Structural issues caused by “bending stress on the pipe” and “a weld flaw” are to blame for the Keystone Pipeline’s oil spill in rural northern Kansas earlier this winter, according to pipeline operator TC Energy.
Just over two months after the spill, the Canadian company released the results of a mechanical analysis on the failed pipe on Thursday.
“The weld flaw led to a crack that propagated over time as a result of bending stress fatigue, eventually leading to an instantaneous rupture,” the company wrote in a press release.
TC Energy also revised its estimated spill volume to 12,937 barrels of oil — slightly lower than the 14,000 barrel estimate it initially released. The new volume is equal to around 543,354 gallons.
The spill is still the largest in the pipeline’s history, and larger than all of its previous spills combined.
The Star previously reported that the section of the pipeline connected to the spill was removed in December, several weeks after the spill occurred. No photos of the impacted pipeline segment have been released so far by TC Energy or regulators like the EPA.
“Such avoidance of pictures unfortunately is becoming more frequent in too many pipeline ruptures,” said Richard Kuprewicz, an independent pipeline advisor who has testified before Congress on pipeline safety and has over 20 years of experience advising on pipeline operation and regulation.
TC Energy said that it is decreasing the pressure inside the pipeline and investigating other spots where similar welding flaws may exist.
Government records show that certain sections of the pipeline have been operating at an above-standard pressure since 2017, but it is unknown whether the impacted section of the pipeline was one of them. TC Energy said that a high pressure was not responsible for the spill.
“The pipeline was operating within its operational design and within the pipeline design maximum operating pressure,” the company said. “The… analysis identified no issues with the strength or material properties of the pipe or manufactured fitting.”
The EPA is overseeing the ongoing cleanup of Mill Creek from the spill.
