Almost a decade after the attacks of 9/11, much of the new World Trade Center site remains under construction, with signature pieces like the Freedom Tower, the Frank Gehry performing arts pavilion and the 9/11 Memorial registering as little more than architectural renderings to most New Yorkers. But for the past seven years, at least one project right in the middle of it all has been fully operational � although not in its fully realized aesthetic glory.

Spanish architect Santiago Calatrava, celebrated for his perfectly engineered minimalist transit centers around the world, was selected to design the WTC PATH Hub. He unveiled his vision � a multi-level underground arcade with clean lines, soaring arches, and light filtering 60 ft down to the train platforms of Lower Manhattan. The centerpiece was a grandiose retractable roof whose 150-ft-long crossing spikes were inspired by the wings of a dove.

That was 2004.

As the economy turned in 2008, and costs on the more than $2 billion project became a serious concern, the wings were trimmed: the roof will no longer open, the spikes have been cut down to a more pedestrian length.

�There are literally hundreds of stakeholders at the World Trade Center site, and all of them have a say on some level to what happens here,� says Gary Winsper, project executive for the joint venture between Skanska USA Civil/Northeast, Granite Construction Northeast/Skanska USA Building, which is responsible for the $540 million contract above-grade. �No one can figure out the dynamic or anticipate all that.�

The work, however, never stopped despite the changes. The temporary station�s capacity today is the same as the original was before it was shut down after Sept. 11. During a mid-day visit, the space looks roomy, the eight escalators leading down from the Vesey Street entrance are comfortably sparce � but its full capacity is 50,000 daily commuters.

�The system�s gotta operate for rush hour,� says Mark Pagliettini, Assistant Director for the Port Authority on the World Trade Center Transit Hub, as he stared at the escalators that would be jam-packed in just a couple of hours.

Even in its temporary phase, the station is huge by any standard. Over 550 tons of temporary steel alone has been erected, according to PANYNJ, and all of it will have to be removed. The station is scheduled for completion in 2014, but, as Pagliettini points out, it never stopped running.

But from inside the station, it�s hard to imagine what the final version will look like, designed to accommodate the 250,000 riders projected to use the hub by 2025. The final station will use more than 22,000 tons of structural steel, roughly twice the amount used on the new Yankee Stadium. The Calatrava design covers 800,000 sq ft, complete with 500,000 sq ft of retail and restaurant space. It will be �the most integrated network of underground pedestrian connections in all of New York City,� according to the Port Authority, connecting PATH trains, 13 subway lines, the Battery Park City Ferry Terminal, the WTC Memorial, Towers 1 trough 4 and the World Financial Center. More than $590 million will go toward security infrastructure alone.

The majority of the work is hidden behind the ubiquitous bright-blue plywood that surrounds the site, making it even more difficult to fathom the amount of work that has been done while the casual observer has paid attention only to the squabbles over the World Trade Center towers.

�It�s a different world behind these�� says Pagliettini, gesturing to the barricades.

Security detail is posted at several passageways separating the foot traffic from the 1,400 construction workers at ground zero and the myriad equipment and materials. The World Trade Center Site envelopes the entire station on all sides, above, and, at least in the case of the No.1 line, an additional 70 ft below. None of the work is typical: it�s never simple excavation, followed by foundation work, followed by steel erection. Construction happens both top-down and bottom-up, east-west and west-east, and almost everything needs temporary support, according to Pagliettini.

In April, for example, crews poured approximately 1,000 cu yds of concrete for the south half of a new crane pad in order to relocate a Manitowac 18,000 crane from One World Trade Center to work on the hub. To install what the crew calls the Calatrava columns�the 15-ton 35-ft tall poured-concrete pieces fabricated in Spain, the team first had to remove parts of the original columns and re-support them with underpinnings. Likewise, to create the passageway under the No. 1 train, crews had to first install 600 mini piles, essentially �hanging the subway,� according to Winsper. �The initial plan was to excavate all the way down, which was a two-step process,� said Winsper. �The team came up with a one-phase approach that would take out an entire phase.�

To further complicate the project, the crew working on the transit hub has to share with everyone else working on the rest of the World Trade Center site, making them essentially landlocked and having to share access to the site with several major contracts.

On the work under the No. 1, that meant simple procedures became incredibly involved.

�Just for the drilling and excavation, we have to excavate it, get it over to a rock dump bed, move it with a crane, transfer it to a truck three-four times�that�s a lot of moving to get that done,� said Jack Frost, executive vice president and CEO of Tutor Perini Civil Group, the contractor on the top-down work underneath the No. 1.

Due to the changing demands of the site, everything, including the entrances to the construction site, changes on an almost daily basis. While leading a site tour to this magazine Pagliettini, who has been on the project for seven years, at least once heads for what he thinks is a door but has now been walled up.

�Nothing here is stable, everything is changing every day�new issues, new problems, new challenges to resolve,� says Winsper. �That stimulates the team overall�it�s not like you can come in and know what you�re doing every day. Some of it is necessity of having four contractors working in a tight space, others are from outside source we have not control over whatsoever.�

�It�s not a fun place to work. It�s a congested site,� Frost agrees. �Fortunately, with good people. My happiest day will be when it�s finished and I move on to something else. We�re going to make sure it�s successful.�