## Facts

- EPA designated portland cement plants as a source category that significantly contributes to air pollution affecting public health or welfare.
- EPA promulgated Clean Air Act § 111 “standards of performance” for new or modified portland cement plants, primarily addressing particulate emissions.
- In the notice of proposed rulemaking, EPA summarized test results supporting the proposed standard but did not disclose test-site details or the methodology used.
- During the comment period, EPA conducted additional tests but did not disclose the underlying details until after issuing the final rule.
- After promulgation, EPA issued supplemental disclosures identifying the type of control technology tested and later provided dates, locations, and methodology.
- Cement manufacturers contended the standard relied on limited testing (including heavy reliance on a single successful test), did not account for differences among plant processes (e.g., wet vs. dry), and did not adequately consider costs and adverse impacts.
- After a remand allowing additional comment, EPA accepted further submissions into the record but did not meaningfully respond or revise the standard.

## Issues

1. Whether EPA’s § 111 standard reflected the degree of emission limitation achievable by the “best system of emission reduction” that had been “adequately demonstrated,” taking account of cost.
2. Whether EPA’s notice-and-comment procedure was defective because it failed to disclose the technical basis (data and methodology) in time for meaningful comment and failed to address significant comments.
3. Whether EPA was required to prepare a NEPA environmental impact statement for § 111 performance standards.

## Decision

- The court did not vacate the performance standards but remanded to EPA for further proceedings and clarification.
- The court held the rulemaking record and explanation were inadequate because EPA did not timely disclose the underlying test data and methodology supporting the standard.
- The court directed EPA on remand to provide a fuller explanation of how the statutory criteria were satisfied, including technological feasibility across the source category and consideration of costs.
- The court required EPA to respond to significant comments and criticisms rather than merely placing them in the record.
- The court rejected the NEPA challenge, concluding that § 111 rulemaking under the Clean Air Act was the functional equivalent of NEPA analysis in this context, so a separate EIS was not required.

## Legal Principles

- Under Clean Air Act § 111, a performance standard must reflect emission limitations achievable through the best system of emission reduction that the Administrator finds adequately demonstrated, taking account of cost.
- “Adequately demonstrated” requires a reasoned, evidence-based determination supported by a record sufficient to justify applying the standard to the regulated source category; speculative extrapolation from sparse testing is insufficient without an adequate explanation.
- In technical informal rulemaking, an agency must disclose in time for comment the critical data, methodology, and assumptions on which a proposed rule relies, so interested parties can provide meaningful comments.
- An agency must respond to significant comments that bear on the rule’s basis, feasibility, or costs; post-promulgation disclosure that prevents effective participation is a procedural defect warranting remand.
- Where a specific environmental regulatory statute requires environmental consideration through its own procedures and substantive mandates, those requirements may serve as the functional equivalent of NEPA, obviating a separate EIS for the action at issue.

## Conclusion

The D.C. Circuit remanded EPA’s § 111 performance standards for new or modified portland cement plants because EPA failed to timely disclose the technical record and to provide a sufficiently reasoned explanation demonstrating that the standard was adequately supported and cost-considered, while holding that a separate NEPA EIS was unnecessary because the Clean Air Act’s § 111 process functioned as NEPA’s equivalent for this rulemaking.


Portland Cement Ass’n v. Ruckelshaus, 486 F.2d 375 (D.C. Cir. 1973)