Effective Roadway Mitigation Strategies: The Case of State Route 241 Wildlife Protection Fence Project in Orange County, California

Doug T. Feremenga, Transportation Corridor Agencies

This presentation highlights the State Route (SR) 241 in Orange County, California, to showcase how wildlife bridge-undercrossings, culverts, and exclusionary fences along highways can be utilized as effective mitigation strategies to: help maintain wildlife movement and connectivity; and reduce wildlife-vehicle collisions.  The SR 241, within the project area, consists of four lanes in each direction plus climbing lanes, with an annual average daily traffic of approximately 56,000 and is located in hilly terrain.

Estimates suggest less than 30 adult cougars (puma concolor) remain within Southern California’s 800-square mile Santa Ana Mountain Range.  Threats include wildlife-vehicle collisions, genetic restriction, habitat loss, and fragmentation.  Highways and associated developments are barriers resulting in the cougar population being semi-isolated.  Vehicle collisions are concerning because of low cougar survival rates, impacts to human health, and economic implications.  Part of the solution lies in appropriately designed wildlife crossings coupled with effective wildlife exclusionary fences, as demonstrated by the SR 241 Project.

Discussion will be centered around current efforts by the Transportation Corridor Agency to address the impact of highways on wildlife and habitat, specifically focusing on the constraints and opportunities related to the crossing designs and their use by wildlife, particularly the target species: mountain lions, deer, coyotes and bobcats.  The presentation will emphasize the lessons learned, as well as the three-year post-construction monitoring results of the recently completed wildlife protection fence along the SR 241.  

In the first year of monitoring, the fence reduced wildlife-vehicle collisions by up to 100 percent for three of the target species (cougar, bobcat, and deer) and up to 93 percent for the fourth species (coyote); in the second and third years, the fence resulted in a 100-percent reduction in roadkill of the target species.  Monitoring of the fence, which includes tracking wildlife-vehicle collisions, and monitoring cameras at bridge undercrossings, jump-out-ramps, culverts, and fence end-points to detect any breaches, is ongoing. However, the results of the past three years of monitoring demonstrate that the fencing, coupled with the undercrossings result in wildlife safely crossing under the SR 241, which provides benefit to the overall welfare of the target species in the region.  The results also show an interesting shift in the undercrossings use patterns, particularly an increase in the use of previously underutilized crossings.  Whether this shift in use of undercrossings is a result of the wildlife fence itself, subsequent wildfires, or weather patterns, will make an interesting discussion during this session.  

Note:
In 2017, the SR 241 Project was presented at the ICOET Conference in Utah, and titled Cougar Safe Trek: Leading the Next Generation of Wildlife Protection Along Highways – The Case of State Route 241 Wildlife Fence in Orange County, California. This presentation focused on the wildlife fence construction, specifically the planning, designing, financing, construction process, and first year monitoring results.  The current presentation focuses on the three-year post-construction monitoring results and highlights the success of the fence project in directing wildlife to the existing undercrossings, thereby reducing wildlife-vehicle collisions.  This presentation will also focus on lessons learned during this project.