The Tenth Circuit Court of Appeals has upheld the U.S. Environmental Protection Agency’s (EPA’s) final rule requiring Utah to submit a revised State Implementation Plan (SI P) under the Clean Air Act (CAA). U.S. Magnesium, LLC v. EPA, No. 11-9533 (10th Cir. 8/6/12). EPA initially approved the Utah SI P in 1980, but stated that it might disapprove the Utah Unavoidable Breakdown Rule (UBR ) once the agency had developed its own guidance for such rules. EPA later developed and subsequently revised guidance for handling equipment malfunction under the CAA. In 1999, EPA asked Utah to conform its UBR to the agency guidance. In 2008, after EPA had disapproved a proposed revision, the state determined not to change its UBR . EPA then undertook a rulemaking to issue its SI P call to Utah.

At issue are UBR provisions that EPA asserted would cover all emissions during a breakdown when, for example, EPA’s toxic emissions rules contain their own breakdown provisions for the pollutants they cover. Moreover, EPA determined that the Utah UBR could be interpreted to completely eliminate potential penalties and to potentially prohibit injunctive relief, both of which are contrary to EPA’s current interpretation of the CAA. EPA also asserted that the Utah UBR could be interpreted to give the state agency’s executive director exclusive authority to determine whether a breakdown constituted a violation, potentially impeding EPA or citizen suit enforcement.

U.S. Magnesium appealed the SI P call, arguing in part that it was based on EPA interpretive documents that had not undergone notice-and-comment rulemaking and did not have the force of law. The Tenth Circuit held that the guidance documents did not have the force of law, they set forth EPA’s interpretation of a statute that it was charged to enforce, and the court deferred to EPA’s interpretation. U.S. Magnesium also argued that EPA had not determined that the Utah UBR had, as a matter of fact, rendered the Utah SI P “substantially inadequate” (the statutory prerequisite for a SI P call) because EPA identified no instances in which the UBR led to National Ambient Air Quality Standards violations. The court agreed with EPA that a SI P can be inadequate even if it has not, at a given time, resulted in such a violation.