Caltrans is preparing to break ground on a massive wildlife crossing that will span 10 lanes across the busy 101 Freeway in Western Los Angeles County. The roughly $90-million Wallis Annenberg Wildlife Crossing is being built to protect and reconnect native animals that have been cutoff by the modern highway.

The public-private partnership project is the result of 20 years of study by the National Park Service, which found roads and development are not only deadly for animals trying to cross, but have also created islands of habitat that can genetically isolate wildlife such as mountain lions, bobcats to birds and lizards.

“As the largest wildlife crossing of its kind in the world, it will provide lifesaving habitat connectivity to a broad array of animals for decades to come,” said Wade Crowfoot, California Secretary for Natural Resources, in a news release.

Caltrans is the project owner, with the National Wildlife Federation serving as a key fundraising partner. Caltrans says a contractor has been selected and will be named when the contract is finalized in the next couple weeks. Chicago-based Living Habitats LLC is leading the design.

The project, which breaks ground April 22, will span 12 acres. The crossing will be 210 ft long and 174 wide, providing about an acre of vegetative space with up to 4 ft of soil and 5,000 plants atop the freeway. The remaining 11 project acres will include approach slopes coming from the nearby hills on the north and south side of the bridge. This area will be landscaped with about 50,000 native plants.

“The crossing is a giant green roof on steroids,” says Robert Rock, Living Habitats Principal & COO. “We are taking this green fabric and stretching it across the freeway and connecting it to both sides and what we are effectively doing is sticking together an ecosystem across the freeway.”

Rock says one of the most fascinating challenges his team faced was coordinating regular meetings with various federal, state, private and NGO agencies during a pandemic.

“Having to be remote and digital as opposed to being able to sit down and sketch things out with people, forced us to find new ways to collaborate and design,” he says. “And to be able to move the needle forward on a project this novel in terms of the structure and the project team, while also being impacted by the pandemic, is a testament to the level of dialogue we had.”

To minimize disruption to the freeway while the crossing is constructed, the contractor will utilize pre-fabrication methodology rather than cast-in-place, says Sheik Moinuddin, Caltrans project manager. “Prefabricated spans will be brought in to build the bridge and this may save about four months in construction time compared to the traditional construction technique,” he says.

Moinuddin says the biggest challenge the project is facing is relocating existing utility lines that run along a road directly next to the 101 Freeway. There is a municipal water district trunk line and Southern California Edison joint poles with transmission, distribution, and communication lines for SCE, Spectrum and Verizon.

“In order to reach the wildlife crossing elevation, Vendell Road will be backfilled, which puts these utilities in conflict,” says Sean Silos, Caltrans transportation civil engineer. “Various relocation alternatives were developed with the utility owners and the project team, and the undergrounding of overhead utilities and relocation of the waterline within a utility tunnel was selected as the preferred alternative.”

Caltrans says this alternative, which will take about five months to complete, addresses the challenges and maintains the ability for utility owners to access their facilities without disrupting the wildlife crossing or the regenerative landscaping area east of the overcrossing. “This was a major sticking point to maintain functionality of the wildlife crossing without creating maintenance and operational challenges for utility owners,” says Silos.

Relocating the utilities also avoids impacting multiple historic oak trees, and “creates a positive project aesthetic as an overhead to overhead relocation would require excessively large transmission poles that would go over the wildlife crossing. These poles are also long lead procurement items that would negatively affect the project schedule,” says Silos.

The utility tunnel design will be completed in the second phase of the two-phase project. The interior dimensions of the tunnel are 16.5 ft high (minimum vertical clearance for equipment) and 28.5 ft wide, which is determined by the necessary offsets of the newly relocated underground utilities.

When complete in mid-2025, the project will have used approximately 5,410 cu-yds of concrete and 784 tons of rebar to construct the crossing and about 6,000 cu-yds of soil media (not dirt) on top of the bridge.