Big year for wildlife overpasses in West


One arch over I-90 east of Seattle has been completed. Work is expected to wrap up in 2018. The highway is being widened from four lanes to six lanes. Photo/WSDOT

Wildlife overpass across across I-90 may be continent’s most ambitious

Profusion of wildlife overpasses in the West this year

by Allen Best

SNOQUALMIE, Wash. – It’s been a big year for wildlife overpasses in the West. Two were completed in Colorado; one is taking shape in Washington state and another in Nevada. More are being planned in British Columbia, and there may be more coming in Utah and Wyoming.

Near Snoqualmie Pass, about an hour east of Seattle, construction crews recently stacked 39 pre-cast panels of concrete and rebar, each weighing 40,600 pounds, across the westbound lanes of Interstate 80. With similar panels on the other side, the arch for what will become a forested bridge is now in place.

When all is done in 2018, wildlife funneled into the crossing by fences along I-90 will find a 66-foot-wide crossing topped with soils, trees, and other native plants. Ten-foot walls on either side of the bridge will keep out the glare of passing headlights from cars, the Seattle Times notes.

This is part of a bigger project that will ultimately yield 27 places in a 15-mile stretch for wildlife to move to the opposite side of the highway. The work is intended to promote biodiversity and prevent motorists from killing wildlife or being killed in such collisions. It may also help some species tolerate the changing climate.

Some species, particularly large predators and migratory mammals, prefer overpasses, said Charles Raines, director of the I-90 Wildlife Bridges Coalition. “Elk like open. They don’t like stuff above their head,” he told the Times.

Raines said as temperatures rise with the changing climate, some species will need the bridges to migrate.

The Times notes that a more permeable highway may allow wolves to expand their range south of the Interstate. Last spring, about 10 miles away, a wolf was found dead on I-90.

Tony Clevenger of the Western Transportation Institute calls the Snoqualmie project “by far the most ecologically comprehensive mitigation project I’m aware of in North America and likely the world.” He consulted on the project.

A resident of Canmore, Alberta, near the east entrance to Banff National Park, Clevenger helped design the wildlife overpasses and underpasses of the TransCanada Highway between Banff and Lake Louise. They constitute the motherlode of wildlife crossings in North America. A study of wildlife that uses the crossing there found that grizzly bears, wolves, moose, and deer nearly always chose overpasses to cross the TransCanada Highway. Cougars, however, are more comfortable with the wildlife underpasses.


The wildlife overpass under construction in the Cascade Range is described by one expert as the most ambitious in its goals in North America and maybe the world.

Many wildlife crossings are driven by the goal of keeping large animals off the highways and, ultimately, hoofs off hoods. In other words, the motive is improved highway safety. But crossings in Banff and elsewhere are also created to allow many other creatures free movement.

The crossing being built at Snoqualmie tries to allow movement by many species, some big but even fish. “They had to consider a lot of creatures, from flying squirrels to pikas to bull trout to the big critters, deer and elk,” says Rob Ament, program manager for road ecology at the Western Transportation Institute in Bozeman, Mont.

Wildlife overpasses are being installed at many places, Ament tells Mountain Town News, because of accumulated evidence about their effectiveness. Efforts to change driver behavior, such as flashing lights and signs, have proved far less successful. The acceptance has been occurring over the last decade.

“At first it’s experimental, and as you monitor the experiments to see how well they work, you have the evidence,” he says. Then, more were built in different situations. Banff National Park is very different than in a working landscape, where you have auxiliary roads. It’s also very different than on Highway 93 in Arizona, near Hoover Dam, where overpasses are being built for bighorn sheep.

Too, he thinks there’s growing acceptance of the need for wildlife overpasses for habitat connectivity.

“We are talking about ecological integrity and not just avoiding collisions with large ungulates,” he says.

Two wildlife overpasses across Highway 9 in Colorado's Middle Park were completed this year. Photo/Allen Best

Two wildlife overpasses across Highway 9 in Colorado’s Middle Park were completed this year. Photo/Allen Best

In Colorado, two overpasses  across Highway 9 between Silverthorne and Kremmling are being completed this year. A $39.2 million highway project will yield five wildlife underpasses, two wildlife overpasses, and a widening of the highway’s shoulder to eight feet, reports the Sky-Hi News. The work there was motivated to end the frequent collisions with deer and motorists.

“We’re saving the lives of people. We’re saving property damage, and we’re saving animals,” Kathy Connell, chairwoman of the Colorado Transportation Commission, told Steamboat Today.

In British Columbia, Parks Canada has announced plans for one wildlife overpass and three wildlife underpasses along the TransCanada Highway in Yoho National Park, reports the Calgary Herald.

In Utah, about a mile of wildlife fence is being installed along I-80 near Park City. A spokesman for the Utah Department of Transportation tells the Park Record that the agency will soon hire a contractor to begin designing a wildlife overpass.


Nevada completed a wildlife overpass of I-80 at Silver Zone Pass in 2014. Photo/Nevada DOT

Nevada is investing significantly in creating structures to allow wildlife, including wild horses, safe movement both over and under highways. It already has a crossing of I-80 near Wendover, and two more are now under construction at Pequop Pass, primarily to allow mule deer to move across the highway without posing a risk. Several more exist on the north-south Highway 93.

In Wyoming, Teton County has allocated $100,000 to study the feasibility of wildlife overpasses and underpasses in Jackson Hole. The money will go to the Western Transportation Institute to develop a plan, reports Planet Jackson Hole.

In these and other cases, high fences along the highways are needed to funnel the wildlife into the overpasses and underpasses. That is also being started in Utah along I-80.


About Allen Best

Allen Best is a Colorado-based journalist. He publishes a subscription-based e-zine called Mountain Town News, portions of which are published on the website of the same name, and also writes for a variety of newspapers and magazines.
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One Response to Big year for wildlife overpasses in West

  1. Nathan Edelson says:

    Yesterday I drove from Kremming CO to Silverthone CO along CO Highway 9, a distance of 37 miles, when I got lost and took the “wrong” road from Steamboat Springs Hot Springs back to Glenwood Springs, where I recently moved.
    On this route are two new wildlife overpasses, of the most hideous architecture you could possibly imagine, totally out of keeping with the nature of the surroundings or anything suggestive of beauty, nature, or the preservation of the environment.
    You have captured one of these in your photos and when compared to the architectural treatments by other States such as Washington you can readily see the difference. I come from Washington, D.C., and in D.C. there is a style of architecture in which Greco-Roman architecture is poorly copied with fake patterned white concrete, very much like this CO Rt. 9 Wildlife overpasses. It is sick in Washington, but much sicker in the beautiful Mountain West I now call my home.
    If CO Wildlife advocates want to continue building Highway Wildlife Overpasses — a noteworthy goal — they should fire the current highway “architect” and hire a good one so that when CO taxpayers like me approach and pass under these new monumental creations in the middle of “nowhere” their eyes and souls will not be offended by the absolutely out-of-touch and utterly ugly and property-value reducing nature of these current monstrosities.

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