In late January, EPA issued a guidance memorandum rescinding the agency’s prior policy that once a source becomes a major source subject to a maximum achievable control technology (MACT) standard under section 112 of the Clean Air Act (CAA), it cannot be reclassified later as an area source not subject to MACT. The prior policy, known as the “once in always in” policy, dates from guidance issued in 1995. Under the new policy, a major source can become an area source if it takes an enforceable limit on its potential to emit (PTE) hazardous air pollutants (HAP) below the major source thresholds (i.e., 10 tons per year (tpy) of any single HAP or 25 tpy of any combination of HAP). A source that was previously classified as major, but which so limits its PTE, will no longer be subject either to the major source MACT or other major source requirements that were applicable to it as a major source under CAA section 112.
The legal basis for this action is that the “once in always in” policy contradicts the plain language of the definitions of “major source” in CAA section 112(a)(l) and “area source” in CAA section 112(a)(2). EPA has twice proposed to rescind the policy since it was adopted in 1995, but neither proposal was finalized. The new guidance rescinding the prior policy is effective immediately. EPA also will take comment on a rulemaking proposal to codify the new policy, to be published at a later date. Several opposition groups have announced their intention to file lawsuits seeking to overturn the new policy.