Los Angeles County Flood Control District v. Natural Resources Defense Council, Inc.

Background

The dispute involves the Los Angeles County Flood Control District, which runs a large storm-drain system, and environmental groups that sued under the Clean Water Act. Monitoring stations in the Los Angeles and San Gabriel Rivers showed repeated pollutant exceedances. The environmental groups said those exceedances proved the District violated its pollution permit. The District and lower courts disputed whether the polluted water measured in the rivers came from the District’s concrete-lined channels or from many other upstream sources.

Reasoning

The narrow question the Court took was whether water flowing out of a concrete-lined part of the same river counts as a separate “discharge of pollutants” under the Clean Water Act. The parties and the United States agreed the answer was no, and the Court relied on its earlier decision that moving polluted water within the same water body does not add pollutants to it. The Court explained that the statute bars an “addition” of pollutants from a point source, and simply moving water from one part of a river to another does not add pollutants. Applying that view, the Court held there was no discharge when water flowed from an improved portion of the river into an unimproved portion, and it reversed the Ninth Circuit.

Real world impact

The ruling makes it harder to hold the District liable based solely on instream monitoring where the water remains within the same river. It leaves open other enforcement routes, including permit terms and end-of-pipe monitoring required by the renewed permit. Because the Court decided a narrow legal question, some permit-based claims may still proceed on different evidence or theories.

Dissents or concurrances

Justice Alito agreed with the judgment. The environmental groups pressed an alternative permit-based theory, but the Court did not consider that issue.