Native Americans from different tribes participate in a rally outside US District Court in Washington, Wednesday, Aug. 24, 2016, in solidarity with the Standing Rock Sioux Tribe in their lawsuit against the Army Corps of Engineers to protect their water and land from the Dakota Access Pipeline. A federal judge in Washington considered a request by the Standing Rock Sioux for a temporary injunction against an oil pipeline under construction near their reservation straddling the North Dakota-South Dakota border. (AP Photo/Manuel Balce Ceneta)

Native Americans from different tribes participate in a rally outside US District Court in Washington, Wednesday, Aug. 24, 2016, in solidarity with the Standing Rock Sioux Tribe in their lawsuit against the Army Corps of Engineers to protect their ... water and land from the Dakota Access Pipeline. A federal judge in Washington considered a request by the Standing Rock Sioux for a temporary injunction against an oil pipeline under construction near their reservation straddling the North Dakota-South Dakota border. (AP Photo/Manuel Balce Ceneta) (The Associated Press)

Oil pipeline: The legal challenges and protests

Markets Associated Press

A federal judge has heard testimony in the Standing Rock Sioux Tribe's request to temporarily block the construction of a four-state oil pipeline near their reservation, which straddles the North Dakota-South Dakota border.

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Some things to know about the pipeline and the tribe's ongoing protest:

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WHAT IS THE DAKOTA ACCESS PIPELINE?

Dallas-based Energy Transfer Partners' Dakota Access Pipeline is a $3.8 billion, 1,172-mile project that would carry nearly a half-million barrels of crude oil daily from North Dakota's oil fields through South Dakota and Iowa to an existing pipeline in Patoka, Illinois, where shippers can access Midwest and Gulf Coast markets.

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WHAT IS THE LAWSUIT TARGETING?

The Standing Rock Sioux Tribe sued federal regulators for approving the oil pipeline, challenging the U.S. Army Corps of Engineers' decision to grant permits at more than 200 water crossings and arguing that the pipeline would be placed less than a mile upstream of the reservation, potentially impacting drinking water for more than 8,000 tribal members and millions of people who rely on it further downstream.

The lawsuit, filed on behalf of the tribe by environmental group Earthjustice, said the project violates several federal laws, including the National Historic Preservation Act. The tribe also worries the project will disturb ancient sacred sites outside of the 2.3-million acre reservation.

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IS THE PIPELINE SAFE?

The company said the pipeline would include safeguards such as leak detection equipment, and workers monitoring the pipeline remotely in Texas could close block valves on it within three minutes if a breach is detected.

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WHO ARE THE PROTESTERS?

Mostly members of the Standing Rock Sioux tribe, but they've been joined by other American Indians and non-Native Americans from across the country. "Divergent" actress Shailene Woodley was part of the protests last week, and actress Susan Sarandon was at Wednesday's federal hearing.

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HOW MANY ARRESTS HAVE THERE BEEN?

For months, there has been a nonviolent tribal protest at a "spirit camp" at the confluence of the Cannonball and Missouri rivers in the path of the pipeline. More than a dozen young people from the reservation also ran to Washington to deliver 140,000 petition signatures to the Corps to protest the pipeline.

But the protest recently became heated, and more than two dozen have been arrested and charged with interfering with the pipeline construction, including Standing Rock Sioux Tribal Chairman David Archambault II.

Gov. Jack Dalrymple declared an emergency last week to make more state resources available to manage public safety risks from the protest. He said that the state is committed to protecting lawful assembly rights, but says unlawful acts have led to "serious public safety concerns."

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ARE THERE PROTESTS IN OTHER STATES?

Yes, but nothing like in North Dakota. Construction equipment at several sites in Iowa was set on fire earlier in August, causing more than $1 million in damage. And Iowa landowners who are upset over the state utilities board allowance of eminent domain have sued and are waiting for that challenge to be heard.

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WHY IS IT BEING BUILT?

Energy Transfer Partners announced the Dakota Access pipeline in 2014, a few days after Dalrymple urged industry and government officials to build more pipelines to keep pace with the state's oil production, which is second only to Texas'.

Supporters said the pipeline would create more markets and reduce truck and oil train traffic — the latter of which has been a growing concern after a spate of fiery derailments of trains carrying North Dakota crude, including one near Dalrymple's hometown of Casselton in 2013, and an explosion in Quebec that same year that killed 47 people.