Arkansas v. Oklahoma, 503 U.S. 91 (1992) (U.S. Supreme Court)
Arkansas v. Oklahoma is a cornerstone Clean Water Act (CWA) and administrative law case that clarifies the Environmental Protection Agency's (EPA) power to manage interstate water pollution through the National Pollutant Discharge Elimination System (NPDES).
Does the Clean Water Act authorize EPA to condition or deny an upstream NPDES permit based on a downstream State's water quality standards, and did EPA reasonably issue Fayetteville's permit upon finding no measurable violation of Oklahoma's standards at the state line?
Under the Clean Water Act, EPA may object to or condition an NPDES permit to ensure compliance with any applicable water quality requirements, including those of a downstream State whose standards have been approved under 33 U.S.C. § 1313. See 33 U.S.C. § 1342(d)(2), § 1311(b)(1)(C), § 1313. Approved State water quality standards become federal law for permitting purposes, and EPA's reasonable interpretation of the CWA and its own regulations (including antidegradation requirements, see 40 C.F.R. § 131.12) is entitled to deference. The Act does not impose a per se ban on new or expanded discharges into waters that are not meeting standards; rather, EPA may authorize a discharge if the permit ensures the discharge will not cause or contribute to a violation of applicable water quality standards, based on the administrative record.
Yes. The Clean Water Act permits EPA to condition or deny an upstream NPDES permit based on a downstream State's water quality standards, and EPA reasonably issued the Fayetteville permit upon concluding—on substantial evidence—that the discharge would not cause a measurable violation of Oklahoma's standards at the state line. The Tenth Circuit's contrary ruling was reversed and the case remanded.
Arkansas v. Oklahoma is a leading case on interstate water pollution, cooperative federalism, and administrative deference. It confirms that downstream State water quality standards meaningfully constrain upstream permits and that EPA may enforce those standards across state lines. For administrative law, it exemplifies Chevron deference to EPA's statutory and regulatory interpretations and judicial deference to EPA's technical findings in complex environmental decision-making. Practically, the case shapes NPDES permitting by requiring agencies and permittees to model interstate effects, incorporate downstream standards, and build a robust record to support 'no cause or contribute' determinations.