BISMARCK — The American Indian tribe leading a federal lawsuit to try to shut down the Dakota Access Pipeline on Friday, Aug. 16, filed what amounts to its final legal argument in the three-year-old case.

The document filed by Earthjustice attorney Jan Hasselman on behalf of the Standing Rock Sioux asks U.S. District Judge James Boasberg to rule in favor of the tribes and order more environmental study of the $3.8 billion pipeline that’s been moving North Dakota oil to Illinois for more than two years.

“This illegal and dangerous pipeline must be shut down,” Standing Rock Chairman Mike Faith said in a statement.

Standing Rock and three other Sioux tribes in the Dakotas fear a pipeline spill into the Missouri River would contaminate water they rely on for drinking water, fishing and religious practices. Thousands of pipeline opponents from around the world who took up their cause flocked to southern North Dakota in 2016 and 2017 to protest the project. Some clashed with police, resulting in 761 arrests in a six-month span.

Texas-based pipeline developer Energy Transfer maintains the pipeline is safe, and the U.S. Army Corps of Engineers, which permitted the project, determined it does not pose a higher risk of adverse impacts to minorities.

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Boasberg in June 2017 ordered more study on that topic. The Corps completed the work last fall and said it substantiated the agency’s earlier conclusions.

Hasselman in his Friday filing called the additional study “a sham from its inception.” He asked Boasberg to order even more study and shut down the pipeline in the meantime.

“This court gave the Corps a second chance to fix ‘significant’ flaws in its initial findings,” Hasselman wrote. “Instead, (the process) only uncovered more problems.”

The Corps and Energy Transfer have until Nov. 20 to file their final arguments. Boasberg will then decide at a later date whether to order even more study. Should he decline, the tribes are likely to appeal. The lawsuit has lingered since July 2016.

Energy Transfer earlier this summer announced a $40 million effort to nearly double the pipeline’s capacity to meet demand from shippers. The expansion would be done through an increase in horsepower — not additional pipeline — but tribes still oppose it. The Standing Rock Sioux has asked North Dakota regulators to hold a hearing on the matter.

“With DAPL’s proposal to double the flow of the pipeline, the unexamined risks to the tribe continue to grow,” Hasselman said in his Friday filing.