## Facts

- The City of Albuquerque operated a publicly owned wastewater treatment facility discharging treated effluent into the Rio Grande.
- The Rio Grande flows downstream through the Pueblo of Isleta reservation.
- Under the Clean Water Act (CWA), EPA may treat eligible Indian tribes as states for purposes of adopting water quality standards.
- EPA granted the Pueblo of Isleta “treatment-as-a-state” status, and the Pueblo adopted water quality standards for the Rio Grande that were more stringent than New Mexico’s standards in certain respects (including numeric criteria for pollutants such as arsenic).
- After notice-and-comment, EPA approved the Pueblo’s standards and initiated revision of Albuquerque’s NPDES permit to ensure Albuquerque’s discharge would not cause violations of the downstream tribal standards.
- Albuquerque sued, contending EPA lacked authority to approve and apply the tribal standards to an upstream, off-reservation discharger; that EPA acted arbitrarily and capriciously; and that certain standards were unconstitutional (Establishment Clause and vagueness) or technically unattainable.
- The district court granted summary judgment for EPA, and Albuquerque appealed.

## Issues

1. Whether the CWA authorizes EPA to approve tribal water quality standards under treatment-as-a-state provisions, including standards more stringent than federal minimum criteria or neighboring state standards.
2. Whether EPA may use downstream tribal water quality standards to set effluent limits in an NPDES permit for an upstream, off-reservation discharger.
3. Whether EPA’s approval of the tribal standards was arbitrary, capricious, or otherwise unlawful under the Administrative Procedure Act.
4. Whether EPA’s approval and application of the standards violated the Establishment Clause or were void for vagueness.

## Decision

- The court affirmed summary judgment for EPA.
- The CWA authorized EPA to treat tribes as states and to approve tribal water quality standards, including more stringent standards.
- EPA could apply approved downstream tribal standards when determining upstream NPDES permit limitations to protect downstream waters.
- EPA’s approval was not arbitrary or capricious because the agency considered the record, followed notice-and-comment procedures, and provided a rational explanation for its approval.
- The Establishment Clause challenge failed because EPA’s approval served a secular regulatory purpose and did not constitute religious endorsement or enforcement.
- The vagueness challenge failed because numeric limits provide clear notice, and narrative standards were sufficiently definite within the CWA regulatory framework.

## Legal Principles

- Under CWA § 518, EPA may treat qualifying tribes as states for water quality standards programs and approve tribal standards meeting statutory and regulatory criteria.
- Approved water quality standards function as the target for effluent limitations in NPDES permits and may be applied to upstream dischargers whose effluent affects downstream waters subject to those standards.
- Under APA review, EPA action is upheld when the agency considers relevant factors, supports its decision with record-based reasoning, and follows required procedures.
- Environmental standards do not violate the Establishment Clause merely because a sovereign’s cultural or religious values inform its preferred level of water protection; federal approval is evaluated by the secular purpose and effect of the regulatory action.
- Standards are not unconstitutionally vague when they provide regulated entities reasonable notice of required conduct; difficulty or cost of compliance does not itself establish vagueness or illegality.

## Conclusion

The court upheld EPA’s approval of the Pueblo of Isleta’s water quality standards and EPA’s use of those standards to drive effluent limits in Albuquerque’s upstream NPDES permit, rejecting statutory, APA, and constitutional challenges.


City of Albuquerque v. Browner, 97 F.3d 415 (10th Cir. 1996)