Earth Day: animal traffic management

Construction is set to officially begin today – Earth Day – in California on what would be the world’s largest animal crossing bridge over a freeway.

The 67m-long, 50m-wide structure will span the eight-lane California State Highway 101 (Ventura Freeway) at Liberty Canyon in Agoura Hills, near Los Angeles. The second phase of the project will extend the structure onto the local dual carriageway Agoura nearby.

The project has spent several years in various design and approval stages and will cost between US$87 million and US$90 million. When completed in late 2025, the crossing will be named the Wallis Annenberg Wildlife Crossing in honor of the project’s largest donor, Wallis Annenberg and the Annenberg Foundation who donated $25 million.

The area, called the Santa Monica Mountains, is home to dozens of large animals and mammals including coyotes, cougars and mountain lions that search everywhere to mate and feed. There are also mule deer, goat snakes, lizards and rabbits. The highway dissects many conservation reserves and many of these animals end up trying to cross the busy highway that carries around 300,000 vehicles every day.

Funding and other resources for the project come from a myriad of public agencies, private nonprofit groups, and environmental organizations. About 60% of the cost will come from private donations, with the rest coming from public funds earmarked for conservation projects.

The Santa Monica Mountains Resource Conservation District, with General Manager Clark Stevens as architect, completed the initial design and 3D modeling of the overpass, working closely with the Caltrans – California Department of Transportation. Additional architectural and landscape design was done in collaboration with the #SaveLACougars campaign leader National Wildlife Federation.

The current bridge – nearly half a hectare in size – is part of a larger 3.2 hectare habitat restoration project which will include phase two on the adjacent dual carriageway and the surrounding countryside.

A tunnel was considered as an alternative, but would have been less likely to be used by wildlife and would not have supported vegetation. During this time, fencing at each end of the planned bridge will help funnel animals into using the bridge. Hikers, mountain bikers and horse riders can also take the crossing.

Caltrans said it would oversee construction of the project as it is a major transportation route and the agency will install cameras to allow live footage and video of construction work. Caltrans also said it is considering wildlife crossings on US 101 at Conejo Valley and at Rocky Peak and Moorpark on State Route 118. A recent Associated Press report noted that construction will take place primarily on night, which means little disruption to daytime traffic.

Construction begins today on Earth Day which is coordinated globally by EarthDay.org. Earth Day was launched in 1970 to demonstrate support for environmental protection and the official theme for 2022 is Investing in Our Planet.

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