Wildlife Infrastructure Plan for State Route 94, San Diego County Post Miles 15.27 to 30.00

The California Natural Community Conservation Planning (NCCP) program is an ecosystem-based approach to conserving species and their habitats in a linked network of high quality habitat blocks, with an emphasis on maintaining landscape integrity and ecosystem functions.  NCCP-conserved lands in southern San Diego County (South County) support the largest expanse of remaining coastal habitats in southern California—coastal sage scrub, maritime succulent scrub, chaparral, riparian woodlands, vernal pools, and grasslands.  Intact landscapes are critical to genetic interchange within plant and animal populations and allow dispersal and recolonization of new areas.  Large landscapes that span elevational gradients, such as this core area in South County, also enable populations to shift in response to environmental and land use changes.

State Route 94 (SR-94), among other roads, cuts through the heart of this core area, potentially impeding wildlife movement across otherwise intact landscapes.  New residential development and a casino under construction in Jamul will increase traffic and potentially impact the wildlife value and connectivity of adjacent conserved lands.  Proposed road improvements associated with these new land uses provide an opportunity to mitigate the potential barrier effects of SR-94 as well as accommodate current hydrologic flow that has increased as a result of development and additional impervious surface not anticipated in the original design of the highway.  Scientific literature suggests that strategically-placed wildlife fencing along roads, combined with effective wildlife crossing areas (e.g., undercrossings, overcrossings, bridges) are the most effective means of influencing animal behavior and directing animal movement, thereby reducing roadkill, enhancing connectivity, and improving traffic safety. 

The purpose of this document is to (1) identify where improvements to existing infrastructure on SR-94 could improve connectivity across the South County preserves, using Best Management Practices from the scientific literature, (2) recommend wildlife movement monitoring to identify where new crossings are needed, and (3) identify where additional conservation would enhance the integrity of South County linkages.  Wildlife movement studies, camera traps, and systematic collection of roadkill data will refine the design and placement of wildlife fencing and crossing structures.  Once implemented, post-construction monitoring should be conducted to ensure that the new infrastructure is functional and cost-effective. 

This review prioritizes infrastructure improvements of 35 existing undercrossings inspected by wildlife experts in the field along 14.6 miles of SR-94 where the highway bisects conserved lands—particularly between the San Diego National Wildlife Refuge (SDNWR), where a box culvert has been designed specifically for this undercrossing, between Rancho Jamul Ecological Reserve (RJER) and Hollenbeck Canyon Wildlife Area (HCWA), and between Bureau of Land Management (BLM) lands and the Lawrence and Barbara Daley Preserve (LB Daley).  In total, SR-94 crosses >10 miles of conserved lands with only three bridges—at the Sweetwater River, Dulzura Creek, and Campus Grove bridge in Dulzura.  Following is a summary of improvements recommended for existing undercrossings and proposed new undercrossings, by segment, presented in this document.

1      On at least one side of the highway

²    Near-term improvements or replacements proposed for existing undercrossings

³    Longer-term proposed new undercrossings  

The majority of the recommendations for infrastructure improvement focus on increasing the diameter, and thus the openness ratio (cross-sectional area divided by length), of the undercrossing itself, removing vegetation and debris blocking the undercrossing, restoring habitat in the approach to the undercrossing, and installing fencing to both (1) keep animals off the highway and (2) funnel wildlife to the undercrossings.  These improvements are intended to facilitate connectivity for the community of species, as opposed to a single target species. Monitoring wildlife movement should help inform placement of new undercrossings and evaluate their effectiveness post-construction.  Increasing the diameter of existing undercrossings and restoring approaches will also facilitate the current and future volume of hydrologic flow, not anticipated in the original design of the highway.

The appendices summarize the covered species that will benefit from these improvements, along with examples of proposed infrastructure and their costs, and roadkill data over the past 5 years.  The cost of not implementing these improvements will be a loss of habitat integrity and ecosystem function in the largest core area in San Diego County.