The Kalamazoo River oil spill occurred in July 2010 when a pipeline operated by Enbridge (Line 6B) burst and flowed into Talmadge Creek, a tributary of the Kalamazoo River. A six-foot break in the pipeline resulted in the largest inland oil spill, and one of the costliest spills, in U.S. history. The pipeline carries diluted bitumen (dilbit), a heavy crude oil from Canada's Athabasca oil sands to the United States. Following the spill, the volatile hydrocarbon diluents evaporated, leaving the heavier bitumen to sink in the water column. Thirty-five miles of the Kalamazoo River were closed for clean-up until June 2012, when portions of the river were re-opened.