Last Friday, the U.S. Court of Appeals for the D.C. Circuit (“D.C. Circuit”) upheld the Environmental Protection Agency’s (“EPA”) “exceptional events rule,” which allows data recorded during unusually strong storms or natural disasters to be excluded when determining whether an area violates federal air quality standards. The rule implements longstanding EPA policy that an area should not be held in violation of federal standards if the emissions were caused primarily by an atypical or unpreventable event that is unlikely to recur.

The challenge to the “exceptional events rule” was raised by the Natural Resources Defense Council (“NRDC”) – it claimed that the rule conflicted with a 2005 Clean Air Act amendment that adopted EPA’s exceptional events policy into law. Even though the amendment itself was based on an EPA policy memorandum, and even though EPA’s final rule copied the language of the amendment directly into the regulation, the NRDC claimed that EPA’s rule conflicted with the statutory language adopted by Congress. However, the Court did not reach the merits of that claim, since two of the three judges agreed that the NRDC failed to raise the issue during the comment period, and thus, could not raise it later in litigation. Even the judge that disagreed with the procedural ruling of the Court would have rejected NRDC’s claim on its merits, according to her dissenting opinion.

The decision is most relevant to agricultural and mining operations, whose earth disturbance activities make them vulnerable to high wind events. A key complaint of the NRDC was that EPA’s exceptional events rule would excuse emissions from farms or mines that occurred during unusually strong storms – the NRDC argued that all human-related emissions should “count” in determining compliance with federal standards, regardless of whether they were actually caused by an exceptional event. If the NRDC’s position had prevailed, areas with significant farming or mining operations would be at greater risk of becoming a “nonattainment area,” thus triggering more stringent restrictions for existing sources and new development projects. By rejecting the NRDC’s challenge, the D.C. Circuit upheld EPA’s policy of excluding short-term, exceptional emissions from consideration when making attainment determinations that can have long-lasting regulatory implications. Troutman Sanders represented the National Mining Association and the American Farm Bureau Federation in the case in support of EPA’s rule.