Boston, MA

Sumner Tunnel Restoration Project

Massachusetts Department of Transportation (MassDOT)


Originally constructed in the 1930s, the 1‑mile-long (1.6 km) Sumner Tunnel is 31 feet (9.4 m) in diameter and carries traffic deep below Boston Harbor, connecting Boston and East Boston. This project includes both design and construction of the rehabilitation of the Sumner Tunnel. 

Through routine inspections, the Massachusetts Department of Transportation (MassDOT) identified structural and safety issues that required a full restoration including repairs and improvements to the walls, deck, and ceiling inside the nearly 100-year-old tunnel. Once restoration work is completed, the Sumner Tunnel will be in compliance with current design and safety standards.

Fast Facts
  • Rehabilitation of a 1-mile-long (1.6 km) highway tunnel
  • Repair of heavily deteriorated crown
  • Upgrading the life safety systems to meet current code requirements
  • Ventilation system improvements

Scope of Work

As prime, Delve Underground is providing rehabilitation design services on this design-build project. The project scope includes evaluating the tunnel conditions, developing repair procedures, and detailed design. The existing ceiling arch, which is experiencing advanced deterioration, will be strengthened and protected with new precast arches. 

The tunnel ventilation system was studied theoretically and through live testing, and it was determined that 75% of the existing hung ceiling could be permanently removed. This would not only result in a reduction of potentially hazardous overhead conditions and a decrease in maintenance needs, but would actually improve the ventilation system performance. 

New LED lighting will be installed to provide better visibility and energy savings, a new fire standpipe system will be provided, the roadway deck will be strengthened and better protected, and the tunnel ceilings and walls will be made more fire resistant.

Challenges & Innovations

The precast arches allow for accelerated construction methods and provide structural strengthening benefits, fire resiliency, improved water infiltration resistance, and protection against contaminants in the tunnel environment. Delve Underground also performed a tunnel ventilation smoke test using the Delve Stacey Agnew test bus to simulate the conditions of a fire in the tunnel and test existing ventilation system performance. 

The “smoking bus” test provides assurance that highway and rail tunnel ventilation systems are working properly and will move smoke as they are required/intended to in the event of an emergency.