The Department of Transportation has launched an investigation in Kansas after a rupture in the Keystone pipeline caused a massive oil spill 160 miles north of Wichita. The pipeline’s operator, TC Energy — formerly known as TransCanada — estimated some 588,000 gallons of oil spilled into a natural waterway. That’s nearly enough to fill an Olympic-sized swimming pool. It’s the largest U.S. crude oil spill in nearly a decade, and the worst in the history of the Keystone pipeline, which carries oil from Canada’s tar sands to refineries in Illinois and the Gulf Coast.