TBM Mary broke through at the South Island to complete the second of the twin-bore tunnels under the Hampton Roads Harbour, marking the end of 29 months of tunnelling.
The achievement was celebrated at a ceremony attended by tunnelling crews, Governor Glenn Youngkin, US secretary of transportation Sean Duffy, Virginia secretary of transportation Shep Miller, Virginia Department of Transportation (VDOT) commissioner Stephen Brich and other VIPs and guests.
Boring on the second tunnel began on October 17, 2024 and was completed three weeks faster than the first 2.41km-long bore.
TBM Mary’s 14m-diameter cutterhead has broken through the diaphragm wall but six more concrete rings need to be installed to complete the tunnel construction.
The project’s design-build contractor, Hampton Roads Connector Partners – a consortium of Dragados USA, Vinci, Flatiron Constructors, and Dodin Campenon Bernard – marked several milestones during tunnelling, including a more than 111.5m advance in a single week – a world record for a machine of TBM Mary’s size.
After completing the first bore, TBM Mary was turned 180 degrees using nitrogen skates – the first time the method had been used in the US.
US transportation secretary Sean P Duffy said the final breakthrough demonstrated “what’s possible when collaboration meets innovation to build big, beautiful infrastructure”.
The HRBT is the largest highway construction project in Virginia’s history. The tunnels are scheduled to open in 2027.
