Bridging the Past to the Present: The Story of the Carlton Street Footbridge
Andre Martecchini, PE, Senior Project Manager, Kleinfelder
Conceived as a gateway entry to the Emerald Necklace parks by Fredrick Law Olmsted and designed by Brookline’s first Town Engineer, Alexis Henry French, the Carlton Street Footbridge was erected in 1894. The pedestrian bridge, an elaborate yet practical steel Pratt truss structure, spanned 70 feet over the then Boston and Albany Railroad, today the Massachusetts Bay Transportation Authority’s (MBTA) Green Line, D-Branch. Due to deferred maintenance, the bridge was closed in 1976 for safety reasons. Ongoing deterioration presented potential safety hazards to the MBTA tracks and trains passing under the bridge, and the bridge became a liability to the Town of Brookline. After a feasibility study and careful consideration, the Town chose to restore the bridge.
Existing Carlton Street Footbridge, closed in 1976
The challenge of this restoration project was to provide a universally accessible, ADA/MAAB-compliant bridge, which would accommodate bicycle traffic and furnish new surface lighting, constructed safely above an active MBTA track within a nationally recognized historic landscape. The bridge also needed to be raised to provide additional clearance above the MBTA tracks. The design solution, which was also the most economical option, was to lift and remove the entire bridge structure from over the tracks and transport it by truck to an offsite location for repair, restoration, and painting. The deteriorated trusses were transported to Rhode Island, where all repairs and painting were completed. While the structure was being restored in Rhode Island, construction of new foundations and the new accessible ramps took place on-site in Brookline, without interrupting Green Line operations.
Lifting and removal of the existing bridge for
repair, restoration, and repainting.
After the trusses and stairs were restored and painted, they were reassembled, transported back to Brookline, and lifted into place onto the new foundations. The resetting of the main span was completed in one lift that included the fully assembled trusses, floor beams, and timber stringers. As the restored structure was stronger, it was able to be lifted without spreader bars, which greatly reduced the lifting height over the trees. The stair trusses were transported back to Brookline later and set in place by the contractor as their restoration and repainting was completed. After resetting the bridge, a new naturally rot and fire-resistant Ipe timber deck was installed on the main trusses and stairs, replicating the historic timber decking. Slip-resistant ADA-compliant aluminum grating was installed on the new accessible ramps and anti-missile barriers, railings, lighting, and other bridge appurtenances were also installed, preparing this historic structure for modern-day use.
View of the reconstructed footbridge looking north
While the phasing of the restoration was technically difficult, the project also presented a challenge in disassembling the bridge trusses to replace corroded steel components and then reassembling the bridge. While the entirety of the bottom chords and all tension diagonals required replacement with new steel components, there was a concerted effort to maintain and repair as much of the original steel as possible. All replacement steel was sized to match or replicate the original design and was fitted with the original steel to preserve the historic aesthetics of the structure.
Reconstructed Carlton Street Footbridge seen from Riverway Park
A community group of more than 200 individuals followed the restoration process and applauded Kleinfelder’s efforts when the bridge reopened to pedestrian traffic on August 11, 2023.