• Completed Clayton Street Bridge
  • The new superstructure is assembled in an adjacent yard.
  • Self-propelled modular transport units wheeled the new structure into place.
  • The old Clayton Street Bridge.
Bridge replacement in a single weekend

Founded in 1630, Dorchester is the largest and most diverse neighborhood in Boston, Massachusetts, and has 15 rapid transit and rail systems. One such system, the Ashmont Red Line, runs over Clayton Street Bridge.

Challenge
Originally constructed in 1911 and last repaired in 1926, the Clayton Street Bridge was a deteriorating three-span superstructure with dangerously low clearance and hazardous steel bents along the narrow sidewalks. The bridge spanned a busy street that trucks often used as a shortcut. Replacing the Clayton Street Bridge by conventional techniques could have taken months, affecting street and train traffic and causing significant commuters disruption and delays.

Solution
As the project design consultant, Louis Berger provided engineering and design services for the replacement of the 104-year-old bridge. This was the first Massachusetts Bay Transportation Authority (MBTA) transit bridge to be replaced using accelerated bridge construction techniques, which increase safety and efficiency of bridge replacements while decreasing the impact on traffic, residents and commuters.

To streamline the process and avoid traction power, signal and communication service interruptions, a temporary structure was constructed in advance to carry the utilities previously routed on the bridge.

In less than 12 hours, the outdated structure was demolished to make room for the new bridge, which had been assembled onsite in an adjacent yard. Self-propelled modular transport units wheeled the new single-span, 500,000 pound structure into place. Once the steel beams touched down on the newly replaced bearings, MBTA crews worked through the night to restore the tracks in time for the next morning’s commute.

Construction was successfully completed in just 56 hours. By using accelerated bridge construction techniques, Louis Berger cut construction time by 10 months, and the state saved approximately $2 million. The new design strengthened the existing substructure and increased the bridge’s clearance to prevent truck collisions.