Revamping the Brooklyn-Battery Tunnel

Completed in 1950, the Brooklyn-Battery Tunnel (now the Hough L. Carey Tunnel), connects the southern tip of Manhattan with the Red Hook neighborhood of Brooklyn. This 9,117-foot (2.8-km) twin-tube tunnel carries over 50,00 vehicles per day. 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 km) of each of its twin tubes with seawater, damaging mechanical, lighting, electrical, communications, traffic controls, and ventilation systems. One of the tubes reopened after 16 days, but the other required weeks of rehabilitation.  

Comprehensive rehabilitation and system upgrades

Before the storm, Mott MacDonald was retained by the Triborough Bridge and Tunnel Authority to help meet several key state of good repair objectives for the tunnel. These included eliminating groundwater infiltration through the existing base slab, rehabilitating the Manhattan Exit Plaza, meeting all safety and operational requirements for a high-traffic-volume highway tunnel, and implementing 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 and wall finishes in both tubes, including evaluation of fire hardening
• Low-voltage and extra-low-voltage duct bank and raceway design within the tunnel
• LED tunnel roadway lighting and control systems, as well as wayfinding and door lighting systems
• Exhaust and intake duct and cross-passage lighting systems
• Exhaust plenum mass notification system
• Replacement of low-voltage distribution for lighting, pumping, and control systems within the four facility buildings
• Traffic control, monitoring, and communications
• 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  

The damage to the tunnel caused by floodwaters contaminated by salts and oils presented an engineering challenge. We performed a Storm Damage Assessment Report for the Authority to submit to FEMA, while concurrently designing multiple tunnel systems on an accelerated design schedule.  

A resilient tunnel for the future

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.

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.