FHA finds Boston's `Big Dig' tunnels structurally sound, despite leaks

`Aggressive' inspections urged for Massachusetts

April 05, 2005|By NEW YORK TIMES NEWS SERVICE

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 Massachusetts must develop an "aggressive" tunnel inspection program to ensure the roadway's future safety.

The report, coming about six months after a huge leak flooded the Interstate 93 northbound tunnel, also says 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 fixing two seriously defective wall sections that have sprung leaks, which means the debate raging among project officials for the past six months over how best to repair the walls will continue.

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 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 about 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 sometime 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."

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