A review of data collected by an inertial pigging tool found that a short section on the Norman Wells Pipeline had experienced an increase in internal diameter, which suggested that the pipeline had experienced a localized wrinkle.

Slope and pipeline instrumentation was installed at the site during an investigative dig and was monitored for one year before the wrinkled section was excavated and replaced. Following pipe replacement, additional slope indicators were installed, along with thermistor cables to monitor the performance of the slope.

The slope indicators indicate that some “creep-like” movement was taking place. Numerical modeling of potential loading mechanisms showed that a combination of deep burial, thaw settlement and mass movement of the soil could strain the pipe to the point of yielding.

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