Sumner Tunnel restoration on schedule, one-third completed, officials say

A worker on a lift in the Sumner Tunnel, which is closed for repairs.David L. Ryan/Globe Staff

Construction on the Sumner Tunnel, which carries southbound traffic on Route 1A under the Boston Harbor, is about 33 percent complete and going smoothly, highway officials said Tuesday.

Speaking to reporters just outside the tunnel’s entrance in East Boston, MassDOT District 6 Highway Director John McInerney said progress was “pretty much in line” with the project’s timeline, and he is confident the tunnel will reopen on schedule at the end of August.

“There’s some extra work that the contractor’s dealing with, but I wouldn’t call it unforeseen,” McInerney said. “The work’s pretty straightforward, it’s just the amount of it.”

Crews closed the tunnel July 5 to begin round-the-clock repairs.

During the Tuesday morning rush, traffic had slowed to its now-typical sluggishness. It took drivers more than 30 minutes to cross the Zakim Bridge from Chelsea, and getting to Government Center from East Boston took about 25 minutes, according to traffic data provided by Mass511.

Although traffic toward Logan International Airport is relatively smooth, the journey into Boston is sharply delayed, and officials are still cautioning riders to add two extra hours of travel time to any trips to or from the airport.

Once construction is completed, the restored tunnel’s design life is expected to be 50 years, according to Marshall Hook, a MassDOT spokesperson.

Earlier in the afternoon, a worker used a Magni lift — a piece of machinery similar to a gigantic forklift — to haul one of more than 780 pre-cast concrete arches into the middle of the tunnel. Those arches will help reinforce the tunnel’s aging ceiling and improve ventilation, according to McInerney. He said 200 tiles had been installed by Tuesday morning.

A curved pre-fab ceiling tile made its way into the tunnel on a machine similar to a giant forklift.David L. Ryan/Globe Staff

The tunnel was just barely wide enough to accommodate the arch, itself more than 22 feet wide. Project manager Chris Blanchard said the tunnel was too narrow for the vehicle to turn around, so the driver has to drive out in reverse.

“He goes all the way back and forth all day long,” Blanchard said. “Two miles an hour down and a little faster coming back. It’s pretty slow.”

Crews are installing about 16 arches per day, enough to cover 96 feet of tunnel, Blanchard said. Working from the center of the tunnel out, workers filled the gaps between newly installed panels with grout and orange sealant, which dripped into small foam stalactites as it expanded.

McInerney said crews need to complete work on the East Boston side of the tunnel, but not the entire route, by August 31 to ensure the tunnel is able to safely welcome the return of traffic. The rest of the project will be completed during weekend closures this fall and another full closure next summer, according to MassDOT.

During the restoration, crews are installing new fire prevention boards, fresh pavement, and improved lighting and security systems. The project should bring the tunnel, opened in 1934, up to modern code.

“It has had maintenance over the years,” McInerney said, but “it’s getting tired.”