4 The record articles

U.S. EPA Finalizes Guidance on Fine Particulates and Ozone Significant Impact Levels

Posted: May 1st, 2018

Authors: Dan D. 

On April 17, 2018, the U.S. Environmental Protection Agency (U.S. EPA) Office of Air Quality Planning and Standards (OAQPS) finalized guidance and supporting documents recommending Significant Impact Levels (SILs) for ozone (O3) and fine particulates (PM2.5) that are used as part of the Prevention of Significant Deterioration (PSD) permitting program.  U.S. EPA had provided draft guidance on the SILs in August 2016, which I summarized in an August 2016 4TR Article and followed up with a webinar some of you may have participated in.

As a quick refresher, SILs are utilized to represent a pollutant specific concentration level that U.S. EPA has determined to be insignificant with respect to the corresponding National Ambient Air Quality Standard (NAAQS) or PSD increment.  SILs can be utilized in PSD air quality modeling to demonstrate that the level of pollutant concentrations resulting from project-related emissions are insignificant and that an air quality modeling analysis to demonstrate compliance with the NAAQS and/or PSD increment is not necessary.  SILs are essentially a permit streamlining tool and can be an important consideration for strategizing how to permit a project.

Below is a summary of the SILs which were not changed from the draft to final guidance memorandum.

That being said, my experience with a wide range of state agencies is that they will use the guidance and the SILs.  The 2016 draft and 2018 final guidance affects the SILs that were part of the 2010 PSD rulemaking.  Specifically, the 2010 PSD Class II PM2.5 annual SIL was reduced from 0.3 micrograms per cubic meter (µg/m3) to 0.2 µg/m3, the 2010 PSD Class I PM2.5 annual SIL was reduced from 0.06 µg/m3 to 0.05 µg/m3, and the 2010 PSD Class I 24-hour PM2.5 SIL was increased from 0.07 µg/m3 to 0.27 µg/m3.  In addition, the 2016 draft and 2018 final guidance adds an O3 SIL.

What this means for your facility is that it will become harder to demonstrate that emissions from your project will result in insignificant concentration levels relative to the annual PM2.5 NAAQS and/or PSD increment and that more involved NAAQS and PSD increment air quality modeling demonstrations will be required.  Thus, you will want to explore different strategies to avoid triggering PSD applicability, (are you thinking project emissions accounting, you should be!!)  However, if you are currently involved or will be involved in a PSD permitting project be sure to connect with your permitting authority to confirm if they will utilize the updated SILs.

For more information on how the updated SILs could affect your current or next project please contact Dan Dix at ddix@all4inc.com or 610.933.5246 x118.


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