NCDOT is building highway bridges for wildlife as well as humans

·6 min read

The N.C. Department of Transportation is building a bridge on Interstate 40 that is one of the first in the state to take into account the needs of bears and elk.

The bridge will carry I-40 over Cold Springs Creek and Harmon Den Road near the Tennessee state line in the narrow, winding Pigeon River Gorge.

The highway creates a barrier there between two sections of Pisgah National Forest. To the south and west is Great Smoky Mountains National Park and its growing elk population centered in Cataloochee Valley. To the north and east is Max Patch, a 4,600-foot mountain bald that is popular with hikers and wildlife, including elk.

This month, a contractor started work on a new bridge at Harmon Den Road that will include more space for animals to follow the creek under the highway. New 9-foot-tall fences on either side will steer bear, deer, elk and other wildlife toward the bridge opening. Meanwhile, cattle guards — grids of steel beams that farmers and ranchers use to keep livestock from roaming — will be built into the pavement on the exit and entrance ramps.

“I don’t know that we’ve ever done that in North Carolina in this type of situation, putting a cattle guard on an interstate highway to keep animals from getting on the interstate,” said Wanda Austin, NCDOT’s division engineer for the region.

The hope is that by making it easier for animals to go under the highway they won’t cross the pavement and put themselves and people in danger, says Liz Hillard, a wildlife scientist with the conservation group Wildlands Network who studies animal movements in the gorge.

“They need these large areas to roam and find resources,” Hillard said. “And then there’s the human safety aspect. Hitting a 1,000-pound elk is dangerous.”

Wildlife passages are more common out west, Hillard said. In Montana, for example, the state transportation department built more than 40 wildlife crossings along a stretch of U.S. 93 through the Flathead Indian Reservation, including a large, grass-covered overpass for bears, deer, elk and moose.

Other wildlife highway crossings in NC

NCDOT has made accommodations for wildlife as well, though much less often. In the 1990s, at the request of the N.C. Wildlife Resources Commission, it built two culverts under a new stretch of Interstate 26 northwest of Asheville for black bears. NCDOT later worked with the commission to design and build three wildlife underpasses for bears, deer, red wolves and other animals under a new stretch of U.S. 64 in Washington County, east of Plymouth.

In 2005, NCDOT agreed to build a higher and longer replacement bridge for U.S. 15-501 over New Hope Creek in Durham to make more room for wildlife, primarily deer that follow the creek. Ron Sutherland, chief scientist for Wildlands Network, said the group has been studying how deer use the passage and, with cameras mounted on the bridge, counted more than 2,000 in a single year.

“I think our data show the 15-501 bridge has been a tremendous success,” Sutherland said. “Thousands of people drive over that bridge every day without knowing how many deer and other wildlife are flowing safely underneath.”

NCDOT is planning a more ambitious crossing in Graham County, where the Appalachian Trail crosses N.C. 143 at Stecoah Gap. The Corridor K project, as it’s known, calls for the state to build a land bridge, planted with vegetation, to carry hikers and wildlife over the road.

“It’s really just protecting that corridor for the wildlife and making it safer from a hiker’s perspective, so that they’re not coming out on the road,” Austin said. “And obviously that helps the motoring public, too.”

A change in culture at NCDOT

When I-40 was built through Pigeon River Gorge in the late 1960s, little thought was given to wildlife, in part because there wasn’t as much of it. Elk hadn’t been seen in North Carolina since the late 1700s, and black bears were relatively rare.

Things have changed. Elk were reintroduced at Cataloochee in 2001, and bears have become so numerous that sightings on the streets of western North Carolina’s largest city, Asheville, have become routine.

Conservationists were initially concerned about how to make it easier for elk to safely cross I-40 in the Pigeon River Gorge, says Jeff Hunter, regional manager for the National Parks Conservation Association. That led to a meeting in the winter of 2017 that evolved into a conversation about other types of wildlife as well.

Hunter says he approached NCDOT about accommodating wildlife in the gorge later that year and got little response.

That began to change the following year, he says, when the Federal Highway Administration held a two-day workshop on wildlife crossing strategies in Maggie Valley, not far from the gorge. NCDOT has been engaged with conservation groups in the mountains since then, Hunter says, and was receptive to modifying the Harmon Den Road bridge.

“It’s a very positive step forward, and it’s an indication that the agency itself is changing,” Hunter said. “Hearts and minds and as a result culture, which is exciting to see.”

NCDOT is replacing the bridge, and eventually four others on I-40 in the gorge, because of age and deterioration. The new bridge, scheduled open to traffic late next spring, will be the same length as the old one.

But the bridge abutments have been redesigned to provide more room underneath. The extra space will be used for flat trails on both sides of Cold Springs Creek that Hillard said should act as “greenway trails for wildlife.”

Harmon Den Road just a start

The conservation groups formed a coalition called Safe Passage that hopes to find other ways to help wildlife safely cross I-40 and other roads in western North Carolina and eastern Tennessee. It has spent more than two years studying how and where animals cross the interstate, using GPS collars on elk, weekly surveys of animal carcasses along the road and more than 100 remote cameras.

Harmon Den Road is one of several hot spots along the 28-mile stretch of highway through the gorge, in part because the river and the creek provide natural routes for wildlife to follow.

The fencing, cattle guards and trails for wildlife will add little to the $19 million cost of replacing the bridge, said Austin, the NCDOT engineer. Hunter said Safe Passage has raised $100,000 to help cover the added cost and will raise more if needed.

Safe Passage will use the data it has collected to point to other places where NCDOT could help wildlife cross the highway.

Potential strategies include new land bridges or tunnels, but also new fencing to steer animals to existing culverts or retrofitting or enlarging culverts to make it easier for animals to pass through. The infrastructure bill signed into law by President Joe Biden includes $350 million for animal crossing projects nationwide.

“In the I-40 corridor, Harmon Den is a really, really positive start,” Hunter said. “But there’s more to be done.”

The old Interstate 40 bridge over Harmon Den Road and Cold Springs Creek, right, being demolished in November 2021. The new bridge will include a wider opening and trails along the creek to encourage wildlife to cross under the highway.
The old Interstate 40 bridge over Harmon Den Road and Cold Springs Creek, right, being demolished in November 2021. The new bridge will include a wider opening and trails along the creek to encourage wildlife to cross under the highway.
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