The MBTA’s historic Lechmere Viaduct carries Green Line trains from Lechmere in East Cambridge across the Charles River into downtown Boston and is made up of a 12-span concrete arch bridge constructed in 1910 by the Boston Elevated Railway Company. Recently, the MBTA determined the bridge’s arches were structurally inadequate and selected VHB as lead designer for the rehabilitation project.
The Lechmere Rehabilitation project will strengthen the structure of the 110-year-old viaduct to handle heavier loads and increased train frequency while also preserving its historic facade. Work includes the complete reconstruction of track, signals, and traction power on the viaduct. These upgrades will allow more trains to pass over the bridge, ultimately serving a completely new Lechmere Station and the new stations constructed as part of the Green Line Extension from the line’s current termination point further west of Boston to Medford.
With the viaduct listed in the National Register of Historic Places (National Register) as a contributing resource within the Charles River Basin Historic District and individually eligible for listing in the National Register, VHB is responsible for coordinating with the Section 106 parties. Efforts have included finding a concrete repair material to match the color and texture of the historic structure’s concrete, a character defining feature. This process required striking a balance between today’s aesthetic material capabilities and producing repairs that were structurally sound. The project also included restoring a cast-in-place concrete structure from 1910, with all its inherent imperfections, and installing uniform precast elements.
The design includes technologies such as Carbon Fiber Reinforcement Polymers (CFRP) wrap for strengthening floor beams and arches marrying historic details and constraints with current engineering practices.
The Lechmere Viaduct Rehabilitation Project is one of 15 projects that make up the overall Green Line Transformation Program. Five of the projects have been completed with the remaining 10 in progress. Green Line Transformation (GLT) projects represent four levels of transformation: Safety and State of Good Repair; Accessibility; Legacy Car Replacement; and Capacity. Each level aims to improve reliability and the overall quality of service for all riders and communities served by the Green Line.
To learn more about the Green Line – Lechmere Viaduct Rehabilitation or VHB, please contact Project Manager Kristofer Kretsch.