The Hampton Roads Bridge-Tunnel (HRBT) represents a vital transport link between Norfolk and Hampton in Virginia, serving as a significant artery for motorists since its inception in 1957. This structure spans 3.5 miles beneath the bustling Hampton Roads channel in the Chesapeake Bay, facilitating a staggering monthly traffic volume of over three million vehicles. Unfortunately, this heavy load has led to notorious congestion, prompting local officials to launch a substantial expansion project worth over $3 billion to alleviate the ongoing traffic woes.
After years of extensive planning and public engagement, a significant milestone was achieved on September 24, 2025, when Mary, an enormous tunnel-boring machine (TBM), broke through to the other side of her first tunnel. The excitement was palpable as community members, reporters, and dignitaries gathered at the exit point on Hampton’s South Island to witness this historic event. Mary, with her monumental 46-foot cutting wheel, managed to tunnel through rock at a rate of about 50 feet a day. U.S. Transportation Secretary Sean Duffy lauded the community’s perseverance and collaborative spirit in seeing this multi-year project come to fruition.
A titanic feat of engineering named Mary
Tunnel-boring machines have a storied history, tracing their origins back to the Wilson Patent Stone Cutting Machine of 1851. Over the years, these machines have evolved dramatically. The modern design was revolutionized by James Robbins in 1952, introducing a rotating cutter head surrounded by a shielded excavation chamber. This design focused on worker safety and efficiency, allowing for effective removal of excavated materials and reinforcement of tunnel walls. Today’s tunnel-boring machines are vast engineering marvels compared to their predecessors, with advancements informed by both historical practices and technological innovations.
Mary stands as a testament to these advancements. Unlike the single-lane “Cybertunnels” proposed by one of Elon Musk’s companies, Mary boasts a cutter head measuring 46 feet in diameter—akin to the height of a four-story building. Extending longer than a football field, this impressive machine’s assembly and transport alone cost a staggering $70 million, not factoring in the labor and energy expenses associated with operating such a remarkable yet fuel-intensive piece of machinery.
As Mary works its way through the rock layer 50 feet below the existing HRBT tunnel system, crews are diligently reinforcing the tunnel walls with concrete bracing. Though the progress has been methodical, it is carefully planned. Optimistically, the new tunnel is set to double the vehicle capacity of the HRBT, significantly easing the traffic frustrations that have plagued the region for decades. For the weary commuters of Hampton Roads, this effort represents a long-awaited beacon of hope and relief.