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Tunnel boring
The journey has come to an end for Mary, the Tunnel Boring Machine (TBM). On Sept. 24, 2025, the TBM’s excavation culminated in the final breakthrough at the South Island in Norfolk, Virginia. Since launching from the South Island in April 2023, Mary has bored beneath the Chesapeake Bay to create twin tunnels for HRBT Expansion Project. Approximately 50 feet below the existing tunnels, the two new tunnels will serve eastbound travel lanes when the project is completed.
The process spanned more than two years. Mary achieved her first milestone on April 17, 2024, when she broke through on the North Island, completing the first bored tunnel in Virginia history. Crews were able to turn the 4700-ton machine around in six months before she began her second trip on Oct. 17, 2025.
Built specifically for the HRBT Expansion Project, Mary installed the tunnel rings as she excavated the soil. Unlike the existing immersed-tube tunnels in Hampton Roads, the bored-tunnel approach eliminated disruptions to the busy federal channel.
With tunneling complete, crews are now disassembling Mary on the South Island. Components of the massive machine are being cleaned, removed, and prepared for transport.
Second tunnel completed!
On Wednesday, Sept. 24, at 12:30 p.m., Mary made her final breakthrough for the HRBT Expansion Project concluding the tunneling part of the project.
Learn how tunnel boring works
Learn how the new HRBT twin tunnels came to life through careful planning and design. Explore the complex engineering and construction process that made this massive project possible.
First tunnel completed!
The TBM completed its first tunnel from Norfolk to Hampton. The TBM is being repositioned for the boring of the second parallel tunnel back to the South Island.
TBM Naming Contest
The HRBT Expansion Project held the Tunnel Boring Machine (TBM) Naming Contest in the fall of 2020. The contest was open to middle school students in Hampton Roads.
TBM Factory Acceptance Test
The HRBT Expansion Project reached another milestone as the Tunnel Boring Machine (TBM), named “Mary the TBM,” achieved completion of the Factory Acceptance Test (FAT).
The FAT process was rigorous, taking place over several weeks as engineers from the design-build team, Hampton Roads Connector Partners (HRCP), examined and tested every component of “Mary,” to demonstrate that all systems function as designed and to address any adjustments needed while the machine is still at the factory. “Mary” was designed and built by Herrenknecht in Germany. The FAT was the final stage of the manufacturing process.“Mary” was then prepared for her journey home, arriving December 2021 in the United States.
Last updated: December 8, 2025
