Four Hawaii Island residents filed petitions challenging the radiation monitoring plan for Pohakuloa Training Area.

The plan is the result of the U.S. Army’s use of depleted uranium — a dense, weakly radioactive metal alloy — in spotting rounds fired 50 years ago at PTA, Schofield Barracks on Oahu and mainland installations. It requires sampling of an intermittent stream bed downslope of the impact area.

Studies and monitoring efforts done over the past decade haven’t shown a health risk to Hawaii Island residents as a result of depleted uranium use and ongoing training. But petitioners say they want to see more monitoring, including continued air sampling, a citizen advisory panel or cleanup of the impact area at PTA.

“I am deeply concerned by the potential contamination of our air, fresh water resources, and food sources,” Hawane Rios of Waikii Ranch said in her request for a hearing to the U.S. Nuclear Regulatory Commission. “… As a kanaka maoli and Kia‘i Mauna (mountain guardian), it is my responsibility and birthright to show up, stand up and speak up when my lands and ancestors are calling me to do so.”

The NRC issued the Army a license to possess depleted uranium in 2013 to cover its use of the spotting rounds for the Davy Crockett tripod-mounted gun in the 1960s. The metal was used to give the rounds sufficient weight to simulate the projectile’s trajectory. The monitoring plan is a requirement of the license.

“We’ve done our part in submitting our recommendations to the Nuclear Regulatory Commission,” PTA Commander Lt. Col. Christopher Marquez said in a statement. “The NRC decides whether the Army’s proposal is satisfactory or if something different is required. Our responsibility is to obey the law and comply with the NRC’s decision.”

PTA spokesman Eric Hamilton said high explosives are not used in the radiological control areas where spotting rounds were fired.

NRC spokeswoman Maureen Conley said the petitions filed by the four residents were referred to the Atomic Safety and Licensing Board.

“The ball is now in the panel’s court,” she said in an email. “Typically the process involves putting together a board comprised of administrative judges who will consider whether the petitioners have standing and have put forth admissible contentions.”

According to the Army, 140 kilograms of depleted uranium were confirmed to have been shipped to Hawaii. That would fit in a 10-inch by 10-inch by 20-inch box, according to Marquez.

Those shipments became known after tail assemblies of the rounds were found at Schofield in 2005 and subsequently at PTA, a 133,000-acre training area located off Saddle Road between Mauna Kea and Mauna Loa.

Since then, studies have been done by multiple agencies and the Waikii Ranch Homeowners Association. None have identified higher than normal radiation levels.

Waikii Ranch is the closest community to the training area.

“The level of DU in the dust sample is so low as to be statistically insignificant,” David Bigelow, Waikii association depleted uranium program manager, wrote to members in 2008. “… From this we conclude that we have not been exposed to DU.”

Depleted uranium is 40 percent less radioactive than uranium, which occurs naturally in the environment.

Jeff Eckerd, state Department of Health radiological branch manager, said the stream bed, which is dry except for periods of rainfall, is a more likely pathway for migration of depleted uranium since the heavy metal would likely only travel a couple hundred yards if aerosolized through use of high explosives in the impact area. Depleted uranium is 60 percent heavier than lead, he said.

Jim Albertini of Kurtistown, who has organized protests of PTA, said the monitoring plan and past surveys have been insufficient or faulty. He said the depleted uranium fragments should be cleaned up.

“How much DU was used we don’t know,” Albertini said in an email.

Hamilton said there is unexploded ordnance in the impact area, so it’s not safe to send people.

It’s not known how many spotting rounds were used at PTA versus Schofield.

A 2011 report commissioned by the Army Corps of Engineers looked at the possibility of depleted uranium becoming aerosolized due to use of high explosives in the training area. It stated that under the worst-case conditions, airborne concentrations at PTA boundaries would be well below health guidelines.

The report also notes 714 spotting rounds were confirmed to have been shipped to Hawaii but, 2,050 would have been needed to meet training requirements during the six-year program. The report said it modeled both scenarios and assumed all the rounds were used at PTA.

The plan doesn’t involve additional air monitoring, a point noted by petitioners.

“The current proposed 1 site sediment sample miles northwest of the impact area, taken every several months, weather permitting, is completely unsatisfactory,” Albertini said in his petition.

Albertini said the whole training area should be surveyed, and PTA, which includes federal and some state land, should be returned to the “Hawaiian people, and the restored nation of Hawaii.”

Past air sampling was done by a consultant for the Army at three locations along Saddle Road and the state health department in Waikoloa Village.

Samples taken near Saddle Road in 2009 and 2010 were well below health guidelines, according to the reports. That included periods where live-fire training occurred.

Air sampling in Waikoloa from February 2009 to May 2009 found normal background levels of natural uranium, according to the Health Department.

Eckerd said he doesn’t think additional air sampling would find anything based on the past samples.

“I haven’t seen anything in any of our surveys that would indicate anything other than naturally occurring radiation,” he said. “… The question becomes: How much is enough?”

Other reports include a consultation by the U.S. Department of Health and Human Services. That agency said no adverse effects for the public were expected.

Other petitioners are Cory Harden and Ruth Aloua.

Harden said in her petition that the radiation monitoring plan assumes depleted uranium fragments are only within the radiological control areas, which consist of firing ranges the Army says were used for the spotting rounds.

“It does not take into account fire tornadoes, dust storms, and other high-wind events that may carry dust long distances,” she wrote.

The Health Department continues radiation surveys outside PTA on a periodic basis, even though readings have not found elevated radiation levels, Eckerd said. Those involve use of hand-held detectors, rather than collecting air samples.

“What we’re really looking for in the ambient surveys if there’s any dispersal on the ground,” he said. “If something came off site and is there now.”

“Everything has been within ambient, what we would deem to be normal radiation levels,” Eckerd said.

Since depleted uranium is weakly radioactive, the main health concerns comes from its toxicity, he said. The risk is generally the same for ingesting naturally occurring uranium, also weakly radioactive, Eckerd said.

“It’s more of a chemical hazard (through ingestion) than a radiation hazard,” he said. “Heavy metal poisoning would be more of an issue before you had long-term chronic health effects from the radiation. I would be more concerned with it as a heavy metal toxin or poison.”

Eckerd said he hasn’t seen evidence of depleted uranium migrating offsite from PTA. He said residents shouldn’t be concerned with driving on Saddle Road.

Email Tom Callis at tcallis@hawaiitribune-herald.com.