Section 511 of the Clean Water Act requires that the Environmental Protection Agency (EPA) comply with National Environmental Policy Act (NEPA) requirements when issuing a National Pollutant Discharge Elimination System (NPDES) permit to a “new source” as defined in CWA §306. This consolidated case involves issuance of an NPDES permit that U.S. EPA Region 8 issued to the Three Affiliated Tribes, comprising the Mandan, Hidatsa, and Arikara Nation, allowing wastewater discharges from a new source.