TL:DR Non-Paywalled The 430-ft-long, 4,700-ton variable density tunnel boring machine began its round trip beneath the harbor in April 2023, completing the first tube just under one year later.

According to the Virginia Dept. of Transportation, the TBM moved a total of more than 1 million cu yd of highly compressed sand and clay on a 3-mile round-trip route that extended more than 100 ft below the riverbed, and up to 173 ft below the mean surface level. The agency said the machine set a world productivity record for its TBM class/size, boring 366 ft in a single week.

Along the way, the TBM installed nearly 2,400 tunnel rings composed of approximately 21,600 precast segments.

The 430-ft-long, 4,700-ton variable density tunnel boring machine began its round trip beneath the harbor in April 2023, completing the first tube just under a year later. Following an intricate turn-around process using nitrogen table technology, and undergoing routine maintenance, it began boring the second tunnel last October.

Paralleling a pair of existing two-lane tunnels, opened in 1957 and 1976, the new tubes are part of the Virginia DOT’s largest-ever highway construction project. Hampton Roads Connector Partners—a design-build joint venture of Dragados USA, Vinci, Dodin Campenon Bernard and Flatiron Constructors—is also constructing 17,000 ft of new and upgraded marine trestles to expand the crossing from four to eight lanes to better accommodate daily traffic volumes that can top 100,000 vehicles during peak summer months.

Two lanes in each direction will carry general purpose traffic, with the other two designated as tolled express lanes, and revenue earmarked for operations, maintenance and funding other infrastructure projects in the region.

Although the TBM cutterhead is out of the tunnel, the department says it still has five rings to install before it can be dismantled, a process expected to get underway in November following removal of the project's 92,500-sq-ft slurry treatment plant, with a flow rate capacity of 13,200 gpm—the largest in North America, the Virginia DOT says. The contractors will now continue with interior build-out of both tunnels.

The DOT says the project, which began in 2020 and also includes 25 new and reconstructed bridges and highway capacity additions on the Hampton and Norfolk sides of the harbor, has remained on track since “unforeseen cost and schedule impacts” forced an early-2024 reset of its comprehensive agreement with the contractors.

Great engineering project! The boring machine is setting world records moving 366 ft per week. Massive heavy civil project!