Final Big Dig section to open

Eleven months after a fatal ceiling collapse in a Big Dig tunnel, the final section under repair was set to reopen today, finally allowing traffic through the entire tunnel network.

At about 2 a.m., car pool vehicles and buses will have access to a reserved lane eastbound in the Interstate 90 connector tunnel, officials said yesterday.

The July 10 ceiling collapse, in which Milena Del Valle of Jamaica Plain was killed while riding in a car to Logan International Airport, triggered national headlines and a traffic-choking shutdown of parts of the city's highway system.

When inspectors scurried into the crawl spaces above tunnel roadways, they found construction flaws that forced the replacement of thousands of bolts that apparently failed in the collapse and hundreds of steel brackets that didn't meet standards for how much weight they must be able to support.

The extensive repairs delayed the first reopenings until September. The last major reopening, of the ramp connecting Interstate 93 north to I-90 east, was in January. Motorists and politicians, alike, said they didn't feel safe in the tunnels.

Almost a year later and after $54 million in repairs, Governor Deval Patrick's administration announced the final reopening yesterday and declared public confidence restored. "After 10 months, the tunnels are back to normal, back to the way they were before the July 2006 tragedy," Transportation Secretary Bernard Cohen said in a statement.

"These tunnels have now been inspected and reviewed more than any highway or tunnel in state history," he said. "This was an exhaustive but necessary process to restore public credibility."

It was also an expensive process.

The state is suing several contractors, including the project design and construction manager, Bechtel/Parsons Brinckerhoff, to recover the $54 million to design, repair, and inspect the tunnels.

Most of the money went to contractors to retool the ceiling support system. Most of the I-90 connector relied on bolts and epoxy, a sort of superglue, to hang 4,000-pound concrete panels from the roof and form a 4-foot-high crawl space used as a ventilation duct.

The other major expense incurred by the state was overtime for police to direct traffic around the road closings.

Commuters greeted the HOV lane opening with relief.

"My commute has been hell," said Dan Krueger, a consultant from East Boston. "In September of last year, I just gave up."

"I'm glad they're finally opening it," said John Lauser, a systems analyst from Weymouth, who said he travels to the airport about twice a month.

And while the repairs are done, the search for responsibility for the collapse goes on. Lawyers for Del Valle's family have named Bechtel/Parsons Brinckerhoff and a dozen other contractors on the Big Dig -- including designers, builders, and safety inspectors -- in a civil suit.

Criminal investigators from the offices of US Attorney Michael J. Sullivan and state Attorney General Martha Coakley are separately pressing their own cases.

The Globe reported last month that criminal investigators are focusing on whether contractors used the wrong adhesive to install at least some of the bolts in the area where the ceiling collapsed.

Invoices from the 1999 ceiling construction job show that the building contractor received and apparently used at least one case of a quick-drying epoxy to secure ceiling bolts to the tunnel roof, rather than the standard epoxy, which the ceiling designers had specified. The difference may be crucial because the fast-set epoxy holds 25 percent less weight than the standard and is not recommended for suspending heavy objects overhead.

Globe correspondent Michael Naughton contributed to this report. Sean Murphy can be reached at smurphy@globe.com.