Expert Report

Spills of Diluted Bitumen from Pipelines: A Comparative Study of Environmental Fate, Effects, and Response (2015)

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The U.S. Department of Transportation (DOT) needs to modify its regulations and planning in order to strengthen preparedness for accidental spills of diluted bitumen from pipelines. Diluted bitumen is a type of crude oil made from bitumen extracted from tar sands. While immediately following a spill, diluted bitumen behaves similarly to other crude oils, exposure to the environment induces rapid physical and chemical changes known as "weathering" that are unique to diluted bitumen. Within days, diluted bitumen starts to turn into a heavy, viscous, sediment-laden residue that cannot easily be recovered using traditional response techniques. The residue has a strong tendency to adhere to surfaces, and it poses particular challenges if it is spilled into a body of water, because the residues can submerge or sink to the bottom. Currently, the regulations and practices of DOT's Pipeline and Hazardous Materials Safety Administration (PHMSA) do not take the unique properties of diluted bitumen into account, nor do they encourage effective planning for spills of diluted bitumen. A more comprehensive and focused approach is needed to improve preparedness for spills of diluted bitumen and to spur more effective cleanup and mitigation measures when spills do occur.