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

Executive Summary

• South Bow and PHMSA released the independent third‑party root cause analysis (RCA) for the April 8, 2025 incident at Milepost 171 on the Keystone Pipeline.
• The RCA identified a fatigue crack originating in the pipe’s long‑seam weld, exacerbated by hydrogen‑induced brittleness, as the primary failure mechanism.
• South Bow is executing an extensive remedial program—including seven additional inline inspection runs and 51 integrity digs—to address the findings and satisfy PHMSA’s Corrective Action Order.

Key Details

• Incident Background: Occurred on April 8, 2025 at MP‑171 (near Fort Ransom, ND). Pipe and welds met industry design, material, and mechanical standards; pipeline was operating within design pressure.
• Root Cause Findings:
• Fatigue crack initiated along the manufactured long‑seam weld.
• Seam‑weld geometry created a stress concentration that likely started the crack during transportation from the pipe mill.
• Multiple prior inline inspections (three generations of ultrasonic shear‑wave technology, two vendors) did not detect the defect.
• Presence of hydrogen contributed to material brittleness and accelerated crack growth over ~15 years of operation.
• Remedial Actions Completed:
• Seven additional inline inspection runs performed.
• 51 integrity digs completed with no injurious issues identified.
• Planned Remediation (2026): Additional inline inspection tool runs and further integrity digs scheduled as part of a comprehensive program addressing RCA recommendations.
• Regulatory Process: South Bow submitted a remedial work plan to PHMSA under the Corrective Action Order; the plan incorporates completed actions and outlines future steps.
• Technical Enhancements: Modified inspection process now overlays data from previous tool runs and improves data‑analysis methods; ongoing collaboration with vendors to advance tool performance, resolve limitations, and develop new technologies.
• Forward‑Looking Statements: Include expectations that PHMSA will approve the CAO remediation plan, continued improvements in inspection tools, and that South Bow will maintain safe, reliable Keystone Pipeline operations.

Notable Quotes

“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, CEO, South Bow Corp.

Materiality Assessment: Material – Neutral (the disclosure provides significant operational and safety information that could affect stakeholder perception of pipeline integrity, though no immediate financial impact is disclosed).