Federal Surfside collapse probe points to pool deck as likely trigger

Federal Surfside collapse probe points to pool deck as likely trigger - The Washington Post

Structural engineers investigating the deadly 2021 collapse of the Champlain Towers South condominium building in Surfside, Fla., have identified the pool deck as a “leading hypothesis” for what triggered the building’s failure but say it will still take more than a year to finalize their inquiry, officials told a federal committee Thursday.

At a day-long series of presentations before the National Construction Safety Team Advisory Committee (NCSTAC), investigators said they are heavily scrutinizing the building’s pool deck area because of a “series of safety concerns” at the time of the collapse.

The investigators pointed to “multiple compounding factors” that put stress on the pool deck, including a faulty original design, subsequent substandard renovations and stress caused by extra weight placed on the elevated structure, including landscaping planters.

“All of these factors combined to result in margin against failures in some areas that were critically low at the time of collapse,” said Glenn R. Bell, associate lead investigator of the inquiry.

But as South Florida prepares to mark the two-year anniversary of a building collapse that killed 98 people, Bell cautioned that his team’s findings are preliminary. Investigators continue to explore as many as two dozen other potential causes for the tragedy.

In addition to the prevailing theory of a faulty pool deck, officials said they continue to explore whether the building failure could have originated in the 12-story tower itself — either by “construction deficiencies,” “overstressed” support beams or “extraordinary loading” elsewhere in the structure, such as a vehicle striking a support beam.

But as of now, officials say they have not unearthed much to support theories that the collapse itself started in the tower.

“It seems more likely that something moving in the tower may have triggered an already overloaded pool deck area that failed and then progressed back into the rest of the system,” said Jack Moehle, a project leader for the investigation.

Within weeks of the building’s collapse, several major outlets, including the Miami Herald and The Washington Post, published investigations that pinpointed the pool deck area as the likely cause of the accident. Thursday’s investigative report, first reported by the New York Times, indicates that federal authorities continue to home in on the pool deck as the likely trigger.

Officials said they hope to complete the technical analysis of their investigation by April 2024. It will take another year after that for them to write a final report and identify recommendations that can be incorporated into building codes and national engineering standards.

Bell, an engineer with the National Institute of Standards and Technology, urged both the families of the victims and the public to be patient as the investigative process plays out over the next two years. He said the stakes are too high for investigators to rush their findings.

“We are doing all we can to communicate our findings publicly, and today is a major step forward with doing that,” said Bell, who quickly added it that would “would be a disaster” to make a premature finding that was later disproved.

“The goal here is to find out what happened and correct things,” Bell told the panel. “Whatever those corrections are, are not going to be easy. They are going to cost money and create hardship, and there will probably be resistance, so it is absolutely critical that our findings are ironclad.”

Yet while they remain hesitant to make a definitive conclusion, investigators are increasingly confident that the Champlain Towers South building was designed and built in 1979 and 1980 without adhering to the proper building codes at the time.

“Furthermore, there is evidence of errors in construction and renovations that compounded those deficiencies,” said James Harris, another investigator, who added those “quality issues are eerily parallel” to how poor construction led to the collapse of two walkways at a Hyatt Hotel in Kansas City, Mo., in 1981.

That collapse, which occurred during an evening tea dance, killed 114 and injured more than 200 others. Federal investigators later determined that the two skywalks were built in such a way that they barely supported their own weight, in defiance of local building codes.

At Champlain Towers South, investigators say their concern about the pool deck stems from a belief that it fell short of the “margin of safety” — which essentially means something is built with the strength “required to resist the loads and conditions of the building’s use over its life,” Bell said.

Bell added the building’s pool deck was built with “deficiencies in the original structural design,” including slabs that were “well short of the applicable building code.”

“So from the beginning, the original structural design provided low margins of safety,” said Bell, who added that steel reinforcement beams were also placed lower than they should have been during construction of the building.

During later renovations, Bell said, the pool deck was stressed further by the addition of “heavy planters” near the area’s north side that were not part of the building’s original design.

“At one time, there were palm trees in those planter boxes, some approaching three stories tall,” Bell said. “The weight of those palm trees and the action of wind blowing on them could have damaged the slabs over time.”

Even more weight was added to the pool deck when nine inches of sediment and sand was placed in that area during a renovation, Bell said. In another part of the pool deck, a sand bed was added with a waterproofing layer on top of the tile and mortar, Bell added.

“These additional loads even further reduced the margins against failure,” Bell said.

Finally, Bell said investigators have discovered that some of the reinforced steel that supports the pool deck had corroded over time.

But he stressed that it will still take more work to evaluate just how big of a role the corrosion played. As they work to finalize their findings, investigators plan to build a reproduction of the pool deck area to continue testing their theories.