Sumner Tunnel Restoration Project Underway Beneath Boston Harbor
Joe Rigney, PESenior Associate
Originally constructed in the 1930s, the Sumner Tunnel is 31 feet (9.4 m) in diameter and carries traffic for a mile, deep below the Boston Harbor, connecting Boston and East Boston and Logan International Airport. Through routine inspections, the Massachusetts Department of Transportation 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.
As prime, Delve Underground is providing rehabilitation design services to J.F. White on this design-build project. The project scope includes evaluating the tunnel conditions and developing repair procedures and detailed design. The tunnel was built with a full transverse ventilation system with an air supply duct below the roadway and a hung ceiling making up the exhaust duct. The existing ceiling arch is experiencing advanced deterioration. The reconstruction will strengthen and protect the tunnel arch with new precast arches and eliminate much of the existing hung ceiling while improving the efficacy of the existing ventilation system. 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.
To date, the team has submitted a series of Early Release packages to allow for the major reconstruction to be undertaken in manageable phases. This has included:
Developing a temporary and permanent lighting scheme
Detailing wall repairs and fireboard finish
Designing the fire standpipe replacement system
Designing and detailing precast arches for early fabrication
Preparing a ventilation test and evaluation program
Designing and detailing precast ceiling panels
As part of our work, Delve Underground 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” 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.
Construction, by J.F. White, completed to date includes installation of the temporary lighting system, removal of the existing wall panels, removal of abandoned conduits within the tunnel, installation of temporary pumps, protection of drain inlets with silt sacks, filling abandoned air ducts within the box tunnel sections, and concrete wall repairs. Concrete wall repairs will continue over the next couple of months, and the installation of fire boards, the new standpipe, and the permanent lighting system is getting underway this month. Fabrication has also begun on precast concrete arches and the steel brackets supporting them, while shop drawings are well advanced for monitoring equipment and mechanical/electrical components. A full tunnel closure will occur this summer (2023) to facilitate removal of the existing hung ceiling system, installation of the new arches, and repair of the roadway deck.
Once restoration work is completed, the Sumner Tunnel will be in compliance with current design and safety standards.