## Facts

- Mississippi’s water-quality authority adopted dissolved-oxygen criteria as part of the state’s water quality standards under the Federal Water Pollution Control Act (FWPCA).
- Water quality standards include (1) designated uses for a water body and (2) criteria (often numeric limits) needed to protect those uses.
- Dissolved oxygen levels affect the ability of fish and aquatic life to survive, making the criteria central to protecting designated uses.
- The EPA disapproved Mississippi’s dissolved-oxygen criteria as insufficient to protect designated uses and inconsistent with federal requirements and policy.
- After disapproval, EPA promulgated a federal dissolved-oxygen standard applicable to Mississippi.
- Mississippi challenged EPA’s actions as beyond statutory authority, arbitrary and capricious, and improperly dismissive of economic impacts; it also raised delay and procedural objections.

## Issues

1. Whether the FWPCA authorizes EPA to disapprove a state water quality standard and promulgate a federal replacement when the state standard fails to meet statutory requirements.
2. Whether EPA’s disapproval and federal promulgation were arbitrary, capricious, or otherwise not in accordance with law under the Administrative Procedure Act.
3. Whether delay or alleged procedural defects required invalidation of the federal standard.

## Decision

- The Fifth Circuit affirmed summary judgment for EPA.
- EPA acted within its statutory authority in disapproving Mississippi’s dissolved-oxygen criteria and promulgating a federal replacement standard.
- EPA’s actions were not arbitrary or capricious because the agency provided a rational explanation supported by the administrative record and scientific evidence.
- EPA was not required to subordinate protection of designated uses to the state’s economic objections at the standards-review stage.
- Delay and procedural objections did not warrant relief because Mississippi failed to show prejudice and the procedural requirements were sufficiently satisfied.

## Legal Principles

- Under the FWPCA, states have primary responsibility to propose water quality standards, but EPA must review those standards for compliance with statutory requirements.
- If EPA determines a state standard does not meet the Act’s requirements or fails to protect designated uses, EPA may disapprove the state standard and promulgate a federal replacement.
- Courts defer to EPA’s technical and scientific judgments in water-quality criteria so long as the agency explains its decision and connects the record evidence to the chosen standard.
- Agency action will be upheld under arbitrary-and-capricious review when the agency articulates a rational basis grounded in the record; disagreement with the level of stringency is insufficient.
- Alleged timing or procedural defects do not invalidate a standard absent a showing of material noncompliance and prejudice.

## Conclusion

The Fifth Circuit upheld EPA’s authority to replace a state dissolved-oxygen criterion with a federal standard when EPA reasonably finds the state criteria insufficient to protect designated uses under the FWPCA, and it sustained EPA’s action as adequately explained, scientifically supported, and procedurally valid.


Mississippi Comm'n on Nat. Res. v. Costle, 625 F.2d 1269 (5th Cir. 1980)