Newly analyzed evidence in the investigation into the partial collapse of Champlain Towers South in June 2021 that killed 98 people in Surfside, Florida, shows that the pool deck collapsed more than four minutes before the tower itself. But researchers are still working to determine the initial event and aim to finish their technical work this summer.
The US Department of Commerce’s National Institute of Standards and Technology (NIST) team investigating the collapse shared an update on its progress during a meeting of the National Security Team’s Advisory Committee on Construction on March 7.
According to NIST research team leader Judith Mitrani-Reiser, the researchers’ analysis of videos shot in and around the building, including two new videos they obtained in December, as well as interviews with witnesses, help clarify the chronology of the collapse. David Goodwin, the investigation’s project leader, said a video overlooking the Champlain Towers South parking lot under the pool deck, when enhanced with the help of the FBI, showed debris falling before the collapse of the tower. Although still a preliminary analysis, the enhanced video appears to show parts of planters and patio furniture, which had been on the pool deck, in the garage below. A column isn’t visible where researchers think it should be, but Goodwin said that could be due to obstructions or poor lighting.
Emel Ganapati, the team’s project leader, said some residents of an apartment block in the building described noises heard on the night of the collapse. They compared the noises to banging, hammering, or furniture being moved above them.
“The noises got louder and louder before … the collapse of the pool deck,” Ganapati said.
Other videos revealed various signs of movement and damage to the tower, including a hallway floor that was collapsing before part of the tower collapsed. And video from a nearby building shows the collapse of the tower started on a portion of the south face of the tower, next to the pool, below the third floor level and spread northward from there , according to Jack Moehle, leader of the research project.
“The first two videos, along with eyewitness accounts, provide compelling evidence that the first major collapse was on the pool deck,” Moehle said.
Investigators had previously highlighted design deficiencies and construction deviations they found in the pool deck, as well as photos showing signs of distress on part of the pool deck where planters had been added. Georgette Hlepas, a research project leader, described how water was seen around some of the pool deck drains and leak damage was discovered in the roof of the garage below.
Deficiencies of the tower
However, the pool cover is not the team’s only hypothesis of failure. Additional structural analysis also revealed deficiencies in the tower’s design that did not meet the building code or common standards at the time it was built, according to James Harris, leader of the research project. There were also constructional deviations in the tower, such as in columns where reinforcing bars were installed with less overlap between top and bottom assemblies than the minimum allowed by the building code, which is what had been specified on the plans .
Researchers are still working on several hypotheses about what factors may have played a role in the collapse, said Glenn Bell, associate leader of the NIST team.
“While there is strong evidence that the collapse was initiated in the pool deck, we have not yet ruled out that a failure was initiated somewhere in the tower that precipitated the collapse in the pool deck. pool,” Bell said.
The team has also been testing materials and simulating material degradation to better understand key points of the structure. Researchers have taken 497 concrete cores and completed hundreds of mechanical tests for compressive strength, modulus of elasticity, and splitting tensile strength. They have also extracted 369 rebars and completed 40 tensile property tests.
Researchers anticipate substantial completion of technical work by the end of July, Bell said. They will then prepare their report and recommendations, and expect to release a draft report in May 2025, followed by the final report in the fall of 2025 after a public comment period.
“Over the next six months, the main driver of our research activities will be the substantial completion of our technical work through the analysis of failure hypotheses,” Bell said. “As we are concentrating on the most likely hypotheses, thoroughness and rigor demand that we sufficiently analyze all reasonable possible scenarios.”
