February's record-breaking snowfall is delaying demolition at the Husky Energy refinery in Superior, which needs to be largely rebuilt after an explosion and asphalt fire severely damaged the facility in April 2018.

"They're just covered in snow right now, but we'll get demolition going when that gets better," Jeff Rinker, Husky's senior vice president for downstream, said in a conference call with investors Tuesday morning.

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The Calgary-based oil company is developing engineering plans for the refinery's rebuild and expects construction to begin later this year, Rinker told investors. The company still plans on a 2020 restart, Rinker added.

On April 26, 2018, an explosion within the refinery's fluid catalytic cracking unit sent a piece of shrapnel into an asphalt tank, causing asphalt to pour out, ignite and burn for most of the day. The incident injured 36 refinery workers and led to the evacuation of much of Superior.

Asked by an investor what changes the refinery rebuild would bring, Rinker said the output - 50,000 barrels per day - would remain the same, but newer equipment would help make the refining process more efficient.

"Largely the refinery is being rebuilt in the same configuration as it was before the incident," Rinker responded.

But that doesn't mean a decision has been made regarding the future of hydrogen fluoride at the refinery, Husky spokesperson Mel Duvall told the News Tribune in an email Tuesday.

"Jeff (Rinker) was referring to the fact that the refinery will be rebuilt in the same 50,000 bbls/day processing configuration that it was in before the fire," Duvall said. "He was not referencing a decision on hydrogen fluoride. That decision has not yet been made."

A timeline on the hydrogen fluoride decision has not been set, Duvall said.

Since the blast, the refinery has faced public opposition to its use of hydrogen fluoride, a potentially dangerous chemical used in the refining process.

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.

While no hydrogen fluoride was released during the incident and the fire never reached the hydrogen fluoride, which was 150 feet away from the fluid catalytic cracking unit - the location of the explosion - shrapnel from the explosion was flung 200 feet, the U.S. Chemical Safety and Hazard Investigation Board said in an Aug. 2 factual update in Superior.

In that same factual update, the board blamed a worn valve for as letting air into the system and mix with concoction of chemicals, creating an explosive mix that then contacted an ignition source.

In separate reports, the Occupational Safety and Health Administration and board both said a process hazard analysis - a document explaining risks involved in an industrial process and operating procedures - failed to address what might happen if the valve was open, but not what would happen if the valve was closed but unable to hold a seal.

The board, a federal agency which doesn't issue fines or citations, but does make recommendations, is still investigating the incident and is set to release its final report and recommendations in several months.

"They are still hoping to meet a late spring/early summer release for the final report," board spokesperson Hillary Cohen told the News Tribune earlier this month.