Mary the tunnel boring machine has completed the first half of her mission to build two tunnels for the Hampton Roads Bridge-Tunnel Expansion, the largest highway project in Virginia history.
Mary broke through the North Island headwall on her yearlong dig of the state’s first bored roadway tunnel and only the third in the U.S. She dug through 7,900 feet of soil while placing concrete segments along the way, according to the Virginia Department of Transportation.
Watch the video of her historic breakthrough at the end of this story.
Her breakthrough ends in a 160-foot-diameter receiving pit that also made history for the state as its largest continuous concrete pour. The pit to hold the 4,700-ton Mary required 31-hours of nonstop pouring of concrete that was hauled in by 584 trucks.
The result is a 9-foot-thick base slab below sea level that is heavy enough to resist buoyancy from the water. The pit is 75 feet deep and contains 1.5 million pounds of rebar.
A map of the $3.9 billion Hampton Roads Bridge-Tunnel Expansion Project, scheduled to be completed in August 2027.Virginia Department of Transportation
One new trestle bridge for eastbound traffic out of Hampton to North Island is scheduled to open by May 1. The existing bridge it replaces will be demolished. The new bridge is 6 to 8 feet higher than the old bridge to accommodate sea-level rise and reduce salt spray. A new trestle bridge will also be built to replace the other existing bridge.
The project was originally scheduled to be completed in 2025 but has since been delayed 18 months to August 2027. The design-build team for the project is Hampton Roads Connector Partners, a joint venture with Dragados USA as lead contractor and HDR and Mott MacDonald as lead designers.
As for Mary, the next step is to reposition her to head in the opposite direction, which can take about six months. Then she’ll spend the next year digging a new, identical tunnel to the South Island.
Check out the VDOT video below as Mary breaks through the North Island wall April 17:
Quick Facts About Mary:
- Height: 46 feet
- Weight: 4,700 tons
- Length: 430 feet
- Cost: $70 million
- Launch: April 2023
- Dig rate: 50 feet a day
- Dig depth: 50 feet below current tunnels
