Presentation Title: Connectivity and Safety in the I-25 South Gap: The Greenland Wildlife Overpass
Presenters: Chuck Attardo, David Herzog, Greg Marcuson - Colorado Department of Transportation and Christopher Russell - Shannon & Wilson
Agencies & Partners: Colorado Department of Transportation (CDOT), Colorado Parks and Wildlife (CPW), Douglas County, Federal Highway Administration (FHWA), Colorado Cattlemen's Agricultural Land Trust, and Douglas Land Conservancy
The Greenland Wildlife Overpass represents a landmark engineering and ecological mitigation effort situated within the Interstate 25 South Gap corridor between Castle Rock and Monument, Colorado. Historically, this 18-mile segment of I-25 acted as a significant barrier to wildlife movement, bisecting protected habitat and resulting in one of the highest rates of wildlife-vehicle collisions (WVCs) in the state. To address these challenges, the Colorado Department of Transportation constructed five wildlife underapasses and a dedicated wildlife overpass as the capstone of a broader wildlife mitigation system.
Spanning six lanes of interstate traffic, the wildlife overpass structure measures 200 feet in width and 209 feet in length, making it one of the largest wildlife overpasses in North America. Unlike traditional underpasses, which are highly effective for deer and smaller mammals, the Greenland Overpass was specifically engineered to accommodate high-sensitivity species such as elk and pronghorn. These species require open sightlines and naturalized terrain to feel secure during crossing. The bridge deck is landscaped with native vegetation and concrete barriers to dampen highway noise and light, creating a seamless extension of the surrounding environment.
Ecologically, the overpass restores vital connectivity between 39,000 acres of protected land on either side of I-25 and over one million acres of the Pike National Forest to the west. This reconnection is critical for vehicular safety, genetic diversity, seasonal movements, and the long-term viability of local big game herds.
Completed in early December 2025 at a cost of approximately $15 million, the project utilized funding from US DOT's Wildlife Crossings Pilot Program. Together with a network of associated underpasses and 8' wildlife exclusion fencing, the entire wildlife mitigation system is projected to reduce wildlife-vehicle collisions in the corridor by at least 91%, serving as a model for integrating transportation infrastructure with landscape-scale conservation.
Location
Setting: In-Person CDOT KOA Office Region 1 18500 E Colfax Ave Aurora, Co 80011 UNITED STATES
