EPA PM2.5 and O3 Draft Modeling Guidance Updates
On February 10, 2020, the U.S.EPA published draft guidance providing updates to the previous Guidance for PM2.5 Permit Modeling to reflect the 2017 revisions to the 40 CFR part 51, Appendix W Guideline on Air Quality Models and incorporate appropriate sections for ozone.
[Spoiler Alert] There does not appear to be any unexpected or considerable changes at this time. The draft guidance seems to be consistent with methodologies we are already employing in our active air quality analyses and appears to simply consolidate recommendations from the past several years. However, with that said, this guidance does warrant special consideration when conducting PM2.5 and ozone air quality analyses as it will likely supersede prior guidance.
The U.S.EPA’s efforts since 2016 focused on updating the 2014 Guidance for PM2.5 Permit Modeling to:
- incorporate ozone;
- update aspects of the PM2.5 increment section;
- reflect the 2017 Appendix W Guideline revisions and 2018 “SILs Guidance;” and
- revise based on ongoing feedback and knowledge gained from practical application in compliance demonstrations.
Per recent communication with U.S.EPA’s modeling group, they are in the process of briefing senior management on revisions from stakeholder comments. The U.S.EPA is still planning a late 2020 or early 2021 release for the final guidance document.
Even though the guidance is not final, the agency is recommending that permit applicants proceed with following the recommendations of the draft guidance. Additionally, it is appropriate for applicants to develop modeling protocols for review with their respective permit reviewing authorities on all permitting projects involving ozone and fine particulate to ensure that there are no issues in the approach for the compliance demonstration.
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Summary of Guidance Document Timeline:
May 20, 2014: EPA Published Guidance for PM2.5 Modeling
January 17, 2017: EPA published Guideline on Air Quality Models (40 CFR Part 51, Appendix W)
February 10, 2020 EPA published DRAFT Guidance for Ozone and Fine Particulate Matter Permit Modeling
March 12, 2020 EPA hosted webinar providing overview and open dialogue related to the February 10, 2020 Draft Guidance.
April 17, 2020 Deadline to submit comments to EPA on February 10, 2020 Draft Guidance. EPA extended deadline to April 17 from the original deadline of March 27, 2020
May 2020 Canceled: EPA workshop to engage with air quality community was canceled due to COVID-19.
Later this Year
or Early 2021: EPA anticipated
timeline for publishing final guidance.
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