South Bow Shares Findings of Root Cause Analysis of Milepost 171 Incident

Independent analysis identifies unique circumstances leading to pipeline failure

Published on Feb. 14, 2026

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South Bow Corp. and the Pipeline and Hazardous Materials Safety Administration (PHMSA) have received the independent third-party root cause analysis (RCA) of the incident that occurred at Milepost 171 (MP-171) of the Keystone Pipeline on April 8, 2025, near Fort Ransom, N.D. The RCA identified that the failure resulted from a fatigue crack that originated along the pipe's manufactured long-seam weld, with the seam weld geometry being a primary contributor. South Bow is actively progressing its remedial actions, including in-line inspection runs and integrity digs, and will continue to work closely with its vendors to advance tool performance and validation.

Why it matters

The MP-171 incident highlights the importance of pipeline safety and the need for continuous improvement in inspection and maintenance practices. As a major operator of crude oil pipelines in North America, South Bow's response and actions in addressing the root causes will be closely watched by regulators, industry peers, and the public.

The details

According to the RCA, the pipe and welds conformed to industry standards, and the pipeline was operating within its design pressure at the time of the incident. The RCA identified that the failure resulted from a fatigue crack that originated along the pipe's manufactured long-seam weld, with the seam weld geometry being a primary contributor. Multiple in-line inspections had previously been completed on the section of pipe, but the presence of hydrogen contributed to material brittleness and increased the growth rate of the fatigue crack.

  • The incident occurred on April 8, 2025, near Fort Ransom, N.D.
  • South Bow has completed seven in-line inspection runs and 51 integrity digs to date as part of its remedial actions.

The players

South Bow Corp.

A Calgary-based company that safely operates 4,900 kilometres (3,045 miles) of crude oil pipeline infrastructure, connecting Alberta crude oil supplies to U.S. refining markets.

Pipeline and Hazardous Materials Safety Administration (PHMSA)

The federal agency responsible for regulating and overseeing the safety of pipelines in the United States.

Bevin Wirzba

The chief executive officer of South Bow Corp.

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What they’re saying

“This was a complex set of unique circumstances. We are committed to learning from this incident and are already implementing remedial measures and enhancements across our systems to prevent future incidents.”

— Bevin Wirzba, Chief Executive Officer, South Bow Corp. (South Bow Corp. press release)

What’s next

South Bow has submitted its remedial work plan to PHMSA for approval, which includes the corrective actions already completed and addressing the RCA recommendations. The company will continue to work closely with its in-line inspection technology vendors to advance tool performance and validation, address and resolve tool limitations, and develop new technologies. Additional in-line inspection tool runs and integrity digs are scheduled for 2026 as part of South Bow's comprehensive program to address the findings and recommendations from the RCA investigation.

The takeaway

This incident highlights the importance of continuous improvement in pipeline safety and the need for operators to work closely with regulators, vendors, and the public to address complex issues and implement robust remedial measures. South Bow's commitment to transparency and its proactive approach to addressing the root causes of the MP-171 incident are crucial steps in maintaining public trust and ensuring the safe and reliable operation of critical energy infrastructure.