Dead bridges: How modular viaducts are keeping the I-91 open in Massachusetts

J.F. White Contracting is replacing four functionally obsolete bridges built in the 1960s. Acrow’s 500-foot-long detour bridge is seen here crossing over Route 5 and a railway (Courtesy of Acrow)
New Jersey-headquartered bridge maker Acrow has supplied two modular steel bridges to keep traffic flowing during a major bridge replacement project on the busy Interstate 91 (I-91) in Northampton, Massachusetts.

J.F. White Contracting is replacing four functionally obsolete, structurally deficient bridges built in the 1960s.

One pair carries north- and south-bound traffic over Route 5 and a railway, and another pair similarly crosses over Hockanum Road a little to the north.

Because maintaining the route is so critical, J.F. White bought two Acrow bridges to keep heavy traffic flowing during the multi-year project.

It installed the bridges in the median to give two open lanes at each site while the permanent bridges are replaced.

Acrow says such detour bridges are becoming more popular with project owners.

The long and short of it

The first bridge over Route 5 and the tracks consists of five spans with a total length of 500 feet. It’s held up by eight Acrow towers ranging in height from 29 to 38 feet.

The second one over Hockanum Road is a 140-foot-long clear span.

Both bridges are 30 feet wide between curbs and have asphalt overlay deck surfaces.

Engineers installed the longer bridge with a full cantilever launch method and the shorter one by crane-assisted launch.

Tight squeeze

Acrow said the limited space between its bridges and the defunct ones proved a challenge.

Temporary support towers on skewed piers helped avoid roads, tracks, and utilities below.

Northbound traffic on the I-91 was shifted to the temporary bridges in May 2022.

When the two permanent northbound bridges are built, southbound traffic will be rerouted over Acrow’s bridges during construction of the permanent southbound structures.

All done by 2025

The four new bridges are scheduled to be finished in 2025.

“Project owners and contractors are increasingly selecting detour bridges over other re-routing methods during construction projects,” said Nick Rotondo, Acrow’s New England business development manager.

“In addition to making work sites safer, modular detour bridging helps minimize work zone impact on motorists and local businesses.”

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