PS 5 Sewage Lagoon Embankment Stabilizationby Keith Mobley, Golder Associates Inc, Anchorage, United States,
James C. Harle, Golder Associates Inc, Anchorage, United States,
Abstract: In 1981 an embankment containing a three-cell wastewater treatment lagoon was constructed adjacent to the northern edge of the Pump Station 5 gravel pad on the Trans Alaska Pipeline System. Since construction, a variety of problems related to settlement of the lagoon embankment have occurred. A soils investigation, conducted in June 1989, and readings from thermistor strings installed at the same time indicated the thaw front was continuing to progress downward and was, at that time, located at the top of a massive ice lens at least 6.5 meters thick. To control the thaw front progression, thermosyphon cooling units were installed beneath the lagoon ponds. Thermosyphons were also installed beneath 10 cm of polyurethane insulation to remove heat from the toe of the embankment and to control heat inflow. These thermosyphons were placed along the toe of the embankment at a 2° slope up toward the cooling fins. Two thermistor strings installed prior to construction of the thermosyphons have been monitored to determine the effectiveness of the thermosyphon heat removal. Thermal monitoring will continue for at least one full year to track thawing and freezeback.
Subject Headings: Lagoons | Sewage | Heat treatment | Freeze and thaw | Heat transfer | Construction management | Pumping stations | Temperature effects | North America | Alaska | United States
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