## Facts

- Michael H. Weitzenhoff (manager) and Thomas W. Mariani (assistant manager) operated a municipal sewage treatment plant in Hawaiʻi subject to an NPDES permit limiting pollutant discharges and requiring monitoring and sampling.
- The plant generated waste-activated sludge (WAS) that was supposed to be stored and removed; instead, defendants arranged for WAS to be discharged into the ocean on roughly 40 occasions between April 1988 and June 1989.
- The WAS discharges were routed to bypass monitoring equipment, resulting in inaccurate or misleading compliance data and reports to regulators.
- Evidence showed defendants directed employees to conduct discharges at night, failed to record them, and did not report the discharges to state or federal agencies.
- Defendants maintained they believed their actions were permitted under their understanding of the NPDES permit.
- A federal jury convicted defendants of multiple counts, including felony violations of the Clean Water Act for “knowingly” violating permit conditions; Weitzenhoff received 21 months’ imprisonment and Mariani 33 months.

## Issues

1. Whether “knowingly” in Clean Water Act § 309(c)(2) requires proof that defendants knew their conduct violated the NPDES permit (or the law), or only that they knowingly engaged in the conduct that in fact caused the permit violation.
2. Whether interpretation of disputed NPDES permit terms is a question of law for the court, making it erroneous to admit expert testimony offering legal interpretations for the jury.
3. Whether any instructional, evidentiary, or sentencing errors required reversal.

## Decision

- The Ninth Circuit affirmed the convictions and the sentence challenges at issue.
- The court held that § 309(c)(2) does not require proof that defendants knew they were violating the permit or the Clean Water Act; it is enough that they knowingly engaged in the acts that resulted in a permit violation.
- The court treated Clean Water Act felony violations as public welfare offenses, placing compliance risk on permittees who control regulated discharges and are positioned to know their permit obligations.
- The court distinguished authority requiring greater knowledge in other regulatory settings, emphasizing defendants’ role as permit-holding operators rather than peripheral actors.
- The court ruled that allowing expert testimony on contested questions of permit meaning was error because permit interpretation is for the judge, but found the error harmless because the discharges violated the permit under the correct legal interpretation.
- The court rejected remaining challenges to instructions, proof, evidentiary rulings, and sentencing.

## Legal Principles

- Under 33 U.S.C. § 1319(c)(2), the government need not prove that a defendant knew the specific permit condition or knew the conduct was unlawful; it must prove the defendant knowingly engaged in the conduct and that the conduct violated the permit.
- Clean Water Act criminal enforcement may operate as a public welfare offense regime, permitting felony liability without proof of knowledge of legal requirements where regulated actors handle dangerous pollutants and control compliance.
- NPDES permit interpretation is a question of law for the court; presenting competing expert views of what permit terms legally require is improper when it substitutes for judicial instruction on the governing legal meaning.
- Erroneous admission of legal-interpretation expert testimony may be harmless where the permit, properly construed, clearly prohibits the charged discharges and the verdict is not affected.

## Conclusion

The Ninth Circuit upheld felony Clean Water Act convictions for intentional sewage-sludge discharges, holding that “knowingly” requires awareness of the discharging conduct—not knowledge that the conduct violated an NPDES permit—and reaffirmed that NPDES permit meaning is determined by the court as a matter of law.


United States v. Weitzenhoff, 35 F.3d 1275 (9th Cir. 1994)