Each enamel-coated metal panel measures 4ft by 9ft (1.2m by 2.7m) and weighs approximately 100lbs (45kg). 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, MassDOT told local press.
The inspection of the Sumner tunnel was triggered by findings inside the Callahan tunnel, which runs parallel to it. The Callahan was shut down on 21 December after a single panel fell that day. There are 2,800 panels in the Callahan. No commuters were injured in that incident.
The weakened bolting systems in the Sumner were not found in clusters but throughout the tunnel. More advanced deterioration was seen in the Callahan, with rusting extending to the framework that holds the panels in place. Replacement of the Callahan tunnel is expected to start later this year and is estimated to cost USD 10M to USD 12M and 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.
