Warning signs ignored: 5 things investigators say went wrong before Boise’s hangar collapse

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The catastrophic collapse of a steel aircraft hangar at the Boise Airport has puzzled observers for months.

Newly released findings Monday from the Occupational Safety and Health Administration reveal key reasons for the structure’s failure, which killed three workers and injured eight others. Big D Builders, the Meridian contractor working on the football-field sized hangar, ignored visible warning signs and exercised “blatant disregard” for standard safety procedures during its construction, the agency said.

Killed in the Jan. 31 structure collapse were 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. Guy lines weren’t installed.

The hangar was to span 300 feet. To construct 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 clear they weren’t straight, and rather than installing additional bracing or temporary guy lines, as is the industry standard, the company left critical connecting bolts loose and used straps to help straighten it, OSHA said in a news release.

The federal investigators said the company began building the hangar without sufficient bracing or guy wires, the tensioned cables that add stability to freestanding structures.

2. Big D ignored signs of instability.

Big D made no plan prior to construction to secure the large-span structure, Kearns said in a phone interview with the Idaho Statesman.

“It’s industry practice to take steps for stability and everything remains plumb,” Kearns said. “When you get to something of this size, shortcuts are going to be much more likely to come back and haunt you.”

Construction crews began adding the sections and connecting them on Jan. 29, just two days before the hangar collapsed. Before the accident, workers reported bent rafters, crooked columns and numerous snapped cables, according to a citation issued to Big D Builders.

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

3. Bolts weren’t properly tightened.

Investigators found that Big D crews had failed to properly tighten bolts, including two columns in which none of the 24 bolts were tightened, according to the citation. At least eight of the 12 bolts needed were not tightened on a third column.

During demolition of the site in June, OSHA investigators returned and determined that less than half of the connecting bolts had been properly tightened, Kearns said. In almost every case, the bolts were no better than hand-tight, he told the Statesman.

“While we can’t say it was the direct factor that led to the collapse, it’s an indication of types of erection being done out there and some serious concerns that we had about that,” Kearns said.

4. Employees weren’t properly trained.

Big D also failed to provide employees with “proper training in the hazards associated with connecting,” according to the citation. “Workers engaged in connecting had not received training to include bolt tightening requirements and torquing methods.”

Nor had employees received training in procedures to ensure structural stability of longer-than-normal rafters that support the roof, according to the citation.

5. The ground wasn’t prepared properly.

OSHA cited Big D for failing to follow proper procedures for the ground that crews were working on. That exposed workers to the risk of equipment overturning, according to the report.

“A firm, properly graded, drained area was not readily accessible to work with adequate space for the safe storage of materials, and the safe operation of the erectors equipment,” the citation said. “Steel erection work occurred in mud and areas of standing water.”

What about the toppling crane?

Although OSHA still cannot affirmatively say what led to the collapse, there is no indication that it was a construction crane that toppled the massive steel structure, Kearns said.

What about high winds?

High winds at or around the time the structure failed — measured at speeds higher than 20 mph with gusts in the 30s — may have been a contributing factor, Kearns said. But they were not deemed to be the cause of the collapse.

“If you already had some structural stability concerns, then I’m sure that the winds were not helpful,” 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 failed structures, said the OSHA report confirmed what he suspected might have occurred after news broke of the hangar’s collapse in January.

“Initially, I guessed that it was a quality-control issue,” Lu told the Statesman by phone Monday. “It’s one floor, right? It’s not a very heavy load, and steel structures are usually pretty strong, as long as they’re connected well. And technology-wise, this is a pretty mature design.”

Lu said most structural failures that occur during the construction phase are caused by poor management or quality-control problems.

He questioned whether the laborers at the site were adequately trained or licensed to do the kind of work they were tasked with. He said construction engineers should’ve been in the field overseeing the project.

“It appears they didn’t assemble it well or didn’t connect it well,” Lu said.

What OSHA proposes, and why

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

“No one death or life is worth more than another, but for this many to occur all at once especially when they were preventable like these were, it really hurts,” Kearns said.

The regulatory agency also proposed that Inland Crane, the Boise contractor used by Big D Builders, pay more than $10,000 in fines for exposing workers to hazards and failing to ensure the hangar’s stability as it was erected.

Big D Builders, citing a pending lawsuit, said it had no comment on the citation or OSHA’s findings.

Inland Crane said OSHA’s findings align 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 out there, they were involved, they were very familiar with the bending and the waving, the issues with the structure. They did express concerns, but they did not take steps to remove workers from the hazard. In the end, they were very fortunate that they did not injure or lose any of their own workers.”

OSHA: Let this be a ‘wake-up call’

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

“I’m hopeful that if anything good comes out of a tragedy like this, it’s that it helps tune up their safety practices, helps improve the culture they have there at the worksite, and workplace safety and health is a core value for them,” he said.

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