JUNEAU — Just how much sulfolane is safe has been a simmering battle that heated up when Flint Hills cited cleanup costs in its plan to shut down production at its North Pole refinery.

Sulfolane is a chemical that spilled from the refinery and into North Pole’s ground water before Flint Hills bought the plant.

The state argues just 14 parts per billion of sulfolane is safe for North Pole residents. Flint Hills Refinery says 362 parts per billion, nearly 26 times higher than the state’s level, should be acceptable.

Facing the layoffs of 80 employees and the shrinking of the railroad’s revenues, lawmakers want answers.

On Thursday, the director of the state’s Division of Spill Prevention and Response, Kristin Ryan, defended the state’s decision-making to a House budget committee.

The issue, Ryan said, is little research has been done on sulfolane’s health impacts. It’s known to cause weakened immune systems in lab rats, and chronic exposure can cause problems in the liver and kidneys, but its health impacts on humans are much less clear, especially with long-term exposure.

“There is considerable ambiguity,” she said, “which is why the division has decided to apply so many uncertainty factors to the cleanup level. Because we’re just not sure how it impacts humans, we’re not sure where it’s going and there’s a lot of unknowns still.

“When we don’t know things, we try to err on the side of caution,” she said.

The U.S. Environmental Protection Agency recently completed an analysis of safe sulfolane levels at the request of the state. That finding came in at 16 parts per billion.

Both Flint Hills and the state used the EPA’s research as a starting point to reach their levels, but Ryan said the state used a wider margin of error.

Only three wells in the affected area, which is 3 miles long by 2.5 miles wide and contains  312 affected homes and businesses, would be considered unsafe by Flint Hills’ calculation, Ryan said.

Flint Hills has appealed the state’s safe cleanup levels to the commissioner of the Department of Environmental Conservation. 

The state and Gov. Sean Parnell were initially criticized for what Flint Hills said were too-strict cleanup requirements, but Parnell and the administration stood by its requirements, citing concern for public health.

When asked about the closure, Ryan said she was surprised because Flint Hills will still be required to clean up the site or provide a system for clean water whether the plant is operating or not.

Flint Hills is still under pressure to clean up the spill and has failed in court to get the site’s previous owners, Williams Alaska Petroleum, to pay for the cleanup.

The state is exploring taking its own legal action against the former owners.

Criticism of the state’s science seemed to melt away during the hearing, with lawmakers’ focus shifting mostly to the question of what will be done for the affected North Pole residents.

Ryan said that if Flint Hills eventually finds that it isn’t feasible to clean up the sulfolane spill, then it will be responsible for providing a clean-water distribution system.

One of the most striking comments came from a lawmaker outside the Interior, Anchorage Republican Rep. Lance Pruitt, who asked about the possible legal action the state could take.

“I am very pro-development, but you’re not going to come to my state, rape the land and then leave,” he said. “If they’re responsible, we need to go after them.”

Contact staff writer Matt Buxton at 459-7544. Follow him on Twitter: @FDNMpolitics.