NORFOLK, Va. (WAVY) — Though you can see the cranes, construction equipment and the bridgework as you drive up and down Interstate 64 through the Hampton Roads Bridge-Tunnel area, what you can’t see is just as important.

Intricate work is being done 65 feet below the road surface as part of the nearly $4 billion expansion project, the largest in Virginia history, that will widen the highway in both directions with the hope of mitigating traffic between the Southside and the Peninsula.

In an aerial photo, the Virginia Department of Transportation explains what is happening below the surface — Mary the tunnel boring machine sitting “with its cutterhead flush against the headwall, and most of her trailing aligned and in position” for the second round, a twin tunnel to be mined toward Norfolk.

Back in June, Mary, which does all the digging work to create tunnels, finished her last ring to support the newest eastbound tunnel. From that point, crews have been working to ensure she’s ready for her next mission — digging the second new eastbound tunnel, which is expected to begin sometime this fall.

“April 17 was that very dramatic day where that headwall came crashing down, but today is just as important as you can walk in free air between the two islands really marking that halfway point in the structural construction of our two new bored tunnels,” said Project Director Ryan Banas back in June.

Mary had just finished her 1,191st ring, which structurally completed the new tube, and at its deepest point, it has been about 173 feet below the water’s surface.

The expanded tunnels will be the first bored tunnel in Virginia, and the third overall in the U.S.

Banas said in a recent, fall update on the project that crews have been hard at work. In late June, he said they rotated the cutterhead and shield 180 degrees. At 2,500 tons and a 46-foot cutterhead, it was a record-setting operation, he said.

Crews are in the process of pulling their gantries out and bringing them to the surface by using two 800-ton cranes, rotating them 180 degrees and placing them back down into the shaft.

“The operation, once fully complete, means that Mary, our tunnel boring machine, will be completely reassembled,” Banas said. “That will allow us to relaunch her for her second tunnel here in the fall of 2024.”

Ground was broken for the HRBT expansion project nearly four years ago. In late September 2023, VDOT said it was about a year behind schedule, and in March, had estimated it would be finished by February 2027. However, Banas said in June they could be on track for an early completion, by September 2026.

“Our contractor is still on track to meet that date (February 2027), moreover, they’re trying to achieve a September 2026 early completion date right now,” Banas said, “so we are working with them day in and day out trying to achieve that early completion date that will allow traffic to move through the corridor on new construction even sooner.”