Number of Big Dig leaks drops from thousands to hundreds

December 17, 2007 01:34 PM Email| Comments (0)| Text size – +

By Noah Bierman, Globe Staff

Leaks in Big Dig tunnel have been reduced from a few thousand to 650, according to a study presented today at the Massachusetts Turnpike Authority board meeting.

The remaining leaks should be plugged by next summer, said Robert R. Rooney, deputy secretary for public works, who headed a review of the tunnels initiated after a fatal ceiling collapse in July 2006.

"It's an ongoing, evolutionary thing, where you just keep peeling down the onion," Rooney said.

New leaks may emerge or be detected over time, but the number is expected to be in the dozens, not the hundreds, said Andrew E.N. Osborn, an engineer with Wiss, Janney, Elstner Associates Inc., the Illinois-based engineering and architectural firm that conducted the leak study.

The consultants said the tunnel system is safe in the short term, but warned that leaks would cause significant erosion if not plugged. The amount of water now being pumped out of the Big Dig is 25 percent of the accepted standard for leaks in tunnels. The contract with Bechtel/Parsons Brinckerhoff to build the Big Dig required that the tunnels have no leaks.

The Globe reported in July that nearly 2 million gallons of water was flowing each month through the Thomas P. O'Neill Jr. Tunnel, an 18 percent increase from last year. The leaks were mainly in the seam between the 1.5-mile tunnel's wall and roof.

The problem became public after a breach opened in the tunnel walls in September 2004, sending water gushing into the northbound lanes. The Turnpike Authority spends nearly $5 million a year for construction crews to plug leaks in the tunnel roof and walls.