I-15 Wildlife Crossings

I-15 Mojave Wildlife Crossing Restoration Project

Map of Interstate 15 Wildlife Crossings Project. Please Contact 909-383-4657 or email D8_1N590_Questions@dot.ca.gov for Questions.


The California Department of Transportation (Caltrans), the California Department of Fish and Wildlife (CDFW) and Brightline West have entered into an agreement to design and construct three wildlife overcrossings across Interstate 15 (I-15) and the future Brightline West high-speed rail system connecting Las Vegas and Southern California. These dedicated overcrossings will provide a sustainable and safe path for wildlife – especially for bighorn sheep – over the existing northbound and southbound highway lanes and the future high-speed rail system to be built within the median.

This project aims to bolster habitat connectivity for desert species. Environmental impacts and mitigation measures were not considered nor required when I-15 and most of Southern California's freeways were built in the 1950s. As a result, the construction of I-15 divided the previously connected natural habitat ranges of many wildlife species. Currently, safe, and sustainable paths for wildlife to cross I-15 are not available. Without the addition of wildlife crossings in the vicinity of Cave Mountain, Soda Mountain, and Clark Mountain Pass in San Bernardino County, the ecological and environmental impact on wildlife that resulted from the construction of I-15 will persist.

This website will provide updated information about progress on the I-15 wildlife crossings project.

The Project Team – Roles and Responsibilities


  • Lead NEPA / CEQA clearance
  • Public sponsor for Federal and State grant applications
  • Lead BLM ROW transfer
  • Lead Operation and Maintenance


  • Lead Coalition Building
  • NEPA / CEQA Cooperating Agency
  • Support Federal and State grant applications and BLM ROW transfer
  • Support of Operation and Maintenance

Brightline West

  • Design and Permitting Support
  • Support Federal and State grant applications
  • Design / Build Project Management
  • Design / Build Implementation

Project Description

This project will construct wildlife crossings and directional fencing in the Mojave Desert at three locations along I-15 near Cave Mountain (PM R116.70), Soda Mountain (PM R129.75), and Clark Mountain (PM 168.05).

The bridges are proposed to be two-span cast-in-place/prestressed concrete box girder structures with openings for the existing NB and SB I-15 lanes and the future BLW rail in the median.  The bridges are proposed to be 100 ft wide, 240 ft to 400 ft long, and the spans will accommodate space for one additional future travel lane in each direction.  Railing and fencing will be installed at the edges of the bridges and chain link directional fencing will also be installed at various lengths along the access control line to direct wildlife to the crossings.  The limits of this fencing will be based on recommendations from wildlife experts.  The surface of the bridges will be composed of native materials to match the characteristics of the surrounding areas.  Other bridge types may be considered during the design phase.

Purpose and Need


The purpose of this project is to restore wildlife connectivity by constructing bridges across Interstate-15 (I-15) in the vicinity of Soda Mountain, Cave Mountain, and Clark Mountain Pass in San Bernardino County to function as wildlife crossings. The dedicated wildlife crossings will provide safe and sustainable passages for bighorn sheep and other wildlife across I-15 that restores bighorn sheep wildlife connectivity and allow for the safe movement of animals, and the exchange of genetic material. The project will assist in restoring and enhancing wildlife connectivity among metapopulation fragments of bighorn sheep and facilitate crossing of the I-15 of other species.


The need for the proposed project is based on desert bighorn sheep genetic and tracking data that demonstrates I-15 is a movement barrier for sheep that have historically traveled between the northern mountain ranges and southern mountain ranges. While there are several undercrossings (washes and large box culverts) present throughout the I-15, data shows desert bighorn sheep are less likely to move through these structures, unlike other medium and large mammals such as bobcats and mountain lions. Like other large mammals, desert bighorn sheep need large, connected habitats to breed and thrive. I-15 divides the previously connected ranges into isolated habitat fragments. This decreases desert bighorn sheep genetic diversity, increases inbreeding, and increases territorial disputes amongst males. The fragmentation of habitat currently forces desert bighorn sheep to cross over I-15, increasing risk of vehicular crashes and desert bighorn sheep fatalities. From 2007 to 2020, at least 59 desert bighorn sheep were killed by vehicles in California. Dedicated wildlife crossings are needed to restore wildlife connectivity.

Environmental Compliance

Caltrans is the California Environmental Quality Act (CEQA) Lead Agency for all improvement projects on the State Highway System (SHS).  Caltrans is also the National Environmental Policy Act (NEPA) Lead Agency for this project.

In compliance with the provision of the CEQA and based on the project information available, per Assembly Bill (AB) 155, a Public Resource Code section 21080.56 Statutory Exemption will be utilized for the project. Caltrans is currently working with CDFW on approving the CEQA Statutory Exemption.

In compliance with the provisions of the NEPA, it is anticipated that a Categorical Exclusion will satisfy the NEPA environmental compliance requirements. Caltrans is in the process of preparing Biological, Cultural Resources, Paleontological, Landscape/Aesthetic, and other technical studies to support the CE.


 Project Approval & Environmental Document  September 2023
 Design, Engineering and Right-of-Way  August 2023 - April 2024
 Begin Construction May 2024
 End Project June 2027


For questions, please contact: D8_1N590_Questions@dot.ca.gov