EPA and Army Corps Release Sweeping 2025 WOTUS Redefinition

On November 17, the U.S. Environmental Protection Agency and the U.S. Army Corps of Engineers unveiled their long-anticipated 2025 Proposed Rule redefining “waters of the United States” (WOTUS) under the Clean Water Act. The 100-page pre-publication version marks the Biden administration’s first major post-Sackett rewrite, setting the stage for yet another national realignment of water jurisdiction, permitting pathways, and enforcement exposure.

CIPA’s regulatory team has completed a first-look review of the rule and is preparing formal comments. Below is a preliminary summary for members.

The Agencies emphasize that this proposal “aligns with Sackett,” but the fine print suggests a rule that may substantially expand federal review in practice, especially in California, where hydrology, wetlands, and landscape features are diverse and seasonally complex.

The Proposed Rule makes four core structural changes:

• Eliminates the interstate waters category

• Deletes “intrastate” from lakes and ponds

• Adds new definitions (including continuous surface connection, relatively permanent, ditch, tributary, prior converted cropland, waste treatment system)

• Adds an explicit exclusion for groundwater
  

These revisions reshape virtually every WOTUS category.

EPA and the Corps offer no major changes but signal they may revisit what counts as “susceptible to interstate commerce,” a potential opening for future reinterpretation.

The rule eliminates interstate waters entirely, noting that only 15 waters nationwide were ever found jurisdictional on that basis. (A post-Sackett cleanup but with minor real-world effect.)

The proposal introduces a firm tripartite test. A tributary must have:

1. Relatively permanent flow,

2. A bed and banks, and

3. A surface connection to a downstream TNW or territorial sea.
   

However, the definition of “relatively permanent” is where the jurisdictional reach becomes sharper:

Standing or continuously flowing water year-round or throughout the wet season, with continuous surface hydrology throughout that season.

This is a major change. It broadens jurisdiction by relying on wet-season hydrology, not annual hydrology, and it rejects the familiar “typical year” test.

Notably:

• Ephemeral features are non-jurisdictional.

• Any break in flow across a reach eliminates jurisdiction.

• Lakes and ponds may count as tributaries.
  

This tributary framework will likely create new field disputes in arid or semi-arid California terrain.

The rule retains “adjacent” as requiring a continuous surface connection, but defines it far more narrowly:

• The wetland must abut (physically touch) a WOTUS.

• It must have surface water throughout the wet season.

• Groundwater-supported saturation no longer qualifies.

• Only the wet portions of a wetland mapped area are jurisdictional.
  

The Agencies explicitly state that wetlands lacking visible surface water most of the year “may look like dry land” and therefore fail Sackett's indistinguishability requirement.

This is a striking narrowing for California’s mosaic and seasonal wetlands, but the Agencies then propose a major modification:

Mosaic and Permafrost Wetlands Split Apart

Instead of viewing them as single systems, EPA will break them into component parts, asserting jurisdiction only over those exhibiting continuous surface water. This may create significant mapping burdens for operators.

The rule deletes “intrastate,” but maintains jurisdiction only where lakes and ponds are relatively permanent and have a continuous surface connection to a WOTUS.

Agencies are contemplating folding lakes and ponds into the “tributary” category, which may signal future regulatory consolidation.

A key definition that will drive many determinations.

• Standing or flowing water year-round or throughout the wet season

• Continuous hydrology required through the entire wet season

• Physical indicators of flow (e.g., bed and banks) are insufficient

• Agencies are open to alternative standards such as:

  • Perennial-only

  • 90-day or 270-day thresholds

  • Minimum flow rates
    

Wet season determination will rely heavily on the Antecedent Precipitation Tool (APT).

Surface connection newly defined as:

“Surface water at least during the wet season and abutting (touching) another jurisdictional water.”

Key clarifications:

• The Agencies intentionally reject “continuous surface water connection,” which would require year-round water.

• Surface water must persist predictably and without interruption throughout the wet season—except during extreme drought.

• “Wet season” ≠ “growing season.”
  

This could complicate California wetland delineations significantly.

Exclusions — What Stays Out

Waste Treatment Systems

The definition mirrors the NWPR’s version, with one change: systems designed to remove pollutants “prior to discharge or eliminating such discharge.”

• 404-authorized systems with 402 coverage remain excluded.

• Abandoned systems lose protection.
  

Prior Converted Cropland

Fully restored NWPR definition:

• Still excluded unless abandoned for 5 years and reverted to wetland conditions.

• USDA determinations recognized but not required.
  

Ditches

Ditches constructed entirely in dry land are excluded—even if they carry relatively permanent flow. Key points:

• Burden of proof rests on the Agencies, not the landowner.

• If evidence is inconclusive, the ditch is presumed non-jurisdictional.

• Ditches built in tributaries or wetlands are jurisdictional.
  

Groundwater

Explicitly excluded, including water moving through subsurface agricultural drainage systems.

Tools & Implementation, A Regulatory Maze

EPA and the Corps identify a long list of tools for WOTUS determinations:

• USGS maps

• Elevation and hydrology datasets

• NWI classifications

• Landsat Level-3 Dynamic Surface Water

• Global Surface Water Explorer

• NOAA, NRCS, USGS precipitation data

• Remote sensing and aerial imagery

• Streamflow Duration Assessment Methods
  

SDAMs, despite not being designed for relatively permanent flow determinations, will still be used as “informative.”

Multiple wet seasons in a region? The feature must have continuous surface hydrology through all of them.

What This Means for California Operators

If finalized as written:

1. More site-specific determinations, more field disputes: the wet-season standard will increase uncertainty in arid and semi-arid counties.

2. Expanded hydrology documentation requirements: operators will be expected to produce multi-season datasets, remote-sensing analyses, and historical imagery.

3. Narrower wetland jurisdiction on paper, but more complex mapping: breaking mosaic wetlands into pieces will require more intensive delineation.

4. Ditch exclusions will be heavily contested: expect case-by-case battles over “constructed in dry land.”

5. New definitions mean re-training consultants and recalibrating long-standing practices: many delineation methodologies will need updating.

Members with active or pending 404/402/401 permitting actions should contact CIPA staff for a project-specific risk review.