In March 2019, snow melt and heavy rainfall resulted in major flooding at one of Enbridge’s (Company) pipeline river crossings. Based on an earlier hydrotechnical assessment, it was identified that the estimated scour in the river channel during a flood event of this magnitude could have the potential to create a pipe span of length where vortex induced vibration (VIV) may be initiated, potentially causing pipe failure and product release. As a precautionary measure, the Company shut down and isolated the pipeline; the two mainline block valves on either side of the river were closed for several days. This un-planned pipeline shut down impacted customers and resulted in revenue loss. An extended shutdown period would have also impacted downstream refineries. In order to promptly restart of the pipeline, bathymetric surveys (measuring the depth of a water body as well as mapping the river bottom profile and the underwater features of a water body) were performed in high flow conditions to verify the pipeline burial condition.
This crossing had been identified in the Company’s long range forecast with a planned remediation completion in 2020. However, the potential residual threat to the integrity of the pipeline due to high flow events existed until the remediation could be completed. Consequently, Company Pipeline Integrity group had been closely monitoring this crossing.
The Company’s Pipeline Integrity (PI) Department is on the journey to become a High Reliability Organization (HRO) where there is a strong preoccupation with failure and emphasis on determining the root cause of an incident, with the goal of striving for error free performance. As such, this incident was treated with as much emphasis as a pipeline failure, and several lessons learned from this incident were identified.
This paper will discuss the enhancements made to the Company’s flood monitoring program, including the incorporation of the flood forecast monitoring into the flood monitoring program, identification of high priority crossings, development of purge plan, utilization of new technology for surveying during flooding and the development of a flood response guideline.