Over their 50-year service, age and heavy traffic took a toll on the twin I-91 Rockingham Bridges. New England’s frigid winters led to six months of deicing agent applications annually, which corroded the reinforcing steel and spalled concrete. A greater concern, the bridges’ gusset plates were undersized, considered “fracture critical,” and lacked redundancy.

The Vermont Agency of Transportation (VTrans) faced a decision: temporarily extend the service life with a costly renovation or replace the bridges.

The new, $50 million I-91 Rockingham Bridges are the state’s first four-span spliced precast concrete girder structures. The new bridges - known locally as the "high bridges" - boast a 100-year lifespan and were constructed alongside public support. A boost to the local economy, the new precast segments were fabricated less than 100 miles from the site. The bridges are wider and safer, with two 12-foot travel lanes, a 4-foot shoulder and a 10-foot breakdown lane. Despite a 6-foot wider cross section, the team gained 8 feet of travel surface with advanced bridge barrier technology.

Constructed 130 feet over an environmentally critical river, the team repurposed the old substructure as temporary supports for the new bridge, maintained traffic throughout construction, and surmounted VTrans’ pier slenderness requirements. They used rolling roadblocks to deliver girders, picked in just 20 minutes. Late in design, realizing the girders were too tall for the route, the team modified the stirrup, which unintentionally also improved safety.

The I-91 Rockingham Bridges includes Vermont’s first four-span spliced precast concrete girder bridge. Using one-of-a-kind elements, some of Vermont’s largest precast segments, and massive cranes, the project team overcame a unique, unbalanced layout and challenging topography. The new, strikingly beautiful structure is nestled in one of America’s most picturesque environments and will play an integral role in people’s lives for decades to come.