Work to replace a bridge over Interstate 495 in Boxborough, Massachusetts, recently hit a major milestone as the first steel girders were placed.
The four girders will help form the foundation for a bridge to carry Route 111/Massachusetts Avenue over I-495 in the northeast part of the state. Though 11 girders were to be used per the original design, the use of high-performance steel means only nine girders will be required for the full structure.
The $24.2 million contract for the bridge’s replacement, which is designed for a 75-year service life, was awarded in January 2024 to MAS Building & Bridge out of Norfolk, Massachusetts.
The previous structure, which recently reached 60 years of service life, first showed signs of advanced deterioration and deficiencies in April 2017. Emergency substructure repairs were conducted in October 2018, and the bridge has since been deemed structurally deficient.
The girders were placed over the course of several nights to avoid danger to live traffic below the bridge. Traffic was reduced in the evenings to a single lane over the remaining half of the existing bridge. Rolling roadblocks were deployed to keep drivers away from the work zone.
One pier from the original construction of I-495 is currently helping stabilize the new bridge’s girders and will later be removed when the concrete at the base of each column is chipped away, and the weakened structure is toppled into the median.
Goals for the new 282-foot-long bridge include reducing maintenance requirements, improving vertical and horizontal clearance, allowing for a future widening of I-495 and providing a shared use path for pedestrians and cyclists.
The finished structure will feature two 12-foot travel lanes in each direction with 4-foot-wide shoulders. Major construction is estimated to finish in Fall 2026.
The foundations for the first portion of the new bridge were completed at the end of June and feature enhanced protection against vehicle crashes.
Upcoming work will include placing utilities onto the new bridge, followed by starting deck installation in the beginning of August. Work remains on schedule to move traffic to the first half of the new bridge in Spring 2026.
