The U.S. Environmental Protection Agency and the U.S. Army Corps of Engineers on Wednesday published a final rule defining “Waters of the United States,” or WOTUS, which determines the extent of federal regulatory authority under the Clean Water Act. 88 Fed. Reg. 3004-3144 (Jan. 18, 2023). The new rule largely reinstates the longstanding definition of WOTUS first adopted in 1986, as modified by the Supreme Court’s opinion in Rapanos v. United States,547 U.S. 715 (2006). But the final rule comes as the Supreme Court again considers the proper scope of WOTUS in Sackett v. Environmental Protection Agency, which will likely determine the viability of the new definition.

The final rule defines WOTUS to include, subject to certain exceptions:

• Waters commonly referred to as “traditional navigable waters,” including those used or usable in interstate or foreign commerce, including tidal waters; the territorial seas; and interstate waters, including interstate wetlands;

• Impoundments of waters otherwise defined as WOTUS (except for impoundments of WOTUS identified in the fifth bullet, below);

• Tributaries of the above that meet either the “relatively permanent” test or the “significant nexus” test, both of which were outlined in the Supreme Court’s Rapanos opinion;

• Wetlands that are adjacent to traditional navigable waters or that meet either the “relatively permanent” test or the “significant nexus” test; and

• Wholly intrastate waters and wetlands not identified above that meet either a modified version of the “relatively permanent” test or the “significant nexus” test.

Return to the Status Quo?

With minor differences, the final rule effectively reinstates the definition of WOTUS in effect from 1986 until 2015, as modified by guidance adopted in 2008 to implement the Rapanos opinion. That guidance, like the new rule, required that non-navigable tributaries and certain wetlands meet either the “relatively permanent” standard articulated in Justice Scalia’s plurality opinion in Rapanos, or the “significant nexus” standard outlined in Justice Kennedy’s concurring opinion in Rapanos. As adopted in the final rule, the relatively permanent standard requires that non-navigable tributaries be “relatively permanent, standing or continuously flowing bodies of water,” and that wetlands have a “continuous surface connection” to relatively permanent or traditional navigable waters. The significant nexus test allows jurisdiction over non-navigable tributaries and/or their adjacent wetlands when they “significantly affect the chemical, physical, or biological integrity” of traditional navigable waters.

In 2015, the agencies issued a rule that broadened the definition of WOTUS. The next administration attempted to repeal the 2015 rule and then replaced it with another rule in 2020 that narrowed the definition. Both rulemakings faced legal challenges and were vacated by federal courts in some jurisdictions, leaving the pre-2015 definition in effect prior to the latest rulemaking, which takes effect March 20, 2023.

The Implications of Sackett

While the agencies have been engaged in the current rulemaking, a challenge to the “significant nexus” standard has played out in the Sackett case, which concerns the application of Clean Water Act Section 404 to wetlands on a residential lot in Idaho. The Sackett petitioners have asked the Supreme Court to limit jurisdiction to wetlands meeting the “reasonably permanent” test, excluding many features that would qualify as WOTUS under the “significant nexus” test, and at oral argument in October many observers perceived a majority of the Court to be skeptical of the “significant nexus” standard. The agencies may have aimed to strengthen their position by adopting the final rule in advance of the Court’s decision in Sackett, but, if the Court rejects the “significant nexus” test, it would leave the 2023 final rule on uncertain ground. Regardless of the outcome, however, the Sackett opinion has the potential to end nearly two decades of uncertainty over the proper interpretation of the fractured Rapanos decision, in which no opinion garnered the support of a majority of the justices.

The definition of WOTUS has important practical implications for many landowners and industries because it defines the waters subject to various Clean Water Act programs, including those that regulate discharges of dredge and fill material (Section 404) and discharges of stormwater and wastewater (Section 402), as well as prevention and cleanup of oil spills and other hazardous substances (Section 311), and application of federal water quality standards (Section 303). Under Section 401 of the Act, states also are required to review and certify permit decisions authorizing discharges to WOTUS.