Aan oil spill from the Belle Fourche Pipeline that was discovered Dec. 5, 2016 in Ash Coulee Creek, a tributary of the Little Missouri River, near Belfield, N.D. Authorities say the pipeline spill is now believed to be one of the biggest in state history. (Scott Stockdill/North Dakota Department of Health via AP)

North Dakota Oil Pipeline Spill 3 Times Larger Than First Estimated

About 530,000 gallons of oil is now believed to have spilled from the Belle Fourche Pipeline that was likely ruptured by a slumping hillside about 16 miles northwest of Belfield in Billings County, North Dakota.