## Facts

- Between June and September 1986, Chevron accidentally discharged small quantities of oil into navigable waters on twelve occasions.
- Each discharge was sufficient to produce an iridescent film or sheen on the water’s surface.
- Section 311 of the Clean Water Act prohibits discharges of oil into navigable waters in quantities that “may be harmful,” and authorizes EPA to define such quantities by regulation.
- EPA regulations (40 C.F.R. pt. 110) treat discharges that cause a film, sheen, or discoloration as discharges that “may be harmful.”
- The Coast Guard investigated each incident and assessed civil penalties, generally several hundred dollars to about $1,000 per discharge.
- In administrative proceedings, Chevron offered expert testimony that the spills were minimal and caused no actual environmental injury, but the Coast Guard upheld the penalties under the sheen standard.
- Chevron sued in federal district court, which granted summary judgment for Chevron on the theory that lack of actual harm (or a minimal-discharge exception) barred penalties.
- The Coast Guard officials and the United States appealed.

## Issues

1. Whether Clean Water Act § 311 and EPA’s sheen regulation require proof of actual environmental harm before civil penalties may be imposed for oil discharges that create a sheen.
2. Whether a de minimis defense exists for sheen-producing oil discharges covered by EPA’s regulation.
3. Whether the Coast Guard permissibly applied EPA’s sheen regulation to impose civil penalties for Chevron’s twelve accidental discharges.

## Decision

- The Fifth Circuit reversed the district court’s summary judgment for Chevron.
- The court held that EPA’s sheen regulation is authorized by § 311(b)(3)–(4) and validly defines discharges that “may be harmful.”
- The court held that proof of actual environmental injury is not required when a discharge meets the regulatory sheen standard.
- The court rejected a de minimis defense for discharges that create a sheen.
- The court upheld the Coast Guard’s authority to assess civil penalties for each sheen-producing discharge.

## Legal Principles

- Under Clean Water Act § 311, Congress prohibited oil discharges in quantities that “may be harmful” and delegated to EPA authority to define, by regulation, what quantities meet that standard.
- EPA’s 40 C.F.R. pt. 110 sheen test is a lawful regulatory determination that a sheen-producing discharge “may be harmful.”
- When a discharge satisfies EPA’s regulatory definition (e.g., causes a sheen), liability and civil penalties do not depend on case-specific proof of actual environmental damage.
- Courts will not create a de minimis exemption that conflicts with the statutory scheme and EPA’s regulatory classification for sheen-producing discharges.
- In enforcement, regulated parties generally may not negate liability by relitigating harm where the controlling regulation treats the discharge as potentially harmful.

## Conclusion

The Fifth Circuit held that an oil discharge that creates a visible sheen on navigable waters violates Clean Water Act § 311 as implemented by EPA regulations, and that civil penalties may be imposed without proving actual harm and without a de minimis exception.


Chevron, U.S.A., Inc. v. Yost, 919 F.2d 27 (5th Cir. 1990)