405 Freeway segment in Fountain Valley will close periodically through mid-April for widening project

Perhaps you’ve never thought of Slater Avenue as a trailblazer. But the thoroughfare’s bridge in Fountain Valley has taken the lead in the overhaul of the 405 Freeway.

Of the 18 Orange County bridges affected by the $1.9 billion freeway-widening project, Slater’s new span will debut first – likely within the next two years. That means Slater also paves the way, so to speak, for reconstruction and lane closures – periodically occurring overnight March 29 through about April 12.

Demolished in September, the span will be off-limits to traffic for at least a year as it undergoes renovation.

Freeway closures around the out-of-commission bridge will take place from 11 p.m. to 5 a.m. weekdays and 11 p.m. to 6 a.m. weekends, said Orange County Transportation Authority spokesman Eric Carpenter. No closures are planned for Saturday nights into Sunday mornings.

Northbound closures are underway until about April 10. The lanes are scheduled to remain open on Monday, April 1, and Tuesday, April 2. Southbound closures, anticipated for the nights of April 11 and April 12, will not overlap with those on the other side of the freeway.

Exact dates are tentative.

“The contractor makes changes to the schedule depending on progress and weather conditions as the project moves forward,” Carpenter said.

Over the next few months, drivers will notice the “falsework” stage of development.

“Falsework is the temporary steel and timber structures used to support construction of a bridge until it becomes self-supporting,” Carpenter said. The huge beams enable construction of the final concrete bridge.

Slater Avenue is the only bridge with falsework currently underway. “The same closures will be required to remove the falsework once bridge construction has been completed,” Carpenter said.

Next up for demolition is the Bolsa Avenue bridge in Westminster. Slated for April 6, it will require a full freeway closure overnight. During that time, work on Slater Avenue will be suspended.

Anticipating that traffic on the 405 will grow by 35 percent over the next two decades, OCTA will add two lanes to each side of the 16-mile stretch between Costa Mesa and the Los Angeles County line. The five-year project will result in two pay-to-use express lanes, which can be accessed at no charge by vehicles carrying multiple passengers.

For a list of upcoming closures and suggested detours, go to octa.net/405map.