters in some areas,” he said.

On May 6, 1958, the U.S. set off an 18-kiloton device on a platform at the northern tip of Runit Island, creating a 350-foot wide crater as part of the U.S. military’s Operation Hardtack.

In 1977, the Defense Nuclear Agency began a cleanup of the Enewetak test sites that focused on dumping the waste in the Runit crater.

Over four years, about 4,000 U.S. Army troops dumped 111,000 cubic yards of soil into the crater and covered it up with more than 350, 18-inch thick concrete slabs to form a dome 377 feet in diameter, according to an investigative series by the Los Angeles Times.

The provision in the NDAA calling for an assessment of repairs to the Runit Dome was the result of an amendment to the bill offered in June by Rep. Tulsi Gabbard, D-Hawaii, a contender for the Democratic presidential nomination.

“The Runit Dome, locally called The Tomb, contains 111,000 cubic yards of radioactive nuclear waste created by U.S. nuclear testing during the Cold War,” Gabbard said in a release. “The U.S. government is responsible for this storage site and must ensure the protection of the people and our environment from the toxic waste stored there.”

Editor’s note: This story has been updated to correct the name of the secretary of energy.