Sumner Tunnel Reconstruction – A Unique & Innovative Project

The Sumner Tunnel Reconstruction Project in Boston, Massachusetts, is a remarkable initiative that showcases the innovative use of precast concrete and rapid smoke testing to address one of MassDOT’s most complex challenges: rehabilitating a deteriorating road tunnel. Originally constructed in the 1930s, the 31-foot-diameter Sumner Tunnel spans 1.08 miles and carries 40,000 vehicles per day deep below Boston Harbor. Over the years, the tunnel’s arch and ceilings have deteriorated, reaching the end of their useful life.

Project Overview

The project involves a full tunnel renovation, including structural arch and walls, invert superstructure and pavement, ceiling and ventilation operating system, lighting, standpipe, and all operating systems. The commitment to complete the project within a single 3-month shutdown period while maintaining existing tunnel operations at all times is a testament to the project’s complexity and uniqueness.

Innovations & Uniqueness

One of the key innovations in this project is the use of a full-span precast arch, which combines tunnel and precast bridge design concepts into a never-before-utilized application. This approach not only enhances durability and fire resiliency but also reduces overall delivery and installation time. The project team conducted a trial program to prove the concept, which convinced MassDOT of its feasibility.

The ventilation system was also optimized with a quarter duct and East Boston damper, validated through innovative testing. This new system improves airflow during fire events and establishes new operating modes that enhance safety.

Social & Sustainable Impacts

A number of social and sustainability benefits were achieved on this project. Components were fabricated off site, which minimized the impact to the community by reducing the space that would have been needed for a casting and curing yard.
The extent of hung ceiling was reduced by 75 percent, reducing the overall delivery and installation time, and the overall closure time. Additionally, the use of sustainable materials, such as steel fibers and polypropylene fibers in concrete, increases fire resistance and durability while reducing the need for fireboard across the tunnel crown. This kept project costs down and made it more sustainable both in the short term and long term, with fewer repairs needed in the future. The elimination of overhead fireboards results in less of a safety risk to the traveling public, as fireboards can become waterlogged and impose more direct tension under gravity loads on the small anchors that support them. Even the new LED lighting system provides a benefit by reducing the tunnel’s operating costs.

Fulfillment of Owner Needs & Future Value The Sumner Tunnel Reconstruction Project extends the structure’s design life by over 50 years while also reducing operational costs and enhancing life safety for travelers. Completed ahead of schedule, the project demonstrates that similar tunnel repairs can be achieved within a short closure period. Its successful delivery has earned praise from MassDOT officials, and it was recently awarded a Gold Engineering Excellence Award by the American Council of Engineering Companies of Massachusetts. 

“We are thrilled that we have been able to deliver this project ahead of schedule.” State Highway Administrator – Jonathan Gulliver

“The Sumner Tunnel Restoration Project was a hugely important effort that ensures this vital piece of infrastructure is in the best possible condition going forward.” MassDOT Secretary – Monica Tibbits-Nutt