Natural Resources Defense Council v. Los Angeles County, United States Court of Appeals for the Ninth Circuit, Case No. 10-56017 (March 10, 2011)

The Ninth Circuit Court of Appeals held that environmental groups were entitled to summary judgment after presenting evidence that the Los Angeles County Flood Control District ("District") had illegally discharged polluted stormwater into the Los Angeles River and San Gabriel River in violation of the federal Clean Water Act. The District has argued that the evidence did not show it was the source of the pollutants, only that it conveyed polluted stormwater. The Ninth Circuit rejected this argument and decided summary judgment was appropriate because monitoring stations located in a section of the municipal separate storm sewer system ("MS4") owned and operated by the District detected pollutants in excess of the limits set forth in the District's National Pollutant Discharge Elimination System permit ("Permit") and, after the polluted stormwater passes through these monitoring stations, it was discharged into the two rivers, causing or contributing to exceedances of water quality standards.