The Supreme Court of the United States heard oral argument in County of Maui v. Hawai’i Wildlife Fund, No. 18-260, a case in which the justices will decide a key jurisdictional issue under the Clean Water Act (CWA): whether the CWA’s National Pollutant Discharge Elimination System (NPDES) permitting requirement applies to releases from point sources that traverse a nonpoint source—like groundwater—before entering navigable waters. Below, the Ninth Circuit had held that the County of Maui’s releases of treated wastewater from injection wells that reached the Pacific Ocean via groundwater required a permit because they were “fairly traceable” back to a point source. 

The justices pressed the advocates to defend their proposed tests for when a “discharge” occurs, such that the CWA requires a permit. In urging reversal, Maui contends that the CWA’s requirement that a point source be a “conveyance” means that a discharge occurs only when a point source actually delivers pollutants to navigable waters. By contrast, the environmental groups who sued Maui are asking the justices to hold that a discharge occurs whenever pollutants in navigable waters are (a) fairly traceable to a point source and (b) it was reasonably foreseeable that pollutants from that source would reach navigable waters. The United States argued in support of reversing the Ninth Circuit but argued that the Court make a narrow ruling that only excludes releases into groundwater (as opposed to releases onto land) from the NPDES permitting program.

Much of the questioning focused on three issues: the potential for evasion, predictability in the permitting regime, and whether any limiting principle could be applied to any of the arguments presented. Multiple justices expressed concerns about adopting a test that would allow otherwise-regulated entities to avoid having to obtain NPDES by locating pipes just short of navigable waters. Other questions focused extensively on the need for a standard that makes determining whether a NPDES permit is required clear before a discharge has commenced.

With the argument completed, the justices have taken the case under advisement. A decision is expected before the Court ends its term in June 2020.