A 2020 study by a professor at Florida International University found that the condo building that collapsed overnight in the Surfside area of Miami-Dade County had been sinking into the earth for three decades, USA Today reports.

Shimon Wdowinski, a professor in the Department of Earth and Environment of FIU, calculated that the Champlain Towers South complex had dropped more than a centimeter into the soil between 1993 and 1999, when the data were collected.  While buildings commonly undergo a process of “settling” as people commonly call it, the study found that this building was actually displacing earth under the building, making the structure unstable.

The towers were built on so-called “reclaimed” land:  wetlands that had been filled in to enable development.  Building on such land requires significant research and structural work to ensure the foundation of the building does not shift and is not subject to hydrological or geological stresses that can shift or literally liquify the earth under the development. 

“It was a byproduct of analyzing the data. We saw this building had some kind of unusual movement,” Wdowinski said.

The fact that one portion of the building remained standing also provides a little insight into what may have caused the collapsed portion to become unstable.

“The fact that one part of it is still standing is important. The portion that collapsed might have been tipping compared to the other portion, which may not have been sinking as fast. So you have an unequal situation, and in between, things begin to crack and tilt,” Matthys Levy, a consulting engineer, professor at Columbia University and author of “Why Buildings Fall Down: How Structures Fail.” told USA Today.

At least one resident of the building had sued the management company for not handling cracks in the exterior of the building which led to water damage to the interior of the building.  Crack in floors and walls signal that a building is shifting in an unstable fashion.

Coincidentally, the building was undergoing a recertification that buildings in the area must undergo every 40 years.  Local officials had not yet received the recertification report, but they reported that no emergent issues had been identified.