All Virginia Railway Express trains to Union Station are stopping short at L'Enfant through Friday, Oct. 23, after Amtrak shut down the First Street Tunnel for a nine-day infrastructure overhaul.

The closure, which began after the last southbound train left Union Station on Oct. 16, is blocking every VRE and Amtrak train traveling between D.C. and Virginia. Both VRE's Fredericksburg and Manassas lines are running modified schedules, with northbound morning trains ending at L'Enfant and southbound afternoon trains departing from there, according to VRE's modified schedule. The disruption affects commuters across Fairfax County and Northern Virginia.

Riders who need Union Station must transfer to Metro or find alternate transportation from L'Enfant. VRE said all single-ride and multi-ride tickets are accepted on the modified service.

The project, which Amtrak calls "Pause for Progress," targets a junction called A-Interlocking, where multiple station tracks funnel into the two tracks that continue into Virginia. Crews are replacing two double-slip switches and a rail crossing known as a diamond, installing new electric switch machines, replacing ballast beneath the tracks and fixing drainage issues, WTOP News reported.

The existing switches are beyond their service life and require a 10-mph speed restriction, according to an Amtrak press release. Amtrak said the confined tunnel environment makes phased construction impractical, so a full shutdown was necessary.

"The track switches are beyond their useful life, so it's important that we take the time … upgrade this critical infrastructure so that we can have better service for the long term," Beth Toll, Amtrak's senior public relations manager, told 7News.

Amtrak service heading north to New York and Baltimore is unaffected. Southbound Amtrak service is sharply reduced. Amtrak Virginia is running one daily round trip between Norfolk and Alexandria and one between Roanoke and Alexandria, down from two each. Three daily round-trip bus bridges connect Alexandria and Union Station, timed to meet trains.

Karina Romero, communications manager at the Virginia Passenger Rail Authority (VPRA), told 7News the agency is running reduced service south of Alexandria. Riders heading to Alexandria can also walk to the nearby King Street-Old Town Metro station for Blue and Yellow Line trains into D.C.

Amtrak crews are working around the clock. Greg Michalski, Amtrak's deputy chief of production construction, told WTOP in August that the components "have just reached their useful life span" and are "at the point of a complete replacement."

Service is scheduled to resume Monday morning, Oct. 26. VRE riders can review the full modified schedule at VRE's website.