The independent third-party root cause analysis report for the April 2025 Keystone pipeline spill in North Dakota has been made public. The incident, involving approximately 3,500 barrels of oil with 3,110 barrels recovered, was investigated by metallurgical specialist Anderson & Associates for the U.S. Pipeline & Hazardous Materials Safety Administration.

Root Cause of the Failure

The analysis concluded the pipe failure resulted from a fatigue crack that originated along the pipe's manufactured long-seam weld. A primary contributor was the specific geometry of that seam weld, which created a concentration of stress. This stress likely initiated the crack during transportation from the pipe mill, before the pipeline was even constructed or entered operation. The report noted the pipe, welds, and transportation all met industry standards, and the pipeline was operating within its design pressure at the time of the failure, making the circumstances unique.

Crack Propagation and Contributing Factors

The fatigue crack developed over the pipeline's 15 years of normal operation. The report suggested the presence of hydrogen contributed to material brittleness and accelerated the crack's growth rate, a process known as hydrogen-induced cracking. Possible hydrogen sources identified include corrosion, excessive cathodic protection, and welding. Prior to the failure, the pipe section had undergone multiple in-line inspections using advanced ultrasonic technology from different vendors.

Company Response and Remedial Measures

South Bow Corporation stated it is implementing measures to prevent a repeat. Remedial actions already undertaken include seven new in-line inspection runs and 51 integrity digs, with preliminary results showing no injurious issues. The company has modified its inspection process by overlaying data from previous tool runs and improving data analysis methods to address known tool limitations. It is also working with technology vendors to advance tool performance and develop new technologies. A remedial work plan has been submitted to PHMSA as required by a corrective action order.

Financial Impact

Costs linked to the spill totaled $55 million, which are largely expected to be recovered through insurance. The company has maintained its contractual commitment to transport 585,000 barrels per day.