Sierra Club v. EPA

The Environmental Protection Agency acts arbitrarily and capriciously when approving a State Implementation Plan for National Ambient Air Quality Standards, based on data that is significantly different than more current data.

The Clean Air Act (CAA) allows the state and federal governments to partner in combating air pollution. The San Joaquin Valley has been designated as an extreme nonattainment area for the pollutant ozone. The CAA allows states to develop State Implementation Plans to address nonattainment areas and come into compliance with the National Ambient Air Quality Standard (NAAQS). The SIPs are subject to United States Environmental Protection Agency approval. In 1991, the San Joaquin Valley was classified as a nonattainment zone. The state missed deadlines in meeting the EPA's requirements for submitting a SIP and voluntarily classified the area as "extreme" to extend the deadline. The 2004 SIP was submitted with the 2006 and 2008 amendments. The EPA approved the 2004 SIP for the San Joaquin Valley's nonattainment area for the one-hour ozone NAAQS. The Sierra Club and several environmental groups petitioned the Court for review of this decision contending the EPA acted arbitrarily and capriciously. The Sierra Club alleges the EPA approved the 2004 SIP knowing that the emissions data the plan relied on, was actually outdated and inaccurate by 2010, when the EPA approved the plan. The 2007 measurement revealed a significantly different measurement of NOx. This should have alerted the EPA to potential flaws in the 2004 SIP. During the EPA's final rule the EPA did not address the apparent differences in the 2004 and 2007 measurements, thus not adequately addressing the outdated data and viewing current data before reaching its conclusion. The Court held the EPA acted arbitrarily and capriciously in approving the 2004 SIP. PETITION GRANTED.