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 near Marshall, Michigan. A break in the pipeline resulted in one of the largest inland oil spills in U.S. history (the largest was the 1991 spill near Grand Rapids, Minnesota). The pipeline carries diluted bitumen (dilbit), a heavy crude oil from Canada's Athabasca oil sands to the United States. Cleanup took five years. Following the spill, the volatile hydrocarbon diluents evaporated, leaving the heavier bitumen to sink in the water column. of the Kalamazoo River were closed for clean-up until June 2012, when portions of the river were re-opened. On March 14, 2013, the Environmental Protection Agency (EPA) ordered Enbridge to return to dredge portions of the river to remove submerged oil and oil-contaminated sediment. The spill On Sunday, July 25, 2010, at about 5:58 p.m. EDT, a pipe segment ruptured in the Enbridge Energy Line 6B, approximately downstream of the Marshall, Michigan pump station. The rupture caused a spill of diluted bitumen originating from Canada (Alberta and Saskatchewan) into Talmadge Creek in Calhoun County, Michigan, which flows into the Kalamazoo River. The US Environmental Protection Agency (EPA) later estimated the spill to be in excess of . On 29 July 2010, the Calhoun County Health Department asked 30 to 50 households to evacuate, and twice as many were advised not to drink their water. Alarms sounded in Enbridge's Edmonton headquarters at the time of the rupture, but control-room staff were unable to interpret them with certainty and remained unaware of the pipeline breach. It was eighteen hours before a Michigan utilities employee reported spilt oil and the company learned of the escape. For much of that time the operators had shut down the pipeline, so that the bitumen mixture escaped comparatively slowly. But they had thought the alarms were possibly caused by a bubble, in the pipeline, causing anomalous pressure readings, and had twice restarted the line. For a few hours, in total, the material was escaping much faster. The oil was contained to a stretch of the Kalamazoo River as several hundred workers took part in the cleanup. Regional EPA Director Susan Hedman estimated that it would take weeks to remove the bulk of the oil from the river, several months to clear oil from the flood plains, and