## Facts

- Carroll County, Maryland operated the Hampstead Wastewater Treatment Plant, which discharged treated effluent into Piney Run, a state-classified trout-supporting stream.
- The Plant discharged under a state-issued NPDES permit under the Clean Water Act (CWA).
- The permit set effluent limits for certain pollutants and required monitoring and reporting, but did not include a numeric thermal limit or expressly list “heat” as a permitted or prohibited pollutant.
- An environmental association filed a CWA citizen suit alleging the County unlawfully discharged “heat” (heated effluent) because the permit did not expressly authorize that pollutant.
- The County asserted it complied with the permit’s express limits and reporting duties and that any thermal discharge was within what the state permitting authority reasonably anticipated when issuing the permit.

## Issues

1. Whether the CWA’s NPDES “permit shield” bars liability when a permittee complies with the permit’s express discharge limits and reporting requirements, and the alleged unlisted pollutant discharge was within the reasonable contemplation of the permitting authority at issuance.
2. Whether the district court could impose CWA liability for a pollutant not expressly limited or listed in the permit despite permit compliance.

## Decision

- The Fourth Circuit vacated the district court’s judgment and remanded.
- The court held the County did not violate the CWA because it complied with the permit’s discharge limitations and reporting requirements and the thermal discharge was within the reasonable contemplation of the permitting authority when the permit issued.
- The court set aside the district court’s injunction and civil penalties predicated on the alleged unauthorized discharge of heat.

## Legal Principles

- Under 33 U.S.C. § 1342(k), compliance with an NPDES permit is deemed compliance with specified substantive CWA provisions (the “permit shield”).
- The permit shield protects a permittee from CWA liability for discharges not expressly listed or numerically limited in the permit when:
  - the permittee complies with the permit’s express effluent limits and monitoring/reporting requirements; and
  - the discharges were within the reasonable contemplation of the permitting authority at the time of permit issuance.
- The permit shield does not protect discharges outside the permitting authority’s reasonable contemplation, or situations involving noncompliance with permit terms or failure to disclose material information necessary for informed permitting.

## Conclusion

The Fourth Circuit held that a permittee that complies with its NPDES permit’s express limitations and reporting obligations is shielded from CWA liability for discharging an unlisted pollutant, so long as the discharge was reasonably contemplated by the permitting authority when the permit was issued.


Piney Run Pres. Ass’n v. Cnty. Comm’rs of Carroll Cnty., 268 F.3d 255 (4th Cir. 2001)