LYNN — Commercial Street will be shut down to traffic for four weekends next year while the street’s commuter-rail bridge is being replaced.
For two of those weekends, train service will be shut down as well on the Newburyport/Rockport line, for which the bridge carries service, according to Vanasse Hangen Brustlin, Inc., (VHB), the engineering and design firm that has been contracted by the Massachusetts Bay Transportation Authority for the project.
Representatives from the MBTA and VHB outlined the transportation agency’s plan to replace the 107-year-old Commercial Street commuter-rail bridge — slated to begin in the spring of 2021 — during a brief virtual meeting on Wednesday night.
Originally built in 1913, the bridge is reaching the end of its useful lifespan, which is why it has been tapped for replacement, according to MBTA Project Manager Mike Ryan.
“This existing bridge is in poor condition,” said Andrew Burkholder, senior engineer for VHB. “It’s outlived its useful life. (This will) replace it with one that’s resilient and has a 75-year useful life.”
The Commercial Street bridge carries commuter rail service for the Newburyport/Rockport line over Commercial Street in Lynn between the River Works and Lynn Station.
The existing steel bridge is being replaced as part of the MBTA’s reliability and modernization program. Five other commuter rail bridges have also been selected for replacement, with construction on all six expected to be completed by August 2022.
Burkholder said the bridge replacement project aims to continue to provide safe transportation for T riders and the public, and maintain and improve the state of good repair of MBTA infrastructure.
In Lynn, work will include a complete bridge replacement, which will include raising the track profile by 12 inches to accommodate the ballasted track structure and maintain vertical clearance, Burkholder said.
A total of 14 feet, six inches of vertical clearance will be provided under the new steel bridge, which will support two tracks, but allow for the potential of future expansion, Burkholder said.
The current bridge was originally a four-track structure, but only two tracks remain active, Burkholder said.
“This bridge will be designed to accommodate future expansion to the south,” said Burkholder. “New tracks can be added to the south side of the bridge without having to reconstruct this structure.”
Partial demolition of the existing bridge is scheduled for next spring, with construction of the new structure scheduled to begin in the summer of 2021. The new bridge will be moved into place next fall and work will wrap up in the spring of 2022 with a site cleanup, according to the presentation.
Detours have been planned for Pleasant Street, Neptune Boulevard and Blossom Street, among other areas, during the four weekends Commercial Street will be shut down.
Only one person, Stefan Wuensch, participated in the public comment portion of the evening. He raised several questions, including whether the placement of the new bridge was designed to allow enough space for the potential Blue Line extension, and if there would be a track speed limit restriction on the bridge during construction.
Ryan said the bridge design would not preclude the potential extension of the Blue Line. And Penfield fielded Wuensch’s second question, saying that there would be times where the 60 mph speed limit would be reduced for trains, but that timeline has not been determined.
The Lynn bridge and five others, including ones in Lawrence and Melrose, were built in the early 20th century and are slated to be replaced under a $91 million contract intended to reduce design and construction time and increase accountability as the projects unfold.
The MBTA is also planning design and construction work in the Market/Broad streets commuter rail garage. Design work is underway and construction is scheduled to begin in late 2021 with the work taking three to four years.
