Arkansas v. Oklahoma

Background

A new sewage treatment plant in Fayetteville, Arkansas sought a federal discharge permit after Arkansas lacked an approved state permit program. The EPA issued a permit authorizing part of the plant’s effluent to flow into local creeks and eventually the Illinois River, which reaches Oklahoma. Oklahoma objected, citing its rule that forbids degradation of certain “scenic” waters. The permit was reviewed by an Administrative Law Judge and the EPA’s Chief Judicial Officer, who found the discharge would not cause any detectable violation of Oklahoma’s standards.

Reasoning

The central question was whether the EPA properly protected the downstream State by insisting there be no detectable harm. The Court declined to decide whether the statute always requires applying downstream standards, but held the EPA had authority to condition permits to ensure compliance. The Court found the Agency’s regulation and its interpretation reasonable, concluded the factual findings (on eutrophication, esthetics, dissolved oxygen, and metals) were supported by substantial evidence, and determined the Court of Appeals had erred by imposing a novel categorical ban and by substituting its own factual and legal judgments for the Agency’s.

Real world impact

The ruling lets the EPA condition federal NPDES permits to prevent detectable harm to downstream State water-quality standards and rejects a blanket prohibition on new discharges into already degraded waters. The decision reversed the Court of Appeals and reinstated the Fayetteville permit, while leaving open the separate question of whether the statute itself always requires downstream-standard application.