VIRGINIA BEACH — Now that the anchor’s away, expansion work at the Chesapeake Bay Bridge-Tunnel is back at full bore.

Burrowing of a new tunnel to help carry more vehicles between Virginia Beach and the Eastern Shore has resumed about 10 months after a gigantic boring machine struck an old ship anchor buried beneath a shipping channel .

Tunneling was suspended so workers could investigate the obstruction, excavate the 10-foot-long anchor — which was in several pieces — and replace machine parts damaged by hitting the anchor.

The tunnel boring machine known as Chessie got back to work on April 8, days before the 60th anniversary of the bridge-tunnel’s opening on April 15, 1964.

“We’re making very good progress now that it’s back working,” Mike Crist, the deputy executive director overseeing infrastructure for the Chesapeake Bay Bridge and Tunnel District, said Friday during a visit to the work site. Chessie is tunneling about 50 feet a day and has bored 1,600 feet total, about 25% of the planned distance of 6,400 feet.

While other construction work continued during the stoppage, the anchor added 241 days to the project, pushing completion from December 2026 to August 2027, Crist said.

It also added $60 million to the project’s $756 million cost. Insurance is expected to cover most of that extra cost, he said. Funding for the project comes from toll revenue. The project began in 2017 and was to be finished by 2022 but has experienced several delays.

The 17-mile-long bridge-tunnel now has two lanes of traffic in each direction. Traffic converges into one lane each way in the two tunnel portions, each a mile long. The expansion project is adding a parallel tube to the Thimble Shoal Channel. The new tube will carry two lanes of southbound traffic; the original tube will carry two lanes of northbound traffic. The northern tunnel is expected to undergo a similar expansion in the 2030s.

Tunnel construction comprises the remaining portion of the current expansion. Chessie is building the tunnel liner. The machine has a steel cutter head 43 feet in diameter and is about 300 feet long — the length of a football field.

Chessie began mining the tunnel in February 2023 and had tunneled about 750 feet by that May, when workers spotted large pieces of steel on a conveyor belt that carries muck from the tunnel to the bay’s surface. More pieces were excavated later.

One piece was engraved “W.L. Byers & Co.” That company, based in Sunderland, England, produced anchors from the 1860s to about the 1950s, Crist said.

How the anchor got buried and to which ship it belonged are unknown, Crist said.

“No one has claimed it,” he said, adding that the anchor was of a very common type. It weighed about 3.5 to 5 tons and likely was intact before the boring machine “chewed it up and snapped it into pieces,” Crist said.

Chessie “was grinding on it before we knew it was there,” he said.

All that grinding damaged Chessie as well; 389 of the 442 tools, such as discs and scrapers, on the cutter head had to be replaced, said Tom Anderson, deputy executive director in charge of finance and operations for the bridge-tunnel. So did 48 wear plates.

From June to December, crews created a safe haven for accessing the cutter head from inside the machine without fear of a cave-in or blowout. They grouted the ground in front of Chessie to pressurize an excavation chamber and prevent water and sand from flowing in. While not in water, the workers were under the kind of pressure divers experience, Anderson said.

January through March was spent restoring the cutter head to working condition.

“The plan that the workers developed to remove the anchor, execute that removal and fix the cutter head in those conditions was pretty incredible work,” Crist said. “It was an unexpected challenge, but they’ve overcome it.”

“Now we’re back to tunneling. Everybody’s relieved.”