## Facts

- EPA amended the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) in 1990–1991 to implement CERCLA § 121 for Superfund remedial actions.
- The revisions treated drinking-water Maximum Contaminant Levels (MCLs) and related requirements as “applicable or relevant and appropriate requirements” (ARARs) for groundwater remediation, while treating Maximum Contaminant Level Goals (MCLGs) as goals rather than mandatory endpoints.
- EPA adopted a carcinogen risk-management policy generally accepting remedies within an excess lifetime cancer-risk range of 10⁻⁴ to 10⁻⁶, using 10⁻⁶ as a point of comparison rather than a fixed minimum.
- The NCP clarified that remedy selection considers multiple criteria, including overall protection, long-term effectiveness and permanence, reduction of toxicity/mobility/volume, short-term effectiveness, implementability, and cost.
- Ohio and other states, joined by additional intervenors and petitioners, filed consolidated petitions for review in the D.C. Circuit challenging these NCP provisions as inconsistent with CERCLA.

## Issues

1. Whether CERCLA § 121 requires EPA to mandate attainment of MCLGs (including zero MCLGs for carcinogens) rather than allowing compliance with MCLs as cleanup standards.
2. Whether EPA may consider cost and feasibility as part of determining what is “protective” under CERCLA, rather than treating protectiveness as purely health-based.
3. Whether CERCLA requires EPA to prioritize permanence over cost in selecting remedial actions.
4. Whether EPA’s adoption of a 10⁻⁴ to 10⁻⁶ cancer-risk range, including acceptance of remedies near 10⁻⁴, is unlawful or arbitrary and capricious under CERCLA.

## Decision

- The court (per curiam) largely upheld the challenged NCP revisions and denied the petitions for review on the core remedial-standard issues.
- The court rejected the argument that CERCLA compels EPA to require MCLGs, including zero MCLGs for carcinogens, as mandatory cleanup levels in all circumstances.
- The court sustained EPA’s authority to structure remedy selection as a multi-factor assessment that includes cost and long-term effectiveness/permanence.
- The court upheld EPA’s use of the 10⁻⁴ to 10⁻⁶ carcinogenic risk range and declined to impose 10⁻⁶ as a judicially required standard.

## Legal Principles

- When CERCLA § 121 leaves key implementation questions open, EPA may adopt reasonable interpretations through the NCP, and reviewing courts will not substitute their policy preferences for the agency’s permissible construction.
- CERCLA does not clearly require MCLGs to function as binding cleanup standards in all Superfund remedies; EPA may treat MCLs as presumptive ARARs while using MCLGs as goals or reference points.
- CERCLA’s “maximum extent practicable” language permits EPA to balance permanence and treatment preferences against cost, implementability, and related remedy-selection considerations.
- Because CERCLA does not specify a numerical carcinogenic risk level, EPA may employ a policy risk range (10⁻⁴ to 10⁻⁶) so long as the agency reasonably explains how selected remedies remain protective.

## Conclusion

The D.C. Circuit upheld EPA’s principal CERCLA NCP framework for Superfund remedies, including reliance on MCLs rather than mandatory attainment of MCLGs, use of a 10⁻⁴–10⁻⁶ cancer-risk range, and a remedy-selection approach that weighs protectiveness, permanence, feasibility, and cost within the bounds of CERCLA § 121.


Ohio v. Envtl. Prot. Agency, 997 F.2d 1520 (D.C. Cir. 1993)