California Construction News staff writer
The Wallis Annenberg Wildlife Crossing, set to become the largest wildlife crossing in the world, reached a significant milestone as crews began placing the first layers of soil over the bridge structure. This crucial step, which will cover nearly an acre of the crossing, is a key part of a groundbreaking project aimed at reconnecting wildlife with their natural habitats and enhancing the safety of local highways.
Located above the U.S. Highway 101 in Agoura Hills, the crossing will span ten lanes of busy freeway, providing a vital pathway for local wildlife such as mountain lions, deer, bobcats, bats, desert cottontails, and monarch butterflies. The project will require approximately 6,000 cubic yards of soil, and the full placement process will take several weeks to complete.
Construction began in 2022, and the work is scheduled to be completed in 2026. This project represents a significant step towards wildlife conservation and habitat connectivity in the region, and D.H. Charles Engineering, Inc. is grateful for the opportunity to collaborate with bridge contractor C.A. Rasmussen, Inc. to overcome the structural and construction engineering challenges presented in building this wildlife crossing.
The wildlife crossing is designed to restore an ecological corridor that has been disrupted by urban development and highways. This vital project will help ensure that local wildlife can safely move through their habitat, reducing the risk of vehicle-wildlife collisions—a significant safety concern on highways like the U.S. 101.
D.H. Charles Engineering, Inc. was involved with multiple lines of work through this project’s construction sequence. From the ground up, our engineers were tasked to design rebar cage stability bracing for the new column reinforcement, concrete wall formwork and wind bracing for bridge abutment structures, and falsework/formwork design for new pier cap, bridge overhang, and other concrete support structures. One of the greatest challenges this project presented was the temporary shoring required to carry new precast bridge girders over the U.S. Highway 101.
The engineering that went into the temporary bridge shoring design was under the microscope as the heightened sensitivity for public safety was felt as the days edged closer to setting the girders and finally building the superstructure of the bridge. D.H. Charles Engineering, Inc. worked intimately with Caltrans officials to provide a design that was safe and tested by many years of both private and public falsework experience.
The temporary bridge girder shoring was constructed using structural steel beams to provide direct support for the new precast girders and timber columns and cross bracing to provide vertical support and stability. A challenge during the design phase of the temporary shoring was the limited space that was offered to the bridge contractor. Tucked neatly between the new abutment walls and the U.S. Highway 101, the limited width created the need for slender falsework towers only 4-feet wide and up to 25-feet tall at the North end of the bridge. Timber cross bracing and foundation structures needed to be designed to not only resist lateral seismic and wind demands per Caltrans standards, but also overturning effects from these same loads to ensure stability during the construction sequence in the event of a natural disaster.
Caltrans Director Tony Tavares highlighted the broader benefits of the crossing, noting how the project supports both wildlife preservation and public safety.
“Wildlife crossings are unique because they allow people and nature to thrive together,” Tavares said. “By building the Wallis Annenberg Wildlife Crossing, Caltrans is supporting transportation infrastructure that will not only reconnect and restore habitats but also reduce vehicle collisions with wildlife and enhance highway safety.”
The bridge will feature coastal sage scrub plants, native to the Santa Monica Mountains, as part of an overall environmental restoration strategy. In addition to the bridge, the project will involve 12 acres of open space and the planting of 50,000 native plants. In May, crews are scheduled to begin planting approximately 5,000 native species, further contributing to the ecological restoration of the area.
The project is part of a broader vision to preserve and restore biodiversity across California, ensuring that wildlife populations can thrive and move freely across the landscape. As a key component of California’s 30×30 conservation goals, the crossing is a model of how infrastructure and wildlife protection can coexist and support each other.
By reconnecting wildlife with the habitats they need to survive and thrive, the crossing will play a crucial role in preserving the natural beauty and biodiversity of Southern California.
For more information about California infrastructure projects, visit build.ca.gov.
