5 Things Investigators Say Went Wrong Before Boise Hangar Collapsed

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The catastrophic collapse of a steel airplane hangar at Boise Airport has kept observers busy for months.

Findings released Monday by the Occupational Safety and Health Administration reveal the primary reasons for the construction failure, which killed three workers and injured eight others. Big D Builders, the Meridian contractor that worked on the football-field-sized hangar, ignored visible warning signs and “egregiously” disregarded standard safety procedures during construction, the agency said.

The building collapse on January 31 killed Craig Durrant, co-founder of Big D Builders, and two construction workers, Mario Sontay Tzi and Mariano “Alex” Coc Och.

What OSHA Says Happened

1. No guy lines are installed.

The hangar would be 300 feet long. To build it, Big D Builders planned to place two 150-foot-long sections of steel I-beams parallel to each other and then connect them with structural steel and bracing, David Kearns, director of OSHA’s Boise Area Office, said by email.

As the company built more sections, it became apparent that they were not straight. Instead of installing additional reinforcement or temporary guy lines, as is industry standard, the company left key connecting bolts loose and used ties to straighten them, OSHA said in a news release.

Federal investigators said the company began construction of the hangar without adequate bracing or guy cables, the tensioned cables that provide stability to freestanding structures.

2. Big D ignored signs of instability.

Big D had no plan in place prior to construction to secure the long-span structure, Kearns said in a telephone interview with the Idaho Statesman.

“It’s common practice in the industry to take measures for stability and everything stays good,” Kearns said. “When you get to something of this magnitude, you’re much more likely to have shortcuts come after you.”

Construction workers began adding and connecting the sections on Jan. 29, just two days before the hangar collapsed. According to a citation issued to Big D Builders, workers reported bent trusses, warped columns and numerous broken cables before the accident.

Big D Builders ignored numerous signs that the 43-foot-tall structure was unstable, according to a press release from the U.S. Department of Labor, which includes OSHA. Some of the I-beams were visibly bent, buckled and corrugated.

3. Bolts were not tightened properly.

Investigators found that Big D crews had improperly tightened bolts, including two columns that had none of the 24 bolts tightened, the summons said. At least eight of the 12 required bolts were not tightened on a third column.

During the demolition of the site in June, OSHA investigators returned and found that less than half of the connecting bolts were properly tightened, Kearns said. In almost all cases, the bolts were no tighter than finger tight, he told the Statesman.

“While we can’t say that this was the direct factor that led to the collapse, it is indicative of the types of erections that are being performed there and that we had serious concerns about that,” Kearns said.

4. Employees were not properly trained.

Big D also failed to provide workers with “proper training on the hazards associated with joining,” the lawsuit alleges. “Employees engaged in joining operations were not trained on bolt tightening requirements and methods of tightening.”

The workers also had no training on procedures to ensure the structural stability of the longer trusses supporting the roof, the summons said.

5. The ground was not properly prepared.

OSHA cited Big D for failing to follow proper procedures for the terrain on which its crews were working, exposing workers to the risk of equipment tipping over, the report said.

“A firm, well-graded, drained area was not readily accessible for work with adequate space for the safe storage of materials and the safe operation of the erectors’ equipment,” the complaint states. “Steel erection work occurred in mud and areas of standing water.”

And what about the falling crane?

While OSHA still cannot say for sure what caused the collapse, there is no indication that a crane structure caused the massive steel structure to topple, Kearns said.

What about strong winds?

>Strong winds at or around the time the structure collapsed — measured at speeds in excess of 20 mph with gusts in the 30s — could have been a contributing factor, Kearns said. But they were not considered the cause of the collapse.

“If you had any concerns about structural stability, I’m sure the wind didn’t help,” Kearns said.

Boise State engineer: Evidence points to poor management

Yang Lu, an associate professor of civil engineering at Boise State University and an expert in forensic analysis of collapsed structures, said the OSHA report confirmed what he suspected after news of the hangar collapse broke in January.

“At first I thought it was a quality control issue,” Lu told the Statesman by phone Monday. “It’s one story, right? It’s not a very heavy load, and steel structures are usually pretty strong as long as they’re connected properly. And in terms of the technology, this is a pretty mature design.”

According to Lu, most structural deficiencies that occur during the construction phase are caused by poor management or quality control issues.

He questioned whether the workers on the site were properly trained or licensed to do the type of work they were required to do. He said that structural engineers should have been on the ground to oversee the project.

“It looks like they didn’t install or connect it properly,” Lu said.

What OSHA is Proposing and Why

OSHA recommended fining the company nearly $200,000 for four violations of federal safety regulations. The total fine is one of the largest financial penalties Idaho has seen in recent years, Kearns said.

“No death or life is more valuable than another, but to see so many happening at once, especially when they could have been prevented like in this case, really hurts,” Kearns said.

The regulator also ordered Inland Crane, the Boise contractor that Big D Builders works with, to pay more than $10,000 in fines because the company exposed workers to hazards and failed to ensure the stability of the hangar during construction.

Big D Builders said a lawsuit is pending and it had no comment on the subpoena or OSHA’s findings.

Inland Crane said OSHA’s findings are consistent with its own “initial impression” that neither the company nor its equipment “contributed to the tragic collapse of the hangar.”

But Kearns told the Statesman: “They were there, they were involved, they were very familiar with the buckling and the swaying, the structural issues. They raised concerns, but they took no steps to move workers out of harm’s way. Ultimately, they were very fortunate that they didn’t injure or lose any of their own workers.”

OSHA: Let This Be a Wake-Up Call

Kearns said the preventable January fatal incident and OSHA’s findings should serve as a reminder and a “wake-up call” to contractors in and around the Treasure Valley to follow industry best practices and safety regulations during construction.

“I hope that something good comes out of a tragedy like this, namely that it helps to change their safety practices and improve the culture in the workplace. Safety and health in the workplace are core values ​​for them,” he said.

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