The United States Supreme Court will review a ruling of the Ninth Circuit Court of Appeals that found the Los Angeles County Flood Control District in violation of its permit under the Clean Water Act for its Municipal Separate Storm Sewer Systems (MS4) discharges into the Los Angeles and San Gabriel Rivers. Segments of those rivers that constitute a part of the MS4 have been paved to improve flood control, and the pollution levels measured as the water moves through those segments and other monitoring locations exceed the amounts allowed by the District’s permit. The District claims that pollution is not a discharge of the District, but is instead the mere passage of water from one part of the river to another.
Robert Abrams, Municipal Separate Storm Sewer Systems (MS4)--Assigning Responsibility for Pollutants That Reach the Nation's Waters, 40 Preview U.S. Sup. Ct. Cas. 129 (2012).