A ROOF OVERBURDENED with construction equipment, poor waterproofing, faulty construction: if reasons such as these are behind the catastrophic collapse on June 24th of a condominium building in Florida, they will be fairly straightforward to learn from and to fix in other buildings. Far more worrying is another theory, that the cause may be a failure to adapt to climate change.
With ten people reported dead, rescue crews are still searching for survivors within the rubble of the Champlain Towers South building in Surfside, a suburb of Miami. One hundred and fifty-one remain missing. The disaster, which destroyed 55 of 136 apartments, may turn out to be the deadliest building collapse in America for 20 years.
It is too soon to know what caused it. But one theory is that over the years the ground shifted beneath the building. Shimon Wdowinski, a researcher at Florida International University, published a paper in 2020 in which he used satellite data to chart subsidence of the land on which Champlain Towers stood. From 1993 to 1999, he reported, the ground beneath the building sank at a rate of nearly two millimetres a year. Although these data have prompted many to extrapolate the threat to nearby developments, Dr Wdowinski cautions against that. He stresses that his data were more than 20 years old and covered only a tightly localised area.
At the same time as the land is sinking, the water is rising. Sea levels around Miami rise at an average of nine millimetres a year—nearly triple the global average—and tidal flooding is regular and severe. The presence of more salt water in or near the foundations, whether in the form of flowing liquid or tiny particles carried in moist sea air, can cause severe structural damage. If chloride ions permeate concrete blocks and reach the reinforcing steel bars within them, the metal will rust. The bars then expand, both compromising their ability to withstand stresses and causing the surrounding concrete to flake off and crack—a process known as spalling.
“When one’s designing a concrete structure in a maritime environment, it’s normally taken that corrosion of reinforcing steel will be the life-governing mechanism of the structure,” says Nick Buenfeld, a structural engineer at Imperial College, London. In a report in 2018 on the Champlain Towers complex, released after the disaster by Surfside officials, an external engineering firm found abundant signs of concrete spalling, though not enough to suggest an imminent collapse was likely.
Though the wet, salty conditions in Surfside make stable construction more challenging, many experts believe such conditions are not the only reason for last week’s disaster. Being in a coastal area is not in itself a recipe for collapse. “Of course you are subjected to the salt water. But that’s just one factor,” says Atorod Azizinamini, a civil engineer at Florida International University.
That said, changing climatic conditions mean that ever more buildings will be exposed to stresses they were not designed to withstand. A report issued in 2019 by Britain’s Institute of Mechanical Engineers, in collaboration with the Florida-based Rising Seas Institute, warned that the world’s infrastructure is poorly prepared for rising sea levels. These are likely to lead not only to more corrosion, but to higher risks of flooding, disruption of vital services, and increased pressure on structural supports. With that rise predicted to be as much as three metres by 2100, more regular assessments and potential retrofits should be a priority.
Depending on the outcome of the investigations, the collapse of Champlain Towers South could illustrate just why such changes are urgently needed. The complex was covered by local building regulations requiring that such structures be given thorough inspections 40 years after construction. Champlain Towers opened its doors in 1981.