Main stairs into the museum beside the Survivor's Stairway (covered in wood planks).
Tom Stoelker / The Architect's Newspaper
Descending a monumental staircase, visitors will reach the bedrock level that houses permanent, rotating, and age-appropriate exhibits. This space, originally the twin towers’ six-story parking garage, is “a room about the size of Grand Central,” said Steven Davis, a partner at Davis Brody Bond Aedas (DBBA)—bigger than the Whitney or the Guggenheim. It took a single morning for the World Trade Center towers and superblock to become Ground Zero. A decade after the attack, the site has morphed from a projection screen for national dreads, factional controversies, and civic aspirations into a real, tangible place. When completed, it will be part public park, part private sanctuary, part cultural touchstone, part archaeological site, part tourist magnet, and part reinvented commercial center on a restored street grid. Still recognizable, through all its evolutionary stages, is Daniel Libeskind’s original master plan, or at least an iteration of it.
It is not a single vision, but “what survives, through a rather excoriating process,” said Memorial designer Michael Arad of Handel Architects. In interactions with Libeskind, Peter Walker, DBBA, Snøhetta, and others involved on or near the plaza, Arad reports, “the ball bounces back and forth from one to the other, and you pass it, and it changes...in the process it gets enriched with meaning and complexity.”
The first component emerges this fall, when the National September 11 Memorial opens on 9/11/11 for bereaved families, then on 9/12 for the general public. It will be followed a year later by the 9/11 Museum, occupying a seven-story, 98,000-square-foot underground space beneath the waterfalls flowing into the twin towers’ footprints. While the below-grade museum is designed by DBBA, its entry pavilion is by Snøhetta on the plaza. SOM’s Tower One is reaching its 60th floor at this writing, with completion estimated for 2013, followed by Fumihiko Maki’s Tower Four (2013), and the transportation hub (2014); Towers Two by Norman Foster and Three by Richard Rogers are on an indeterminate, market-dependent timetable.
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Rendering of the underground Slurry Wall and the final column removed from the site, now wrapped and installed in the museum (left). Rendering showing aerial view of void pool, Snøhetta's museum building, and two vent structures (right).
Courtesy Squared Design Lab [+]
The original twin towers went from groundbreaking to completion in seven years (1966–1973). The Burj Khalifa arose in six years; the Empire State Building, in 410 days. According to data from the Council on Tall Buildings and Urban Habitat, over the past ten years (including partial data for 2011), China has completed 133 buildings over 200 meters tall.
Do apples-and-oranges comparisons put Lower Manhattan’s pace in context or muddy the waters further? Disputes delaying construction recur in local debates and headlines, but complaints about the timetable have it backward, says Snøhetta principal Craig Dykers. “I always feel that it went too quickly,” he said. “Very few people you’ll find saying that, but I strongly believe this. I think there was too much emphasis on speed,” Dykers said adding, “You cannot compare [the World Trade Center site to] the Empire State Building”—a single-owner project on clearly defined property. To Dykers and others who have come to understand the site’s complexity, the gravity of its demands, and the quality of the work done to date, what’s striking about the Museum/Memorial component is not that it’s taken so long, but that it is achieving so much so fast.
Having worked on Cairo’s Alexandria Library, another emotionally and culturally laden project (lasting 13 years), Dykers finds that Ground Zero’s difficult collaborations have harmonized aspects of the mission that might easily have been discordant. As a memorial, he says, the site looks back toward the Earth, history, the traumas of September 11, and the dead, as it reconnects with the living city. Its “skyscrapers are incised into the sky...pointing upward to the place that we often associate with the future,” he said, and embodying the inherent optimism of commerce. Snøhetta’s three-story Museum Pavilion, the only building on the 8-acre memorial block, draws light deep into the connected Museum atrium by DBBA and creates a transition zone between the city’s energy and the Museum’s solemnity. The low-slung pavilion, whose angled steel panels and mullions introduce a Libeskindian theme of purposeful dissonance, contrasting with what project manager Anne Lewison calls the “corporate signature” of the four towers, includes a private area reserved for the families and a public auditorium. Snøhetta’s original commission—the cultural building housing the Drawing Center and the politically sensitive Freedom Center—fell out of the planning in 2005, but Dykers insists that “there is still a cultural center on the Memorial... an edifice that responds both to the lives of those lost and to the future through culture.”
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Clockwise from left: Construction of the interior wall of the south void pool; a rendering of the "ribbon ramp" and its observation platforms; the ramp under construction.
Rendering courtesy Davis Brody Bond Aedas
On its upper floors and roof, Snøhetta’s building also includes 13,559 square feet of mechanical space, cores, and shafts, out of a total of 59,136 gross interior square feet. Throughout a site that is tightly interwoven in three dimensions—Dykers and Lewison comment that it typifies New York’s tendency to delineate spaces both in plan and in section—such multi-functionality is to be expected. Lewison points out that bearing beams and steel webs both within and beneath the Pavilion strike non-orthogonal angles that are as functional amid the site’s tricky alignments and transfers as its panels and mullion grid are expressive. The Port Authority’s October 2008 report to Governor David Patterson identified a deck-over construction strategy—building the roof of the PATH mezzanine (which doubles as the floor of the Memorial Plaza) before the remainder of the hub—as an operational solution allowing completion of the Plaza in time for the first-decade anniversary. Structural engineer WSP Cantor Seinuk has provided a system of four-foot-thick concrete shear walls, blast walls, and steel-supported concrete slabs below this plaza roof, providing lateral seismic resistance and allowing construction vehicles to serve multiple projects while maintaining uninterrupted PATH service. “The structural gymnastics that went into making this situation work were beyond daunting,” said Davis pointing out a mere wall separating his firm’s space from the PATH mezzanine during a site tour.
The subterranean museum, Davis reports, developed in part through changes in Arad’s initial design, which called for an underground memorial gallery, four ramps per pool, and views through the waterfalls. He is succinct about this change, the subject of a much-publicized clash with Arad: “Because of security concerns, that became untenable.” Another factor, says museum director Alice Greenwald, was Libeskind’s recognition of the metaphoric power of the slurry wall holding back the Hudson, leading to its designation as an historic asset. “We are obligated by federal landmark preservation law to make the slurry wall available to the public to see, which is actually the reason the museum is located below ground,” Greenwald said. The 2006 decision to bring all memorial functions to grade, she says, was a critical milestone, not only halting cost escalation but also consolidating the components and articulating the Memorial/ Museum complex as “its own precinct.”
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Left to right: Photographs of the victims will line this room in the memorial, where the floor of the original structure will be exposed; Rendering of the space beneath the pool with the stairway and "ribbon ramp" in the background; and a rendering of the memorial showing an original column in front of an observation platform (right).
Rendering Courtesy Squared Design Lab [+]
Visitors will follow a coherent path, a Dantesque sequence of descent, contemplation, and ascent (Greenwald calls it “a light-touch experience, not a forced march”). Descending from the Pavilion by stairs or escalator past an iconic pair of the original towers’ 70-foot trident columns, one follows the gently sloping “ribbon” ramp, which doubles back twice to offer broad views of the vast space at west and east overlook points before a break point at the Vesey Street Survivors’ Stairway (relocated and preserved under glass). “We made a very conscious decision for people to arrive at bedrock between the two towers, with no bias for one or another,” says Davis.
Descending the monumental staircase, they reach the bedrock level and the space as large as GrandCentral and bigger than the Whitney and Gugg, Davis said. The exhibition level, where the void pools hover above the original towers’ sheared-off box columns—precisely above them, Davis notes, not a few feet off as in early plans—are aligned with the illuminated square patterns of column stubs to create columns of light in airborne dust. “Everything about this experience,” he notes, “is scale and authenticity.”
The undersides of the pools, Davis adds, will be clad with a unique material, Cymat Alusion foamed aluminum, formed under high pressure with superheated gas and used for strong, light structural bracing in airplane wings. With a surface of myriad reflective facets, the aluminum will resemble a fog when under-lit, becoming “essentially buoyant,” Davis said. “It will dematerialize. It ceases being a solid material...and takes on an eerie, almost apparition-like glow.” Large artifacts already delivered to the Museum include the final column removed at the end of the nine-month recovery period, now preserved against construction-phase dust, debris, and other atmospheric conditions inside an air-conditioned chamber near the west overlook.
The ascent back to plaza level returns the visitor not immediately into urban clamor but to a meditative space defined by Arad’s now-familiar fountains and a grove of some 400 swamp white oak trees in an “abacus bead” alignment: orderly rows when viewed along an east-west axis but naturally randomized when seen from north to south. “There are some unbelievably advanced things going on in this landscape,” Davis says, saluting Walker for the system of pavers, cobblestones, precast concrete tables, soil troughs, and rainwater-capture irrigation. Like so many of the memorial’s abstract elements, the fountain technology is more complex than it looks: fluted weirs by Dan Euser Waterarchitecture guide water flow, and the voids’ massive scale (nearly an acre each, 192 feet on each side, with 176-foot-long waterfalls) makes precise leveling imperative. “If that weir were up an inch anywhere,” says Walker, “the water would run around that inch, and you wouldn’t have the continuous [flow].” Tested last November, it worked on the first try, Davis reports, and it will continue working thanks to a threaded adjustment system to allow for differential settlement over time.
Clockwise from left: View underneath the north void pool whose surfaces will be covered in aluminum foam; exposed detail from the original World Trade Center; a row of shaved bases of columns that supported one of the towers; the slurry wall which was designated an historic asset; a detail of one of the original column bases in the subterranean museum and memorial.
[+ Click to enlarge.]
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Walker credits forester Paul Cowie and transplant/transport specialist Tom Cox for helping resolve the “huge technical issues of trying to grow trees on top of a seven-story building of this size.” New York street trees are stressed enough by particulates, noise, radiation, and disease to live an average of only seven years, he says, but these oaks are expected to live for 80 to 100. After a year of forestry research, the species quercus bicolor was chosen, one of only six or seven deemed hardy enough for these conditions. The trees represent the five states where most 9/11 victims resided and have spent the past several years in a New Jersey nursery with a climate similar to Manhattan’s, fed and tended with a precision that makes them, in Walker’s words, “virtually identical, all straight leaders, all virtually the same tree.” He adds, “I’ve never had a chance to do this over time” in the U.S. This is his first American project as sophisticated as those of Swiss and German nurseries.
One component that may surprise visitors is a pair of concrete monoliths along the site’s West Street border, where original plans called for a one- or two-story museum entrance pavilion (removed in 2006 when public functions were brought up to grade and the museum and plaza entrances were consolidated on the east). Currently, the two structures are an unavoidable utilitarian eruption into the plan: vents. Among feasible airflow options for the site’s subgrade spaces—the museum, train stations, chiller plants, extensions of commercial spaces, and others—the West Street structures are far less intrusive, Walker explains, than what engineers initially saw as necessary: numerous smaller vents scattered around the memorial plaza. “I think there were 17 or 18 of them... frankly, I couldn’t see how you could build a memorial with all these vents. Because of the security, these vents had to be pretty tall, as much as 20 feet off the ground. So they were formidable. Our task in the Memorial was to produce this flat plane from which the voids fall down 30 feet....You just can’t do that with all this other stuff around. You have to produce a plane with which you can cut these voids if they’re going to be powerful. So we did a model, which we later called the Awful Model, where we had all the vents and colored them bright orange, and we took them to the Governor.” The reaction by Pataki’s chief of staff John Cahill was, “That looks awful.” He ordered the engineers to remove them all. The two West Street volumes and a few flat grates “essentially have collected all the vents that absolutely have to come up,” Walker notes. “It solved the security problems and also grouped all the vents together, which took a lot of engineering.”
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Clockwise from top: Two vent buildings flank the grove of oak trees above the underground museum; the southern pool under construction; the granite-paved plaza with museum entrance in the background.
[+ Click to enlarge.]
Few preliminary renderings emphasize the vents, and tree growth will make them less conspicuous over time, but they suggest how the site has evolved to keep its aesthetics and its emotional weight in counterpoise with its practicalities. It is developing within an atmosphere of relentless scrutiny, likely to re-intensify as each component opens, no matter how “Ground Zeroed out” some New Yorkers have grown over the long decade. “Part of the obligation of memory as human beings,” said Greenwald, “is that this is not somebody else’s tragedy; this is our tragedy. It belongs to all of us”—even someday to those who will have no personal memory of Sept. 11, those who may visit once in a lifetime in search of a history lesson, and those who drop by daily from a nearby office seeking a shady place to eat lunch.
If the site’s mission inspires awe, its execution evokes humility. “The awe wears off,” admitted Arad, and control is impossible on any level, from building placement on the site to the fine details of translating the two-dimensional Optima Nova font into the three-dimensional lettering of names on the fountain parapets. “It’s all about letting the site speak for itself,” he said, “not trying to come in here and impose a clear and reductive narrative,” his own included. “I don’t think you can force understanding or an epiphany on anyone, but you can create that space that allows people to have their own epiphanies.” After a decade of contention among parties trying to impose their stories on the Memorial, what the public will ultimately perceive and use is not time, political process, or even values, but the dialogues of expertise that generate a spatial performance.