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The excavation by the tunnel boring machine Mary exposed the technical dimension of a billion-dollar project under the Hampton Roads bay, with expected impact on I-64 and direct connection with the history of American engineering.
The tunnel boring machine Mary completed the excavation of the second and final tunnel of the Hampton Roads Bridge-Tunnel expansion project, in Virginia, United States, by breaking through the final wall on September 24, 2025.
The machine ended a journey of about three miles under the Hampton Roads Harbor, in a project estimated at $3.9 billion and pointed out by the Virginia Department of Transportation as the largest road project in the state’s history.
The completion of the excavation marks the end of the drilling phase but does not represent the immediate opening of the tunnels to traffic.
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After the underground advance, the teams began dismantling Mary and preparing the internal structures, with the installation of the track, ventilation, electrical equipment, and safety systems.
The project schedule foresees substantial completion in February 2027 and final completion in August 2027, according to information gathered by VDOT on its official updates page.
Tunnel Boring Machine Mary was designed to dig under the bay
Mary was built to operate in the Hampton Roads Bridge-Tunnel expansion project, linking I-64 between Norfolk and Hampton.
Assembled, the tunnel boring machine was about 46 feet tall, more than 430 feet long, and weighed over 4,700 tons, a size compatible with the type of excavation planned to cross the bay’s subsoil without trenching the navigation channel.
The equipment arrived in the United States in parts, after being manufactured in Germany and transported by ship.
Once in Virginia, it was reassembled to begin drilling from South Island, one of the artificial islands used in the Hampton Roads Bridge-Tunnel system.
The choice of the tunnel boring machine method allowed progress under the harbor floor while the federal channel remained operational, according to VDOT’s technical explanation of the project.
During the advance, the machine removed soil and installed concrete rings that form the permanent lining of the tunnel.
This procedure is part of the very logic of operation of a tunnel boring machine: excavation occurs along with the assembly of the structure that supports the underground passage.
In Mary’s case, this process was used to open two parallel tunnels under the Hampton Roads Harbor.
The operation began on South Island, in April 2023.
The first journey took the tunnel boring machine to North Island, where the machine needed to be partially dismantled, rotated, and prepared to return in the parallel tunnel.
The first drilling was completed on April 17, 2024, a date recorded by VDOT as the advancement of Virginia’s first excavated road tunnel.
The second stage began after the equipment was repositioned.
The original statement from STV states that Mary began the second excavation in October 2024; however, a VDOT page consulted shows “Oct. 17, 2025,” a date incompatible with the final advancement recorded on September 24, 2025.
Expansion of the Hampton Roads Bridge-Tunnel changes the I-64 corridor
The Hampton Roads Bridge-Tunnel is a connection used on the I-64 between Norfolk and Hampton, a region with road traffic associated with urban commuting, port activity, military bases, and tourist traffic.
The expansion project involves interventions in almost 10 miles of the corridor, with new two-lane tunnels and widening of already existing sections of the highway.
The goal declared by VDOT is to increase the corridor’s capacity and reduce congestion at the crossing.
Instead of replacing the existing tunnels, the project adds two excavated tunnels, which will operate in conjunction with the current infrastructure.
In the land sections, the expansion also alters lanes and accesses connected to the I-64.
The project is not limited to the underground passage.
The program includes bridges, viaducts, artificial islands, access areas, and operational systems necessary for the whole to function as part of a highway.
Therefore, the completion of the drilling represents only one of the stages of the project, even though it is one of the most complex from an engineering perspective.
In the new tunnels, each tube will be approximately 7,900 to 8,000 feet long, according to data released in technical updates and project monitoring.
At its deepest stage, Mary reached about 173 feet below the surface, according to STV, a company involved in quality assurance supervision in the excavated section.
The company also reported that the tunnel boring machine built more than 366 feet of tunnel in a single week, a milestone attributed to the equipment’s performance under the project’s conditions.
As the information appears in the company’s own statement, it should be attributed to STV, responsible for inspection, testing, and documentation activities in the excavated tunnel sections.
Mary Winston Jackson inspires the machine’s name
The name of the tunnel boring machine honors Mary Winston Jackson, a mathematician and aerospace engineer from Hampton, Virginia.
She became NASA’s first black female engineer in 1958, according to the biography published by the American space agency itself.
The name was chosen through a school contest in the Hampton Roads area.
The tribute connects an infrastructure project to a figure from the history of science and engineering in the United States, without altering the technical nature of the project.
In the context of the article, the association helps explain why an industrial machine came to be identified by the name of an engineer linked to NASA.
Mary Jackson worked at the Langley Research Center, a NASA center located in Hampton.
Before reaching the position of engineer, she worked in technical and mathematical areas during a period marked by racial segregation and gender barriers in the United States.
The agency notes that she also worked, throughout her career, on initiatives aimed at the presence of women in scientific and technical roles.
In the Hampton Roads Bridge-Tunnel project, the name Mary came to designate the machine responsible for opening the two new tunnels under the bay.
From this use, the equipment gained public identification in official statements, local reports, and technical updates of the project.
How a tunnel boring machine builds underwater tunnels
A tunnel boring machine of this size combines excavation, material removal, and structural assembly functions.
At the front of the machine, the cutting head advances through the ground.
Behind it, internal systems transport the removed material, while concrete segments are positioned to form the tunnel rings.
This method is different from that used in immersed tunnels, where prefabricated sections are installed in an open trench on the bed of the body of water.
In the case of the Hampton Roads Bridge-Tunnel, VDOT states that the excavated approach avoided disruptions in the federal channel, a relevant point for a region with commercial and military navigation.
STV reported that it monitored inspections, tests, documentation, slurry treatment station, tunnel boring machine operation, and verification of the lining segments.
Harshad Pandit, vice president and director of engineering at the company, stated in the release issued by STV that the milestone represented “years of collaboration, precision, and persistence.”
The quote was retained as it was part of the company’s original material.
Rosmar Gonzalez, responsible for tunnel quality assurance at STV, also attributed the result to the excavation technology and the work of the teams involved.
As this is an assessment made by a representative of the company participating in the project, the statement should be read as an institutional declaration, not as an independent conclusion.
Project enters the phase of internal tunnel systems
With the drilling completed, the teams began dismantling Mary on South Island.
Machine components are cleaned, removed, and prepared for transport, according to VDOT’s description.
This stage occurs before the complete installation of systems that will allow vehicle circulation in the new tunnels.
The next work involves internal paving, ventilation, power, signage, fire safety, drainage, monitoring, and auxiliary structures.
These systems are necessary to transform the excavated space into an operational road within the I-64 corridor.
Mary’s operation also shows a less visible stage of underground works with parallel tunnels.
After completing the first section, the machine did not continue in a continuous line to another project.
It needed to be recovered on North Island, repositioned, and prepared to execute a second pass, with its own alignment and new assembly stages.
When the expansion is delivered, the crossing will have new lanes under the water and in approach sections.
VDOT informs that the purpose of the project is to increase capacity, reduce congestion, and improve the reliability of travel in the corridor.
The measurement of these effects will depend on the system’s operation after delivery and the traffic behavior in the region.
The tunnel boring machine’s mission ended under the bay, but the work continues on the surface and inside the tunnels.
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