Sixth Time’s A Charm? Another Chapter in the WOTUS Saga

by Lora K. Naismith and Lauren C. Thomson

If the definition of “waters of the United States” (“WOTUS”) under the Clean Water Act (“CWA”) were a movie series, we would have far surpassed the original film, the sequel, the threequel, and even the prequel. With the newest addition of the proposed rule released on November 17, 2025 by the Trump Administration’s Environmental Protection Agency and U.S. Army Corps of Engineers (collectively, the “Agencies”), the definition of WOTUS has developed into a full-fledged franchise. This is not the first time the agencies have proposed a rule to amend the definition of WOTUS, and, based on the last decade, it is unlikely to be the finale.

At its core, WOTUS is about jurisdiction. If a surface waterbody—be it a stream or a river or a lake—falls under the WOTUS definition, it is subject to regulation under the CWA. This means that any person or entity seeking to discharge into WOTUS or dredge or fill WOTUS must seek permission from state and federal agencies prior to any discharge or dredge or fill work.¹ If a waterbody does not fall under the definition of a WOTUS, then the waterbody is not subject to federal CWA jurisdiction, although it may still be regulated under state law depending on where it is located. This article focuses on solely the proposed updates to the definition of WOTUS.

The agencies are proposing their sixth definition of WOTUS in the last ten years. Prior to 2015, WOTUS was a combination of regulations from 1986, the Migratory Bird Rule, and case law from Solid Waste Agency of Northern Cook County v. Army Corps of Engineers and United States v. Rapanos.² The Supreme Court’s decision in Rapanos is central to nearly every WOTUS rulemaking over the past ten years. In Rapanos, because the Court did not issue a majority opinion, two competing standards emerged. Justice Scalia’s plurality opinion limited CWA jurisdiction to “relatively permanent” bodies of water and wetlands with a continuous surface connection to such waters,³ while Justice Kennedy’s concurrence adopted a broad “significant nexus” test, which looked at whether a water or wetland significantly affected downstream navigable waters.⁴

In 2015, the Obama Administration issued the Clean Water Rule, which expanded federal jurisdiction by relying on the concept of a “significant nexus” existing between certain water and traditionally navigable waters (as seen in Justice Kennedy’s plurality opinion in Rapanos).⁵ The Obama Administration’s rule was repealed in 2019. In 2020, the first Trump Administration issued the Navigable Waters Protection Rule, which defined WOTUS based on the Rapanos plurality’s standard of “relatively permanent, standing or continuously flowing bodies of water.”⁶ This rule was later vacated by a federal court.⁷ In January 2023, the Biden Administration issued the Amended 2023 WOTUS Rule, which amended WOTUS to incorporate the two jurisdictional standards from Rapanos, called the “relatively permanent standard” and the “significant nexus standard.”⁸ Later, in May 2023, the Supreme Court decided Sackett v. EPA, limiting the reach of WOTUS jurisdiction by rejecting the significant nexus test and holding that wetlands are only subject to CWA jurisdiction when they have a continuous surface connection to relatively permanent waters.⁹ In response, the Biden Administration issued a conforming rule to conform with the Supreme Court’s ruling in Sackett v. EPA (the “Conforming Rule”). This version of the Conforming Rule removed the broad “significant nexus” standard as described in Justice Kennedy’s concurring opinion in Rapanos, amended the definition of “adjacent,” and removed “interstate wetlands.”¹⁰ Due to ongoing litigation, the Conforming Rule currently applies in 24 states. Texas is not one of them. In 26 states, including Texas, the pre-2015 version of the WOTUS Rule (described above) is in effect.¹¹

This latest installment—the 2025 Proposed Rule—further amends the Conforming Rule. Under the Proposed Rule, the definition of WOTUS would be changed to include: (1) traditional navigable waters and the territorial seas; (2) most impoundments of WOTUS; (3) relatively permanent tributaries of traditional navigable waters, the territorial seas, and impoundments; (4) wetlands adjacent (i.e., having a continuous surface connection) to traditional navigable waters, impoundments, and tributaries; and (5) lakes and ponds that are relatively permanent and have a continuous surface connection to a traditional navigable water, the territorial seas, or a tributary.¹² Notably absent from this definition is the long-standing inclusion of intrastate waters. Under the Proposed Rule, a waterbody that crosses state lines and does NOT fall under any of the definitions in items (1) – (5), above would not be considered WOTUS.¹³ In other words, a waterbody that runs between two states does not automatically get WOTUS jurisdiction. However, a waterbody that runs between two states can still be subject to WOTUS, so long as it meets one of the definitions in items (1) – (5), above.

The Proposed Rule also adds definitions for “relatively permanent,” “wet season,” “tributary,” “continuous surface connection,” and “waste treatment system.” The Agencies are seeking comment from the public on several aspects of these definitions.

• “Relatively permanent,” as used in “relativity permanent tributaries of traditional navigable waters” above, would be defined as “standing or continuously flowing bodies of surface water that are standing or continuously flowing year-round or at least during the wet season.”¹⁴
• “Wet season” would be defined as when average monthly precipitation exceeds average monthly evapotranspiration.¹⁵
• “Tributary” would mean “a body of water with relatively permanent flow, and a bed and bank, that connects to a downstream traditional navigable water or the territorial seas, either directly or through one or more waters or features that convey relatively permanent flow.”¹⁶ Notably, a tributary would not include “a body of water that contributes surface water flow to a downstream jurisdictional water through a feature such as a channelized non-jurisdictional surface water feature, subterranean river, culvert, dam, tunnel, or similar artificial feature, or through a debris pile, boulder field, wetland, or similar natural feature, if such feature does not convey relatively permanent flow.”¹⁷
• “Continuous surface connection” as described above would mean a two pronged test of: (1) having surface water at least during the wet season and (2) abutting (i.e., touching) a jurisdictional water.¹⁸ The phrase “having surface water at least during the wet season” is intended to include wetlands that have at least semi-permanent surface hydrology that is persistent surface water hydrology uninterrupted throughout the wet season except in times of extreme drought and would not include wetlands without semi-permanent surface hydrology, including wetlands with only saturated soil conditions supported by groundwater.¹⁹

For years, the regulated community has asked for regulatory certainty in regards to the CWA’s application to discharges into waste treatment systems. A frequent comment received by the agencies was waste treatment lagoons and other waste treatment systems should not be considered WOTUS.²⁰ The Proposed Rule will keep the exclusion for waste treatment systems, which has been in effect since 1979,²¹ and proposes to add a definition for waste treatment systems to be defined as “all components of a waste treatment system designed to meet the requirements of the Clean Water Act, including lagoons and treatment ponds (such as settling or cooling ponds), designed to either convey or retain, concentrate, settle, reduce, or remove pollutants, either actively or passively, from wastewater prior to discharge (or eliminating any such discharge).”²² However, for stormwater systems and wastewater reuse facilities, “such determinations would depend on the specific attributes of the control and the water feature and thus need to be made on a case-by-case basis.”²³

Although the Agencies describe the Proposed Rule as an effort to provide greater regulatory certainty, predictability, and consistency,²⁴ past revisions to the WOTUS definition suggest that increased litigation is likely, particularly over the dividing line between federal and state authority and the interpretation of newly adopted terms. The Agencies anticipate that the Proposed Rule will lead to an increase in non-jurisdictional findings in jurisdictional determinations, and fewer waters and wetlands would fall within the scope of the CWA.²⁵ The Agencies also expect that CWA Section 404 permitting will see reductions in both the number of permits issued and the amount of mitigation required for projects.²⁶

The comment period deadline closed January 5, 2025, and the Agencies will have two public comment sessions forthcoming. Comments are available for viewing online at www.regulations.gov to Docket ID No. EPA-HQ-OW-2025-0322. At this rate, the total number of WOTUS installments could one day rival the films in the Marvel Cinematic Universe. As we wait to see how the series unfolds, if you have questions or need assistance in understanding the changes to the Proposed Rule, please reach out.

¹See 33 U.S.C. §§ 1342 and 1344 (Clean Water Act sections regarding discharges into WOTUS and Section 404 dredge and fill permitting).
²See 84 Fed. Reg. 56626 (Oct. 22, 2019); Solid Waste Agency of Northern Cook Cnty v. Army Corps of Eng’rs, 531 U.S. 159 (2001); United States v. Rapanos, 547 U.S. 715 (2006).
³Rapanos, 547 U.S. at 739.
⁴Id. at 779.
⁵See 80 Fed. Reg. 37054 (Jun. 29, 2015).
⁶See 85 Fed. Reg. 22250 (Apr. 21, 2020).
⁷See Pasqua Yaqui Tribe v. U.S. Env’t Prot. Agency, 557 F.Supp. 3d 949 (D. Ariz. 2021).
⁸See 88 Fed. Reg. 3004 (Jan. 18, 2023).
⁹Sackett v. U.S. Env’t Prot. Agency, 598 U.S. 651 (2023).
¹⁰See 85 Fed. Reg. 61964 (Sept. 8, 2023).
¹¹90 Fed. Reg. 52498, 52512 (Nov. 20, 2025).
¹²Id. at 52499.
¹³Id. at 52516.
¹⁴Id. at 52517-18.
¹⁵Id.
¹⁶Id. at 52521.
¹⁷Id.
¹⁸Id. at 52527.
¹⁹Id.
²⁰Id. at 52534.
²¹44 Fed. Reg. 32854, 32858 (Jun 7, 1979);
90 Fed. Reg. 52499, 52534 (Nov. 20, 2025).
²²90 Fed. Reg. 52499, 52534 (Nov. 20, 2025).
²³Id. at 52535.
²⁴Id. at 52499.
²⁵Id. at 52500.
²⁶Id.

Lora Naismith is an Associate in the Firm’s Water Practice Group and Lauren Thomson is a Principal in the Firm’s Water, Litigation, and Compliance and Enforcement Practice Groups. If you would like additional information related to this article or other matters, please contact Lora at 512.322.5850 or lnaismith@lglawfirm.com, or Lauren at 512.322.5858 or lthomson@lglawfirm.com.