The Dakota Access Pipeline (DAPL) was designed to transport oil from North Dakota to Illinois, crossing the Missouri River at Lake Oahe near the Standing Rock and Cheyenne River Sioux Reservations. The U.S. Army Corps of Engineers prepared an Environmental Assessment (EA) and issued a Finding of No Significant Impact (FONSI) in July 2016, concluding an Environmental Impact Statement (EIS) was not required. The Corps then granted permits under Section 408 of the Rivers and Harbors Act and Nationwide Permit 12, and later issued an easement under the Mineral Leasing Act in February 2017 allowing pipeline construction under Lake Oahe. The Standing Rock Sioux Tribe, located 0.55 miles downstream from the crossing, and Cheyenne River Sioux Tribe, located 73 miles downstream, challenged the Corps' decisions. Both Tribes rely on Lake Oahe for drinking water, fishing, hunting, and religious practices. Lake Oahe was created in 1958 by damming the Missouri River, resulting in the taking of significant tribal lands. The Tribes expressed concerns about oil spill risks, impacts on Treaty rights, and environmental justice, submitting comments and expert reports criticizing the EA's methodology and data.