By BLAKE NICHOLSON and JAMES MacPHERSON

CANNON BALL, N.D. (AP) — Oil could be flowing through the $3.8 billion Dakota Access pipeline in less than two weeks, according to court documents filed by the developer just before police and soldiers started clearing a protest camp in North Dakota where pipeline opponents had gathered for the better part of a year.

Energy Transfer Partners has finished drilling under Lake Oahe and will soon be laying pipe under the Missouri River reservoir, the Dallas-based company said.

“Dakota Access estimates and targets that the pipeline will be complete and ready to flow oil anywhere between the week of March 6, 2017, and April 1, 2017,” company attorney William Scherman said in the documents filed in Washington, D.C., on Tuesday.

The work under the Missouri River reservoir is the last stretch of the 1,200-mile pipeline that will move oil from North Dakota through South Dakota and Iowa to a shipping point in Illinois. ETP got permission for the lake work last month from the pro-energy Trump administration, though American Indian tribes continue fighting the project in court.

The Standing Rock and Cheyenne River Sioux tribes say the pipeline threatens their drinking water, cultural sites and ability to practice their religion, which depends on pure water. ETP rejects those claims and says the pipeline is safe.

The tribes have been fighting the construction since last summer, when an initial lawsuit was filed.

They have also asked U.S. District Judge James Boasberg to overturn permission for the river crossing. The Standing Rock Sioux filed a motion earlier this month, and the Standing Rock tribe filed a similar request on Wednesday. ETP didn’t immediately respond to the motions.

Several groups including the National Congress of American Indians and the Great Plains Tribal Chairman’s Association along with 34 other tribes on Thursday filed a court brief supporting Standing Rock’s request.

Boasberg has scheduled a hearing Tuesday on a separate request by the Cheyenne River tribe to temporarily halt the lake work until the full legal battle is resolved.

The drilling work is just to the north of a protest camp on federal land where pipeline opponents had gathered since August. Authorities shut down the camp Wednesday ahead of spring flooding, with an estimated 150-200 protesters leaving peacefully. Police officers and National Guardsmen cleared the camp of people Thursday, searching tents and huts and arresting dozens of holdouts who had defied the government order to leave.

Authorities said they arrested 46 people, including a group of military veterans who had to be carried out and a man who climbed atop a building and stayed there for more than an hour before surrendering.

As police in full riot gear worked to arrest the stragglers, cleanup crews began razing buildings on the square-mile piece of property at the confluence of the Cannonball and Missouri rivers.

American Indian activist Chase Iron Eyes, an outspoken supporter of the camp, said its shutdown is not the end of the fight against the pipeline.

“The battleground has shifted to the legal courts and the court of public opinion,” he said, referring to lawsuits filed by tribes and an effort planned by the Lakota People’s Law Project to rally lawmakers and others in Washington, D.C., to their cause.

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Nicholson reported from Bismarck, North Dakota. Follow him on Twitter at: http://twitter.com/NicholsonBlake