NIST investigation of Champlain Towers South collapse indicates no sinkhole

Investigators from the National Institute of Standards and Technology (NIST) say they have found no evidence of underground voids on the site of the Champlain Towers South collapse, according to a new NIST report.

The team of investigators have studied the site’s subsurface conditions to determine if sinkholes or excessive settling of the pile foundations might have caused the collapse. They have found no such evidence to support that potential cause.

Preliminary evaluation of data indicates about one quarter of an inch or less of settling in the pile foundations supporting the pool deck structure and basement. This would have had minimal impact on the pool deck structure, NIST says.

“Understanding exactly what caused this collapse is taking meticulous investigation and the collection of copious amounts of evidence and information,” said Joannie Chin, director of NIST’s Engineering Laboratory. “Our team members are dedicated to unraveling the complexities of this tragic event, and their rigorous research and analysis will not only help us understand the likely technical cause of the collapse but will improve the safety of our communities.”

The team’s preliminary evaluation of physical and historical evidence found that the pool deck construction deviated from design requirements. Specifically, the number of slab reinforcing bars centered over vertical columns was inadequate, and the reinforcing bars in the top of the slab in the vicinity of the columns were spaced farther apart than the design required, according to investigators. These deviations weakened the slab-column connections, they said.

NIST expects technical work on the investigation to be substantially completed in late June 2024 and aims to release a report with findings and recommendations in late June 2025.

Components of the $9-million structural concrete construction phase included a 700-foot-long, below-grade baggage-handling tunnel; metal decks covered in poured-in-place concrete; slab-on-grade for the new terminal; and 10 exterior architectural columns––each 56-feet tall and erected at a 14-degree angle.