On January 25, 2018, The EPA published a guidance memorandum withdrawing the “once in always in” policy for the classification of major sources of hazardous air pollutants under section 112 of the Clean Air Act. This new EPA guidance allows stationary sources of hazardous air pollutants (HAPs) that are classified as “major sources” to limit their HAP emissions to below major source thresholds and thereby be reclassified as “area” sources at any time. As Bill Wehrum, assistant administrator of EPA’s Office of Air and Radiation, puts it, “It will reduce regulatory burden for industries and the states, while continuing to ensure stringent and effective controls on hazardous air pollutants.” I agree.
A major source is one that emits or has the potential to emit 10 tons per year of any single HAP or 25 tons per year of combination of HAPs. For the last 20 years, once a source became subject to a MACT it remained in that status even if it reduced emissions below the major source threshold(s).
The new policy follows a similar theme emerging from the Pruitt EPA: legally speaking, the once in always in policy was not supported by the language of the Clean Air Act. Under this new policy, a source can voluntarily accept limitations (even after previously triggering major source status) and avoid major source requirements. This would eliminate some of the resource intensive burdens of MACT such as recordkeeping and reporting requirements.
In 2007, the Bush EPA proposed a rule that would have replaced the historic policy. After taking comment on the proposal, the EPA never took a final action and it has never been withdrawn. Based upon the new guidance, EPA intends to revive the pending rulemaking consistent with the Wehrum guidance document.
This new policy is a significant incentive for major sources to take efforts to reduce emissions on an actual or potential basis and fall below the triggering thresholds. As such, this new policy is good for business and the environment.