The embankment has been creeping on a buried layer of frozen peat shear zone. The resulting slope movement has tilted and displaced the piles that support the pipeline, which requires continuous and expensive maintenance. Permafrost degradation is causing more rapid creep movement and could cause a rapid landslide when the peat shear zone thaws.

Shannon & Wilson designed new piles to replace those with excessive tilt and a thermal improvement system to cool the peat zone to stop the creep movement and prevent a rapidly moving landslide. The thermal improvement system consists of an array of free-standing heat pipe thermosyphons and surface insulation, which provides long-term cooling in a completely passive manner, requiring no moving parts, pumps, or supplied power of any kind. The woodchip surface insulation that prevents heat excessive heat gain during warm weather seasons is renewable and environmentally sustainable.

We were able to significantly reduce the number of thermosyphons and extent of woodchip surface insulation to cool and maintain permafrost even with the most severe climate warming scenario by using state of the art design methods. We re-analyzed our preliminary 2D thermal simulations using new, commercially available, 3D thermal finite element software. The Lost Creek project was the first application of the new software for designing thermal slope stabilization. This approach provided great benefits to Alyeska Pipeline Service Company, local communities, and the environment, including:

• 40% fewer thermosyphons, which resulted in significant cost savings and allowed construction to fit into one season instead of two.
• Smaller woodchip insulation area that does not encroach on the adjacent wetlands and creek.
• A more sustainable project with less material waste and shipping.
• A project savings of over $1 million.