USEPA’s Proposed Reversal of the Once In, Always In Policy – Does This Make Sense?

USEPA’s Proposed Reversal of the Once In, Always In Policy – Does This Make Sense?

USEPA’s Proposed Reversal of the Once In, Always In Policy – Does This Make Sense?

On January 25, 2018, the U.S. Environmental Protection Agency (USEPA) made a change in policy that could have significant ramifications for permitted sources of hazardous air pollutants (HAP).  That is when Bill Werhum, Deputy Director of the USEPA, published a guidance memo to the USEPA Regional Air Directors that reversed the long-standing Once In, Always In (OIAI) policy1.

What is OIAI and what does it mean?

So, what is the OIAI policy?  To answer this, a little history about the CAA would first be helpful.  Section 112 of the 1970 CAA established health-based emissions standards for a few hazardous (or toxic) compounds.  In following years, the United States government was pushed to do more to limit toxic compound emissions throughout the country.  As a result, the CAA was amended by Congress in 1990 with a revision to Section 112 requiring the USEPA to develop technology-based emission standards for “major sources” of HAP compounds, approximately 190 in all.  The standards are commonly referred to as maximum achievable control technology (MACT) standards that limit HAP emissions from approximately 164 different source categories.  A major source is defined as having the potential to emit 10 tons per year or more of a single HAP, or 25 tons per year or more of aggregate HAP. Any source with the potential to emit less than these thresholds are defined as “area sources.”  Compliance with an applicable major source MACT can vary depending on the standard, but will generally include variations of emission rate limits, raw material restrictions, add-on emission controls, and work practices.

Back in the mid-1990s, a major source of HAP that was facing a “new” MACT standard would typically require planning, new resources and, in many instances, significant capital expenditures to demonstrate compliance.  In fact, it was not uncommon for forward-thinking facilities to, instead, consider investing in technologies to completely avoid applicability of a rule; however, the appropriate timing for avoidance was not very clear.  Such clarity eventually came in May 1995 when USEPA published the Potential to Emit for MACT Standards – Guidance on Timing Issues2 memorandum.  For our purposes here, this memo can be boiled down to the key directive to permitting authorities stating that “..facilities that are major sources for HAPs on the “first compliance date” are required to comply permanently with the MACT standard to ensure that maximum achievable reductions in toxic emissions are achieved and maintained.” (bold emphasis added).  This guidance was termed the once in, always in policy.

What is the dilemma?

Following the implementation of the OIAI policy, any change at a facility after an applicable MACT compliance date that resulted in a reduction in their potential to emit HAP below the major source thresholds (becoming an area source) would still require them to comply with all aspects of the major source MACT standard.  Even those facilities that later, for example, added air pollution control, or incorporated HAP-reducing raw material innovations, or chose to voluntarily accept federally-enforceable limits on their potential to emit (PTE) HAPs would still be required to continually comply as a major HAP emitting source.  This has resulted in a significant added cost burden to facilities and, as an unintended consequence, has disincentivized them to make investments to improve air quality.

Over the years, there have been attempts to change the OIAI policy in published Federal Register proposals but were never finalized. Mr. Werhum’s memorandum is a complete reversal of the OIAI policy.  As expected, the Werhum memo has drawn opposition, including a legal challenge from several environmental groups as well as several published opinions that argue the policy reversal would ultimately result in higher HAP emissions.  While some states quickly accepted the Werhum policy change into their air permitting programs to accommodate those facilities that wish to pursue the process of reclassification, others have been reluctant to do so. 

Final Thoughts

We typically form our opinions based on our personal expertise and our own experiences.  Based on my experience assisting many facilities through the interpretation and application of complex air quality regulations, the reversal of the OIAI policy makes sense.  Large manufacturing complexes with significant emissions are not the types of facilities that would pursue reclassification; they need the legal right to emit as a major HAP source and function to comply with the applicable regulatory requirements as such.  Rather, the small to medium-sized facilities that may only emit one or two HAP compounds but otherwise exceed the major source threshold could benefit from reclassification.  The following are a couple of actual projects that I have personally been involved with that serve as excellent examples of this:

An electronics manufacturing facility that employed nearly 3,000 people in the 1990s manufactured specialty and bulk electronic components.  They became subject to a major source MACT resulting from the use of a solvent containing a HAP compound.  During the 2000s, the high-volume bulk manufacturing process was relocated to operations outside the U.S.  Today, the facility only manufactures low-volume specialty electronic components and generates actual HAP emissions of less than one ton per year; however, costly compliance with the major source regulation must continue even though there is no added benefit to improving air quality.

A military components manufacturer was historically subject to major source MACT regulations for emissions of HAP compounds present in a primer used to coat manufactured parts. Two years ago, the facility invested over a million dollars in capital to make process changes to replace the solvent-based primer with one that is water-based – a change that significantly reduced their HAP emissions that were not possible at the time the MACT became applicable.  The facility is now a candidate to voluntarily accept federally-enforceable limits on HAP PTE and be reclassified as an area source; however, the state where they reside is resistant to the OIAI policy change.

Mr. Wehrum has indicated that the USEPA has a fully-formed proposed rule to reverse the OIAI policy with rulemaking ready for the Federal Register.  Will it become a final rule?  We shall see.  Similar attempts in the past have languished.

Again, my experience with facilities that are candidates to be reclassified as area sources, would do so without increasing HAP emissions.  If state-level opponents to the policy change have their own examples where HAP emissions might increase the following reclassification, then my hope is that potential applicants be reviewed on a case-by-case basis.  I expect many would accept reasonable measures to ensure their HAP emissions will not increase to ultimately avoid an applicable, burdensome major source MACT standard.

To learn more about OIAI policy, see how your state is reacting to it or how this could affect your manufacturing sites, feel free to contact me at –  I will be happy to answer your questions.

  1. Wehrum, William L., Reclassification of Major Sources as Area Sources Under Section 112 of the Clean Air Act, USEPA, January 25, 2018.
  2. Seitz, John S., Potential to Emit for MACT Standards – Guidance on Timing Issues, USEPA, May 16, 1995.
  3. California Communities Against Air Toxics, et al USEPA et al, U.S. Court of Appeals For The District of Columbia, March 26, 2018.
  4. “Once In Always In” Guidance for Major Sources under the Clean Air Act, Environmental Law at Harvard,

About the Author

Gary Yoder provides regulatory compliance oversight for ClimeCo’s various service platforms, including air-permit application development, emission-rate calculations, air dispersion modeling, monitoring, recordkeeping and reporting system implementation.  Gary brings more than 25 years of industrial air-quality compliance expertise to his clients.