A seismic retrofit project to help Interstate 5 overpasses withstand future earthquakes gets underway with ramp and lane closures starting Monday night. The project will continue at four locations in Federal Way into summer 2015.

The project will start with the closure of the southbound I-5 ramp to eastbound State Route 18 from 8 p.m. Monday, March 24 to 5 a.m. Tuesday, March 25. During the closure, contractor crews working for the Washington State Department of Transportation will put temporary striping in place.

Wednesday, March 26, contractor crews will close the left lane of eastbound SR 18 under I-5 from 8 p.m. to 5 a.m. for barrier work. The westbound lanes of SR 18 will also be restriped and temporary barrier will be placed on their left side as soon as weather permits.

Thursday night, March 27, excavation will begin in the SR 18 median.

The seismic retrofit of the bridges at South 336th Street also will begin this week.

The project will retrofit I-5 overpasses at four locations in Federal Way – SR 18, South 336th Street, Military Road South and South 288th Street. There will be sidewalk, shoulder and lane closures on these streets during the project. Work will be done during the day and at night. All work will take place under I-5, so the freeway will not be affected.

Work will include installing girder stops, bolsters and steel column jackets at SR 18 and South 288th Street. Steel jackets will be installed at South 336th Street and Military Road South.

This project is part of WSDOT’s seismic retrofit program, designed to help keep bridges and overpasses standing after a major earthquake. Since the program began in 1991, WSDOT has done complete or partial retrofits on more than 400 bridges.