SURFSIDE - Federal investigators say the 2021 partial collapse of Champlain Towers South in Surfside likely began in the building’s pool deck, not the tower itself, and that warning signs of structural distress were visible weeks before the tragedy.

 

The National Institute of Standards and Technology shared the update on Tuesday, citing large-scale testing, computer simulations and physical evidence.

“We are near the end of our analysis of failure scenarios. The painstaking work of our investigation is yielding results,” said Glenn Bell, associate lead of NIST.

Preliminary findings focus on a few scenarios that may have contributed to the horrific tragedy on June 24, 2021.

“There were many events of distress occurring across the pool deck and the street level parking decks for days, weeks, months and even years before the collapse of Champlain Towers South,” said Judith Mitrani-Reiser, team lead at NIST.

Investigators found that corrosion, concrete shrinkage and faulty construction joints weakened a pool deck slab-column connection, where the failure likely started.

“Our recent analysis of eyewitness accounts of the pool deck collapse, which Judy has described, as well as review of alarm system records, indicate that the pool deck likely collapsed at least seven minutes before the tower,” said Bell.

Additionally, investigators said:

“It is more likely that the collapse initiated in the pool deck than the tower. At the time of the failure, the pool deck’s slab-column connections had critically low margins of safety. The bulk of the critically low margins of safety was caused by design understrength and misplaced slab reinforcement. The structure had low resistance to progressive collapse, allowing the collapse of the pool deck to spread into and throughout the middle and east parts of the tower.”

Investigators said their ultimate goal is to figure out how this failure started and how it progressed, narrowing in on the pool deck and on the tower.

“Now, the fact that the pool deck collapsed before the tower does not mean that the failure necessarily initiated in the pool deck. Though some of the possible initiating events are in the pool deck and some are in the tower,” said Bell. “In summary, our recent work indicates that it is more likely that the failure started in the pool deck than the tower.”

“These early signs of distress were all concentrated in the pool deck and street level parking deck area, with much concentration near previously repaired cracks and along construction joints,” said Mitrani-Reiser.

The collapse affected families globally, with victims ranging in age from 1 to 92. Rescue missions lasted days on end, with rescue personnel coming to South Florida from around the world.

The towers have since been demolished and are set to be redeveloped.

The probe into the collapse was delayed several times.

The federal investigation was expected to be completed back in June; however, only preliminary findings that focused on the possible failures of slab-column connections in the pool deck, weakened columns in the tower, and failure of joints that connect the slabs in the columns were released.

Investigators ruled out the collapse being related to issues underneath the building, like settling, sinking or piling failure, adding that those structural issues existed for decades.

“The need for rigorous and thorough approach to failure analysis means that these investigations take time,” said Bell.

The investigation is far from over, but officials say another major public update will come in Spring 2027.