SURFSIDE, Fla. — Scraped clean of tons of rubble late last month, the bare garage floor of Champlain Towers South appears to rule out at least one early suspect in its catastrophic collapse.
There were no telltale signs of a sinkhole.
The garage floor, the building’s lowest level, remains in one piece with no craters or potholes suggesting unseen geological forces were at work. The “sinkhole” a doomed resident saw opening from her balcony in a final phone conversation was likely not erosion beneath the building but the implosion of the concrete pool deck above the garage floor — the seeming trigger event of a massive and still unresolved structural failure.
“The slab appears to be intact and there is no obvious sink hole,” said Jennifer Huergo, a spokesperson for the National Institute of Standards and Technology, the federal agency investigating the cause of the collapse. “That said… our experts will be looking at every aspect, above and below ground, for potential triggers.”
Those aspects will include the effects of rising seas on the 40-year-old building, which remain on the long list of contributing factors for structural engineers and other experts trying to piece together the causes of the unprecedented disaster. If increasing tidal flooding didn’t undermine the building, it may have pushed corrosive brine into the parking garage.
Even now, time-lapses of the empty garage floor show flooding that rises and falls with the tide throughout the day. And a former maintenance manager described to Herald news partner CBS4 regular pumping of salt water from the garage — conditions experts say would likely exacerbate the effects of rust on reinforcing steel in concrete slabs and columns.
“We’re chasing like 50 different things and trying to understand them one at a time,” said Allyn Kilsheimer, the independent structural engineer that the town of Surfside hired to investigate the collapse.
Kilsheimer himself isn’t ready to rule anything out, including sea-rise impacts and possible undetected voids or sinkholes under the building. Among the many things he wants to assess are the effects of tides and full moons on the underground water table. He will drill a hole near the north building (a few blocks from the south building) and insert a device called a piezometer, which measures groundwater levels. That, he said, is a challenge in an underground garage on a barrier island — one that also underlines the looming threat of sea rise to South Florida.
“We can’t drill through the basement of the garage because it could create a geyser at high tide,” he said.
A rising threat
What, if any, role rising seas played in the collapse, there is no escaping the rising risks to Surfside and other coastal communities up and down the Florida coast. Low-lying garages in South Florida have flooded for years, some famously so. Recall the 2016 photo of an octopus finding its way up a drainpipe into a Miami Beach condo’s garage.
The 2 feet of sea level rise expected by 2060 will swamp septic tanks, homes, parks and roads. And as waters keep rising, it will eventually render some places permanently uninhabitable.
In a meeting just last year, the town heard from consultants that it faces structural threats from sea rise. The most pressing risk is not along the higher elevations of the beach where Champlain Towers was but on the low-lying side adjacent to north Biscayne Bay.
Streets in the single-family home part of town nearer to the Intracostal Waterway flood so deeply after heavy rains that the water has been reported ruining cars and soaking into houses, garages and crawl spaces. Residents even floated the idea of installing “No Wake” signs to protect their homes.
The meeting was the public debut of a flood model the city commissioned from Atkins Engineering through a partnership with the American Flood Coalition. Caroline Resor, a strategy associate with the flood coalition at the time, told residents that sea-rise-driven flooding could occur as often as 100 days per year by 2030. She said the more extreme of those floods could cause $400,000 to $2 million in damage to homes.
