In its recent decision in Waterkeeper Alliance v. U.S. Environmental Protection Agency, No. 23-636 (9th Cir. June 18, 2025), the Ninth Circuit Court of Appeals held that the Environmental Protection Agency (EPA) failed to properly consider important factors in refusing to revise technology based “Effluent Limitations, Guidelines, and Standards” (ELGs) for seven industrial categories under its Effluent Guidelines Program Plan 15. This decision suggests that industries should keep a watchful eye on other ELG modifications in the future that might fundamentally change their discharge requirements.
The Clean Water Act (CWA) requires EPA to develop ELGs that set national regulatory standards for sources that discharge directly to Waters of the United States (WOTUS) and indirectly though treatment works. These ELGs are then incorporated into National Pollutant Discharge Elimination System (NPDES) permits.
The CWA requires that EPA periodically review and, if appropriate, revise these ELGs. Every two years, EPA reviews its existing ELGs through public notice and comment, and develops a new program plan that identifies which, if any, ELGs will be revised or subjected to further study. The Plaintiffs in Waterkeeper alleged that EPA should have, but did not, revise source ELGs for seven industrial categories:
- Fertilizer Manufacturing;
- Inorganic Chemical Manufacturing;
- Nonferrous Metals Manufacturing;
- Organic Chemicals, Plastics, and Synthetic Fibers Manufacturing;
- Pesticide Chemical Manufacturing;
- Petroleum Refining; and
- Plastics Molding and Forming Facilities. Waterkeeper, No. 23-636, slip op. at 6.
The Ninth Circuit partially agreed, holding that EPA’s focus “must be to identify whether each ELG is outdated, in the sense that it does not conform with the [Clean Water] Act’s substantive requirements for that ELG.” Id. at 39-40. Thus, although EPA “was not required, as part of its periodic review, to revise an ELG simply because it was out of date or not comprehensive,” id. at 35, the Ninth Circuit seized on the Supreme Court’s recent decision in Loper Bright Enterprises v. Raimondo, 603 U.S. 369 (2024), and observed that the agency’s discretion on when to revise ELGs is controlled by the substantive provisions of the CWA—“[t]he goal is to have ELGs that conform to those substantive requirements, and to the extent an ELG does not conform with those requirements revision would presumptively be appropriate.” Waterkeeper, No. 23-636, slip op. at 38.
The Ninth Circuit concluded that EPA failed to consider three important factors when it chose not to revise the seven industrial ELGs.
- Advances in pollution control technology
The Ninth Circuit reasoned that, since ELGs are technology-based standards, “[w]hether it is ‘appropriate’ to ‘revise’ an ELG must turn, at least to an extent, on some consideration of developments in pollution control technology.” Id. at 40-41. However, EPA used a Category Ranking Analysis, which did not include any consideration of technological developments.
- Pretreatment standards and guidelines applicable to indirect dischargers
The Ninth Circuit concluded “[a]t bottom, EPA could not have reasonably carried out its obligations to review pretreatment standards and guidelines for the Seven Industrial Categories by relying exclusively on the Category Ranking Analysis,” id. at 49, because “EPA did not consider pollution from indirect dischargers,” id. at 70, which “cast[] substantial doubt on the ability of the Category Ranking Analysis to carry out its stated purpose of ‘prioritiz[ing] revisions on the basis of where they will do the most good.’” Id. at 47. EPA failed to explain why it could rely on data from direct dischargers to make decisions about pretreatment standards and guidelines applicable to indirect dischargers.
- Information relating to pollutants not currently covered by applicable ELGs
Finally, the Ninth Circuit reasoned that “[j]ust as some consideration of the extent to which an ELG is out of date is necessary to determine the benefits of revision, so too some consideration of the extent to which an ELG is underinclusive is also necessary.” Id. at 51. Yet EPA apparently collects little data on the discharge of pollutants not currently covered by the applicable ELGs, thus preventing EPA from “determin[ing] where a rulemaking would ‘produce the most significant benefits.’” Id. The Ninth Circuit concluded that “EPA must give at least some consideration to this aspect of the problem in order for its analysis to comport with the minimum requirements of rationality,” id. at 51, yet EPA failed to do so and thus “failed to consider an important aspect of ELGs and the CWA.” Id. at 52.
The Ninth Circuit remanded the case to EPA for further proceedings, either “to reconsider its decision or provide a fuller explanation.” Id. at 62. EPA is currently midway through developing the final Program Plan 16, having published Preliminary Plan 16 in December 2024 and taken public comment on this draft plan through January 17, 2025. At present, it appears that Preliminary Plan 16 does not include revisions to ELGs. Given the advanced stage of Preliminary Plan 16, EPA may address the Waterkeeper issues separately or attempt to fold its reconsideration or fuller explanation into Preliminary Plan 17.
