On September 8, 2023, the Army Corps of Engineers and Environmental Protection Agency published new standards defining “waters of the United States” as it relates to regulations under the Clean Water Act. The new regulations took effect immediately to fill a void left by the Supreme Court’s ruling in Sackett v. Environmental Protection Agency, 598 U.S. 651 (2023), in May, and they replace standards implemented in March 2023.

After Sackett, the CWA’s corresponding regulations did not provide a working definition for waters of the United States, a necessary starting point for any regulatory action under the CWA. The agencies state in the entry in the Federal Register that because the new rule is to amend the previous one to conform to the Supreme Court’s ruling in Sackett, advanced public notice and a comment period are not necessary; the new promulgation does not call for discretion by the agency.

The March standards sought to expand the definition of waters of the United States to encompass two competing standards outlined in a prior Supreme Court case that dealt with the definition, Rapanos v. United States, 547 U.S. 715 (2006). The two standards were the “relatively permanent” standard and the “significant nexus” standard. The relatively permanent standard was agreed upon by the plurality in Rapanos, focusing on waters that maintain a continuous surface connection to other waters that more clearly fit into the definition of waters of the United States. The significant nexus standard as included in the March rule included all waters that “significantly affect the chemical, physical, or biological integrity of traditional navigable waters, the territorial seas, or interstate waters.”

In Sackett, the Supreme Court held that only the relatively permanent standard should apply. The new regulations remove the significant nexus test from various provisions related to the definition of waters of the United States. The new regulations limit the inclusion of wetlands to the same relatively permanent surface connection standard as other waters. Additionally, Sackett and the new regulations change the definition of “adjacent” as it is used in the CWA to define covered wetlands to require a continuous surface connection to covered waters. The new definition will reduce the scope of wetlands protection under the CWA.

However, Sackett and the new regulations seem to leave some ambiguities in how the regulations should be implemented. Neither the Court in Sackett nor the agencies in the regulations define what exactly “relatively permanent” or “continuous surface connection” mean regarding waters and wetlands. “Relatively permanent” allows that a water covered under the CWA may be dry or cease flowing for some period of time. How long is a question that will likely be litigated in the future. Likewise, “continuous surface connection” may come into play in litigation in the future related to wetlands adjacent to waters whose coverage under the CWA may be questioned for their seasonal or other periodic disruptions.