“Chessie,” a German-made tunnel-boring machine inadvertently unearthed an old artifact while digging deep under the Chesapeake Bay floor. The ‘discovery’ added eight months to the project while crews had to replace 389 cutting tools by hand. The fragments that reached the surface on the conveyor belt came from an old anchor whose owner is unknown.
While Chessie’s job is finished, the new Thimble Shoal tunnel will not be ready for use until early 2028. Paving, drainage, waterproofing, ventilation, fire protection, emergency exits, electrical connections, and other support structures must be finished before drivers can enjoy this widened shortcut.
Why Virginia needs another tunnel
Four million drivers per year currently take the 17.6-mile trip from Virginia Beach to the Eastern Shore on the Chesapeake Bay Bridge-Tunnel (CBBT).
According to federal project data, the original Thimble Shoal tunnel averages 25 accidents or breakdowns per year, causing frequent lane closures along with oversized-load transports. Opened in 1964, it provides only one lane in each direction within the same tube.
The new tunnel will house two southbound lanes, converting the existing tube to a northbound-only tunnel.
Chessie met something no survey found
Chessie is a 3,075-ton beast with a 43.5-ft. cutterhead. Built by Herrenknecht in Germany, it is nearly as long as an American football field.
After boring through about 700 ft. of earth in 2023, it collided with an anchor marked W. L. Byers & Co. CBBT determined it was English-made, most likely from the turn of the 20th century, but no records of the boat it belonged to have been found.
The repair happened under pressure
Crews could not just ‘throw it in reverse’ and back out, as Chessie had already lined the tunnel behind with concrete. Through air locks, crews entered the pressurized excavation chamber at the face of the digger and got to work removing debris and repairing the cutterhead.
They had to replace almost 90% of the 150-lb. cutting tools in addition to 48 wear plates–all by hand.
Once moving, Chessie moved fast
Despite the collision, everything else on the massive machine remained intact and functional, allowing tunneling to resume in early April 2024.
Chessie proceeded to go on a tear of 50 ft. per day, reaching Two Island in late January 2025. She had mined more than 6,300 feet, displacing about a half-million cubic yards of soil and installing about 10,000 10-ton concrete segments to line the tunnel.
Why the finished hole still needs years
At a total cost of $1.074 billion according to the Federal Highway Administration, there is still much work to do.
Now that each tunnel will carry traffic in one direction, flow and safety will improve markedly once the tunnel is completed. Lane closures will be less an issue with more space to maneuver.
Drivers may not fully appreciate the arduous process of the 3,000-ton behemoth and its unexpected discovery, or the efforts of crews manually replacing cutters and laying concrete under the bay floor. The convenience and safety, however, will pay dividends for generations to come.
The latest official project update was published by the Chesapeake Bay Bridge-Tunnel.
