Fort Miller Precast engineered and delivered a durable precast flood wall system on Governors Island, protecting critical infrastructure from coastal flooding and erosion.

Project Details

• Owner: Triborough Bridge & Tunnel Authority
• Contractor: Judlau Contracting
• Erector / Installer: Northeast Structural Steel
• Project Completion: 2019
• Scope: 61 Precast Concrete Flood Wall Panels

Project Overview

Governors Island, located just south of Manhattan in New York Harbor, is home to an octagonal ventilation building for the Hugh L. Carey (Brooklyn-Battery) Tunnel. This critical structure contains dozens of high-capacity fans that purge vehicle exhaust and completely refresh the tunnel’s air every 90 seconds, making it a vital part of New York’s transportation infrastructure. 

Protecting the ventilation building from coastal flooding and erosion is paramount, as its continuous operation is vital to tunnel safety. In October 2012, Superstorm Sandy underscored this vulnerability: A massive storm surge flooded thousands of feet of the tunnel tubes, causing extensive damage to the tunnel’s mechanical and electrical systems. In response, the Metropolitan Transportation Authority (MTA) launched resiliency upgrades, including a precast flood wall system around the Governors Island vent building. 

This barrier provides long-term protection against storm surge, sea level rise, and shoreline erosion, ensuring the tunnel’s ventilation system remains fully operational during extreme weather events.

Scope and Details

To protect the Governors Island Ventilation Building from coastal flooding and long-term shoreline erosion, Fort Miller Precast was selected to manufacture a durable, custom precast flood wall solution. Leveraging the benefits of off-site manufacturing, Fort Miller fabricated all wall components in a controlled environment, ensuring precision, consistency, and structural integrity. 

Fort Miller Precast manufactured a total of 61 precast concrete flood wall panels for this project. The panels featured a haunched top profile to help deflect wave action, enhancing their performance as a flood barrier for erosion protection.

All panels were fabricated off-site at Fort Miller’s facility in upstate New York under strict quality control measures and free from weather interruptions or on-site constraints. Once cured, the massive panels were shipped by truck to a New Jersey staging yard, then loaded onto barges for final delivery to Governors Island. 

This logistics plan was crucial given the island’s limited accessibility. Delivering precast components by barge and just-in-time for installation eliminated the need for large material stockpiles or formwork yards on the island. Off-site prefabrication greatly minimized on-site construction activities, a major benefit in a tight, hard-to-reach jobsite. The precast approach reduced disruption to the island’s nearby public park spaces and kept the job efficient despite the remote location.

After the island’s perimeter was prepared with a new reinforced concrete foundation ring, installation of the precast wall was completed using heavy lift equipment. A floating crane hoisted each 19-ton panel and set it into place around the octagonal building’s base. Fort Miller also cast corrugated sleeve inserts in the bottom of each panel during fabrication. During erection, these sleeves fit over anchor rods embedded in the new foundation, allowing for fast and precise alignment. Adjacent panels were then bolted together to form a continuous structural ring. Grouting and sealing of the joints completed the barrier, making it effectively watertight up to the design flood elevation. 

For aesthetics, an architectural stone-textured formliner was used on the outward face of each panel, helping the new flood wall complement the historic granite façade of the vent building. Notably, two of the precast units included integrated doorway openings, providing access points through the wall while maintaining flood protection. The concrete mix utilized white cement and exposed aggregate accents on panel joints, giving the appearance of dimensional stone banding to blend with the original structure. In effect, the installed system is both a functional flood barrier and an architecturally sensitive flood wall structure.

Despite the massive size of the panels, the coordinated off-site manufacturing and on-site erection meant the flood wall was installed quickly and with a high degree of fit and finish. By late 2019, the 61-panel precast wall was fully in place around the ventilation building, marking completion of this scope of the flood mitigation program.

Impact and Innovation

This project demonstrates an innovative application of precast flood wall technology for coastal flood protection. 

The new flood wall building serves as a resilient shield, safeguarding this critical infrastructure from future storms. In the event of a hurricane or extreme high tide, the precast flood wall is designed to absorb and block storm surge, preventing floodwaters from reaching the ventilation plant and ensuring the Hugh L. Carey Tunnel remains operable during severe weather. By controlling wave impact and limiting coastal erosion around the building’s perimeter, the wall helps preserve the stability of both the structure and the island shoreline. 

Equally important is the innovative construction approach using off-site precast fabrication for a difficult location. Fort Miller’s ability to deliver high-precision precast of this size by barge enabled the project team to fortify a remote site that would have been challenging for traditional cast-in-place construction. 

Moreover, the precast installation was faster than an equivalent poured-in-place wall, helping the design-build team accelerate the schedule and complete the flood mitigation upgrades sooner. 

The project delivered a durable, innovative precast flood wall system that provides long-term erosion protection and flood defense, all while meeting the high standards of design expected by the engineering community and general public.

All installation photos are courtesy of Northeast Structural Steel.