Big Dig leak repairs to take years

Leaks in the Big Dig's Interstate 93 tunnel roof will persist for years to come, despite current efforts to patch them with a grout sealant, according to an independent report released last night by the Massachusetts Turnpike Authority.

The grouting program will seal an estimated 3,600 leaks in the tunnels this year, but more than 42 percent of those seals are expected to reopen, requiring a second round of grouting, the report said.

At a result, Turnpike Authority managers estimate they will face 1,543 leaks next year, 661 in 2007, 284 in 2008, 121 in 2009, and 77 in 2010, the report says. No estimate is made beyond 2010.

The cost of sealing those leaks is expected to drop from $7.3 million this year to $3.1 million in 2006, $1.3 million in 2007, $574,000 in 2008, $246,500 in 2009, and to $156,000 in 2010, based on a per-leak repair cost of $2,029.

The estimate was contained in a report posted on the Turnpike Authority website at about 7 p.m. yesterday.

Mariellen Burns, the authority's director of communications, did not return calls last night, and in her e-mail notifying reporters of the report, she did not address the future cost of leak repair and maintenance. ''The bottom line of the report is that managing water is a part of any underground construction project," she wrote.

Turnpike officials, including chairman Matthew J. Amorello and project director Michael P. Lewis, could not be reached for comment last night.

In November, when the Globe reported that the I-93 tunnels had hundreds of leaks, Jack K. Lemley, an outside consultant hired to investigate the problem, said of future repairs: ''You're talking years here, even a decade."

Turnpike Authority officials and the Big Dig's management consultant, Bechtel/Parsons Brinckerhoff, disputed that statement. ''The program to seal leaks will be completed within months, not years," Bechtel/Parsons Brinckerhoff said in a statement issued Nov. 23.

But since then, Turnpike Authority officials have acknowledged that significant work will continue on the massive tunnel and highway project at least through January, four months after its long-pledged substantial completion date of September.

Estimating the number of future leaks is a risky venture, said Deloitte Financial Advisory Services, the consultant hired to study the impact of the two kinds of defects that have plagued the project as it nears completion. Those flaws are the thousands of small roof leaks at the roof-wall joints of the tunnels and the 189 soft spots in the tunnel walls, including the one that breached and flooded the northbound roadway on Sept. 15.

''As the work continues, the recurrence rate [of leaks] could change," the report posted last night said. ''Any increase in the recurrence rate will result in more grout locations and higher incurred costs by MTA until a steady state is reached."

The Deloitte report said no estimate of the cost of future leaks had been made by the Turnpike Authority or Big Dig managers until March. At that time, Kenneth M. Mead, the US Department of Transportation's inspector general, was threatening to hold up $81 million in federal funding for the project unless he was assured that Turnpike Authority officials were adequately addressing the leaks. The Deloitte report also concluded that fixing and preventing leaks has cost $38 million. Nevertheless, the report said the total cost for the Big Dig should remain within the estimate of $14.625 billion because the leak costs are paid from contingency accounts.

Sean P. Murphy can be reached at smurphy@globe.com.