A key Dot Ave bridge that links Dorchester and South Boston that closed last June will remain shut down through next fall as work continues to replace the aging MBTA-owned span that carries people and cars over Red Line and commuter rail tracks below it.

The $34.5 million project involves a full replacement of the bridge and the Red Line tunnel roof and the rehabilitation of a retaining wall on adjacent Von Hillern Street.

The bridge was supposed to re-open to cars, bikes and people on Nov. 7, but the MBTA announced on Oct. 28 that the closure will stay in place through fall 2023 “at the request of the City of Boston.”

A statement by the T said that “this extension allows for acceleration of work by the Boston Water & Sewer Commission.”

This delay comes after the T had already extended the closure from August into this month after workers found “obstructions” that delayed the job, according to an MBTA spokesman.

The existing bridge is slated to be demolished and replaced with new steel girders and concrete bridge deck, T planners say.

Go to MBTA.com/DotAveBridge for more details.