Surfside -- A
startling discovery awaited an engineer who drilled into the
ground-level concrete slab at Champlain Towers South last
year. He could find no waterproofing in two separate
sections, the engineer wrote in a letter to the condominium
board.
Without that essential
layer for a high rise facing the punishing Atlantic Ocean,
rainwater and salty sea spray likely had seeped in for
decades, slowly weakening the steel rebar and concrete
holding up the condo building. Indeed, the engineer reported
at the time seeing significant concrete deterioration.
Less than a year later, in the early hours of June 24, part
of that slab dropped into the parking garage below. Within
minutes, the east wing of the 13-story tower collapsed,
killing 98 people in a disaster without modern precedent in
the U.S.
The devastation caused by Hurricane Andrew in 1992 led to
tighter Florida building rules after a grand jury
investigation found flawed designs and shoddy workmanship
among single-family homes. |
|
|
For beachfront
buildings like Champlain Towers that are made from
reinforced concrete, the ocean is a constant source of
danger. Like a steel skeleton, rebar rods run through
concrete columns and slabs. Saltwater seeping through
concrete can cause the steel torust and expand. The concrete
starts to crack and eventually may fail. Since at least the
late 1970s, the American Concrete Institute has recommended
placing a waterproofing membrane—often maThe devastation
caused by Hurricane Andrew in 1992 led to tighter Florida
building rules after a grand jury investigation found flawed
designs and shoddy workmanship among single-family homes.
For beachfront buildings like Champlain Towers that are made
from reinforced concrete, the ocean is a constant source of
danger. Like a steel skeleton, rebar rods run through
concrete columns and slabs. Saltwater seeping through
concrete can cause the steel to rust and expand. The
concrete starts to crack and eventually may fail. Since at
least the late 1970s, the American Concrete Institute has
recommended placing a waterproofing membrane.
Since then, a picture has emerged of a tower that was
hobbled from the start. The people who oversaw its planning
and construction some 40 years ago made cost-saving choices
that generally met the building codes of that era but may
have created long-term safety risks, a Wall Street Journal
investigation found.
They skipped waterproofing in areas where saltwater could
seep into concrete, the available evidence indicates. They
put the building’s structural slabs on thin columns without
the support of beams in some places. They installed too few
of the special heavy walls that help keep buildings from
toppling, engineers say, features that could have limited
the extent of the collapse. And they appeared to have put
too little concrete over rebar in some places and not enough
rebar in others, design plans and photos of the rubble
indicate.
Officials are still investigating why the tower fell.
Engineers consulted by the Journal, including some involved
in the official probes, say it’s unlikely one design or
construction issue identified so far could have brought down
the building by itself, but rather that the cumulative
effects of the decisions ultimately doomed the structure.
“These things kind of snowball,” said Roberto Leon, an
engineering professor at Virginia Tech who isn’t involved in
any official inquiry.
Issues like a lack of waterproofing or too little concrete
cover aren’t unusual for South Florida condos built in the
early 1980s, a time when building codes were laxer and
engineering science less advanced, said James Prichard, a
Florida-based construction lawyer who works with condo
boards statewide.
“It is reasonable for people to be worried about this
happening again because Champlain is not unlike many other
buildings throughout the state,” he said.
Several investigations have begun at the federal and local
level. A spokeswoman for the National Institute of Standards
and Technology, a federal agency probing the collapse,
declined to comment on potential causes. Allyn Kilsheimer, a
structural engineer hired by the town of Surfside to
investigate, said he is looking at dozens of possible
factors.
The people who designed and built Champlain Towers South
decades ago made construction choices that created long-term
safety risks.
Investigators are still trying to determine why this section
of the building collapsed. An engineer drilled into the
structural slab under the ground-level parking area in 2020
and said he found no waterproofing. This part of the slab
later collapsed.
An engineer who tested the concrete slab under the pool deck
found waterproofing beneath the pavers. Building permits
indicate that a layer was installed in 1996 after water
seeped into the garage ceiling below.
Long, rust-colored cracks and stalactites in the garage
ceiling were signs of water damage to the structural slab
above.
The building’s drawings call for a ¾-inch concrete cover
over rebar in floor slabs. The building code at the time
called for 1½ inches of cover for rebar in slabs exposed to
weather. Insufficient cover could make rebar more vulnerable
to corrosion, which in turn could damage a structural slab
over time.
Part of the pool deck collapsed shortly before the building
came down, according to eyewitnesses. Images from the site
indicate that there was less rebar connecting the pool-deck
slab to columns than plans called for.
Engineers say the columns in the collapsed part of the
building were too thin. Many of them measured 16 by 16
inches, compared with 24 by 24 inches in the part of the
building that didn’t collapse. The collapsed portion of the
building had only one lateral shear wall. Engineers say more
shear walls could potentially have limited the extent of the
collapse.
Designed in the late 1970s, the 136-unit Champlain Towers
South was completed in 1981 and marketed as luxury living.
The same development team also built a nearby stand-alone
sister tower, Champlain Towers North, around the same time.
Town officials are still assessing the safety of that
building, said Surfside Mayor Charles Burkett, though some
residents continue to live there.
Many of the key principals are dead, including the
architect, the lead structural engineer and the contractor.
Records show the development team included Canadians Nathan
Reiber and Nathan Goldlist, both deceased. Surviving members
of their families either couldn’t be reached or declined to
comment.
In a brief interview with the Journal, Manuel Jurado, one of
the project’s structural engineers, now 92 years old,
defended the integrity of Champlain Towers South but said he
didn’t recall specifics. It wasn’t clear why the people
behind the project made the design and construction choices
they did; maximizing profits is one of several potential
reasons. Nor is it clear who made many of these decisions.
The risks of some of the choices made four decades ago were
well known at the time, but building codes generally gave
developers wide leeway. The 1979 South Florida Building
Code, for example, didn’t mandate waterproofing on open-air
concrete roofs next to the ocean.
As residential condo towers sprouted along Florida’s coast
in the 1970s and ’80s, skimping on construction materials
and structural elements was an easy way to save time and
money, said Dr. Leon and a veteran South Florida engineer.
Rebar, structural walls and waterproofing layers were hidden
under tiles or paint; flaws or shortcuts were detectable but
only if someone went
looking.
The devastation caused by Hurricane Andrew in 1992 led to
tighter Florida building rules after a grand jury
investigation found flawed designs and shoddy workmanship
among single-family homes.
For beachfront buildings like Champlain Towers that are made
from reinforced concrete, the ocean is a constant source of
danger. Like a steel skeleton, rebar rods run through
concrete columns and slabs. Saltwater seeping through
concrete can cause the steel to rust and expand. The
concrete starts to crack and eventually may fail. Since at
least the late 1970s, the American Concrete Institute has
recommended placing a waterproofing membrane—often made of a
type of advanced plastic—above a weather-exposed structural
slab.
Concrete
Accelerated corrosion due to chloride ions will reduce the
thickness of the rebar, which can weaken it and cause
collapse. Another way for concrete to fail is when iron
oxide forms around
rebar, resulting in an expansion in volume that causes the
surrounding concrete to spall.
Loss of thickness
Morabito Consultants, the engineering firm hired by the
condo board in 2018 to inspect the building ahead of a
required 40-year recertification, said it found no
waterproofing in parts of the ground-level slab but did find
some under the pool deck and planters. These findings were
in a 2020 report, reviewed by the Journal, that Morabito
submitted to the Champlain Towers South condo board.
“Where there is waterproofing, it has failed. Water has
gotten underneath and caused additional damage to the
concrete,” condo-board president Jean Wodnicki wrote in an
October 2020 presentation for residents reviewed by the
Journal.
In addition, part of the driveway wasn’t sloped toward
drains, according to a December 2020 condo-board
presentation, meaning water couldn’t run off.
Efforts to reach Ms. Wodnicki weren’t successful. A Morabito
Consultants spokesman declined to answer questions.
“Morabito Consultants identified extensive repairs that
would be required for the recertification process, but there
was nothing in the firm’s findings to indicate that the
building itself was at risk of complete structural failure,
that it was at imminent risk of collapse, or that it should
be deemed unsafe for occupation,” the spokesman said.
Beneath the waterproofing, oceanfront buildings should have
a second line of defense against saltwater: the concrete
that covers the rebar and thus protects it from corrosion.
The 1979 Champlain Towers South architectural plans called
for just ¾-inch of cover in floor slabs, half the minimum
1.5 inches required by the building code at the time. Some
engineers say photos from the rubble indicate the cover may
have been far than 1.5 inches in some places. The Surfside
mayor at the time, Mitchell Kinzer, said inspectors working
for the town should have caught this and generally ensured
that construction followed code.
All of this left the structural slab at the base of the
tower more vulnerable to corrosion. About a week after the
collapse, a crew from Maryland-based Controlled Demolition
Inc. drilled holes into support columns and sturdy walls in
the still-standing part of the building to make space for
explosives. Officials had hired CDI to take down the
remainder of the tower due to mounting safety concerns for
rescuers.
Looking on from inside the tower during preparations on July
3, CDI owner Mark Loizeaux noticed that concrete chewed up
by the drills was powdery, he said in an interview,
suggesting another potential flaw. This surprised him, he
said, because building plans he reviewed specified those
columns would get concrete with a robust 6,000 pounds per
square inch of compressive strength. Very hard concrete
comes out in chips during drilling, even after 40 years, he
said.
“I asked my drillers, after they drilled two columns,
‘What’s the concrete like?’ They just said, ‘Soft, really
soft,’ ” he recalled.
Mr. Loizeaux said he asked if they believed it to be 6,000
psi. “No way,” he said they replied.
He said his crew used pneumatic drills to make more than 120
holes on the first floor and garage level, and the concrete
was “uniformly soft.” That doesn’t necessarily mean it was
dangerous, he said, but it was notable enough that he shared
the observations with investigators.
Abieyuwa Aghayere, a Drexel University structural
engineering professor who isn’t involved in the official
investigations, said concrete visible in photos of the
rubble looked unusually smooth and homogeneous. He said he
didn’t see any of the gravel typically included to
strengthen it, though only a lab analysis can provide
definitive answers. Engineers say the columns in the
collapsed part of the building were too small. Most of them
were 16 by 16 inches compared with 24 by 24 inches in the
western part. That made them more likely to fail, and
increased the risk that corroding rebar could cause serious
damage.
Mr. Aghayere and other engineers told the Journal that
photos of the rubble in some places appeared to show fewer
of the horizontal steel rods meant to connect columns to the
ground-level structural slab than the 1979 plans prescribed.
They cautioned that it’s possible the concrete contained
more rebar than the photos indicate.
Inadequate waterproofing, weak concrete, small columns and
too little rebar would all increase the risk of a structural
slab collapsing and columns failing, possibly setting off a
catastrophic domino effect, engineers say.
Even so, they say, the entire northeast wing might not have
been doomed once the collapse began had it not been for
another design choice.
Around 1 a.m. on June 24, Iliana Monteagudo awoke in her
sixth-floor condo in Champlain and noticed a crack forming
in the ceiling, according to her son, Manny Frade. Ms.
Monteagudo threw on some clothes, and ran, her son said. She
didn’t take the nearest stairwell because she didn’t know
about it. As she raced down a more-distant one, she heard
the building crash down around her. Within seconds, her unit
and dozens like it were gone—but the staircase she was in
remained standing and she made it out.
“The ‘mistake’ that she committed saved her life,” said Mr.
Frade: The closer stairwell collapsed.
Inadequate waterproofing, weak concrete, small columns and
too little rebar would all increase the risk of a structural
slab collapsing and columns failing, possibly setting off a
catastrophic domino effect, engineers say.
Even so, they say, the entire northeast wing might not have
been doomed once the collapse began had it not been for
another design choice.
Engineers say the staircase she chose was likely saved by a
shear wall—a thick, concrete wall running from the basement
to the roof that stood between the staircase and the
collapsed part of the building. Shear walls are designed to
resist lateral forces like wind and are a crucial part of
many reinforced-concrete buildings.
The part of the building that didn’t collapse had three such
walls. The collapsed segment had only one, and none built to
resist east-west forces, according to the drawings.
With more shear walls, the eastern end of the building could
have held up longer after the collapse began, engineers say.
“That would have saved more lives,” said Jiann-Wen Ju, an
engineering professor at the University of California, Los
Angeles, not involved in the investigation.
How do you think Florida should regulate the condo industry
going forward?
Shear walls make it harder to design large open floors, so
developers and architects often want to include as few as
possible, said Dr. Leon, the Virginia Tech engineer.
Building codes in the U.S. generally leave it to the
building’s engineer to decide how many are necessary.
Mr. Kilsheimer, the engineer hired by Surfside, said he is
considering another potential structural issue: a lack of
support under the building’s slabs.
Engineers often add concrete boxes called drop panels to the
top of columns to help prevent the slab from breaking at the
point where it connects to a column. These, too, add to the
construction cost.
In 2020, Morabito Consultants proposed adding drop panels
atop garage columns in part of the structure where the slab
“was overstressed since the day the building went up,” said
a December 2020 condo-board presentation.
Buildings that don’t have drop panels sometimes have beams
under slabs to help support them, but Champlain Towers
South’s drawings called for beams just on parts of the west
side of the property—the section that didn’t fall.
Despite the building’s many structural flaws, engineers say
some issues would have been fixable, had the property’s
condo board done more extensive repairs sooner. By 1996, the
slab started
showing cracks, and pieces of concrete had fallen off the
garage ceiling, unusual so soon after construction. Workers
patched cracks and waterproofed the pool deck, but that too
eventually
failed.
In 2018, Frank Morabito, president of Morabito Consultants,
wrote that failed waterproofing “is causing major structural
damage” and that the damage would “expand exponentially”
unless fixed.
While owners of the sister tower, Champlain Towers North,
replaced the pool-deck waterproofing in 2020, the owners of
the south tower had dragged their feet on making structural
repairs and other fixes, as the total cost had swelled to
more than $16 million, documents show. It was to be paid by
residents in a contentious special assessment. “We have
discussed, debated, and argued for years now,” Ms. Wodnicki,
the condo-board president, said in an April letter to
residents. Roof work began weeks before the collapse, but
repairs to the steel-reinforced concrete hadn’t yet started.
The day before the building collapsed, the condo owners
received a report based on the building’s 2020 finances. It
said they had saved nowhere near enough for repairs.
Owners were due to pay their respective shares, ranging from
about $80,000 to $336,000 each, the week after the building
collapsed.