The Keystone XL pipeline would transport up to 830,000 barrels of oil per day from Morgan, Mont. to Steel City, Neb. About 85 percent of the oil would come from tar sands that extend across Manitoba, Saskatchewan, British Columbia and, especially, Alberta.
The process of removing that oil from tar sands and its use as an energy source could add as much as 93 million metric tons of carbon dioxide to the atmosphere each year, according to a Dec. 2013 report by the Stockholm Environment Institute.
A July 2013 report by the Natural Resources Defense Council concluded that, during a 50-year period, the pipeline could cause at least 1 billion more metric tons of the greenhouse gas to be pumped into the atmosphere than would be discharged without it.
The rest of the oil that would be transported by the pipeline would be drawn from the Bakken Shale Formation in western North Dakota.
Environmental advocacy organizations wasted little time before calling on Obama to reject the pipeline.
"Even though the State Department continues to downplay clear evidence that the Keystone XL pipeline would lead to tar sands expansion and significantly worsen carbon pollution, it has, for the first time, acknowledged that the proposed project could accelerate climate change," Susan Casey-Lefkowitz, the international program director for Natural Resources Defense Council, said in a statement. "President Obama now has all the information he needs to reject the pipeline."
Obama has said that he will not approve the Keystone XL pipeline if its construction would add to the problem of climate change.
The publication of the EIS is the latest step in an odyssey that has lasted for nearly six years. President Obama rejected the developer's first permit request in 2011 because of concerns about the impact on Nebraska's Sand Hills and its underlying aquifer. The proposed route was later changed, which necessitated both a new permit application and a new environmental impact review of the project.
A 2004 executive order by former President George W. Bush requires a presidential permit for oil and gas facilities that cross U.S. international borders.
The release of a supplemental environmental impact statement triggers a 30-day comment period, which will commence on Feb. 5. Once the deadline for submission of those comments passes, secretary of state John Kerry will make his recommendation about whether the White House should grant the presidential permit required to build the trans-national conduit for oil extracted from Canada's tar sands.
A coalition of environmental groups argued, in a Jan. 29 letter to Kerry, that the State Department needs to consider the cumulative climate change impacts of both the Keystone XL pipeline and the expansion of the nearby Alberta Clipper pipeline. That project would,if expansion is approved, carry about 880,000 barrels of crude per day. An amendment to an existing presidential permit is required for Enbridge, Inc., the developer of both pipelines, to increase the Alberta Clipper's capacity.
Construction of the southern half of the pipeline, which will carry oil from Cushing, Okla. to the Gulf of Mexico coast, has recently been completed.