DAQ-2024-009992

September 3, 2024

Bryce Bird, Director
Utah Division of Air Quality
P.O. Box 144820
Salt Lake City, Utah 84114-4820

RE: EPA Region 8 Comments on Proposed Revisions to Utah’s Moderate Area Ozone
Reasonable Further Progress State Implementation Plan for the 2015 Ozone National
Ambient Air Quality Standard for the Northern Wasatch Front Nonattainment Area
(Proposed Amendments to R307-110-13)

Dear Director Bird:

Thank you for the opportunity to provide comments on the State of Utah’s proposed revisions
to the reasonable further progress (RFP) State Implementation Plan (SIP) (Sections IX.D.11) for
the Northern Wasatch Front (NWF) Nonattainment Area (NAA) under the 2015 ozone National
Ambient Air Quality Standard, which were approved for public comment by the Utah Air Quality
Board on July 9, 2024.

The EPA has concerns with Utah’s reliance on reductions of nitrogen oxides (NOX) to satisfy the
Clean Air Act (CAA) RFP requirement in the proposed revisions. The CAA and the EPA’s
implementing regulations do not allow reliance on NOX emission reductions for a Moderate RFP
ozone plan unless the EPA has previously approved a Moderate RFP ozone plan for the
nonattainment area. Utah does not have a previously approved Moderate RFP ozone plan and
therefore cannot rely on NOx emission reductions to satisfy the requirement. The volatile
organic compound (VOC) reductions achieved under the particulate matter (PM2.5) SIP do not
substitute for a previously approved Moderate RFP ozone plan. If the state submits a SIP
revision that relies on NOX reductions, as in the proposed revisions, EPA does not currently see a
basis for proposing approval of such a SIP revision.

For areas that cannot satisfy the 15% VOC reduction requirement, the CAA permits a state to
pursue an “RFP waiver,” under which areas may show less than a 15% VOC reduction if they
meet the requirements of CAA section 182(b)(1)(A)(ii). This includes requirements to
significantly tighten the major source threshold and impose higher emissions offset
requirements for new sources (see CAA section 182(b)(1)(A)(ii)).

EPA understands that Utah’s efforts to control VOCs in the Salt Lake City, Utah area over the past
several decades have made it more difficult to find sufficient additional VOC reductions for the
purpose of satisfying the RFP requirement. In light of these considerations, EPA encourages
Utah to thoroughly assess how long it would take the state to achieve the full 15% in VOC
reductions from the 2017 base year, even if doing so will take longer than the six years
contemplated under CAA section 182(b)(1)(A)(i).1 EPA historically has approved such an RFP
demonstration, provided the state has included robust technical support that demonstrates that
the state would achieve the 15% VOC reductions as soon as practicable, i.e., that there are no
additional measures the state could implement to achieve the full 15% VOC reductions more
expeditiously.2

To the extent Utah is taking comment on the entire ozone SIP, we refer Utah back to our July 17,
2023 comment letter. Many of the concerns we stated in that letter may still be applicable to
the draft out for public comment. As previously conveyed, our preliminary assessment is that
the submitted and proposed revised ozone SIP needs additional development and analysis so
that it can be fully approved by the EPA. However, we will not reach any final conclusions until
after the state formally submits proposed revisions to the ozone SIP and after we conduct our
own notice and comment rulemaking.

As always, we are committed to continuing to work with you to help address the issues
identified in this letter. If you have any questions, please contact me at 720-391-2147, or your
staff may contact Amanda Brimmer at [e-mail].

Sincerely,

X_____________________________

Adrienne Sandoval
Director, Region 8 Air and Radiation Division

1 See Final rule, Approval and Promulgation of Implementation Plans; State of Missouri, 65 FR 31485, 31486 (May 18, 2000)
(identifying 2003 “demonstration date” for RFP); Sierra Club v. EPA, 252 F.3d 943 (8th Cir. 2001) (upholding EPA decision).
2 See CAA section 182(b)(1)(A)(i) and 40 CFR 51.1310(a)(4)(i) for RFP requirements for Moderate nonattainment areas for the
2015 ozone NAAQS.