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Supreme Court Rules in Favor of Los Angeles County Regarding Stormwater Case

By Judy Sheahan
January 14, 2013


The Supreme Court unanimously ruled on January 8 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.” The U.S. Conference of Mayors supported Los Angeles County’s position by signing onto an amicus briefing in the case Los Angeles County Flood Control District (LA County) v. Natural Resources Defense Council, Inc. (NRDC).

In this case, Los Angeles County operated a municipal separate storm sewer system (MS4), and had a National Pollutant Discharge Elimination System (NPDES) permit. The county also operates a series of concrete-lined portions of the river with monitoring stations positioned farther down the river. NRDC claimed that the downstream monitoring stations established that the county was violating the terms of its NPDES permit. The District Court said that is was undisputed that the monitoring stations did demonstrate that the number of pollutants exceeded water quality standards but that “thousands of (other) permitted dischargers,” other than the county, discharged into the rivers upstream of the monitoring stations and therefore there was insufficient evidence to find that the county had violated their permit.

The Appellate Court reversed the District Court’s decision and ruled that the county was liable for the discharge of pollutants that “occurred when the polluted water detected at the monitoring stations flowed out of the concrete-lined portions of the rivers, where the monitoring stations are located, into lower, unlined portions of the same rivers.”

The Supreme Court disagreed and reversed the Appellate Court’s decision basing their decision on a previous ruling, South Florida Water Management District v. Miccosukee Tribe. In that case the Supreme Court ruled that the “transfer of polluted water between ‘two parts of the same water body’ does not constitute a discharge of pollutants under the Clean Water Act.”

It should be noted that shortly before the Los Angeles County case was heard, Los Angeles County’s renewed NPDES permit was approved but was changed to require end-of-pipe monitoring at individual MS4 discharge points. More information about this court case will be discussed during the Environmental Committee hearing at the upcoming Conference of Mayors Winter Meeting.