Vail Pass project looks at wildlife connectivity

John LaConte
Vail Daily
I-70 Coalition Director Margaret Bowes, left, speaks at an event on Vail Pass in September 2020. The public comment period for the Interstate-70 West Vail Pass Auxiliary Lanes project environmental assessment began on Sept. 22 and ends Oct. 21.
John LaConte |

Vail Pass is a dangerous section of highway for motorists, especially in winter conditions, and when slow moving vehicles cause drivers to make quick lane changes.

A total of 566 crashes were reported from Jan. 1, 2014, through Dec. 31, 2016, between mile markers 180 and 190, with 205 injuries recorded.

CDOT has received one of the largest grants in the department’s history to improve safety in the area, and in addition to the safety of motorists, the department also has included wildlife safety in its core values.

The money will be used to create the Interstate 70 West Vail Pass Auxiliary Lanes project, a 2021 effort to add a 12-foot auxiliary lane, both eastbound and westbound, between mile markers 180 and 190.

Other sensitive species are known or suspected to use the area, as well, including American marten, Colorado River cutthroat trout, boreal owl, boreal toad, hoary bat, monarch butterfly, northern goshawk, northern leopard frog, pygmy shrew, olive-sided flycatcher, western bumblebee and white-tailed ptarmigan.

Wildlife migration corridor

The purpose of the West Vail Pass Auxiliary Lanes project is to improve safety and traffic flow on the highway, but the core values for the project include efforts to maintain existing terrestrial wildlife connectivity. Connectivity which, as researchers have learned over the years, is significant.

The nonprofit group Wildlands Network, which seeks to reconnect North America in an effort to reduce species extinctions, has identified Vail Pass as a priority wildlife corridor within the Western Wildway, a 6,000-mile corridor of somewhat-connected public lands between Mexico and Alaska.

Wildlands Network Conservation Director Greg Costello says Vail Pass is critical in promoting north-south migration into southern Colorado and Northern New Mexico.

Vail Pass has “always, historically, been a huge mixing ground of species, species from warmer climes and colder climes, a big mixing zone of biodiversity,” Costello told the Vail Daily.

That biodiversity brought Native Americans to the area nearly 7,000 years ago; evidence of Ute Indian hunting camps from 4800 B.C. were discovered on Vail Pass by archaeologists in 1975, where “Open meadows at the summit provided the Indians with a rich hunting ground,” writes Mary Ellen Gilliland.

Funding for more wildlife connectivity has always been difficult, but the grant will help ease CDOT’s burden in creating a project that could, if their goals are realized, not only reduce deaths, crashes and highway closures, but bring back some opportunity for different species to migrate between the very different environments of northern and southern Colorado.

“In the I-70 west Vail Pass project I think that there will be a large opportunity to increase connectivity, and to restore some of those historic migration corridors along Vail Pass,” said Cinnamon Levi-Flinn, a CDOT regional biologist. “The new project will have multiple crossing structures of various sizes, so we have a couple underpasses specifically for large mammals, and then we have about four or so medium-sized crossing structures for those smaller mammals to be able to cross.”

While the obvious goal of not hitting a deer on the freeway is always present in wildlife mitigation efforts, wildlife crossings can be important even in areas that don’t see much roadkill, said Jeff Peterson, CDOT wildlife program manager.

“You would expect a whole lot more roadkill than you’re getting out there,” Peterson said of Vail Pass. “That’s because it’s such a barrier, animals aren’t even attempting to cross it anymore. And when that happens, you’re restricting gene flow and population dispersal and increasing disease vulnerability, and ultimately reducing the population numbers by restricting movements and ability to find food, water, shelter, mating opportunities and things like that.”

The project includes six wildlife underpasses, along with wildlife fencing throughout the corridor.

Peterson said CDOT’s wildlife program is trying to look at the larger goal of habitat connectivity.

“If a highway, particularly a large one like I-70, is bisecting a quality habitat, it’d be a fair assumption that it’s also reducing or preventing wildlife from moving between those areas,” Peterson said. “So the way we’re approaching it is, you connect the habitat, and the wildlife movement will follow. In crossings like on Vail Pass, where there isn’t what appears to be a large wildlife-vehicle collision problem, we’ve determined that’s still an excellent place to put a crossing because of that habitat connectivity.”

Looking to be the leader

CDOT points to the State Highway 9 Colorado River South Wildlife & Safety Improvement Project, completed in 2016, as an example of the successful implementation of a habitat connectivity strategy. That project installed seven large wildlife crossing structures and 10.4 miles of wildlife exclusion fence between Kremmling and Green Mountain Reservoir in Grand County.

Using 62 motion-triggered cameras at 49 locations, a four-year study on the safety improvement project, published in March, documented 83,256 successful movements of mule deer as a project highlight.

“Success movements by elk, pronghorn, moose, bighorn sheep and white-tailed deer occurred in much lower numbers than mule deer but generally increased each year of the research,” the study noted. “These numbers reflect the relative proportion of these species in this landscape but are expected to continue increasing as more individuals learn to use the structures. The success rates for these ungulate species were 88% or greater in Year 4. … In winter 2018-19, for the first time, small herds of up to 17 elk were detected at the North Underpass. In each of these events, individuals were hesitant to use the structure but ultimately crossed through, suggesting that the elk were still adapting to the structure.”

The study documented a wide range of other species, as well.

“Overall success rates for all non-ungulate species documented at the wildlife crossing structures (including badger, black bear, bobcat, coyote, mountain lion, raccoon, red fox and striped skunk) ranged from 71% for badger up to 99% for black bear. In addition, river otter and turkey were detected successfully using the crossing structures for the first time in Year 4.”

Costello said increased efforts to create more wildlife connectivity across the country have been encouraging in recent years. The sheer visibility of certain projects, especially in Colorado, also has helped efforts in the Test.

“On the East Coast, we’ve got places that are really important for salamanders and turtles, but they don’t get the visibility,” he said.

In 2019, Gov. Jared Polis signed an executive order directing Colorado Parks and Wildlife, the Department of Natural Resources and the Department of Transportation to collaborate on migration patterns, regulatory and legislative opportunities for habitat conservation, safe wildlife passages that reduce wildlife-vehicle collisions, as well as education and outreach efforts to help teach the public about important migration areas.

CDOT director Shoshana Lew said the executive order is part of Colorado being a leader in the greater, nationwide issue to create migration corridors across the continent.

“I think that there’s a very heightened focus on this issue right now,” Lew said, referencing a Washington Post article from 2019.

“We’re obviously most focused on Colorado, as we should be, but it’s an issue where the best practices are developing a lot broader than just us, and frankly other parts of the country are looking to us as a leader on this,” Lew said.

Environmental assessment

Of course, the I-70 West Vail Pass Auxiliary Lanes project itself could create its own disturbances to wildlife, namely the one federally listed wildlife species which is known to inhabit the area, the Canada lynx. Approximately 150 acres of lynx habitat occur within the Project area.

“The Project may affect, and is likely to adversely affect, Canada lynx,” the project’s environmental assessment, which was published on Sept. 21, concludes. “This determination is based on the direct loss of winter forage, denning, and other habitat, increase in barrier effect and linkage area disturbance, light pollution, and likelihood of future lynx strikes resulting from the Project. The increase in barrier due to the wider highway footprint, avalanche mitigation, VMS cantilevers, lighting, glare screens, guardrails, bridge rails, and retaining walls have the potential to adversely affect lynx.”

Other sensitive species are known or suspected to use the area, as well, including American marten, Colorado River cutthroat trout, boreal owl, boreal toad, hoary bat, monarch butterfly, northern goshawk, northern leopard frog, pygmy shrew, olive-sided flycatcher, western bumblebee and white-tailed ptarmigan. Twenty bird species may occur in the study area, three of which are U.S. Fish and Wildlife Service birds of conservation concern: Golden Eagle, Peregrine Falcon and Williamson’s Sapsucker.

“Habitat loss, and physical and psychological barriers would continue to exist due to ongoing maintenance projects,” the assessment concludes.

Mitigation efforts include disallowing construction activities or equipment to work in flowing water or disturb sediment during recognized trout spawning seasons (March 1-May 31 for Cutthroat and Rainbow Trout) and Oct. 1-Nov. 30 (brown trout). Recommendations also include work be conducted during daylight hours as much as possible when lynx are less active “to avoid disrupting this nocturnal species foraging and travel behaviors,” according to the assessment. “For night work, concentrate the activity in as small an area as possible, and work for four consecutive nights separated by three consecutive nights of no work to allow any individuals in the vicinity to recover and potentially use the site for foraging or travel.”

The public comment period for the environmental assessment began on Sept. 22 and ends Oct. 21. Written comments can be submitted through the project website, by calling the project hotline (970-331-0200), or by email to, or by mail or to: John Kronholm, P.E. Colorado Department of Transportation P.O. Box 298 Eagle, CO 81631.


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