In its January 8, 2013 decision in Los Angeles County Flood Control District v. Natural Resources Defense Council, Inc. (Docket No. 11-460), the Supreme Court reversed the 9th Circuit and declared that the flow of water from an improved portion of a navigable waterway into an unimproved portion of that waterway does not constitute a “discharge of a pollutant” under the federal Clean Water Act.
In this case, the Los Angeles County Flood Control District (LACFCD) had operated a “municipal separate storm sewer system” (“MS4”) for which it had obtained a National Pollutant Discharge Elimination System (NPDES) permit as required by the Clean Water Act. In the course of operating the MS4, polluted water detected at monitoring stations in the Los Angeles and San Gabriel Rivers had flowed out of concrete channels in those waterways and into downstream portions of the waterways lacking concrete linings. The Supreme Court held that the Clean Water Act defines the term “discharge of a pollutant” as “an addition of any pollutant to navigable waters” and that “no pollutants are ‘added’ to a water body when water is merely transferred between different portions of that water body.”
The court did not rule on the Natural Resource Defense Council’s contention that, regardless of the flow of polluted water, the pollution levels detected at the monitoring stations alone exceeded those allowed for upstream discharges under LACFCD’s NPDES permit.