Embankment Fill Slope Movement on Thaw Sensitive Permafrost: Movement Mechanisms and Thermal Conditions at Lost Creek along the Trans-Alaska Pipeline System; Lost Creek—Part 1

The Trans-Alaska Pipeline System was constructed in the 1970s to transport oil through a 48-inch diameter pipeline (mainline) 800 miles from Prudhoe Bay to Valdez, Alaska. The system traverses continuous and discontinuous permafrost and is supported above-ground or buried, depending on permafrost and ground conditions. The Lost Creek site is in discontinuous, warm permafrost on a northwest-facing cut and fill slope. On the lower portion of the slope, fill was placed over frozen colluvium and ice-rich peat. The mainline at this site is supported aboveground on H-type bents, which consists of two piles supporting a crossbeam on which the pipe is supported. Since 1990, Alyeska Pipeline Service Company has observed signs of ground and pile movement. This paper presents our interpretation of geotechnical site conditions based on instrumentation monitoring and field observations. We developed mitigation options to control ground movement and present our approach in a separate paper within these proceedings.