Polychrome Pass Bridge: Innovative Geotechnical and Structural Solutions for Remote Infrastructure Rehabilitation in Denali National Park-PPT Presentation

PPT Presentation

Pdf Summary

The Polychrome Pass Bridge project addresses a major landslide in Denali National Park, where warming ice-rich permafrost caused ground movement to accelerate dramatically—from periodic maintenance needs to as much as five feet per month in 2020. The movement forced the park road to close in 2021, disrupting access to half the park and affecting tourism and Alaska’s economy.<br /><br />The remote site presented severe construction constraints, including limited work areas, challenging geology, environmental requirements, and ongoing slope movement. The project team adopted a Construction Manager/General Contractor (CMGC) delivery approach to coordinate design and construction under an accelerated schedule and uncertain ground conditions.<br /><br />The 475-foot bridge required extensive geotechnical work to stabilize its abutments and support construction. Permanent measures included soil nails, anchors, micropiles, and thermosyphons. For the bridge launch, engineers first developed a conservative temporary micropile design, then conducted instrumented load tests to refine it. The resulting design used 34 piles across six bents, fewer than initially anticipated.<br /><br />The bridge was launched as a cantilever over temporary foundations and reached its touchdown point on July 25, 2025. Final deflection was within four inches of the modeled value, which was within tolerance. Roadway and civil work, along with restoration of staging areas, was scheduled for 2026.<br /><br />Key lessons include the value of early contractor involvement, on-site engineering and testing in remote settings, flexible temporary works, and continued monitoring and planning for ground movement throughout construction.

Keywords

Polychrome Pass Bridge

Denali National Park

landslide

permafrost thaw

bridge launch

geotechnical engineering

micropiles

thermosyphons

CMGC delivery

road closure