Thousands of tons of radioactive waste are created every year by Bakken oil development and state health regulators have signed off on a risk assessment study that could allow some of it to be buried in North Dakota landfills.

The $180,000 study by Illinois-based Argonne National Laboratories, followed by any new rules for radioactive waste, will take at least a year to complete, said Scott Radig, director of the state Health Department’s special waste program.

In the meantime, rules will remain as they are now, he said.

Radioactive waste above 5 picocuries per gram can’t be disposed of in any landfill here. The result is that oil field operators truck it to landfills in Colorado, Idaho, Utah and recently Montana. Those states have higher thresholds.

Radig said those states allow from 30 picocuries up to 400.

“We have a very conservative threshold. It’s quite possible that this study will show that the limit can be raised,” he said.

The reason for the study is that naturally occurring, low-level radioactivity in soil formations becomes concentrated on some oil field equipment and waste materials.

Since this is a fairly new phenomenon, health officials wants to know — and so does the oil industry — if it can raise the regulated threshold so more radioactive waste produced here can be buried here.

“This material is generated here and there is risk in transport, as well as handling. The question is how to manage it in as safe a way as possible,” Radig said.

Darrell Dorgan, who heads the citizen-based Energy Industry Waste Coalition, said his group believes the rule shouldn’t change.

“This isn’t a wink-wink game. This is about people’s lives. The oil companies knew the rules before they started drilling,” Dorgan said.

Dorgan said he is pleased the department will wait for the study results before proposing any change.

Argonne said it will identify the exposure risk for people who work in the oil industry and at landfill disposal sites, or live near the landfills

It also will look at the design of North Dakota’s eight oil field special waste landfills and the one industrial waste landfill to determine if any could safely handle radioactive waste.

The Health Department will tell Argonne how much radioactive waste is produced in the oil patch and the level of concentration so it can assess the risk.

Some early numbers are already in.

Radig said the oil industry generates an estimated 7,500 tons of filter socks every year, with average concentrations from zero to as high as 70 picocuries. The socks look like small fishing nets and are used to filter out solids at disposal wells.

One out-of-state company — Clean Harbors of Colorado — said it took in 16,000 tons of oil tank bottoms and filter cake from North Dakota oil operators in the first eight months of 2013.

From samples, the company said that 42 percent of the sludge contained less than 5 picocuries of radioactivity. The remainder was above that — most at 10 to 20 picocuries, Radig said.

Ceramic proppants, which are used instead of sand in some wells to hold open the pressurized hydraulic fractures that allow Bakken oil to flow, have concentrations of 10 to 20 picocuries. Radig said those proppants stay in the wells two miles deep and don’t present a risk for exposure.

Radig said if the regulated threshold is raised next year, landfill operators won’t get an automatic pass.

“It would not be a blanket for all of them. Each one would have to apply for a modified permit,” Radig said.

Theodora Bird Bear, a member of the Energy Industry Waste Coalition, said citizens shouldn’t have to wait until after the study is complete to hear from Argonne.

“If the state … is intending to increase the radioactivity of oil waste in North Dakota, there should be a preliminary meeting on the intent or purpose behind the study,” she said.

Radig said the public would be involved before its rules are changed.

Reach reporter Lauren Donovan at 701-220-5511 or