Denali builds $230m bridge over moving landslide 5 years after road was cut

Pretty Rocks bridge (Image Credit: National Park Service)In August 2021, a massive landslide in Denali National Park and Preserve tore apart a section of the park's only road, cutting off vehicle access to destinations deep inside the Alaska wilderness. Five years later, a new bridge now spans the unstable ground where the road once crossed the slope. As reported by Alaska Public Media, the completion of the Pretty Rocks Bridge marks a major step toward restoring full use of the Denali Park Road. According to the National Park Service (NPS), the roughly $230 million project includes a 475-foot steel truss bridge built across the active landslide near Mile 45. The bridge reconnects the eastern and western portions of the road and is designed as a long-term solution rather than another attempt to keep rebuilding a roadway across moving ground. Full bus service to the western end is expected to return during the 2027 visitor season.The landslide that changed DenaliThe Pretty Rocks landslide forced the NPS to close the Denali Park Road in August 2021. The failure occurred in the Polychrome area, near Mile 45, disrupting access to some of the park's most important destinations west of the slide. Among the areas affected were the Eielson Visitor Center, Wonder Lake and Kantishna, along with residential, maintenance and privately operated tourism facilities. For several years, park buses could travel only as far as East Fork, around Mile 43. The problem was not simply a section of damaged pavement that could be repaired and reopened. The ground beneath the road remained unstable and continued moving, making repeated reconstruction of the roadway a difficult long-term solution.Building above moving groundInstead of building another road directly across the landslide, engineers developed a plan to span the unstable area with a bridge. The result is a steel truss structure approximately 475 feet long, 50 feet tall and 24 feet wide. It was designed to carry the park road across the active slide while avoiding direct reliance on the unstable ground underneath. The project presented unusual engineering challenges. Crews had to work in steep terrain with complex geology, permafrost and a short Alaska construction season. The remote location also made transporting equipment and completing construction more complicated than a conventional bridge project.A bridge assembled in AlaskaOne of the most striking parts of the project was how the bridge was put into position. Rather than building the entire structure across the landslide, crews assembled the bridge on the east side of the unstable area. In 2025, the completed structure was gradually launched across the slide toward the opposite side. The bridge reached the receiving tower in August 2025 and was subsequently lowered into its final position. NPS described the successful launch as one of the major accomplishments of that year's construction season. The structure also incorporates 23 thermosiphons, underground devices designed to help keep the permafrost beneath the eastern end of the bridge frozen. Maintaining stable ground around the bridge is an important part of ensuring its long-term performance.More than just a bridgeThe Pretty Rocks project involved more than constructing the main span. Crews also worked on road approaches, retaining structures and slope stabilisation. In 2026, workers completed additional construction around the bridge and carried out rock scaling on slopes in the Polychrome area to reduce the risk of unstable rock falling onto the road. A separate section near the Bear Cave landslide was also rerouted away from unstable ground. Construction was declared complete in late August 2026, with final restoration and removal of construction equipment continuing afterward.Access returns graduallyThe completed bridge does not mean every type of traffic immediately returned to the entire road. According to the National Park Service, hikers and cyclists can now travel west of East Fork and cross the new bridge, while park buses remain restricted to East Fork for the rest of the 2026 season. Full bus service along the Denali Park Road will resume in 2027. That reopening will restore access to the western reaches of Denali that have been difficult or impossible for many visitors to reach since the 2021 landslide.A long-term solutionThe Pretty Rocks Bridge represents a major change in how Denali's unstable terrain is being managed. Instead of repeatedly trying to hold a road in place across an active landslide, engineers built a structure that passes over the moving ground. The approximately $230 million project was funded through a combination of federal transportation, disaster supplemental and infrastructure funding. Five years after the Pretty Rocks landslide disrupted Denali's only road, the new bridge provides a connection across the unstable slope. Its completion marks the end of one of the park's most challenging infrastructure projects and sets the stage for visitors to once again travel farther into Denali beginning in 2027.