After long insisting that the Big Dig would be substantially complete in September, project officials acknowledged yesterday that significant work, and some traffic detours, will continue through January.
Project manager Michael P. Lewis said in a meeting with the Globe that work to repair hundreds of leaks will stretch into next year and require regular early-morning closing of both the northbound and southbound Interstate 93 tunnels.
Just to repair a section of tunnel wall that ruptured on Sept. 15 will require 60 to 90 shifts of overnight work, which will force the shutdown of the northbound tunnel and divert motorists onto surface streets. Lewis said that the repair, which is scheduled to begin shortly, will cost between $300,000 and $500,000 and be paid for by contractors.
In addition, he said, the entrance ramp to the westbound Massachusetts Turnpike from Kneeland Street will not open until at least November, and work will also continue after September to construct some of the streets on the project's surface, which surrounds the new Rose Kennedy Greenway.
Since 2003, Big Dig officials have said the project would be mostly finished no later than September 2005. Despite the discovery of hundreds of leaks in the tunnels last fall, project manager Bechtel/Parsons Brinckerhoff said in a statement that finding and repairing leaks ''should be substantially complete, along with the rest of the project, by the summer of 2005."
''Proper repairs will take months, not years, to complete," the statement said.
But the schedule outlined by Big Dig officials yesterday was triggered in part by this week's approval by the Federal Highway Administration of the authority's plan for fixing the section of wall that ruptured Sept. 15.
Lewis and other project officials acknowledged yesterday that the delays will prolong inconvenience for motorists. The continuation of work past September also could further diminish the public credibility of the $14.6 billion project, which was already damaged last fall by the disclosures about the leaks.
A spokeswoman for the Turnpike Authority said yesterday that, despite the work that will continue beyond September, the agency believes it has essentially met its goal. Two more ramps to the Interstate 93 tunnels are due to be opened in August, Burns said, one from Essex Street to the northbound roadway and the other one from Summer Street to the southbound side. She said project officials always expected that the ramp from Kneeland Street would not be done until after September.
''Substantial completion is this fall, by the end of September, when most of it is open," said Mariellen Burns, Turnpike Authority spokeswoman.
But Lewis acknowledged that for those detoured off the highway due to ongoing repairs the project may not seem complete or even substantially complete.
''For people who are driving at night, it will be a pain," Lewis said.
The Big Dig is scrambling to repair two kinds of leaks plaguing the tunnel. One kind, like the Sept. 15 major rupture, is caused by construction defects in tunnel walls and requires extensive repair. The other, more numerous, kind is generally located in the tunnel roof area and is caused by waterproofing failures. Those leaks are being sealed with grout.
Big Dig officials did not provide a detailed schedule for their leak repair program. Lewis said three contractors would be involved in repairing the 169 wall sections found defective. But, Lewis said, only one contractor, Modern Continental Construction Co., has begun that work.
''Modern has completed something on the order of 20 to 25 repairs to date" while contractors J.F. White Contracting Co. and Jay Cashman Inc. ''haven't even started yet," he said.
Leaks in the Big Dig tunnels became a national story in November, after the Globe, relying on interviews with outside consultants hired to investigate the Sept. 15 leak, first reported the existence of more 700 leaks in the tunnels.
Doug Hanchett, a Turnpike Authority spokesman, said last evening that the number of leaks has been reduced to ''below 400," but could not provide an exact number.
Repair crews are working on the most serious leaks, in which water is dripping or trickling, and should move on to less serious leaks in September, with completion in January, Burns said.
All the repairs require full or partial closing of the I-93 tunnels, Lewis said, because workers need to use heavy equipment and gain unimpeded access to much of the roadway. Project officials attempt to limit the closings to the early morning hours, generally 1 a.m. to 4:30 a.m. Traffic is diverted onto nearby surface streets, such as Atlantic Avenue and Purchase Street.
For some drivers, the seemingly never-ending nighttime closures are an ongoing frustration.
Melissa Majkut often makes the trip at night from her boyfriend's place in Quincy to her home in Allston. It's normally a 15-minute trip up I-93 and west on the Massachusetts Turnpike, she said, but frequent ramp closings force her to exit into Chinatown and snake toward the next turnpike entrance. That can add 30 minutes to her trip.
''I often cut the night short because I don't want to get caught going around the crazy detour," she said. ''I want to leave by 9 because I don't want to get stuck. He thinks I'm crazy, but I really don't like to do the detour."
David Hart of Salem said he got stuck in a terrible traffic jam on a recent Friday night while trying to drive home after attending the opera. Anticipating the northbound I-93 tunnel would be closed, Hart headed to Storrow Drive, expecting to use the ramp there onto northbound Route 1. Instead he found Storrow Drive gridlocked and the ramp also shut down.
''There were hundreds of people sitting there idling, burning gas," Hart said. ''You just can't trust what's going on. There are so many delays and closures down there."
Hart said he will avoid driving into Boston at night until all Big Dig work is finished. ''You can't predict it," he said. ''You feel trapped."