Wildlife crossing: Highway 101 closures to switch to all northbound lanes

Overnight closures on Highway 101 near Agoura Hills are expected to switch to northbound lanes later this week.

All lanes will be closed in one direction at a time as crews lift dozens of heavy concrete beams in place to form the skeleton of the Wallis Annenberg Wildlife Crossing. The southbound closures started April 15 and are expected to continue Monday and Tuesday nights.

Starting Wednesday, the work will move to the northbound side, according to the California Department of Transportation. The closures are expected to start shortly before midnight, or earlier depending on traffic conditions, Monday through Friday.

The highway will reopen by 5 a.m. weekday mornings and roughly 6 a.m. Saturdays.

Where can vehicles detour around Highway 101 closures?

Some lanes begin closing as early as 7 p.m. During the closure, drivers can get from Los Angeles to Ventura County via Highways 405, 118, 23 and the 101, Caltrans said.

Those who can't use other highways can detour from the 101 onto Agoura Road, the agency said. The detour runs between Chesebro and Liberty Canyon exits. The northbound 101 onramp at Liberty Canyon also may be closed during the northbound lane closures.

Plans call for installing 82 reinforced concrete girders stretching from the walls on either side of the freeway to middle support columns. The overnight closures are expected to take roughly two to three weeks in each direction.

How much will it cost to build the 101 crossing?

During construction, officials also have lowered the speed limit and narrowed lanes to accommodate work on a short stretch of the 101 near Liberty Canyon.

Construction started two years ago on the bridge over the 10-lane freeway, a barrier for mountain lions, mule deer and other wildlife in Ventura and Los Angeles counties. The 210-foot-long crossing may help save an isolated mountain lion population from extinction.

C. A. Rasmussen Inc., of Valencia, received a $23 million contract to complete the first phase of construction, which includes the bridge over the freeway. More than $100 million in a mix of public funds, private grants and donations have been raised to pay for costs, including designs, studies and construction. Caltrans officials say they hope to complete the crossing, expected to look like natural habitat, as early as late 2025.

Why build the Wallis Annenberg Wildlife Crossing?

The area near Liberty Canyon is one of few places left that has natural habitat on both sides of the 101. The land is also publicly owned and protected from development.

The National Park Service has found that mountain lions and other animals approach both sides of the freeway but few attempt to cross it. The agency has studied mountain lions in the area since 2002 to see how they're surviving in an increasingly urban area.

The small cougar population in the Santa Monicas Mountains is boxed in by development and highways, obstacles that have led to inbreeding, low genetic diversity and lions killing each other. Crossings can reduce collisions with wildlife but also add connections to other areas and reduce isolation, experts say.

Cheri Carlson covers the environment and county government for the Ventura County Star. Reach her at cheri.carlson@vcstar.com or 805-437-0260.

This article originally appeared on Ventura County Star: Wildlife crossing work to close Highway 101 northbound lanes