## Facts

- The Clean Air Act (CAA) sets a national goal of remedying man-made visibility impairment in mandatory Class I federal areas (e.g., national parks and wilderness areas).
- EPA issued the 2005 Regional Haze Rule, including implementing regulations for state plans and guidance for determining and applying Best Available Retrofit Technology (BART) to certain large stationary sources.
- BART-eligible sources generally included large sources built between August 7, 1962 and August 7, 1977 and within listed source categories, if they may reasonably be anticipated to cause or contribute to visibility impairment in a Class I area.
- EPA’s framework allowed states to determine BART applicability using regional-scale modeling and contribution thresholds rather than requiring source-specific proof of causation for each Class I area.
- The rule also permitted states to use alternative measures (including trading-style programs) in lieu of source-specific BART if the alternative would achieve greater reasonable progress toward visibility improvement than BART.
- Industry petitioners challenged the rule as overinclusive and beyond EPA’s statutory authority; environmental petitioners challenged the rule as too permissive and inconsistent with the CAA’s visibility mandates.

## Issues

1. Whether EPA reasonably interpreted the CAA to allow regional or collective attribution methods to identify sources that “cause or contribute” to visibility impairment for BART purposes.
2. Whether EPA may allow state plan alternatives to source-specific BART when the alternative achieves greater reasonable progress toward visibility improvement.
3. Whether EPA’s choices on modeling, thresholds, and implementation discretion were arbitrary or capricious under administrative law principles.
4. Whether the CAA requires visibility improvement guarantees at each Class I area, rather than allowing overall regional progress.

## Decision

- The court denied the petitions for review and largely upheld EPA’s Regional Haze Rule and BART framework.
- Applying Chevron deference, the court held that key statutory terms (including “cause or contribute” and “reasonable progress”) left room for EPA’s policy and technical judgments.
- The court upheld EPA’s allowance of regional-scale methods to determine contribution and BART applicability in the regional haze context.
- The court upheld EPA’s authorization of state alternatives to BART where the alternative demonstrates greater reasonable progress than source-specific BART.
- The court rejected the argument that the CAA unambiguously requires visibility improvements at each individual Class I area as a prerequisite to approval of EPA’s overall approach.

## Legal Principles

- When statutory terms governing complex pollution programs are ambiguous, EPA may choose reasonable implementation approaches within the statute’s bounds, and courts will defer under Chevron.
- For regional haze, EPA may rely on scientifically supported regional modeling and reasonable contribution thresholds rather than demanding individualized proof of causation for each regulated source and each Class I area.
- The CAA’s visibility provisions permit performance-based substitutes for source-specific retrofit requirements when the substitute achieves greater reasonable progress toward the statutory visibility goal.
- Arbitrary-and-capricious review does not allow courts to replace EPA’s technical judgments with their own where the agency explains its choices and ties them to the record and statutory objectives.

## Conclusion

The D.C. Circuit sustained EPA’s central design for the Regional Haze Rule, holding that EPA reasonably interpreted the CAA to permit regional attribution methods for BART applicability and to allow state plan alternatives to BART when they produce greater reasonable progress toward improved visibility in Class I areas.


Utility Air Regulatory Group v. EPA, 471 F.3d 1333 (D.C. Cir. 2006)