State transportation workers found 26 loose wall panels inside the Sumner Tunnel during an inspection late Sunday night into Monday morning and removed them, after an examination last week in the Callahan Tunnel found 121 loose panels.
“Overall, the condition of the wall panels in the Sumner is much better than what we found in the Callahan,’’ said Frank DePaola, highway administrator for the state Department of Transportation, during a press conference at the department’s headquarters in downtown Boston Monday.
Each enamel-coated metal panel measures 4 feet by 9 feet and weighs approximately 100 pounds. About three dozen workers performed pull tests on all 2,400 panels lining the Sumner and found that 26 were loose because the stainless-steel bolted connections holding them in place were corroded, DePaola said.
The inspection of the Sumner, which lasted from 9 p.m. Sunday night until 1 a.m. Monday, was triggered by findings inside the Callahan, which runs parallel to it. The Callahan was shut down Dec. 21 as an emergency precaution after a single panel fell at 6 p.m. that day. There are 2,800 panels in the Callahan. No commuters were injured in that incident.
Annual inspections of all tunnels were prompted by a 2006 ceiling-tile collapse in the connector that links the Ted Williams Tunnel with other sections of the Big Dig, killing grandmother Milena Del Valle.
The weakened bolting systems in the Sumner were not found in clusters but throughout the milelong tunnel. More advanced deterioration was seen in the Callahan, with rusting extending to the framework that holds the panels in place, officials said.
Several factors cause the degradation in tunnels, including washing, diesel exhaust, brake dust, underground seepage, and grime, officials say. The panels are decorative and provide a reflective surface to distribute the lighting better and are easier to clean than the concrete walls they cover.
The department is ordering replacement materials for the Sumner, with repairs to come in weeks. Work in the Callahan will take longer, perhaps a year, DePaola said. The Callahan tunnel was renovated in 1990, and the Sumner several years later, he said.
“We are still advancing our plans to do a full replacement of the wall system in the Callahan Tunnel,” DePaola said. A March inspection is planned in that tunnel. The full replacement will start next winter, he said. That estimated $10 million to $12 million project will also include resurfacing the two lanes of the Callahan, which carries eastbound traffic from downtown Boston and Interstate 93 toward East Boston and Logan International Airport. It runs parallel to the older, westbound Sumner Tunnel.
Designers are looking to replace the existing fastening system used in both tunnels with one that would hold up better under the elements and are also looking into using lighter fiberglass slats.
Along with the tunnel system, the state has hundreds of aging bridges, some over 100 years old, and maintenance on many of those structures has been deferred for decades.
“We want to bring everything up to a state of good repair for the Commonwealth and for the citizens that use our transportation network,” said DePaola. “We are filing a bill with the Legislature in the next two weeks which will propose the amount of funding that we think over the next 10-year period we need to address a lot of the outstanding infrastructure investments that we need to do.”
That $14 billion price tag for the state’s infrastructure investments would be financed by a transportation bond, he said.