Mountaintop removal mining operations in the Appalachian region have expanded significantly in recent decades. The practice decimates the mountain ecosystems by leveling forests, filling headwater streams, and producing significant runoff of heavy metals, sediment, and other pollutants that impair the aquatic environment of entire watersheds. Yet environmental permitting of the practice is relatively limited. A recent trend in litigation aimed at halting mining operations has involved challenging permits that authorize the discharge of mining overburden into headwater streams pursuant to the Clean Water Act (CWA). The Army Corps of Engineers has assumed jurisdiction over such discharges under section 404 of the CWA, asserting that overburde...