The Greenland Overpass is a unique solution to a unique situation, says Chuck Attardo, I-25 south corridor environmental project manager for the Colorado Department of Transportation.

Few places on the continent have a similar confluence of human activity and wildness like the Interstate 25 corridor between Castle Rock and Colorado Springs. An eight-lane highway handling over 100,000 vehicles per day cuts directly through 54 square miles of protected habitat for elk, pronghorn and other animals.

“That setting is not replicated in too many places around the country,” he said.

Vehicle collisions with animals have been a hazard for decades, while herds that once roamed from the plains up into the foothills of Pike National Forest have been cut off, geographically and genetically.

In recent years, CDOT has worked to reduce collisions and create ways for animals to cross safely. The capstone of that project, what the state says is the largest wildlife overpass on the continent, opened for non-human traffic this month.

The Greenland Overpass slopes gently up from two previously disconnected conservation areas over the interstate north of Monument in Douglas County. The hope is that skittish animals that avoid the existing interstate underpasses will learn to use the overpass, which is big enough to accommodate a herd.

Douglas County Commissioner George Teal said he was hoping the passage would improve the health of wildlife, which in turn balance the grassland ecosystem vital to ranching operations in his district.

“Anything we can do to encourage the elk herds to have that good environment actually goes to the agricultural economy of Douglas County,” he said.

Since nothing quite to the scale of the Greenland Overpass has been built, it’s hard to predict its effect. Teal said he was optimistic based on the data available from other large wildlife overpasses in the Western U.S. and Canada.

Attardo said the project had already documented one significant event: In the past two months, cameras set up around the overpass caught five pronghorn on the west side of I-25 — where they haven’t been documented in years.

CDOT is not sure how the pronghorn crossed. The plains species has not been documented using any other means of passage across the interstate.

“Pronghorn especially, they hate underpasses,” said Attardo.

CDOT has set up four cameras on the overpass to document wildlife — two high resolution and two night vision. Researchers will watch how animals react to the new infrastructure and if migration can be achieved between the two separated conservation areas.

The project came in under budget and slightly ahead of schedule, said Attardo. Originally budgeted at $30 million, he said the state’s chosen contractor was able to lower the cost to $15 million using innovative building practices. Those included building a temporary roadway up and around the overpass to divert traffic while construction crews installed massive bridge girders. The 76 girders were installed over the course of eight days.

Colorado received $22 million in federal funding for the project, the remainder of which it would like to use to expand wildlife fencing to the borders of Monument and Castle Rock. Attardo said the wildlife-vehicle collisions that do still occur tend to happen where the fences end.

Still, he said efforts along the I-25 “South Gap” to reduce collisions through fencing and underpasses have already been successful: a report CDOT produced in August found that collisions were reduced by 91%.

With the completion of the Greenland Overpass, CDOT has a long list of places where it would like to put in similar, smaller projects. Among them are I-25 in the Raton Pass near the New Mexico state line, U.S. 287 from Fort Collins to Wyoming and Interstate 70 east of Vail Pass.

Federal money for Greenland came from the Federal Highway Administration’s Wildlife Crossings Pilot Program. Attardo said future projects may depend on whether the federal agency opens more applications for the $150 million still available in the program.

“We’re hoping that they announce that program again, and we’re able to go after some of that money,” he said.

Ian Griffis, an owner of ranchland about two miles from the overpass, said he hoped to see better genetic diversity among the elk herds that birth calves and participate in fall rut east of the interstate. The conservation corridor, he said, was a major public asset.

“Every Coloradan benefits from that,” he said.