UPA's Major Stationary Source Precursor Demonstration for NOx, SOx, VOC, and NH3 in the Salt Lake City 24-hour PM2.5 Serious Nonattainment Area

On 09/05/2018, the Utah Air Quality Board (UAQB) heard a prepared statement presented by the Utah Petroleum Association (UPA) on comments submitted during the Utah SIP, Section IX, Part H comment period. As part of that comment period, UPA submitted a precursor demonstration modeling report titled Major Stationary Source Precursor Demonstration for NOx, SOx, VOC, and NH3 in the Salt Lake City 24-hour PM2.5 Serious Nonattainment Area. The report can be reviewed here: https://deq.utah.gov/air-quality/air-quality-rule-plan-changes-open-public-comment

An approved Stationary Source Precursor demonstration by the EPA Administrator results in elimination of the requirement to impose additional Best Available Control Technology controls for point source precursors as contained in the Utah SIP, Section IX, Part H, Emission Limits and Operating Practices.

Precursor demonstrations to exclude precursors that do not significantly contribute to the formation of secondary PM2.5 in the particular airshed are typically prepared and submitted by air quality agencies. The analysis currently being presented for public comment was prepared by the Utah Petroleum Association, not the Utah Division of Air Quality (UDAQ). UDAQ feels it is prudent to perform our own analysis in consultation with its EPA partners instead of accepting the conclusions proffered by the commenter. UDAQ can then determine if controlling precursor emissions from major stationary sources is appropriate in the SLC NAA.

UDAQ has identified several concerns regarding the Major Stationary Source Precursor Demonstration submitted as public comment by UPA:

Ambient PM2.5 in the SLC NAA airshed is largely composed of secondary PM2.5 formed by precursors, not primary PM2.5. In addition, as shown in the SLC NAA SIP, empirical evidence points to the success in declining concentrations of ambient PM2.5 from controlling precursor emissions.

UPA's precursor demonstration analysis was based on EPA's draft guidance, which identifies a threshold of 1.5 microgram/m ³. Considering Utah has previously implemented emissions controls that resulted in large reductions, Utah continues to look at controls that may only produce marginal benefits. Therefore, the threshold established in the draft guidance may not be appropriate in the SLC NAA, particularly when looking at the precursors cumulatively.

Included in the SIP is a weight of evidence discussion that illustrates potential shortcomings in the model that affect its sensitivity to simulated reductions in precursor emissions. Considering this, UPA's analysis with the same model may have perpetuated these same shortcomings.

The UAQB proposed the Ramboll precursor demonstration for a 30-day public comment period. The public comment period closes at 5:00 PM on October 30, 2018. Comments postmarked on or before that date will be accepted. Comments may be submitted by email to [e-mail] or by mail to:

Bryce C. Bird
ATTN: UPA Precursor Demonstration
Utah Division of Air Quality
PO Box 144820
Salt Lake City, UT 84114-4820

UPA's comments can be found here: https://deq.utah.gov/air-quality/public-comments-regarding-revisions-to-section-ix-control-measures-for-area-and-point-sources-part-h-emission-limits