The Environmental Vanguard is a quarterly newsletter from McGuireWoods, bringing key insights from leading environmental attorneys and consultants at the forefront of regulatory, litigation and policy developments. This issue covers the proposed rule to revise the definition of “waters of the United States” under the Clean Water Act. It also discusses important updates impacting the Chemical Safety and Hazard Investigation Board, the Toxic Substances Control Act, the Clean Air Act and coal ash disposal under the Resource Conservation and Recovery Act.
Look for new editions every quarter and feel free to reach out to the McGuireWoods team with questions about litigation, regulatory, enforcement or other environmental law issues.
I. EPA and U.S. Army Corps Propose Revised WOTUS Definition After Sackett
On Nov. 17, 2025, the EPA and the U.S. Army Corps of Engineers announced a proposed rule to revise the definition of “waters of the United States” (WOTUS) under the Clean Water Act in response to the U.S. Supreme Court’s 2023 decision in Sackett v. Environmental Protection Agency. The agencies stated that the proposal aims to “provide greater regulatory certainty and increase Clean Water Act program predictability and consistency by clarifying the definition of ‘waters of the United States.’” EPA Administrator Lee Zeldin emphasized the need to set “clear and practical rules of the road that accelerate economic growth and opportunity.” The agencies stated that the proposal is intended to “restore and maintain the quality of the Nation’s waters while respecting State and Tribal authority over their own land and water resources.”
The proposed rule outlines the categories of waters that would fall within federal jurisdiction. As summarized by the agencies, WOTUS “would include (1) traditional navigable waters and the territorial seas; (2) most impoundments of “waters of the United States;” (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. The agencies are also proposing to amend the exclusions for waste treatment systems, prior converted cropland, and certain ditches, and to add an exclusion for groundwater.”
The proposal introduces and clarifies key terms that will guide jurisdictional determinations post-Sackett:
- Relatively permanent: Proposed to include features “standing or continuously flowing bodies of surface water that are standing or continuously flowing year-round or at least during the wet season.” The “wet season” construct “is intended to include extended periods of predictable, continuous surface hydrology occurring in the same geographic feature year after year.”
- Continuous surface connection: Proposed to mean “having surface water at least during the wet season and abutting (i.e., touching) a jurisdictional water.”
- Tributary: Proposed to 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.” The proposal clarifies that a tributary “does not include a body of water that contributes surface water 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. When the tributary is part of a water transfer (as that term is applied under 40 CFR 122.3) currently in operation, the tributary would retain jurisdictional status.”
The proposed rule’s revised definitions and expanded exclusions for federal jurisdiction, including clarifications on groundwater, ditches, waste treatment systems and prior converted cropland, could significantly reshape which water features and wetlands are subject to federal oversight. If finalized, these changes could have far-reaching effects on landowners, farmers and developers in the regulatory roles of states and tribes. Stakeholders with ongoing or planned permitting under Clean Water Act Sections 402 and 404 should closely evaluate how the updated definitions and exclusions may affect jurisdictional determinations, especially regarding conveyances, breaks in surface connectivity and seasonal hydrology.
The agencies are soliciting public comment on the proposed rule for 45 days once published in the Federal Register. The EPA and the Army Corps will host two hybrid public meetings on the updated definition of WOTUS.
II. Trump Administration Proposes Closing Chemical Safety Hazard Investigation Board
In further efforts to downsize the federal government, President Donald Trump proposed eliminating the Chemical Safety Hazard Investigation Board (CSB). The CSB’s role is to make safety recommendations after root-cause investigations to prevent future chemical releases. As an independent nonregulatory federal agency, its investigations do not result in the issuing of fines, citations or jail time.
While the CSB has no authority to create or enforce the policy recommendations it makes as a result of its investigations, the investigations themselves can bring significant negative publicity and cause substantial business disruptions. In recent years, reportable incidents were shared publicly on the CSB’s website, including animated reenactment videos of chemical release incidents.
Since 1998 the CSB has issued more than 1,000 recommendations to address safety issues causing chemical release incidents. The CSB most recently released a final report on Sept. 25, 2025, detailing its investigation in an accidental anhydrous ammonia release at Cuisine Solutions, a prepared foods manufacturer, in Sterling, Virginia. Trump’s budget proposal will put similar investigations to an end.
The Trump administration proposed eliminating funding to the CSB “as part of the Administration’s plans to move the Nation towards fiscal responsibility and to redefine the proper role of the Federal Government.” The balance of the CSB’s remaining funds were directed to be used for “expenses necessary to carry out the closure of the Board.” Id. at 1048.
The Trump administration argues the CSB is duplicative of other agencies such as the EPA and OSHA. This argument is reinforced by the fact that the CSB has no authority to create or enforce the policy recommendations from its studies. Supporters of the CSB counter that the nonregulatory nature of the CSB is intentional and works to ensure broad enhancements for public safety that only independent investigations can bring.
If Congress adopts the president’s recommendation and closes the CSB, businesses will see a reduction in negative publicity after accidental chemical releases and face less confusion caused by oversight from multiple agencies. However, businesses will still be subject to investigation by the EPA, OSHA or other agencies with jurisdiction after accidental chemical release incidents. Businesses also will continue to face potential liability.
III. EPA Proposes Updates to Chemical Risk Evaluation Process Under TSCA
On Sept. 22, 2025, the EPA published a proposed rule to revise how it evaluates risks of chemicals already in commerce under the Toxic Substances Control Act (TSCA). Zeldin stated the proposal brings a “clear, predictable, commonsense approach” that supports safety and economic growth, in line with Trump’s Executive Order 14219 and the administration’s “Powering the Great American Comeback” agenda. The proposed rule revises elements of the 2024 regulation, Procedures for Chemical Risk Evaluation under TSCA.
Proposed changes include:
- Requiring risk determinations for each condition of chemical use, not just the substance as a whole.
- Clarifying how worker protections (e.g., PPE, industrial controls) are considered.
- Outlining the EPA’s discretion in selecting uses and exposure pathways to evaluate.
- Updating definitions and processes to ensure transparency and meet legal deadlines.
- Adjusting requirements for manufacturers requesting EPA-led risk evaluations.
The public comment period for the proposed rule ended on Nov. 7, 2025.
IV. EPA Considers Revoking Endangerment Finding
In 2009, the EPA issued the Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act — known as the “Endangerment Finding” — which concluded that greenhouse gases pose a threat to public health and supported regulation of greenhouse gas emissions from motor vehicles. EPA later made generally similar endangerment findings to support regulation of greenhouse gas emissions from various industries, such as power plants and oil and gas facilities. The Finding listed six greenhouse gases for the danger they pose together to public health and welfare: carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride.
The Endangerment Finding traces back to the 2007 U.S. Supreme Court decision in Massachusetts v. EPA, which held that greenhouse gases are pollutants under the Clean Air Act and directed the EPA to determine whether they endanger public health and welfare under Section 202 of the Clean Air Act. The EPA’s determination that six greenhouse gases meet the endangerment criteria enabled the agency to regulate emissions from vehicles. The U.S. Court of Appeals for the D.C. Circuit upheld the Finding and the Supreme Court declined review. The Finding has since served as the legal cornerstone of federal climate action.
On July 29, 2025, the EPA proposed revoking the Endangerment Finding. Without the Endangerment Finding, the EPA lacks authority under Section 202 of the Clean Air Act to set emission standards for new motor vehicles and engines. The EPA simultaneously proposed eliminating greenhouse gas emission regulations for vehicles.
Under the proposal, engine and vehicle manufacturers would no longer have future obligations to measure, control or report greenhouse gas emissions for any highway engines or vehicles, including model years produced before the proposal. The EPA would, however, keep in place rules governing criteria pollutant and air toxic testing and standards, Corporate Average Fuel Economy testing, and related fuel economy labeling requirements.
The EPA asserted that, if adopted, the proposal would remove the legal foundation for an estimated $1 trillion in costly regulations and yield more than $54 billion in annual savings. The EPA contends that sweeping vehicle greenhouse gas regulations created major uncertainties and substantial costs for the auto industry. According to the EPA, revoking the Endangerment Finding would deliver greater certainty and regulatory relief so that companies can plan effectively, giving consumers greater access to affordable vehicle choices.
The deadline for public comments on the EPA’s proposal to rescind the Endangerment Finding was Sept. 22, 2025. With the federal shutdown, a decision on revoking the Endangerment Finding may be delayed until early 2026.
V. EPA Extends Deadlines for Coal Ash Groundwater Monitoring
On July 17, 2025, the EPA issued a direct final rule and companion proposal that will extend the compliance deadlines for coal combustion residual (CCR) management unit (CCRMU) requirements under new CCR regulations that went into effect in November 2024. In the announcement, Zeldin stated that the rule would assist in keeping energy affordable and reliable by providing “much needed regulatory relief for the power sector.”
Under the 2024 CCR rule, certain areas of CCR disposal outside regulated units, as well as certain legacy CCR surface impoundments, will become subject to groundwater monitoring, corrective action, closure and post-closure care requirements regardless of how or when that CCR was placed. Facility owners are required to conduct facility-wide evaluations to determine whether any CCRMUs exist on-site that contain greater than one ton of CCR.
The original deadline for these evaluations was February 2026. The EPA agreed to give companies an extra year, until Feb. 8, 2027, to inspect and report on their coal ash impoundments, while companies have until Aug. 8, 2029, to install groundwater monitoring systems. The remaining interrelated CCRMU compliance deadlines were also extended.
Originally, coal power plant operators were required to submit part one of their Facility Evaluation Report (FER Part 1) on Feb. 9, 2026. The second report (FER Part 2), which involves a physical evaluation of the facility, was due on Feb. 8, 2027. Under the 2025 direct final rule, facility owners may now opt to combine FER Part 1 and FER Part 2 into a single submission due Feb. 8, 2027.
The EPA determined an extension was necessary after receiving consistent reports of industrywide shortages of qualified contractors as well as issues with the aging infrastructure of the industry. Many existing records are physical documents in poor or illegible condition. The EPA determined that a robust monitoring plan should not proceed until all CCRMUs are identified and mapped under the FER process, which will take larger operations additional time.
VI. Courts Uphold EPA’s Interpretation of Coal Ash Closure Requirements
Subtitle D of the Resource Conservation and Recovery Act addresses the disposal of solid and hazardous waste, including coal ash, in the United States. The EPA promulgated the first coal ash disposal regulation in 2015. The 2015 rule established the process for closing CCR units that begin to contaminate groundwater. In 2020, an amendment to the 2015 rule reclassified unlined coal-residual units as “open dumps” requiring their closure beginning April 11, 2021, but permitted extensions up to Oct. 15, 2024, if owners could show compliance with all other requirements. In 2024, another amendment regarding “legacy ponds” included updates to the definitions of “liquids” and “infiltration.”
Gavin Power sought an extension of the April 11, 2021, deadline to close one of its CCR units. The EPA denied the extension request, in part, due to Gavin Power’s failure to comply with closure requirements on a separate closed coal-residual unit. Gavin Power had an unlined, closed coal-residual unit where coal ash was up to 40% flooded with groundwater.
Gavin Power appealed to the D.C. Circuit, arguing that the EPA amended the 2015 Rule to create a new waste-in-place closure requirement by prohibiting any groundwater saturation. The D.C. Circuit held that the minimize-groundwater-saturation requirement was clear from the text of the 2015 Rule, and no new legislative rule was created in denying Gavin Power an extension. See Elec. Energy, Inc. v. Envtl. Protec. Agency, 106 F.4th 31 (D.C. Cir. 2024).
Gavin Power attempted to bring an Administrative Procedure Act case before the Southern District of Ohio alleging that the EPA retroactively applied amendments to the 2015 rule to label Gavin Power a “significant noncomplier.” On Aug. 26, 2025, Judge Michael H. Watson entered an order in Gavin Power, LLC v. EPA. Judge Watson agreed that the minimize-groundwater-saturation requirement was not new; instead, the 2015 Rule always required units closed with waste-in-place to minimize inflow and outflow of groundwater. Watson held that this would be the case based on the plain text and following issue preclusion from the D.C. Circuit’s decision.
Citing SEC v. Chenery Corp., 332 U.S. 194, 203 (1947), Watson further held that, even if the EPA could be said to be applying a new principle retroactively, the EPA could do so when the “mischief of producing a result which is contrary to a statutory design or to legal and equitable principles” is greater than the “ill effect of the retroactive application.”
VII. Data Centers
The EPA announced an expedited chemical review for data centers to facilitate domestic expansion in AI. The EPA effort is accompanied by an executive order, “Accelerating Federal Permitting of Data Center Infrastructure.” The EPA hopes to get through what it has characterized as a “massive backlog of new chemical reviews” slowing down data center and AI projects.
Newly developed chemicals that the industry wants to use, such as per- and polyfluoroalkyl substances for specialized cooling systems, are subject to environmental and health reviews under the Toxic Substances Control Act (TSCA). Any chemical that is not on the TSCA Inventory is considered a “new chemical substance.” If a chemical creates an “unreasonable risk,” it can be restricted by the EPA. Supporters of the change contend that the current process was not transparent and unreasonably slowed down business development.
The new expedited process will likely benefit other industries, such as the fossil fuel, nuclear and semiconductor industries, as they have corresponding business with qualifying projects.
The environmental team at McGuireWoods helps clients navigate complex regulatory challenges, permitting, enforcement actions, litigation, and crisis response across air and climate, water, waste, and natural resources. McGuireWoods Consulting adds critical depth with lobbying, policy advocacy, and site selection and incentive negotiations, helping businesses manage risk and capitalize on opportunities in a shifting regulatory landscape.For questions or to discuss these topics in more detail, reach out to any of the authors or your McGuireWoods or McGuireWoods Consulting contact.
Learn more about McGuireWoods’ environmental practices, including Environmental Litigation, Environmental Enforcement & Regulatory Counseling, Crisis Management & Incident Response, and McGuireWoods Consulting.