Get Smart Fast: The Controversial Dakota Access Pipeline

The Dakota Access pipeline is a 1,172-mile pipeline beginning in northwestern North Dakota, crossing South Dakota, Iowa and terminating in Patoka, Illinois where it would connect with other pipeline systems. When fully operational, the pipeline would carry 470,000 barrels of oil a day.

The builder -- Energy Transfer Partners -- secured the required permits from the Army Corps of Engineers and started construction on the pipeline, which is 60 percent complete. The company estimates that more than $1.6 billion has been spent so far on the project.

However, the pipeline has garnered significant attention and controversy. Environmental groups argue that a pipeline accident could taint local water supplies. Native Americans, including the directly impacted Standing Rock Sioux, complained that the construction would disrupt sacred tribal sites.

Opponents sued in federal court to stop construction but a judge ruled against them September 9, stating that the government had followed the necessary procedures and that construction could continue.

Later that day, three Federal agencies -- the Department of Justice, the Department of the Interior, and the Corps of Engineers -- issued a statement that the federal government may need to revisit questions about tribal consultation and asked Energy Transfer Partners to "voluntarily pause" its construction.

It is unusual for a federal agency to reverse itself on a large infrastructure project that has been permitted and is under construction. But for now anyway, the Dakota Access pipeline is on indefinite hold.