County planners have recommended approving the Big West of California refinery expansion after a last-minute analysis showed the use of a controversial chemical there is safe.

After consulting with refining experts, planners said the occasional use of a low concentration of hydrofluoric acid at the facility should be allowed to continue. However, they suggested any other use of the chemical at the facility be prohibited.

“We feel this is a safe process,” said Kern County Planning Director Ted James. “We’ve concluded the use of this acid at such as low (concentration) is appropriate.”

The $700 million expansion will go before the Board of Supervisors Tuesday for final approval.

Big West’s hard-won support for the project hung in the balance last week after it was revealed that a solution containing 1 to 5 percent HF is used to service the facility’s injection wells.

Big West had initially proposed to use pure HF in the expansion but faced major opposition from community groups and politicians due to its hazards.

In pure form, HF poses serious risk due to its ability to vaporize when spilled, forming a toxic cloud that can spread to surrounding areas. In recent weeks, the company agreed to an alternative expansion plan that doesn’t use the chemical.

After learning that a low concentration of HF was already in use at the facility, Supervisor Mike Maggard called a news conference and accused Big West of not being “truthful enough” with the public.

The head of a community group that praised Big West’s decision not to use HF in the expansion also said she felt betrayed.

Big West officials said the HF solution is used by a contractor that services wells at the refinery a few times a year. Unlike pure HF, the diluted form cannot vaporize and form a toxic cloud.

“It really is a totally different kind of HF acid use because it’s only 5 percent and it’s in an aqueous solution,” said Big West Health, Safety and Environmental Director Bill Chadick.

Kern County Environmental Health Director Matt Constantine confirmed that the risks of aqueous HF were not as serious as pure HF.

Still, county planner Lorelei Oviatt said Big West should have been up front about the chemical’s use. Oviatt said she repeatedly asked refinery officials if HF is in use or being tested at the facility and they said no. Under state environmental review laws, the public had a right to know about the chemical’s use, she said.

“We rely on (Big West) to tell us about their project,” Oviatt said. “They didn’t understand the extent to which they needed to describe what they do so we could tell that to the decision-makers and the public.”

Chadick said the environmental review process doesn’t require the company to conduct risk assessments on every chemical it uses. Because of the low risk of aqueous HF, the company didn’t think it was worth the effort to analyze its dangers, he said.

Maggard said Monday that he remained concerned about Big West’s ability to communicate important issues to the community. He plans to propose additional measures today to ensure the company acts transparently.

“The issue for me was never the fact that the diluted mixture is not manageable,” Maggard said. “The issue is they need to fully cooperate and disclose when we make inquiries of them.”