Alaska Repaving Roads Using Polystyrene Insulation
The Alaska Department of Transportation & Public Facilities (ADOT&PF) is rebuilding portions of roads in the northern regions of the state using a thick layer of insulation under the pavement in order to help prevent the thaw of underlying permafrost caused by heat transfer. Thawing permafrost, exacerbated by increasing average annual temperatures and heat transfer from paved roads, has caused structural instability to roadway infrastructure and buildings in Alaska. Portions of Goldstream Road near Fairbanks and the Dalton Highway further north are both being replaced with insulation board to ensure thermal stability of the roads with increasing temperatures under climate change scenarios.
The Goldstream Road project, which began in June 2013, involves tearing up existing portions of Goldstream Road and placing four-inch thick sheets of polystyrene foam insulation five feet below the road surface. Permafrost thaw is threatening the structural integrity of Goldstream Road, which has previously experienced sinking and instability due to heat transfer from the roadway, causing foundation soils to thaw and heave. The insulation will help prevent heat transfer. Foam insulation accounts for $2 million of the nearly $17 million overall project cost. The added cost of the foam insulation is designed to reduce repair costs over time. The road is also being constructed with geotextile fabric in between the insulation and the road surface in order to reduce erosion and further improve road stability.
ADOT&PF is also designing a portion of the Dalton Highway on the coastal plain north of the Brooks Range to include insulation board. As temperatures warm, road embankments will need to be thicker to prevent underlying permafrost layers from thawing. ADOT&PF engineers used the TEMP/W program to model different road embankment heights with and without insulation, and determined that the redesigned road would require insulation board in order to be thermally stable even under current conditions. The engineers then tested the final proposed design to ensure thermal stability under possible future scenarios with higher temperatures.
This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on February 6, 2015.
Publication Date: 2013
- Alaska Department of Transportation and Public Facilities
- Case study
- Air temperature
- Permafrost melt