A 2018 engineering report released by the city of Surfside, Florida on Saturday found a “major error” in the construction of the 12-story condominium building that collapsed on Thursday morning, leading to water infiltration that caused structural damage below the pool deck.
“The main issue with this building structure is that the entrance drive/pool deck/ planter waterproofing is laid on a flat structure,” says the October 2018 report by Morabito Consultants. “Since the reinforced concrete slab is not sloped to drain, the water sits on the waterproofing until it evaporates. This is a major error in the development of the original contract documents prepared by William M. Friedman & Associates Architects Inc. and Breiterman Jurado & Associates, Consulting Engineers.”
The Champlain Towers South homeowners association hired Morabito as it prepared for an inspection required by the Miami-Dade County for multifamily residential buildings that reach 40 years of age. The structural engineering firm recommended $9 million in repairs to the building, but did not say there was any imminent danger.
Morabito’s report said that failed waterproofing is causing major structural damage to the concrete structural slab below the pool deck. The report said “where the slab had been epoxy-injected, new cracks were radiating from the originally repaired cracks.”
“Failure to replace the waterproofing in the near future will cause the extent of the concrete deterioration to expand exponentially,” the report said.
Morabito said repairs to the waterproofing around the pool deck would be “disruptive and create a major disturbance to the occupants of this condominium building.”
About half of the condominium building, containing 136 units, collapsed early Thursday morning. Rescue teams continued digging through the rubble on Sunday after recovering nine bodies among the debris.
The Miami Herald reported that Surfside Town Commissioner Eliana Salzhauer said residents of the building expressed concern about water leaking from the pool deck and collecting in the basement parking garage before the disaster.
Steel rebar laced into concrete forms to increase tensile strength can expand when water infiltrates the structure, causing cracks in the surrounding concrete in a process called spalling. Engineers speculated even before the city released the inspection report that corrosion of reinforcing steel may have been a factor leading to the collapse.
Gregg Schlesinger, a former construction project engineer who is now a lawyer handling construction defect cases, said another area of concern in the report is cracks that were discovered in the tower’s stucco facade, the Associated Press reported. Schlesinger said that could indicate structural problems inside the exterior that could have been critical in the collapse.
“The building speaks to us. It is telling us we have a serious problem,” Schlesinger said in a phone interview with an AP reporter on Saturday.
He added that there are frequently “telltale signs” on oceanfront buildings indicating problems structurally largely from saltwater and salty air intrusion.
“This is a wakeup call for folks on the beach. Investigate and repair. This should be done every five years,” Schlesinger added. “The scary portion is the other buildings. You think this is unique? No.”
Abi Aghayere, a Drexel University engineering researcher, said the extent of the damage shown in the engineering report was notable. In addition to possible problems under the pool, he said several areas above the entrance drive showing signs of deterioration were worrisome and should have been repaired immediately because access issues prevented a closer inspection.
“Were the supporting members deteriorated to the extent that a critical structural element or their connections failed leading to progressive collapse?” he wrote in an email to the AP after reviewing the report. “Were there other areas in the structure that were badly deteriorated and unnoticed?”
Engineer John Pistorino told WUSF News that concern about corrosion caused by South Florida’s humid and salty ocean air led Miami-Dade County to require recertification of multiple-family structures once they reach 40 years of age.
Pistorino was a consulting engineer for the county in 1974 when the federal Drug Enforcement Agency building in downtown Miami collapsed, killing seven employees, WUSF reported. He told the news service that aggregate rock used in concrete can contain salt that when combined with humidity can corrode reinforcing steel.
Pistorino told WUSF that it is far too soon to make guesses about what caused the Surfside building to collapse. However, he also said corrosion in older buildings prompted Miami-Dade and other Florida jurisdictions to require recertification after 40 years and every 10 years thereafter. The DEA building was about 40 years old when it collapsed.
Champlain Towers South happened to be going through its recertification process when disaster struck. Mark Direktor, an attorney who represents the condominium’s homeowner’s association, told the New York Times that the association had hired an engineering firm to begin the inspection. The engineers have a good idea where the building needed restoration, but the extent of the corrosion is often not clear until the work is underway, he told the Times.
According to the Times and other media reports, a resident filed suit against the homeowners association in 2015, alleging that poor maintenance of the building allowed water to damage her unit after entering cracks through the outside wall.
Researchers know that the land under the Champlain Towers South building was sinking before the building partially collapsed, but engineers said some other factor must have triggered the catastrophic structural failure.
Florida International University professor Shimon Wdowinski and colleagues noted in a paper published in April 2020 that land subsidence— or settling — had occurred at the location of the condominium complex from 1993 to 1999. Using satellite radar data, the researchers measured a 12mm drop over the six year period. That’s about half an inch.
Wdowsinski told the Miami Herald that the sinkage was not significant, but stood out because most of the surrounding area was stable. He said that subsidence alone, however, could not have caused the collapse.
Wdowsinki told FIU News that he has seen far more dramatic subsidence in other locations. Mexico City, for example, is sinking at a rate of 15 inches per year, he told the university’s news service.
David Peraza, a principal engineer with Exponent in New York City, told the Claims Journal in an email that the land subsidence noted in the FIU report would not have raised any concerns about potential structural damage. He said most times buildings are not affected when land subsides unless the settling is differential, meaning much greater on one side of a structure. Nothing in the research noted any differential subsidence, he said.
Peraza said something else must have caused the collapse.
“It is highly unusual for a building that has stood for 40 years to collapse spontaneously, without an apparent trigger,” he said. “By ‘trigger’ I mean an added load, like an impact, explosion, hurricane, snow, etc. Or a trigger can be a significant reduction in strength, as might be caused by the removal of a major structural element, or severe deterioration.”
Peraza said the owners of the building or perhaps the city of Surfside will likely retain structural engineers to conduct a forensic investigation to determine what went wrong, and also assess the safety of the portion of the structure that remains standing.
“Initially, a structural engineer will develop a list of hypotheses and he or she will then attempt to whittle those down by process of elimination,” he said. “This is easier said than done.”
The investigation will be complicated by the intense rescue and recovery effort at the site of the collapsed building. The removal of debris to search for survivors will take precedence over evidence preservation.
And the rescue operations may be underway for sometime. Peraza said the rescue/recovery effort took eight days after the 16-story L’Ambiance Plaza collapsed in Bridgeport, Connecticut in 1987 while under construction, killing 28 workers.
Some aren’t waiting for a full investigation before assigning blame. On Thursday, Champlain Towers South homeowner Manuel Drezner filed a purported class-action lawsuit in Miami-Dade Circuit Court alleging that the association had failed to take adequate and reasonable measures to ensure the safety of residents and their property.
“Defendant knew, or should have known, of the risks inherent in its activities or involving Champlain Towers South, as well as the importance of adequate safety measures,” says the lawsuit, filed by the Brad Sohn law firm.
About the photo: People look at the partially collapsed Champlain Towers South Condo in Surfside, Fla., Thursday, June 24, 2021. (David Santiago/Miami Herald via AP)
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