In good news for local jurisdictions, the Supreme Court unanimously ruled today 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 (Los Angeles County Flood Control District v. Natural Resources Defense Council, Inc. et al.).

In Los Angeles County Flood Control District v. Natural Resources Defense Council (NRDC), the NRDC alleges that discharges from the municipal separate storm sewer system (MS4) resulted in pollutant exceedances in four rivers in Southern California. A U.S. district court found that the NRDC did not present evidence sufficient to prove that the county’s MS4 was responsible for the pollution. But the U.S. Court of Appeals for the 9th Circuit overruled the district court, finding that readings at the county’s self-monitoring stations revealed persistent violations of the county’s National Pollutant Discharge Elimination System (NPDES) permit.

According to the 9th circuit, evidence showed that monitoring stations for two of the rivers (the Los Angeles and the San Gabriel) are located in a channelized portion of the MS4 owned and operated by the District and after stormwater known to contain pollutant exceedances passes through the monitoring stations, it is discharged into the two rivers. When the pollutants were detected, they had not yet exited the point source (the concrete channels of the MS4) into navigable waters. The District claims that the infrastructure of the MS4 does not generate or discharge pollutants—it just conveys the stormwater that contains the pollutants. The Court said that because the District holds the permit for the MS4, it has the legal authority to hold dischargers to the MS4 accountable for their contributions of pollutants and flows through such things as ordinances, permits, contracts, and model programs.

The Supreme Court disagreed with the 9th circuit ruling, citing the South Fla. Water Management District v. Miccosukee Tribe decision in which the High Court ruled that pumping polluted water from one part of a water body into another of the same body is not a discharge of pollutants under the CWA. According to the Court, it follows from Miccosukee that no discharge of pollutants occurs when water, rather than being removed and then returned to a water body, simply flows from one portion of the water body to another.

Click here and here for a synopses of the oral arguments before the Supreme court in December.

Click here for today's Supreme Court decision.