A Weld Passed Inspection in 2010. It Ruptured 12 Years Later.

On November 19, 2010, a girth weld on the Keystone Cushing Extension pipeline in Kansas was radiographed and passed inspection, per PHMSA's failure investigation report⧉.▸ Twelve years later, on December 7, 2022, that same weld ruptured, releasing an estimated 12,937 barrels of crude oil -- most of it into Mill Creek in Washington County, Kansas. The Justice Department⧉ calls it one of the largest inland oil spills in recent U.S. history, and the largest ever from the Keystone Pipeline system. PHMSA's investigators later found the crack that caused the rupture started at a defect that standard radiography is known to miss when it runs parallel to the pipe wall -- which is exactly how this one ran.

The failed fitting was fabricated in a Houston shop in 2010, part of a warranty-replacement program that swapped out 70 undersized elbow fittings across the Cushing Extension after a hydrostatic test found their steel didn't meet strength specifications.▸ The replacement weld was radiographed before burial and passed. It sat undisturbed for over a decade until PHMSA's post-rupture metallurgical exam found internal root-pass weld repairs with lack-of-fusion defects -- and confirmed that a second radiograph, taken at the lab after the accident, still didn't catch them. Only ultrasonic phased-array testing, run after the pipe had already failed, found the flaw. PHMSA attributes the bending stress that eventually cracked the weld to inadequate soil compaction during the same 2010 repair: the backfill spoil pile sat exposed to freezing temperatures for several days, and TC could produce no site-specific records showing the backfill had been inspected before burial.

Cleanup crews grew nearly sevenfold in six weeks -- from 119 contract personnel four days after the rupture to 785 at the response's late-January peak, per EPA pollution reports cited in PHMSA's investigation⧉.▸ Benzene from the spilled diluted bitumen passed an underflow dam built to contain it and reached the water column downstream; clams were found dead as far as five miles past the dam. Sediment cleanup of Mill Creek itself wrapped in May 2023, but full remediation of the spill site wasn't finished until February 2024, per the Clean Water Act consent decree⧉ South Bow signed this month -- roughly 14 months after the creek bed itself was clean.

PHMSA's own accounting puts the total cost of the incident -- cleanup, remediation, response, and related expenses -- at $600,793,659.▸ On July 10, 2026, the EPA, Justice Department, and State of Kansas announced⧉ the settlement of the resulting Clean Water Act case: a $26,867,789 civil penalty to the federal Oil Spill Liability Trust Fund, due within 30 days, plus $3,080,000 South Bow will spend on Kansas-approved natural-resource restoration projects over the next three years -- $29.9 million combined. South Bow separately estimates it will spend about $40 million complying with new prevention and detection requirements the settlement imposes, money spent on future compliance rather than a payment for what already happened. "The oil spill blanketed land and water, rendering the waterway lifeless and useless,"⧉ EPA's Jeffrey A. Hall said announcing the deal.