All lanes of I-5 will be closed near Southwest 26th Avenue.

A major road closure is coming this weekend to Interstate 5 as crews work to repair an aging, worn-out bridge overpass in Southwest Portland.

Beginning Friday at 9 p.m., the Oregon Department of Transportation will close 4 miles of I-5 to replace a bridge overpass near Southwest 26th Avenue. The freeway is expected to reopen by 5 a.m. Monday.

ODOT spokesperson Don Hamilton said the bridge replacement is long overdue. It hasn’t undergone any major upgrades since it was built 65 years ago.

“At this age right now, it’s outlived its useful life, and it is not up to today’s seismic standards,” Hamilton said. “We need to make sure that we’re upgrading this, that we’re getting it ready for the 21st century.”

The project, which has been in the works for almost a year, also includes better lighting, bike lanes and sidewalks. Drivers are advised to use detour routes on Interstate 205, Interstate 405 and Highway 26.

According to Hamilton, this stretch of freeway typically sees about 100,000 cars a day and remains one of the busiest roads across the state.

“We realize this is going to be a real inconvenience, but we’re doing everything we can to try to make sure we’re keeping this system safe and ready for the future,” Hamilton said.

Additional single-lane, nighttime closures are also expected to take place over the next few months. Crews are hoping to have the project completed later this fall.

More information on the improvement project, as well as detours, are available here.