Metro will embark on a series of renovations to a 1970s-era bridge spanning the Potomac River and nearby tunnels next year, resulting in an “extended shutdown” of Yellow Line service between L’Enfant Plaza and the Pentagon.

The project is slated to take place in fall 2022 and be completed by the end of the year, but details are still up in the air. The Washington Metropolitan Area Transit Authority (WMATA) is in the process of securing permits for the project, so it is unclear when the outage will happen or exactly how long it will last, according to Andrew Off, an executive vice president at WMATA.

“This is one of the most complex projects we have undertaken,” Off said during a Metro committee meeting Thursday where officials were given an update on upcoming renovations.

The rehabilitation will include remediating “excessive wear and corrosion,” replacing pipe, and replacing bearings that support the tunnel, as well as updating the bridge’s fire suppression system.

In addition to the Yellow Line outages, a number of other closures are already scheduled for next year.

The Red Line will single track on six weekends in early 2022 between Silver spring and Forest Glen for a project to address leaking. The Orange Line will shut down from Minnesota Avenue to New Carrollton over the summer for station renovations. And the Potomac Yard station is also scheduled to close for two weeks in the late summer or early fall.