Snoqualmie Pass in Washington State has seen an amazing conservation effort on I-90. A wildlife bridge finished constructin nearly a decade ago so that local populations of animals can cross over the highway safely without posing a danger to themselves and commuters.
It was no easy task, and the project took years of investment to finally see it completed. The bridge aids local bears, elk, deer, and other wildlife in reconnecting with previously fragmented populations. However, the bridge has been slowly adopted by wildlife.
A Wildlife Bridge
Highways are important infrastructure and help to connect cities across states. These highways are essential for supply chains and for commuters, but they pose a problem to wildlife.
Highways span multiple lanes and cut right through natural landscapes, separating important populations and reducing their biodiversity in the process. Washington Bridge aims to rectify this issue and encourage animals to cross over the highway unimpeded.
First Large Predator Crossing
Wildlife is generally skeptical about using wildlife bridges that cross over highways at first. With the wildlife overpass on I-90 costing $110 million, it’s no small investment.
Luckily, over time, wildlife gets used to the bridges thanks to them being camouflaged with natural elements like plants and vegetation. As key species start to use these bridges as habitat corridors, some interesting wildlife has been picked up on the monitors, and May 2025 saw the first large predator crossing over since over a year.
Cougar Crossing
Trail cameras set up by WSDOT, the Washington State Department of Transportation, have seen the first large predator crossing over the overpass since January 2024.
This is a significant sight, as the sighting of a cougar proves that all types of wildlife are using the bridge, helping to restore the balance that highways often disrupt in ecosystems. The cougar caught on the cameras didn’t seem nervous or distracted and leisurely strutted to the other side of I-90.
Adapting
Wildlife adapting to these overpasses takes a bit of time, as animals are weary of busy urban structures like highways. There are many factors that can dissuade animals from using them, including the sound of vehicles below them, leftover scents from constructions, and changes in vegetation.
While the usage of overpasses can vary, wildlife usually gets used to these structures and integrates them into their regular migration after a few years.
Cost And Funding
The $110 million that was invested into the project included more than just the overpass – two under crossings, as well as expanded lanes and safety features, were built.
The funding was given from both federal and state transportation sectors, and Conservation Northwest also contributed to the project. The overpass alone only cost a little over $6 million, showcasing such expensive changes to the existing highway.
The Overpass Itself
The overpass itself had to be built big so that animals wouldn’t feel claustrophobic or close to the edges. With this in mind, the overpass is 150 feet wide and 66 feet long, acting as a bridge over all lanes of I-90.
Landscaping took place on the overpass to make it look more natural and includes more than 20 species of trees, shrubs, and groundcover to emulate the feeling of the surrounding environment.
Perceived Results
With the first cougar using the overpass, it made headlines and was covered by local and national news sources. Many people have been optimistic about the project, praising its innovation to protect both commuters and wildlife.
However, some are skeptical that the large quantity of money justifies its slow usage in the short term.
The project will start to show its value as more animals start using the overpass, but this will take time as they adapt and remember that it’s a viable path through an otherwise dangerous crossing.
Monitoring The Bridge
The overpass will continue to be monitored by WSDOT, the Washington Department of Fish and Wildlife, as well as non-profit groups. The trail cameras can be used as an important piece of conservation equipment, allowing researchers to track local populations and behavioral patterns, as well as how often species are using the overpass.
Monitoring is expected to last at least ten years to research the long term impacts of the overpass.
The Future
The overpass has already seen small mammals like deer and coyotes crossing over safely from one side to another, as well as the most recent sighting of the cougar.
The project isn’t about short-term success but rather the long-term benefits of animals integrating the overpass as a wildlife corridor, ensuring that biodiversity stays high and populations aren’t isolated. The bridge will be evaluated for years to come and could serve as a model for future wildlife overpasses at highways where wildlife conflict is becoming increasingly apparent.
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