by Ankur Tohan and Rachel Aramburu
Few environmental terms have been contested as hotly as “Waters of the United States” (WOTUS). WOTUS is the Clean Water Act’s (CWA) jurisdictional boundary: it determines which rivers, streams, wetlands, and other aquatic features fall under federal regulation by the U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers (the Corps). For mining, that boundary drives whether federal permits are needed, how long reviews may take, and what mitigation and compliance obligations attach.
EPA and the Corps have proposed revisions to the WOTUS definition intended to align the regulations with the U.S. Supreme Court’s 2023 decision in Sackett v. EPA. The proposal would narrow federal jurisdiction in several ways. But it also elevates an unresolved concept that may become the next permitting battleground: the “wet season.”
Why WOTUS matters
Mine construction and operations routinely interact with waters and aquatic features – access roads and crossings, pads and facilities, tailings and waste rock areas, diversions, stormwater controls, and dewatering or other discharges. If affected features are WOTUS, common federal triggers include:
- CWA Section 404 dredge-and-fill permits (fills, crossings, impoundments, and certain placement activities); and
- CWA Section 402 National Pollutant Discharge Elimination System permits for regulated discharges.
These permits can extend schedules, require avoidance and minimization, trigger compensatory mitigation, and impose monitoring and reporting. If a feature is not WOTUS, primary oversight may shift to state or local authorities, often with different timelines and standards. In many mining regions – especially the arid and semi-arid West – ephemeral channels, intermittent drainages, and seasonal wetlands are common, so small jurisdictional shifts can have outsized project impacts.
The Sackett decision
The proposed rule builds directly on Sackett v. EPA. In Sackett, the Court rejected broader jurisdictional theories and emphasized physical, surface-water connectivity. Federal jurisdiction extends only to:
- Relatively permanent bodies of water that are traditional navigable waters or connected to them; and
- Wetlands that have a continuous surface connection to such waters, making the wetland difficult to distinguish from the jurisdictional water.
The focus is on relatively permanent surface-water and surface connections, not functional or ecological relationships.
The proposed rule
The proposal seeks to codify Sackett by narrowing covered waters and adding definitions for key terms.
Relatively Permanent Waters
“Relatively permanent” would mean surface waters that stand or flow continuously year-round, or at least during the wet season. That qualifier matters: a water need not be perennial to be covered, but it must have more than short-lived, storm-driven flow. Most ephemeral features (flow only in direct response to precipitation) would generally be excluded, and some intermittent features may also fall outside jurisdiction, depending on how “wet season” is identified for the region.
The proposal would also limit jurisdictional tributaries. Tributaries would be covered only if they have a relatively permanent flow and connect to a downstream traditional navigable water (or the territorial seas, or an impoundment of a jurisdictional water) through waters that also convey relatively permanent flow. As a result, many minor drainages and dry channels encountered on mine sites – particularly where flow is episodic or routed through non-qualifying features – would not be WOTUS.
Continuous Surface Connection (Wetlands)
Wetlands would be regulated only when they directly abut (touch) a jurisdictional water and have surface water at least during the wet season, such that the wetland is effectively indistinguishable from the adjacent jurisdictional water. Subsurface hydrologic connections – groundwater exchange, shallow interflow, or periodic saturation – would not be enough.
The proposal also clarifies that certain interruptions in relatively permanent surface flow, such as dams, dikes, roads, or similar barriers, can sever jurisdictional connections. Likewise, discrete conveyances (pipes, culverts, or engineered channels) do not create jurisdiction merely because they transport water.
New Exclusions
The proposal would expressly exclude groundwater from WOTUS. Groundwater may still matter under other regulatory programs, but it would not establish CWA jurisdiction.
The proposal would also remove “interstate waters” as an independent jurisdictional category. A water would not be WOTUS merely because it crosses a state line; it must still satisfy the relatively permanent or continuous surface connection criteria. For mines near borders, this may reduce federal permitting needs in some settings, but it increases the importance of documenting site hydrology.
The Missing Definition: “Wet Season”
Although the proposal narrows jurisdiction, it does not define “wet season.” Instead, wet season operates as a limiting benchmark embedded in two definitions.
First, a waterbody is “relatively permanent” only if it is standing or continuously flowing year-round, or at least during the wet season. This draws a line between ephemeral features (generally excluded) and intermittent streams that flow reliably during wet periods (potentially jurisdictional).
Second, for a wetland to qualify as WOTUS, it must (a) abut a jurisdictional water and (b) have surface water at least during the wet season, making it difficult to distinguish from the jurisdictional water. Wetlands connected only via groundwater, subsurface flow, or rare storm events would be excluded – even if they provide downstream water-quality or flood-storage functions.
EPA has indicated that wet season would be determined case by case and would vary by region, relying on agency experience, site-specific field indicators, and available precipitation and hydrologic data.
For mining operators, that approach has two practical effects:
- It may reduce federal permitting where features wet up only during short storm events or where wetlands lack a seasonal surface connection.
- It can increase uncertainty for borderline
intermittent channels and seasonally connected wetlands – especially where wet seasons are short
or variable, where year-to-year precipitation timing changes observed flow duration, where climate variability is shifting patterns, or where baseline records are limited.
In close cases, jurisdictional determinations may turn on the quality of site observations and data and on how individual Corps districts interpret wet-season indicators.
Practical takeaway
Overall, the proposed rule continues a shift toward a narrower, surface-water-focused view of Clean Water Act jurisdiction. Ephemeral channels, many intermittent drainages, isolated wetlands, and engineered conveyances are more likely to fall outside federal jurisdiction than under prior approaches, potentially reducing federal permitting burdens for some mining projects.
But uncertainty is not eliminated. Until “wet season” is defined – or at least applied consistently – jurisdictional determinations will remain site-specific.
Therefore, for project planning, miners should (1) screen drainage networks and wetlands early; (2) time fieldwork to seasonal conditions; and (3) build a defensible hydrology record (include photographic logs, precipitation history, remote sensing, and, where feasible, flow or stage monitoring) to support jurisdictional determinations and permitting strategy.
EPA is expected to issue a final rule later this year.
Ankur Tohan is an environmental and energy lawyer for Stoel Rives, based in Seattle, Wash. His experience spans working for the U.S. EPA and 15 years of private practice. He has focused his practice on supporting clients with carbon capture and sequestration projects, renewable fuels, waste-to-energy facilities, carbon credit, and offset transactions.
Rachel Aramburu is an associate in Stoel Rives’ Boise, Idaho, office, where she counsels clients on environmental and regulatory matters. Her practice includes compliance assistance, enforcement defense, permitting support, and environmental due diligence in mergers and acquisitions.