PDA

View Full Version : Status of the Slurry Wall



ZippyTheChimp
December 27th, 2002, 01:25 PM
This issue came up in a discussion on Libeskind on another forum. It was argued that the slurry wall will need interior support.

I know that during original construction, the wall was supported by tie rods into the bedrock. These were later removed as the wall was supported laterally by the basement floors. The tie rods have since been reinstalled.

I searched online and could not find an answer. I remember last spring there was talk about a new secondary wall being built alongside the original.

Kris
December 27th, 2002, 02:05 PM
I think the operation has been completed and would not compromise the plan. What other forum?

JMGarcia
December 27th, 2002, 03:16 PM
If you look at the video of the Libeskind plan (availble on the www.newsday.com) you can see he has added some additional support to the wall without compromising the visuals. He explained this during his presentation broadcast on NY1.

ZippyTheChimp
December 27th, 2002, 09:05 PM
Thanks for the info.

The forum I was referring to is not architectural. It was set up after 9/11 to help residents get info on what was going on in the neighborhhood. It was never taken down, and is still rather useful. Found out recently that a few dogs were electrocuted (not fatally) on South End Ave. Manhole cover was energized when salt corroded Con Ed feeder cables. :o
Sometimes there's a thread about rebuilding.

http://bpc.mobile123.com/

Kris
December 28th, 2002, 08:52 AM
Poor creatures.

JMGarcia
December 28th, 2002, 11:29 AM
My favorite complaint over there is the one about a bunch of buildings together in an L shape being terrible.

Sounds exactly like the World Financial Center to me, which I'm sure if you asked them they are very happy with.

LOL :biggrin: :biggrin:

Kris
December 28th, 2002, 12:40 PM
I'm surprised they're still debating about whether or not to rebuild and in a patriotism versus reason and culture perspective, as if it would either be a wartime statement of power or a foolish act of pride.

Kris
December 28th, 2002, 12:53 PM
It's all about faith in the idea of NY, of course. Whatever that means, its essence is best expressed in the skyscraper. I wonder why some people who mock the alleged vanity of it live there.

JMGarcia
December 28th, 2002, 01:00 PM
I agree with Chris. I read an article shortly after 9/11 that said rebuilding should not be about either hiding from terrorism or trying to prove a point. It should be about reaffirming the spirit of NY which, according to the article, has always been "bigger, better, newer" and the desire of the human spirit to push the limits and excel.

Kris
December 28th, 2002, 03:26 PM
It also has a mythical resonance. Some proposals explicitely or not refer to Babylon, its tower and hanging gardens - both are incorporated. The tower symbolized the meeting point between Earth and Heaven in the greatest city of the world's first civilization. It was an extremely cosmopolitan place for the time and in the biblical tradition, where the tower is seen as an act of defiance, God destroys it and divides mankind by creating languages in order to restore his authority.

I don't know if it should be seen in the original spiritual sense or in the biblical one, as a Promethean act of rebellious ambition (in NY, without a doubt a secular city, skyscrapers do loom high above churches). But I'm pretty sure that fundamentalists see them as evil creations of human arrogance and that it played a part in the fact that the twin towers were chosen as targets of destruction. So reasserting our faith in such structures will in my view signify the triumph of civilization over obscurantist beliefs.

amigo32
December 28th, 2002, 09:25 PM
Bravo! *:biggrin:

Kris
December 29th, 2002, 05:25 PM
A recent article about the problems tied to the ideas of underground memorials: http://www.nytimes.com/2002/12/20/nyregion/20REBU.html?pagewanted=print&position=top

Kris
June 23rd, 2003, 04:11 AM
June 23, 2003

A Wall Once Unseen, Now Revered

By GLENN COLLINS

http://graphics7.nytimes.com/images/2003/06/23/nyregion/23wall.jpg
At the World Trade Center site, crews are using concrete reinforced with steel to stabilize the section of the wall that shifted after the attack. Workers are coating other segments with liquid concrete.

The wall.

Once it was the invisible 3,300-foot-long perimeter of the World Trade Center. But now this anonymous bit player has became a star in the epic story that is the multibillion-dollar reconstruction effort at ground zero.

Rugged, utilitarian: these are perhaps the warmest words that could reasonably describe this concrete bulwark that was never intended to be seen. Even its nickname, the bathtub, is unglamorous, though it describes the role of the pebbly three-foot-thick slab that has kept the waters of the Hudson River from inundating the twin towers' foundations since before the towers were built.

But to legions of tourists who have photographed it, the wall has become beautiful in its brutalist simplicity and cherished for the circumstances of its survival.

And if Daniel Libeskind's architectural blueprint for ground zero is heeded, the wall could become an icon of American patriotism. Since the wall withstood the terrorist attack, Mr. Libeskind said, "it stands for the indomitable spirit of New York and as a miracle of engineering as well."

Many elements of Mr. Libeskind's design are in flux, but he is adamant that the wall be displayed as the centerpiece of the new memorial at ground zero. The Libeskind plan calls for the exposure of a 300-foot stretch of the wall at West Street near Vesey Street. "It is the trace of the actual attack," Mr. Libeskind said, "the witness to it. It speaks to the power of what is unchangeable, and unchanging, there."

Then, not unlike the Liberty Bell, the wall could be cherished by generations of tourists.

But only if it remains standing.

After all, it is no longer vital that the Liberty Bell ring. But it is still essential that the wall tame the Hudson River.

And so, engineers have intensified a monumental conservation effort. This $4 million repair job is but a part of the $200 million effort to brace the entire ground zero site and create a foundation for the memorial.

In April, Gov. George E. Pataki said that the stabilization of the wall was a priority and that it must be completed by the third anniversary of the disaster in September 2004.

All involved, from those overseeing the operation to the hard hats down in the pit, bring unusual emotion to the work. Joseph J. Seymour, the executive director of the Port Authority of New York and New Jersey, which owns the trade center site, said that the first moment he saw the wall, "I was moved by it."

"The wall withstood the attack and saved the lives of people who were in the trade center," he said.

Peter L. Rinaldi, the Port Authority's general manager at the trade center site, protectively calls it "my wall," saying, "This will never be just another construction project."

Front-line repair crews share more than respect for the rough-hewn structure. "We are working on something that belongs to history," said Ramon Rodriguez, 33, who was hefting a 40-pound nozzle that spews 50 cubic yards of concrete a day onto the wall in the stabilization effort. "I made it a point to be here, because I wanted to help out."

George Tamaro, a 66-year-old engineer who helped oversee the wall's construction for the Port Authority from March 1967 to April 1968, said the original accomplishment "had never been achieved at that scale." Now a consultant with Mueser Rutledge Consulting Engineers, he was called in on Sept. 12, 2001, to help stabilize the wall and is monitoring its conservation.

For 25 years now, the wall has kept the Hudson River at bay. The slab is not actually holding back the river, which is more than 150 feet to the west. But it holds back the dirt and stones that hold back the waves; nevertheless, brackish water seeps between the panel joints and around the tieback tendons that stabilized the wall during its construction.

The bathtub was constructed in 22-foot sections. In each, as builders dug down 70 to 80 feet to the bedrock of Manhattan schist, they injected a slurry of water and bentonite, a soupy clay dense enough to keep out the groundwater and push back the soil. After reinforcement cages of steel rebar were lowered into the trench, liquid concrete was pumped in, forcing out the bentonite.

For more than two decades after the trade center took its place in New York's sky, the wall was hidden to all but the slide-rule cognoscenti who revered it as a landmark engineering achievement. "You could sneak in and see bits of it in the basement parking lot," Mr. Tamaro recalled.

The slab was designed to withstand a force of 3,500 pounds per square inch, but it probably could withstand 5,000, Mr. Tamaro said. It endured damage from the terrorist bomb that exploded in the trade center garage in 1993. Then it was unimaginably tested on Sept. 11, 2001, when the wall held through the impacts of the hijacked jetliners and the collapse of the south and north towers, which generated temblors of magnitude 2.1 and 2.3, respectively, as measured by Columbia University's Lamont-Doherty Earth Observatory in Palisades, N.Y.

In accomplishing what it had never been designed to do, the wall enabled thousands of people to flee the towers. Its collapse could have undermined the twin towers earlier, trapping more workers; a massive inundation could have destabilized the foundations of other buildings and impeded recovery efforts.

But its survival was a near thing. After the towers collapsed, the southern margin of the wall moved about a foot, bellying like a concrete dam about to burst. According to Mr. Tamaro, 40,000 cubic yards of backfill was brought in to stabilize a 300-foot-long section. Then new steel tieback tendons the stabilizing rods that visibly stud the bathtub walls were driven in deeply, stapling the wall to the bedrock. When the backfill was removed, the wall withstood.

But will it hold? "It's hard to say what the stresses on the wall are now," Mr. Tamaro said. "Which makes me edgy. Engineers like to have some precision to what they are doing."

He added, "We believe that the wall is safe." He does not foresee a collapse, "but it is possible that pieces could fall free, joints could open, and water could come in."

In Europe, there are sections of 1,000-year-old Roman concrete still very much in use, but the slurry wall "is in an aggressive climate, adjacent to the Hudson River, with a very high water table, and subject to the freeze-thaw cycle," Mr. Tamaro said. It can, if protected and braced properly, last a long time. "But the natural life of the wall is not going to be hundreds of years," he said.

Tony Cracchiolo, the Port Authority's lead project manager at ground zero, noted that the wall had been open to the elements and "has been exposed to stresses and weather that it was never intended to face."

So porous was the wall that, last winter, at the 30-foot level marking the winter water table, ice formed stalactites on the concrete, giving it the look of a frozen Niagara Falls.

Danger to the wall, engineers said, involves a process that geologists call mass wasting: the thaw and freeze cycle that will transform the Himalayas into foothills one day. As water becomes ice, it expands in the cracks of both walls and mountains.

In their efforts to slow entropy, Port Authority engineers say they need to brace the slurry wall. "That's why the base of the memorial will be 30 feet deep instead of 80 feet deep," said Mr. Seymour, the Port Authority executive director. "The wall can't survive if it is totally exposed." (Mr. Cracchiolo, the project manager, hopes that at least a small section of the entire height of the wall can be displayed.)

At some places, such as the Liberty Street side, where the wall bowed about a foot out of true, the engineers are lining the wall with steel-reinforced concrete to prop it up. Elsewhere, leaks from the junctures between the wall's 22-foot-wide panels are being caulked by liquid grout injected into crevices by a high-pressure hose.

Workers, including Mr. Rodriguez, have been repairing the wall, then spraying on a coating of shotcrete, a grayish liquid concrete. This treatment has the effect of making over the old rust-stained, tortured wall which seemed to embody the collective suffering of the lost into a somewhat upgraded wall that is nevertheless still stunningly bleak, streaky and stubbly.

The replacement of crumbling concrete and snapped steel is necessary, Mr. Tamaro said, to increase the wall's stability. Under discussion are plans for putting this exposed section of the wall behind glass, Mr. Cracchiolo said, "to protect it from temperature changes and humidity, like at an archaeological site."

The initial stabilization effort should be complete within a year. Looking ahead, though, Mr. Tamaro cautioned, "There are more question marks about the wall than answers."


Copyright 2003 The New York Times Company

ZippyTheChimp
June 23rd, 2003, 07:17 AM
...said that the first moment he saw the wall, "I was moved by it."

Ernest Burden III
June 23rd, 2003, 09:38 AM
You may all have already seen this, but there are plans and a few sections of the bathtub here (URL below) made available for the memorial competition. *These are not the most complete documents LMDC has (they had full plans and 3D models of lower manhattan for the buildings competition. *But there are a few things that are different (and so likely updated) and these incluse some info about the winning design.

I heard the number of entrants to the new comp. is up to 13,000

http://www.wtcsitememorial.org/downloads/index.html#5

Jasonik
June 23rd, 2003, 08:35 PM
In Europe, there are sections of 1,000-year-old Roman concrete still very much in use, but the slurry wall "is in an aggressive climate, adjacent to the Hudson River, with a very high water table, and subject to the freeze-thaw cycle," Mr. Tamaro said. It can, if protected and braced properly, last a long time. "But the natural life of the wall is not going to be hundreds of years," he said.

Is the memorial for posterity or a temporary feel-good gesture? *If the permanence of the memorial is compromised by exposing the wall, why do it? *How dramatic would a half submerged memorial be for a civilization more concerned with vacuous emotive political tokenism than solid permanence, (ironically what the wall is meant to symbolize). *Am I thinking too long term here? *

Jasonik
August 11th, 2003, 09:24 PM
The Hidden Hero of 9/11
George Tamaro's Sunken Wall Held Back the Waters at Ground Zero, Then Emerged to Shape the Memorial There

By Lynne Duke
Washington Post Staff Writer
Monday, August 11, 2003; Page C01


Second of two parts (http://www.washingtonpost.com/wp-dyn/articles/A39481-2003Aug9.html)

NEW YORK -- Deep in the pit that is Ground Zero, George Tamaro climbs atop a concrete knoll. He's trying to get a closer look at an engineering wonder -- the giant concrete slurry wall his team built some 30 years ago.

He made his professional name with this wall. In fact, you could call it Tamaro's wall, except that the 66-year-old structural engineer with the squat frame and wide smile is a practical man, not given to pretense. He cringes at the very suggestion that he could claim this wall as a personal masterpiece.

"It's a pretty ugly wall to fall in love with," he says with a sarcastic laugh.

It's raw, for sure, and rough in texture, definitely not a work of art, and not meant to be visible at all. And yet it has become very much a public symbol.

Tamaro peers out from under his white hard hat, explaining the engineering of this wall. It's a three-foot-thick, 70-foot-high expanse of steel-reinforced concrete socketed right into the Manhattan bedrock and stretching straight up to street level. It's studded with the huge heads of hundreds of anchors -- drilled diagonally into the bedrock, each able to withstand 300 tons of pressure -- to keep the wall upright. It spans 3,300 feet in all, enclosing the twin towers' foundations much like a giant underground bathtub, except that instead of holding water in, this was a tub designed to keep it out.

After hijacked jetliners smashed into the World Trade Center, the wall kept the waters of the Hudson River at bay. Though crushed and cracked in some places, the wall held. Stressed, yes; nudged from its original position and leaning ominously in one stretch; leaking groundwater -- but standing.

Daniel Libeskind, designer of the planned trade center redevelopment project, has imbued the wall with heroic status because it was all that was left of the obliterated trade center complex. But Tamaro, who has been a voice of engineering reality for the Libeskind team, views the wall in strictly technical, structural terms. He knows the wall's stresses, like the freeze-thaw cycle that left 50-foot icicles last winter. He knows, also, that there is much that's unknowable, unseeable, within the concrete. Will it hold? Is it protected and secure? Is the earth around it moving? Is the groundwater or Hudson River water encroaching?

With the wall set to become perhaps the most emotionally evocative element of a memorial site whose design is to be selected this summer, Tamaro has been preoccupied with how to keep that wall permanently standing.

You learn all this and it becomes clear: This wall definitely does not belong to Tamaro. Quite the opposite. It is Tamaro who belongs to the wall. He is its servant, maybe even its conscience, but definitely, he says, its voice.

"Somebody's got to speak up on behalf of the wall," he says with a shrug. "Somebody's got to speak up and protect it."

In years to come, visitors to the 16-acre Ground Zero site will walk down a long ramp leading into the bathtub, where they will see a memorial -- as yet to be designed -- to the thousands killed in the terror attacks. A huge memorial competition now is underway here. More than 5,000 people from around the world have submitted designs, and a winner is to be announced in September.

Whatever the memorial turns out to be, it will in no way rival the eerie, awesome backdrop of that strange and lonely wall. In the sunken memorial garden that Libeskind has designed, the wall will stand, largely as it does today, with one section left fully exposed down to the bedrock. That in itself will memorialize much of the raw sorrow and hope of 9/11.

But like a patient whose condition requires constant monitoring, even today, nearly two years after the attack, the wall is still not out of the woods. It is being closely watched for signs of trouble. Repair and restoration are ongoing.

"There are repairs to the joints where there are leaks," says Tamaro, listing some of the work still underway. "There is the removal of the delaminated concrete," which means concrete that is splitting into crumbling layers. "The cleaning of the steel. The restoration of the surface."

As he speaks, there's an edge in his voice, as if there remains much yet to be done, as if he's nervous about that wall.

"I am nervous by nature," he admits. "In a sense, it's my job to worry about these things and make sure nothing happens that's risky."

As it has been since shortly after the terror attack, the wall is marked with orange surveyor points so it can be periodically measured for any new movement. Along the entire perimeter of the bathtub, slope indicators are installed in the ground. They will detect any land shifts that could affect the wall. And water level monitors will detect the dangers of rising groundwater at the site. Earlier on, when flooding was a constant threat, engineers even drilled wells outside the bathtub to relieve the groundwater pressure.

The wall is secure for now, but not forever. That's the battle that lies ahead.

Tamaro wanted, in earlier years, to be an architect. Somehow, though, he was lured underground, lured into the world of the Moles (a society of engineers who work underground, to which he belongs).

As a young engineer for the Port Authority of New York and New Jersey back in 1967, Tamaro was tapped to apply a new foundational technology -- the slurry wall -- to the base of what would be the world's most ambitious construction project: the 110-story World Trade Center. After blasting into the bedrock, Tamaro's team used a clay-like soil and water mixture, known as slurry, to form the base of the concrete wall they would build.

Later, Tamaro became a partner in Mueser Rutledge Consulting Engineers, a large structural engineering firm that specializes in below-ground work. Mueser Rutledge built the slurry walls and foundations of the District's new convention center as well as the Ronald Reagan Building, and the huge World Financial Center complex across from the trade center site.

That financial center project was Tamaro's baby, so to speak. And it remains one of his most challenging, he says. It included the construction of two slurry walls to create the foundations of the four-building complex, part of which sits on concrete decks built right atop the Hudson River and anchored into the bedrock below the river bed.

From the World Trade Center to the World Financial Center, Tamaro's career has tracked Manhattan's east-west expansion. The city's liberal use of landfill over the years has created a Hudson River shoreline much farther west than nature had intended.

His midtown office tells of the depth of his labors below ground, below sea level. There are several old bottles from the Colonial era, four cannonballs dated to the Revolutionary War and a ship's wooden pulley. He hoped that perhaps the 1960s excavation for the trade center would yield clues about the Tijger, a Dutch vessel that burned and sank in the Hudson River in 1614.

He is, at heart, a sailor. Perhaps that's because his father was a sailmaker. Among the memorabilia on his wall is his ship's operating license from the U.S. Coast Guard. Up in Martha's Vineyard, where he spends part of his summers with his wife, Rosemary, a retired Montessori teacher, he sails a 17-foot catboat.

On Sept. 12, 2001, New York City officials phoned Tamaro and his firm for help. Before the armies of architects would arrive, before the artists and designers would take their shot at designing a memorial, Tamaro and company were on the scene to guide firefighters and emergency workers through the subgrade site, which was filled with booby traps for the men and machines searching for victims amid the tons of debris. (And down in the District, meanwhile, his son, Mark, a structural engineer, would end up working with FEMA on the Pentagon site. The three other Tamaro children are in architecture, computers and finance.)

Within the trade center bathtub, which held seven below-ground floors, there were unseen vent shafts, ramps, stairwells and commuter train tunnels. Each of them was a potential booby trap for the recovery workers. Tamaro needed to make sure the work crews knew these delicate locations, as well as the outlines of the slurry wall. He feared the crews would park their heavy machinery atop the wall and unintentionally cause further damage.

When the towers collapsed and crushed just about all of the seven subfloors, they also smashed the lateral supports that held the walls upright. The subfloors, which once housed parking garages, mechanical plants, storage areas and a commuter train concourse, were built right into the slurry wall and thus braced it against collapse. Without such support, the walls could succumb to the pressures of the soil and water pressing in from all sides.

For a time, the 1.8 million tons of compacted debris from the towers' collapse helped to hold up the slurry walls. But the debris' removal revealed the extent of damage the wall had received -- and the extent of repair work that would be required.

The debris had crushed a 100-foot stretch of slurry wall on the site's east side, along Greenwich Street, and pushed the wall 41/2 feet inward. Along Liberty Street, on the south side, the upper sections of the wall leaned inward about 10 inches because of lack of support.

As portions of the wall were exposed the process of anchoring the wall began. Tamaro's team drilled the huge anchors, called tiebacks, into the wall. Where the wall was crushed, it was rebuilt first.

Those anchors are not intended to hold the wall permanently, Tamaro says. Only subflooring of the kind destroyed in the terror attacks can give the wall the kind of support it was intended to have. But Libeskind's design for the site called for the slurry wall to be largely exposed, with no flooring to hold it up.

As protector of the wall, Tamaro held tremendous sway in shaping the wall's role in Daniel Libeskind's memorial garden design.

While Libeskind is focused on the grand concepts, Tamaro is one of the people who tell him what is and is not possible. What can actually, physically, technically, be accomplished.

"We're looking at this from two different perspectives," Tamaro says. "To him, it's an important design component and it has great significance as something that started the project and is the only thing that remains. To me, it's a barrier between 2,000 people in the [commuter] station and the Hudson River."

Libeskind, who speaks effusively of the wall's significance, once wrote of it: "The foundations withstood the unimaginable trauma of the destruction and stand as eloquent as the Constitution itself asserting the durability of democracy and the value of individual life. We have to be able to enter this hallowed, sacred ground while creating a quiet, meditative and spiritual space. We need to journey down, some 70 feet into Ground Zero, onto the bedrock foundation."

But Tamaro told him it couldn't be done. There would need to be flooring of some kind in the bathtub. Tamaro, if he had his druthers, would give back to the wall what it lost.

"From purely an engineering point of view, I would prefer to have floors all the way up to grade, so that I could restore the underground supports that were there before," he says.

In the end, both Tamaro and Libeskind had to compromise. Instead of journeying down 70 feet, tourists now will journey down about 35 feet -- beneath which will be two levels of slab flooring to brace the wall, as Tamaro deemed necessary. And the upper reaches of the wall -- the 35 feet left exposed -- will have to be supported by a truss or brace scheme that Libeskind says he will gladly provide.

The two men, though coming to the wall from different starting points, say there is no conflict between them on the need to secure it.

"Of course, we have to work within George Tamaro's perameters," Libeskind says. "Whatever we've done was done in close collaboration" with Tamaro. He doesn't feel his style was cramped by Tamaro's technical dictates.

Libeskind believes the power of his design emanates in large measure from the symbolism of that wall. He doesn't think of it as a ruin. He believes its message is one of life.

"It says, 'I survived and I'm here and look at me!' "

But Tamaro hears a different message from the wall. It is one word, a word that he hopes he can silence, and leave the wall in peace. Because even now, nearly two years later, he hears the wall groaning, "Ooouuuccchhh."


2003 The Washington Post Company

TonyO
August 12th, 2003, 03:28 PM
I have to say something about this. *In the effort to memorialize anything at ground zero, this 'deifying' of the slurry wall is sad. *Its bad enough that the memorial is going to be a pit...then on top of it all trying to tell everyone that it is justified because it is so amazing. *Any foundation that has that much rubble on top of it is going to be intact. *Its just physics folks.

NyC MaNiAc
August 12th, 2003, 11:53 PM
Whatever. Let them glorify something that's not so special. As long as I get my towers, I really don't care. I don't believe in a memorial there to begin with, so I won't even start.

Kris
August 13th, 2003, 03:01 AM
The "exploit" is to have withstood the impacts of the planes and the collapses.

billyblancoNYC
August 13th, 2003, 10:54 AM
What can you say, it's just another example of the "touchy-feeliness" that everyone seems to be so fond of these days. *Footprints, slurry walls. *Just so we can reminisce, let's just throw tons of burnt rubble, ash, and stell on top of the site and take it all in - for posterity.

ZippyTheChimp
August 13th, 2003, 05:31 PM
Your wish for twin towers is a memorial.

Freedom Tower
August 14th, 2003, 12:11 PM
I just hope it's not too ugly. Leaving the slurry wall permanently exposed! I dont know if thats the best idea. Maybe they can have a really small section with a window you can look in on it with, but the whole thing out in the open, im not so sure.

NYatKNIGHT
August 14th, 2003, 12:31 PM
Let's see what they do with it before we air all our grievances. No offense, but at this point if I had to choose between all you complainers' vision of a good memorial setting and Libeskind's.......

billyblancoNYC
August 14th, 2003, 12:49 PM
I think the design now is great. *Leave well enough alone. *It's the fact that people continue to push and change, etc. Let the thing pan out. *No one, other than a handful of people, want a 16 acre memorial. *End of story. *NYC is about reinvention, development, commerce, etc... and memorialing this tragedy.

Kris
November 22nd, 2003, 11:12 PM
November 23, 2003

Ahead of Any 9/11 Memorial, a Wall Bears Witness

By JAMES GLANZ

http://graphics7.nytimes.com/images/2003/11/23/weekinreview/Glanz650.jpg
Parts of the slurry wall bear scars of the towers' fall. A photo of one victim hangs from a yellow ribbon.

THE gargantuan physical remnants of the World Trade Center often carried an emotional power beyond anything the original buildings could muster. Early on, the Gothic shard of the south tower's steel facade loomed darkly above the smoking ruins at ground zero. Then workers found the immense bronze globe by the sculptor Fritz Koenig, once perched 25-feet high in the center of the plaza, now horribly puckered and punctured by falling debris.

And most enduringly, there was the slurry wall, popularly called the bathtub wall because it was designed to hold back groundwater fed by the Hudson River. The first part of the trade center to be built and now virtually the last of the original structure to remain it served as a foundation wall for the complex, stretching more than 3,000 feet around and some 70 feet down into the Lower Manhattan soil.

"As eloquent as the Constitution itself" was how the architect Daniel Libeskind described the wall after his first descent into the pit more than a year ago, when its rusting steel reinforcing bars, jagged textures and dark streaks bore witness to the violence of the towers' collapse on Sept. 11. Mr. Libeskind made it one of the central motifs of his master plan for rebuilding the site, and last week, when the finalists in the competition for the memorial design at ground zero were revealed, they featured as much as 1,000 feet of exposed slurry wall.

But as the fancy and somehow dainty models were unveiled at the sparkling Winter Garden, the current state of the immense, sunken, muddy ruin of what was the trade center, just across West Street, raised questions about how any of the high-concept presentations would incorporate the physical reality there.

The wall, for instance, is no longer what it was when Mr. Libeskind first felt its power. With little public discussion, the Port Authority of New York and New Jersey, which owns the site, has covered most of the surface with shotcrete essentially a form of concrete blasted through a hose.

George Tamaro, the 66-year-old engineer and partner at Mueser Rutledge Consulting Engineers who oversaw construction of the wall in the 1960's, said the work was necessary to preserve the wall from further degradation. And he said that, sadly, the wall that inspired Mr. Libeskind had quietly vanished.

"I think that's gone," said Mr. Tamaro, who advises the Port Authority on the wall. "It will never be what it was a year ago. I think that what he saw, what we all saw at that time, was very eloquent and it was powerful." But because of the wall's structural imperatives, Mr. Tamaro said, "what he saw was not going to remain."

In an interview, Mr. Libeskind said that because the slurry wall was not merely some traditional romantic ruin a pile of stones to be marveled at but continued to function as a bulwark against the water, its changes were part of its appeal.

"Ruins are dead buildings," Mr. Libeskind said. "But to expose a living foundation, that's something totally new. It's about the livingness of that wall. So the fact that the wall is changing, the fact that there is water in it, that it's breathing, that it's freezing in the winter, and that structurally one has to take care of these things and protect the wall it's like an ongoing affirmation."

Mr. Libeskind said he saw the wall as a palimpsest, with various layers of meaning corresponding to different epochs of its history. And Kevin M. Rampe, president of the Lower Manhattan Development Corporation, which is organizing the memorial competition, pointed out that there are still portions of the wall that have not been coated with shotcrete.

"I think that at the end of the day, we'll see some of the slurry wall exposed," Mr. Rampe said. But he said that more advanced and presumably more revealing coatings could be considered for what remains of the raw surface.

Still, some see the shotcreting of the wall as the latest in a series of decisions made out of the public eye that have had a huge impact on ground zero artifacts. Soon after Sept. 11, with no public announcement, the city began recycling steel recovered from the trade center. Even federal investigators who were studying why the towers collapsed were taken by surprise. (They were later given permission to save selected pieces.)

The Port Authority also decided to partially repair the Koenig globe, making it generally spherical again. The result, on display at the Battery, retains plenty of evidence of trauma to some eyes and is reminiscent of an unsatisfactory fender-repair job to others.

"It's definitely a pattern," said Mary Fetchet, who lost her 24-year-old son, Bradley, in the attacks and is the chairwoman of Voices of September 11, a family advocacy group. "There's so many decisions that have been made behind the scenes, that haven't been discussed, and the site is being compromised as a result."

The two engineers most responsible for building the original wall were Mr. Tamaro, then a young Port Authority engineer, and a husky Italian contractor to the agency named Arturo Ressi di Cervia. The novel method of construction involved digging a three-foot wide trench where the bathtub wall was to run and then filling it with a watery gray slop called bentonite slurry, which kept the soil from collapsing into the trench.

Then concrete was squirted into the bottom of the trench, forcing the slurry out. When the concrete hardened, its surface was imprinted with the textures of the soil. It looked ancient from the moment the trade center basement was excavated and the inside of the wall was exposed. The wall was covered up when the rest of the trade center was built above it, but exposed again scarred and battered and somehow looking even mightier and more dignified when debris from the collapsed buildings was pulled away after Sept. 11.

The potential visual impact of the wall was reduced when the development corporation agreed to raise the floor of much of the memorial some 30 feet, among other reasons, to help support the wall. Further cluttering the view would be large structural supports to add more stability to the wall.

For Mr. Libeskind, though, those factors simply add to the wall's appeal as an element of the memorial designs.

"Every time I go down there, I always have the same kind of breathless feeling," he said. "This is an amazing wall in every sense physically, spiritually. That wall has a heroic place in the city, and it's not a heroism that is put on top of it by rhetoric. But it's there for everybody to see. And you can touch it."

James Glanz and Eric Lipton, both reporters for The New York Times, wrote "City in the Sky: The Rise and Fall of the World Trade Center" (Times Books, 2003).

Copyright 2003 The New York Times Company

emmeka
November 23rd, 2003, 04:55 AM
It looks so menacing, it instantly depresses you.

NoyokA
November 23rd, 2003, 11:21 AM
I would compare the slurry wall as the equivalent of the Vietnam Memorial. Although I was never overrally impressed by the design of the Vietnam Memorial, touching the wall was a powerful expierence. As such the cold and texture of the slurry wall would have an effect on many for their own many different reasons.

JMGarcia
November 23rd, 2003, 06:55 PM
I took that PATH train, which re-opened today, through the site and you get a good, close-up view of the full 70 foot height of the slurry wall from the bottom of the pit.

It was more impressive than any of the current memorial proposals and their faux treatment of the footprints. The slurry wall is the real thing, outlining the footprints with new construction is not.

It's a shame none of the proposals make the slurry wall more of a centerpiece to their design. I guess the designers felt that they wouldn't be being original if they paid too much attention to. Ego first I guess. ;)

ZippyTheChimp
November 23rd, 2003, 10:26 PM
It was more impressive than any of the current memorial proposals and their faux treatment of the footprints. The slurry wall is the real thing, outlining the footprints with new construction is not
I felt that way the first time I saw it dug out. I would have liked to see a proposal with just the portion of the slurry wall, maybe 150 ft, exposed all the way to bedrock and tied in the a footprint. They could have engineered a support system for a small enough section.