Port Authority installations turn an employee emblem into a 13-ft sculpture and Daniel Libeskind’s ‘Wedge of Light’ into an Oculus floor inlay
Twenty-five years after the Sept. 11 attacks, two additions to the World Trade Center campus are giving permanent form to symbols and ideas that emerged from the destruction and rebuilding of the site.
A 13-ft-tall memorial unveiled Sept. 8 in Liberty Park transforms an image worn on Port Authority of New York and New Jersey workers’ hard hats during reconstruction into a three-dimensional monument. A second installation, announced Sept. 9, sets into the Oculus floor, the centerpiece of the $4-billion World Trade Center Transportation Hub, the path of sunlight that helped shape Daniel Libeskind’s original master plan for rebuilding the 16-acre site.
From Hard Hat to Memorial
The memorial’s circular granite base recreates part of a 1995 Port Authority memorial to employees killed in the 1993 World Trade Center bombing that was destroyed on Sept. 11.
Image courtesy HNTB
The Port Authority Employee Memorial, near St. Nicholas Greek Orthodox Church and overlooking the World Trade Center memorial pools, honors the 84 agency employees killed on Sept. 11, 2001, and six killed in the February 1993 World Trade Center bombing. The Port Authority said it also recognizes those sickened or killed by illnesses linked to post-9/11 recovery work.
The nonprofit World Trade Center Memorial Fund commissioned and installed the sculpture in collaboration with the Port Authority. Its design is based on a perspective image of the Twin Towers that became a symbol of remembrance and recovery among agency workers, appearing on hard hats, patches and flags after the attacks.
HNTB served as architect and engineer of record. Project lead Thomas Grassi said the central challenge was translating the image’s forced-perspective, two-dimensional aerial view into a structure recognizable from below but also able to “stand alone architecturally and meaningfully” for visitors unfamiliar with the original symbol. The team tested the geometry with digital and 3D-printed models.
The towers are fabricated from stainless steel, supported by welded 316L stainless steel plates in a box configuration. The 2,300-lb stainless-steel segment is attached to granite elements with grouted anchors, bringing the entire memorial to about 25,000 lb. It rests on a 9-in.-thick concrete pad over compacted dense-graded aggregate and existing geofoam. Kearny Sheet Metal Works fabricated the stainless steel and Burns Bros. & McCabe Inc. fabricated the stone.
“When standing at the location of the memorial, a person feels like they are on the ground, but this location is actually the roof of a vehicular facility,” Grassi said.
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HNTB studied the framing, capacity and waterproofing of the World Trade Center’s below-grade vehicle security facility before determining the memorial could be placed there. The team also evaluated multiple crane setup locations so erection could occur during a limited overnight construction window, minimizing impacts to nearby streets and an adjacent hotel.
The granite also links the new memorial to one that stood at the original World Trade Center. It came from the same quarry that supplied stone for a Port Authority memorial unveiled in 1995 for those killed in the 1993 bombing. That memorial was destroyed on Sept. 11. The new structure recreates its circular, red-inscribed ring. According to Grassi, it is the first memorial to bring Port Authority employees killed in both attacks together at one location.
Grassi spent 30 years at the Port Authority and was working on the 82nd floor of One World Trade Center when the first plane struck Sept. 11. He spent the next 15 years working on recovery and reconstruction, wearing the Twin Towers symbol on his hard hat throughout that work.
ENR Archive Rebuilding the World Trade Center Two Decades of ENR Reporting
ENR followed the design, engineering and construction that reshaped the World Trade Center site.
2003 Libeskind’s Proposed Trade Center Scheme Wins The Wedge of Light enters the rebuilding plan. 2004 Design of World Trade Center Transportation Hub Unveiled Sept. 11 sunlight is designed into the hub. 2006 A Conversation With Calatrava Calatrava envisions a “living memorial.” 2006 Team for WTC ‘Bird of Peace’ Tries to Remain Unflappable The hub shifts to incorporate the Wedge of Light. 2011 At New York’s New World Trade Center, Uncommon Cooperation Inside construction across the 16-acre site. 2016 World Trade Center Train Station Opens With $4-Billion Price Tag The Oculus opens after years of redesign. 2020 World Trade Center Downtown Restoration Program, Phases I & II ENR looks back at the $20-billion rebuilding program. 2023 New York Project of the Year: Saint Nicholas Greek Orthodox Church Building a new landmark of remembrance at Liberty Park. Explore More ENR 9/11 Coverage →
A Design Drawn in Sunlight
Inside the Oculus, the Port Authority has installed permanent floor markings aligned with Libeskind’s “Wedge of Light” concept.
A glass-and-Lasa-marble centerpiece and inscriptions extending across the Oculus trace, according to the Port Authority, the sun’s axis and angle between 8:46 a.m., when American Airlines Flight 11 struck the North Tower, and 10:28 a.m., when the tower collapsed.
New floor markings in the Oculus trace the sun’s angle and path associated with Daniel Libeskind’s “Wedge of Light” concept for the rebuilt World Trade Center site.
Image courtesy PANYNJ
One inscription records the sun at an azimuth of 128.45° and an altitude of 41.33° at 10:28 a.m. Anti-slip glass covers the marble medallion.
When Libeskind’s “Memory Foundations” concept was selected in February 2003, ENR reported that the plan included a “Wedge of Light,” then envisioned as a piazza around an intersection within the World Trade Center site.
When Santiago Calatrava unveiled his conceptual hub design in 2004, ENR reported that its retractable roof was intended to admit daylight into the structure, including sunbeams corresponding to Sept. 11, 2001.
By 2006, ENR reported that Calatrava wanted to shift the transit hall to incorporate part of Libeskind’s Wedge of Light plaza, a change that ultimately won agreement from Libeskind, the Port Authority and government officials.
Calatrava told ENR that year that he saw the transportation hub as potentially becoming a “living memorial,” a place where people would arrive at the World Trade Center through light and activity. The hub was positioned within the landscaped Wedge of Light plaza, with the building angled along its southern edge.
That emphasis on light extended to an operable roof designed to open annually on Sept. 11, allowing natural light and a slice of sky into the building. The Oculus, which opened in 2016, instead had fixed wings after a redesign.
The new walk-over medallion marks the 10:28 a.m. position with an inscription: “HERE THE SUN STANDS AT 10:28 AM ON SEPTEMBER 11, COMPLETING A WEDGE OF LIGHT.”
