In Los Angeles County Flood Control District v. Natural Resources Defense Council, Inc., No. 11-460, decided January 8, 2013, the United States Supreme Court unanimously held that the flow of water from an improved portion of a navigable waterway into an unimproved portion of the same waterway does not qualify as a “discharge of a pollutant” under the Clean Water Act (CWA). 

The Court reversed a U.S. Court of Appeals for the Ninth Circuit decision holding that pre-polluted water originating from a navigable river and passing through a “man-made construction” into the natural river below is a “discharge of a pollutant” under the CWA.  The Ninth Circuit’s decision raised concerns for the hydropower industry because dams are man-made constructions in navigable waters that discharge water downstream, and the decision suggested, contrary to well-established precedent, that dams could become subject to National Pollutant Discharge Elimination System (NPDES) permitting under section 402 of the CWA. 

The Court’s decision preserves long-standing precedent that hydropower dams are generally not subject to NPDES permits.  Had the Ninth Circuit’s decision been affirmed, dam operators could have been required to obtain NPDES permits for releases of water, such as power-generation activities or spillway releases.  Because NPDES permits must be obtained every five years, this requirement could interfere significantly with Federal Energy Regulatory Commission-issued long-term licenses that already contain compliance requirements, including water quality conditions under section 401 of the CWA.  Los Angeles County Flood Control District clarifies that the flow of water through a man-made construction (such as a dam, penstock, and/or powerhouse) within the same waterway does not qualify as a discharge of pollutants and does not require an NPDES permit.