Largest wildlife overpass in North America opens in Colorado: "It's a win-win"

North America's largest wildlife overpass is now open in Colorado.

The overpass spans Interstate 25 near the Greenland exit south of Castle Rock. More than 100,000 cars travel through the area every day, and now animals can safely cross as well.

During spring and fall, the stretch of I-25 between Castle Rock and Monument, known as the South Gap, sees about one wildlife collision a day. A new wildlife crossing overpass aims to change that.

Mary Rodriguez knows the cost of a wildlife collision.

"We are trying desperately to cope with losing him," Rodriguez said.

Her father, Victor, died last year on U.S. 85 in Castle Rock when a passing car struck a 700-pound elk, launching it into the air.

"He was killed immediately when the elk came through the windshield," Rodriguez said. "Had that fencing been in place, my dad could still be here with us today."

Along I-25, fencing and five wildlife underpasses were installed in 2022 as part of the South Gap project.

"As of August, we were able to reduce wildlife-vehicle collisions in the corridor by 91%," said CDOT Environmental Manager Chuck Attardo.

Attardo said the new wildlife overpass is strategically located between those underpasses.

"Animals are like people. They like choices, and the wildlife overpass was specifically designed for elk and pronghorn," Attardo said. "We made sure that this overpass was large and had great sight lines for those two species in particular. Now we think moose and deer and bear and mountain lion and other small mammals are going to use it as well."

At 209 by 200 feet, it is the largest bridge structure for wildlife in North America. Attardo notes that a recently constructed bridge designed to help cougars in California is longer, but says the Colorado bridge has a greater surface area.

"This could be a project of international significance. And in fact, in May, we've had people from all over the world come visit it," Attardo said.

The overpass connects 39,000 acres of wildlife habitat on both sides of I-25 between Larkspur and Monument. The area is known for high movement of large game.

Attardo said the project was completed ahead of schedule in just 10 months.

The project received $22 million in federal infrastructure investment funds and $8 million from the state, but Attardo said contractor Kraemer North America was able to complete it for just $15 million.

"So we're right now figuring out how to reinvest that money into the corridor, and one of the things we're focused on is actually building a little bit more of that wildlife fence," Attardo said.

Multiple cameras have been placed on the overpass to capture images of wildlife.

"Cool moments, public education, raise awareness, let people know that these things work, these wildlife mitigation systems pay for themselves because of the wildlife-vehicle collisions that you can reduce when you construct them," Attardo said.

"I think it's a wonderful thing to have for the wildlife and for the drivers, and I like to see all of the implementation of wildlife fencing as well along I-25," Rodriguez said.

Rodriguez said she is happy to see the improvements in her community.

"It just keeps the animals safe and it keeps the motorists safe. It's a win-win for everyone," Rodriguez said.

She hopes the stretch of U.S. 85 where her father died will be the next to receive wildlife fencing.

"My dad is proof that it is a very serious problem here," Rodriguez said.

Attardo said CDOT is planning a project on that stretch of U.S. 85 between Meadows Parkway and Sedalia. The project is in the design phase and would still need funding.

"We're working with Douglas County and the Colorado Parks and Wildlife to figure out where we can create some wildlife permeability in that section of U.S. 85 Santa Fe, because we know there's been a fatality, we know there's been other accidents," Attardo said. "We know it's a rising issue."

CDOT has six priority areas for future wildlife mitigation projects.

"I-25 at the New Mexico border, Raton Pass is what we call it, that's a statewide priority," Attardo said. "U.S. 287 between Fort Collins and Wyoming; that's a priority. U.S. 40 near Empire, so if you're going skiing up to Winter Park, that's one of our largest, that is our largest bighorn sheep population in Colorado. They're getting slaughtered right now. I-70 on the east side of Vail Pass; statewide priority. U.S. 40, huge migration route west of Craig, statewide priority. And state Highway 160 east of Mesa Verde; big migration route, statewide priority."

Attardo said the organization is hoping to get started on those projects once it secures federal funding.