BOSTON (AP) – Dave Weibe no longer finds himself nervously eyeballing the Big Dig’s ceilings from the driver’s seat of his car, but that wasn’t always the case.

After concrete slabs ripped away from the ceiling of a Big Dig tunnel a year ago, crushing a car and killing a passenger, Weibe had second thoughts about entering any of the project’s tunnels.

“Right after the accident, I was driving through the tunnel about twice a week and I would scope out the job they were doing half-expecting to see something shoddy,” said Weibe, 25, who works in the banking industry in Boston.

Weibe wasn’t the only anxious driver in the wake of the accident.

The $14.798 billion Big Dig – the costliest highway project in U.S. history – had torn up downtown Boston for more than a decade, plaguing drivers with traffic turmoil, leaky tunnels and a symphony of jackhammers.

But until the night of July 10, 2006, the Big Dig hadn’t killed any motorists.

Then, 12 tons of ceiling panels dropped from the Interstate-90 connector tunnel leading to Logan International Airport, flattening a car carrying Angel Del Valle, 46, and his wife Milena, 39, on their way to pick up his brother and sister-in-law returning from a trip to Puerto Rico.

The passenger side where Milena sat took the brunt of the force.

Angel Del Valle managed to crawl out of the rubble with minor injuries. Milena Del Valle died. The car was just yards away from exiting the tunnel.

On Tuesday, the anniversary of the accident, the National Transportation Safety Board is expected to approve a final report on the probable cause of the tunnel collapse. The board is also expected to issue a series of recommendations.

Del Valle’s death has stained the project’s already pockmarked reputation.

The accident investigation quickly focused on the bolt-and-epoxy system holding the concrete slabs to the ceiling. Portions of the tunnels were shut down for months as workers methodically replaced all suspect bolts with an improved fastener system.

In January, seven months after the accident, traffic again began flowing through the portion of the tunnel where Milena Del Valle died.

After the accident, the state launched an extensive review of the safety of the entire Big Dig, concluding those safety systems were “conservatively designed and fundamentally robust,” according to state Transportation Secretary Bernard Cohen, chairman of the Massachusetts Turnpike Authority, which oversees the project.

“That doesn’t mean that there aren’t things that we need to address, but nothing that is an immediate safety concern,” Cohen said.

The accident also prompted a series of state and federal, civil and criminal investigations, including the NTSB review.

Massachusetts Attorney General Martha Coakley is expected to announce soon whether she’ll press criminal charges in connection with the accident. Coakley’s predecessor, former Attorney General Tom Reilly, said the accident could lead to charges of negligent homicide.

Also pending is a wrongful death lawsuit filed last August by Del Valle’s family against the Turnpike Authority and several companies associated with design and construction of the project, including project manager Bechtel/Parsons Brinckerhoff and Modern Continental Construction Co., the company that constructed the I-90 connector ceiling.

The companies have said they stand behind their work.

Angel and Milena Del Valle met four years before the accident after he moved to the United States from Puerto Rico and she moved from Costa Rica. Their lives revolved around family and church.

Angel Del Valle said he saw the concrete panels coming down but couldn’t avoid them. “I think that God chose Milena and I to go through this so another bigger tragedy could be avoided,” he said the day after he and Milena Del Valle’s daughter filed the lawsuit.

Jeffrey Denner, attorney for Angel Del Valle, said Thursday the family is pressing forward with the lawsuit as they try to put their lives back together.

“They’re doing fine. They have a lot of loss to deal with, but they’re moving forward,” Denner said.

Bradley Henry, a lawyer representing Milena Del Valle’s family including her daughter Raquel Ibarra Mora, said the state and federal probes should shed more light on the accident.

“We are going to learn a great deal about what happened in this collapse in the month of July,” he said. “All the various investigations are starting to coalesce.”

There was also plenty of political fallout from the accident.

The tragedy gave then Gov. Mitt Romney, who had been spending increasing amounts of time out of state prepping for an expected presidential run, a chance to demonstrate his crisis management skills.

Romney held a series of televised press conferences, coolly explaining what went wrong – hand-drawing diagrams with black marker on large sheets of white paper.

He also shook up the management of the project, forcing the eventual ouster of then-Turnpike Chairman Matthew Amorello.

“Romney overcame what could have been a pretty big blow,” said Julian Zelizer, professor of history and public affairs at Princeton University. “This is going to be the example of what he accomplished as a crisis manager. You could contrast this with (Hurricane) Katrina.”

A year after the accident, most drivers readily use the tunnels.

“I’ve never been worried about it,” said Susannah Pugh, a 25-year-old paralegal from Waltham. “It’s sad, but it’s not something I worry about.”

Even Weibe has put his initial fears behind him.

“At this point, I really don’t think about it,” he said.

Cohen conceded that the death of Milena Del Valle and the revelations of flaws in the Big Dig’s tunnels will be an unwelcome part of the project’s troubled legacy.

But he also said the accident shouldn’t overshadow the benefits of the project, which has alleviated one of the most notorious bottlenecks on the eastern seaboard.

“It will inevitably be part of the unfortunate history of the project, but if it results in higher sensitivity to safety issues on the part of designers and builders, my hope is that this will have some positive impact,” he said.