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Building Freedom Tower

February 2007 Installment of the Monthly Journal 

[Read the sidebar, Building Freedom Tower -- The Journal for introduction]

By Dick Sheppard

February 12, 2007

Progress and Protraction?

Since the hoopla surrounding the emplacement of Freedom Tower's initial columns several weeks back, there has been a subtle and not-so-subtle shift in activity across the entire WTC construction site. The subtle aspect is taking place at the Freedom Tower zone, where, following the celebrated emplacement of the initial steel columns, there's a noticeable decrease in activity. (More about that below.)

Video Coverage for this Story:

A Tight Fit, Part I

A Tight Fit, Part II

A Tight Fit, Part III

The not-so-subtle activity is taking place at the southeast corner of the WTC site, right near the intersection of Church Street and Liberty Street. There, the Port Authority's contractors are energetically going about their building of the "eastern bathtub" retaining walls. The wall will run from approximately where the north-extending Greenwich Street will enter the rebuilt site at Liberty (diagonally across from the Ladder 10 firehouse, wth it's bronze wall memorial). 

It heads east for the block along Liberty to Church, then it will turn north on Church, and run several blocks north up to Vesey Street. The wall will turn west on Vesey to a point where the new Greenwich Street will emerge on the north side of the site, right about where West Broadway begins it's run north into Tribeca. The wall will encase the "eastern bathtub" within which the three Church Street towers rise: Building Two at the north end of the eastern bathtub, and building Three and Four south to Liberty. This new bathtub will compliment the already existing "western bathtub," within which the original World Trade Center Towers rose, and within which Freedom Tower will rise in the northwest portion.

Rebar cage sags while being lifted to vertical for insertion into wall section trench.

The Port Authority is obligated to create the eastern retaining bathtub so developer Larry Silverstein can erect the massive towers that will be Freedom Tower's eastern neighbors. Presently, there are three types of cranes working on the wall project right there at Liberty and Church. First, there is a very tall heavy-lift crane, which handles all manner of lifting tasks and one important slurry wall task (about which more below). Alongside that major crane, there are four smaller booms/cranes, two each of a specific type. There are two clamshell scoop cranes, digging a deep and approximately 3-foot wide trench. These cranes send a massive rectangular unit containing a clamshell at its base deep down into the trench, scooping out mud down to the Manhattan schist that underlies the entire site.

 As that trench is dug, a dense "slurry" mix - water and a clay-type substance, is pumped into the deepening trench to prevent it from collapsing or closing up on itself. 

Once the clamshell has dug out as much material as it can, and hits schist, the second type of crane -- of which there are two of these on site -- takes over. One construction worker termed this crane-type a "milling machine." I need to get additional details, but this third type of crane sends a large rectangular unit into the trench to "mill" the bottom rock smooth, I surmise. It also has hoses dangling from two large pulleys; it may be pumping slurry into the trench too. My guess is that the schist at the bottom of the trench has to be "milled" smooth to get to the next step. Because while the clamshell and milling cranes are working, so are the "ladder" men.

"Ladder men" is construction lingo for the workers who put together the steel concrete reinforcing bars, the "rebar." When completed in stand-alone fashion, rebar is usually more "cage-like" structures than "ladderly." But if the construction guys want to call their fellow tradesman "ladder men" instead of "cage men" this novice isn't arguing. Right near the corner of Liberty Street and Church Street, the ladder men are busy.

You can't see them from the street, because much of the entire WTC site is at least partially obscured from street-level. Arriving on the PATH directly into the existing "west bathtub," one gets the best view of the western site you can get outside a direct tour. From above, in my office, I can stand on the air-conditioning alongside the office windows and look directly down onto the Liberty/Church wall construction on the east side. From above, you can see that the ladder men are constructing long, rectangular cages of rebar, lying flat alongside the trenching operations. Already, as reported in the NY Times a few weeks back, the first of these rectangular steel cages has been lifted by the largest on-site crane, and pulled skyward. Once so raised, the rebar might resemble a ladder, but a ladder it isn't. Instead, the large crane swings the rebar over to one of the recently dug trenches, and ever so slowly lowers the entire rebar cage into the trench. Then the slurry gets pumped out, the rebar supports the trench, the actually wall concrete is poured in. Viola, an approximately 50-60 foot deep vertical section of wall, about 10 across and three feet thick is in place. 

I witnessed just such a rebar-into-trench placement operation, and it's a sight to behold. As the rebar is lifted from lying flat to vertical, it sags, bending and thereby belying it's reinforcing strength. But it's not designed to be horizontally robust, but vertically so. As the crane slowly pulls it completely vertical, the hanging cage-like rebar, about 60 feet tall, assumes it's final shape. And as the rebar is lifted to vertical, you can see that during assembly of the cage, workers have installed "tieback" insertion brackets. I'm not sure if happens before the concrete is poured to form the wall, or after, but long rods will be slipped into these brackets and drilled into the surrounding dirt and rock to fix and stabilize the wall in place until the understructures of the final skyscrapers will hold the wall in place. 

Heavy-Lift crane lowers rebar into trench.

When the WTC was destroyed on 9/11/01, a section of the existing "western bathtub" wall along Liberty Street buckled and had to be re-shored with tiebacks to prevent a wall collapse/failure.

In present operations, ever so slowly the heavy-lift crane swings the massive cage over to the awaiting trench. Two steel columns have already been inserted into the trench, to serve as a sort of "notch" into which the rebar will slide. Gradually, the crane lowers the rebar into this notch where it awaits tying-back and concrete pouring.

According to a recent NY Times article in their coverage of the very first section of the wall being completed, mention was made to the effect of, "one down, 62 more to go!" So there's an awful lot more trenching, slurrying, and rebarring, work to be done. And then when the wall is in place, the very ground on which everyone, and all the equipment, are working will be dug out and carted away. 

Then Larry can fill the resulting huge, deep hole - the new "bathtub" - with huge soaring buildings. As with all of the construction in the wide area within and alongside the WTC zone, the workers go at it with a purpose, often they're at work when I'm passing nearby shortly after 7am.

Milling crane in foreground heavy-lift crane with rebar prepares to swing rebar into wall section

That's encouraging, but there are hints of a potential slow-down on the Big Job itself: Building Freedom Tower. As mentioned above, activity there has been subdued since the noteworthy raising of the first columns. There's activity at the site, but since the first noteworthy columns were emplaced over a month ago, nothing too visible is taking place in the Freedom Tower zone. And while this pause might be discouraging, the reason might make some sense. The NY Post's Steve Cuozzo wrote an interesting column during the week just ended (2/10/07).

Milling crane in foreground heavy-lift crane with rebar prepares to swing rebar into wall section.

Steve was thinking out loud about some things people in the big development field have been discussing not-too-loudly. And that is: slow down on Freedom Tower. The reason is counter-intuitive - after all of the delays, the steel is rising, let it rise! Yet, as Steve explained, maybe it makes more sense to build the Church Street buildings first, or get them well underway and signing leases. Prove the vibrancy and viability of building at the WTC site; let those buildings, with huge floorplans/plates, attract top-flight tenants. Don't let Freedom Tower lead the lease pack, because of the uncertainty still of how potential Freedom Tower tenants approach inhabiting that iconic tower. First, there's the fact that much of Freedom Tower may be leased to government entities, which may reduce private sector interest as commercial entities sometimes shy from too many government co-tenants.

Second, there's the reasonable safety concerns still when discussing occupying this symbolic building. Thus a wait-see approach might be prudent: Get the Church Street buildings built and leased, and some of the Freedom Tower issues could be overcome as tenants are drawn to a what at that point would be a super-charged, super-prestigious location. There's no need then to "force" Freedom Tower aloft, it will create it's own demand if the timing is right. As much as the credo of this diary has been, "Build, build, build!" a business-driven delay at this point is tolerable when compared to the previous maddening political and designs delays. 

If it takes that much longer for Building Freedom Tower "the right way." In a way that makes economic sense for both Larry Silverstein and the ultimate viability of the entire rebuilt site, I can live with that! The ultimate goal beyond filling that void in the Lower Manhattan sky is a pre-eminent, twenty-first century, and world-renowned memorial, business, and public center; that's the requirement and I think it's encouraging that people are thinking in innovative ways, if a little late in doing so.

 

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