Pretty Rocks Landslide

LOCATION: Denali National Park, Alaska

The Denali Park Road is a 92-mile-long out-and-back road that heads west from the park entrance near Healy, Alaska to Kantishna, an outpost within the heart of Denali Park. In the summer of 2021, a segment of the Denali Park Road through the Polychrome Pass area was cut off by the downslope movement of the Pretty Rocks Landslide near Mile 45, preventing travel further west. The complexity of the geology, climate, permafrost, and seismic hazards present a unique challenge for developing a solution to reopen the Denali Park Road and regain access to the stunning landscape. BGC partnered with Jacobs Engineering and Western Federal Lands Highway Division to facilitate an Expert-based Risk Assessment (EBRA) to assess the long-term geotechnical risks to various alternative Denali Park Road alignments in 2020. BGC performed site investigations in 2021 and 2022 which included structural geologic mapping, helicopter-access drilling investigations, surface and downhole geophysical surveys, and installation of remote monitoring units to transmit real-time borehole instrumentation data. BGC is currently in the design phase of the project which involves the development of a 3D geological and engineering site model, kinematic analyses, slope stability analyses, rock cut design, probabilistic seismic hazard assessment, bridge foundation soil-structure interaction analysis and design, retaining wall design, and thermal modelling and design.