It was not exactly the inside of the Sistine Chapel, but the Callahan Tunnel looked pretty good, as mile-long, barren passageways go.
The floor was paved into a smooth sheet of concrete. Brand-new curbs were installed in neat lines against the walls. Perhaps most important, the construction project was on track to finish by its deadline.
During a Friday afternoon media tour of the construction site, Frank DePaola, highway administrator, announced that the tunnel may even be completed up to two days earlier than its March 12 end date.
Since before the tunnel was closed Dec. 27, DePaola has expressed confidence that the project would conclude on time. Now, he says, the prospect that the construction crew will meet their deadline has become certain.
“It’s definitely a sure thing,” said DePaola.
By next week, he said, officials will know if the tunnel will reopen early.
The $34.9 million project was prompted by the need to rebuild the tunnel’s concrete floors, which had deteriorated so badly that a manhole fell through the foundation of the deck into an air duct below.
Now, light gray concrete stretches from the North End to East Boston. Soon, a layer of asphalt several inches thick will be spread atop the concrete, and after that, workers will apply a spray-on material that seals and waterproofs the asphalt.
DePaola warned that people at either end of the tunnel might smell an odor as the sealing material is applied to the road, but he said it would not pose a health hazard when it mixes with fresh air.
Workers inside the tunnel will wear protective gear so they do not inhale the compound.
“Outside of the tunnel, it will be well within the levels that are safe,” DePaola said.
The biggest challenge of the project was breaking apart the old concrete using high-
pressure water, but DePaola said the demolition went better than expected.
“The condition of the deck was such that we weren’t sure how that would go,” DePaola said.
Some construction will continue after the tunnel reopens to traffic, part of the plan that DePaola announced last year.
Officials will close the tunnel overnight on several weekends to allow the construction team to install large wall panels onto the stainless steel clips currently bolted into the tunnel’s original siding.
Some of that work will continue during off-peak hours into the summer, DePaola said. Scheduling those shorter closures will be challenging, because officials will have to plan around upcoming weekend construction work planned for the section of the Massachusetts Turnpike underneath Hynes Convention Center, as well as road closures for the Boston Marathon.
“It’s a little bit of a dance for us,” DePaola said.