A Year-End Review of EPA’s Recent Air Permitting Guidance Changes

As we enter into 2019, it is important to reflect on the air permitting guidance changes we have seen in what has been a very active year in EPA air permitting guidance. These guidance changes, especially those under the complex NSR review process, will impact the air permitting process for capital projects going forward. Below is just a brief summary of some of the major EPA actions affecting the air permitting process in 2018:

Once In, Always In Policy

Withdrawal of the “Once In, Always In” policy was published on January 25, 2018. This memorandum reverses a long-standing policy that EPA has held since 1995 that a source subject to major source standards for Hazardous Air Pollutants (HAP) would always remain subject to those standards, even if it subsequently reduces its emissions below the major source threshold. (Link)

Project Emissions Accounting

Changes to the NSR “Netting” process were published on March 13, 2018. This memorandum establishes the concept of “Project Emissions Accounting,” and allows a facility subject to NSR review to consider both emissions increases and decreases in the first step of the NSR review process, rather than just increases. (Link)


President Trump issued a memo to EPA on April 12, 2018, which was followed by the EPA “Back-to-Basics” memorandum on May 9, 2018. Both of these memoranda address the National Ambient Air Quality Standards (NAAQS) review process and aim to make the process more transparent, and stress that attainment determinations be made in a timely manner. (Link 1, Link 2)

Source Aggregation

EPA clarified source aggregation and the definition of “Common Control” in a letter to the Pennsylvania Department of Environmental Protection on April 30, 2018 regarding Meadowbrook Energy, LLC. Further refinements to source aggregation policy were included in an October 16, 2018 letter from EPA to the Wisconsin Department of Natural Resources regarding the Janesville City Landfill. Both letters stress that common control is not merely the ability to influence another facility, but the power to direct activities which would directly impact air emissions and compliance obligations. (Link 1, Link 2)

Draft guidance on source aggregation and adjacency in NSR review was published on September 4, 2018. This guidance stresses that functional interrelatedness should not enter into a decision on whether or not two sources are “adjacent,” and that adjacent means physical proximity only. This guidance does not, however, include a physical distance threshold for adjacency, as is used in the industry-specific oil and gas adjacency criteria (one quarter mile). (Link)

ACE Rule

On August 21, 2018, EPA proposed the Affordable Clean Energy Rule as a replacement to the 2015 Clean Power Plan. This rule establishes emissions guidelines for states to develop plans to address Greenhouse Gas (GHG) emissions from coal-fired power plants. (Link)

Ambient Air

On November 9, 2018, EPA published draft guidance on the definition of “ambient air.” If finalized, this guidance would allow ambient air analyses to exclude areas that are inaccessible due to reasons other than just fencing or physical barriers. Public comment on this draft guidance is open through December 21, 2018. (Link)

Project Aggregation

On November 15, 2018, EPA published a reconsideration of an earlier action in 2009 that clarifies what is considered a “project” under New Source Review (NSR) and when projects should be aggregated together during an NSR analysis. This action affects how facilities going through Prevention of Significant Deterioration (PSD) and Nonattainment New Source Review (NNSR) characterize their projects when determining whether they constitute a “major modification.” While there will still be some case-by-case element to what constitutes a “project,” this action gives regulated entities as well as regulators criteria to help make a judgment on whether certain changes at a facility should be aggregated in an NSR analysis. (Link)

With all the movement we saw in 2018, we can expect 2019 to be another active year. PPM will continue to stay up-to-date on the latest regulatory developments and summarize their impact on the regulated community.

If this summary has sparked your interest in a certain area, please feel free to reach out to ned.coleman@ppmco.com for a collaborative discussion regarding your facility.


Contributed by Ned Coleman, P.E., Senior Environmental Engineer