More than Models and Field Data: Site-specific Design of Wildlife Crossings in Alaska

The Sterling Highway Milepost 45-60 Project is a highway re-alignment project located south of Anchorage, Alaska along the Kenai River and passes through the Chugach National Forest and the Kenai National Wildlife Refuge. The Alaska Department of Transportation and Public Facilities (ADOT&PF) undertook the project to improve the overall safety of section of highway that sees frequent vehicle-vehicle as well as wildlife-vehicle collisions. During development of the EIS, resource agencies and the public identified impacts to wildlife movement and habitat fragmentation as key issues that required mitigation incorporated into the project design. The Kenai River supports high densities of moose, brown and black bears, and other species that move between the river and core upland habitats. To address these issues, ADOT&PF committed to working with resource agencies to study the movement of six focal wildlife species that would drive the siting and design of dedicated wildlife crossing structures.
This presentation will focus on two aspects of the project. First, it will detail the wildlife movement studies that have been ongoing since 2015, including general results and trends over time, our initial use of artificial intelligence to speed up data entry, how our results informed the identification of key wildlife movement corridors, and how wildlife crossings were sited in these corridors to maximize their potential future use. These studies have utilized landscape-level habitat modeling and camera trapping to predict high use corridors that helped determine the location of four undercrossings and one overpass dedicated for wildlife use. As the design process has progressed, data collected from camera traps in the vicinity of each designed wildlife crossing structure have been used to provide ADOT&PF with recommendations on site-specific design features such as crossing size, fencing, guardrail configuration, and potential solutions to reduce traffic noise near the openings of undercrossings. To date, two of the planned five planned wildlife crossings have been constructed.
Secondly, the presentation will describe the collaborative approach the project team has taken with resource agencies in the overall design of the highway, including the wildlife crossing structures. In order to meet their mitigation commitments, the project team formed a Wildlife Crossing working group to give agency stakeholders a real say in the design of each crossing structure. Through site visits, discussions of lessons learned from other highway projects, and a detailed public-facing web map, the working group developed several important modifications to the crossing structure designs that were implemented. These design modifications will improve the effectiveness of the structures and meet other goals such as reducing surface impacts to important wetlands adjacent to the Kenai River.