BISMARCK — The U.S. Army Corps of Engineers properly handled a judge’s order to further study the Dakota Access Pipeline and reached a reasonable conclusion that the project doesn’t harm American Indian tribes, an attorney for the agency argued in court documents asking the judge to rule in the government’s favor.

The Corps wants U.S. District Judge James Boasberg to sign off on its August 2018 finding that no more environmental study is warranted on the $3.8 billion pipeline that’s been moving North Dakota oil to Illinois for more than two years.

The Oct. 9 filing by Justice Department attorney Matthew Marinelli is in response to an August plea by the Standing Rock Sioux, which wants Boasberg to shut down the pipeline and order even more study than he already has.

Standing Rock is leading four Sioux tribes in the Dakotas in a three-year-old lawsuit over the pipeline built by Texas-based Energy Transfer. The tribes all recently made what amounts to their final legal arguments. The Corps is now doing the same.

The agency, which permitted the pipeline, “carefully and reasonably considered the environmental impacts of its action, including the risk and potential impact of a spill,” Marinelli wrote.

The tribes fear a pipeline spill into the Missouri River — which the line crosses beneath just to the north of the Standing Rock Reservation — 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 more than 760 arrests.

Energy Transfer maintains the pipeline is safe, a contention backed by the Corps.

But Boasberg in June 2017 ordered more study on the pipeline’s impacts on tribes. The Corps completed the work last fall and said it substantiated the agency’s earlier conclusions. Earthjustice attorney Jan Hasselman, who works on behalf of the Standing Rock Sioux, contended this past August that the additional work was “a sham,” in part because it relied on a “flawed” worst-case spill scenario and because it “traded one gerrymandered environmental justice analysis for another, with the Corps still unwilling to acknowledge that siting the pipeline immediately upstream of the Standing Rock Reservation presents serious environmental justice concerns.”

Marinelli disputes those contentions in his filing. The Corps used a spill model report consistent with federal regulations, he said, and tribal arguments “are insufficient to show that the Corps’ consideration of environmental justice was arbitrary.”

The concept of environmental justice deals with whether a project poses a higher risk of adverse impacts to minority or poor people. Boasberg in June 2017 criticized the Corps for focusing its Dakota Access study more on the mostly white demographics near the Missouri River crossing, and the tribe accused the Corps of gerrymandering because its study area did not include the reservation.

Hasselman in August said the Corps study “trivializes” the potential impacts of a spill to the tribe “by rationalizing that they would also be felt by nontribal members.”

Marinelli countered that the Corps’ environmental justice study “analyzes impacts specific to tribes and tribal members over hundreds of miles.”

Marinelli also wrote that the Corps “appropriately” sought information from tribes and consulted with Standing Rock “even though it had no obligation.”

Boasberg in August allowed nine groups including the American Civil Liberties Union and the National Congress of American Indians to weigh in on whether the Corps properly consulted tribes. He also allowed 14 other tribes from Washington state to Florida to provide comments.

The judge will decide later whether to order additional study. Should he decline, the suing tribes are likely to appeal. The lawsuit has lingered since July 2016. Meanwhile, Energy Transfer this summer announced a $40 million effort to nearly double the pipeline’s capacity through an increase in horsepower to meet demand from shippers.

State regulators will hold a public hearing Nov. 13 in Linton on Energy Transfer’s plan to build a pump station in Emmons County that would be necessary for an expansion.