Enhancing wildlife connectivity along California's highways: the cas of the state route SR 241 wildlife fence in Orange County California USA
  • Valarie L McFall
    Bio statement : Chief Environmental Planning Officer
    Extensive background working with large-scale infrastructure projects that involve strategic planning; outreach; consensus from regulatory agencies and community groups; public speaking and innovative ideas that resolve issues and move projects forward to completion.
    As Chief Environmental Planning Officer for California's largest tolling agency, The Transportation Corridor Agencies, her responsibilities include managing the Agencies' nearly 2,200 acres of open space, preparing environmental documents, managing grants, identifying properties for acquisition of open space, obtaining permits from federal and state resource agencies and reporting on all mitigation obligations.
    Country : US
    Contact : vmcfall@thetollroads.com
    Website : http://www.thetollroads.com

This project aims to:

  • Reduce wildlife-vehicle collisions on highways through appropriate design and construction of wildlife exclusionary fence;
  • Reduce habitat loss and fragmentation;
  • Develop reproducible exclusionary fence design guidelines.

Southern California’s Santa Ana Mountain Range is bound by Interstate 15 to the east and State Routes 91 and 241 to the north. Estimates suggest less than 30 adult pumas (Puma concolor) remain within this area. Threats include wildlife-vehicle collisions, habitat loss and fragmentation, depredation permits, and genetic restriction. Interstate 15 and associated developments are barriers that have resulted in the puma population being semi-isolated with reduced genetic variability and separation from other populations. Vehicle collisions are particularly concerning because of low annual puma survival rates, impacts to human health, and economic implications. Part of the solution lies in appropriately designed wildlife crossings coupled with effective wildlife protection fences.

The SR-241 Wildlife Protection Fence Project runs along both sides of a 6.5-mile stretch, from the SR-261 junction north to the SR-91 Freeway in Orange County, California. During construction of SR-241, United States Fish and Wildlife Service (USFWS) required the Foothill/Eastern Transportation Corridor Agency (TCA) to construct four wildlife undercrossings and conduct a five-year post-construction study to document the usage of the crossings. Although the study documented a substantial number of wildlife using the undercrossings, concerns regarding the number of wildlife still crossing the roadway at-grade remained.

In response, TCA contracted with the University of California, Davis (UCD) to conduct an assessment of SR-241 and formulate recommendations to enhance wildlife movement. UCD studied the behavior and movement of wildlife along SR-241 by installing and monitoring cameras, collecting and analyzing data from GPS-collared pumas, documenting intrusions and mortalities along the roadway, modeling crossings, and conducting an extensive on-the-ground examination of the roadway, including the undercrossings and right-of-way fencing.

Results confirmed existing wildlife-crossing structures along SR-241 are adequate in size, type, and location to allow wildlife movement. However, due to the ease with which wildlife can access the roadway and cross at-grade, UCD recommended that state-of-the-art wildlife protection fence be constructed. The fence is 10-to-12 feet (3-3.7 meters) high; has an 18-inch (46-centimeter) “outrigger,” is buried 24 inches (0.6 meter) to prevent animals from digging under the fence; and is in close proximity to the roadway shoulder to minimize natural habitat loss. The fence is expected to reduce collisions by 90 to 95 percent. For the wildlife that may still enter the roadway, jump-out ramps that provide animals with an escape back into the open space have been included.

Effectiveness of the fence and efficacy of the undercrossings will be evaluated through an adaptive management approach over a three-year period. This includes reviewing Caltrans maintenance records; as well as, monitoring cameras at three bridge undercrossings, 27 jump-out-ramps, five culverts, and fence end-points to detect any breaches by wildlife.

Monitoring will determine if:

  • The exclusionary fencing reduces collisions;
  • There are changes in use patterns because of the fence; and
  • There is an impact on the overall welfare of the Santa Ana Mountains puma population.
traffic mortality, accidents, mortality, barrier effect, fauna passages, efficacy, mitigation, monitoring, traffic noise, verge management, vegetation, compensation, wildlife fencing