In 2009, the United Nations Educational, Scientific and Cultural Organization decided there should be a permanent memorial established on the United Nations (UN) visitor’s grounds to honor the victims of slavery and the Trans-Atlantic Slave Trade. Named the Ark of Return, this was to be the first permanent memorial of any kind at the UN’s headquarters, which is located in New York City. The memorial was designed by Rodney Leon, an American architect of Haitian descent, and is the result of an international competition that attracted over 300 entries from 83 countries.

“The permanent memorial at the UN honors the memories of the estimated 15 million men, women and children who were victims of the largest forced migration in history,” said Jonathan Tibett, proprietor for ABC Stone in Brooklyn, NY. “Rodney was aware that ABC played an important role in other large-scale monumental installations, such as Antonio Pio Saracino’s Hero and Superhero in Bryant Park, and knew we had the experience to facilitate a project of this magnitude. It was a real honor to be chosen by Rodney to assist him in realizing his monument.”

The project was contracted by Precision Stone Inc,  supplied by ABC Stone Inc and fabricated by Union Marble and Granite. Olympic White Danby marble was chosen for elevations and Mountain White and Crystal Stratus Danby marble was employed for the floor. The marble was all quarried by Vermont Quarries of Mendon, VT. The slabs spanned 128 x 78 inches with thicknesses ranging from 2 to 9 inches. Additionally, Zimbabwe Absolute Black cubes were airfreighted for the elements necessary for the Trinity Sculpture. In total, the project used 550 cubic feet of stone.

“In addition to the scale, it was also technically complex as it contains a statue of an African man at its center and houses a waterfall which represents the tears of the men, women and children who were forced to make this horrific journey across the Atlantic into slavery,” said Tibett. “My team had an incredible desire to provide something strong and powerful and send the message to future generations so that such a terrible injustice will never become part of our reality again.”

Picco Engineering, located in Concord, Ontario, Canada, was selected as the engineering consultant of the UN’s Memorial. “Engineering consulting for the Ark of Return involved analysis and recommendations specific to the structural requirements for stone bearing support and attachment,” said Michael Salerno, the business development manager for Picco Engineering. “The complex shape of the Ark required an innovative and non-traditional approach to stone engineering.” Picco Engineering relied on Building Information Modeling (BIM) visualization tools, significant collaboration and geometry analysis to understand and conceptualize efficient stone installation. The stone panels were large and varied in shape, so special attention for lifting the stone and positioning the anchors was considered.”

One of the biggest challenges during the process for Picco Engineering was coordinating and designing the steel frame with the engineering of the stone and stone anchoring. “The coordination of the structural steel frame was done in collaboration with Milgo-Bufkin, the steel fabricator,” said Salerno. “The geometry of the stone panels was such that the steel framing members behind the stone required precise alignment with stone jointly. Both welded and screwed connection plates were to align with stone joints and steel framing tubes precisely. The biggest challenges with the stone were the large sizing in relation to the stone properties, and the non-rectangular shape and positioning of the marble slabs. Our start to finish deliverable schedule for structural design, engineering of stone, all detailing, stone fabrication and installation was 45 days. This would ensure that the high-profile unveiling went off without a hitch. We are happy to say that it did exactly that.”

To fabricate all the stone, ABC Stone used a 5-axis CNC machine from Prussiani of Italy; a 3-axis bridge saw from GMM of Gravellona Toce, Italy; and a waterjet from Flow International of Kent, WA.

Coordination was a critical part of this project for ABC Stone. “Working out the coordination of the steel and stone was a huge task,” said Tibett. “We used Catia software to develop the model, which allowed us to identify all aspects of the structure and their interaction with the finished stonework. We were able to incorporate all of our anchoring connections, lighting and plumbing connections as well. The monument has an extensive lighting and fountain component that needed to fit into a minimal cavity. As the onlooker walks up to the Trinity Sculpture, a sensor triggers a pump which pushes water through a 2-mm tube in the corner of the Trinity’s eye that gives the impression of crying. This water is then captured in a hidden drain in the memorial hood of the sculpture which recycles through the fountains. The fabrication of all of the pieces was extremely challenging, as only two pieces in the entire structure were cut square.”

In addition to the use of BIM software to help successfully execute the Ark of Return project, various software programs were used in combination by the project team, including Catia, Inventor, Autocad and Revit. “BIM allowed all stakeholders to seamlessly coordinate their independent design efforts into one cohesive and comprehensive 3D parametric model,” said Salerno. “The model was the fundamental deliverable that was used to export and generate all fabricated materials, including the steel frame, stone panels and stainless steel connections. BIM allowed the team to view the complex shape easily and manipulate sections and elevations for streamlined solving of design challenges. It proved to be an efficient conduit for team reviews through GOTO meetings and approvals; while robustly helping to identify clashes and discrepancies.”

Since its completion in March of 2015, the Ark of Return memorial has received high-level accolades from visiting dignitaries and members of the UN.  


Ark of Return

United Nations

New York, NY

Owner: United Nations

Stone Supplier: ABC Stone, Brooklyn, NY

Contractor: Precision Stone Inc., Westbury, NY

Stone Fabricator: Union Marble and Granite, Westbury, NY

Stone Quarrier: Vermont Quarries, Mendon, VT (White marble)