USEPA Attempts To End “Once In Always In” Policy

In late January 2018, the USEPA issued an internal memorandum and in early February USEPA Administrator Scott Pruitt testified to Congress of his desire to rescind its “Once In Always In” (OIAI) policy for major sources under the federal National Emission Standards for Hazardous Air Pollutants (NESHAP) program. Under OIAI, major sources subject to Maximum Achievable Control Technology (MACT) standards are prohibited from reclassification that would excuse them from these standards even if the facility reduced air toxic emissions sufficiently to become a minor source. The memo reverses this position. This action is being done to reward major emission sources who have invested resources to significantly reduce hazardous air pollutant emissions to fall below the major source threshold. The USEPA plans to amend NESHAP text to codify this new policy beginning with a Federal Register posting. Legal challenges are expected.


The federal NESHAP program provides emission limits based on “maximum achievable control technology”, defined in the rule as fairly stringent requirements. MACT apples to sources that emit any of 187 listed hazardous air pollutants (“HAPs”) in over 100 source categories. NESHAP covers two categories of sources: “major” and “area” sources. Major sources have the potential to emit at least 10 tons per year (tpy) of any listed HAP or 25 tpy of all HAPs. Any source that is not “major” is treated as an “area” source. Most MACT standards only apply to major sources; area sources are exempt. However, MACT standards for some source categories apply to both major and areas sources.

Given this, it is possible for a facility to accept federally-enforceable emission limits to become an area source (“synthetic minor”) to get out of installing expensive MACT-compliant technology (and avoid significant recordkeeping and reporting requirements). This can be achieved potentially with air pollution control strategies that are less stringent than MACT or by reducing hours of operation. Given the sensitivity of HAP emissions which could result in adverse public health effects on those near a plant, the USEPA in the early 1990’s established a policy that a facility can become a synthetic minor, but only by doing so before a MACT standard became effective. One cannot avoid the standard after the MACT standard went into effect, leading to the OIAI policy.

USEPA Justification

The USEPA justified the new policy on the grounds that Congress in the Clean Air Act provided no language pertaining to the reclassification of major sources to area ones. Their new guidance memo wishes to inject “plain language” that a facility would switch from a major source of HAPs to an area source when an enforceable limit on potential to emit HAPs below the “10/25” thresholds is achieved and approved.

Intended Outcomes

The USEPA believes its new policy ending OIAI will have several outcomes. It would:

• result in “meaningful incentives” for facilities to undertake projects that will reduce HAP emissions below major source thresholds.

• eliminate a “punishment” for facilities whose HAP emissions have dropped not because of conscious emission reductions, but because of changes in processes or business shifts for remaining “major”. For example, facilities who have permanently substituted less toxic compounds for HAPs for any of a variety of reasons (cost, availability, worker safety concerns) and is no longer major would no longer be required to comply with MACT and robust recordkeeping and reporting requirements. Also, this would apply to whose business has changed and no longer produce products or produce less product that require use of HAP compounds. They would no longer be burdened given this policy change.

• remove the burden for facilities whose potential to emit (based on unrestricted operation) is above the major source threshold, but whose actual emissions are significantly below it. Facilities who were unsure how to limit their operation to have federally-enforceable limits were careful and went into a given MACT program. But for those whose subsequent operation confirmed that actual HAP emissions were truly well below the major threshold, it was too late for relief.

A Compromise Solution?

While this is an article of facts and background, I do wish to provide a compromise position that I think would achieve the goals of both sides of this debate. New York State has a policy that any facility wishing to permit itself just below any applicable threshold (even for non-HAP compounds) must be limited to 10% below the threshold to account for any unexpected or accidental release (the facility would likely still be below the threshold. Applied to this situation, if a facility can commit and abide by permit limits of 9 tpy for any HAP and 22.5 tpy of all HAPs, and maintain this for a set time, say, 2 years, then it can be changed to an area source and all MACT requirements removed.

What Facilities Should Do

While there are likely to be legal battles concerning the elimination of OIAI, facilities who are regulated as major HAP sources should review their current emission inventories to see if they have fallen below the major source thresholds or are close enough to make the reduction to below the threshold technically and economically feasible. It may be to the facility’s advantage to catalog that its actual emissions are below the major threshold or implement the changes that will ensure this. To codify this, one would need to modify one’s Title V Air Permit to remove that MACT standard as an applicable rule and in so doing, remove or lessen control, recordkeeping, and reporting requirements. Some states, which may be resistant to this change, may not implement any such changes until all court proceedings are completed. Also, some have “anti-backsliding” provisions that may prevent the loosening of existing restrictions. Such facilities should retain the proper technical and legal experts as they are proceeding.

Please note that this is a technical, not a legal, assessment of the change in federal OIAI policy. Speak to appropriate legal counsel before making any decisions on this or related matters. CCES has the technical experts to help you assess whether your current emissions exceed or are below any major applicability threshold and can provide advice on the most cost-effective ways to reduce HAP (and non-HAP) emissions for a variety of processes. Contact us today at 914-584-6720 or at