Pipeline opponent Bold Nebraska joined the Sierra Club, the Natural Resources Defense Council, tar sands opponent Oil Change International and others in demanding the U.S. State Department conduct another environmental review.
The State Department in early 2013 published its draft environmental assessment of the pipeline proposed to deliver 830,000 barrels of tar sands oil from Canada to southern U.S. refineries.
Opponents of Keystone XL are concerned about the high-level of emissions associated with tar sands production and the perceived likelihood of pipeline corrosion.
A study published this week by the U.S. National Research Council dispelled concerns about the corrosive nature of tar sands.
The advocacy groups petitioning the State Department said Thursday they want to see more details on climate impacts associated with tar sands production. Their 48-page letter to the State Department points to a series of reports critical of tar sands, including an April report from the Environmental Protection Agency saying carbon emissions were downplayed in the original report from this year.
The State Department's initial review said climate concerns associated with tar sands would be present with or without the pipeline. President Obama said he would weigh the project against its environmental footprint.