A work crew found another extensively corroded light fixture in a Big Dig tunnel last Thursday, state transportation officials said on Friday, five months after an identical 110-pound fixture came crashing down in the Tip O’Neill tunnel.
Workers driving through a ramp connecting Leverett Circle to the O’Neill Tunnel Thursday noticed a light was vibrating from a nearby jet fan and was askew. When they looked more closely, they found that five of the 10 clips that secured the light to the ceiling were corroded, leaving the light only partially secured.
Transportation Secretary Jeffrey B. Mullan said the corroded fixture discovered Thursday had been inspected in May as part of a systemwide review that found widespread corrosion in the Big Dig tunnels. But Mullan could not say why the corrosion on the Leverett Circle light fixture was not discovered during the earlier inspection.
“We’re working it. I don’t know. I don’t know exactly,’’ he said. “I know it was next to a jet fan. I’ve got my engineering team working on it right now.’’
Workers removed the corroded light fixture discovered Thursday and then reattached it using plastic straps, a remedy that has been used on many lights in the Big Dig’s tunnels since the light fixture collapse in February. Of the system’s 25,000 light fixtures, more than 9,000 have been reinforced with straps.
Mullan, whose department came under criticism for not telling the public about the fallen light fixture for more than a month, announced the latest findings yesterday, unprompted, to reporters who were inquiring about his decision to step down later this year. The Massachusetts Transportation Department also posted a full report about the situation online yesterday.
Earlier this week, Mullan suspended the Big Dig’s top engineer, Helmut Ernst, after Ernst told the Globe that he and his colleagues were trained not to leave a paper trail about safety issues in the tunnels for fear of litigation.
The incident report suggested that forced air from the jet fan may have caused the Leverett Circle light to vibrate more than normal. The report also suggested that the testing conducted in May, which involved prying loose the clips that connect light fixtures to the ceiling, may have weakened those clips. That type of testing was suspended later in the month “because of the potential for damage’’ to the clips, the incident report showed.