On February 19, the Supreme Court granted certiorari in the closely-watched Clean Water Act (CWA) case, County of Maui, Hawai'i. v. Hawai'i Wildlife Fund. The Court agreed to take up a critical issue that has been the focus of several citizen suits around the country: whether a National Pollutant Discharge Elimination System (NPDES) permit is required for activities that release pollutants that are eventually conveyed through groundwater or soil to navigable water.

The County of Maui case centers on the County's discharge of treated municipal wastewater into underground injection wells. Several environmental groups sued the County, claiming that the injection of wastewater without an NPDES permit violates the CWA because contaminants from the injection wells migrate through groundwater to the ocean. The Ninth Circuit agreed, finding that the permit requirement applies when pollutants discharged from a point source are "fairly traceable" from the point source to navigable water and the pollutants reach the navigable water at "more than de minimis" levels. Haw. Wildlife Fund v. Cty. of Maui, Haw., 886 F.3d 737, 749 (9th Cir. 2018).

The United States and several industry groups filed amicus briefs in support of the County's cert petition, arguing that the Supreme Court should take the case to resolve a circuit conflict on the question of whether the NPDES program applies to activities that cause pollutants to be conveyed through groundwater to navigable water. The amicus briefs argue that the Ninth Circuit's holding threatens to impose unprecedented liability to a wide swath of new sources and facilities, because an NPDES permit could be mandated any time pollutants are released into soil or groundwater and eventually reach navigable waters, regardless of the mode or duration of migration.

The case is important to a broad range of industries beyond those utilizing injection wells, as similar arguments regarding NPDES liability have been raised in citizen suits involving everything from petroleum pipelines to coal ash ponds. Historically, NPDES permits have only been required for direct discharges from "point" sources, like an outfall pipe, directly to jurisdictional waters. Since groundwater is not jurisdictional under the CWA, discharges to groundwater have instead generally been subject to state, rather than federal, jurisdiction. The Ninth Circuit's holding would significantly expand the reach of the CWA by applying its onerous permitting requirements to much more indirect discharges of pollutants. The groundwater migration theory of liability at issue in this case would potentially expose a broad range of industrial facilities to CWA obligations and liabilities that they do not confront today, including potentially substantial CWA penalties.

The case is expected to be placed on the Supreme Court's calendar for the next term, which begins in October, which means a resolution of this issue is likely to occur in the first half of 2020.