Keystone Pipeline oil spill could be worse than we thought

An oil spill in South Dakota that leaked thousands of gallons of highly polluting oil could damage the environment more than the company has let on.

TransCanada shut down a portion of its highly contested Keystone Pipeline, which transports oil from the Canadian tar sands to refineries in the U.S., at 6 a.m. on Thursday after 210,000 gallons, or around 5,000 barrels, of oil spilled across South Dakota farmland. The type of oil in the pipeline, however, makes pinpointing the size of the spill more difficult than usual, worrying local environmental groups and landowners about its environmental effects.

The spill also comes just days before a crucial moment for the pipeline: Nebraskans will vote on Monday whether to approve the final step in the Keystone XL Pipeline, which would move 830,000 extra barrels of Canadian oil through the Midwest to refineries in Texas and Illinois.

A viscous type of oil called diluted bitumen, or tar sands oil, flows through the Keystone Pipeline. Because it’s so thick, leaks can be difficult to detect. If the oil does spill, it’s often far more detrimental to sensitive water resources. Bitumen is also one of the dirtiest fuels in the world. Unlike conventional crude which can be pumped directly from the ground, water is required to separate the heavy, tar-like substance from the sand it’s found in — a process that depletes and pollutes freshwater resources.