Conveyance of Polluted Water Within River Involves No 'Discharge' Under Clean Water Act

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The flow of polluted water from a concrete-lined portion of a river into a downstream portion of the same river does not involve a “discharge” for purposes of the Clean Water Act (“CWA”) and thus involves no CWA violation, the Supreme Court held in an opinion filed January 8. The Court’s opinion reverses a Ninth Circuit judgment that held the Los Angeles County Flood Control District (“District”) liable for CWA violations based on sampling data that showed polluted water leaving portions of the Los Angeles and San Gabriel Rivers controlled by the District and entering downstream portions of the same rivers. The opinion addresses only a very narrow issue that is controlled by the Court’s prior decision in South Fla. Water Management Dist. v. Miccosukee Tribe, 541 U.S. 95 (2004), and does not reach larger questions about the scope of liability for operators of municipal separate storm sewer systems (“MS4”).

In the proceedings below, the District conceded that water quality monitoring data showed violations of water quality standards in the Los Angeles and San Gabriel Rivers downstream of its MS4 facilities. The CWA permit issued for the District’s MS4 system prohibited discharges that would cause or contribute to violations of water quality standards. But the District argued that the evidence did not show it had caused or contributed to the water quality violations because (1) other entities also were permitted to discharge pollutants into the Rivers upstream of the monitoring stations, and (2) the District’s MS4 facilities convey, but do not generate, the collective discharges generated by many other MS4 co-permittees located “up-sewer.” The district court agreed, finding no evidence that the pollutants measured at the monitoring stations had been discharged by the District.

The Ninth Circuit reversed, apparently believing that the monitoring stations were located within the MS4 system owned and operated by the District—not downstream of it—and thus that the pollutants detected by the monitoring stations necessarily would be “discharged” from the MS4 into the Rivers, in violation of the District’s MS4 permit. NRDC v. County of Los Angeles, 673 F. 3d 880, 899-901 (9th Cir. 2011). According to the Supreme Court, however, the monitoring stations were located within portions of the Rivers that had been channelized and lined with concrete for flood control purposes. Thus, the monitoring data only showed a discharge from portions of the Rivers controlled by the District to other portions of the same Rivers.

The Court therefore granted certiorari on a single question: does a “discharge of pollutants” occur when polluted water “flows from one portion of a river that is [a] navigable water of the United States, through a concrete channel or other engineered improvement in the river . . . into a lower portion of the same river?” All the parties agreed that this question was answered by the Court’s 2004 Miccosukee decision, which held that the transfer of polluted water between “two parts of the same water body” does not constitute a discharge of pollutants under the CWA, because a discharge requires the addition of a pollutant to navigable waters from a point source.

Because of the unusual factual situation and the narrow issue certified for review, the scope of the Court’s holding is limited. In particular, it does not address the District’s potential liability if the plaintiffs provide evidence showing that a “discharge” of pollutants did occur from the MS4 system to the Rivers, nor the District’s argument that it should not be held liable for pollutants contributed by “up-sewer” permittees.