A major transportation project in one of Alaska’s most challenging environments has reached completion, restoring a key connection through Denali National Park after a landslide forced the closure of part of the road in 2021.
Granite Construction completed the Polychrome Pass Bridge after five years of planning, engineering and construction. The project provides a permanent crossing over the active Pretty Rocks Landslide and reconnects the eastern and western sections of Denali Park Road.
The 475-foot bridge uses a single-span steel truss configuration to carry traffic above the unstable slope. Its foundations and associated slope stabilization systems were developed to address continuing ground movement and seismic conditions at the site.
The location presented additional challenges because of ice-rich permafrost and the environmental sensitivity of Denali National Park. Project teams incorporated geotechnical investigations and ongoing monitoring into the engineering and construction process.
A key component of the project is a passive thermosiphon system installed beneath the bridge’s eastern abutment. The technology removes heat from the ground to help maintain frozen permafrost conditions throughout the year.
The approach was incorporated into the foundation design to address the effects that changing ground temperatures could have on the bridge. The project also required coordination around the active landslide, seismic considerations and protection of the surrounding landscape.
Granite Construction and its project partners used a CM/GC delivery model, allowing construction and design teams to work together on risk identification and technical solutions during project development.
With the bridge now complete, road access beyond the Pretty Rocks Landslide has been restored. The new crossing provides transportation infrastructure designed for the site’s geological and climatic conditions while reducing the need for continued reliance on the closed roadway section.
The Polychrome Pass Bridge demonstrates how transportation infrastructure can be designed for locations where conventional foundation and construction methods face significant geological and environmental constraints.
For transportation owners and contractors, the project highlights the use of single-span bridge construction, slope stabilization, geotechnical monitoring and passive permafrost protection in a remote setting. Restoring the Denali Park Road connection also reestablishes access to destinations on both sides of the landslide, creating a long-term transportation link within the national park
Source: Granite Construction.
