## Facts

- Federal land managers approved the Mt. Hope Project, a large, long-term molybdenum mine in central Nevada involving an open pit and related facilities on public lands.
- The agency prepared an Environmental Impact Statement (EIS) and issued a Record of Decision (ROD) approving the project.
- The EIS addressed baseline air quality and predicted emissions, cumulative air-quality effects from regional activities, potential post-closure pit-lake effects on groundwater, and mitigation and reclamation measures.
- Environmental and tribal-advocacy organizations sued, alleging the EIS violated the National Environmental Policy Act (NEPA), that approval conflicted with the Federal Land Policy and Management Act (FLPMA), and that the agency failed to protect springs potentially subject to Public Water Reserve No. 107 (PWR 107).
- The district court largely upheld the approvals and entered judgment for the agency and the project proponent.
- Plaintiffs appealed.

## Issues

1. Whether the EIS used a reasonable and accurate baseline for certain air pollutants as required by NEPA’s “hard look.”
2. Whether the EIS adequately analyzed cumulative air-quality impacts from the project combined with other past, present, and reasonably foreseeable actions.
3. Whether the agency took a sufficient “hard look” at post-closure pit-lake water quality and related groundwater impacts.
4. Whether the EIS’s discussion of long-term mitigation and reclamation was sufficiently complete under NEPA.
5. Whether alleged failures to protect PWR 107 springs and related FLPMA duties should be resolved before the agency corrects NEPA errors.

## Decision

- The court affirmed in part, reversed in part, and vacated in part the district court’s judgment.
- It held the agency’s selection of baseline levels for certain air pollutants was unreasonable and violated NEPA.
- It held the cumulative air-quality impacts analysis was deficient under NEPA.
- It held the agency took the required hard look at pit-lake water quality and potential groundwater impacts.
- It held the mitigation and reclamation discussion was “reasonably complete” and sufficient under NEPA.
- It declined to reach the PWR 107/withdrawn-waters claim at that stage and remanded for the agency to correct the NEPA errors first.
- It directed the district court to vacate the ROD and remand to the agency.

## Legal Principles

- NEPA requires an agency to establish a reasonable, accurate environmental baseline to permit informed evaluation of a proposed action’s impacts; an unreasonable baseline can render an EIS arbitrary and capricious under APA review.
- NEPA cumulative-impact review must evaluate the incremental effect of the proposed action when added to other past, present, and reasonably foreseeable actions; generalized or cursory discussion may be inadequate where a concrete assessment is feasible.
- Courts defer to technical judgments where the agency meaningfully addresses the relevant scientific issues and explains its methodology, satisfying the “hard look” standard.
- NEPA requires discussion of mitigation measures, but the discussion is adequate if it is reasonably complete and informs decisionmakers and the public without requiring fully engineered, final mitigation plans at the EIS stage.
- When NEPA defects are intertwined with other statutory or withdrawn-land questions, a court may remand for NEPA compliance first and postpone merits resolution of related substantive challenges.

## Conclusion

The Ninth Circuit required the agency to redo core parts of its air-quality analysis under NEPA, vacated the project approval, and remanded for further agency proceedings while leaving pit-lake, mitigation, and withdrawn-water issues largely unresolved pending corrected environmental review.


Great Basin Res. Watch v. Bureau of Land Mgmt., 844 F.3d 1095 (9th Cir. 2016)