In a letter to the U.S. Army Corps of Engineers, chairmen of the Standing Rock Sioux Tribe, Cheyenne River Sioux Tribe, and the Oglala Sioux Tribe called for a stop to the environmental analysis of the Dakota Access Pipeline (DAPL) before it proceeds any further, rejecting the current process as “irredeemable” and “fatally flawed.”

In order to get back on track, Tribal leaders said the administration should terminate its contract with the firm that is tasked with producing the environmental impact statement (EIS), Environmental Resources Management (ERM). It also asked for the Department of Interior to be brought in as a co-equal cooperating agency, since the U.S. Army Corps of Engineers “has consistently demonstrated an institutional lack of sensitivity to and understanding of Tribal concerns.”

ERM, the same firm that was tasked with conducting environmental impact statements for the Keystone XL and TransCanada pipelines, is a member of the American Petroleum Institute — an oil-industry association that previously backed DAPL operator Energy Transfer with an amicus brief in litigation concerning the pipeline. In addition to this conflict-of-interest, Tribal leaders noted that an early draft of the environmental impact statement is filled with errors, omissions, and misstatements.

“Given ERM’s inherent bias, it is no wonder that the draft EIS largely ignores the last five years of history and the thousands of pages of detailed technical and cultural material shared by the Tribes,” the chairmen wrote. “Instead of a good faith examination of the critical issues of siting this pipeline in the Tribes’ treaty lands … this is an advocacy document that appears to be prepared by the proponent for a single purpose: to justify issuance of a new easement of the pipeline at its current location.”

In July, the Pipeline and Hazardous Materials Safety Administration flagged a list of safety regulations Energy Transfer had violated, raising additional concerns that the infrastructure — which continues to operate without a valid federal permit — could cause a major oil spill. Nevertheless, Energy Transfer recently made modifications doubling its capacity to transport oil.