Native American Tribes including the Standing Rock Sioux Tribe on Sept. 22 told the U.S. Army Corps of Engineers that the environmental study on Dakota Access oil pipeline is biased and urged the Biden administration to bring in the U.S. Interior Department.

The U.S. District Court for the District of Columbia revoked a key environmental permit for the largest pipeline out of the North Dakota oil basin last year and ordered the study.

The Tribes said on Sept. 22 they believe the process is currently designed to justify issuing a new permit in the same location and that the draft of the study does not take into account technical and cultural information that the Tribes have presented to the Corps.

"Our participation in the EIS (Environmental Impact Statement) process and review of the initial draft reveals that the Corps has fundamentally misunderstood the courts' directive and the requirements of the law," the Tribes said in the letter addressed to Jaime Pinkham, acting assistant secretary of the Army for Civil Works, on Sept. 22.

"The Administration must bring in the U.S. Department of the Interior as a co-equal cooperating agency with appropriate expertise to assist the Corps in centering Tribal impacts and concerns which motivated this EIS in the first place."

Dakota Access' operators earlier this week asked the U.S. Supreme Court to revisit whether the 570,000 barrel-per-day pipeline requires additional environmental review.

The pipeline entered service in 2017 following months of protests by environmentalists, Native American tribes and their supporters. Opponents said its construction destroyed sacred artifacts and posed a threat to Lake Oahe, a critical drinking supply, and the greater Missouri River.

Energy Transfer, which operates the line, has said it is safe.

Onshore