On Dec. 4, the U.S. Supreme Court heard a case — L.A. County Flood Control District vs. National Resources Defense Council (NRDC) — focusing on stormwater discharges in the Los Angeles area. During oral arguments, all parties in the case agreed that the transfer of water through concrete-lined sections of the Los Angeles and San Gabriel Rivers does not constitute a “discharge” under the National Pollutant Discharge Elimination System (NPDES) municipal separate storm sewer system (MS4) permit held by the flood control district (District).

Oral arguments during the Dec. 4 case also focused on the scope of the District’s responsibility, under the compliance monitoring regime of its MS4 permit, for pollution detected at the in-river monitoring stations, regardless of any demonstrated connection to the District’s stormwater outfalls.

Arguments also addressed the Supreme Court’s options. It could reverse the Ninth Circuit decision outright or vacate the case, remanding it back to the Ninth Circuit to re-hear the issue of the District’s responsibility under their permit’s compliance monitoring regime. Although the Ninth Circuit previously rejected the District’s argument regarding permit interpretation, it might reconsider once the Supreme Court officially rules on the discharge issue.