In the shadow of bridge B-16-281, Farhad Rastegari and I walked over to the Exit 29 off-ramp, where Tom Prendergast was in a boom lift on the back of his truck. He checked the bridge’s deck for rust, cracks, and other signs of distress, then lowered the boom a bit and began to tap the concrete embankment with a hammer, listening for hollow or “punky” sounds. Afterward, he maneuvered himself underneath the span, getting up close to a steel support beam. “It’s very critical to make sure it’s not deteriorated,” Rastegari said. “If it gets thinned out, then all of a sudden the bridge might buckle.”

Because bridges in Massachusetts are getting older, it takes longer to inspect them. An inspection that used to take six hours with paperwork can now take twice that long, and a bridge in bad shape can take three or four days. With a team inspecting 10 to 15 bridges a month, Rastegari said, he could use another four or five crews.

Prendergast lowered the boom lift. “How are the bearings?” Rastegari asked him.

“Good,” Prendergast replied. “Everything is weathered steel. We haven’t really seen much. A couple of hairline fractures.”

I asked about several patches of crumbling concrete I’d noticed in different sections of the bridge where the deck met the superstructure. They were a disturbing sight, with rusty steel poking through the concrete. Rastegari explained that directly above the areas in question were joints where sections of the deck came together. The sections were intentionally left unconnected to give them flexibility that prevents damage as the deck contracts and expands with New England’s weather extremes. When the bridge was built 30 years ago, the joints were outfitted with rubber caps to prevent corrosive salty slush from dripping through them and onto the superstructure below.

Though the damage looked bad to my untrained eye, Rastegari said it didn’t pose any structural problem—yet. But eventually, he acknowledged, it was the kind of thing that could become a concern.

Prendergast agreed that leaking joints were the cause. “My guess is, 1970 vintage,” he said. “The caps have probably never been replaced.”