EPA Finalizes Regulations Ending "Once-In-Always-In" Policy

On October 1, 2020, the United States Environmental Protection Agency (EPA) issued a final rule under Section 112(a) of the Clean Air Act, ending EPA's "once-in-always-in" policy governing emissions of hazardous air pollutants (HAPs). The rule allows for a major source of HAPs to be reclassified as an area source in some circumstances. A major source is a source that emits or has the potential to emit at least 10 tons per year of a single HAP or at least 25 tons per year of a combination of HAPs, while an area source is any stationary source of HAPs that does not meet either of these thresholds. Major sources are required to use the Maximum Achievable Control Technology (MACT) to reduce HAP emissions. Area sources are meanwhile generally subject to a less stringent "Generally Available Control Technology" standard.