Water Issues on the Horizon in the Second Half of 2026
The water regulatory landscape continues to evolve rapidly as federal agencies, courts, states, and regulated entities adjust to shifting legal and policy priorities. Over the past year, the U.S. Environmental Protection Agency (EPA), the U.S. Army Corps of Engineers (the Corps), and state regulators have advanced significant changes affecting nearly every aspect of water regulation—from the scope of federal Clean Water Act (CWA) jurisdiction, Section 401 certifications, and stormwater regulation to per- and polyfluoroalkyl substances (PFAS) drinking water regulation, citizen enforcement, and emerging challenges involving water supply, infrastructure, and water rights across the western U.S.
At the federal level, agencies are moving forward with rulemakings that could reshape permitting obligations, jurisdictional boundaries, and compliance requirements for years to come. At the same time, states are stepping in to fill perceived regulatory gaps, creating a more complex and geographically varied compliance landscape. Federal courts also continue to play a central role, with recent and pending decisions influencing the interpretation and implementation of key CWA programs. As a result, companies face a regulatory environment that is simultaneously becoming narrower in some areas of federal oversight and more expansive, fragmented, and uncertain in others.
This article highlights several of the most important water law and policy developments to watch in 2026.
- WOTUS Rule Proposed Changes
- CWA Section 401 Certification Proposed Rule
- SF vs. EPA Reshaping NPDES Permits
- EPA to Propose Revisions to NPDES Rules
- Residual Designation Authority Activity
- PFAS in Water Permitting
- PFAS Drinking Water Standards
- Industrial Stormwater General Permit Reissuance Activity
- CWA Citizen Suits
- Water Rights, Supply, and Infrastructure
WOTUS Rule Proposed Changes
In November 2025, EPA and the Corps proposed a new definition of WOTUS, the threshold jurisdictional term that triggers CWA jurisdiction. As discussed in our prior alert, the proposed revisions would narrow the scope of CWA jurisdiction by clarifying the Sackett decision specifically for wetlands, tributaries, ditches, and other discrete features. Public comments on the rule raised numerous complex issues, and the Administration recently announced that it will be seeking renewed public comment on a supplemental proposal. Because the Administration will need time to review and address these new comments, it is likely that issuance of a final rule will be substantially delayed.
Several states have stepped in to fill the jurisdictional gap left by EPA’s and the Corps’ push for a narrower WOTUS definition following Sackett. Colorado is the clearest example: under HB 24-1379 and Regulation 87, the Colorado Department of Public Health and Environment (CDPHE) continues implementing Colorado’s state dredge-and-fill program for state waters, which includes standing authorizations for certain dredge or fill activities. Meanwhile, California’s Water Boards are reporting a significant shift from federal § 401 certifications to state-ordered Water Discharge Requirements (WDRs) for proposed dredge or fill activities in state waters, and to general orders intended to address Sackett. But these expansions of state authority do not always cleanly clarify questions left by federal policy changes. For example, a New York trial court recently vacated the New York Department of Environmental Protection’s new 6 NYCRR Part 664 regulations—albeit on procedural grounds—but the resulting delay between vacatur and the promulgation of new rules leaves stakeholders uncertain about how to proceed. Companies should continue to monitor state agency activities, especially for state authorizations and general permits, and build extra flexibility into project timelines to account for new state-level hurdles.
CWA Section 401 Certification Proposed Rule
In January 2026, EPA issued a Proposed Rule to revise its CWA Section 401 water quality certification regulations, as discussed in our prior alert. Comments closed February 17, 2026; EPA received over 80,000 public comments. The Unified Agenda lists a final-rule date of June 2026, but EPA has not yet sent a draft rule to OMB as of the publication of this alert, and so has missed this target.
The expansion in state programs discussed in the previous (WOTUS) section will also address at least some of the interests that the states currently protect through CWA section 401, although the state requirements may be less effective because they will not be incorporated in a federal license or permit, as would be the case under 401.
SF vs. EPA Reshaping NPDES Permits
The Supreme Court’s landmark decision in City & County of San Francisco v. EPA, 604 U.S. 334 (2025), is remaking Clean Water Act permitting for the better. The Court held that the Act does not allow EPA or states to impose so-called “end result” requirements—provisions in National Pollutant Discharge Elimination System (NPDES) permits that subject permittees to liability based on receiving waters conditions. The Court explained that the CWA requires EPA and state permitting agencies instead to specify the steps a permittee must take (e.g., implementing BMPs or meeting an effluent limitation) to ensure receiving water conditions meet applicable water quality standards.
EPA and authorized states have begun implementing San Francisco by removing end result prohibitions in both individual and general permits. For example, California’s regional water boards have ceased including so-called “receiving water limitations” intended to meet applicable water quality objectives in their NPDES permits. EPA Region 1’s permits issued in New Hampshire and Massachusetts also no longer contain boilerplate prohibitions against causing or contributing to violations of water quality standards. And Washington removed a prohibition against causing violations of water quality standards from its most recent construction general permit.
As 2026 continues, look out for two big issues. First, citizen groups have continued to allege violations of end-result prohibitions in their notices of intent. These permit terms should not be enforceable, but a district court in California held otherwise last year. S.F. Baykeeper v. City of Sunnyvale, 2025 WL 1382862 (N.D. Cal. May 12, 2025). So long as groups continue to bring actions to enforce end-result provisions, courts will have to weigh the enforceability of these terms. Second, it remains to be seen whether states will attempt to impose end-result prohibitions as non-NPDES requirements enforceable only under state law.
EPA to Propose Revisions to NPDES Rules
EPA will soon release for public comment revisions to its regulations governing the issuance of NPDES permits. Titled Updates to the National Pollutant Discharge Elimination System Definitions and Exclusions, the rule will likely do more than modernize the regulations or clarify minor issues. Under President Trump and Administrator Lee Zeldin, EPA has emphasized decreasing regulatory burdens and implementing statutes in a manner that hews closely to their plain meaning.
The draft rule will have implications for permits issued by both EPA and authorized states, and any revisions during this Administration are likely to prompt NGO opposition. It will thus be critical for the regulated community to submit robust comments supporting the proposal or suggesting alternatives that could better withstand judicial review.
Residual Designation Authority Activity
As discussed in B&D’s prior alerts on EPA Region 9 and Region 1, EPA has increasingly sought to use residual designation authority (RDA) as a vehicle to impose NPDES stormwater permitting obligations on commercial, industrial, and institutional (CII) properties that historically have not been required to obtain stormwater permit coverage. Region 9’s final designation for certain CII properties in two Los Angeles County watersheds, and Region 1’s proposed designation and draft general permit for CII properties in the Charles, Mystic, and Neponset River watersheds, reflect an asserted expansion of stormwater permitting authority that could have broader implications if implemented and allowed to stand.
With respect to the Region 9 designation, the Los Angeles Water Board noticed a July 23, 2026 public hearing to consider adoption of its revised tentative CII general permit. The hearing follows a lengthy draft-permit process: after EPA Region 9’s purported final RDA designation, the LA Water Board issued initial then revised implementing permit drafts, received public comments on those drafts, and converted the previously scheduled November 20, 2025 adoption hearing into a workshop to address unresolved stakeholder issues. According to the hearing notice, those issues included uncertainty around the regional project compliance option, applicability to mixed-use properties, owner/operator responsibility, monitoring and initial sampling requirements, timing of compliance options, recognition of existing BMPs and low-impact development, and the definition of permeability. The Los Angeles Water Board states it will not accept additional written comments before the adoption hearing, although oral comments may be provided at the July 23, 2026 hearing.
In the second half of 2026, owners and operators of potentially affected CII properties in Region 9 should consider participating in the July 23, 2026 hearing, should watch for final action on the CII general permit, and evaluate potential judicial challenge to the Region 9 designation or implementing permit.
PFAS in Water Permitting
EPA continues to expand its toolbox for PFAS regulation under the CWA, though it has not yet finalized nationally applicable PFAS effluent limits for most industrial categories.
EPA issued guidance in April 2022 for addressing PFAS in NPDES permits and pretreatment programs in the limited jurisdictions where EPA is the permit-issuing agency or the pretreatment control authority. Eight months later, EPA issued similar guidance for states authorized to issue NPDES programs. Though this is only guidance, EPA can use measures such as this to pressure NPDES-authorized states to follow its PFAS policy even if it is not an enforceable federal regulation.
The agency’s 2023 Effluent Guidelines Program Plan 15 announced EPA’s intent to initiate a POTW Influent Study of PFAS, focusing on collecting nationwide data on industrial discharges of PFAS to POTWs, including categories recently reviewed. In 2024, EPA finalized recommended aquatic life water quality criteria for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS).
In January 2025, EPA proposed two methods to screen for PFAS compounds—Method 1633A and Method 1621—for addition to the approved methods under CWA regulations. Until EPA promulgates those methods through rulemaking, they are not nationally required for CWA compliance monitoring. EPA has nonetheless recommended Method 1633A for use in NPDES permits and has identified Method 1621 as a complementary screening method that may be used where appropriate.
In the meantime, states have pressed ahead with incorporating PFAS-related requirements into Clean Water Act permits. Notably, the Minnesota Pollution Control Agency’s 2025 Multi-Sector General Permit for Industrial Stormwater requires permitted facilities in certain industries to monitor PFAS in their stormwater runoff or snow and, depending on the levels, implement a source and exposure reduction plan.
As EPA and states continue to develop PFAS permitting tools, regulated entities should track evolving requirements and evaluate how PFAS pretreatment and monitoring obligations may affect future compliance planning.
PFAS Drinking Water Standards
On May 18, 2026, EPA announced two proposed rules that, if finalized, could reshape near-term implementation of PFAS drinking water requirements under the federal Safe Drinking Water Act (SDWA).
First, EPA proposed to retain the 4.0 parts per trillion (ppt) Maximum Contaminant Levels (MCLs) for PFOA and PFOS, while establishing a federal exemption framework that would allow eligible public water systems to request up to two additional years—until April 26, 2031—to comply with those enforceable limits. The proposed exemption would apply to qualifying systems in states, territories, or Tribes that have not obtained primacy for the PFOA and PFOS MCLs, and the extension would not be automatic. EPA states that PFOA and PFOS monitoring and reporting obligations would remain subject to the timeframes established in the April 2024 PFAS National Primary Drinking Water Regulation.
Second, EPA proposed to rescind its regulatory determinations and remove related federal requirements for PFHxS, PFNA, HFPO-DA, commonly known as Gen-X, and the Hazard Index for mixtures containing two or more of PFHxS, PFNA, HFPO-DA, and PFBS. EPA’s proposal would rescind associated Maximum Contaminant Level Goals (MCLGs), MCLs, and regulatory provisions specific to those PFAS, but would not affect the PFOA and PFOS MCLs or related PFOA/PFOS monitoring and reporting requirements.
EPA’s proposals suggest that PFAS drinking water obligations may increasingly be shaped by implementation timing, state primacy, and state-specific standards rather than solely by federal rulemaking. Regulated entities should pay close attention to how EPA’s proposals translate into state-level drinking water requirements. Even if EPA extends the PFOA/PFOS compliance deadline or rescinds federal requirements for certain other PFAS, these impacts may differ from state to state. Stakeholders should monitor EPA’s final rules and state implementation decisions as water systems move from PFAS monitoring to compliance planning.
Industrial Stormwater General Permit Reissuance Activity
Industrial facilities and municipalities with industrial stormwater operations should monitor several important general permit developments over the next six months. The most immediate state watch items are in Oregon, Texas, and Louisiana, while EPA’s federal Multi-Sector General Permit remains in administrative continuation pending final action on the proposed 2026 MSGP.
At the federal level, EPA has not yet finalized the 2026 MSGP. EPA issued the proposed 2026 MSGP to replace the 2021 MSGP, but the comment period closed in May 2025, and the final permit remains pending. Because the 2021 MSGP expired on February 28, 2026, EPA has administratively continued the permit for facilities and operators that had coverage prior to its expiration.
Several state permits also warrant attention. Oregon’s 1200-Z industrial stormwater general permit reissuance is in the final stage, with the state targeting final issuance in July 2026 and requiring current registrants to renew coverage to continue discharging after the existing permit term. Oregon is also moving through the reissuance process for its 1200-A and WPCF 1000 permits for certain mining and nonmetallic mineral operations, with additional public engagement expected this fall. In Texas, the TCEQ Multi-Sector General Permit is scheduled to expire in August 2026, and the renewal process is already underway. Louisiana’s LAR050000 Multi-Sector General Stormwater Permit is scheduled to expire in October 2026 and should be watched for draft permit and public notice activity.
Where draft permits are open or expected, facilities and municipalities should consider whether proposed changes could affect sampling frequency, benchmarks, sector-specific requirements, corrective-action triggers, or reporting obligations. These issues are also relevant to citizen-suit risk because plaintiffs increasingly rely on publicly available reporting documents and data to identify potential targets.
CWA Citizen Suits
Clean Water Act citizen suits are not new, but increased public access to compliance reporting records via state agency databases has made it easier for citizen groups to identify potential targets.
In the second half of 2026, companies should expect continued attention to CWA compliance issues reflected in the public record, including recurring effluent limitation exceedances or gaps in mandatory reporting documents. Companies may benefit from reviewing publicly available compliance information with an eye toward how it could be characterized by a potential citizen-suit plaintiff. A key question is not only whether a facility is in compliance, but whether the public record clearly documents the basis for that position.
Water Rights, Supply, and Infrastructure
Western states are seeing tensions rise as water supply falls. The growing mismatch between demand and declining supply, and between decentralized legal entitlements and operational realities, will create both operational and legal challenges for water users. The Colorado River and Rio Grande Basins exemplify the problem. Persistent aridity, reduced snowpack, and shrinking reservoir storage increase the likelihood of curtailments, changes to reservoir operations, and disputes over delivery obligations. Meanwhile, Tribal water rights settlements provide greater clarity but increased demand.
In the Colorado River Basin, high aridity and low snowmelt continue pushing the reservoir system towards collapse, with an approximately 2.59 million acre-foot gap between the River’s natural supply and consumptive use. With the threat that low reservoir levels pose to hydropower generation and other critical infrastructure, Reclamation faces a seemingly impossible task: maintaining storage and meeting downstream delivery obligations. But absent demand reductions (or significant hydrologic recovery that could only be described as divine intervention), Law‑of‑the‑River delivery requirements pose a real risk of forcing the system into de facto “run‑of‑the‑river” operations.
Major water users within the Colorado River basin should prepare for major curtailment measures imposed by Reclamation or the Basin States, with Reclamation’s “Post-2026 Operational Guidelines and Strategies for Lake Powell and Lake Mead” offering an excellent starting point. Litigation is likely, so interested stakeholders should prepare to review the forthcoming Record of Decision and either analyze venue options, monitor federal district court dockets for intervention opportunities, or wait to see if anyone dares to trigger the Supreme Court’s original jurisdiction under the Colorado River Basin Act.
Rio Grande Basin water users face similar challenges, raising questions about how the Basin’s states will meet their delivery obligations. (Per Reclamation, Elephant Butte Reservoir currently oscillates around 13% capacity.) Even with the groundwater-accounting and compliance framework approved in the settlement of Texas v. New Mexico, it remains unclear whether the new regime will materially improve deliveries or simply formalize the scarcity. Either way, it cannot cover the underlying supply shortfall, and a flood of water-related disputes will likely follow. Stakeholders whose operations require a consistent supply should evaluate alternative sources, conservation measures, and operational contingency plans, and also monitor federal and state actions to implement the new settlement’s terms. Managed aquifer recharge (MAR) and conjunctive use are emerging as core structural adaptations that may have some promise. Existing programs in Arizona (CAP recharge) and California (SGMA‑driven basins) suggest that underground storage is viable, but these approaches also raise novel concerns about ownership, allocation, and accounting.
Beveridge & Diamond advises clients on the full spectrum of Clean Water Act issues, including jurisdictional determinations, Infrastructure, Project Development, and Permitting Practices, Enforcement Risk, and Litigation. Our Water practice helps navigate the complexities of federal and state regulatory interpretations as agencies and courts continue to reshape the scope of WOTUS. For more information, please contact the authors.
