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Surfside, Florida: Cameras capture moment condos collapse

A security camera captured the moment a condo partially collapsed in Surfside, a town near Miami, Florida.

Associated Press, USA TODAY

SURFSIDE, Fla. Perhaps it was a fatal flaw in the pool deck that over decades weakened a supporting concrete slab, or a rising sea that drove corrosive saltwater against critical columns in the lower-level garage.

Maybe concrete throughout the building had been poured too thin to protect reinforcing steel, or condo owners and town officials hoped for the best when they should have prepared for the worst.

In the days since the June 24 collapse of the Champlain Towers South condominium near Miami, victims, families, and a shocked nation have pondered those theories and others in a vain search for an answer to the same, desperate question.

What happened?

Yet the only consensus among 10 engineers and other experts interviewed by USA TODAY is that an answer will take time.

This will be a fact-finding not fault-finding technical investigation, said James Olthoff, director of the National Institute of Standards and Technology, during a Wednesday press briefing to announce that agencys investigation. It will take time, possibly a couple of years. But we will not stop until we determine the likely cause of this tragedy.

In the end, experts said, it will likely be a combination of many factors and missed opportunities that ended in what could become the deadliest building collapse in American history not caused by a terrorist act or natural disaster. The confirmed death toll stood at 22on Friday, with 126 others still missingin.

Whether this particular building succumbed to some shortcoming in practice and construction, we just dont know, said Glenn Bell, past president of the Structural Engineering Institute of the American Society of Civil Engineers, who has investigated building failures.

'Major problems': There were many warnings before the Florida building collapsed

But even as the official investigation begins, engineers, scientists, and regulators elsewhere are seeking lessons from whats known so far.

The engineering community will look at this and hopefully learn a lot from it to minimize the chance of this happening in the future, said Reginald DesRoches, provost of Houstons Rice University and a civil and structural engineer.

Emerging evidence points to a potential failure at the lowest levels of the 12-story condominium. Engineering reports and condo association letters reported serious concerns with the buildings pool deck and concrete pillars in the underground garage. Former workers and building residents recalled significant flooding, whether it be from the pool or groundwater.

That raised questions about the potential for rising sea levels and tides to push seawater into the building, corroding materials and leading to a potential failure. Harold Wanless, a geologist and sea level expert at the University of Miami, said the region has experienced about a foot of sea level rise since the 1940s. But less is known about where and how the corrosive saltwater affects structures, and that concerns Wanless.

Exactly what kind of concrete was used in the building, and at the base of the building? … Thats very important because there are all kinds of concrete, Wanless said. Some are very good and can handle salt well. And there are others that dont do well at all.

Files from the Florida Department of Transportation show that the groundwater near Champlain South begins about 2.5 feet underground and is moderately aggressive in its corrosiveness. The groundwater quality came up during construction in a 1979 notice sent by Miami-Dade Countys environmental resources management division. It noted that due to the high chloride content and elevation of the groundwater at this location, builders would have to install special fiberglass tanks for gas and oil that wouldnt corrode.

The Backstory: What our reporters saw, heard and experienced at the Florida condo collapse

But those conditions arent remarkably different from any other place along the barrier island where Surfside rests, according to Lee Hefty, the current director of Miami-Dades environmental division. Numerous experts noted that similar projects have long been constructed in coastal areas without incident, so long as the engineering and maintenance are sound.

You can build anywhere as long as you provide the necessary strength to support your structure, said Abieyuwa Aghayere, a professor of structural engineering at Drexel University in Philadelphia. In an environment like this, what it calls for is a more regular, periodic inspection of these kinds of buildings, because its a very corrosive environment.

Reviewing original design plans of the building, Aghayere saw indications of vulnerabilities to coastal conditions. In addition to seawater pushing up against and corroding weight-bearing structures at lower levels, corrosive salt air can eat away at concrete and exposed metal if they are not properly protected.

Aghayere noted that designs called for three-quarters of an inch of concrete around the reinforcing steel bars known as rebar in balconies and the buildings slabs. Current engineering standards call for 1.5 inches, but Aghayere and other experts werent sure what requirements were in place when the building was constructed. The thin concrete layer could have led to exposure and weakening of the rebar.

Indeed, numerous inspections and reports filed over the past three years showed crumbling concrete and exposed rebar at several places in the building.

I can see why thered be issues with the rebar in that kind of environment, Aghayere said.

He and others said inspections should occur more regularly than the 40 years required by Miami-Dade and Broward counties for recertification.

In coastal areas, recertification, in my opinion, should take place at a 20-year building anniversary and then every 10 years, said Jorge Kuperman, principal architect of JSK Architectural Group in nearby Coral Gables, Florida.

Two days after the collapse, Miami-Dade County Mayor Daniella Levine Cava announced 30-day audits of hundreds of buildings that are at least five stories and 40 years old to ensure they complied with the countys existing recertification requirement.

Florida lawmakers are thinking about going further.

State Sen. Jason Pizzo said he plans to file legislation that would likely focus on building requirements, re-inspection standards for older buildings, the risk of seawater intrusion and the financial obligations of condominium associations.

We should at least be looking at two things: The actual physical structure itself, the design and material used, and the accelerated environmental conditions that are affecting these buildings near the beach, said Pizzo, a Democrat whose district includes Surfside and 14 other Miami-Dade municipalities.

In addition to earlier and more rigorous inspections, experts pointed to some scientific techniques that could avert similar catastrophes.

After a consulting engineer warned of concrete deterioration in a 2018 report to the condo association, tests should have been done on the concretes strength either by compressing it or conducting a chemical analysis, said Syed Ashraf, a structural engineer who has experience retrofitting older high-rises in Miami. Ashraf said such testing is simple and not really expensive.

If the inspector had tested the concrete at the time, Ashraf surmised, he would have seen that the strength of the concrete was very low and there was danger of a collapse.

It remains unclear if failing concrete played a role in the buildings collapse. Some experts noted it could have been triggered by an unidentified event or one difficult to anticipate, such as a sinkhole in the underlying limestone bedrock.

As first reported by USA TODAY, a 2020 study that used satellite data to analyze flooding in the Miami area found that Champlain South appeared to be sinking at a rate of about 2 millimeters a year in the 1990s. The technology could not determine whether the land beneath the condo was actually sinking, or whether a structural flaw was causing the building to sink into the earth or sag onto itself.

Still, Shimon Wdowinski, a professor in the Department of Earth and Environment at Florida International University who conducted the study, said the incident made him realize the potential to use the technology to detect issues with buildings.

Another technology called lidar, a laser-based system that can scan environments and buildings to create a digital map, also shows promise, said Clinton Andrews, a professor of urban planning and director of the Center for Green Building at Rutgers University.

Researchers at Rutgers last year drove a car equipped with the technology around the beach town of Asbury Park, New Jersey, and created a three-dimensional replica of it, Andrews said. They also used it on several buildings in the Bronx in New York City, where they combined lidar with thermal imaging to detect structural defects in buildings, such as a contractor forgetting to install insulation and a leak causing water damage.

Andrews said the technologys cost is decreasing to levels affordable at the municipal level. It could detect structural problems in buildings and help prevent future catastrophes.

Its sensitive enough to detect issues like subsidence, Andrews said, using the scientific term for sinking earth.

Even with the best possible technology to detect a problem, experts said preventing disasters still depends on humans raising alarms and someone responding.

While lawsuits and public debate will parse over what should have been done about the early warnings at Champlain Towers South, the experts were slow to find fault.

Bell, with the American Society of Civil Engineers, cautioned against jumping to conclusions that engineers who inspected the building on behalf of the condo failed to take proper action.

"It's very difficult to judge what is in an evaluator's mind and what actions he should or should not have taken," Bell said.

Kuperman, the Miami-area architect, said nothing in the Miami-Dade code stipulates when an engineer is to raise an alarm.

In fact, a licensed professional does not have the faculty or authority to raise alarms but (only) to put on record what is observed, Kuperman said.

Instead, the experts said responsibility for determining when a building is unsafe and needs to be condemned or evacuated should fall on cities or counties. Ashraf, the structural engineer working in Miami, took issue with Ross Prieto, a former Surfside building official who after receiving the 2018 inspection report told the condo association that the building was in very good shape, according to minutes of an association meeting.

I totally disagree with the building official, Asharaf said. He should have given a notice of violation. It does not mean that he's shutting the building down, but it would have expedited the process and the collapse would not have happened.

Prieto has not returned calls and messages left by USA TODAY.

Asked whether the incident could trigger changes in how engineers respond to troubling inspections, Bell said that a professional obligation to protect the public is already written into engineering codes and standards.

If there is an issue where a structural engineer feels there is an imminent threat to public safety, they need to do things to encourage that its addressed, Bell said.

As more facts emerge, Bell said he believes the engineering community will make changes to safeguard buildings. That typically starts with new national policies among engineering organizations that filter down into new state and local laws.

Since this failure, there have been discussions in the profession about what were doing currently and what well be doing going forward, Bell said.

Aleszu Bajak, John Kennedy, Sudiksha Kochi, Erin Mansfield, Jesse Mendoza, Rick Neale, and Elizabeth Weise of the USA TODAY Network contributed.

Read more from the original source:

Engineers ponder what comes next as they seek to avoid another condo collapse in Florida - USA TODAY