In a Sept. 26 letter, the Democratic lawmakers —  Rep. Betty McCollum, Rep. Rick Nolan, Sen. Tina Smith and Sen. Amy Klobuchar of Minnesota and Sen. Tammy Baldwin of Wisconsin — asked the board to consider hosting hearings in response to the April 26 explosion, which caused 36 injuries and the evacuation of much of Superior.

Citing the Board’s investigation, the lawmakers said debris could have hit a hydrogen fluoride tank 150 feet away and called the caustic chemical a “great public risk to the Twin Ports metropolitan area.”

“As the board investigation continues, our request for a full public meeting would allow input from the refinery communities about the scope of the board’s investigation of the Husky Refinery accident,” the lawmakers wrote.

Breathing in hydrogen fluoride at high levels, or in combination with skin contact, can cause death from an irregular heartbeat or from fluid buildup in the lungs. A News Tribune investigation found the chemical threatens a 25-mile radius surrounding the refinery under a worst-case release scenario. The April 26 evacuations were based on the risk of a hydrogen fluoride release.

The refinery can handle about 78,000 pounds of hydrogen fluoride, according to federal EPA records from 2012, but it contained about 15,000 pounds of the chemical at the time of the fire. The fire never reached the hydrogen fluoride, which was 150 feet away from the fluid catalytic cracking unit — the location of the explosion — but shrapnel from the explosion flew 200 feet, the Board said in an Aug. 2 factual update in Superior.

The Twin Ports Action Alliance, a group demanding the Husky refinery stop using hydrogen fluoride, thanked the lawmakers in a news release Wednesday.

“It is crucial that Superior and Duluth … be allowed to give testimony at a public hearing of the (Chemical Safety Board’s) findings, as it is these communities that are at risk in the event of future disasters at the refinery, and it is these communities that bear the burden of the refinery’s operations,” the Action Alliance said.

In an email to the News Tribune on Wednesday afternoon, Board spokesperson Hillary Cohen said the Board has received the letter but did not say whether the board will host a hearing.

“The CSB is in the process of reviewing the letter and will have a plan on how we will be moving forward shortly,” Cohen said.

Husky spokesperson Mel Duvall said the company has seen the letter.

“We are aware of the letter and have been working cooperatively with the CSB. We will continue to do so as they carry on their investigation,” Duvall said.

In the letter, lawmakers point out that both Superior Mayor Jim Paine and Duluth Mayor Emily Larson called on Husky to stop using hydrogen fluoride and have asked for the company to adopt an safer alternative chemical when the refinery rebuilds.

When asked if Husky could comment on the future use of hydrogen fluoride at the Superior refinery, Duvall said, “We are not yet at a stage to be able to do so.”