A break in the Keystone pipeline leaked about 383,000 gallons of oil- half the size of an Olympic swimming pool- in northeastern North Dakota, pipeline owner TC Energy said Thursday.
The leak was detected at 9:20 p.m. Tuesday when the company noticed a drop in pressure in the line and shut it off , TC Energy officials said. The company has not determined the cause.
The affected area in Walsh County near Edinburg is about 2,500 square yards, or roughly half the size of a football field.
Regulators from the North Dakota Department of Environmental Quality and federal agencies, including the National Response Center and the Pipeline and Hazardous Materials Safety Administration, are at the scene Thursday to assess the damage.
The pipeline was activated in 2010 as part of the Keystone system. It extends from the tar sands of Alberta, Canada, through North and South Dakota, and hits a junction in Steele City, Neb. The oil supplies a refinery in Illinois.