## Facts

- Montana revised portions of its Clean Water Act § 303(c) water quality standards, including an exemption for nonpoint sources from antidegradation review and policies permitting “mixing zones” for certain point source discharges.
- The Clean Water Act generally regulates point source discharges through the NPDES permitting program; nonpoint source pollution is addressed primarily through state programs and planning mechanisms.
- Montana submitted its revised standards to the Environmental Protection Agency for review, and EPA approved the revisions.
- American Wildlands, an environmental organization, challenged EPA’s approval in federal district court, alleging (1) untimely EPA action and (2) unlawful approval of standards inconsistent with the Clean Water Act.
- The district court upheld EPA’s actions and entered judgment for EPA.
- American Wildlands appealed to the Tenth Circuit.

## Issues

1. Whether EPA acted arbitrarily, capriciously, or contrary to law in approving Montana’s exemption of nonpoint source pollution from antidegradation review.
2. Whether EPA acted arbitrarily, capriciously, or contrary to law in approving Montana’s mixing zone policies and procedures.

## Decision

- The Tenth Circuit affirmed the district court’s judgment for EPA.
- EPA permissibly approved Montana’s exemption of nonpoint sources from antidegradation review because the Clean Water Act does not grant EPA authority to regulate nonpoint source discharges through the federal permitting structure, and EPA’s construction of the statutory scheme was reasonable.
- EPA permissibly approved Montana’s mixing zone policies because antidegradation requirements apply to the waterbody as a whole; limited, controlled degradation within a mixing zone is allowable if water quality criteria and designated uses are protected outside the zone.
- Applying APA arbitrary-and-capricious review and Chevron deference where the statute was ambiguous, the court found EPA’s approvals rational and consistent with the Act and EPA’s implementing regulations.

## Legal Principles

- Agency approval of state water quality standards under Clean Water Act § 303(c) is reviewed under the APA’s “arbitrary and capricious” standard.
- When the Clean Water Act is ambiguous on the scope of EPA authority, courts defer to EPA’s reasonable statutory interpretation under Chevron.
- The Clean Water Act’s primary federal control mechanism is the NPDES permit program for point sources; nonpoint source pollution is chiefly addressed through state-led measures, including planning tools such as TMDLs for waters not meeting standards.
- Antidegradation policy requirements may be satisfied even where a state permits mixing zones, so long as water quality standards and designated uses are maintained for the waterbody outside the mixing zone.

## Conclusion

The Tenth Circuit upheld EPA’s approval of Montana’s revised water quality standards, concluding that EPA reasonably interpreted the Clean Water Act to allow an exemption of nonpoint sources from antidegradation review and to permit regulated mixing zones that protect water quality and uses outside the defined zones.


American Wildlands v. Browner, 260 F.3d 1192 (10th Cir. 2001)