Metro

State set to replace faulty nuts in Big Dig’s tunnels

A crew worked on a light fixture in the roof at the center of the entrance to the Thomas P. O’Neill Jr. Tunnel in Boston in 2011.

Aram Boghosian for the Globe/File 2011

A crew worked on a light fixture in the roof at the center of the entrance to the Thomas P. O’Neill Jr. Tunnel in Boston in 2011.

State transportation workers are set to replace hundreds of flawed nuts on light fixtures throughout the Big Dig’s tunnels after inspectors found a cracked one last month , a top highway administrator said Wednesday.

Officials with the Massachusetts Department of Transportation said that while no light fixtures were in danger of falling, the department would replace faulty nuts out of an abundance of caution.

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“If one nut is showing the slightest sign of deterioration, we’re removing that and replacing that nut on that system,” Highway Administrator Thomas Tinlin said during the monthly state transportation board meeting. “It just makes good sense.”

Officials did not have an estimate of how much the replacements would cost.

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Safety within the Big Dig’s tunnels has long been a concern. In 2011, a 110-pound light fixture in the Thomas P. O’Neill Jr. Tunnel crashed onto the roadway because of corroded supports. In 2006, a concrete ceiling panel crashed to the ground inside a Big Dig tunnel, killing a woman in a car.

Tinlin told board members that officials determined no imminent safety concern existed when they discovered the faulty nut, but officials did “not want to wait for something to break.”

“If we have learned anything in the past, it’s that the diligence that we’re showing is warranted,” he said.

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Tinlin said that after an inspector found a single cracked nut in the Ted Williams Tunnel in mid-September, MassDOT officials asked inspectors to pay more attention to light fixture nuts throughout the tunnel.

At that point, inspectors discovered 41 other nuts that needed replacing. The department then had inspectors check every nut on every light fixture in the Williams Tunnel, the Interstate 90 Connector, and the Interstate 93 tunnels.

Inspectors then embarked on a broader inspection of the roughly 5,000 light fixtures in the Williams Tunnel. After reviewing about 70 percent of the light fixtures, inspectors have identified 878 nuts for replacement.

Another 17,925 light fixtures are used in the Interstate 90 and Interstate 93 tunnels but only 14 percent have been inspected. Of those, nearly 50 nuts must be replaced.

The inspections in the Williams Tunnel will be complete by the end of this month, and the inspection of the Interstate 90 and Interstate 93 tunnels will be finished by the end of November.

The state has contacted federal officials to help identify why the nuts are flawed, according to Tinlin. He said some nuts have been in place for 25 years and could have been fractured when installed.

In other developments, transportation officials at the meeting revealed that the completion date of the Green Line extension appears likely to be pushed back again.

Officials do not have an estimate for when the work could be completed. But they acknowledged the project is unlikely to meet its latest timeline, which called for some stations to open by 2017.

On Wednesday, Transportation Secretary Stephanie Pollack told the board the next major phase of the project might not move forward until next spring — at the earliest. Construction on that phase was slated to begin this fall.

State officials, who said it is still possible the extension may be halted completely, will present their recommendations for the project at a Dec. 9 meeting.

“We don’t want to put additional Commonwealth dollars at risk until we’ve moved forward on the project,” Pollack said.

The project was threatened earlier this year when officials revealed the long-awaited extension to bring the Green Line to Medford and Somerville could cost about $1 billion more than expected.

The subject of T fares was also addressed Wednesday. The MBTA seems poised to tackle fare hikes in coming months, as officials presented information on how much the agency must subsidize every ride on subways, buses, commuter rail, and other modes of mass transportation.

The T’s chief administrator, Brian Shortsleeve, told board members the Massachusetts Bay Transportation Authority spent about $2.07 to subsidize each of the 395 million rides it gave during the 2015 budget year.

Among its modes of transit, the MBTA spends the least to subsidize subway riders: The T pitches in only about 61 cents for each ride. That figure does not include the Green Line, which is technically considered light rail. The T spends about $1.39 to subsidize each light rail ride.

The agency spends more to subsidize buses, paying about $2.86 for every ride. The number is even higher for commuter rail: It spends about $5.75 for every commuter rail ride.

The largest subsidy by far goes to customers who use the RIDE, which provides door-to-door service to riders with disabilities. For every ride, the MBTA spends $45.53.

Nicole Dungca can be reached at nicole.dungca@globe.com.
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