ABC News
A spill of more than 500,000-gallons of crude oil from the Keystone Pipeline in December in Kansas was caused by a combination of a faulty weld and "bending stress fatigue" on the pipe, the conduit's operator announced Thursday. TC Energy, the pipeline's Canadian operator, said the cause was determined by an independent lab analysis on the failed section of the 2,687-mile conduit. "Although welding inspection and testing were conducted within applicable codes and standards, the weld flaw led to a crack that propagated over time as a result of bending stress fatigue, eventually leading to an instantaneous rupture," TC Energy said in a statement.