## Facts

- Chesapeake Bay suffered severe nutrient and sediment pollution impairing aquatic life.
- Under Clean Water Act (CWA) § 303(d), EPA issued a 2010 Chesapeake Bay total maximum daily load (TMDL) for nitrogen, phosphorus, and sediment.
- The TMDL set overall pollutant caps and included detailed allocations among sources, including wasteload allocations for point sources and load allocations for nonpoint sources.
- EPA also included more granular sector and source allocations, a timetable, and “reasonable assurance” components intended to ensure implementation by states.
- A coalition of agricultural, poultry, fertilizer, and homebuilding organizations challenged the TMDL, seeking to vacate it as beyond EPA’s statutory authority.
- The district court granted summary judgment to EPA, upholding the TMDL as consistent with the CWA.
- The challengers appealed to the Third Circuit.

## Issues

1. Whether the CWA term “total maximum daily load” authorizes EPA to issue a TMDL containing detailed source allocations, target dates, and implementation assurances, or limits EPA to setting only an aggregate numeric cap.
2. Whether EPA’s Bay-wide TMDL unlawfully intruded on state authority within the CWA’s cooperative-federalism framework.
3. Whether, under Chevron, EPA’s interpretation of “TMDL” was a permissible construction of an ambiguous statutory term.

## Decision

- The Third Circuit affirmed the district court’s judgment for EPA.
- The court held EPA acted within its statutory authority in promulgating the Chesapeake Bay TMDL.
- The court upheld EPA’s inclusion of detailed allocations, timetables, and reasonable-assurance measures as a reasonable policy choice under the CWA.
- The court rejected the argument that “total” restricts a TMDL to a single undifferentiated number.
- Applying Chevron deference, the court concluded the statute left “TMDL” undefined and EPA’s construction was reasonable.

## Legal Principles

- When a statutory term is undefined and ambiguous, courts may defer to an agency’s reasonable interpretation under Chevron.
- A TMDL under CWA § 303(d) may be treated as more than an aggregate cap and may include allocations among categories of sources (including point and nonpoint sources) to meet water-quality standards.
- The CWA’s cooperative-federalism structure permits EPA oversight and coordination for interstate waters while leaving primary implementation responsibilities to states, so long as EPA does not assume regulatory powers the statute withholds.
- EPA may structure a TMDL with implementation-oriented elements (such as schedules and reasonable-assurance mechanisms) where the agency reasonably determines they are connected to achieving the pollutant limits needed to attain standards.

## Conclusion

The Third Circuit sustained EPA’s Chesapeake Bay TMDL as a lawful exercise of CWA § 303(d) authority, deferring to EPA’s reasonable interpretation that a TMDL may include detailed allocations and implementation measures to ensure attainment of water-quality standards in a multi-state watershed.


Am. Farm Bureau Fed’n v. U.S. Env’t Prot. Agency, 792 F.3d 281 (3d Cir. 2015)