Saltwater rising underground causes surfside collapse

Researchers are trying raise the alarm over the dangers rising seas pose for coastal buildings.

Saltwater rising underground causes surfside collapse

Randall Parkinson experienced what he called an epiphany shortly after the collapse of a Condo Tower in Surfside, Florida last June.

Parkinson, a Florida International University coastal geologist, was curious if rising sea levels had caused saltwater to seep beneath the tower's concrete foundation, which could have led to its destruction. He was not alone in asking similar questions. However, he could not find any one who had researched the effects of saltwater intrusion upon residential buildings.

Parkinson stated, "So I decided that I would dig a little deeper."

Seven months after the collapse of on June 24, that left 98 people dead there is still no clear explanation for the cause of the 40-year-old condo, Champlain Towers South. Parkinson is among several scientists who think that saltwater may have caused the tower's collapse.



 

He and others had discovered that rising seas push underground saltwater closer towards the foundations coastal buildings. The staff also noted that Champlain Towers South's underground parking garage was showing signs of corrosion and flooding. They also reported that employees had been pumping water from the garage.

A December report by the Miami-Dade County Grand Jury suggested that saltwater intrusion may have caused the collapse.

Parkinson and other experts insist that they don't believe such damage caused the 12-story building to collapse. Federal authorities are investigating the cause of the incident on a barrier island which includes Miami Beach. Champlain Towers South was damaged by construction defects and severe above-ground corrosion. Residents were upset that the foundation of Champlain Towers South shook when a neighboring tower was built. According to an environmental scientist, the building slowly fell in the 1990s.

Experts say that even though saltwater intrusion was not the cause of the collapse experts want to raise awareness about an unrecognized threat that could leave many residential towers along the Florida coast susceptible to decay.

Parkinson stated, "I feel like this was totally missed." You can see the coast erosion. It's easy to see if your shoreline is being lost or if your property has been flooded. What you don't notice, and what most people haven't started to consider, is all that happens underground. It's hidden underground, and it's not visible.

However, Parkinson and other scientists may still face difficulties convincing Floridians that they need to act to address the threat from rising groundwater. This is due to the lack of research and the fact that repairing damage to buildings could be costly and hinder an condo sector which helps to drive the state's economy.

Steel-reinforced concrete is used in many foundations. Concrete can absorb saltwater and cause corrosion to the steel support. If not protected properly, it can become porous. This can lead to "spalling", where the steel rebar expands and crumbles the concrete around.

The December report of the Miami-Dade County Grand Jury examining condo safety following the collapse noted that there was "open and obvious" spalling in Champlain Towers South. It concluded that it was "fairly certain there had been unseen corrosion or weakening concrete in the foundations and underground pillars."

The grand jury warned that saltwater intrusion could be a serious danger beyond Champlain Towers South. It stated that it "may create hazardous conditions that will negatively affect concrete pillars, foundations that support building structures, particularly those in coastal communities."

A panel foreman and a spokesperson for the Miami-Dade State Attorney's Office declined to comment on the findings. They also cited confidentiality rules. The grand jury was not charged with criminal prosecutions, but with investigating the impact on public safety of the collapse. After federal authorities have determined the cause, local prosecutors will take up this work.

In November, Parkinson published his first peer-reviewed study on rising sea levels' underground attack upon residential buildings. This was later reported in The Palm Beach Post. Parkinson used data from nearby monitoring wells to show that sea level rose caused by rising sea levels. Groundwater rose an average of 244 times per year between 1994 and 2006, to 636 times each year from 2007 through 2020.

Parkinson was unable to get data on water salinity but he suggested that underground seawater and the freshwater layer over it, called a lens, could mix during the natural tide cycle. This is especially true during high "king tides". Parkinson stated that mixing will become more frequent as sea levels rise.

Parkinson stated that eventually, it will all end up as salt. The ocean will rise so high that it will flood the area, and there won't be any freshwater lenses. Although we don't know enough about the future, we can speculate on where it will lead.
Two professors from Florida Atlantic University are working on a similar theory, just an hour away from Parkinson's office. Fred Bloetscher (a civil engineer who studies the effects of sea level rise on municipal water systems), was joined by Anthony Abbate (an architect who focuses on protecting buildings against climate change). They had previously discussed the possibility that steel-reinforced concrete used in building foundations could be damaged by rising salty groundwater levels.

Bloetscher posed the question: "Do you think that this could be a contributing factor?"

Abbate responded, "I don’t know, it sure seems like it,"

Architecture + Design, a peer-reviewed journal. The study used a similar approach to Parkinson's work and found that Champlain Towers South's foundation (including piles, columns and garage floor) had been exposed to saltwater. This is known to increase corrosion and occur in greater quantities and more frequently.

Abbate stated that he has tried for years to get builders and architects interested in the topic. He said that studies on saltwater corrosion risks have focused mainly on portions of buildings above ground or on infrastructure like roads, bridges and water systems. However, in Fort Lauderdale where Abbate is located, saltwater intrusion led to several bursting of sewer pipes. The collapse of Champlain Towers South heightened the urgency of a new threat.

Abbate stated that Surfside was the tragic and unanticipated result of processes we thought were going on, but had never been able to find a study or funding research to prove it.

Abbate stated that more scientific research could lead to changes in building codes. Abbate suggested that testing that measures the salinity and depth of water under buildings could be required. A new code could require foundations to be more resistant to corrosion. Abbate stated that foundations should be equipped with sensors to allow building owners to gather data about a building's "vital sign".

Bloetscher and he want to do more research on South Florida properties to better understand the risk. They have given talks to local design and construction professionals since the Surfside collapse. Bloetscher stated that engineers, bankers, and contractors are interested in the topic, while representatives from the real estate and insurance sectors express less concern.

He said that Florida condo laws, and politics of condo boards, don't encourage deeper investigations of possible threats. They can be costly and could harm the real estate market.

Bloetscher expressed concern about rising groundwater. "This is my main concern. It's not seen and it shouldn't happen again.

Harold Wanless is a University of Miami geologist and has warned for decades about the dangers of sea level rising in Florida. He also once taught Parkinson. Wanless said that he agree with Parkinson's observation of a blind spot in saltwater intrusion research. He cautioned, however, that it is not clear if seawater infiltrated Champlain Towers South's foundation. Wanless stated that without the data, it was difficult to say whether saltwater ate concrete.

Florida International University hydrogeologist Michael Sukop said that he too has become interested in saltwater's effect on concrete foundations for buildings such as Champlain Towers South. He is currently working on a project to measure how saltwater intrusion might impact concrete foundations of coastal buildings. He said that Surfside doesn't have enough information on the saltwater content of the ground and it is difficult to determine the cause.

Sukop stated, "I would like to see more monitoring of freshwater/saltwater interfaces at barrier islands and on mainland." "We have difficulty answering these questions otherwise."



 

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