An engineer warned in October 2018 that he had discovered “major structural damage” to a concrete slab below the pool deck in the section of the Champlain Towers South condominium building that collapsed Thursday, killing at least four and leaving scores trapped, according to records released by local authorities late Friday.

The engineer, Frank P. Morabito, said in a structural survey report that waterproofing below the pool deck and entrance drive had failed, allowing damaging leaks.

“Failure to replace the waterproofing in the near future will cause the extent of the concrete deterioration to expand exponentially,” Morabito wrote. He said a “major error” had been made in the construction of the building when waterproofing was laid on a flat slab rather than on a sloped surface to allow water to run off.

His firm, Morabito Consultants, said in a statement Saturday that the damage he found “required repairs to ensure the safety of residents and the public” but that the repairs had not been started when the collapse occurred.

Morabito’s firm has offices in Maryland and Florida.

Morabito said in his inspection report that he also found “abundant cracking” and deterioration in the concrete columns, beams and walls supporting the parking garage under the pool deck, along with damaged and exposed rebar.

The report said that the necessary repair work, which would be aimed at “maintaining the structural integrity” of the building, would be “extremely expensive” and would create significant disruption for residents.

According to the consulting firm’s statement, after the firm gave the condominium association an estimate of costs for the repairs, about 18 months elapsed before the association hired the firm to prepare detailed repair plans. An 84-page draft of the plans from April this year also was released by Surfside.

Previous repairs to the slab supporting the pool above the garage, including the patching of cracks, had been done “less than satisfactorily” and needed to be completed again, according to Morabito’s inspection report.

Other problems detailed in the report included “significant cracking” in the stucco facade of the building, flooding in some apartments because of failed seals on doors and windows, and damaged balconies.

The detailed repair plan was aimed at ensuring that the building, which was completed in 1981, passed a mandated 40-year recertification process.

A separate inspection report on the building by Morabito, completed around the same time as the structural survey report, was also released by the town of Surfside, along with a note that said: “This report was not formally submitted or authorized by the property owner Champlain Towers South Condominium Association, Inc., as required by Section 8-11(f)(iv) of the Miami-Dade County Code.”

It is unclear why Morabito did not submit the 2018 report to the city until 5:35 p.m. Thursday, after the collapse. Morabito did not return calls, and his firm’s statement did not directly address the issue. Neither the town nor condo association responded to requests for clarification.

A former member of the Champlain Towers South condo board, Max Friedman, said that the damage identified in the 2018 report had prompted a $15 million construction project to make repairs.

“It was an expensive project,” Friedman said. Some condo owners “have paid up front and some were going to pay over a period of time.”

He also said the condo association had taken out a line of credit for the project. The repairs on the roof that were taking place before the building collapsed were an early part of this larger repair effort, he said.

Friedman said he has owned his condo for about a decade and has served on the board for several years but does not now.

He said that there was water in the basement garage occasionally and that it would “come and go depending on the season.”

“I think before the catastrophe it was quite dry,” he said. “When it rains, there is water in the garage. That was part of the project also, to put more water-proofing in and fix the columns.”

Friedman lives in New York City and was in Surfside a few weeks ago visiting the condo.

“Our apartment was completely destroyed,” he said. “It’s gone.”

Investigators will review Morabito’s reports as they search for signs of why the building collapsed catastrophically early Thursday. Surfside Mayor Charles W. Burkett told reporters Friday that authorities have “no idea” what caused the collapse.

John Pistorino, a veteran engineer who helped write the Miami-Dade County code that requires buildings to be inspected and recertified once they are 40 years old, said he had been hired to look into the Surfside collapse.

As a young engineer, Pistorino discovered that the area’s salty and humid climate had contributed to the weakening of a building that collapsed in downtown Miami in 1974, killing seven people.

Investigators will probe whether salt, humidity and other environmental conditions also could have weakened the Champlain South structure or if other problems such as a sinkhole-like collapse in the ground underneath the building led to the disaster.

“We got to get to the bottom of this. This is such an unusual and mystifying type of collapse,” Pistorino said. “Something very unique has happened here.”

Some local officials and others interviewed said that the 40-year review process should be made more rigorous and that the inspections should be more frequent. They noted that the checklist does not include an examination of the ground under buildings such as Champlain Towers.

“It’s not just what’s happening above ground — it’s what happening below ground that counts,” Surfside Building Department chief James McGuinness, told reporters. According to McGuinness, the review is strictly focused on the structural load-bearing elements of the building and its electrical systems.

Surfside Town Commissioner Eliana Salzhauer told reporters Friday that commissioners believed the process should be adjusted to include underground checks.

“They look for cracks in the concrete, but they really have no clue what’s going on beneath the ground,” said attorney David Haber, who specializes in construction and condominium law. “Who knows what it looks like below grade? That’s something that I think we are going to have to look at changing in South Florida, with the rising water table.”

Haber said policymakers should consider requiring the recertification process to begin after 30 or 35 years because of the corrosive effects of the ocean air.

Salzhauer agreed and called on state lawmakers to begin updating the guidelines.

“Why are we waiting 40 years to do recertification, especially on the beach?” Salzhauer said in an interview.

In recent months, a much larger building was constructed next to Champlain Towers. During construction, Salzhauer said some Champlain Towers residents had complained that the vibrations had caused property damage, including some cracks in their building.

“Some of those things may have been factors, but this is an investigation, and we don’t know where it’s going to lead,” Salzhauer said.

But Salzhauer said Surfside, like communities throughout South Florida, has been battling erosion. Many buildings have been constructed on reclaimed marshland.

“Remember, the water just doesn’t go where we see it,” Salzhauer said. “The water is underneath. Miami Beach has water underneath. There is water below us, and the water is above us. And we have to live in that precarious balance of having to build on what is essentially a big puddle of water.”

At least 159 people are unaccounted for and four are confirmed dead after a condo building’s sudden collapse in Surfside, Fla. (Reuters)

Last year, the U.S. Army Corps of Engineers did a full replenishment of Surfside’s beaches, Salzhauer said. Much of the sand for that project was initially stored directly in front of Champlain Towers, she added.

“We trucked in thousands and thousands of tons of sand, and it was dumped right in front of that location,” Salzhauer said. “And I don’t know if that weight of all of that schlepping of sand contributed to anything. But I don’t think its going to be any one factor. I think its going to be a cumulative effect of many different things.”

Jason Borden, a Fort Lauderdale-based engineer, said that he had examined the building during a January 2020 walk-through as his firm prepared an unsuccessful bid for the contract to conduct the 40-year inspection.

Borden told The Washington Post that he had noticed deterioration of the building’s stucco cladding; deterioration of concrete on some balconies; deformation or damage of balcony guardrails; and cracks in the ceiling of the garage along with calcification and rust that indicated a water leak through waterproofing.

But Borden, a regional director at O&S Associates, said these issues were typical and not alarming. “I certainly didn’t see anything requiring evacuation or any indication of imminent collapse,” he said.

Attorney Donna DiMaggio Berger, a colleague of Kenneth Direktor, whose law firm represents the Champlain condominium association, said the replacement of the building’s roof had been flagged as a top priority as hurricane season approached.

McGuinness, the town building official, said he had been on the building’s roof only 14 hours before the collapse. He said he did not see an inordinate amount of materials or equipment whose weight he believed could have led to the disaster.

DiMaggio Berger said that a “subsurface, structural issue” likely caused the collapse. “This building was on pilings buffeted by the Atlantic Ocean and the Intracoastal Waterway,” she said. “We’ve got water coming at this thing from both sides.”

In recordings of emergency responder radio traffic from early Thursday, around 1:20 a.m. an unidentified person is heard saying that an alarm was ringing at Champlain Towers. The kind of alarm was not specified.

Around 1:31 a.m., another unidentified person said over the radio that county authorities reported there was “a collapse inside the building” and a fire, before amending their comments to say there was no fire, “just a straight-up collapse.”

The radio traffic was posted on Broadcastify, a website that compiles such recordings.

The day before the collapse, one of the now-missing residents told her son that the building was making “loud creaking noises,” CNN reported. Pablo Rodriguez, whose mother and grandmother are among those missing, told CNN the creaking was “loud enough to wake her.”

The 12-story Champlain Towers South building was completed in 1981, according to Miami-Dade County records. It stood alongside two similar towers named East and North.

The properties were developed by a real estate partnership including the Polish-born Canadian Nathan Reiber, who died in 2014. Reiber was charged by Canadian authorities with evading taxes during the 1970s, according to a report in the Hamilton Spectator in Ontario, which said that a warrant was issued for Reiber’s arrest after he left for Florida. Canadian federal court records show a tax case involving Reiber from 1981.

Reiber was eventually fined $60,000 after he returned to Canada voluntarily and pleaded guilty to tax evasion, according to the report. Reiber and business partners who owned apartment buildings in Canada were alleged to have skimmed tens of thousands of dollars from coin-operated laundries and issued $120,000 in checks for phony construction work before banking the money themselves.

Reiber, who also was a lawyer, was in 1984 found by the Law Society of Upper Canada to have committed professional misconduct after he failed to cooperate with its inquiry into the tax charges, according to the Globe and Mail, which reported that Reiber was allowed to resign from the society.

Reiber’s widow and two of his children did not respond to messages.

Once in Florida, Reiber and his fellow developers faced a moratorium on construction in Surfside in 1979 because of problems with the sewer system. After the Champlain developers agreed to pay half the $400,000 bill for upgrades, according to reports from the time, rival developers with stalled projects complained that they had been given preferential treatment for permits.

The following year, the Champlain developers asked two members of the town council to return campaign contributions that they had made, after the company was accused of trying to buy favor from local officials.

Reiber was awarded the key to the city once all the Champlain towers were completed in 1986, according to his obituary.

Former representatives of the companies that had a role in the construction of Champlain Towers were unwilling Saturday to discuss the building.

One of the companies, Brieterman Jurado & Associates, Consulting Engineers was mentioned in the 2018 engineer’s report as a consultant in the building’s construction. William M. Friedman & Associates Architects helped with the design.

Manuel Jurado said his side of Breiterman and Jurado handled the mechanical and electrical while Breiterman handled the structural side. (Sertio Breiterman died in the 1990s.) Jurado said he did not do anything with waterproofing or inspections. “To be honest with you, I don’t remember,” said Jurado, 92. “I don’t even remember this building in Surfside.”

Manuel Tapia-Ruano, a former vice president of the Friedman architectural firm, said the building’s design was handled by William Friedman, who died in 2018.

“It was his project, not mine,” Tapia-Ruano said about Friedman, at his doorstep in another part of the greater Miami area.

“When I joined the company, the building was already constructed,” Tapia-Ruano said. He had heard about the collapse but declined to discuss what might have caused it or how it might have been prevented.

“I don’t know anything about it,” he said.

On Friday, as officials and lawyers called for greater scrutiny of the ground underneath residential structures, The Post found that research indicating that the site of the Champlain building had been sinking was made public at least 3½ years ago, earlier than was previously known.

An academic study published in April 2020, which found that the building appeared to have been sinking during the 1990s, was first reported by USA Today on Thursday, after the tower collapsed.

But findings in that study previously appeared in a 2017 doctoral thesis by one of the authors, a copy reviewed by The Post shows. The thesis included satellite imagery in which apparent subsidence in the area around the building was highlighted.

The thesis, by Italian researcher Simone Fiaschi, was submitted in January 2017 and subsequently published on the website of the University of Padua in Italy, where it remains available to download. The thesis was online by December 14, 2017, archives of the site show.

Fiaschi’s co-author, a professor, Shimon Wdowinski of Miami’s Florida International University, told The Post that he had presented research in the past to Miami-Dade officials as part of a regional task force seeking to tackle climate change but could not recall whether the subsidence in the area of Champlain Towers South had been discussed.

Leaders of the task force and a senior Miami-Dade official who participates on it declined to comment when asked if they had been aware of the findings.

Wdowinski said that he did not think Surfside town officials were aware of his work. Town Manager Andy Hyatt told reporters Friday that he had not been made aware of the research, which was published several months before he took his position in November 2020.

Fiaschi stressed in an email to The Post that the reason for the collapse of Champlain Towers was unclear, saying it was “not possible to understand which are the causes of the collapse, or if the subsidence we detected have some sort of contribution to the failure of the building.”

In the studies, Fiaschi and Wdowinski detected sinking by comparing images of the Earth’s surface taken over time by microwave beams emitted from a satellite.

While the April 2020 study was limited to images of the Champlain site captured between 1993 and 1999, Fiaschi’s doctoral thesis used imagery taken more recently, in 2005. Both studies indicated that the Champlain site sank at a rate of around two millimeters per year, but the thesis highlighted in red additional hot spots of possibly quicker subsidence — more than three millimeters per year — in the area immediately to the north of the condominium building.

Fiaschi told The Post that the 2005 images contained higher possible error rates, making the data less reliable. “I can’t say that the subsidence accelerated based on our previous results,” he said.

Other analysts on Friday said focus should remain on the building’s structural integrity.

Kit Miyamoto, a veteran Los Angeles-based structural engineer who specializes in structural resilience, said that a pillar or column supporting the building appeared to have failed. Corrosion by the salty air or a “differential settlement,” meaning differences between how sides of the building were sitting on the land, could have caused a pillar to collapse, he said.

“This is truly a classic failure of a column,” said Miyamoto, chief executive of Miyamoto International, a global earthquake and structural engineering firm. “It was supporting many stories and that’s why it happened very suddenly.”

Miyamoto, who has studied building collapses around the world, added that it would be difficult to pinpoint the exact location of the degraded pillar because of the near-total destruction of the building. “It requires a forensic investigation, like peeling off the skin of an onion, one by one,” he said.

Peter Dyga, president of Associated Builders and Contractors Florida East Coast Chapter, an industry trade group, said that Miami-Dade’s building code was one of the strongest in the nation but added “of course, you can always do more.” He said that there would be obvious cracks in the building if there were deficiencies underneath.

“The process is already very extensive,” he said. “Also, you don’t have to wait 40 years to take action on something that’s visible.”

Investigators are likely to examine whether necessary repairs were carried out promptly. A relative of two missing residents told The Post that there had been some disagreement among members of the condominium board about funding for necessary improvements to the building.

“They knew they had to do something, but they were fighting over the cost of having to address this issue,” said the relative, who spoke on the condition of anonymity to discuss matters that are already the subject of a lawsuit.

Direktor did not respond to a request for comment on the relative’s claim.

A lawyer who sued the condominium association in 2015 said Friday that if the building collapsed because of neglected structural problems, it would be consistent with past unwillingness to address such issues in his client’s case.

The attorney, Daniel Wagner, said corrosion had contributed to water damage caused inside his client’s first-floor unit. In that case, resident Matilde Fainstein said damage to her home was caused by water seeping in through an exterior wall.

Building code compliance records from 2015 to 2021 show a litany of minor code violations that suggest a somewhat haphazard management approach, but none that suggest a likely cause of collapse. The code violations include expired elevator certifications, an expired fire extinguisher panel certification, lights that don’t comply with sea turtle conservation rules, gates that don’t close properly, holes in the wall in the stairwell and “an excess of accumulated water on the pavement in the garage, possibly due to a leaky sprinkler,” and other issues.

Wagner said an inspection of the unit and its surroundings revealed signs of corrosion. He sent a letter to the board, he said. A confidential settlement was reached.

Wagner said the collapse should serve as “a wake-up call” to other condominium boards, some of which fall short in fixing problems in the interest of saving money and to avoid raising maintenance fees. Condominium boards and unit owners prefer to keep maintenance costs low and avoid charging special assessments “presumably to attract buyers and keep market values up, all to the detriment of those same unit owners,” he said.

“Associations sometimes opt to forgo necessary maintenance repairs and to take the risk,” he said. “All this does is pass the buck to future generations.”

Caroline Anders, Tim Craig, Max Hauptman, Nate Jones, Joyce Sohyun Lee, Lori Rozsa and Timothy Bella contributed to this report.