Big Dig tunnels sound, US says

The Big Dig's tunnels are structurally sound despite hundreds of roof leaks and dozens of wall defects, according to a Federal Highway Administration report released yesterday, but the state must develop an aggressive tunnel inspection program to ensure the roadway's future safety.

The report, issued roughly six months after a massive leak flooded the Interstate 93 northbound tunnel, also says that the tunnels will probably always be susceptible to leaks, which could pose a long-term corrosion threat to the steel beams that form the spine of the roadway.

However, the report's authors did not offer a solution for how to fix two seriously defective wall sections that have sprung leaks, which means a continuation of the debate raging among project officials for the past six months over how best to repair the walls.

Earlier this year, two independent engineers hired by the Massachusetts Turnpike Authority said they could no longer vouch for the safety of the system because they said they were denied key documents and data related to an internal leak investigation being carried out by managers Bechtel/Parsons Brinckerhoff. The engineers' statements, which Turnpike officials strongly denied, were followed by disclosures of other flaws by project officials.

All told, 60 weak spots have been discovered in the tunnels' 3-foot-thick slurry walls, two of them requiring major repair work, and there are hundreds more leaks where the tunnel walls meet the roof. In addition, about 1,200 square feet of sprayed-on fireproofing, out of roughly 1.8-million square feet total, were destroyed by water and ice, yesterday's report said.

The federal report was written by a team of senior engineers from around the country who conducted a three-day assessment of the tunnels in December. It concludes that efforts to patch the roof leaks are progressing and that the work to inject as many as 3,585 leaking areas with sealant should conclude this summer. However, the report warns that ''the submerged nature of the tunnel system makes it unlikely that intrusion by water can be completely eliminated" and that ''a primary concern with these leaks is the corrosion of roof steel I-beams."

Despite that concern, the tunnel system ''is structurally sound and remains safe for traffic," Mary E. Peters, administrator of the Federal Highway Administration, says in a cover letter accompanying the report. She ordered the report after the leaks were disclosed last fall.

The report relied on site inspections and interviews with 16 state, federal, and Bechtel/Parsons Brinckerhoff officials and cites numerous documents as references, including an internal Bechtel/Parsons Brinckerhoff memo, draft investigation reports by the managers, a December US Department of Transportation report, and databases and other reports dating from 1997. It was unclear whether those documents were the same ones that engineers Jack K. Lemley and George J. Tamaro, who raised questions about the tunnel system, had requested but did not receive as part of their investigations. Neither man could be reached yesterday.

Turnpike Authority chairman Matthew J. Amorello and Andrew Paven, a spokesman for Bechtel/Parsons Brinckerhoff, said in separate interviews yesterday that the federal report confirms their repeated assertions that the leaks are not a threat to safety and that the leaks are fully repairable.

''It's great to have an independent source confirm the safety of these tunnels," Amorello said. ''They were safe when we opened them, and they still remain safe."

Said Paven: ''Motorists and taxpayers should be assured by this expert confirmation that the Big Dig is safe and the program to address the leaks is on target."

State lawmakers and a spokesman for Governor Mitt Romney said they, too, were generally pleased with the report's findings, but said the fallout from the leaks is far from over.

''There is still a serious ongoing problem with respect to the leaks, and this report doesn't absolve the current management of the Turnpike Authority from its inability to successfully manage this project to completion," said Romney's communications director, Eric Ferhnstrom.

After the Globe first reported the leaks problem in November, Romney called on Amorello to resign, but he refused.

Yesterday, Amorello said he was confident that the Turnpike would satisfy the mandate in the federal report to create an aggressive inspection program to keep an eye on leak-related damage. He said project officials are writing protocols that will call for inspections of the tunnel walls and roof connections every two years ''at a minimum." The inspections would help alert authorities to deterioration of the steel beams.

''This is the first slurry-wall-constructed tunnel in the country; this is going to be a prototype," Amorello said. ''On this project, it's brand new, and we don't expect major capital investments for 10 to 15 years."

Attorney General Thomas F. Reilly, who recently took over efforts to recover money from Bechtel/Parsons Brinckerhoff and contractors for leak-related costs, said he considers the real threat to Massachusetts drivers the costs associated with fixing the leaks, both now and in the future.

''The real problem here is that taxpayers have not gotten the tunnel that we paid for," said a statement Reilly issued. ''We did not pay for a tunnel that leaks. My focus remains squarely on Bechtel and the contractors: They need to step up to the plate, fulfill their professional responsibility, and design a lasting solution to fix the leaks at no cost to taxpayers."

State Senator Steven A. Baddour, cochairman of the Legislature's Joint Transportation Committee, agreed. ''There's an inherent design flaw with the tunnel, and we need to make sure the taxpayer's not left holding the bag at the end of the day," he said.

Repairing the two wall sections with the largest defects -- one of which sprang a leak on Sept. 15 that caused a 10-mile traffic jam -- will be a costly and complicated affair, and Big Dig officials have been arguing for months over how best to take on that task.

The report's authors did not back any of the three competing methods proposed to repair the sections. One method proposed by Tamaro, a renowned slurry wall specialist who left last month after alleging that Turnpike officials blocked his ability to work on the leak problem, entails rebuilding the entire defective wall sections. That would be a major and expensive undertaking that would leave the tunnel looking as it was supposed to, if it had been built properly in the first place.

The two other proposals -- put forth by contractors Modern Continental Co., which built the defective areas -- call for filling the defective areas with grout and putting a large steel plate over them or, going one step further, covering each steel plate with a 10-inch thick concrete slab.

All methods could cost hundreds of thousands of dollars, and require closing at least one traffic lane during off-hours.

The report's authors stipulated that whichever method is chosen must ''provide a durable and effective barrier against moisture from entering the tunnel, be relatively maintenance free, and neither interfere with other tunnel systems nor detract from the tunnel's finished appearance."