The 414-mile road from Fairbanks, Alaska, to the frozen tundra of North America's largest oil field is remote and rugged with hills steep as roller coasters, polar bears nearby and wild weather featured regularly in History Channel episodes of “Ice Road Truckers.”
Known locally as the Dalton Highway, this sometimes-paved, often-graveled road is the lifeline to transport supplies from food to heating fuel to modular housing to the 213,543-acre oil field near the Arctic Ocean and the few towns north of the Arctic Circle.
When the Alaska Department of Transportation needed to repair the 50-mile leg that ends just shy of the oil field by Prudhoe Bay, it gave a green light to using block-molded expanded polystyrene as insulation in the roadbed.
A contractor is installing two layers of 2-inch-thick EPS as part of the base for a gravel-surfaced section of the highway, which dates back to 1974 and originally serviced construction of the Trans-Alaska Pipeline. The insulation serves two purposes, according to Monte Hagerty, plant manager at a facility in Anchorage that manufactured 4 million cubic feet of InsulFoam 40-brand EPS for the project. The product keeps the permafrost frozen for stability and raises the roadbed above the flood level, Hagerty told Plastics News.
Freeze-thaw cycles have taken its toll on the road reportedly traveled by some 200 tractor-trailer rigs a day. Though average temperatures there are below-freezing much of the year, summer usually brings highs in the 50s, and a wide range of temperatures from -62° F to 83° F have been recorded. Melting permafrost causes the highway to settle and buckle.
Another problem is due to major flooding in 2015 caused by the rapid melting of the Sag River. Overflow ice and a spring flood eroded parts of the road.
Hagerty said in an email that InsulFoam 40 addresses these problems by “banking cold” within the roadbed in winter to keep the permafrost frozen in summer and by providing a lightweight structural infill that lifts the roadbed above flood levels without overcompressing the underlying soils.
Traditionally, the only product that could meet the project standard in terms of thermal value, water absorption and compression was extruded polystyrene foam board, Hagerty said. However, the Insulfoam Anchorage plant has “specialized manufacturing equipment” that produces EPS boards that meet standards of the American Association of State Highway and Transportation Officials. Hagerty said he could only identify the equipment as a block molding machine for proprietary reasons.
He described the InsulFoam 40 product it forms as a “high-performance insulation consisting of a superior closed-cell, lightweight and resilient EPS, manufactured in a plank mold.”
Road crews have installed plenty of the product to date for the project, which is scheduled for completion in 2019.
“Picture a football field stacked about 70 feet high with insulation,” Hagerty said of the volume manufactured so far.