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August 2018

Walsh Construction Completes Commonwealth Avenue Bridge Replacement

BOSTON - Walsh Construction has completed the replacement of the westbound portion of the Commonwealth Avenue Bridge. The $82-million project was completed in 15.5 days, July 28 through August 11. The project called for the replacement of the westbound superstructure, including the concrete deck and steel beams, that carries Commonwealth Avenue, inclusive of the MBTA Green Line over the I-90 Massachusetts Turnpike (Mass Pike) and a commuter rail line.

Walsh Construction replaced the eastbound portion in 2017 during a similar duration.

The Commonwealth Avenue Bridge is a major connector for commuters and public transit through Boston. Since its original construction in 1965, it has deteriorated and the steel beams have experienced corrosion in numerous locations.

The project began with the demolition of the existing deck to expose the steel beams for removal. The demolition of the existing deck on Spans One and Two began on Saturday, July 28, and the first existing steel beam was removed only a few hours later. Demolition operations for these spans were completed in 36 hours. Span Three was demolished later in the week, and staged closures on the Mass Pike and commuter line below were in place to allow crews to perform all operations safely.

To replace this structure using conventional methods would have taken four to five years. The Accelerated Bridge Construction techniques were chosen by MassDOT to eliminate major impacts to the Mass Pike and commuter rail under the bridge, as well as Commonwealth Avenue and the Green Line that runs through the center. In the end, the complete replacement of three bridge spans took a resounding 15.5 days.

The spans were pre-erected off-site to ensure proper fit-up of the steel girders and precast concrete deck panels. The deck panels were then tagged for their ultimate destinations, stored on trailers and transported to the construction site for just-in-time placement.

Walsh Construction crews worked in continuous shifts, 24 hours a day, during the intensive shutdown period. On average, 200 workers were on site during each shift.

The replacement of the westbound side of the bridge utilized three cranes to place 45 steel beams (that were up to 165 feet long and weighed 66 tons) and 214 prefabricated concrete deck panels (that weighed about 10,000 pounds each). The project included 680 cubic yards of concrete and 520 tons of hot mix asphalt. The project involved installing granite curbing, waterproofing the bridge deck, paving, putting in place traffic signals and completing utility and other work.

Walsh Construction achieved milestones across the project. Closures on the Mass Pike and the parallel commuter rail line under Commonwealth Avenue was also back in operation ahead of schedule, and the entire bridge replacement was completed on time.



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