Opportunity
In 1940, President Franklin D. Roosevelt broke ground for the construction of a tunnel linking the southern tip of Manhattan with the Red Hook neighborhood of Brooklyn. Ten years later, after a three-year hiatus caused by World War II, the 9,117-foot (2.8-kilometer) twin-tube tunnel was completed.
In The Power Broker, his classic biography of developer Robert Moses, Robert A. Caro wrote, “No underwater vehicular tunnel in the Western Hemisphere — and only one underwater vehicular tunnel anywhere in the world — would be as long as the Brooklyn–Battery Tunnel.”
More than 60 years after its completion, it remains the longest underwater vehicular tunnel in North America.
In October 2012, the storm surge from Superstorm Sandy completely flooded 6,000 feet (1.8 kilometers) of each tube with seawater, damaging mechanical, lighting, and ventilation systems. One of the tubes reopened after 16 days, but the other required weeks of rehabilitation.
Solution
Before the storm, Mott MacDonald was retained by the Triborough Bridge and Tunnel Authority to help meet several key objectives for the tunnel:
- Eliminate groundwater infiltration through the existing base slab
- Rehabilitate the Manhattan Exit Plaza
- Meet all safety and operational requirements for a high-traffic-volume highway tunnel
- Implement maintenance and protection of traffic to minimize impacts on the traveling public
Following Superstorm Sandy, the Authority asked us to expand its scope of work to include the design for the replacement of the following:
- Ceiling system in both tubes, including evaluation of fire hardening
- Wall finishes in both tubes, including evaluation of fire hardening
- Roadway lighting and control systems
- Exhaust and intake duct and cross-passage lighting systems
- Traffic control, monitoring, and communications
- Systems in ventilation buildings
- Elevator in Governors Island Ventilation Building
The scope of work also included the following:
- Condition assessment of roadway concrete ceiling slab
- Repair or replacement of elements damaged during flooding, including cathodic protection system, and low-tension clay-tile duct banks.
- Repair or replacement of fresh air flues, exhaust ducts, and damper plates
- Replacement and capacity upgrades to the Governors Island Ventilation Building and Manhattan Blower Building pump stations
- Evaluation and design of repair or replacement of fire protection elements
Outcome
The damage to the tunnel caused by floodwaters contaminated by salts and oils presented an engineering challenge. Mott MacDonald performed a Storm Damage Assessment Report for the Triborough Bridge and Tunnel Authority to submit to FEMA, while concurrently designing multiple tunnel systems on an accelerated design schedule.
With our help, the Authority is helping to provide a resilient tunnel structure that will help protect against future flooding, fire, and terrorist threats. Emergency evacuation systems have been added to the tunnel with wayfinding lighting not previously used in North America. Tunnel systems also include energy-saving LED lights.
The Brooklyn–Battery Tunnel will be returned to a State of Good Repair that will leave it more robust and better prepared to withstand extreme weather and other severe impacts.