Wildlife Underpasses Save More Than Animals

Thu August 07, 2014 - West Edition
Lori Tobias

The underpasses are located on Highway 97 near Lava Butte, south of Bend.
The underpasses are located on Highway 97 near Lava Butte, south of Bend.
The underpasses are located on Highway 97 near Lava Butte, south of Bend. One of the underpasses is a wildlife only underpass; the other, designed for wildlife, with an additional lane open seasonally to vehicles. Oregon is now planning a third migration route, this one to be an overpass also on Highway 97 near Chemult in south central Oregon. One of the underpasses is a wildlife only underpass; the other, designed for wildlife, with an additional lane open seasonally to vehicles.


When officials with the Oregon Department of Transportation talk about the two wildlife migration underpasses they recently built and a third proposed migration overpass, it tends to sound a little touchy-feely, inspiring comments along the lines of "Aw, isn’t that sweet." And it’s true, it does save wildlife. But that’s not the only thing it saves.

"The concept is protection of wildlife," said Jay Davenport, construction project manager of the Oregon Department of Transportation. "But it is also for motorists. If you look at the cost per incident in a motor vehicle/animal accident, it’s estimated to cost $750,000 in the long term effects of people who get killed in collisions. Is it saving wildlife or people? It is both."

The underpasses are located on Highway 97 near Lava Butte, south of Bend. One is a wildlife only underpass, the other, designed for wildlife, with an additional lane open seasonally to vehicles.

"Thanks to the construction of the underpasses … the number of animal-vehicle collisions is way down," said Meg Kenagy, Oregon Conservation Strategy communications coordinator. "Deer, elk, bobcats, black bears, squirrels and other species are using the structures to avoid crossing the highway, making it safer for people and wildlife."

The underpasses were built over a two year period when the highway was being expanded from two to four lanes. Because it takes animals several generations to learn to use the safer route, fencing along a 4 mi. (6.4 km) stretch of the highway also was incorporated into the project to direct animals to use the underpasses.

"Since the structures were completed in 2012, an ongoing study has shown a greater than 80 percent reduction in deer mortality along that stretch of highway," Kenagy said.

The underpasses, which cost $2 million, were built using standard bridge building construction, said Davenport.

"First, we did embankment construction with bulldozers, excavators and rollers," he said. "There are two bridge sets, for a total of four bridges that are twins of each other. It does take a lot of time, excavating, setting the rebar, pouring the foundation, working up to the bridge deck. One is 60-feet wide and the other is 100-feet wide. The project on Highway 97 was the first on the state highway system."

Colorado and Utah were the first states to build some type of wildlife vehicle protection system. They also are utilized in Alberta, Canada, near the Lake Louise area where there were significant problems with animal-vehicles collisions, Davenport said.

Now, Oregon is planning a third migration route, this one to be an overpass also on Highway 97 near Chemult in south central Oregon.

"In this case, animals will be going over the top of the highway," Davenport said. "It will look like a pedestrian bridge but a lot wider."

The project is still in the design phase, but will likely be a precast concrete arch, said Zach Beget, bridge designer.

"That means it’s built somewhere else, and they bring it here and erector-set it in place," Beget said. "This type of construction is fairly quick. It stays out of the travel lane of Highway 97 so you’re not really having to postpone traffic. The cranes will be on sight. The concrete arches travel on trucks and the cranes pick them up and set them in place."

ODOT is looking to a similar overpass in Nevada as guide for the one they hope to construct in Oregon. But the plans are still preliminary and could change, Beget said.

Another option would be building an arch bridge out of corrugated metal.

"We have until November to make a decision," Beget said. "It’s going be around $2 million just for this one structure. It’s quite large. The highway is currently two lanes but it will be expanding to four and we want to be to accommodate the additional lanes. Right now, we have enough funding for 30 percent of the design acceptance phase. We’re hoping once that is done, the funding to build it will follow."