On Sunday afternoon, as Hurricane Irma unleashed destructive winds across South Florida, images of towering cranes were causing panic on social media.

At two construction sites in Miami, crane booms — the long horizontal arms that carry loads and balance the structures — had collapsed, damaging the unfinished towers next to them and sending debris onto the city’s empty streets. One appeared to have been bent, dangling perilously to the side. A similar incident was reported later at another construction site in nearby Fort Lauderdale.

While developers and the contractors in charge of the cranes insisted that they had inspected and secured the structures ahead of Irma’s arrival, exactly why the cranes failed remains unclear. The companies, along with city officials, are investigating the cause.

What is apparent, however, is that the cranes collapsed under winds weaker than what they should have been able to endure. City officials said the roughly two dozen cranes that dot Miami’s developing hot spots are designed to withstand winds of up to 145 mph; as Irma tracked to the west, the city saw gusts of up to 100 mph.

Nobody was injured in the incidents, which happened above deserted streets. Still, the crane failures reopened a debate about whether imposing stricter regulations are necessary, with Miami Mayor Tomás Regalado telling the Miami Herald that the city “cannot gamble on the wind.”

Imposing tighter rules, though, could be a regulatory nightmare.

Although Miami enforces codes and regulations on the construction and maintenance of buildings, cranes are regulated by the federal government, specifically the Occupational Safety and Health Administration. State law adds another layer of red tape; Florida statute preempts cities from enforcing laws regulating cranes, said Miami City Attorney Victoria Méndez.

Rules vary in other states. New York City officials, for example, introduced new restrictions, including lowering the wind-speed threshold needed for crews to secure cranes, after a crane fell onto a Manhattan street, killing one and injuring three others in early 2016.

Still, some trade associations in Florida bristled at the mere mention of tighter regulations. Associated Builders and Contractors says imposing new rules would be a knee-jerk reaction.

“It’s premature to say anything because we don’t know anything about what happened,” said Peter Dyga, the president of the trade group’s local chapter, which once sued Miami-Dade County over a crane ordinance. “It could’ve been a tornado. We simply don’t know. It’s possible that the operator made an error. … We don’t know if the equipment was actually put in the proper mode. There’s a lot of facts that need to be investigated and answered before we say that standards are improper.”

Maurice Pons, deputy director of Miami’s Building Department, said the city has ordered the contractors to stop construction work on the buildings where the cranes failed and to remove the towering hazards. OSHA has also been notified, Pons said.

An OSHA official said the cranes appeared to have failed because of the storm, and the agency has offered assistance in dismantling and removing them.

The first crane to make the news Sunday is at a high-rise apartment building in downtown Miami. Its boom snapped, sending bricks to the ground, the Miami Herald reported.

“All three cranes that fell in Dade and Broward counties (one of which is ours) were all north of 300 feet in height,” Ryan Shear, principal at Property Markets Group, the building’s developer, wrote in an email to The Washington Post. “We have limited data of the recorded wind speeds at that height at this time. While yes the investigation is ongoing, at this time we have no evidence that the cranes failed to meet their expected wind capacity.”

Shear said preparations began six days before Irma made landfall on the Florida Keys. That included lowering the crane by about 40 feet, the maximum possible given the time restraint; inspecting it three days before the storm; removing all loose material and debris; and securing openings, entrances and other major equipment, he said. The brakes on the horizontal boom were also released, allowing it to spin freely.

Dismantling and removing all the cranes in Miami would have been impossible to do before the storm hit, city officials and experts said.

Only a handful of engineering companies are equipped to do so, and it takes anywhere from a week to 10 days to remove a single crane, they said.

“And a week ago, we were not even under a hurricane watch, not even a tropical storm watch,” said Dan Whiteman, vice chairman of Coastal Construction, which is in charge of a dozen cranes in the Miami area.

Lowering the cranes as much as possible, while a good safety precaution, would not have greatly mattered, Whiteman said. For example, his cranes were lowered by only about 20 feet and were either as high or higher than other cranes in the area when Irma hit. None of them failed.

Experts said cranes are designed to move like weather vanes, meaning the booms are supposed to spin under strong winds. Locking them and making them more resistant to the wind would pose greater danger, said Dyga, the Associated Builders and Contractors chapter president.

Securing the structures is key, said Jim Robertson, president of Allegiance Crane & Equipment, which rents cranes to Whiteman.

“Tighten and check every bolt in the crane. You basically go through the crane as if you erected it,” Robertson said, adding later: “Cranes should be free and clear of all loose items on top. Power cables are secure, bolts are tight. Those are general common-sense things. It’s all about preparedness. … Everything is detail in this business.”

Brad Meltzer, president of Plaza Construction, the contractor in charge of the second crane that failed, said in a statement that the boom was damaged by high winds despite the company’s preemptive efforts. The property is in a neighborhood of luxury beachfront condominiums just outside of downtown Miami. The third accident happened a few hours later at another oceanfront property in Fort Lauderdale.

“Hurricane Irma was an unprecedented and historic catastrophic storm,” Meltzer said. “Every effort to safeguard life in the path of Irma was taken, including the mandatory evacuation ordered by government officials.”

Cathy Callegari, spokeswoman for Plaza Construction, said the company is assessing the damage and repairing the crane but has not yet determined why it failed.

Shear, the developer in charge of the first failed crane, said the part of the structure that collapsed has been strapped and anchored to temporarily keep it from falling. He said the building’s roof and several floors of the high-rise were damaged.

The threat of the cranes failing under Irma’s winds was known to Miami officials days before the storm hit. The city had advised people to not stay inside buildings next to such cranes.

At the time, Irma was a Category 5 storm, and the National Hurricane Center and other officials were warning Floridians to brace for the worst.

Irma’s strongest winds passed over Southwest Florida on Sunday night. Wind gusts of up to 142 mph, the strongest recorded from this storm in the United States, swept through Naples, The Post reported.

More cranes would have collapsed had Irma directly hit Miami on the state’s east cost, Miami Commissioner Ken Russell said at a news conference Monday. The two Miami cranes that failed are in his district.

“These cranes were at risk. … Fortunately, they did not strike any surrounding buildings and nobody was hurt,” Russell said, adding that he and others will look at possible legislation.

Shear, one of the Miami developers, supports stricter codes, which he said should keep evolving to account for hurricanes like Irma.

“We have learned a lot of lessons from Andrew 25 years ago, and the code has evolved — windows with stronger wind load capacity, elevated lobbies and a slew of other items,” he said. “I think we need to be proactive and ensure safety above all else.”

Others, however, disagree.

“Everyone wants to jump in and propose legislation when they really don’t know whether legislation is going to help,” said Whiteman, the Coastal Construction vice chairman. “Of course, we want to work with officials … No one wants a crane failure.”

Whiteman is also an officer for the Associated General Contractors of America’s South Florida chapter, another trade group that sued Miami-Dade County over a crane ordinance.

He added: “I think that they should look first at the cranes that did not fail and what steps they took to assure that they were properly maintained, and see that those steps are taken in the future as a requirement on all cranes. They need to look at the manufacturers of the cranes that failed and see if there’s something systemic with those cranes that caused them to fail.”

If history was any indication, the prospect of more regulations could be an uphill battle.

In 2008, the construction industry sued Miami-Dade County over an ordinance requiring tower cranes to be able to withstand 140 mph winds. Dyga, of the Associated Builders and Contractors, said the requirement was unattainable at that time and would have put projects that require cranes out of business.

Dyga said he and others fought the ordinance — and won — mainly because regulating cranes was OSHA’s job. According to OSHA rules, the maximum wind speed cranes should be able to withstand should be determined by the manufacturers.

“Once we know all the facts,” Dyga said, “we would welcome as an industry an educated discussion on that at the right place.”

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