Work on Magnolia Street bridge to cause partial closure of 405 Freeway

405 closure map
All southbound lanes of the 405 Freeway between Magnolia Street and Warner Avenue are scheduled to be closed overnight Monday for work on the new Magnolia Street bridge.
(Courtesy of Orange County Transportation Authority)

Work on the new Magnolia Street bridge over the 405 Freeway in Fountain Valley will cause a full closure of part of the southbound freeway overnight Monday.

Crews are scheduled to remove steel falsework, or temporary framework structures used in construction. All southbound lanes of the 405 between Magnolia and Warner Avenue are scheduled to be closed between 11 p.m. Monday and 5 a.m. Tuesday, according to the Orange County Transportation Authority. Detours will be in effect.

The 405 off-ramp to Magnolia Street is set to close at 10 p.m. Tuesday, and the on-ramp from Magnolia is scheduled to close at 10 p.m. Feb. 23. Both are expected to reopen March 24.

The Magnolia Street bridge is being rebuilt in two stages — one half at a time — allowing it to remain open to traffic during construction. The work started in December 2018 with a completion schedule of 18 to 24 months. The bridge is being reconstructed to increase the number of traffic lanes from four to six and have bike lanes and sidewalks in both directions.


The project is part of a $1.9-billion plan to widen the 405 between the 73 Freeway in Costa Mesa and the 605 Freeway near Rossmoor. Once the larger project is completed in 2023, both directions of the 16-mile stretch of the freeway will have an additional general-purpose lane and a new “express” toll lane, according to the OCTA. The existing carpool lane in each direction will be converted to an express lane.

For more information, email or call (888) 400-8994.