Cracks Found in Support Beam of Boston’s Tobin Bridge

Cracks in a support beam of Boston’s Tobin Bridge have officials scrambling to find a fix. In the meantime, all vehicles over 10,000 lb, including commercial trucks and buses, are banned from traveling over the structure, according to Massachusetts Port Authority officials at a press conference late Friday afternoon.

Several cracks were found in one of the support beams of the structure Friday during a regular inspection. The ban is expected to last through the weekend as temporary, emergency repairs are made. A more permanent fix will take much longer.

Officials are saying the cracks in the 2-ft by 8-ft beam do not pose an immediate danger.

Massport’s Director of Capital Programs Sam Sleiman said in the press briefing that although the cracks were found and traffic diverted, the bridge is still safe.

“The bridge is safe. The bridge is structurally sound,” he said. “We would not have allowed any traffic over it if we did not feel the bridge was sound. This is just a precaution.”

Part of the temporary fix includes wrapping the beam with high-strength cables. A permanent repair is expected to take at least a week.

The cracks were found during a foot-by-foot inspection of the bridge, conducted every four years. While the cause of the cracks is still under investigation, officials say corrosion is suspected.

In August, the 57-year-old span of the bridge gave boaters a reason to panic when debris fell from the bridge, breaking windshields and causing other damage to boats and vehicles below at the Chelsea Yacht Club.

This wasn’t the first time; over the years flakes of rust the size of about a quarter have continuously fallen on the yacht club.

At the time, Massport officials said the falling debris did not affect the structural integrity of the bridge. As an emergency measure at the time, Massport officials stretched a net beneath the bridge to catch chunks of falling concrete and metal.

Maintained by Massport, the Tobin was erected in 1948-49 and opened to traffic in 1950. The bridge connects the Charlestown section of Boston with Chelsea and provides three travel lanes northbound on its lower level and three lanes southbound on the upper level. The roadway is 36 ft wide. According to the Massport website, the main structure of the Tobin is a three-span, cantilevered truss 1,525 ft in length. Its center span is 800 ft and the maximum truss height is 115 ft. It provides a navigable waterway opening 700 ft wide by 135 ft high. A smaller, simply supported warren truss spans the Little Mystic channel. It reaches a maximum truss height of 65 ft and is 439 ft long. Its navigable waterway opening measures 340 ft wide by 100 ft high.

In the wake of this summer’s highway bridge collapse in Minnesota, and last year’s fatality when a ceiling panel collapsed in one of Boston’s Big Dig tunnels last summer, officials are working hard to ensure infrastructure in and around the city is safe.