onstruction crews have resumed work on the final segment of the Dakota Access pipeline, and the developer of the long-delayed project said Thursday that the full system could be operational within three months. Meanwhile, an American Indian tribe filed a legal challenge to block the work and protect its water supply. The Army granted Energy Transfer Partners formal permission Wednesday to lay pipe under a North Dakota reservoir, clearing the way for completion of the 1,200-mile pipeline. Company spokeswoman Vicki Granado confirmed early Thursday that construction began "immediately after receiving the easement." Workers had already drilled entry and exit holes for the segment, and oil had been put in the pipeline leading up to Lake Oahe in anticipation of finishing the project. The Cheyenne River Sioux on Thursday asked a federal judge to stop the work while a lawsuit filed earlier by the tribes proceeds. Attorney Nicole Ducheneaux said in court documents that the pipeline "will desecrate the waters" that the Cheyenne River Sioux rely on.