The Reconstruction of Longfellow Bridge

Project Longfellow Bridge

Architect Rosales + Partners

When architect Miguel Rosales describes the restoration work performed on the Longfellow Bridge, he uses the word integrity a lot. His firm, Rosales + Partners, in collaboration with engineering firm STV and a task force of nearly 40 government and local agencies, helmed the $300 million-plus project completed in 2018. The arched steel bridge is a protected landmark that spans the Charles River, connecting Boston and Cambridge. The original structure was built between 1900 and 1907, and was ultimately named for poet Henry Wadsworth Longfellow, though it is perhaps better known among Bostonians as the “Salt and Pepper Bridge,” a moniker referencing its shaker-shaped towers.

For over a century, the bridge has been in continuous use and hadn’t been upgraded since the 1950s. The goals for this project included increasing its seismic capacity, improving its functionality, and preserving its historic architecture. The structure’s 2,132-foot length, its complex detailing, and its poor condition made it an expensive and laborious undertaking that took five years to complete.

Rosales + Partners was a natural fit to lead the charge, as they specialize in bridges—typically new construction but some restoration work, too. Here they were dealing with 11 open-spandrel steel arches, a 105-foot-wide deck, a substructure of granite masonry in the form of ten hollow piers and two abutments, and four Neoclassical granite towers—the restoration of which was a Herculean effort complicated by the fact that the bridge needed to remain operational while under construction. (The structure handles 28,000 vehicles and nearly 100,000 transit riders on average per day.) At one point, the trains had to be moved to one side in order to repair the center of the bridge, which was rusting on the underside.

Among the initial decisions was how to divide the space. The bridge has always been multimodal—initially with a trolly system, then the metro Red Line train, plus vehicles and pedestrians. But Rosales explains that the structure is fixed in terms of its width: “We could not expand it without destroying the architecture because of the towers at the edges.” He says there were many lengthy discussions about how to configure the layout that resulted in a tug of war between those who wanted it to carry more cars and those who wanted it to cater to pedestrians. Arguably, the train is the most important mode of transportation to consider because it carries the bulk of users. “Everybody wanted more space,” Rosales recalls. “With about 100 feet in width, every inch counted. One of the compromises we made was to remove one lane going into Cambridge in order to install wider sidewalks and bike lanes on half of the bridge, which resulted in an asymmetrical structure.”

Another challenge was to determine which architectural elements to restore and which to replicate and replace. Analysis determined that the granite towers, main steel arches, and most of the railings could be restored. The rest needed to be replaced. “Luckily, because this bridge has always been important, there was a lot of documentation and technical information about the structure, so we could find the details to replicate,” Rosales reports, pointing to the example of the tower windows, which are new but modeled on the original profiles and made of the same wood.

Many of the columns connecting to the deck were damaged or weakened and had to be replaced with a different style column. The originals were held together with massive rivets—an old welding technique no longer in common use. “We had to find people willing to do that work in Massachusetts, which added some costs and complications,” Rosales notes, “but I think it paid off.” He explains that the traditional rivet method was used on the exterior steelwork that is visible to the public. They also restored or replicated the original steel buckle plates used to support the bridge deck in certain locations along the river banks.

A significant portion of the restoration work lay with dismantling, cleaning, restoring, and re-erecting the 58-foot-tall towers, which had settled over time. Each tower is made of more than 500 Quincy granite blocks, which vary in size—some weighing up to three tons. As the towers were deconstructed, the blocks were numbered for accurate reassembly. Before rebuilding the towers, concrete liner walls were added to increase the bridge’s seismic capacity. “From one tower to another, the stones do not match,” says Rosales. “It was like putting together a puzzle. It took some time to get them all straight.”

He points to another factor complicating the towers’ restoration: Quincy granite is no longer available. To get an exact match, they had to use pieces from other bridges and regions. They also moved some of the granite that was in the middle of the bridge to rebuild visible sections. However, they still couldn’t source a sufficient supply so a granite veneer was used in some places, and one of the walls by the park on the Boston side had to be completely redone. “You can’t tell,” Rosales says. “It’s essentially the same material but the technique was different—they weren’t working with solid pieces.” Inside the towers, a new shell was built for additional strength against seismic loads.

The towers’ bronze doors were restored, too. Six were cleaned and repaired, and one needed to be replicated, as they had been removed and put into storage in the 1950s to protect them from vandalism, and one was lost in the process. Likewise, the cast-iron pedestrian railings were restored or replicated when missing.

Many of the lighting fixtures had also disappeared over the years; when they were replaced, it was without regard for the original style and location. During this project, the lamps on the towers were replicated and accurately placed. “The lighting is pretty close to what existed there 100 years ago,” says Rosales. “I think it’s very compatible with the structure.” For additional lighting on the roadway, new light posts were designed to resemble the catenary poles once used along the trolley lines. Rosales also calls attention to the never-before illuminated towers as a popular introduction, saying they now have a nighttime presence, which is enhanced by the blue lighting added beneath the arches. “For 100 years, the bridge was always dark at night. Now it comes to life.”

Other modernization efforts included: the widening of sidewalks, the addition of dedicated protected bicycle lanes, the installation of an open-rail barrier between the sidewalks and the vehicular lanes for improved safety, the modification of abutments and approaches for ADA compliance, and the clarifying of connections to the adjacent parkland.

The project received the highest recognition bestowed by the National Trust for Historic Preservation, which is not typically given to bridges but rather to important buildings. “It’s interesting because it is winning engineering and architecture awards as well as historic preservation awards,” Rosales notes. “It’s a combination of three different fields that came together for these results, of which I am very proud. I think it’s a fine example of how to restore a bridge to a high level of integrity, and I hope it serves as a model for other cities to show it is worth spending the money and time on a historic bridge, especially one with such significance and visual importance. It would have been very sad had it been demolished.”

2018 Lighting Design Award
Heritage Lighting

2019 Preservation Achievement Award
Boston Preservation Alliance

2019 Preservation Award
Massachusetts Historical Commission

2019 Richard H. Driehaus Foundation National Preservation Award
National Trust for Historic Preservation

2019 Public Works Project of the Year in Historical Restoration/Preservation
American Public Works Association

2020 Bulfinch Award
Institute of Classical Architecture & Art

Rosales + Partners also designed the $12.5 Frances Appleton Pedestrian Bridge as part of the Longfellow Bridge restoration project. It replaced the existing Boston Esplanade Pedestrian Bridge, which was built in the 1950s, and was thought to be too close to the vehicular bridge. Plus, the connection between the two structures was awkward. The new 230-foot-long steel span links Beacon Hill/Charles Circle to the Charles River Esplanade. It is named for Longfellow’s wife, Frances Appleton, in honor of their courtship during the 1840s when he would cross the Charles River from Cambridge to Beacon Hill to visit her.