The tunnels are part of a 10-mile project corridor spanning both sides of the harbor. Hampton Roads Connector Partners (HRCP)—a design-build joint venture of Dragados USA, Vinci, Dodin Campenon Bernard and Flatiron Constructors—is also overseeing 25 new and reconstructed bridges and highway capacity additions. HDR and Mott MacDonald are the project’s lead designers.

Mary, the tunnel boring machine, arrived on the project’s existing artificial north island and was relaunched back to the south island.
Photo Courtesy Virginia Dept. of Transportation

Appropriately, the “stars” of the multifaceted program have been connected with local history. Mary, the 430-ft-long, 4,700-ton variable density tunnel boring machine tasked with excavating the 45-ft-dia tubes beneath one of the nation’s busiest harbor entrances, honors Mary Winston Jackson, a NASA mathematician and engineer who worked at the nearby Langley Research Center and was depicted in the movie “Hidden Figures.”

Mary’s partner, a 92,500-sq-ft slurry treatment plant, was named for Katherine Johnson, Jackson’s NASA colleague. The plant is designed to receive a flow rate of 14,000 gallons per minute and features one of North America’s largest desanding units.

Mary completed the first tube linking the bridge-tunnel complex’s existing artificial islands in May 2024, breaking through into a specially constructed receiving pit after 13 months of plowing as deep as 100 ft below the riverbed. Following an elaborate turnaround procedure and routine maintenance, the machine was on the move again the following October and is on track to complete mining the second tunnel this summer, VDOT says.

In early May, the tunnel boring machine reached the deepest point of its return route at more than 170 ft below the surface of Hampton Roads harbor.
Photo Courtesy Virginia Dept. of Transportation

Superlatives & Struggles

The significance of managing only the fourth U.S. use of a TBM to excavate a new highway tunnel is not lost on the project team.

“More men have been on the moon then the number of highway tunnels built using this technology,” says Ryan Banas, project director for VDOT’s construction manager, HNTB Corp.

Perhaps as important, adds Banas, is the funding structure that’s making the massive project possible, with more than 90% coming from regional sales and gas taxes provided through the Hampton Roads Transportation Accountability Commission. The agency will use revenue from the completed expansion’s tolled express lanes to fund other infrastructure projects in the region.

The expansion, Banas says, “will open the floodgates to many other projects that will be invested here for generations to come.”

With great size and complexity have also come great challenges. Early last year, VDOT revised its 2019 comprehensive agreement with HRCP, citing what the agency called “unforeseen cost and schedule impacts.” Pushing back the original 2025 completion date by 18 months, VDOT said at the time, would “provide construction schedule certainty, enhance contractor schedule accountability and reduce the potential of litigation,” while also preserving the original budget.

Banas declined to elaborate on reasons for the reset, saying only that given the expansion’s “sheer magnitude, voluminous quantities of materials and complexity,” revising the comprehensive agreement was determined to be in the best interests of all involved.

“The target for substantial completion remains February 2027,” he adds, noting that HRCP has a $90-million incentive to finish by September 2026. “They’re working hard to achieve that bonus.”

A new eight-lane South Trestle bridge is under construction. Temporary bridges aid construction and traffic flow as the old trestle is torn down.
Photo Courtesy Virginia Dept. of Transportation

Digging In

To mine the two new tunnels, HRCP expanded the bridge-tunnel’s two existing artificial islands by several acres using infilled bund rock walls. Mary began her initial journey from a specially constructed 65-ft deep pit on the south island, where the slurry treatment plant is also located.

Moving approximately 50 ft per day, Mary mined approximately 50 ft deeper than the existing tunnels to a layer of highly compressed sand and clay. With each 6.5-ft push forward, the TBM placed a liner ring consisting of nine 6-ft-wide, 12-ton precast concrete segments.

Periodic additions of booster pumps helped keep the slurry system operating at optimal capacity during the 24/7 operation as Mary moved forward, with up to 15 minutes required for excavated material to reach the slurry plant before filtered bentonite slurry is sent back to the TBM.

On the north island, HRCP readied for Mary’s arrival with the construction of a 75-ft deep, 160-ft-dia receiving pit with a 9-ft-thick base slab, heavy enough to resist buoyancy. VDOT says the 31-hour nonstop concrete pour for the slab was the largest continuous pour in agency history, with a fleet of more than 30 trucks making multiple batch plant trips to haul in nearly 5,500 cu yd of concrete.

Following Mary’s May 2024 breakthrough, positioning the TBM for the return trip required a similarly intricate operation that aimed to keep as much of the machine intact as possible. Juan-Miguel Perez, who served as HRCP’s project executive for the expansion’s initial phases, told ENR that “minimizing disassembly would shorten the time needed to deconstruct and reconstruct the TBM, helping us get back to tunneling more quickly.”

With 875- and 750-ton crawler cranes having removed TBM gantries in four pieces, Mary’s 2,500-ton cutter head and shield were turned and aligned for the second tunnel through the use of nitrogen skates, the technology’s first such application in the U.S. and the heaviest shield turn ever, VDOT says. Completed in just 11 hours, the maneuver “was a clean, well-planned operation,” Perez adds.

Mary, the tunnel boring machine, is named for Mary Winston Jackson, a NASA mathematician and engineer who worked at the nearby Langley Research Center and was depicted in the movie “Hidden Figures.”
Photo Courtesy Virginia Dept. of Transportation

Heading Home

Taking advantage of experience gained during excavation of the first tunnel, HRCP has been able to improve efficiency. Mid-April saw the most productive week yet, with the TBM mining 420 ft and placing 63 liner rings. By the time Mary makes her scheduled September arrival back on the south island, the TBM will have placed 2,385 rings totaling approximately 21,600 segments.

The relative smoothness of the tunnel boring phase so far is evidenced by the fact that the only “surprise” has been unearthing remains of a North American mastodon, estimated to be up to 50,000 years old. Currently being used in public presentations about the project, the remains will eventually be donated to Virginia’s natural history museum.

Meanwhile, HRCP continues fitting the first tunnel with ballast, drainage, roadway, lighting, ventilation and safety systems. Back at the surface, new trestles are also nearing completion. Built on 54-in.-dia cylindrical piles driven to depths of 70 to 110 ft, the structures are approximately 12 to 15 ft higher than the original trestles to improve resilience from corrosive storm waves and potential sea level rise. Span lengths range from 60 ft to 125 ft.

This summer, VDOT plans to shift two lanes of traffic on to the new south trestle, which, with 67,568 sq yd of bride deck, will eventually carry all eight lanes between the tunnels and the Norfolk side. To the north, where the alignment required maintaining separate northbound and southbound links to Hampton, HRCP will soon shift traffic on to the new westbound trestle. As the old trestles are demolished, the new structures will continue to direct traffic in and out of the existing tunnels until the new tubes are ready.

Claudio Cimiotti, who took over as HRCP project executive earlier this year, says that achieving these and subsequent milestones on schedule will “require the same focus, care and teamwork” that has brought the project this far, including keeping safety as the top priority.

“One mishap, no matter how small it may seem, can ripple across operations, impact schedules, jeopardize critical milestones and, most importantly, put lives at risk,” Cimiotti says. “We simply cannot afford to let that happen.”