The Clean Water Act is federal legislation designed to control the quality of water and protect the public against polluted or contaminated water. The Act required a Flood Control District in Los Angeles County to obtain a permit in order to discharge storm water into navigable waters due to the often high levels of pollution in the storm sewer drainage system. This permit prohibited the District from discharging water with pollutants above a certain measurable level. The Natural Resources Defense Council brought suit against the District arguing it had violated this permit by discharging water with excessive levels of pollutants. The District Court ruled in favor of the Flood Control District, but the Ninth Circuit reversed, citing a discharge of pollutants when the water "flowed out of concrete channels" and into the river where no concrete channels existed.
The Supreme Court reversed the Ninth Circuit's decision in Los Angeles County Flood Control District v. Natural Resources Defense Council, Inc., No. 11-460, on January 8, 2013. The Court stated that there is no discharge of pollutants when polluted water flows from one part of a river, into a concrete lined channel, and then back into the same river where the concrete ends. The ruling followed precedent that held that "discharges" under the Clean Water Act occur only when water flows between different and distinct bodies of water - not within the same river along different portions of the waterway.