US-101 Liberty Canyon Wildlife Crossing
A FIRST FOR CALIFORNIA
Liberty Canyon Wildlife Crossing Project (PDF)
Caltrans proposes to build a wildlife crossing across U.S. Route 101 (US-101) just west of Liberty Canyon Road in the City of Agoura Hills in Los Angeles County. The purpose is to help maintain wildlife populations that travel between the Santa Monica Mountains and Simi Hills, and ultimately to the Sierra Madre Mountain Range. This linkage has been identified in numerous county, city and regional plans and publications as a critically important connection for wildlife. Such wildlife crossings have been built and used successfully in other states and countries. The Liberty Canyon Wildlife Crossing would be the first of its kind in California.
The purpose of the proposed project is to provide a safe and sustainable wildlife passage across the freeway in order to help create an important linkage in the region. The crossing would help reduce wildlife mortality, ease animal movement across habitats, and allow for the exchange of genetic material. In particular, large mammals such as mountain lions and bobcats need large connected habitats in order to hunt, breed, and thrive. US-101 divides this previously contiguous ecosystem into isolated habitat fragments; for mountain lions, this has resulted in inbreeding, territorial fighting, and a decrease in genetic diversity. Without the addition of a wildlife crossing, the ecological and environmental impacts on wildlife movement that resulted from the original construction of US-101 will persist. The proposed project would also help mitigate anticipated future effects of climate change on the current distributions of species across habitats.
Three alternatives were evaluated for this project, the No Build Alternative and two build alternatives with two design options.
No Build Alternative – The No Build alternative will maintain the existing configuration of US-101 and no additional infrastructure will be will constructed to enhance wildlife connectivity across the freeway.
Directional fencing is currently being constructed as part of a separate project. This fencing would funnel wildlife to the existing Liberty Canyon Road undercrossing. Under the No Build Alternative, this fencing will remain.
Alternative 1 – Alternative 1 proposes to construct a 165-foot wide by 200-foot long bridge across US-101 immediately west of Liberty Canyon Road.
Alternative 2 has two design options:
- Design Option 1- Construct a 48-foot wide bridge and associated retaining wall system along Agoura Road to keep the road operational and to accommodate the fill material needed to construct the wildlife crossing.
- Design Option 2- Construct a 54-foot wide bridge and associated retaining wall system along Agoura Road to keep the road operational and to accommodate the fill material needed to construct the wildlife crossing.
Both design options for the proposed overcrossing over Agoura Road will consist of a vertical clearance of 18 feet.
Common Design Features of the Build Alternatives
Common design features of both build alternatives (Build Alternative 1 and 2) include:
- Constructing a two span 165-foot wide by 200-foot long bridge with columns on spread footings in the freeway median.
- Constructing retaining walls at both the north and south ends of the bridge.
- Constructing soundwalls along the outer edges of the bridge to mitigate traffic noise and block light in order to make the crossing more conducive to wildlife crossing.
- Planting vegetation on and adjacent to the bridge to create an extension of the surrounding wildlife habitat and connect the crossing to the existing riparian corridor.
- Installing irrigation and drainage systems on the bridge.
- Filling and grading the slope and open area between the freeway and Agoura Road from the southern bridge abutment down to the shoulder of Agoura Road.
- Modifying or replacing existing wildlife fencing to prohibit wildlife from accessing US-101 and funnel wildlife to the overcrossing.
- Constructing a five- foot, multi-use, single-track compacted dirt recreational trail on the overcrossing.
- Directional fencing is currently being constructed as part of a separate project. This fencing would funnel wildlife to the existing Liberty Canyon Road Undercrossing. Under the Build Alternatives, this fencing may be modified to funnel wildlife to and through the project instead.
Unique Features of Build Alternatives
Build Alternative 2 will include:
- Grading and filling the slope between the bridge abutment and Agoura Road south of the freeway to grade to allow the crossing to extend over Agoura Road before descending to join existing ground.
Two other alternatives exist for this project, but were not fully developed due to recommendations from Caltrans’ Project Delivery Team. Both alternatives proposed to construct a tunnel under US-101 to serve as a wildlife crossing. Neither tunnel would convey wildlife across and to the south of Agoura Road since they would have entrances to the north of Agoura Road, adjacent to US-101.
The first, smaller, tunnel was a 13’ x 13’ jacked box culvert located west of Liberty Canyon Road. This tunnel would not accommodate the same wide range of wildlife species as an overcrossing. A tunnel study, originally done by the Federal Highway Administration Central Federal Lands Highway Division (FHWA-CFLHD) in 2010 and updated in 2015, estimated the cost at approximately $19.7 million (see the Project Study Report, Attachment I). It was agreed that the cost-benefit would not achieve the goals of the project.
The second, larger, tunnel was a 32’ wide x 15’ high cast-in-place rectangular culvert located west of Liberty Canyon Road. This tunnel was not considered feasible due to constructability considerations and high traffic impacts. Specifically, such a large tunnel would require using the cut-and-cover technique and the closure of US-101, one of the busiest freeways in the region. In addition, it was estimated that such a large tunnel would be more costly than an overcrossing.
Who is Involved
This project presents a unique opportunity for public-private partnership. Current partners in the project include Caltrans, the Mountains Recreation and Conservation Authority, the Santa Monica Mountains Conservancy, the National Park Service, and the Resource Conservation District of the Santa Monica Mountains. Additional support and partnership is being provided by Senator Fran Pavley, Assemblymember Richard Bloom, LA County Supervisor Sheila Kuehl, the National Wildlife Federation, Congressman Ted Lieu, Ventura County Supervisor Linda Parks, the City of Agoura Hills, the City of Thousand Oaks, and the State Coastal Conservancy.
Where We’re At In The Process
The joint Initial Study with Proposed Mitigated Negative Declaration/ Environmental Assessment (IS/EA) it currently available for public review and comment. A Public Hearing will be held on October 12, 2017. Please submit comments on the IS/EA, no later than October 26, 2017.
October 12, 2017 – Public Hearing
The public comment period will be open from
- Project Study Report for Liberty Canyon Wildlife Crossing (5/1/2015) (PDF - 5mbs)
- Location Map
- Drawings of Alternatives
- Alternative 1 (No build) - Current view looking northeast
- Alternative 2 – Build crossing over US-101 (for reference only, design currently under review)
- Alternative 3 -Preliminary design profile (for reference only, design currently under review)
- Alternative 3 – Build with extension over Agoura Road (for reference only, design currently under review)
- Proposed crossing location (preliminary draft)
- http://www.cbsnews.com/news/60-minutes-mountain-lions-of-los-angeles-2/ http://www.topangamessenger.com/story_detail.php?ArticleID=8071
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