DAQ-2024-009249

UTAH DIVISION OF AIR QUALITY
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Utah Division of Air Quality

State Implementation Plan

2015 Ozone NAAQS Northern Wasatch Front
Moderate Nonattainment Area

[2023]2024

Section IX Part D.11

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Contents
List of Acronyms ................................................................................................................................8
Chapter 1 – Background and State Implementation Plan (SIP) Requirements ..................................... 10
1.1 How Ozone is Formed ....................................................................................................................... 10
1.2 Health Effects of Ozone ..................................................................................................................... 10
1.3 History of Ozone NAAQS in the Northern Wasatch Front................................................................. 11
1.4 2015 NAAQS Ozone NAAs ................................................................................................................. 12
1.5 Responsible Air Agencies ................................................................................................................... 15
1.6 Moderate SIP Elements ..................................................................................................................... 15
1.7 Moderate Area SIP Development Process ........................................................................................ 17
Chapter 2 – NWF Monitoring Network .............................................................................................. 18
2.1 Monitoring Network .......................................................................................................................... 18
2.2 Ozone Monitoring Data ..................................................................................................................... 20
2.3 Data Quality Assurance ..................................................................................................................... 22
Chapter 3 - Baseline and Future Year Emission Inventories ................................................................ 25
3.1 Emission Inventory Background ........................................................................................................ 25
3.2 Baseline 2017 Emission Inventory and Projected 2023 Emission Inventory ..................................... 25
Chapter 4 – Reasonably Available Control Technology (RACT) Analysis and Nonattainment New Source
Review (NNSR) ................................................................................................................................. 34
4.1 Reasonably Available Control Technology (RACT) Overview ............................................................ 34
4.2 Utah RACT Process ............................................................................................................................ 35
4.3 Big West Oil LLC - Refinery ................................................................................................................ 36
4.4 Chevron Products Company – Salt Lake Refinery ............................................................................. 40
4.5 Hexcel Corporation ............................................................................................................................ 45
4.6 Hill Air Force Base .............................................................................................................................. 48
4.8 Kennecott Utah Copper Bingham Canyon Mine and Copperton Concentrator ................................ 56
4.9 KUC Smelter and Refinery ................................................................................................................. 60
4.10 LHoist North America of Arizona, Inc. ............................................................................................. 66
4.11 Pacificorp Energy Gadsby Power Plant............................................................................................ 67
4.12 Tesoro Refining & Marketing Company LLC dba Marathon Refinery ............................................. 70
4.13 Utah Municipal Power Agency West Valley Power Plant ................................................................ 75
4.14 University of Utah ........................................................................................................................... 77
4.15 US Magnesium LLC .......................................................................................................................... 80
4.16 Chevron Salt Lake Marketing Terminal ........................................................................................... 85

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4.17 Holly Energy Partners Woods Cross Terminal ................................................................................. 87
4.18 Tesoro Logistics Operations LLC Truck Loading Rack and Remote Tank Farm ................................ 89
4.19 CTG and ACT .................................................................................................................................... 92
4.20 RACT Conclusions ............................................................................................................................ 92
4.21 Nonattainment New Source Review (NNSR) ................................................................................... 95
Chapter 5 - Reasonably Available Control Measures (RACM) Analysis ................................................ 96
5.1 Overview............................................................................................................................................ 96
5.2 RACM Analysis ................................................................................................................................... 97
5.3 RACM Analysis Conclusion .............................................................................................................. 104
Chapter 6 – Inspection and Maintenance (I/M) Program ................................................................. 106
6.1 Overview of I/M Programs .............................................................................................................. 106
6.2 Federal Requirements ..................................................................................................................... 106
6.3 I/M Testing ...................................................................................................................................... 107
6.4 Utah I/M Program History and General Authority .......................................................................... 107
6.5 UDAQ Evaluation of Current I/M Program ...................................................................................... 108
6.6 Implementation of I/M Program in Tooele County ......................................................................... 110
Chapter 7 – Reasonable Further Progress (RFP) ............................................................................... 112
7.1 Reasonable Further Progress .......................................................................................................... 112
7.2 Methodology ................................................................................................................................... 113
7.3 RFP and Anthropogenic VOC Emission Reductions ......................................................................... 113
7.4 Anthropogenic NOx Emissions ......................................................................................................... 116
7.5 CAA Section 172(c)(2) and NOx Substitutions ................................................................................. 119
[7.5]7.6 Future SIP Emission Reductions ............................................................................................... 124
7.7 RFP Conclusions ............................................................................................................................... 127
Chapter 8 - Attainment Demonstration and Weight of Evidence ...................................................... 128
8.1 Background ...................................................................................................................................... 128
8.2 Photochemical Modeling Platform.................................................................................................. 129
8.3 Weight of Evidence (WOE) .............................................................................................................. 137
8.4 Conclusion ....................................................................................................................................... 150
Chapter 9 - 179B(a) Prospective Demonstration .............................................................................. 151
9.1 Overview.......................................................................................................................................... 151
9.2 Ozone Source Apportionment (OSAT) Modeling ............................................................................ 152
9.3 Ozone Source Apportionment Modeling Results ............................................................................ 155

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9.4 Future Design Values after Removal of Contributions from International Anthropogenic Emissions
............................................................................................................................................................... 157
9.5 Conclusion ....................................................................................................................................... 158
Chapter 10 - Transportation Conformity and Motor Vehicle Emission Budget .................................. 161
10.1 Introduction ................................................................................................................................... 161
10.2 Transportation Conformity............................................................................................................ 161
10.3 – Consultation ............................................................................................................................... 161
10.4 Motor Vehicle Emission Budgets (MVEB) ..................................................................................... 162
10.5 Emission Budgets for the Northern Wasatch Front NAA .............................................................. 163
10.6 Implementation of MVEB in Transportation Conformity Determinations .................................... 163
Chapter 11 - Contingency Measures ............................................................................................... 165
11.1 Overview ....................................................................................................................................... 165
11.2 Contingency Measures .................................................................................................................. 165
Chapter 12 - Environmental Justice & Title VI Considerations .......................................................... 167
12.1 Environmental Justice ................................................................................................................... 167
12.2 Title VI of the Civil Rights Act ........................................................................................................ 167
12.3 Screening-Level Analysis ............................................................................................................... 168
12.4 Identified Stakeholders ................................................................................................................. 169
12.5 Stakeholder Outreach, Meaningful Involvement, and Information Distribution ......................... 169

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List of Tables
Table 1: NWF NAA marginal requirements under the CAA. ....................................................................... 14
Table 2: Ozone values in ppm from sites in NWF NAA from 2018 - 2020. Values calculated in accordance
with 40 CFR Part 50, Appendix U. ............................................................................................................... 14
Table 3: SIP Requirements .......................................................................................................................... 16
Table 4: NWF 4th Maximum 8-Hour Ozone Values reported in ppm......................................................... 20
Table 5: NWF 8-Hour Ozone Three-Year Average 4th Maximum Ozone Values. ....................................... 21
Table 6: NWF Ozone Data Recovery Rates shown as percentages............................................................. 23
Table 7: 2017 Nonattainment Area Emission Inventory (tons per day) ..................................................... 26
Table 8: 2023 Projected Nonattainment Area Emission Inventory (tons per day) ..................................... 27
Table 9: Biogenic Emissions (tons per day) ................................................................................................. 27
Table 10: Solvent Emissions Inventory ....................................................................................................... 28
Table 11: 2023 Solvent Emissions Inventory .............................................................................................. 28
Table 12: 2017 Area Source Emission Inventory ........................................................................................ 29
Table 13: Area Source Emission Inventory ................................................................................................. 29
Table 14: Non-Road, Rail and Airports Emission Inventory ........................................................................ 30
Table 15: 2023 Non-Road, Rail and Airports Emission Inventory ............................................................... 30
Table 16: 2017 Point Sources and EGUs Emission Inventory ..................................................................... 31
Table 17: 2023 Point Sources and EGUs Emission Inventory ..................................................................... 32
Table 18: 2017 On-road emission inventory for ozone weekday ............................................................... 32
Table 19: 2023 On-road emission inventory for ozone weekday ............................................................... 32
Table 20: 2017 ERC Bank Emission Inventory ............................................................................................. 33
Table 21: 2023 ERC Bank Emission Inventory ............................................................................................. 33
Table 22: Big West Oil LLC Refinery Facility-Wide Emissions ..................................................................... 37
Table 23: Big West Oil LLC - Refinery .......................................................................................................... 37
Table 24: Chevron Products Company – Salt Lake Refinery Facility-Wide Emissions ................................ 40
Table 25: Chevron Products Company – Salt Lake Refinery ....................................................................... 41
Table 26: Hexcel Corporation Facility-Wide Emissions ............................................................................... 45
Table 27: Hexcel Corporation ..................................................................................................................... 45
Table 28: Hill Air Force Base Facility-Wide Emissions ................................................................................. 48
Table 29: Hill Air Force Base........................................................................................................................ 50
Table 30: Holly Frontier Sinclair Woods Cross Refinery Facility-Wide Emissions ....................................... 53
Table 31: Holly Frontier Sinclair Woods Cross Refinery .............................................................................. 54
Table 32: KUC Bingham Canyon Mine and Copperton Concentrator Facility-Wide Emissions .................. 57
Table 33: Kennecott Utah Copper (KUC): Bingham Canyon Mine and Copperton Concentrator .............. 57
Table 34: KUC Smelter and Refinery Facility-Wide Emissions .................................................................... 61
Table 35: Kennecott Utah Copper: Smelter and Refinery .......................................................................... 61
Table 36: LHoist North America of Arizona Facility Facility-Wide Emissions .............................................. 66
Table 37: Lhoist North America of Arizona, Inc. ......................................................................................... 67
Table 38: Pacificorp Energy Gadsby Power Plant Facility-Wide Emissions ................................................. 68
Table 39: PacifiCorp Energy: Gadsby Power Plant ...................................................................................... 68
Table 40: Tesoro Marathon Refinery Facility-Wide Emissions ................................................................... 70
Table 41: Tesoro Refining and Marketing Company LLC dba Marathon Refinery ...................................... 70
Table 42: West Valley Power Plant Facility-Wide Emissions ...................................................................... 75
Table 43: Utah Municipal Power Agency West Valley Power Plant ........................................................... 76
Table 44: University of Utah Facility-Wide Emissions ................................................................................. 77

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Table 45: University of Utah ....................................................................................................................... 78
Table 46: US Magnesium LLC Facility-Wide Emissions ............................................................................... 81
Table 47: US Magnesium RACT Determination .......................................................................................... 81
Table 48: Chevron Salt Lake Marketing Terminal Facility-Wide Emissions ................................................ 86
Table 49: Chevron Salt Lake Marketing Terminal ....................................................................................... 86
Table 50: Holly Energy Partners Woods Cross Terminal Facility-Wide Emissions ...................................... 88
Table 51: Holly Energy Partners Woods Cross Terminal ............................................................................. 88
Table 52: Tesoro Logistics Operations LLC TLR and RTF Facility-Wide Emissions ....................................... 90
Table 53: Tesoro Logistics Operations LLC TLR and RTF ............................................................................. 90
Table 54: Controls identified by RACT analysis for the NWF NAA. ............................................................. 94
Table 55: Existing area source VOC rules in the NWF NAA ......................................................................... 97
Table 56: VOC RACM Assessment Summary .............................................................................................. 98
Table 57: NOX RACM Assessment Summary ............................................................................................. 102
Table 58: RACM Identified Control Strategies .......................................................................................... 104
Table 59: 2023 Davis County Summer Basic Performance Modeling ....................................................... 109
Table 60: 2023 Salt Lake Summer Basic Performance Modeling.............................................................. 109
Table 61: 2023 Utah County Summer Basic Performance Modeling ....................................................... 110
Table 62: 2023 Weber County Summer Basic Performance Modeling .................................................... 110
Table 63: I/M Program Implementation Evaluation for Tooele County in 2023 ...................................... 111
Table 64: Anthropogenic VOC Emission Reductions from 2017 to 2023 for the NWF ............................. 114
Table 65: Anthropogenic NOx Emission Reductions from 2017 to 2023 for the NWF ............................. 116
Table 66: VOC reductions in the NWF NAA during past SIPs timeline demonstrating a 15% VOC reduction
relative to NAAQS base years………………………………………………………………………………………………………………120
Table 67: VOC and NOx reduction in the NWF NAA during the moderate SIP timeline………………………..121
Table [66]68: Performance statistics for maximum daily average 8-hour (MDA8) ozone on all days of the
modeling episode. Results are shown for monitors in the 1.33 km modeling domain. ........................... 131
Table [67]69: Performance statistics for maximum daily average 8-hour (MDA8) ozone on high O3 days
(observed MDA8 > 60 ppb). Results are shown for monitors in the 1.33 km modeling domain. ............ 132
Table [68]70: Baseline design values (BDV), relative response factors (RRF), future design values (FDV) at
Bountiful, Hawthorne and Herriman monitoring locations. Design values before and after exclusion of
days impacted by wildfire smoke are shown.* indicates design value after removal of wildfire smoke-
impacted ozone exceedance values. ........................................................................................................ 136
Table [69]71: Baseline design values (BDV), relative response factors (RRF), future design values (FDV) at
monitors within the northern Wasatch Front ozone non-attainment area. ............................................ 136
Table [70]72: 2023 contributions from upwind states to NWF NAA (ppb) as identified by EPA 2016v2
modeling ................................................................................................................................................... 140
Table [71]73: NOx and VOC reductions resulting from PM2.5 SIPs. ........................................................... 143
Table [72]74: Emission reductions associated with incentive programs in and around the NWF NAA ... 147
Table [73]75: Emission source categories considered in 2023 ozone source apportionment modeling. 154
Table [74]76: Future design values (FDV), source contribution estimates for international anthropogenic
emissions (IAE) and adjusted future design values (FDV adj) at monitoring locations within the northern
Wasatch Front non-attainment area. ....................................................................................................... 158
Table [75]77: NWF Ozone 2023 NAA MVEB ............................................................................................. 163
Table [76]78: Percent Emission Reductions Based on 2017 Base Year Inventory .................................... 166
Table [77]79: Environmental Justice Indexes Over the 80th Percentile in the NWF NAA ........................ 168

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List of Figures
Figure 1: Wasatch Front Ozone Nonattainment Areas. .............................................................................. 13
Figure 2: Monitoring sites in the NWF NAA ................................................................................................ 19
Figure 3: Ozone 4th Highest 8-Hour Concentration in Wasatch Front ....................................................... 22
Figure 4: NWF Anthropogenic VOC Emission Inventories ........................................................................ 115
Figure 5: NWF Anthropogenic NOx Emission Inventories ......................................................................... 117
Figure 6: NOx-attributable (brown) and VOC-attributable (green) ozone at Hawthorne (left panel) and
Bountiful (right) monitoring stations on average over all days of the modeling episode. ....................... 118
Figure 7: 12/4/1.33 km CAMx Modeling Domains ................................................................................... 130
Figure 8: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone
concentration (O3_8hrmax) at the Bountiful monitoring station. ........................................................... 132
Figure 9: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone
concentration (O3_8hrmax) at the Hawthorne monitoring station. ........................................................ 133
Figure 10: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone
concentration (O3_8hrmax) at the Erda monitoring station. ................................................................... 133
Figure 11: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone
concentration (O3_8hrmax) at the Herriman monitoring station. ........................................................... 133
Figure 12: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone
concentration (O3_8hrmax) at the Harrisville monitoring station. .......................................................... 134
Figure 13: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone
concentration (O3_8hrmax) at the Ogden monitoring station. ............................................................... 134
Figure 14: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone
concentration (O3_8hrmax) at Gothic Colorado monitoring station. ...................................................... 134
Figure 15: Ozone Attributed to Domain-Wide Sources at Hawthorne as simulated 8-hour mean daily
ozone concentrations along the Wasatch Front. ...................................................................................... 139
Figure 16: Episode average of simulated 8-hour mean daily ozone concentrations at Hawthorne along
the Wasatch Front. ................................................................................................................................... 139
Figure 17: Ozone Attributed to Domain-Wide Sources ............................................................................ 142
Figure 18: MDA8 ozone source apportionment exceedance vs. non-exceedance days .......................... 142
Figure 19: Map of source regions used in 2023 ozone source apportionment modeling for the 4 and 1.33
km domains. Each color represents a different source region. ................................................................ 153
Figure 20: Source contributions by region and emission sector to maximum daily 8-hr average (MDA8)
ozone concentration (ppb) at the Hawthorne monitoring station for each day of the modeling episode
(left panel) and on average over all days of the modeling episode (right panel). Results are based on
2023 OSAT model outputs for the 1.33 km modeling domain and spin-up days are excluded. .............. 156
Figure 21: Source contributions by region and emission sector to maximum daily 8-hr average (MDA8)
ozone concentration (ppb) at the Hawthorne monitoring station for each day of the modeling episode
(upper panel) and on average over all days of the modeling episode, exceedance days, top 10
exceedance days and non-exceedance days (lower panel). Results are based on 2023 OSAT model
outputs for the 1.33 km modeling domain and spin-up days are excluded. ............................................ 157
Figure 22: International contributions at Hawthorne monitor site on exceedance and non-exceedance
days. .......................................................................................................................................................... 159
Figure 23: EJ Indexes >80th percentile in Each NWF NAA Census Block .................................................. 167

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List of Acronyms
ACT = Alternative Control Techniques
AO = Approval Order
BDV = Base Design Value
CAA = Clean Air Act
CAMx = Comprehensive Air Quality Model with Extensions
CFR = Code of Federal Register
CO = Carbon Monoxide
CTG = Control Techniques Guidelines
DERA = Diesel Emissions Reduction Act
DV = Design Value
EGU = Electric Generating Units
EMP = Enhanced Monitoring Program
EPA = U.S. Environmental Protection Agency
EV = Electric Vehicles
FDV = Future Design Value
FHWA = Federal Highway Administration
FIP = Federal Implementation Plan
FR = Federal Register
HAP = Hazardous Air Pollutants
HYSPLIT = Hybrid Single–Particle Lagrangian Integrated Trajectory
ICT = Interagency Consultation Team
I/M = Inspection and Maintenance
MDA8 = Maximum Daily Average Ozone Over an 8-Hour period
MOVES3 = Motor Vehicle Emission Simulator (2014 Release)
MPE = Model Performance Evaluation
MPO = Metropolitan Planning Organization
MVEB = Motor Vehicle Emissions Budgets
NAA = Nonattainment Area
NAAQS = National Ambient Air Quality Standard
NESHAP = National Emission Standards for Hazardous Air Pollutants
NMOG – Non-Methane Organic Gases
NOx = Nitrogen Oxides
NSPS = New Source Performance Standards
NNSR = Nonattainment New Source Review
OBD = On-Board Diagnostics
OSAT = Ozone Source Apportionment
PPB = Parts per Billion
PPM = Parts per Million
PPMV = Parts Per Million by Volume
RACM = Reasonably Available Control Measures
RACT = Reasonably Available Control Technology
RFP = Reasonable Further Progress
RRF = Relative Response Factor
SIP = State Implementation Plan
SMOKE = Sparse Matrix Operator Kernel Emissions

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TIP = Transportation Improvement Program
TPD = Tons per Day
TPY = Tons per Year
TSD = Technical Support Document
UDAQ = Utah Division of Air Quality
VMT = Vehicle Miles Traveled
VOC = Volatile Organic Compounds
WOE = Weight of Evidence
WRF = Weather Research and Forecasting
ZEV = Zero Emission Vehicles

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Chapter 1 – Background and State Implementation Plan (SIP)
Requirements
1.1 How Ozone is Formed
Ozone is a highly unstable and oxidative gas made up of three atoms of oxygen covalently
bonded together. Tropospheric ozone is not directly emitted but is formed in the atmosphere through a
complex series of secondary and tertiary reactions. In short, Volatile Organic Compounds (VOCs) from a
variety of natural and anthropogenic sources react in the atmosphere with Nitrogen Oxides (NOx), and
to a lesser extent Carbon Monoxide (CO), in the presence of sunlight and heat to form ozone (Equation
1).

Equation 1
VOC + NOx + Sunlight + Heat = O3

Anthropogenic sources of VOCs and NOx include, but are not limited to automobile exhaust,
refueling vapors, solvents, complete and incomplete combustion of fuels, and industrial activities.
Natural sources include wildfires, biogenic activities, and soil respiration.
In the Northern Wasatch Front (NWF), elevated concentrations of ground-level ozone are
predominantly a summertime phenomenon associated with extended periods of high-pressure
coinciding with high temperatures, low relative humidity, limited cloud cover, and intense incoming
solar radiation. In addition to favorable atmospheric conditions for the local formation of ozone, the
high elevation of the NWF and its location within the Intermountain West contribute to the observed
elevated ozone concentrations.
1.2 Health Effects of Ozone
Exposure to elevated levels of ozone is linked to an array of respiratory and pulmonary
problems, primarily among susceptible populations and those participating in outdoor activities.1 These
health problems can include increased susceptibility to respiratory illnesses like pneumonia and
bronchitis, chest pain, inflammation of the respiratory tract, irritated and or permanently damaged lung
tissues, and cardiac impacts and aggravation of preexisting respiratory issues like asthma or chronic
obstructive pulmonary disease (COPD).
The Clean Air Act (CAA) requires the US Environmental Protection Agency (EPA) to set air quality
standards for certain criteria air pollutants, known as the National Ambient Air Quality Standards
(NAAQS), to protect both public health and the environment. States must develop plans to attain and
maintain these health-based standards called State Implementation Plans (SIPs). If an area is determined
to not meet these standards, then the SIP must be revised with plans on how the area will achieve the
standard by deadlines established in the CAA.

1 Devlin BR, Raub AJ, Folinsbee JL. (1997). Health effects of ozone. Science & Medicine;(3):8-17.

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1.3 History of Ozone NAAQS in the Northern Wasatch Front
Significant efforts have been made in reducing precursor emissions, primarily NOx and VOCs,
throughout the NWF over the last 40 years. Much of the more recent efforts have been targeted at
reducing Utah’s wintertime fine particulate matter (PM2.5), however, there is a long history of efforts to
combat ozone directly.
1.3.1 1979 1-Hour Ozone Standard
In 1977 EPA designated parts of the Wasatch Front including Davis, Salt Lake, Utah, and Weber
Counties as nonattainment for the 1-hour ozone standard of 0.120 parts per million (ppm). In 1981 both
Weber and Utah Counties were re-designated as attainment. In April of 1981, an ozone SIP was
submitted to EPA that demonstrated attainment of the standard for both Davis and Salt Lake Counties
by May 1, 1984. This ozone SIP submittal was fully approved by the EPA.
In November of 1990, Congress amended the CAA. Under the 1990 Amendments, each area of
the country that was designated nonattainment for the 1-hour ozone NAAQS, including Salt Lake County
and Davis County, was classified by operation of law as marginal, moderate, serious, severe, or extreme
nonattainment depending on the severity of the area's air quality problem. The ozone nonattainment
designation for Salt Lake County and Davis County continued by operation of law according to section
107(d)(1)(C)(i) of the CAA, as amended in 1990. Furthermore, this area was classified by operation of law
as moderate for ozone under CAA section 181(a)(1). On November 12, 1993, Utah submitted a formal
request to EPA that the Salt Lake/Davis County nonattainment area (NAA) be redesignated to
attainment of the 1-hour ozone NAAQS, and the State, in accordance with the CAA, submitted a
maintenance plan. In July of 1997, the EPA approved the Ozone Maintenance Plan for Salt Lake and
Davis Counties, effective August 18, 1997, and redesignated both counties to attainment for 1-hour
ozone NAAQS.
1.3.2 1997 8-Hour Ozone Standard
In July 1997, the EPA established a new, more rigorous standard for the 8-hour ozone NAAQS.
The new 8-hour standard was set at a level of 0.080 ppm averaged over an eight-hour period. To better
account for variable meteorological conditions that can influence ozone formation, a violation of the
standard occurs when the three-year average of the fourth-highest maximum value at a monitor
exceeds the federal standard. On April 30, 2004, EPA published the first phase of its final rule (Phase 1
Rule) to implement the 8-hour ozone NAAQS.2 At the same time, EPA also published 8-hour ozone
designations for all areas of the country. All areas of Utah were designated attainment or unclassifiable.
These designations became effective on June 15, 2004. The Phase 1 Rule provided that the 1979 1-hour
ozone NAAQS would be revoked following the effective date of the 8-hour ozone NAAQS, or June 15,
2005. This revocation action was affirmed on August 3, 2005.3 On November 29, 2005, EPA published
the Final Rule to Implement the 8-hour Ozone NAAQS - Phase 2.4

2 Final Rule to Implement the 8-Hour Ozone National Ambient Air Quality Standard—Phase 1, 69 Fed. Reg. 23,951 (April 30, 2004).
3 Identification of Ozone Areas for Which the 1-Hour Standard Has Been Revoked and Technical Correction to Phase 1 Rule, 70 Fed. Reg. 44,470 (Aug. 3, 2005).
4 Final Rule to Implement the 8-Hour Ozone National Ambient Air Quality Standard—Phase 2; Final Rule to Implement Certain Aspects of the 1990 Amendments
Relating to New Source Review and Prevention of Significant Deterioration as They Apply in Carbon Monoxide, Particulate Matter and Ozone NAAQS; Final Rule for
Reformulated Gasoline, 70 Fed. Reg. 71,612 (Nov. 29, 2005).

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The Utah Air Quality Board adopted a revised maintenance plan on January 3, 2007. Salt Lake
and Davis Counties were found to be in attainment on July 18, 1995, under the 1-hour ozone NAAQS5
and had been operating under an approved maintenance plan (62 Federal Register [FR] 38213) since July
17, 1997.6 This maintenance plan demonstrated that Salt Lake and Davis Counties had achieved the 8-
hour ozone standard and could maintain compliance with the standard through 2014.
1.3.3 2008 8-Hour Ozone Standard
In March, 2008, the EPA revised the 1997 8-hour NAAQS from 0.080 to 0.075 ppm averaged
over an 8-hour period. In 2012, EPA finalized the standard and issued rulemaking relevant to the
implementation of the rule.7 In 2015, EPA finalized the SIP requirements and NAA classifications and
determinations for this standard.8 Monitoring data indicated that all areas of Utah were attaining the
standard, and thus no SIP revisions were required for the state of Utah for this NAAQS.
1.4 2015 NAAQS Ozone NAAs
On October 26, 2015, the EPA promulgated a revision to the primary NAAQS for ground-level
ozone in accordance with Section 107(d) of the CAA. This revision lowered the standard from 0.075 to
0.070 ppm for the 4th highest daily maximum 8-hour concentration (MDA8) averaged over three years.9
As a result of the more stringent standard, effective on August 3, 2018, the EPA designated two areas
along the Wasatch Front as marginal NAA including the Northern Wasatch Front and Southern Wasatch
Front.10 The NWF NAA includes Salt Lake and Davis counties as well as portions of Tooele and Weber
counties (Figure 1).

5 Determination of Attainment of Ozone Standard for Salt Lake and Davis Counties, Utah, and Determination Regard ing Applicability of Certain Reasonable Further
Progress and Attainment Demonstration Requirements, 60 Fed. Reg. 36,723 (July 18, 1995).
6 Approval and Promulgation of Air Quality Implementation Plans; State of Utah; Salt Lake and Davis Counties Ozone Rede signation to Attainment, Designation of
Areas for Air Quality Planning Purposes, Approval of Related Elements, Approval of Partial NOX RACT Exemption, and Approval o f Weber County I/M Program, 62
Fed. Reg. 38,213 (July 17, 1997).
7 77 FR 30160
8 FR 80 12264
9 National Ambient Air Quality Standards for Ozone, 80 Fed. Reg. 65,292 (Oct. 26, 2015).
10 Additional Air Quality Designations for the 2015 Ozone National Ambient Air Quality Standards, 83 Fed. Reg. 25,776 (June 4, 2 018).

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Figure 1: Wasatch Front Ozone NAAs
1.4.1 Northern Wasatch Front Ozone NAA
The boundaries for the NWF NAA include three valleys that are part of the Intermountain West’s
basin and range geological province: Tooele Valley, the North Salt Lake Valley, and the Salt Lake Valley.
The majority of the approximately 1.8 million residents within the NAA reside in the Salt Lake valleys
situated along the base of the Wasatch Mountains. The three valleys consist of a variety of complex
topography including low and large valleys bordered by steep mountain terrain and a large body of
water—the Great Salt Lake. The average elevation of the three valleys is 4,327 feet above sea level with
the bordering Wasatch Mountains rising to elevations over 11,000 feet. The area experiences a dry-
summer continental climate with hot and dry summers dominated by persistent high-pressure systems.
The relatively high baseline elevation of over 4,000 feet, coupled with its warm and dry climate, and its
prominent location in the Intermountain West, results in a naturally high contribution of background
ozone in the NWF NAA11 during the typical summer ozone season.

1.4.2 NWF Marginal Ozone NAA Requirements
The NWF NAA failed to attain the standard by the marginal attainment date but has met all
statutory requirements for a marginal NAA under the CAA Section 182(a) as shown in Table 1.

11 Scientific assessment of background ozone over the U.S.: Implications for air quality management. Jaffe et al.

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Table 1: NWF NAA marginal requirements under the CAA.
CAA Requirement Federal Register Approval
2017 Base Year Emission Inventory 86 FR 35404, July 6, 2021
Emission Inventory Statement Rule 87 FR 24273, April 25, 2022
Nonattainment New Source Review 87 FR 24273, April 25, 2022

The design value (DV) calculated from data collected from 2018-2020 was used to determine if
the area attained the standard by the attainment date of August 3, 2021. Validated data in EPA’s Air
Quality System (AQS) shows a 3-year average of the 4th high maximum daily 8-hour ozone value at the
NWF Bountiful monitor of 0.077 ppm, with exceedances also observed at all other monitoring sites in
the NAA except Erda in Tooele County (Table 2).

Table 2: Ozone values in ppm from sites in NWF NAA from 2018 - 2020. Values calculated in accordance with 40 CFR Part 50,
Appendix U.

On October 7, 2022, the EPA finalized rulemaking where it determined that the NWF did not
attain by the attainment date and reclassified the area to moderate with a new attainment date of
August 3, 2024.12 The effective date of this rulemaking was November 7, 2022, marking the effective
date of moderate designation for the NWF NAA.

1.4.3 Utah’s Request to Adjustment the NWF NAA Boundary
On February 27, 2023, Governor Spencer J. Cox submitted a letter13 and supporting
documentation14 to EPA Region 8 administrator Kathleen Becker. In this letter, Governor Cox used his
authority under Section 107(d)(3)(D) of the CAA to request an adjustment to the existing NWF NAA
boundary (figure 1). The requested modification would extend the western edge of the existing
boundary in Tooele County 7.6 miles further west. This adjustment would result in the inclusion of US

12 Determinations of Attainment by the Attainment Date, Extensions of the Attainment Date, and Reclassification of Areas Classif ied as Marginal for the 2015 Ozone
National Ambient Air Quality Standards, 87 Fed. Reg. 60,897 (Oct. 7, 2022).
13 Utah’s Request for Boundary Adjustment for the Northern Wasatch Front NAA. Feb. 27, 2023: https://documents.deq.utah.gov/air -quality/planning/DAQ-2023-
002065.pdf
14 Request for Adjustment of the Northern Wasatch Front NAA Boundary for the 2015 8-hour Ozone National Ambient Air Quality Standard. Feb. 27, 2023:
https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-002086.pdf

Ozone Summary
Site ID Site Name County Annual 4th Highest
(ppm)
Three Year Average (ppm)
2018 2019 2020 2018-2020
49-057-1003 Harrisville Weber 0.077 0.064 0.074 0.071
49-011-0004 Bountiful Davis 0.080 0.073 0.080 0.077
49-035-2005 Copperview Salt Lake 0.079 0.067 0.075 0.073
49-035-3006 Hawthorne Salt Lake 0.074 0.073 0.075 0.074
49-035-3010 Rose Park Salt Lake 0.080 0.071 0.080 0.077
49-035-3013 Herriman Salt Lake 0.078 0.070 0.073 0.073
49-045-0004 Erda Tooele 0.074 0.065 0.070 0.069

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15

Magnesium LLC (section 4.15) into the NWF NAA. US Magnesium’s Rowley plant is currently one of the
largest point sources of VOCs and NOx in the greater Wasatch Front. US Magnesium is also a unique
source of halogen emissions which have been shown to impact both summer and wintertime pollution.15
Upon the receipt of the letter, EPA has 18 months to either approve or deny the state’s request. EPA has
not formally acted on this request and thus the extent of the NWF NAA remains as described in section
1.4.3 (Figure 1). However, given the magnitude of emissions from US Magnesium LLC, and their impacts
on the NWF NAA, the Utah Division of Air Quality (UDAQ) has included US Magnesium LLC in this SIP
revision where it is appropriate.
1.5 Responsible Air Agencies
1.5.1 Utah Division of Air Quality (UDAQ)
Section 19-2-104 of the Utah Code gives the Utah Air Quality Board the authority to promulgate
rules “regarding the control, abatement, and prevention of air pollution from all sources and the
establishment of the maximum quantity of air pollutants that may be emitted by an air pollutant
source.”16 The UDAQ develops, prepares, and submits SIPs to the Utah Air Quality Board for
consideration and promulgation. UDAQ is the primary state agency responsible for the development and
implementation of SIPs once they are approved by the Utah Air Quality Board, and associated
administrative rules, as required by the CAA.
1.5.2 Interagency Consultation Team
UDAQ works in close coordination with local Metropolitan Planning Organizations (MPOs) on
relevant traffic and travel-related aspects of SIP and transportation conformity activities. The
Interagency Consultation Team17 (ICT) is a group of MPOs and transportation planning agencies, that
undertake the interagency consultation process as it relates to the development of the SIP, applicable
control measures related to transportation included in the SIP, transportation plans, the Transportation
Improvement Program (TIP), and Transportation Conformity determinations. Within the NWF NAA, the
Wasatch Front Regional Council (WFRC) serves as the MPO for Box Elder, Davis, Salt Lake, Tooele, and
Weber Counties. The Utah Department of Transportation (UDOT), Federal Highway Transportation
Administration, Federal Transit Administration, and the EPA, are all part of the ICT as well.
1.6 Moderate SIP Elements
As part of the reclassification to a moderate NAA, EPA has required that Utah submit a SIP
revision.18 A moderate SIP revision requires mandatory planning elements per CAA section 182(b) which
are outlined in the final SIP Requirements Rule as well as in Table 3.19

15 Womack CC, Chace WS, Wang S, Baasandorj M, Fibiger DL, Franchin A, Goldberger L, Harkins C, Jo DS, Lee BH, Lin JC, McDonald B C, McDuffie EE, Middlebrook
AM, Moravek A, Murphy JG, Neuman JA, Thornton JA, Veres PR, Brown SS. Midlatitude Ozone Depletion and Air Quality Impacts from Industrial Halogen Emissions
in the Great Salt Lake Basin. Environ Sci Technol. 2023 Feb 7;57(5):1870-1881. doi: 10.1021/acs.est.2c05376. Epub 2023 Jan 25. PMID: 36695819.
16 Utah Code Ann. § 19-2-104(1)(a).
17 Utah State Implementation Plan Section XII; Transportation Conformity Consultation (May 2, 2007), available at https://documents.deq.utah.gov/legacy/laws-
and-rules/air-quality/sip/docs/2007/05May/SECXII.PDF
18 87 Fed. Reg. 60,897.
19 Implementation of the 2008 National Ambient Air Quality Standards for Ozone: NAA Classifications Approach, Attainment Deadlines and Revocation of th e 1997
Ozone Standards for Transportation Conformity Purposes, 77 Fed. Reg. 30,160 (May 21, 2012).

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16

Table 3: SIP Requirements
Category Requirement Reference Addressed in Section
Reasonable
Further Progress
(RFP)
Demonstrate a 15% reduction of
VOCs from the base year inventory to
the attainment year.
CAA
§182(b)(1)(A)(i)
and 40 CFR
§51.1310
Chapter 7 (IX D.11)
Base Year and
Projected
Emission
Inventories
Establish the base year emission
inventory (2017) and attainment year
inventory (2023) for use in
establishing RFP and demonstration
of attainment.
CAA
§182(b)(1)(B) and
40 CFR §51.1315
Chapter 3 (IX D.11)
Attainment
Demonstration
Demonstration that the NAA will
attain the standard using a
photochemical model and methods
approved in EPA modeling guidance.
CAA §182(c)(2)(A)
and 40 CFR
§51.1308
Chapter 8 (IX D.11)
Reasonable
Available Control
Technology
(RACT)
Evaluation of the application of
reasonable control technology
(technically and economically
feasible) at major sources.
CAA §182(b)(2)
and 40 CFR
§51.1312
Chapter 4 (IX D.11)
Reasonable
Available Control
Measure (RACM)
Evaluation of application of RACM for
all other sources of ozone precursors.
CAA §182(b)(2)
and 40 CFR
§51.1312
Chapter 5 (IX D.11)
Motor Vehicle
Inspection and
Maintenance
(I/M) Program
Evaluate if current I/M program
meets CAA requirements. CAA §182(b)(4) Chapter 6 (IX D.11)
Nonattainment
New Source
Review (NNSR)
Program
General offsets for VOCs shall be a
ratio of at least 1.15 to 1.0.
CAA §182(b)(5)
and 40 CFR
§51.1314
Chapter 4 (IX D.11)
Contingency
Measures
Emission reduction measure triggered
if the NAA fails to attain the standard
by the attainment date.
CAA §182(c)(9) Chapter 11 (IX D.11)

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17

Motor Vehicle
Emission Budgets
Establishment of maximum allowable
emissions from on-road mobile sector
for ozone precursor emissions used in
transportation conformity analysis.
CAA §182(c)(5) Chapter 10 (IX D.11)
1.7 Moderate Area SIP Development Process
UDAQ led the development of the moderate SIP and coordinated with the MPOs and EPA on the
development of the various SIP elements. Work began in September 2019 in anticipation of the
reclassification of the area from marginal to moderate status. Throughout the SIP development, public
stakeholder meetings were held to solicit comment and engagement from interested parties as detailed
in Chapter 10 of this SIP revision. The UDAQ holds regular bi-monthly meetings with both industry
representatives and environmental advocates. These meetings provide the opportunity to maintain
open dialogue and transparency in the development of a SIP with interested parties. Once aspects of the
SIP were developed to the point where they could be shared, UDAQ scheduled public outreach meetings
to present data and information to the public, and the public was provided with the opportunity to
comment or make suggestions. UDAQ also posted all documents related to the development of this SIP
revision, including all technical supporting documentation, to its public webpage20 as soon as they
became available.

20 https://deq.utah.gov/air-quality/northern-wasatch-front-moderate-ozone-sip-technical-support-documentation#supporting-tsd

UTAH DIVISION OF AIR QUALITY
18

Chapter 2 – NWF Monitoring Network
2.1 Monitoring Network
The UDAQ maintains a highly reliable, continuous near-surface ambient air monitoring network
that meets the requirements of 40 CFR Parts 50, 53, and 58.21 The 1970 CAA and subsequent
amendments provide the framework for an ambient air monitoring network that is designed to collect
data addressing five basic needs to:

1. Activate emergency control procedures that prevent or alleviate air pollution episodes.
2. Provide air pollution data to the public in a timely manner.
3. Judge compliance with and progress towards meeting ambient air quality standards.
4. Observe pollution trends throughout the region, including non-urban areas.
5. Provide a database for research evaluation of the following effects: urban, land-use, transportation
planning, development and evaluation of abatement strategies, and development and validation of
diffusion models.

The UDAQ collects monitoring data for five NAAQS criteria pollutants including: sulfur dioxide
(SO2), CO, ozone (O3), nitrogen dioxide (NO2) and particulate matter (PM10 and PM2.5). In addition, UDAQ
currently operates one continuous gas chromatograph for the collection and analysis of ozone precursor
data for the Photochemical Assessment Monitoring Station (PAMS) program. Each year, a network
review is performed by staff and the Annual Monitoring Network Plan is submitted as a separate
document to EPA Region 8 for approval. In addition, Utah has established a comprehensive
meteorological monitoring network to supply data for modeling activities, including measurements of
temperature, relative humidity, wind speed, and wind direction.
As part of the air monitoring network, the UDAQ specifically operates an extensive network of
ground level in-situ ambient air quality monitoring stations throughout the NWF NAA. The network
consists of eight active sites that monitor atmospheric concentrations of ozone that are used for
regulatory purposes, as well as two historic sites which help provide context for the extent and length of
UDAQs monitoring network (Figure 2). Beyond the UDAQ operated network of sites, there are several
research grade ozone monitoring stations within the NAA boundary that are supported by UDAQ
including: The Red Butte Ozone Monitoring Network, the mobile based TRAX Air Quality Observation
Project platform and the Mobile Electric Bus Air Quality Monitoring Project. While these projects are not
regulatory and are not included in the EPA’s Air Quality System and determination of a DV for the NAA,
they significantly contribute to the understanding of transport, production, and the spatiotemporal
patterns of ozone throughout the NAA.

21 Title 40 Protection of the Environment, Chapter 1 Environmental Protection Agency, Subchapter C Air Programs, Part 50 Nationa l Primary and Secondary Ambient
Air Quality Standards, Part 53 Ambient Air Monitoring Reference and Equivalent Methods and Part 58 Ambient Air Quality Surveillanc e.

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19

Figure 2: Monitoring sites in the NWF NAA
The UDAQ currently operates one PAMS site at Hawthorne, located in Salt Lake County. The PAMS
program is a subset of the State or Local Air Monitoring Stations (SLAMS) network for enhanced
monitoring of ozone precursor chemicals at sites located in an area with a population over 1,000,000
and in areas of moderate and above nonattainment status. The PAMS program is designed with the
objective to produce an air quality database to be used to evaluate and refine ozone prediction models.
In addition, the program will assist to identify and quantify the ozone precursors and establish the
temporal patterns and associated meteorological conditions to assist and refine the control strategies.
UDAQ is measuring the following parameters at the PAMS required site:
• Carbonyls
• Meteorological parameters: ambient temperature, wind direction, wind speed, atmospheric
pressure, relative humidity, precipitation, mixing layer height, solar radiation, and UV radiation
• Speciated VOCs
• True NO2
• NO & NOy
• Ozone

UTAH DIVISION OF AIR QUALITY
20

Since significant portions of the NWF NAA overlap with the Salt Lake City PM2.5 NAA, the UDAQ
operates the PAMS site for the full calendar year to account for both wintertime PM2.5 and summertime
ozone seasons.
In order to meet the Enhanced Monitoring Plan (EMP) requirements for a moderate NAA the UDAQ
is developing an EMP in fulfillment of federal regulations, 40 CFR Part 58, Appendix D 5(h). These
regulations require that a state with any area designated moderate or above for the 8-hour ozone
standard, and any state within the Ozone Transport Region (OTR), develop, implement, and submit an
EMP for ozone to the regional EPA office two years following the effective date of a designation to a
classification of moderate or above. The EMP is intended to provide monitoring organizations the
flexibility to implement any additional monitoring beyond the minimum requirements for the SLAMS to
complement the needs of their area.
As part of UDAQ’s proposed EMP, UDAQ plans to expand PAMS monitoring beyond the existing site
at Hawthorne to include 5 additional sites throughout the NWF NAA. These sites will represent an array
of land use types and will be distributed to provide insight into the underlying atmospheric chemical
regimes present at a variety of locations.
2.2 Ozone Monitoring Data
Table 4 and Table 5 show the monitoring data for the past twelve years for the NWF ozone
monitoring sites. The MDA8, and the 3-year averages of the MDA8 at each site are shown, respectively.
A trend graph of data from 2002 – 2021 for the key sites in the NWF is presented in Figure 3.

Table 4: NWF MDA8 reported in ppm.
NWF NAA Ozone MDA8 (ppm)
Site ID AQS # 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
Bountiful BV 49-011-
0004
0.074 0.068 0.067 0.062* 0.074 0.073* 0.076 0.078 0.080 0.073 0.080 0.082
Copperview CV 49-035-
2005
--- --- --- --- --- --- --- --- 0.079* 0.067 0.075 0.086
Hawthorne HW 49-035-
3006
0.073 0.075 0.078 0.077 0.072 0.081 0.074 0.081 0.074 0.073 0.075 0.081
Rose Park RP 49-035-
3010
--- --- --- --- --- --- --- --- 0.080 0.071 0.080 0.079
Herriman H3 49-035-
3013
--- --- --- --- --- 0.074 0.076 0.078 0.078 0.070 0.073 0.087
Lake Park LP 49-035-
3014
--- --- --- --- --- --- --- --- --- --- 0.062* 0.082
Tech Center UT 49-035-
3015
--- --- --- --- --- --- --- --- --- 0.038* 0.071* 0.083
Near Road NR 49-035-
4002
--- --- --- --- --- --- --- --- --- 0.064 0.072 0.083
Tooele #3 T3 49-045-
0003
0.074 0.071 0.074 0.072 0.069 --- --- --- --- --- --- ---
Erda ED 49-045-
0004
--- --- --- --- --- 0.071* 0.072 0.077 0.074 0.065 0.070 0.075
Harrisville HV 49-057-
1003
0.070 0.074 0.076 0.073 0.070 0.074 0.073 0.073 0.077 0.064 0.074 0.077
Ogden O2 49-057-
0002
0.073 0.074 0.066 0.076 0.070 0.072 0.072 0.075 0.079 0.059* --- ---
* Indicates numbers that do not meet the data completeness requirements

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21

Table 5: NWF 8-Hour Ozone Three-Year Average 4th Maximum Ozone Values.
3-yr. Average MDA8 (ppm)
Site ID AQS
#
2010-
2012
2011-
2013
2012-
2014
2013-
2015
2014-
2016
2015-
2017
2016-
2018
2017-
2019
2018-
2020
2019-
2021
Bountiful BV 49-011-
0004 0.069 0.065* 0.067* 0.069* 0.074* 0.075* 0.078 0.077 0.077 0.078
Copperview CV 49-035-
2005 --- --- --- --- --- --- 0.079* 0.073* 0.073* 0.076*
Hawthorne HW 49-035-
3006 0.075* 0.076 0.075 0.076 0.075 0.078 0.076* 0.076 0.074 0.076
Rose Park RP 49-035-
3010 --- --- --- --- --- --- 0.08* 0.075* 0.077* 0.076*
Herriman H3 49-035-
3013 --- --- --- 0.074 0.075 0.076 0.077 0.075 0.073 0.076
Lake Park LP 49-035-
3014 --- --- --- --- --- --- --- --- --- ---
Tech Center UT 49-035-
3015 --- --- --- --- --- --- --- --- --- 0.064*
Near Road NR 49-035-
4002 --- --- --- --- --- --- --- --- --- 0.073*
Tooele #3 T3 49-045-
0003 0.073 0.072 0.071 0.07 --- --- --- --- --- ---
Erda ED 49-045-
0004 --- --- --- 0.071* 0.071* 0.073* 0.074 0.072 0.069 0.07
Harrisville HV 49-057-
1003 0.073 0.074 0.073 0.072 0.072 0.073 0.074 0.071 0.071 0.071
Ogden O2 49-057-
0002 0.071 0.072 0.07 0.072 0.071 0.073 0.075 0.071* --- ---
* Indicates numbers that do not meet the data completeness requirements

UTAH DIVISION OF AIR QUALITY
22

Figure 3: MDA8 in Wasatch Front
As shown in Figure 3, the combined state air agency and federal regulatory actions have been
successful at reducing ozone values in the NWF. However, the area is still experiencing exceedances of
the ozone standard at all regulatory air monitors within the NAA. Ozone represents a unique challenge
in the Intermountain West. Despite years of success in reducing precursor emissions of NOX and VOCs,
the region still faces significant and unique challenges in meeting ambient ozone concentration health-
based standards. These regionally specific challenges include significantly elevated background ozone
levels,22 increasing instances and contributions of emissions from wildfire events,23 significant biogenic
contributions,24 as well as both interstate and international25 transport.
2.3 Data Quality Assurance
The primary purpose of UDAQ’s ambient air monitoring network is to determine whether the
area is meeting the criteria pollutant NAAQS. Other purposes for air monitoring include, but are not
limited to, determining the impact of sources on air quality, establishing background concentrations,
and determining the extent of regional ozone transport. The goal of UDAQ’s Air Monitoring Section is to

22 Scientific Assessment of background ozone over the U.S.: Implications for air quality management
23 Influence of Fires on O3 Concentrations in the Western U.S.; Dan Jaffe, Duli Chand, Will Hafner, Anthony Westerling, and Dominick Spracklen; Environment al
Science & Technology 2008 42 (16), 5885-5891. DOI: 10.1021/es800084k
24 EPA Webinar; Description and preliminary evaluation of BELD 6 and BEIS 4. ORD. Jesse O. Bash and Jeff Vukovich
25 Entrainment of stratospheric air and Asian pollution by the convective boundary layer in the southwestern U.S.; Langford, A.O . et al. (2017), J. Geophysics. Res.
Atmos., 122, 1312-1337, doi:10.1002/2016JD025987

UTAH DIVISION OF AIR QUALITY
23

produce data that are complete, comparable, representative, precise, and accurate in accordance with
40 CFR Part 58, Appendix A. Data quality is calculated at least annually according to EPA’s accepted
statistical procedures to determine compliance with the recommended limits. Data outside these limits
are still reported to Air Quality System (AQS), but UDAQ flags the data internally and attempts to
determine the source of the problems. The UDAQ Air Monitoring Quality Assurance Program Plan
provides details of how UDAQ meets the requirements of 40 CFR Part 58, Appendix A and is made
available to the public for review.26
Table 6 shows the data recovery rates for each monitoring site in the NWF NAA as a percentage.
The percent of data recovery is the number of valid sampling hours occurring within the ozone season
divided by the total number of hours encompassing the ozone season. The ozone season for Utah was
defined as from January 1 to December 31, thus is year-round.27 A valid sampling day is one in which at
least 75% of the hourly averages are recorded.

Table 6: NWF Ozone Data Recovery Rates shown as percentages.
Site 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
Bountiful
49-011-0004
99% 97% 98% 64% 99% 53% 100% 99% 99% 98% 99% 99%
Copperview
49-035-2005
--- --- --- --- --- --- --- --- 96% 93% 98% 97%
Hawthorne
49-035-3006
99% 97% 98% 64% 99% 53% 100% 99% 99% 98% 99% 96%
Rose Park
49-035-3010
--- --- --- --- --- --- --- --- 87% 80% 98% 99%
Herriman
49-035-3013
--- --- --- --- --- 100% 98% 98% 97% 99% 99% 98%
Lake Park
49-035-3014
--- --- --- --- --- --- --- --- --- --- 99% 98%
Tech Center
49-035-3015
--- --- --- --- --- --- --- --- --- 99% 99% 98%
Near Road --- --- --- --- --- --- --- --- --- 99% 98% 99%
Tooele
49-045-0003
64% 98% 99% 100% 99% 100% 83% 83% 97% 99% 92% ---
Erda
49-045-0004
--- --- --- --- --- 61% 100% 99% 93% 97% 99% 99%
Harrisville
49-057-1003
83% 99% 98% 99% 100% 96% 99% 89% 99% 82% 98% 96%
Ogden
49-057-0002
98% 94% 96% 99% 100% 100% 99% 99% 99% 99% --- ---

As shown in Table 6, the UDAQ monitoring program is extremely robust with a consistently high
level of data recovery. On an annual basis, the monitoring network is evaluated, assessed, and adjusted
as necessary to ensure that the agency and the public have an accurate understanding of local air quality

26 https://documents.deq.utah.gov/air-quality/planning/air-monitoring/DAQ-2022-007189.pdf
27 83 FR 25776

UTAH DIVISION OF AIR QUALITY
24

concentrations and trends. What these monitoring values represent and how they are impacted will be
evaluated and discussed in other SIP chapters.

UTAH DIVISION OF AIR QUALITY
25

Chapter 3 - Baseline and Future Year Emission Inventories
3.1 Emission Inventory Background
3.1.1 2017 Base Year Inventory
In accordance with the CAA and 40 CFR §51.1315, when the NWF was designated as a marginal
ozone NAA, the UDAQ was required to submit a base year emission inventory 24 months after the
effective date of designation. A base year inventory is comprised of a comprehensive, accurate, current
inventory of actual emissions from sources of VOCs and NOX emitted within the boundaries of the NAA
as required by CAA Section 182(a)(1). The base year for this SIP submittal is 2017, which is the most
recent calendar year for which a complete triennial inventory was submitted to the EPA. The inventory
is compiled in ozone season day emissions, which is an average day’s emissions for a typical ozone
season work weekday. This requirement was met and approved by EPA in 86 FR 35404, on July 6, 2021.
As a result of being reclassified as a moderate ozone NAA, the 2017 base year inventory is being
resubmitted as part of this NWF moderate SIP as some refinements have been made since the submittal
of the marginal base year inventory. The methodology for each inventory source category will be
provided in this chapter, with a more detailed description provided in the technical support document
(TSD) for this SIP.
3.1.2 2023 Projected Year Inventory
To support the CAA requirement for a moderate NAA to demonstrate RFP towards attainment,
UDAQ has developed a projected emission inventory for 2023 based on the base year inventory
described in Section 3.1.1. 2023 is the year prior to the required attainment date of August 3, 2024, thus
the state is required to demonstrate a 15% reduction in VOCs between 2017 and 2023 in accordance
with 40 CFR § 51.1310. The emission inventory presented here represents the projected inventory for
sources with no additional emission controls implemented beyond actions taken under the PM2.5 SIPs. A
discussion of proposed or potential emission controls and how they will help achieve the required VOC
reductions and demonstration of attainment will be discussed in Chapter 7, RFP. This chapter provides
the methodology and results of developing the baseline and future year inventories in accordance with
available EPA guidance.28
3.2 Baseline 2017 Emission Inventory a nd Projected 2023 Emission Inventory
Both inventories developed for the SIP are reported as an average day’s emissions for a typical
ozone season work weekday, in the unit of tons per day (tpd). This is an average summer day for the
NWF. The 2017 inventory of actual emissions is the basis for any projections made to represent future
years. Emission inventories are generally collected and reported as annual emissions. These annual
inventories are processed through the Sparse Matrix Operating Kernel Emissions Model (SMOKE).29
SMOKE modeling spatially allocates, temporalizes, and chemically speciates annual emissions
estimations from the emissions inventories. Post-SMOKE, annual emissions are temporalized and can be
represented in tons per day. Spatial allocation, temporalization, and chemical speciation are SCC-specific
operations. UDAQ typically tabulates emissions from area and mobile sources on a county-by-county

28 SMOKE Technical Support Documentation for NWF SIP Attainment Demonstration; https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001603.pdf
29 SMOKE Technical Support Documentation for NWF SIP Attainment Demonstration; https://documents.deq.utah.gov/air -quality/planning/DAQ-2023-001603.pdf

UTAH DIVISION OF AIR QUALITY
26

basis, however the NAA includes two partial counties. To obtain the typical ozone season day, emission
inventories are entered into the SMOKE model such that it is assigned a geographic location (grid cell).
To report emissions specific to the NAA, UDAQ cropped the post-SMOKE processed gridded emissions
using a Geographic Information System (GIS) tool using polygons representing the boundaries of the
NAA.
An inventory of emissions was developed for the major source categories as presented in Table
7 for the 2017 emission inventory. Residential wood combustion is excluded as this source is not a
significant emitter of ozone precursors when compared to more predominant sources in the NAA and is
not seasonally relevant to summertime ozone production in the NWF. More detailed post-SMOKE
emissions inventory tables can be found in the SMOKE TSD.30

Table 7: 2017 Nonattainment Emission Inventory (tons per day)
NWF NAA 2017 base year
Sector NOx TPD VOC TPD
Solvents 0.56 43.20
Area (non-point) 5.36 8.51
Livestock

0.69
Non-road 10.52 12.53
Rail 9.25 0.47
Airports 3.14 1.25
Electric Generating Units (EGUs) 0.44 0.03
Point Sources 20.43 5.85
On-road Mobile 55.53 20.47
ERC Bank 3.1 0.7
TOTAL ANTHROPOGENIC 108.33 93.7

The projection year emissions inventory was prepared for 2023 as this is the year prior to the
attainment date of August 3, 2024. The emission projections reflect changes due to growth and existing
controls. The 2023 emission inventories presented here do not account for controls put in place
specifically from actions taken for this SIP.

30 SMOKE Technical Support Documentation for NWF SIP Attainment Demonstration; https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001603.pdf

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27

Table 8: 2023 Projected Nonattainment Emission Inventory (tpd)
NWF NAA 2023 future year
Sector NOX TPD VOC TPD
Solvents 0.71 44.52
Area (non-point) 4.85 8.26
Livestock

0.71
Non-road 8.05 12.62
Rail 8.77 0.44
Airports 3.74 1.42
Electric Generating Units (EGUs) 0.45 0.03
Point Sources 22.00 6.00
On-road Mobile 35.40 15.32
ERC Bank 3.1 0.7
TOTAL ANTHROPOGENIC 87.07 90.02
3.2.1 Fires and Biogenic Sources
Emissions from wildland and prescribed fires, and biogenic sources, which are dependent on
meteorological conditions, are accounted for during the modeling phase and are not traditionally
inventoried.31 Emissions from wildfires are accounted for using the Blue-Sky Framework in the SMOKE
model. Biogenic emissions are modeled with the Biogenic Emissions Inventory System (BEIS) version
3.6.1. BEIS creates gridded, hourly, model-species emissions from vegetation and soils. Forests are
significant sources of VOCs, and the burning of forest material is a source of ozone precursors and
particulate matter. These source categories are crucial to include in any ozone modeling demonstration.
The emissions from biogenic sources are shown in Table 9 and are held constant between 2017 and
2023.

Table 9: Biogenic Emissions (tons per day)
NWF NAA COUNTIES (includes all of Tooele and Weber Counties) 2017 base year
Sector NO TPD VOC TPD
TOTAL NAA COUNTY-WIDE BIOGENIC 5.57 246.88
3.2.2 Solvent Emissions
The solvents sector includes VOC emissions from everyday items such as cleaners, personal care
products, adhesives, architectural and aerosol coatings, printing inks, asphalt, and pesticides. Emissions
estimates were sourced from EPA’s 2016v2 platform, which were generated with the VCPy framework.
EPA’s 2017 platform predates EPA’s 2016v2 platform, and it does not include emissions from solvents
according to the VCPy framework. The VCPy framework features better VOC emissions estimates than
previous platforms, thus UDAQ made every effort to include improved emissions in the solvents
inventory.32 Since EPA’s 2016 modeling base year did not align with the NWF SIP 2017 base year, the
inventory was projected to 2017. The only relation expected to change between 2016 and 2017 base
years is the mass of chemical products used. To determine a change in product used, UDAQ evaluated

31 SMOKE Technical Support Documentation for NWF SIP Attainment Demonstration; https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001603.pdf
32 SMOKE Technical Support Documentation for NWF SIP Attainment Demonstration; https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001603.pdf

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the average Producer Price Index (PPI) across the summer months represented during our modeling
episode: June, July, and August. In 2016, the average summer PPI for all commodities was 187.3. In 2017
the PPI was 193.6. This shows a 3% increase in PPI from 2016 to 2017, so all solvents emissions from the
2016v2 platform VCPy inventory were increased by 3% to produce the 2017 base year VCPy inventory
used in this modeling demonstration. The 2016v2 platform includes projected emissions inventories for
2023 that were utilized by UDAQ. Table 10 and Table 11 provide the 2017 baseline inventory for
solvents and the projected 2023 inventory respectively.
Emissions from hot mix asphalt (HMA) plants are submitted as point source inventories,
however, all HMA plants in the NAA have 2017 NOx and/or VOC emissions less than 100 tons per year
(tpy). Point sources with NOx and/or VOC emissions less than 100 tpy are assumed to be represented in
nonpoint sectors, but emissions from asphalt plants are technically not represented in the solvents or
nonpoint sectors. To accommodate planned rulemaking, UDAQ added emissions from HMA plants to
the solvents sector. It is important to note that the emissions associated with HMA facilities discussed in
this section represent UDAQ’s best assumptions for actual annual emissions associated with the
production of HMA products based on known metrics like annual production. Elsewhere in this SIP
revision emissions may be reported based on the combined potential to emit based on permitted
maximums from all HMA facilities, and thus represent the upper bounds of potential emissions from
HMA facilities.

Table 10: Solvent Emissions Inventory
NWF NAA 2017 base year
Sector NOX TPD VOC TPD
Solvents 0.56 43.20
Consumer Products - 18.23
HMA plants 0.56 0.06
Other Solvents - 24.91

Table 11: 2023 Solvent Emissions Inventory
NWF NAA 2023 future year
Sector NOX TPD VOC TPD
Solvents 0.71 44.52
Consumer Products - 18.80
HMA plants 0.71 0.11
Other Solvents - 25.62
3.2.3 Area Sources
Nonpoint (area) sources are typically smaller, yet pervasive sources that do not qualify as point
sources under the relevant emissions cutoffs. Area sources encompass more widespread sources that
may be abundant, but that, individually, release small amounts of a given pollutant. These are sources
for which emissions are estimated as a group rather than individually. Examples typically include
residential heating and residential charcoal grilling. Area sources generally are not required to submit
individual emissions estimates, and instead are reported as county totals.
Area source calculation methods are consistent with Utah’s methods for reporting the EPA’s tri-
annual National Emissions Inventory. Area source emissions are calculated based on activity data, which

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29

is gathered from sources such as Departments of Transportation, State Tax Commissions, State Data
Centers, State Offices of Planning and Budget, State Energy Commissions, federal agencies such as the
U.S. Census Bureau, county and local government agencies, airports, natural gas suppliers, and local
trade associations. These data include population, employment, vehicle miles traveled (VMT), fuel
usage, animal, crop, and other estimates. Area source calculations are often based on combining these
activity data with emission factors. Emission factors were also gathered from similar sources, mostly EPA
documents. Area sources were adjusted for potential overlaps and double counts with point sources.33
Emission projections for 2023 were based on 2017 data and projected forward. Projection
methods were consistent with methods used in past Utah SIPs. Emission projections were based on
activity data, similar to their baseline estimates. Depending on the specific source, emissions were
projected to scale with population, manufacturing, agricultural, employment data, Energy Information
Agency energy use projections, VMT, and other similar data sources.
Livestock emissions were calculated using EPA generated emission factors for livestock animals
and multiplying them by the respective livestock populations for each county. Future emissions were
forecast using a linear regression model to predict future year livestock emissions as based on
agricultural employment.

Table 12: 2017 Area Source Emission Inventory
NWF NAA 2017 base year
Sector NOX TPD VOC TPD
Livestock - 0.69
Nonpoint 5.36 8.51
2 - 5 MMBTU boilers 0.91 0.05
Other Nonpoint Sources 4.45 8.46

Table 13: Area Source Emission Inventory
NWF NAA 2023 future year
Sector NOX TPD VOC TPD
Livestock - 0.71
Nonpoint 4.85 8.26
2 - 5 MMBTU boilers 0.87 0.05
Other Nonpoint Sources 3.99 8.21
3.2.4 Non-Road, Rail, and Airport Sources
EPA’s Motor Vehicle Emission Simulator (MOVES3) model was used to obtain emission
inventories for non-road mobile vehicles and equipment that operate on unpaved roads and other areas
but not on paved roads.34 They include non-road engines and equipment, such as lawn and garden
equipment, construction equipment, engines used in recreational activities, portable industrial,
commercial, and agricultural engines. Emissions from MOVES3 for the month of July are input to SMOKE
to obtain the typical ozone season day value.

33 Area Source Inventories; https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001348.pdf
34 2017 BASELINE, EPISODIC AND 2023 PROJECTION OZONE EMISSIONS INVENTORY NON-ROAD MOBILE SOURCE; https://documents.deq.utah.gov/air-
quality/planning/DAQ-2023-001585.pdf

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30

Emissions from snow blowers and snowmobiles have been removed from the non-road sector,
assuming that these emissions are zero during the summertime modeling episode. Emissions from
pleasure craft (personal watercraft and recreational boats with outboard or inboard/sterndrive motors)
are allocated to counties according to the number of watercraft registrations in each county. However,
along the Wasatch Front, personal watercraft is not operated in the county of residence. Bodies of
water on which pleasure craft may be operated exist in mainly rural counties beyond the urban corridor
of the Wasatch Front. Assuming that pleasure craft owners transport their recreational vehicles to use
them, UDAQ removes any pleasure craft emissions from Salt Lake, Davis, Weber, and Tooele counties.
These four counties do not include any bodies of water on which pleasure craft may be operated. 35
Emissions in the airports sector include all emissions from aircraft and associated ground
support equipment. UDAQ’s platform base year airport emissions are sourced from EPA’s 2017 platform
within Utah, and from EPA’s 2016v2 platform outside Utah. All future year 2023 emissions were copied
from EPA’s 2016v2 platform future year emissions inventories (2023). Rail emissions within the state of
Utah include all locomotives, railway maintenance locomotives, and point source yard locomotives.36

Table 14: Non-Road, Rail and Airports Emission Inventory
NWF NAA 2017 base year
Sector NOx TPD VOC TPD
Non-road 10.52 12.53
2-stoke Lawn/garden Equipment 0.11 3.33
Other Lawn/garden Equipment 1.48 4.35
Other Non-road Sources 8.94 4.86
Rail 9.25 0.47
Airports 3.14 1.25

Table 15: 2023 Non-Road, Rail and Airports Emission Inventory
NWF NAA 2023 future year
Sector NOx TPD VOC TPD
Non-road 8.05 12.62
2-stoke Lawn/garden Equipment 0.12 3.63
Other Lawn/garden Equipment 1.46 4.42
Other Non-road Sources 6.47 4.57
Rail 8.77 0.44
Airports 3.74 1.42
3.2.5 Point Sources and Electric Generating Units (EGUs)
The definition of a Type B Source under Title V of the CAA (as specified in 40 CFR Appendix A to
Subpart A of Part 51) includes point source thresholds in the NAA. This definition includes all facilities
with the potential to emit 100 tpy or more of VOC or NOX. Emissions from sources under the Type B
thresholds are included in the area source baseline inventory, as they do not have large enough

35 SMOKE Technical Support Documentation for NWF SIP Attainment Demonstration; https://documents.deq.utah.gov/air -quality/planning/DAQ-2023-001603.pdf
36 SMOKE Technical Support Documentation for NWF SIP Attainment Demonstration; https://documents.deq.ut ah.gov/air-quality/planning/DAQ-2023-001603.pdf

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potential emissions to qualify for the point source inventory. According to the Type B Source definition,
Utah had 53 major point sources of NOx and VOC in 2017, 12 of which are located in the NWF NAA.
UDAQ has improved emissions inventory data management with the implementation of the
State and Local Emissions Inventory System (SLEIS). This system has established an online emissions
inventory system, whereby point sources can submit their air emissions inventories to UDAQ. SLEIS
includes built-in calculation capabilities which simplify the process and reduce the workload for point
sources. SLEIS also contains extensive Quality Assurance and Quality Control (QA/QC) tools which guide
point sources as they submit their data, thereby greatly reducing oversight required by UDAQ staff. The
2017 triannual emissions inventory was submitted to UDAQ by point sources using the SLEIS online
system. The submitted emissions inventories were thoroughly reviewed using additional QA/QC by
UDAQ staff before being finalized. The QA/QC contained in the SLEIS online system along with the
review performed by UDAQ staff greatly surpasses EPA guidance requiring 10% QA/QC as the minimum
criteria necessary for a SIP inventory.
The 2017-point source emissions inventory was used for the baseline emissions inventory for
the SIP.37 Point source emissions were represented as the actual emissions from the 2017 triannual
emissions inventory which coincides with the most recent triannual inventory that has been compiled
and reviewed by UDAQ.
Point source emissions, as based on annual actual emissions, in the NAA and affecting the NWF
NAA was grown on a case-by-case basis for each source and represented in the ozone SIP workbooks for
2023. Emission estimates were projected to future years and to display any control technologies that
will be applied. Data from Kem C. Gardner Policy Institute County Projections were used for developing
projected emissions for all major point sources. 38 More information on how the Kem C. Gardner data
was used is found on page 3 of the 2023 Point Source TSD.
Point source operators provided a monthly percentage of annual emissions from January to
December as part of their emissions inventory submission, which was used to generate source-specific
monthly temporal profiles in SMOKE for point sources in Utah’s emissions inventory. Emissions
summaries are provided on a per-facility basis in the SMOKE TSD.39

Table 16: 2017 Point Sources and EGUs Emission Inventory
NWF NAA 2017 base year
Sector NOx TPD VOC TPD
EGUs 0.44 0.03
Point Sources 20.43 5.85
5+ MMBTU boilers 1.90 0.12
Other Point Sources 18.52 5.74

37 Base Year Ozone SIP Point Source Inventory; https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001356.pdf
38 Projected Ozone SIP Point Source Inventory; https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001361.pdf
39 SMOKE Technical Support Documentation for NWF SIP Attainment Demonstration; https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001603.pdf

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Table 17: 2023 Point Sources and EGUs Emission Inventory
NWF NAA 2023 future year
Sector NOx TPD VOC TPD
EGUs 0.45 0.03
Point Sources 22.00 6.00
5+ MMBTU boilers 1.48 0.14
Other Point Sources 20.52 5.86
3.2.6 On-Road Mobile
On-road mobile source emissions include vehicles that travel on paved roads that produce
exhaust, evaporative, and road dust emissions. The on-road mobile inventory was compiled using Motor
Vehicle Emissions Simulator (MOVES3) according to the document “MOVES3 Technical Guidance: Using
MOVES to Prepare Emissions Inventories for SIPs and Transportation Conformity” November 2020. The
baseline year and projection year inventories was compiled through the ICT. The interagency
consultation team is primarily used to discuss and decide what MOVES modeling inputs should be used
with the SIP modeling domain. The ICT includes representatives from EPA, Federal Highway
Administration (FHWA), Federal Transit Authority, Utah Department of Transportation, Utah Transit
Authority, Wasatch Front Regional Council (WFRC), Mountainland Association of Governments (MAG),
Cache MPO, and UDAQ.40
On-road mobile source baseline and projection emission inventories are prepared for an
average ozone season weekday based on average hourly temperatures and relative humidity from 2017
July data. VMT were reported as an average ozone season day weekday.

Table 18: 2017 On-road emission inventory for ozone weekday
NWF NAA 2017 base year
Sector NOx TPD VOC TPD
On-road Mobile 55.53 20.47
Heavy Duty Vehicles 27.21 3.65
Light Duty Vehicles 28.32 16.82

Table 19: 2023 On-road emission inventory for ozone weekday
NWF NAA 2023 future year
Sector NOx TPD VOC TPD
On-road Mobile 35.40 15.32
Heavy Duty Vehicles 23.41 2.74
Light Duty Vehicles 11.98 12.58

40 2017 THE NORTHERN WASATCH FRONT, UT NONATTAINMENT OZONE AREA SUMMER BASELINE OZONE INVENTORY ON -ROAD TECHNICAL SUPPORT
DOCUMENTATION; https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001725.pdf & 2023 NORTHERN WASATCH FRONT, UT NONATTAINMENT
OZONE AREA SUMMER PROJECTION OZONE INVENTORY ON-ROAD TECHNICAL SUPPORT DOCUMENT; https://documents.deq.utah.gov/air-quality/planning/DAQ-
2023-001699.pdf

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3.2.7 Emission Reduction Credit Bank
The NAA has Emission Reduction Credit Bank (ERC) from past ozone SIP revisions that include
NOx and VOC credits available. Emission credit banks for VOCs and NOx were reviewed for the four NAA
counties. All banked credits were reviewed for validity concerning applicable emission credits meeting
2017 RACT or better for controlled or reduced emissions. Upon review, the majority of credits were
awarded as a result of a unit or facility closure or decommissioning. Credits are valid and remained in
the bank if the applicable change was RACT or better. These credits are available in the ERC offset bank
moving forward and were included in the ERC portion of both the baseline and projected year
inventories to represent all potential emissions within the NAA boundary.41

Table 20: 2017 ERC Bank Emission Inventory
NWF NAA 2017 base year
Sector NOx TPD VOC TPD
ERC Bank 3.10 0.70

Table 21: 2023 ERC Bank Emission Inventory
NWF NAA 2023 future year
Sector NOx TPD VOC TPD
ERC Bank 3.10 0.70

41 SMOKE Technical Support Documentation for NWF SIP Attainment Demonstration; https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001603.pdf

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Chapter 4 – Reasonably Available Control Technology (RACT) Analysis
and Nonattainment New Source Review (NNSR)
4.1 Reasonably Available Control Technology (RACT) Overview
Under the CAA 182(b)(2), all areas designated moderate nonattainment for the 2015 8-hour
ozone NAAQS are required to implement RACT for all existing major sources of VOCs or NOx that emit
100 tpy of either pollutant, as well as all VOC sources subject to an EPA Control Technique Guideline
(CTG).
CTGs are documents issued by the EPA to provide states with recommendations on how to
control VOC emissions from specific sources or products in an ozone NAA. When determining what is
RACT, in addition to existing CTGs and alternative control techniques (ACTs), states should consider, “all
relevant information (including recent technical information and information submitted by the public)
that is available at the time they develop the RACT SIPs.”42. “States may require VOC and NOX reductions
that are “beyond RACT" if such reductions are needed to provide for timely attainment of the ozone
NAAQS.”43
A RACT analysis identifies controls that could be implemented at the lowest emission limitation
that a source is capable of meeting by the application of a control technology that is reasonably
available, considering technological and economic feasibility.44 Implementation of controls identified
under the RACT process must be implemented by January 1, 2023, for emission reductions to be
creditable towards RFP requirements (section 7).45 A RACT analysis must include the latest information
when evaluating control technologies. Control technologies evaluated for a RACT analysis can range
from work practices to add-on controls. As part of the RACT analysis, current control technologies
already in use for VOCs or NOX sources can be taken into consideration. To conduct a RACT analysis, a
top-down analysis is used to rank all control technologies.
4.1.1 Top Down RACT Analysis Steps
For sources that meet or exceed the applicable emission thresholds, the following steps are
followed:
• Step 1. Identify all RACT options applicable to the source
• Step 2. Eliminate technically infeasible control technologies
• Step 3. Rank remaining control technologies based on capture and control efficiencies
• Step 4. Evaluate remaining control technologies based on economic, energy, and environmental
feasibility
• Step 5. Select RACT options

42 Implementation of the 2015 National Ambient Air Quality Standards for Ozone: NAA State Implementation Plan Requirements, 83 Fed. Reg. 62,998, 63,007 (Dec.
6, 2018).
43 Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State Implementation Plan Requirements, 80 Fed. Reg. 12,264, 12,279 (March 6,
2015).
44 40 CFR § 51.1312 Requirements for reasonably available control technology (RACT) and reasonably available control measures (RACM).
45 87 Fed. Reg. 60,897.

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35

All available control technologies must be included in a RACT analysis for all VOC and NOx
sources, with a thorough description and discussion of technological feasibility. Economic feasibility is
determined through Step 4 of a RACT analysis using EPA’s Air Pollution Control Cost Manual as
guidance.46
4.2 Utah RACT Process
The UDAQ relied on multiple available analyses when determining if sources within the NWF NAA
met RACT requirements, or if the implementation of additional RACT were required to demonstrate that
the NWF NAA will attain the standard at the earliest possible date. First, the UDAQ reviewed and
reconsidered control options submitted as part of the Salt Lake City, UT PM2.5 serious SIP, which
required the implementation of the more stringent Best Available Control Technologies (BACT) for both
NOx and VOCs.47 BACT relies on more restrictive emission control requirements than RACT, and thus
emission reduction strategies identified and implemented under BACT are more stringent than those
identified through the RACT process. Therefore, by reexamining past BACT analyses, the UDAQ relied on
a recently conducted analysis which implemented controls that conform to a higher economic and
technological standard. In doing so, the UDAQ is remaining consistent with guidance provided by the
EPA48, in which the EPA concludes that states may conclude a source has already addressed RACT based
on a RACT determination for a previous NAAQS SIP revision. For instance, the EPA proposes that in some
instances a RACT analysis submitted for the 1997 NAAQS are appropriate for meeting RACT
requirements for the 2008 NAAQS.49 In this example, states are granted the discretion to rely on a like-
for-like RACT analysis with a substantial time laps between respective SIP revisions under each NAAQS.
For this SIP revision, the UDAQ reexamined the more stringent BACT analyses submitted with a shorter
time lapse than that provided in the example, with BACT reports being submitted just 4 to 5 years
earlier.
In addition to reexamining past BACT reports, the UDAQ identified three emission sources that were
not evaluated as part of the PM2.5 serious SIP. Those analyses were provided to UDAQ by Tesoro
Refining and Marketing Company LLC50, Holly Energy Partners Woods Cross Terminal51, and Chevron Salt
Lake Marketing Terminal52. These three RACT reports were later included in facility wide updated RACT
analyses by each of the respective sources and therefore were analyzed in multiple rounds of RACT
analysis conducted as part of this SIP revision.
Beyond the past PM2.5 BACT reports, and three additional RACT reports submitted for review, the
UDAQ notified sources that they could opt-in to submitting an updated facility wide RACT analysis for
consideration in this SIP revision. Subsequently, 9 sources within the NAA provided UDAQ with new
RACT analyses for emissions of both VOCs and NOx. The UDAQ reviewed all analyses submitted in

46 EPA’s Air Pollution Control Cost Manual can be found at: https://www.epa.gov/sites/default/files/2020 -07/documents/c_allchs.pdf
47 Utah State Implementation Plan; Control Measures for Area and Point Sources, Fine Particulate Matter, Serious Area PM2.5 SIP for the Salt Lake City, Utah NAA;
Section IX. Part A.31: https://deq.utah.gov/air-quality/control-strategies-serious-area-pm2-5-sip
48 80 FR 12264 & 83 FR 62998
49 80 FR 12264 p.12278
50 The RACT analysis from the Tesoro Refinery and Marketing Company can be found at: https://documents.deq.utah.gov/air -quality/planning/air-quality-
policy/DAQ-2022-011275.pdf
51 The RACT analysis for the Holly Energy Partners Woods Cross Terminal can be found at: https://documents.deq.utah.gov/air-quality/planning/air-quality-
policy/DAQ-2022-011295.pdf
52 The RACT analysis for the Chevron Salt Lake Marketing Terminal can be found at: https://documents.deq.utah.gov/air -quality/planning/air-quality-policy/DAQ-
2022-011292.pdf

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36

conjunction with past BACT reports, and where warranted, requested updated RACT reports with
additional or clarifying information. All RACT analyses, and all follow-up reports, were made available for
public review at the earliest possible date53.
UDAQ determined that one major source located outside the NWF NAA impacts the ability of the
NAA to attain the NAAQS, and as such was required to provide a RACT analysis to UDAQ. This source, US
Magnesium, its RACT analysis, and identified control options, will be discussed in detail in Section 4.15.
4.2.1 Actual Emissions and Potential to Emit (PTE)
Utah Administrative Rule R307-101; General Requirements, contains the definitions for the
terms “Actual Emissions”, “Potential to Emit”, and “Enforceable”. Thus, the actual emissions of a source
refers to the actual rate of emissions of an air pollutant from an emissions unit. Actual emissions are
calculated using the unit’s actual operating hours, production rates, and types of materials processed,
stored, or combusted during the selected time period. The actual emissions of a source can fluctuate
from year-to-year due to changes in a source’s year-to-year operations.
The PTE of a source means the estimated maximum capacity of a source to emit an air pollutant
under its physical and operational design. A source’s PTE is not an enforceable limitation in itself, but is
instead the maximum amount of air pollutants a source could emit if each emission unit operated at
100% of its design capacity, 24 hours a day, 365 days a year. Any physical or operational limitation on
the capacity of a source to emit an air pollutant, including air pollution control equipment and
operational or process restrictions or limitations, are treated as part of a source’s design if the limitation
is enforceable.
Enforceable limitations and conditions include requirements developed pursuant to 40 CFR
Parts 60 and 61, requirements within the Utah SIP and Utah Administrative Rule Series R307, and any
permit requirements established pursuant to Utah Administrative Rule R307-401; Permit: New and
Modified Sources.
4.3 Big West Oil LLC - Refinery
4.3.1 Introduction
This section specifically serves as an evaluation of Big West Oil LLC – Big West Oil Refinery (Big
West). The UDAQ relied on past submitted BACT reports and an additional RACT analysis submitted by
Big West for evaluation on January 31, 2023; specific sections from this analysis are referenced in the
RACT analysis. Specific ozone SIP conditions for Big West can be found in Section IX, Part H.32.a.
4.3.2 Facility Process Summary
The Big West Oil Refinery is a petroleum refinery capable of processing 30,000 barrels per day of
crude oil. The source consists of a specific type of Fluidized Catalytic Cracking Unit (FCCU), a Millisecond
Catalytic Cracker (MSCC); catalytic reforming unit; hydrotreating units; and a sulfur recovery unit. The
source also has an assortment of heaters, boilers, cooling towers, storage tanks, flares, and fugitive
emissions.

53 https://deq.utah.gov/air-quality/northern-wasatch-front-moderate-ozone-sip-technical-support-documentation#supporting-tsd

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4.3.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from Big West processes and equipment are summarized in Table
22. The 2017 actual emissions were used as the baseline emissions. The current PTE values for Big West
were established by the most recent active Approval Orders (AOs) issued to the source. Big West
currently has several open AO modifications that will include updating their PTE to more accurately
reflect their operations.
• AO DAQE-AN101220077-22 issued January 13, 2022 (0077-22)
• AO DAQE-AN101220074-19 issued October 23, 2019 (0074-19)
• AO DAQE-AN101220072-19 issued July 10, 2019 (0072-19)
Table 22: Big West Oil LLC Refinery Facility-Wide Emissions
Big West Oil LLC Refinery Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 115.15 195.00
VOC 676.59 432.78
4.3.4 RACT Analysis
The RACT evaluations were performed using data from Big West Oil, AOs and supporting
documentation, and Utah SIP Section IX, Parts H.11 and H.12. Various resources were evaluated to
identify all existing and potential controls and emission rates, including EPA’s RBLC; technical
documents, EPA fact sheets, applicable CTGs, and other applicable literature; state and federal
regulations; and other state SIPS. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 23.

Table 23: Big West Oil LLC - Refinery
Big West Oil LLC - Refinery
RACT
Section
#54
Emission
Unit/Activity
Pollutant RACT
Determination
Enforceability Comments
AO
Conditions
PM2.5 SIP
Conditions
3.1 FCCU
(MSCC)
Regenerator
NOx Low-NOx
regeneration
with low-NOx
promoter
catalyst -
meets MACT
Subpart UUU.
(0077-22)
II.B.3.b
H.12.b.ii &
H.12.b.vi
Current operations
meet RACT, no further
action warranted.
VOCs Good
combustion
practices, no
(0077-22)
I.5
No

54 https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001493.pdf

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additional
controls.
3.2 -
3.4
Process
Heaters and
Boilers
NOx LNB & ULNB
required on
various units,
& refinery-
wide NOx limit.
(0077-22)
II.B.1.d &
II.B.8.d
H.12.b.ii &
H.12.b.vi
Current operations
meet RACT, no further
action warranted.
VOCs Good
combustion
practices, no
additional
controls.
(0077-22)
I.5
No
3.5 Refinery
Flares
NOx Evaluated
through
control of flare
gases, not
through
individual
pollutants,
requirement
to meet New
Source
Performance
Standards
(NSPS)
Subpart Ja and
MACT Subpart
CC for flares.
(0077-22)
II.B.4 &
II.B.7.c
H.11.g.v,
H.12.b.ii,
&
H.12.b.vi
Current operations
meet RACT, no further
action warranted.
VOCs
3.4 SRU NOx Existing tail
gas incinerator
& refinery-
wide NOx limit.
(0077-22)
II.B.8.d
H.12.b.ii &
H.12.b.vi
Current operations
meet RACT, no further
action warranted.
3.13 Cooling
Towers
VOCs MACT Subpart
CC
requirements
on cooling
towers
servicing high
VOC heat
exchangers.
(0077-22)
II.B.7.a
H.11.g.iii Current operations
meet RACT, no further
action warranted.
3.7 Fugitive
emissions
VOCs Low leak LDAR
requirements
of NSPS
Subpart GGGa.
(0077-22)
II.B.1.a &
II.B.7.b
H.11.g.iv Current operations
meet RACT, no further
action warranted.

UTAH DIVISION OF AIR QUALITY
39

3.10 &
3.11
Tanks VOCs Submerged fill
operations &
tank degassing
requirements -
eventual
compliance
with NSPS
Subpart Kb or
MACT Subpart
CC.
(0072-19)
II.B.1.a &
II.B.1.b
H.11.g.vi Current operations
meet RACT, no further
action warranted.
3.12 Wastewater
System
VOCs API separator
with fixed
cover, carbon
canisters for
VOC control,
90% removal
efficiency.
No H.12.b.vi Current operations
meet RACT, no further
action warranted.
3.6 Standby Fire
Pumps
VOCs Proper
maintenance
and operation,
and
compliance
with
applicable
NSPS or MACT
requirements.
(0074-19)
I.5
H.12.b.iv Current operations
meet RACT, no further
action warranted. NOx (0074-19)
II.B.1.c
3.8 Truck
Loading Rack
VOCs Vapor
recovery unit
with carbon
adsorption in
compliance
with MACT
Subpart CC.
(0077-22)
I.5
H.12.b.vi Current operations
meet RACT, no further
action warranted.
3.9 Railcar
Loading Rack
VOCs Vapor
recovery with
vapor
combustion
unit in
compliance
with MACT
Subpart R.
(0077-22)
I.5
H.12.b.vi Current operations
meet RACT, no further
action warranted.
N/A Refinery
General
Approach
NOx Refinery-wide
NOx limit.
(0077-22)
II.B.8.d
H.12.b.ii Current operations
meet RACT, no further
action warranted.

UTAH DIVISION OF AIR QUALITY
40

4.3.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emission limitations are considered RACT for the Big West Oil Refinery. RACT evaluations showed
that additional add-on controls or limitations are not technically or economically feasible options at this
time. No additional RACT measures were identified, and all RACT determinations are already being
implemented. Therefore, there are no additional implementation schedules or requirements for Big
West Oil Refinery as required by this SIP revision.
4.4 Chevron Products Company – Salt Lake Refinery
4.4.1 Introduction
This section specifically serves as an evaluation of Chevron Products Company – Salt Lake
Refinery (Chevron Refinery). In addition to its past submitted BACT reports, Chevron Refinery submitted
an additional RACT analysis for evaluation January 31, 2023, with supporting information submitted
February 23, 2023, and February 24, 2023; specific sections from this analysis are referenced in the
RACT analysis. Specific Ozone SIP conditions for Chevron Refinery can be found in Section IX, Part
H.32.b.
4.4.2 Facility Process Summary
The Chevron Refinery is a petroleum refinery with a nominal capacity of approximately 50,000
barrels per day of crude oil. The source consists of two FCCUs, a delayed coking unit, a catalytic
reforming unit, hydrotreating units, and two sulfur recovery units. The source also has an assortment of
heaters, boilers, cooling towers, storage tanks, flares, and fugitive emissions. The refinery operates with
a flare gas recovery system on its hydrocarbon flares.
4.4.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the Chevron Refinery processes and equipment are
summarized in Table 24. The 2017 baseline actual emissions were used as the baseline emissions. The
current PTE values for Chevron Refinery were established by the most recent active AOs issued to the
source.
• AO DAQE-AN101190106-22 issued August 24, 2022 (0106-22)
• AO DAQE-AN101190104-22 issued September 26, 2022 (0104-22)
Table 24: Chevron Products Company – Salt Lake Refinery Facility-Wide Emissions
Chevron Products Company – Salt Lake Refinery Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 265.50 766.50
VOC 339.60 1,242.06

UTAH DIVISION OF AIR QUALITY
41

4.4.4 RACT Analysis
The RACT evaluations were performed using data from Chevron Refinery, AOs and supporting
documentation, and Section IX, Utah SIP Parts H.11 and H.12. Various resources were evaluated to
identify all existing and potential controls and emission rates, including EPA’s RBLC; technical
documents, EPA fact sheets, applicable CTGs, and other applicable literature; state and federal
regulations; and other state SIPs. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 25.

Table 25: Chevron Products Company – Salt Lake Refinery
Chevron Products Company – Salt Lake Refinery
RACT
Section
#55
Emission
Unit /
Activity
Pollutant RACT
Determin
ation
Enforceability Comments
AO Conditions PM2.5 SIP
Conditions
II.A FCCU
Regenerator
NOx Feed
hydrotrea
ting &
refinery-
wide NOx
limit.
(0106-22)
II.B.1.h &
II.B.7.b
H.12.d.ii Current
operations
meet
RACT, no
further
action
warranted. VOCs Good
combustio
n
practices,
no
additional
controls.
(0106-22)
I.5
No
II.B Process
Heaters and
Boilers
NOx LNB, FGR
(Boilers 5,
6,7), &
refinery-
wide NOx
limit,
complianc
e with
NSPS
Subpart
Ja.
(0106-22)
II.B.1.h, II.B.2,
& II.B.3
H.12.d.ii &
H.12.d.vii
Current
operations
meet
RACT, no
further
action
warranted.
VOCs Good
combustio
n
practices,
(0106-22)
I.5
No

55 https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001911.pdf

UTAH DIVISION OF AIR QUALITY
42

no
additional
controls,
complianc
e with
NSPS
Subpart
Ja.
II.B Crude
Heaters
NOx LNB &
refinery-
wide NOx
limit.
(0106-22)
II.B.1.h
H.12.d.ii &
H.12.d.vii

Current
operations
meet
RACT, no
further
action
warranted.
VOCs Good
combustio
n
practices.
(0106-22)
I.5

No
II.C SRU NOx Existing
tail gas
treatment
unit and
thermal
oxidizer &
refinery-
wide NOx
limit.
(0106-22)
II.B.1.h
H.12.d.ii &
H.12.d.vii
Current
operations
meet
RACT, no
further
action
warranted.
II.D Cooling
Towers
VOCs MACT
Subpart
CC
requireme
nts on
cooling
towers
servicing
high VOC
heat
exchanger
s.
(0106-22)
II.B.10.a
H.11.g.iii Current
operations
meet
RACT, no
further
action
warranted.
II.E Fugitive
emissions
VOCs Low leak
LDAR
requireme
nts of
NSPS
Subpart
GGGa.
(0106-22)
II.B.10.b
H.11.g.iv Current
operations
meet
RACT, no
further
action
warranted.
II.F Tanks VOCs Submerge
d fill
(0106-22)
II.B.10.c1
H.11.g.vi Current
operations

UTAH DIVISION OF AIR QUALITY
43

operation
s & tank
degassing
requireme
nts -
complianc
e with
NSPS
Subpart
Kb or
MACT
Subpart
CC.
&
(0104-22)
II.B.2.c2
meet
RACT, no
further
action
warranted.
II.G Wastewater
System
VOCs Induced
air
floatation
& RTO,
complianc
e with
NSPS
Subpart
QQQ and
National
Emission
Standards
for
Hazardous
Air
Pollutants
(NESHAP)
Subpart
FF.
(0104-22)
II.B.2.a &
II.B.2.b
H.12.d.vii Current
operations
meet
RACT, no
further
action
warranted.
II.H Refinery
Flares
NOx Evaluated
through
control of
flare
gases, not
through
individual
pollutants
,
requireme
nt to meet
NSPS
Subpart Ja
for flares.
(0106-22)
II.B.10.d
H.11.g.v,
H.12.d.ii, &
H.12.d.vii
Current
operations
meet
RACT, no
further
action
warranted.
VOCs

UTAH DIVISION OF AIR QUALITY
44

II.I Standby Fire
Pumps and
Emergency
Diesel
Engines
VOCs Proper
maintena
nce and
operation,
and
complianc
e with
NESHAP
Subpart
ZZZZ.
(0106-22)
I.5
H.12.d.iv Current
operations
meet
RACT, no
further
action
warranted.
NOx (0106-22)
II.B.8.c
II.L Reformer
Compressor
Engines
NOx Use of
NSCR
meeting
NOx
emission
limits in
SIP
Section IX,
Part
H.12.d.v.
(0106-22)
II.B.9.a
H.12.d.v &
H.12.d.vii
SCR
incorrectly
required in
SIP Section
IX, Part
H.12.d.vii.
Correct
control
required is
NSCR.
Current
operations
meet
RACT, no
further
action
warranted.
II.J Crude Oil
Loading
Racks
VOCs Vapor
Combusti
on Unit
with a
98% VOC
control
efficiency.
(0104-22)
II.B.3.a
H.12.d.vii Current
operations
meet
RACT, no
further
action
warranted.
N/A

Refinery
General
Approach

NOx

Refinery-
wide NOx
limit.

(0106-22)
II.B.1.h

H.12.d.ii

Current
operations
meet
RACT, no
further
action
warranted.
4.4.5 Conclusion of RACT Implementation
The emission units/activities examined in this RACT analysis indicates that all activities currently
meet all RACT requirements, and all other existing controls and emissions limitations are considered

UTAH DIVISION OF AIR QUALITY
45

RACT for the Chevron Refinery. No other additional add-on controls or limitations are technically or
economically feasible options at this time.
4.5 Hexcel Corporation
4.5.1 Introduction
This section specifically serves as an evaluation of Hexcel Corporation (Hexcel). In addition to its
past BACT reports, Hexcel submitted an additional RACT analysis for evaluation January 31, 2023.
Specific Ozone SIP conditions for Hexcel can be found in Section IX, Part H.32.c.
4.5.2 Facility Process Summary
Hexcel owns and operates a carbon fiber and fabric pre-impregnation manufacturing plant in
West Valley City. Products made at Hexcel are used in commercial aerospace primary and secondary
structures, helicopters, defense aircraft, satellites, and sporting equipment. The facility consists of
twelve production buildings, two raw material receiving warehouses, and a material testing laboratory.
The plant manufactures carbon fibers and hot melt pre-impregnation fabrics. The plant also produces
epoxy resins, adhesive films, and solvated fabrics.
4.5.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the Hexcel industrial processes and equipment are
summarized in Table 26. The 2017 actual emissions were used as the baseline emissions. The current
PTE values for Hexcel were established by the most recent active AOs issued to the source.
• AO DAQE-AN113860032-19 issued May 13, 2019 (0032-19)
Table 26: Hexcel Corporation Facility-Wide Emissions
Hexcel Corporation Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 187.90 197.51
VOC 154.20 168.34
4.5.4 RACT Analysis
The RACT evaluations were performed using data from Hexcel, AOs and supporting
documentation, and Utah SIP Section IX, Parts H.11 and H.12. Various resources were evaluated to
identify all existing and potential controls and emission rates, including EPA’s RBLC; technical
documents, EPA fact sheets, applicable CTGs, and other applicable literature; state and federal
regulations; and other state SIPS. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 27.

Table 27: Hexcel Corporation

Hexcel Corporation
Pollutant Enforceability Comments

UTAH DIVISION OF AIR QUALITY
46

RACT
Section
#56
Emission
Unit/Activity
RACT
Determination
AO
Conditions
PM2.5 SIP
Conditions
4.0 -
4.2
All Fiber
Lines
All Consumption
and
production
limits.
(0032-19)
II.B.1.b
H.12.f.i &
H.12.f.vi
Current operations
meet RACT, no
further action
warranted.
4.0 -
4.2
Fiber Lines 2
thru 8, 10
thru 12
VOCs Good
combustion
practices,
natural gas as
fuel,
incineration
and flaring
technology.
(0032-19)
I.5;
II.B.1.d -
II.B.1.l;
II.B.3.a -
II.B.3.d;
II.B.4.a -
II.B.4.c; &
II.B.5.a -
II.B.5.b
No Current operations
meet RACT, no
further action
warranted. Fiber Lines 2,
5, 6, 8, 10
thru 12
NOx
4.0 -
4.2
Fiber Lines 3,
4, and 7
NOx ULNB with
FGR required
to be installed
by December
31, 2024.
No H.12.f.iv Current operations
meet RACT, no
further action
warranted.
4.0 -
4.2
Fiber Lines
13 thru 16
VOCs RTO,
incineration
and flaring
technology.
(0032-19)
I.5;
II.B.1.d -
II.B.1.l;
II.B.6.a; &
II.B.7.a
H.12.f.ii Current operations
meet RACT, no
further action
warranted.
NOx LNB on
thermal
oxidizer and
RTO, good
combustion
practices,
natural gas as
fuel.
H.12.f.ii,
H.12.f.v
4.3 Pilot VOCs Good
combustion
practices,
natural gas as
fuel, proper
maintenance,
incineration
and flaring
technology.
(0032-19)
I.5 &
II.B.1.d -
II.B.1.l
No Current operations
meet RACT, no
further action
warranted.
NOx

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UTAH DIVISION OF AIR QUALITY
47

5.0 Matrix
(Solvent
Coating
Operations)
VOCs Good
combustion
practices,
natural gas as
fuel, proper
maintenance,
incineration
and flaring
technology.
(0032-19)
I.5;
II.B.1.j;
II.B.1.o; &
II.B.1.p
No Current operations
meet RACT, no
further action
warranted.
NOx
6.0 Boilers VOCs Use of pipeline
quality natural
gas, good
combustion
practices,
good design, &
proper
operation.
(0032-19)
I.5
No Current operations
meet RACT, no
further action
warranted.

NOx Compliance
with a NOx
emission rate
of 9 ppm.
(0032-19)
I.5
No
7.0 Emergency
Generators
VOCs Proper
maintenance
and operation,
Subpart IIII
and Subpart
ZZZZ.
(0032-19)
I.5
No Current operations
meet RACT, no
further action
warranted. NOx
8.0 HVAC VOCs Proper
maintenance
and operation.
(0032-19)
I.5 &
II.B.1.o
No Current operations
meet RACT, no
further action
warranted. NOx
4.5.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for Hexcel. RACT evaluations showed that additional add-
on controls or limitations are not technically or economically feasible options at this time. No additional
RACT measures were identified, and all RACT determinations are already being implemented. Therefore,
there are no additional implementation schedules or requirements for Hexcel as required by this SIP
revision.

UTAH DIVISION OF AIR QUALITY
48

4.6 Hill Air Force Base
4.6.1 Introduction
This section specifically serves as an evaluation of Hill Air Force Base (Hill AFB). Hill AFB did not
submit an additional RACT analysis for evaluation, and thus UDAQ relied on the more stringent BACT
analysis submitted for NOx and VOC emissions as evaluated for the Salt Lake City PM2.5 serious SIP.
Specific conditions as they relate to this SIP revision for Hill AFB can be found in Section IX, Part H.32.d.
4.6.2 Facility Process Summary
Hill AFB is a large U.S. Air Force base located in northern Utah, just south of the city of Ogden.
Hill AFB is the home of the Air Force Material Command’s Ogden Air Logistics Complex, which is the
worldwide manager for a wide range of aircraft, engines, missiles, software, avionics, and accessories
components, and provides worldwide logistics support for Air Force and Defense Department weapon
systems. Additional tenant units include the Air Combat Command and the Air Force Reserve Command.
Hill AFB has extensive industrial facilities for painting, paint stripping, plating, parts
warehousing/distribution, wastewater treatment, and manages and maintains air munitions, solid
propellants, landing gear, and training devices.
4.6.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the Hill AFB processes and equipment are summarized in Table
28. The 2017 actual emissions were used as the baseline emissions. The current PTE values for Hill AFB
were established by the most recent active AOs issued to the source.
• AO DAQE-AN101210245-16 issued September 1, 2016 (0245-16)
• AO DAQE-AN101210200A-09 issued December 17, 2009 (0200A-09)
• AO DAQE-AN0121175-06 issued October 16, 2006 (175-06)
• AO DAQE-AN101210266-19 issued May 8, 2019 (0266-19)
• AO DAQE-AN0101210195-09 issued August 10, 2009 (0195-09)
• AO DAQE-AN101210233-12 issued January 27, 2012 (0233-12)
• AO DAQE-AN101210225-12 issued April 19, 2012 (0225-12)
• AO DAQE-AN101210248-17 issued June 7, 2017 (0248-17)
• AO DAQE-AN101210228-12 issued June 13, 2012 (0228-12)
• AO DAQE-AN0101210214-11 issued June 28, 2011 (0214-11)
• AO DAQE-AN101210229-12 issued October 29, 2012 (0229-12)
• AO DAQE-AN101210233-14 issued June 26, 2014 (0233-14)
• AO DAQE-AN101210237-15 issued March 9, 2015 (0237-15)
• AO DAQE-AN101210241-15 issued November 5, 2015 (0241-15)
• AO DAQE-AN101210260-19 issued April 3, 2019 (0260-19)
• AO DAQE-AN101210240B-16 issued February 8, 2016 (0240B-16)
Table 28: Hill Air Force Base Facility-Wide Emissions
Hill Air Force Base Facility Emissions
Pollutant Baseline Emissions PTE

UTAH DIVISION OF AIR QUALITY
49

(TPY) (TPY)
NOx 101.43 279.81
VOC 140.24 330.41
4.6.4 RACT Analysis
The RACT evaluations were performed using data from Hill AFB, AOs and supporting
documentation, and Utah SIP Section IX, Parts H.11 and H.12. Various resources were evaluated to
identify all existing and potential controls and emission rates, including EPA’s RBLC; technical
documents, EPA fact sheets, applicable CTGs, and other applicable literature; state and federal
regulations; and other state SIPS. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 29.

UTAH DIVISION OF AIR QUALITY
50

Table 29: Hill Air Force Base
Hill Air Force Base
TSD
Section
#57
Emission
Unit/Activity
Pollutant BACT
Determination
Enforceability Comments
AO
Conditions
PM2.5 SIP
Conditions
2.1.1 Boilers VOCs Use of pipeline
quality natural
gas (low sulfur
fuel), good
combustion
practices,
good design,
and proper
operation.
(0245-16)
I.5
No Current operations
meet RACT, no
further action
warranted.
NOx All boilers
older than
January 1,
1989, will be
removed. The
combined
heat NOx
emissions for
all boilers
(except those
less than 5
MMBtu/hr)
shall not
exceed 95
lb/hr.
(0245-16)
II.B.1.a &
II.B.2.a

H.12.q.ii Current operations
meet RACT, no
further action
warranted.
2.1.2 Surface
Coating,
Cleaning &
Chemically
De-painting
Operations
VOCs Low VOC
coatings, work
practice
standards,
emissions limit
of 0.58 tpd,
and proper
maintenance.
(0200A-
09)
II.B.1.a
through
II.B.1.m

H.12.q.i Current operations
meet RACT, no
further action
warranted.

57 https://documents.deq.utah.gov/air-quality/pm25-serious-sip/DAQ-2018-007651.pdf

UTAH DIVISION OF AIR QUALITY
51

2.1.3 Emergency
Equipment
Operations
VOCs Limited hours
of operation
for
maintenance
and testing,
good
combustion
practices, use
of a tier-
certified
engine when
required
under NSPS
Subpart IIII
and JJJJ, the
use of ULSD
and proper
equipment
operation,
maintenance
schedules and
protocols.
(175-06)
I.E & II.C

(0266-19)
I.5 &
II.B.1.b
No Current operations
meet RACT, no
further action
warranted.

NOx
2.1.4 Testing
Operations
VOCs Site-wide fuel
limit and
proper
operation,
maintenance,
and protocols.
(0195-09)
I.5,
II.B.1.a,
II.B.2.a, &
II.B.3.a
(0233-12)
I.5 &
II.B.1.b
(0225-12)
I.5 &
II.B.1.a
(0248-17)
I.4,
II.B.1.a, &
II.B.1.b
No Current operations
meet RACT, no
further action
warranted.

NOx
2.1.5 Degreasing
Operations
VOCs Use of low
volatility
solvents,
proper
operation,
maintenance
and operation
protocols with
(0228-12)
I.6, II.B.1.a
through
II.B.1.f

No Current operations
meet RACT, no
further action
warranted.

UTAH DIVISION OF AIR QUALITY
52

a limit on VOC
emissions.
2.1.6 Misc.
Coating and
Blasting
VOCs Scrubbers,
low-sulfur
fuel, limited
use, proper
operation,
maintenance
and protocols.
(0214-11)
I.5 &
II.B.1.a
(0229-12)
I.5
(0233-14)
I.5 &
II.B.1.a

No Current operations
meet RACT, no
further action
warranted.

NOx Limited use,
proper
operation,
maintenance,
and protocols.
2.1.7 Air Handlers
& Heaters
VOCs LNBs, low
sulfur fuel,
limited use,
proper
operation,
maintenance,
and protocols.
(0237-15)
I.5 &
II.B.1.a

No Current operations
meet RACT, no
further action
warranted. NOx
2.1.8 Fuel
Operations
VOCs Fuel storage:
vapor
balancing
system and
submerged
loading as
required by
R307-328,
limited use,
proper
operation,
maintenance
and protocols.

Distillation:
Limited use,
proper
operation,
Maintenance
and protocols.
(0241-15)
I.5 and
II.B.1.a
(0260-19)
I.5,
II.B.1.a, &
II.B.1.b

No Current operations
meet RACT, no
further action
warranted.

2.1.10 Industrial
Wastewater
Operation
VOCs Limiting VOC
emission,
proper
operation,
(0240B-
16)
I.5,
II.B.1.a, &
II.B.1.b
No Current operations
meet RACT, no
further action
warranted.

UTAH DIVISION OF AIR QUALITY
53

maintenance
and protocols.

4.6.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for Hill AFB. Re-evaluation of BACT showed that
additional add-on controls or limitations are not technically or economically feasible options at this time.
No additional RACT measures were identified, and all RACT determinations are already being
implemented. Therefore, there are no additional implementation schedules or requirements for Hill AFB
as required by this SIP revision.

4.7 Holly Frontier Sinclair Woods Cross Refinery

4.7.1 Introduction
This section specifically serves as an evaluation of Holly Frontier Sinclair Woods Cross Refinery
(HF Sinclair Refinery). In addition to its BACT report submitted as part of the Salt Lake City PM2.5 serious
SIP, HF Sinclair Refinery submitted an additional RACT analysis for evaluation on January 31, 2023, with
supporting information submitted February 23, 2023. Specific conditions related to this SIP revision for
HF Sinclair Refinery can be found in Section IX, Part H.32.e.

4.7.2 Facility Process Summary
The HF Sinclair Refinery is a petroleum refinery capable of processing 60,000 barrels per day of
crude oil, primarily heavier black wax and yellow wax crudes from eastern Utah. The refinery produces a
variety of products including gasoline, natural gas liquids, propane, butanes, jet fuels, fuel oils, and
kerosene products. The refinery receives and distributes products by tanker truck, rail car, and pipeline.
The source consists of two FCCUs, both controlled with wet gas scrubbers. A single sulfur recovery unit
controls the sulfur content of the fuel gas. The source also has an assortment of heaters, boilers, cooling
towers, storage tanks, flares, and related fugitive emissions.

4.7.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the HF Sinclair Refinery processes and equipment are
summarized in Table 28. The 2017 actual emissions were used as the baseline emissions. The current
PTE values for HF Sinclair Refinery were established by the most recent active AOs issued to the source.
• AO DAQE-AN101230053-22 issued September 1, 2022 (0053-22)
Table 30: Holly Frontier Sinclair Woods Cross Refinery Facility-Wide Emissions
Holly Frontier Sinclair Woods Cross Refinery Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 170.51 347.10
VOC 217.45 223.63

4.7.4 RACT Analysis
The RACT evaluations were performed using data from HF Sinclair Refinery, AOs and supporting
documentation, and Utah SIP Section IX, Parts H.11 and H.12. Various resources were evaluated to

UTAH DIVISION OF AIR QUALITY
54

identify all existing and potential controls and emission rates, including EPA’s RBLC; technical
documents, EPA fact sheets, applicable CTGs, and other applicable literature; state and federal
regulations; and other state SIPS. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 31.

Table 31: Holly Frontier Sinclair Woods Cross Refinery
Holly Frontier Sinclair Woods Cross Refinery
RACT
Section
#58
Emission
Unit/Activity
Pollutant RACT
Determination
Enforceability Comments
AO
Condition
s
PM2.5 SIP
Conditions
3.4 &
4.5
FCCU
Regenerator
NOx Wet gas
scrubber with
use of LoTOx
add-on &
refinery-wide
NOx limit.
(0053-22)
II.B.4 &
II.B.8.b
H.12.g.ii &
H.12.g.vi
Current
operations meet
RACT, no further
action
warranted.
4.5 VOCs Good
combustion
practices, no
additional
controls.
(0053-22)
I.5
No
3.1 &
4.1
Process
Heaters and
Boilers
NOx LNB, ULNB,
some use of
SCR, &
refinery-wide
NOx limit.
(0053-22)
II.B.4.a &
II.B.6.b
H.12.g.ii &
H.12.g.vi
Current
operations meet
RACT, no further
action
warranted.
4.1 VOCs Good
combustion
practices, no
additional
controls.
(0053-22)
I.5 &
II.B.6.d
No
3.3 &
4.4
Sulfur
Recovery
Unit Tail Gas
incinerator
NOx Wet Gas
Scrubber, Low-
NOx burner &
refinery-wide
NOx limit.
(0053-22)
I.5 &
II.B.4.a
H.12.g.ii &
H.12.g.vi
Current
operations meet
RACT, no further
action
warranted.
4.4 VOCs Wet Gas
Scrubber.
4.3 Cooling
Towers
VOCs MACT Subpart
CC
requirements
on cooling
(0053-22)
II.B.12.a
H.11.g.iii Current
operations meet
RACT, no further

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UTAH DIVISION OF AIR QUALITY
55

towers
servicing high
VOC heat
exchangers.
action
warranted.
4.9 Fugitive
emissions/
Equipment
Leaks
VOCs Low leak LDAR
requirements
of NSPS
Subpart GGGa.
(0053-22)
II.B.1.h
H.11.g.iv Current
operations meet
RACT, no further
action
warranted.
4.6 Fixed Roof
Tanks
VOCs Compliance
with NSPS
Subpart Kb,
MACT Subpart
WW, and
LDAR.
(0053-22)
I.5
H.11.g.vi Current
operations meet
RACT, no further
action
warranted.
4.7 Internal
Floating Roof
Storage tanks
VOCs Submerged fill
operations &
tank degassing
requirements -
eventual
compliance
with NSPS
Subpart Kb or
MACT Subpart
CC and MACT
Subpart WW.
(0053-22)
I.5

H.11.g.vi

Current
operations meet
RACT, no further
action
warranted.
4.8 External
Floating Roof
VOCs Compliant with
NSPS Subpart
Kb or MACT
Subpart CC and
MACT Subpart
WW.
(0053-22)
I.5

H.11.g.vi

Current
operations meet
RACT, no further
action
warranted.
4.10 Wastewater
System
VOCs Closed vent
system with
carbon
adsorption.
Compliance
with NSPS
Subpart QQQ
and MACT
Subpart FF.
(0053-22)
I.5
H.12.g.vi Current
operations meet
RACT, no further
action
warranted.
3.2 &
4.2
Refinery
Flares
NOx Flare Gas
recovery
system,
requirement to
(0053-22)
II.B.1.g
H.11.g.v,
H.12.g.ii, &
H.12.g.vi
Current
operations meet
RACT, no further
action
warranted.
4.2 VOCs

UTAH DIVISION OF AIR QUALITY
56

meet NSPS
Subpart Ja.
3.5 &
4.12
Standby
Diesel
Engines
VOCs Proper
maintenance
and operation,
compliance
with MACT
Subpart ZZZZ.
(0053-22)
I.5
H.12.g.iv Current
operations meet
RACT, no further
action
warranted.
4.1 NOx
3.6 &
4.13
Standby
Emergency
Nat Gas
Engines
VOCs Proper
maintenance
and operation,
compliance
with NSPS
Subpart JJJJ
and MACT
Subpart ZZZZ.
(0053-22)
I.5
No Current
operations meet
RACT, no further
action
warranted.
4.1 NOx
4.11 Product
Loading
VOCs Submerged or
bottom loading
as well as
vapor
balancing.
(0053-22)
I.5
No Current
operations meet
RACT, no further
action
warranted.
N/A

Refinery
General
Approach

NOx

Refinery-wide
NOx limit.

(0053-22)
II.B.4

H.12.g.ii

Current
operations meet
RACT, no further
action
warranted.
4.7.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for the HF Sinclair Refinery. RACT evaluations showed
that additional add-on controls or limitations are not technically or economically feasible options at this
time. No additional RACT measures were identified, and all RACT determinations are already being
implemented. Therefore, there are no additional implementation schedules or requirements for the HF
Sinclair Refinery as required by this SIP revision.
4.8 Kennecott Utah Copper Bingham Canyon Mine and Copperton Concentrator
4.8.1 Introduction
This section specifically serves as an evaluation of Kennecott Utah Copper (KUC) – Bingham
Canyon Mine (BCM) and Copperton Concentrator (CC). In addition to past submitted BACT reports, KUC
submitted an additional RACT analysis for evaluation January 30, 2023. Specific conditions for this SIP
revision for KUC BCM & CC can be found in Section IX, Part H.32.f.

UTAH DIVISION OF AIR QUALITY
57

4.8.2 Facility Process Summary
The KUC BCM is an open pit mining operation located in the southwest corner of Salt Lake
County. The ore and waste rock at the BCM are transferred from the mining areas to other areas of the
mine through a series of transfers using haul trucks and conveyor belts. Ore is crushed in the in-pit
crusher. After the ore is crushed, it is conveyed to the KUC CC located approximately five miles north of
the open pit. At the CC, semi-autogenous grinding mills and ball mills grind the ore into a slurry. The
slurry is sent through cyclone clusters, and the cyclone overflow is fed into flotation circuits and mixed
with reagents. The flotation circuits are aerated to float copper and other valuable by-products from the
ore. Once the ore is processed at the concentrator, it is transferred to the smelter.
4.8.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the KUC BCM & CC processes and equipment are
summarized in Table 31. The 2017 actual emissions were used as the baseline emissions. The current
PTE values for KUC BCM & CC were established by the most recent active AOs issued to the source.
• AO DAQE-AN105710047-21 issued May 10, 2021 (0047-21)
• AO DAQE-AN105710044-18 issued August 21, 2018 (0044-18)
Table 31: KUC Bingham Canyon Mine and Copperton Concentrator Facility-Wide Emissions
KUC Bingham Canyon Mine & Copperton Concentrator Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 4,209.19 5,852.77
VOC 210.03 318.17

4.8.4 RACT Analysis
The RACT evaluations were performed using data from KUC, AOs and supporting
documentation, and Utah SIP Section IX, Parts H.11 and H.12. Various resources were evaluated to
identify all existing and potential controls and emission rates, including EPA’s RBLC; technical
documents, EPA fact sheets, applicable CTGs, and other applicable literature; state and federal
regulations; and other state SIPs. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 33.

Table 33: Kennecott Utah Copper: Bingham Canyon Mine and Copperton Concentrator
Kennecott Utah Copper: Bingham Canyon Mine & Copperton Concentrator
Bingham Canyon Mine
RACT
Section
#59
Emission
Unit/Activity
Pollutant RACT
Determination
Enforceability Comments
AO
Condition
PM2.5 SIP
Conditions

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2.1.1 Tailpipe
Emissions
from Mobile
Sources
NOx Compliance
with non-road
EPA Standards.
(0047-21)
II.B.1.f
H.12.h.i.A Current
operations
meet RACT, no
further action
warranted.
2.1.5 Solvent
Extraction
and
Electrowinni
ng Process
NOx Use of mist
eliminators and
covers in tanks,
mixers, and
settlers.
(0047-21)
II.B.2.f &
II.B.2.g
No Current
operations
meet RACT, no
further action
warranted.
VOCs
2.1.2 Gasoline
Fueling
VOCs Stage I and
Stage 2
recovery
systems.
(0047-21)
I.5
No Current
operations
meet RACT, no
further action
warranted.
2.1.3 Cold Solvent
Degreasing
Washers
VOCs Compliance
with R307-335.
(0047-21)
I.5
No Current
operations
meet RACT, no
further action
warranted.
2.1.4 Propane
Communicati
ons
Generator
VOCs Proper
maintenance
and operation,
and
compliance
with applicable
NSPS or MACT
requirements.
(0047-21)
I.5
No Current
operations
meet RACT, no
further action
warranted.
NOx
PM2.5
BACT
TSD
1.460
Diesel-Fired
Emergency
Generators
VOCs BACT
determination:
proper
maintenance
and operation,
and
compliance
with applicable
NSPS or MACT
requirements.
(0047-21)
I.5
No Equipment not
operated
during
evaluation
period, no
additional
RACT
submitted.
Current
operations
meet RACT, no
further action
warranted.
NOx

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UTAH DIVISION OF AIR QUALITY
59

Copperton Concentrator
RACT
Section
#
Emission
Unit/Activity
Pollutant RACT
Determination
Enforceability Comments
AO
Condition
PM2.5 SIP
Conditions
2.2.1 Tioga
Heaters
VOCs Use of pipeline
quality natural
gas, good
combustion
practices, and
good design
and proper
operation
(0044-18)
I.5
No Current
operations
meet RACT, no
further action
warranted. NOx
2.2.4 Feed and
Product
Dryer Oil
Heaters
VOCs Use of pipeline
quality natural
gas and good
combustion
practices.
(0044-18)
I.5
No Current
operations
meet RACT, no
further action
warranted.
NOx LNBs H.12.h.ii.A
2.2.2 Degreasing
Parts
Washers
VOCs Compliance
with the
requirements
of R307-335.
(0044-18)
I.5
No Current
operations
meet RACT, no
further action
warranted.
2.2.3 Gasoline
Fueling
Stations
VOCs Stage I and
Stage 2
recovery
systems.
(0044-18)
I.5
No Current
operations
meet RACT, no
further action
warranted.
PM2.5
BACT
TSD
1.4

Three
Storage
Tanks
(Sodium
Cyanide)
VOCs BACT
determination:
use of
submerged
pipes.
(0044-18)
I.5
No Equipment not
operated
during
evaluation
period, no
additional
RACT
submitted.
Current
operations
meet RACT, no
further action
warranted.

UTAH DIVISION OF AIR QUALITY
60

2.1.4 Liquid
Propane-
Fired
Emergency
Generator
VOCs Proper
maintenance
and operation,
and
compliance
with applicable
NSPS or MACT
requirements.
(0044-18)
I.5
No Current
operations
meet RACT, no
further action
warranted.
NOx

4.8.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for KUC BCM & CC. RACT evaluations showed that
additional add-on controls or limitations are not technically or economically feasible options at this time.
No additional RACT measures were identified, and all RACT determinations are already being
implemented. Therefore, there are no additional implementation schedules or requirements for KUC
BCM & CC as required by this SIP revision.
4.9 KUC Smelter and Refinery
4.9.1 Introduction
This section specifically serves as an evaluation of KUC – Smelter and Refinery. In addition to
past BACT reports, KUC submitted an additional RACT analysis for evaluation January 30, 2023. Specific
conditions for this SIP revision for the KUC Smelter and Refinery can be found in Section IX, Part H.32.g.
4.9.2 Facility Process Summary
KUC operates a copper smelter and refinery in Salt Lake County. The Smelter employs flash
smelting technology with flash converting technology to produce copper anodes and high concentration
sulfur dioxide gases. Copper ore concentrates from the Copperton Concentrator are first dewatered,
dried, blended with fluxes and secondary copper-bearing materials, then fed to a flash smelting furnace
where the ore is melted and reacts to produce copper matte. The copper matte is converted to blister
copper by oxidization, reduced in the anode furnace to produce a high purity copper, and then poured
in molds to cast solid copper ingots (anodes). The anodes are moved to the Refinery co-located near the
Smelter. The Refinery uses an electrolytic refining process to convert the Smelter-produced anodes to
high-purity cathode copper and also recover precious metals from the electrolytic refinery slimes in a
precious metals circuit.
4.9.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the KUC Smelter and Refinery processes and equipment are
summarized in Table 34. The 2017 actual emissions were used as the baseline emissions. The current
PTE values for the KUC Smelter and Refinery were established by the most recent active AOs issued to
the source.
• AO DAQE-AN103460058-20 issued November 12, 2020 (0058-20)
• AO DAQE-AN103460061-22 issued June 23, 2022 (0061-22)

UTAH DIVISION OF AIR QUALITY
61

Table 34: KUC Smelter and Refinery Facility-Wide Emissions
KUC Smelter and Refinery Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 154.87 198.13
VOC 10.94 20.47
4.9.4 RACT Analysis
The RACT evaluations were performed using data from KUC, AOs and supporting
documentation, and Utah SIP Section IX, Parts H.11 and H.12. Various resources were evaluated to
identify all existing and potential controls and emission rates, including EPA’s RBLC; technical
documents, EPA fact sheets, applicable CTGs, and other applicable literature; state and federal
regulations; and other state SIPS. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 35.

Table 35: Kennecott Utah Copper: Smelter and Refinery
Kennecott Utah Copper: Smelter and Refinery
Refinery
RACT
Section
#61
Emission
Unit/Activity
Pollutant RACT
Determination
Enforceability Comments
AO
Conditio
n
PM2.5 SIP
Conditions
3.2.1 Boiler VOCs Use of pipeline
quality natural
gas, good
combustion
practices, good
design, & proper
operation.
(0058-
20)
I.5 &
II.B.4.a
No Current
operations meet
RACT, no further
action
warranted.
NOx Installation of
ULNB (9 ppmvd)
on the boiler &
continued use of
FGR.
(0058-
20)
II.B.1.A
H.12.j.ii.A
&
H.12.j.ii.C
3.2.2 CHP VOCs Use of pipeline
quality natural
gas, good
combustion
practices, good
design, & proper
operation.
(0058-
20)
I.5 &
II.B.4.d
H.12.j.ii.D Current
operations meet
RACT, no further
action
warranted.

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UTAH DIVISION OF AIR QUALITY
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NOx Use of SoLoNOx
burner
technology (9
ppmv) on
turbine.
(0058-
20)
II.B.1.A
H.12.j.ii.A
3.1.8 Space
Heaters
VOCs Use of pipeline
quality natural
gas, good
combustion
practices, good
design, & proper
operation.
(0058-
20)
I.5
No Current
operations meet
RACT, no further
action
warranted. NOx
3.1.6 Gasoline
Fueling
VOCs Stage I and Stage
2 recovery
systems.
(0058-
20)
I.5
No Current
operations meet
RACT, no further
action
warranted.
PM2.5
BACT
TSD
1.462

Degreasing VOCs BACT
determination:
compliance with
R307-335.
(0058-
20)
I.5
No Equipment not
operated during
evaluation
period, no
additional RACT
submitted.
Current
operations meet
RACT, no further
action
warranted.
3.2.8 Paint VOCs Enclosures. (0058-
20)
I.5
No Current
operations meet
RACT, no further
action
warranted.
3.2.7 Prime Diesel
Generators
VOCs Proper
maintenance and
operation, and
compliance with
applicable NSPS
or MACT
requirements.
(0058-
20)
I.5
No Current
operations meet
RACT, no further
action
warranted. NOx
3.1.4 Refinery LPG
Emergency
VOCs Proper
maintenance and
operation, and
(0058-
20)
No Current
operations meet
RACT, no further

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63

Communicati
on Generator
NOx compliance with
applicable NSPS
or MACT
requirements.
I.5 &
II.B.4.e
action
warranted.
Smelter
RACT
Section
#
Emission
Unit/Activity
Pollutant RACT
Determination
Enforceability Comments
AO
Conditio
n
PM2.5 SIP
Conditions
3.1.1 Main Stack NOx Controls are
described for
each source that
vents to the Main
Stack. The
following sources
vent to the Main
Stack: anode
furnaces,
secondary gas
system, matte
grinding,
concentrate
dryer, acid plant,
and vacuum
cleaning system.
Compliance with
MACT Subpart
EEEEEE.
(0061-
22)
II.B.1.a &
II.B.3.a
H.12.j.i.A.I.
3
Current
operations meet
RACT, no further
action
warranted.
3.1.1.1 Anode
Furnaces
NOx LNB (30 ppmvd) (0061-
22)
II.B.1.a &
II.B.3.a
No Current
operations meet
RACT, no further
action
warranted. VOCs Use of pipeline
quality natural
gas and oxy-fuel,
good combustion
practices, good
design, & proper
operation.
(0061-
22)
I.5
3.1.1 Concentrate
Dryer
NOx Use of LNB &
good combustion
practices.
(0061-
22)
II.B.1.a &
II.B.3.a
No Current
operations meet
RACT, no further
action
warranted. VOCs Use of pipeline
quality natural
gas and oxy-fuel,
(0061-
22)
I.5

UTAH DIVISION OF AIR QUALITY
64

good combustion
practices, good
design, & proper
operation.
3.1.2 Powerhouse
Holman
Boiler
VOCs Use of pipeline
quality natural
gas, good
combustion
practices, good
design, proper
operation, &
limited natural
gas consumption.
(0061-
22)
I.5
No Current
operations meet
RACT, no further
action
warranted.
NOx Use of
continuous
monitoring to
ensure NOx
emissions do not
exceed 14 lbs/hr
(calendar-day
average); FGR.
(0061-
22)
II.B.1.a &
II.B.2
H.12.j.i.A.II
3.1.3 Powerhouse
Foster
Wheeler
Boiler (Now
Rentech
Boiler)
VOCs Use of pipeline
quality natural
gas, good
combustion
practices, good
design, proper
operation, &
limited natural
gas consumption.
(0061-
22)
I.5
No Replaced by
Rentech Boiler in
AO DAQE-
AN103460056-20
issued January
10, 2020. Current
operations meet
RACT, no further
action
warranted. NOx ULNB, 15 ppm (0061-
22)
II.B.1.a &
II.B.2
3.1.5 Cold Solvent
Degreaser
VOCs Compliance with
R307-335
(0061-
22)
I.5
No Current
operations meet
RACT, no further
action
warranted.
3.1.8 Space
Heaters
VOCs Use of pipeline
quality natural
gas, good
combustion
practices, good
design, & proper
operation.
(0061-
22)
I.5
No Current
operations meet
RACT, no further
action
warranted.
NOx

UTAH DIVISION OF AIR QUALITY
65

3.1.6 Fueling VOCs Stage I and Stage
2 recovery
systems.
(0061-
22)
I.5
No Current
operations meet
RACT, no further
action
warranted.
3.2.7,
3.1.7
Emergency
Backup
Power
Generators
VOCs Proper
maintenance and
operation, and
compliance with
applicable NSPS
or MACT
requirements.
(0061-
22)
I.5
No Current
operations meet
RACT, no further
action
warranted. NOx
PM2.5
BACT
TSD
1.4

Diesel
Compressor
VOCs BACT
determination:
proper
maintenance and
operation.
(0061-
22)
I.5
No Equipment not
operated during
evaluation
period, no
additional RACT
submitted.
Current
operations meet
RACT, no further
action
warranted.
NOx
3.1.4 Smelter LPG
Emergency
Communicati
on Generator
VOCs Proper
maintenance and
operation, and
compliance with
applicable NSPS
or MACT
requirements.
(0061-
22)
I.5
No Current
operations meet
RACT, no further
action
warranted. NOx
3.1.9 Hot Water
Boilers
VOCs Proper
maintenance and
operation.
(0061-
22)
I.5
No Current
operations meet
RACT, no further
action
warranted.
NOx

4.9.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for the KUC Smelter and Refinery. RACT evaluations
showed that additional add-on controls or limitations are not technically or economically feasible
options at this time. No additional RACT measures were identified, and all RACT determinations are
already being implemented. Therefore, there are no additional implementation schedules or
requirements for the KUC Smelter and Refinery as required by this SIP revision.

UTAH DIVISION OF AIR QUALITY
66

4.10 LHoist North America of Arizona, Inc.

4.10.1 Introduction
This section specifically serves as an evaluation of LHoist North America of Arizona, Inc. (LHoist).
LHoist did not submit an additional RACT analysis for evaluation. UDAQ referenced the more stringent
BACT for NOx and VOCs evaluated as part of the Salt Lake City PM2.5 serious SIP. Specific conditions for
this SIP revision for LHoist can be found in Section IX, Part H.32.h.
4.10.2 Facility Process Summary
LHoist operates a lime production facility near Grantsville that consists of a Quarry and Lime
Plant. Kiln operations were placed in temporary care and maintenance mode November 14, 2008, with
support operations having had limited operation since that date. Activities at the facility include mining
of limestone ore, limestone processing through various crushing and screening processes, operation of a
rotary kiln that heats the crushed limestone ore and converts it into quicklime, lime hydration
equipment to create hydrated lime, bagging facilities, and load-out operations. When operating, the
facility produces a variety of products including quicklime, hydrate, aggregate kiln-grade limestone,
overburden/low-grade limestone, and limestone chat.
4.10.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the LHoist processes and equipment are summarized in Table
36. The 2017 actual emissions were used as the baseline emissions. The current PTE values for LHoist
were established by the most recent active AOs issued to the source.
• AO DAQE-AN0707015-06 issued August 14, 2006 (015-06)

Table 36: LHoist North America of Arizona Facility Facility-Wide Emissions
LHoist North America of Arizona Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 0.11 328.66
VOC 0.07 3.01
4.10.4 RACT Analysis
The RACT evaluations were performed using data from LHoist, AOs and supporting
documentation, and Utah SIP Section IX, Parts H.11 and H.12. Various resources were evaluated to
identify all existing and potential controls and emission rates, including EPA’s RBLC; technical
documents, EPA fact sheets, applicable CTGs, and other applicable literature; state and federal
regulations; and other state SIPS. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 37.

UTAH DIVISION OF AIR QUALITY
67

Table 37: Lhoist North America of Arizona, Inc.
LHoist North America of Arizona, Inc.
TSD
Section
#63
Emission
Unit/Activity
Pollutant BACT
Determination
Enforceability Comments
AO
Conditions
PM2.5 SIP
Conditions
4.0 Rotary Kiln
System
NOx SNCR required
upon facility
startup.
No H.12.c.i &
H.12.c.ii
Current operations
meet RACT, no
further action
warranted.

VOCs Good
combustion
practices and
burner/process
optimization.
(015-06)
#22
No
5.0 Pressure
Hydrator
NOx Good
combustion
practices and
natural gas as
fuel.
(015-06)
#22
No Current operations
meet RACT, no
further action
warranted.
VOCs
7.0 Kiln Shaft
Motor
NOx Good
combustion
practices and
proper
maintenance.
(015-06)
#22
No Current operations
meet RACT, no
further action
warranted. VOCs

4.10.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for LHoist. Re-evaluation of BACT showed that additional
add-on controls or limitations are not technically or economically feasible options at this time. No
additional RACT measures were identified, and all RACT determinations are already being implemented.
Therefore, there are no additional implementation schedules or requirements for LHoist as required by
this SIP revision.
4.11 Pacificorp Energy Gadsby Power Plant
4.11.1 Introduction
This section specifically serves as an evaluation of Pacificorp Energy – Gadsby Power Plant
(Pacificorp Gadsby). Pacificorp Gadsby did not opt to submit an additional RACT analysis for evaluation,
therefore UDAQ referenced the more stringent BACT for NOx and VOCs evaluated as part of the PM2.5
serious SIP, with support information submitted by Pacificorp Gadsby March 10, 2023. Specific
conditions for this SIP revision for Pacificorp Gadsby can be found in Section IX, Part H.32.i.

63 https://documents.deq.utah.gov/air-quality/pm25-serious-sip/DAQ-2018-007681.pdf

UTAH DIVISION OF AIR QUALITY
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4.11.2 Facility Process Summary
Pacificorp Energy operates the Gadsby Power Plant located in Salt Lake City. The Gadsby Power
Plant is a natural gas-fired electric generating plant consisting of three steam boilers (Units #1-3) and
three simple-cycle combustion turbines (Units #4-6). Unit #1 is a 65 MW unit equipped with low NOx
burners; Unit #2 is an 80 MW unit equipped with low NOx burners; and Unit #3 is a 105 MW unit. All
three units are capable of using fuel oil as a back-up fuel during natural gas curtailments. Units #4-6 are
43.5 MW combustion turbine engines. The plant also has small emergency generators, cooling towers,
and small storage tanks.
4.11.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from Pacificorp Gadsby processes and equipment are summarized
in Table 38. The 2017 actual emissions were used as the baseline emissions. The current PTE values for
Pacificorp Gadsby were established by the most recent active AOs issued to the source.
• AO DAQE-AN103550015-09 issued January 12, 2009 (0015-09)
Table 38: Pacificorp Energy Gadsby Power Plant Facility-Wide Emissions
Pacificorp Energy Gadsby Power Plant Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 38.81 716.10
VOC 2.26 23.00
4.11.4 RACT Analysis
The RACT evaluations were performed using data from Pacificorp Gadsby, AOs and supporting
documentation, and SIP Section IX, Parts H.11 and H.12. Various resources were evaluated to identify all
existing and potential controls and emission rates, including EPA’s RBLC; technical documents, EPA fact
sheets, applicable CTGs, and other applicable literature; state and federal regulations; and other state
SIPS. The RACT determinations for each emission unit or activity emitting NOx and VOCs are provided in
Table 39.

Table 39: PacifiCorp Energy: Gadsby Power Plant
PacifiCorp Energy: Gadsby Power Plant
TSD
Section
#64
Emission
Unit/Activity
Pollutant BACT
Determination
Enforceability Comments
AO
Conditions
PM2.5 SIP
Conditions
4.0 Steam Generating
Units (Boilers 1-3)
NOx Natural gas as
fuel, good
combustion
practices, ULSD as
backup fuel, NOx
emission limits.
(0015-09)
II.B.4
H.12.l.i,
H.12.l.ii,
H.12.l.iii,
& H.12.l.iv
Current
operations
meet RACT,
no further
action
warranted.

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VOCs Good combustion
practices, proper
design.
(0015-09)
I.5
No
5.0 Combustion
Turbines (Units 4-
6)
NOx SCR, water/steam
injection.
(0015-09)
II.B.3
H.12.l.v Current
operations
meet RACT,
no further
action
warranted.
VOCs GCP and
oxidation
catalysts.
(0015-09)
I.5
No
6.3 Fuel Storage
Tanks
VOCs Submerged fill
operations, no
additional
controls.
(0015-09)
I.5
No Current
operations
meet RACT,
no further
action
warranted.
6.5 Misc. Painting
Operations
VOCs Use of low-VOC
compliant
coatings, high
transfer efficiency
applications, &
proper operation.
(0015-09)
I.5
No Current
operations
meet RACT,
no further
action
warranted.
6.2 Standby
Emergency
Engines
VOCs Proper
maintenance and
operation.
(0015-09)
I.5
No Current
operations
meet RACT,
no further
action
warranted.
NOx
5.5 Startup/Shutdown
at Combustion
Turbines
NOx Limitation of
hours of
operation for
startup/shutdown
to limit NOx,
alternative
operating
scenarios
included.
(0015-09)
I.5
H.12.l.vi Current
operations
meet RACT,
no further
action
warranted.
4.11.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for Pacificorp Gadsby. Re-evaluation of BACT showed
that additional add-on controls or limitations are not technically or economically feasible options at this
time. No additional RACT measures were identified, and all RACT determinations are already being
implemented. Therefore, there are no additional implementation schedules or requirements for
Pacificorp Gadsby as required by this SIP revision.

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70

4.12 Tesoro Refining & M arketing Company LLC dba Marathon Refinery
4.12.1 Introduction
This section specifically serves as an evaluation of Tesoro Refining and Marketing Company LLC
dba Marathon Refinery (Marathon Refinery). In addition to past BACT reports, Marathon Refinery
submitted an additional RACT analysis for evaluation January 31, 2023, with a subsequent submission
including additional information submitted on March 31, 2023. Specific conditions for this SIP revision
for Marathon Refinery can be found in Section IX, Part H.32.j.
4.12.2 Facility Process Summary
The Marathon Refinery is a petroleum refinery capable of processing 57,500 barrels per day of
crude oil. The source consists of one FCCU, a catalytic reforming unit, hydrotreating units, a sulfur
recovery unit, and cogeneration units. The source also has assorted heaters, boilers, cooling towers,
storage tanks, flares, and similar fugitive emissions.
4.12.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the Marathon Refinery processes and equipment are
summarized in Table 40. The 2017 actual emissions were used as the baseline emissions. The current
PTE values for Marathon Refinery were established by the most recent active AOs issued to the source.
• AO DAQE-AN103350075-18 issued January 11, 2018 (0075-18)
• AO DAQE-AN103350081A-21 issued January 12, 2021 (0081A-21)

Table 40: Tesoro Marathon Refinery Facility-Wide Emissions
Tesoro Marathon Refinery Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 313.27 638.05
VOC 230.77 769.88

4.12.4 RACT Analysis
The RACT evaluations were performed using data from Marathon Refinery, AOs and supporting
documentation, and Utah SIP Section IX, Parts H.11 and H.12. Various resources were evaluated to
identify all existing and potential controls and emission rates, including EPA’s RBLC; technical
documents, EPA fact sheets, applicable CTGs, and other applicable literature; state and federal
regulations; and other state SIPS. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 41.

Table 41: Tesoro Refining and Marketing Company LLC dba Marathon Refinery
Tesoro Refining and Marketing Company LLC dba Marathon Refinery
Pollutant Enforceability Comments

UTAH DIVISION OF AIR QUALITY
71

RACT
Section
#65
Emission
Unit/Activity
RACT
Determination
AO
Conditions
PM2.5 SIP
Conditions
4.0 FCCU
Regenerator
& CO Boiler
NOx Wet gas
scrubber with
use of LoTOx
add-on &
refinery-wide
NOx limit.
(0075-18)
II.B.1.g,
II.B.4.a,
II.B.4.f, &
II.B.7.a
H.12.m.ii
&
H.12.m.vi
Current operations
meet RACT, no
further action
warranted.
VOCs Good
combustion
practices, no
additional
controls.
(0075-18)
I.5
No
5.0 Process
Heaters and
Boilers
NOx LNB & ULNB
required on
various units,
& refinery-
wide NOx limit.
(0075-18)
II.B.1.g,
II.B.3.a, &
II.B.7.a
H.12.m.ii
&
H.12.m.vi
Current operations
meet RACT, no
further action
warranted.
VOCs Good
combustion
practices, no
additional
controls.
(0075-18)
I.5
No

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6.0 Cogeneration
Turbines
NOx Good
combustion
practices, use
of gaseous
fuels, &
refinery-wide
NOx limit. SCR
installation
required.
(0075-18)
II.B.1.g &
II.B.7.a
H.12.m.ii Installation of SCR
that meets a 5 ppm
NOx limit by
October 1, 2028.
Required by SIP
Section IX, Part
H.32.j.
VOCs Good
combustion
practices, no
additional
controls.
(0075-18)
I.5
No
7.0 SRU NOx Good
combustion
practices &
refinery-wide
NOx limit.
(0075-18)
II.B.1.g
H.12.m.ii
&
H.12.m.vi
Current operations
meet RACT, no
further action
warranted.
13.0 Cooling
Towers
VOCs MACT Subpart
CC
requirements
on cooling
towers
servicing high
VOC heat
exchangers.
(0075-18)
I.5

H.11.g.iii Current operations
meet RACT, no
further action
warranted.

UTAH DIVISION OF AIR QUALITY
73

8.0 Fugitive
emissions
VOCs Low leak LDAR
requirements
of NSPS
Subpart GGGa.
(0075-18)
I.5
H.11.g.iv Current operations
meet RACT, no
further action
warranted.
16.0 -
18.0
Tanks VOCs Submerged fill
operations,
and tank
degassing
requirements -
eventual
compliance
with NSPS
Subpart Kb or
MACT Subpart
CC. Secondary
seal
installation on
Tank 321
required.
(0075-18)
II.B.9
H.11.g.vi &
H.12.m.vi
Installation of
secondary seal on
Tank 321 by May 1,
2026. Required by
SIP Section IX, Part
H.32.j. All other
current operations
meet RACT, no
further action
warranted.
9.0 Wastewater
System
VOCs API separator
unit with fixed
cover;
installation of
closed vent
system to
carbon
adsorption
required.
(0075-18)
I.5

H.12.m.vi Installation of a
closed vent system
to carbon
adsorption by
December 31, 2025
in compliance with
NSPS Subpart QQQ.
Required by SIP
Section IX, Part
H.32.j.
11.0 &
12.0
Refinery
Flares
NOx Evaluated
through
control of flare
gases, not
through
individual
pollutants,
requirement
to meet
Subpart Ja for
flares.
(0075-18)
II.B.1.f
H.11.g.v &
H.12.m.vi
Current operations
meet RACT, no
further action
warranted.
VOCs

UTAH DIVISION OF AIR QUALITY
74

19.0 Standby
Emergency
Engines
VOCs Proper
maintenance
and operation,
and
compliance
with
applicable
NSPS or MACT
requirements.
(0075-18)
I.5
H.12.m.vi Current operations
meet RACT, no
further action
warranted.
NOx
15.0 K1
Compressors
(natural gas
engines)
VOCs Catalytic
converters,
proper
maintenance
and operation,
& refinery-
wide NOx limit
(0075-18)
I.5
(0075-18)
II.B.4.a,
II.B.7.a, &
II.B.7.c
H.12.m.ii Current operations
meet RACT, no
further action
warranted.
NOx
N/A Refinery
General
Approach
NOx Refinery-wide
NOx limit.
(0075-18)
II.B.1.g &
II.B.7.a
H.12.m.ii Current operations
meet RACT, no
further action
warranted.

4.12.5 Conclusion of RACT Implementation
The RACT analysis determined that all emission units/activities currently meet all RACT
requirements, and all other existing controls and emissions limitations are considered RACT for the
Marathon Refinery. The evaluations showed that the following control options are technically feasible:
• Installation of selective catalytic reduction (SCR) that meets a NOx emission rate of 5 ppm on the
Cogeneration Turbines
• Installation of a secondary seal on Tank 321
• Installation of a closed vent system controlled by carbon adsorption on the Wastewater System
The UDAQ has determined that these controls are necessary for the NWF NAA to demonstrate
attainment of the 2015 8-hour ozone NAAQS as expeditiously as practicable. While the financial
feasibility of the identified controls may be beyond previously established RACT thresholds, the CAA
provides states with “discretion to require beyond-RACT reductions from any source” if those reductions
are necessary to “demonstrate attainment as expeditiously as practicable”. 66
No other additional add-on controls or limitations are technically or economically feasible options at
this time. The installation of SCR on the Cogeneration Turbines will control total emissions from these
two turbines by approximately 68.7%. The installation of SCR will result in an annual emission reduction
of 68.78 tpy of NOx. The SCR shall be installed and operational by October 1, 2028. The installation of a
secondary seal on Tank 321 will result in 2.30 TPY of VOC emission reductions. The secondary seal shall
be installed and operational by May 1, 2026. The installation of a closed vent system with carbon

66 80 FR 12279 & 83 FR 62998

UTAH DIVISION OF AIR QUALITY
75

adsorption on the Wastewater System is a planned refinery modification that shall be installed and
operational by December 31, 2025, and result in approximately 10 TPY of VOC emission reductions.
All requirements for the Cogeneration Turbines, Tank 321, and the Wastewater System are
incorporated into SIP Section IX, Part H.32.j. No additional RACT measures were identified, and all other
identified RACT determinations are already being implemented.
4.13 Utah Municipal Power Agency West Valley Power Plant
4.13.1 Introduction
This section specifically serves as an evaluation of Utah Municipal Power Agency (UMPA) West
Valley Power Plant (WVPP). In addition to past BACT reports, UMPA submitted an additional RACT
analysis for evaluation January 31, 2023, with supporting information submitted March 1, 2023. Specific
conditions for this SIP revision for UMPA WVPP can be found in Section IX, Part H.32.l.
4.13.2 Facility Process Summary
UMPA operates the WVPP in West Valley City. The WVPP is a natural gas-fired electric
generating plant consisting of 5 natural gas simple cycle turbines. Each turbine has a power output rated
at 43.4 MW and is equipped with water injection, evaporative spray mist inlet air cooling, selective
catalytic reduction catalyst, and CO oxidation catalyst. The primary purpose of the plant is to produce
electricity for sale via the utility power distribution system to meet the demands of the Salt Lake Valley
service area.
4.13.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the WVPP processes and equipment are summarized in Table
42. The 2017 actual emissions were used as the baseline emissions. The current PTE values for the WVPP
were established by the most recent active AOs issued to the source.
• AO DAQE-282-02 issued April 18, 2002 (282-02)

Table 42: West Valley Power Plant Facility-Wide Emissions
UMPA West Valley Power Plant Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 10.09 162.06
VOC 1.47 18.33
4.13.4 RACT Analysis
The RACT evaluations were performed using data from UMPA WVPP, AOs and supporting
documentation, and Utah SIP Section IX, Parts H.11 and H.12. Various resources were evaluated to
identify all existing and potential controls and emission rates, including EPA’s RBLC; technical
documents, EPA fact sheets, applicable CTGs, and other applicable literature; state and federal
regulations; and other state SIPS. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 43.

UTAH DIVISION OF AIR QUALITY
76

Table 43: Utah Municipal Power Agency West Valley Power Plant
Utah Municipal Power Agency West Valley Power Plant
RACT
Section
#67

Emission Unit/Activity Pollutant RACT
Determination
Enforceability Comments
AO
Conditions
PM2.5 SIP
Conditions
4.1 & 4.2
Combustion Turbines

NOx
SCR,
water/steam
injection and
maintenance
of NOx
emissions at or
below 5 ppmv
for each
turbine.
(282-02)
#10, #17
H.12.o.i, ii, iii,
iv Current
operations
meet RACT,
no further
action
warranted.
4.2 VOCs
Good
combustion
practices and
oxidation
catalysts.
(282-02)
#14, #19 No
PM2.5
BACT TSD
5.068
Startup/Shutdown at
Combustion Turbines

NOx
BACT
determination:
limitation of
hours of
operation for
startup/shutd
own to limit
NOx,
alternative
operating
scenarios
included.
(282-02)
#19 No
No
additional
RACT
submitted
.
Current
operation
s meet
RACT, no
further
action
warranted
.
4.13.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for the UMPA WVPP. RACT evaluations showed that
additional add-on controls or limitations are not technically or economically feasible options at this time.
No additional RACT measures were identified, and all RACT determinations are already being

67 https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-002084.pdf
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UTAH DIVISION OF AIR QUALITY
77

implemented. Therefore, there are no additional implementation schedules or requirements for the
UMPA WVPP as required by this SIP revision.
4.14 University of Utah
4.14.1 Introduction
This section specifically serves as an evaluation of the University of Utah (U of U). In addition to
past BACT reports, the U of U submitted an additional RACT analysis for evaluation January 31, 2023.
Specific conditions for this SIP revision for the U of U can be found in Section IX, Part H.32.m.
4.14.2 Facility Process Summary
The U of U is a higher education institution in Salt Lake City. The U of U campus consists of
several different types of buildings and facilities, including classroom buildings, hospitals and clinics,
research facilities, and housing. The emission sources at the U of U are primarily boilers, comfort heating
equipment, emergency generator engines, and miscellaneous small VOC sources. Industrial high
temperature boilers that provide hot water for distribution heating systems are located in the two main
heating plants on campus: the Upper Campus High Temperature Water Plant (UCHTWP) and the Lower
Campus High Temperature Water Plant (LCHTWP). A cogeneration turbine with waste heat recovery unit
is also located at the LCHTWP.
4.14.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the U of U processes and equipment are summarized in Table
44. The 2017 actual emissions were used as the baseline emissions. The current PTE values for the U of
U were established by the most recent active AOs issued to the source.
• AO DAQE-AN103540030-22 issued December 22, 2022 (0030-22)

Table 44: University of Utah Facility-Wide Emissions
University of Utah Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 41.65 126.50
VOC 8.13 13.53
4.14.4 RACT Analysis
The RACT evaluations were performed using data from the U of U, AOs and supporting
documentation, and Utah SIP Section IX, Parts H.11 and H.12. Various resources were evaluated to
identify all existing and potential controls and emission rates, including EPA’s RBLC; technical
documents, EPA fact sheets, applicable CTGs, and other applicable literature; state and federal
regulations; and other state SIPS. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 45.

UTAH DIVISION OF AIR QUALITY
78

Table 45: University of Utah
University of Utah
RACT
Section
#69
Emission
Unit/Activity
Pollutant RACT
Determination
Enforceability Comments
AO
Conditions
PM2.5 SIP
Conditions
4.0 Building 302
UCHWTP
Boilers
VOCs Use of pipeline
quality natural
gas, good
combustion
practices, good
design, & proper
operation.
(0030-22)
I.5
H.12.p.iv. Current operations
meet RACT, no
further action
warranted.
NOx Boilers limited
to back-
up/peaking
boilers with
natural gas
limitations and
FGR.
(0030-22)
II.B.1.b
5.0 Building 303
LCHWTP
Boilers
NOx Boiler 4 required
to be
decommissioned
and replaced by
Boiler 9, use of
ULNB (9ppmvd)
on Boiler 9, &
use of LNBs and
FGR (9 ppmvd)
for boilers 6 and
7.
(0030-22)
II.b.2.a
H.12.p.i.,
H.12.p.ii.,
&
H.12.p.iii.
Current operations
meet RACT, no
further action
warranted.
VOCs Use of pipeline
quality natural
gas, good
combustion
practices, good
design, & proper
operation.
(0030-22)
I.5
No Current operations
meet RACT, no
further action
warranted.
6.0 Building 303
LCHWTP
Cogeneration
Plant
NOx SoLoNOx
burners and
compliance with
NSPS Subpart
KKKK.
(0030-22)
II.B.2.a
No Current operations
meet RACT, no
further action
warranted.

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VOCs Use of pipeline
quality natural
gas, good
combustion
practices, good
design, & proper
operation.
(0030-22)
I.5
7.0 Dual Fuel
Boilers
NOx LNBs on various
boilers; the use
of specialized
mixing heads
and mixing
assemblies.
(0030-22)
I.5 &
II.B.3.a
H.12.p.v. Current operations
meet RACT, no
further action
warranted.
VOCs Use of pipeline
quality natural
gas with diesel
fuel as backup,
good
combustion
practices, good
design, & proper
operation.
(0030-22)
I.5
No
8.0 Backup
Diesel Boiler
NOx Meet a NOx
emission rate of
30 ppm.
(0030-22)
I.5 &
II.B.3.a
No Current operations
meet RACT, no
further action
warranted. VOCs Use of diesel
fuel, good
combustion
practices, good
design, & proper
operation.
(0030-22)
I.5
No
9.0 Small Boilers VOCs Use of pipeline
quality natural
gas, good
combustion
practices, good
design, & proper
operation.
(0030-22)
II.B.1.b &
II.B.3.a
No Current operations
meet RACT, no
further action
warranted.
NOx LNBs on various
boilers.
(0030-22)
II.B.3.c
H.12.p.v
10.0 Diesel
Emergency
Generator
Engines
VOCs Proper
maintenance
and operation,
and compliance
with applicable
(0030-22)
I.5
No Current operations
meet RACT, no
further action
warranted.
NOx

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NSPS or MACT
requirements.
11.0 Natural Gas
Emergency
Generator
Engines
VOCs Use of pipeline
quality natural
gas, good
combustion
practices, good
design, proper
operation, and
compliance with
applicable NSPS
or MACT
requirements.
(0030-22)
I.5
No Current operations
meet RACT, no
further action
warranted.
NOx
12.0 Paint Booth
and Parts
Washer
VOCs Good
housekeeping
practices,
routine
inspections, &
compliance with
R307-351.
(0030-22)
I.5
No Current operations
meet RACT, no
further action
warranted.
12.0 Fuel Storage
Tanks
VOCs Good operating
and
maintenance
practices.
(0030-22)
I.5
No Current operations
meet RACT, no
further action
warranted.
N/A Ethylene
Oxide
Sterilizer
VOCs Preparing to
decommission.
(0030-22)
I.5
No Current operations
meet RACT, no
further action
warranted.
4.14.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for the U of U. RACT evaluations showed that additional
add-on controls or limitations are not technically or economically feasible options at this time. No
additional RACT measures were identified, and all RACT determinations are already being implemented.
Therefore, there are no additional implementation schedules or requirements for the U of U as required
by this SIP revision.
4.15 US Magnesium LLC
4.15.1 Introduction
This section specifically serves as an evaluation of US Magnesium LLC (US Magnesium) RACT.
UDAQ identified US Magnesium as a major stationary source with the potential to impact the ozone
formation in the NWF NAA. The UDAQ required US Magnesium to submit a RACT analysis under CAA
172(c)(6) Other Measures for all major stationary sources located outside a NAA but impacting the NAA,

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which applied to one source. US Magnesium submitted a NOx-specific RACT analysis for evaluation May
17, 2021, with a supporting VOC-specific RACT analysis submitted May 20, 2022, and an updated VOC-
specific RACT analysis submitted January 31, 2023. Specific conditions for this SIP revision for US
Magnesium can be found in Section IX, Part H.32.k. While US Magnesium was included in the RACT
process, the emissions from this facility were not included in the point source inventories found in
section 3 of this SIP revision as the facility was located outside of the NAA.
4.15.2 Facility Process Summary
US Magnesium operates a primary magnesium production facility at its Rowley plant located in
Tooele County. US Magnesium produces magnesium metal from the waters of the Great Salt Lake, using
a system of solar evaporation ponds to create a brine solution. This brine solution is purified and dried
to a powder in spray dryers. The powder is melted and further purified in the melt reactor before going
through an electrolytic process to separate magnesium metal from chlorine. The magnesium is then
refined and/or alloyed and cast into molds. The separated chlorine is combusted in the chlorine
reduction burner and converted into hydrochloric acid, which is removed through a scrubber train. The
chlorine generated at the electrolytic cells is collected and piped to the chlorine plant. The on-site
lithium carbonate plant recovers lithium from cell salt created through the magnesium plant production.
4.15.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the US Magnesium processes and equipment are
summarized in Table 46. The 2017 actual emissions were used as the baseline emissions. The current
PTE values for US Magnesium were established by the most recent active AOs issued to the source.
• AO DAQE-AN107160050-20 issued April 20, 2020 (0050-20)

Table 46: US Magnesium LLC Facility-Wide Emissions
US Magnesium LLC Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 1,061.59 1,260.99
VOC 660.26 894.25
4.15.4 RACT Analysis
The RACT evaluations were performed using data from US Magnesium, AOs, and supporting
documentation. Various resources were evaluated to identify all existing and potential controls and
emission rates, including EPA’s RBLC; technical documents, EPA fact sheets, applicable CTGs, and other
applicable literature; state and federal regulations; other state SIPS; and UDAQ’s Appendix A – PM2.5
serious SIP BACT for Small Sources. The RACT determinations for each emission unit or activity emitting
NOx and VOCs are provided in Table 47.

Table 47: US Magnesium RACT Determination

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US Magnesium LLC
RACT
Section
#70
Emission
Unit/Activity
Pollutant RACT
Determination
AO
Conditions
Comments
5.1 Turbines and
Duct Burners
VOCs Use of pipeline
quality natural
gas with fuel
oil as backup,
good
combustion
practices,
good design, &
proper
operation.
(0050-20)
I.4
Current operations meet RACT,
no further action warranted.
NOx Compliance
with a plant-
wide natural
gas
consumption
limit.
(0050-20)
II.B.1.b
5.2 Chlorine
Reduction
Burner
NOx Compliance
with a plant-
wide natural
gas
consumption
limit.
(0050-20)
II.B.1.b
Current operations meet RACT,
no further action warranted.
VOCs Use of pipeline
quality natural
gas, good
combustion
practices,
good design, &
proper
operation.
(0050-20)
I.4
5.3 Riley Boiler NOx Compliance
with a plant-
wide natural
gas
consumption
limit.
Installation of
flue gas
recirculation
required by
(0050-20)
II.B.1.b
Current operations meet RACT,
no further action warranted.

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January 1,
2028 under
SIP Section IX,
Part H.23.g.
VOCs Use of pipeline
quality natural
gas, good
combustion
practices,
good design, &
proper
operation.
(0050-20)
I.4
5.5 Hydrochloric
Acid Plant
Burner
VOCs Use of pipeline
quality natural
gas, good
combustion
practices,
good design, &
proper
operation.
(0050-20)
I.4
Current operations meet RACT,
no further action warranted.
NOx Compliance
with a plant-
wide natural
gas
consumption
limit.
(0050-20)
II.B.1.b
5.4 Diesel
Engines
VOCs Proper
maintenance
and operation,
compliance
with
applicable
MACT
requirements,
and
compliance
with a
horsepower-
hour
operational
limitation.
(0050-20)
I.4 &
II.B.4.b
Current operations meet RACT,
no further action warranted.
NOx

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5.6 Casting
House
VOCs Use of pipeline
quality natural
gas, good
combustion
practices,
good design, &
proper
operation.
(0050-20)
I.4
Current operations meet RACT,
no further action warranted.
NOx Compliance
with a plant-
wide natural
gas
consumption
limit.
(0050-20)
II.B.1.b
5.7 Lithium
Carbonate
Plant Boilers
& Burners
VOCs Use of pipeline
quality natural
gas, good
combustion
practices,
good design, &
proper
operation.
(0050-20)
I.4
Current operations meet RACT,
no further action warranted.
NOx ULNBs on
boilers and
LNBs on
burners;
compliance
with a plant-
wide natural
gas
consumption
limit.
(0050-20)
II.B.1.b &
II.B.12.d
VOC
RACT71
Boron Plant VOCs Installation of
a steam
stripper and
RTO system
that will
achieve 98%
control
efficiency by
October 1,
2024.
N/A Installation of a steam stripper
and RTO system by October 1,
2024, required by SIP Section IX,
Part H.32.k.

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Small
Source
BACT72
Fuel Storage
Tanks
VOCs Proper
maintenance
and operation.
(0050-20)
I.4
Current operations meet RACT,
no further action warranted.
Small
Source
BACT
Paint Booths VOCs Good
operating
practices and
compliance
with
consumption
and VOC
limitations.
(0050-20)
I.4,
II.B.11.a,
& II.B.11.d
Current operations meet RACT,
no further action warranted.

4.15.5 Conclusion of RACT Implementation
The UDAQ determined that the emission units/activities currently meet all RACT requirements,
and all other existing controls and emissions limitations are considered RACT for US Magnesium.
However, RACT evaluations showed that the installation of a steam stripper in series with a regenerative
thermal oxidizer (RTO) to control VOC emissions from the Boron Plant Process Wastewater Ponds is
technically feasible.
The UDAQ has determined that these controls are necessary for the NWF NAA to demonstrate
attainment of the 2015 8-hour ozone NAAQS as expeditiously as practicable. While the financial
feasibility of the identified controls may be beyond previously established RACT thresholds, the CAA
provides states with “discretion to require beyond-RACT reductions from any source” if those reductions
are necessary to “demonstrate attainment as expeditiously as practicable”. 73
The installation of a steam stripper with RTO on the Boron Plant Process Wastewater Ponds will
control emissions from this process by approximately 98% resulting in 161.70 tpy of VOC emissions
reductions. The steam stripper with RTO shall be installed and operational by October 1, 2024. All
requirements for the Boron Plant are incorporated into SIP Section IX, Part H.32.k. No other additional
RACT measures were identified, and all other RACT determinations are already being implemented.
4.16 Chevron Salt Lake Marketing Terminal
4.16.1 Introduction
This section specifically serves as an evaluation of Chevron Salt Lake Marketing Terminal
(Chevron Terminal). The emissions units at the Chevron Terminal were not included in the PM2.5 serious
SIP. At that time, UDAQ considered the Chevron Terminal as a separate source from the Chevron
Refinery. However, recent permitting actions have since established that the Chevron Terminal and
Chevron Refinery are considered one stationary source. Therefore, UDAQ requested a RACT analysis for
the emission units at the Chevron Terminal. Chevron Terminal submitted a RACT analysis for evaluation

72 https://documents.deq.utah.gov/air-quality/pm25-serious-sip/DAQ-2018-007161.pdf
73 80 FR 12279 & 83 FR 62998

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86

March 30, 2021, with supporting information submitted January 4, 2023. Specific conditions applicable
for this SIP revision for Chevron Terminal can be found in Section IX, Part H.32.b.
4.16.2 Facility Process Summary
The Chevron Terminal is a bulk gasoline terminal, which receives product by pipeline from the
Chevron Refinery, as well as ethanol and additives from outside vendors by truck and railcar. Products
are dispensed through the primary truck loading rack to cargo tank trucks where the product is
delivered to gasoline dispensing facilities. Storage tanks at the site store gasoline, ethanol, Transmix,
diesel fuel, water, additives, hydraulic fluid, motor oil, and jet fuel. Ethanol and other additives are
blended in line with refined products at the truck loading rack.
4.16.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from Chevron Terminal processes and equipment are summarized
in Table 48. The 2017 actual emissions were used as the baseline emissions. The current PTE values for
Chevron Terminal were established by the most recent active AOs issued to the source.
• AO DAQE-AN105560017-15 issued May 18, 2015 (0017-15)
Table 48: Chevron Salt Lake Marketing Terminal Facility-Wide Emissions
Chevron Salt Lake Marketing Terminal Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx N/A N/A
VOC 13.64 33.60
4.16.4 RACT Analysis
The RACT evaluations were performed using data from Chevron Terminal, AOs, and supporting
documentation. Various resources were evaluated to identify all existing and potential controls and
emission rates, including EPA’s RBLC; technical documents, EPA fact sheets, applicable CTGs, and other
applicable literature; state and federal regulations; and other state SIPS. The RACT determinations for
each emission unit or activity emitting NOx and VOCs are provided in Table 49.

Table 49: Chevron Salt Lake Marketing Terminal
Chevron Salt Lake Marketing Terminal
RACT
Section
#74
Emission
Unit/Activity
Pollutant RACT
Determination
AO
Conditions
Comments
2.2.1

Transport
Loading Rack

VOCs

Vapor recovery
unit with carbon
adsorption in
compliance with
MACT Subpart R.

(0017-15)
II.B.1.b &
II.B.1.c
Current
operations
meet RACT,
no further
action
warranted.

74 https://documents.deq.utah.gov/air-quality/planning/air-quality-policy/DAQ-2022-011292.pdf

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2.2.3

Fugitive
Emissions

VOCs

LDAR in
accordance with
MACT Subpart R
and NSPS Subparts
XX and Kb.

(0017-15) I.5
2.2.1

Specialty Rack

VOCs

Bottom loading
with good work
practice standards.

(0017-15) I.5
& II.B.1.c
Current
operations
meet RACT,
no further
action
warranted.

2.2.2

Storage Tanks

VOCs

Top-submerged or
bottom loading of
tanks; good design
methods and
operating
procedures; and
compliance with
applicable NSPS
Subpart Kb
requirements.

(0017-15)
II.B.1.c
Current
operations
meet RACT,
no further
action
warranted.

4.16.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for the Chevron Terminal. RACT evaluations showed that
additional add-on controls or limitations are not technically or economically feasible options at this time.
No additional RACT measures were identified, and all RACT determinations are already being
implemented. Therefore, there are no additional implementation schedules or requirements for the
Chevron Terminal as required by this SIP revision.
4.17 Holly Energy Partners Woods Cross Terminal
4.17.1 Introduction
This section specifically serves as an evaluation of Holly Energy Partners Terminal (Holly
Terminal). The emissions units at the Holly Terminal were not included in the PM2.5 serious SIP. At that
time, UDAQ considered the Holly Terminal as a separate source from the main refinery. However, recent

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permitting actions have since established that the Holly Terminal and Woods Cross Refinery are
considered one stationary source. Therefore, UDAQ requested a RACT analysis for the emission units at
the Holly Terminal. Holly Terminal submitted a RACT analysis for evaluation February 12, 2021. Specific
conditions applicable to this SIP revision for Holly Terminal can be found in Section IX, Part H.32.e.
4.17.2 Facility Process Summary
The Holly Terminal is a petroleum products loading facility located in Woods Cross. The terminal
consists of a loading rack and a soil remediation system. The bulk terminal is used by the Holly Terminal
to load gasoline and diesel products into tanker trucks. The Holly Terminal receives gasoline, diesel, and
jet fuel via pipeline from the HF Sinclair Woods Cross Refinery. The petroleum products are loaded into
tanker trucks for offsite transportation. The Holly Terminal doesn’t have aboveground storage tanks.
4.17.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the Holly Terminal processes and equipment are summarized
in Table 50. The 2017 actual emissions were used as the baseline emissions. The current PTE values for
the Holly Terminal were established by the most recent active AOs issued to the source.
• AO DAQE-AN101230023B-07 issued October 17, 2007 (0023B-07)
• AO DAQE-AN101230034-10 issued November 18, 2010 (0034-10)
Table 50: Holly Energy Partners Woods Cross Terminal Facility-Wide Emissions
Holly Energy Partners Woods Cross Terminal Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx 0.32 2.53
VOC 2.14 9.13

4.17.4 RACT Analysis
The RACT evaluations were performed using data from Holly Terminal, AOs, and supporting
documentation. Various resources were evaluated to identify all existing and potential controls and
emission rates, including EPA’s RBLC; technical documents, EPA fact sheets, applicable CTGs, and other
applicable literature; state and federal regulations; and other state SIPS. The RACT determinations for
each emission unit or activity emitting NOx and VOCs are provided in Table 51.

Table 51: Holly Energy Partners Woods Cross Terminal
Holly Energy Partners Woods Cross Terminal
RACT
Section
#75
Emission
Unit/Activity
Pollutant RACT
Determination
AO
Conditions
Comments

75 https://documents.deq.utah.gov/air-quality/planning/air-quality-policy/DAQ-2022-011295.pdf

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5.1 Transport
Loading Rack
VOCs Vapor recovery
unit with carbon
adsorption in
compliance with
MACT Subpart
CC; vapor
combustion unit
backup.
(0023B-
07) #7, #9,
& #16
Current operations meet
RACT, no further action
warranted.
5.2 Fugitive
Emissions
VOCs LDAR required by
NSPS Subpart
VVa.
(0023B-
07) #12
Current operations meet
RACT, no further action
warranted.
5.3 Soil
Remediation
System
VOCs Thermal/catalytic
oxidizer.
(0034-10)
I.5; II.B.1.b
Current operations meet
RACT, no further action
warranted.

4.17.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for the Holly Terminal. RACT evaluations showed that
additional add-on controls or limitations are not technically or economically feasible options at this time.
No additional RACT measures were identified, and all RACT determinations are already being
implemented. Therefore, there are no additional implementation schedules or requirements for the
Holly Terminal as required by this SIP revision.
4.18 Tesoro Logistics Operations LLC Truck Loading Rack and Remote Tank Farm
4.18.1 Introduction
This section specifically serves as an evaluation of Tesoro Logistics Operations LLC Truck Loading
Rack and Remote Tank Farm (Tesoro TLR). The emissions units at the Tesoro TLR were not included in
the PM2.5 serious SIP. At that time, UDAQ considered the Tesoro TLR as a separate source from the main
refinery. However, recent permitting actions have since established that the Tesoro TLR and Marathon

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Refinery are considered one stationary source. Therefore, UDAQ requested a RACT analysis for the
emission units at the Tesoro TLR. Tesoro TLR submitted a RACT analysis for evaluation March 31, 2021,
with an updated RACT analysis submitted January 31, 2023. Specific conditions applicable to this SIP
revision for Tesoro TLR can be found in Section IX, Part H.32.j.
4.18.2 Facility Process Summary
The Tesoro TLR is a bulk gasoline terminal, which receives products from the Marathon Refinery.
Products are dispensed through the primary truck loading rack to cargo tank trucks where the product is
delivered to gasoline dispensing facilities. Storage tanks at the site store gasoline, diesel fuel, kerosene,
heavy oils, and fuel additives.
4.18.3 Facility Baseline Actual Emissions and Current PTE
The baseline and current PTE from the Tesoro TLR processes and equipment are summarized in
Table 52. The 2017 actual emissions were used as the baseline emissions. The current PTE values for the
Tesoro TLR were established by the most recent active AOs issued to the source.
• AO DAQE-AN156590008-18 issued March 12, 2018 (0008-18)
Table 52: Tesoro Logistics Operations LLC TLR and RTF Facility-Wide Emissions
Tesoro Logistics Operations LLC TLR and RTF Facility Emissions
Pollutant Baseline Emissions
(TPY)
PTE
(TPY)
NOx N/A N/A
VOC 18.24 107.92
4.18.4 RACT Analysis
The RACT evaluations were performed using data from Tesoro TLR, AOs, and supporting
documentation. Various resources were evaluated to identify all existing and potential controls and
emission rates, including EPA’s RBLC; technical documents, EPA fact sheets, applicable CTGs, and other
applicable literature; state and federal regulations; and other state SIPS. The RACT determinations for
each emission unit or activity emitting NOx and VOCs are provided in Table 53.

Table 53: Tesoro Logistics Operations LLC TLR and RTF
Tesoro Logistics Operations LLC Truck Loading Rack and Remote Tank Farm
RACT
Section
#76
Emission
Unit/Activity
Pollutant RACT
Determination
AO
Conditions
Comments

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5.1 Transport
Loading Rack
VOCs Vapor
recovery unit
with carbon
adsorption in
compliance
with MACT
Subpart CC.
(0008-18)
II.B.1.l
Current operations meet RACT,
no further action warranted.
4.1 Fugitive
Emissions
VOCs Enhanced
LDAR required
by NSPS
Subpart GGGa
and
maintenance
vent
monitoring.
(0008-18)
I.7
Current operations meet RACT,
no further action warranted.
6.1 Fixed Roof
Tanks
VOCs Good design
methods and
operating
procedures;
closed vent
system to a
carbon
adsorber on
OWS Tank.
(0008-18)
I.7;
II.B.1.c -
II.B.1.k
Current operations meet RACT,
no further action warranted.
7.1 Internal
Floating
Roof Tanks
VOCs Good design
methods and
operating
procedures;
compliance
with
applicable
NSPS Subpart
Kb
requirements;
and tank
degassing
requirements.
(0008-18)
I.7;
II.B.1.c -
II.B.1.k
Current operations meet RACT,
no further action warranted.

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4.18.5 Conclusion of RACT Implementation
The emission units/activities currently meet all RACT requirements, and the existing controls
and emissions limitations are considered RACT for the Tesoro TLR. RACT evaluations showed that
additional add-on controls or limitations are not technically or economically feasible options at this time.
No additional RACT measures were identified, and all RACT determinations are already being
implemented. Therefore, there are no additional implementation schedules or requirements for the
Tesoro TLR as required by this SIP revision.
4.19 CTG and ACT
For all sources located within the NWF NAA examined as part of this RACT analysis, any
applicable CTGs or ACTs were found to have been implemented to the relevant source through existing
AOs or SIP conditions. Any published CTG or ACT not enacted within the NAA boundary results from the
fact that the NWF does not have sources in which those CTGs are applicable. Details regarding this
analysis and additional information about source specific CTG and ACT applicability can be found in the
CTG VOC Source Categories Analysis TSD.77
Thus, the UDAQ conducted no further RACT analysis for CTG source categories not included in
AOs or SIP conditions as there are not sources subject to those CTGs within the NWF NAA. Therefore,
this SIP revision has met the CTG requirements as required under CAA Section 182(b)(2).
4.20 RACT Conclusions
Upon completion of RACT analysis for each of the major industrial sources located within the
NWF NAA, or nearby in the case of US Magnesium, the UDAQ has concluded that the controls identified
in Table 54, with the corresponding emission limitations included in Utah SIP Section IX, Part H.31 and
H.32, are necessary for the NWF NAA to demonstrate attainment of the 2015 8-hour ozone NAAQS as
expeditiously as practicable. While the financial feasibility of some of these controls may be beyond
previously established RACT thresholds, the CAA provides states with “discretion to require beyond-
RACT reductions from any source” if those reductions are necessary to “demonstrate attainment as
expeditiously as practicable”. 78 The precedent for the requirement of “beyond-RACT” controls for an
ozone NAA demonstrating attainment at the earliest achievable date has been previously established in
2001,79 and further upheld in 2009.80
The implementation timeline of controls identified in Table 54 are beyond the implementation
deadline of January 1, 202381 and therefore will not count towards RFP under this SIP revision. However,
the state of Utah has ongoing obligations under Section 182 of the CAA to demonstrate attainment of
the NAAQS. The timing of compliance for states meeting statutory deadlines established in the CAA does
not impact or nullify those obligations for future SIP revisions. Thus, a state submitting a SIP revision
late, or meeting 182(b)(2) requirements late, does not negate the obligations imposed by the CAA. As a
result, the UDAQ has determined that the implementation of the controls identified in Table 54 are

77 NWF CTG VOC Source Categories Analysis: https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-005467.pdf
78 80 FR 12279 & 83 FR 62998
79 66 FR 26914
80 74 FR 1927
81 87 Fed. Reg. 60,897.

UTAH DIVISION OF AIR QUALITY
93

required to be implemented on the most expeditiously practicable timelines to comply with these
ongoing CAA obligations.
While the controls identified in Table 54 have been determined to be beyond-RACT, the UDAQ
has concluded that these controls meet the definition of reasonable when considering their cost
effectiveness for controls considered beyond-RACT. This determination was made when examining
three variables that impact what constitutes reasonable including: 1) the regulatory landscape of the
NWF NAA (i.e. availability of control options), 2) other NAA determination of cost thresholds, 3)
appropriate adjustments for inflationary and other price pressures.
First, as noted in sections 5 and 7 of this SIP revision, Utah has previously implemented an
extensive array of emission reduction strategies at the BACT threshold while the state worked to
address wintertime PM2.5 pollution. These emission reductions target the same precursor emissions for
ozone, i.e. NOx and VOCs. As a result, there are exceedingly few control options available for the State to
implement at this time in the regulatory landscape of the NWF. In essence, the supply of available
controls is exceptionally low, while the demand to implement controls to comply with CAA
requirements is high. This same economic reality—what is considered a reasonable cost in one area will
be different than another area based on supply and demand— is seen in a wide array of economic
activities, such as housing. Therefore, it is reasonable to conclude that an appropriate cost threshold for
controls in the NWF NAA would be higher than that seen in an area with greater control options
available to it. This same reasoning follows that a reasonable cost threshold would be more similar to a
cost threshold seen in an NAA with fewer control options available. Further, a recent analysis conducted
by the UDAQ examining the cost effectiveness of emissions reduced from incentive programs identified
a similar scenario, with the cost to reduce emissions increasing as a result of previously implemented
incentive programs. In short, as programs (incentive or regulatory) reduce emissions from older, dirtier
equipment, the remaining pool of emissions sources are relatively cleaner, and thus the emission
reductions are more expensive per ton of pollutant removed.
Second, the UDAQ compared and contrasted the RACT cost thresholds with a number of other
NAAs, and compared cost thresholds for both RACT and BACT implemented controls. While many
contrasting NAAs that have recently implemented RACT determined an appropriate cost thresholds
between $5,000 - $10,000 per ton of pollutant removed,82 these areas are doing so with a wider array of
emission reduction strategies available to them. In contrast, the UDAQ examined BACT cost thresholds
in areas with more similar regulatory frameworks in place to see what the higher end of cost
effectiveness could be considered reasonable. The Division found instances of BACT cost thresholds near
$43,000 per ton of VOC and $41,000 per ton of NOx emission reductions.83 While these higher end
estimates are considered BACT, and thus represent a more stringent standard, the Division has
concluded that, given the existing regulatory framework in place in the NWF and the similarities
between these higher cost threshold NAAs, that a RACT cost threshold of approximately $10,000 per ton
of pollutant removed below that reported on the high end is reasonable for the NWF. The controls
outlined in Table 54 all fall near or below this threshold. Additionally, the UDAQ identified instances in
which a cost threshold of $10,000 was determined reasonable for Regional Haze SIPs.84 It’s worth noting
that Regional Haze SIPs are developed to meet visibility standards, not health-based standards as in this

82 Approval and Promulgation of Air Quality Implementation Plans; Pennsylvania; Reasonably Available Control Technology Determinations for Case-by-Case
Sources Under the 1997 and 2008 8-Hour Ozone National Ambient Air Quality Standards, 85 Fed. Reg. 66,484, 66,486 (Oct. 20, 2020) (examples of benchmarks from
several other states examined by Pennsylvania).
83 2022 South Coast Air Quality Management District BACT Maximum Cost Effectiveness Values.
84 Oregon Regional Haze State Implementation Plan, for the period 2018 – 2028, available at https://www.oregon.gov/deq/rulemaking/Pages/rhsip2028.aspx.

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moderate ozone SIP. The Division believes that a reasonable threshold for a control used to protect
human health should be considerably higher than that determined reasonable for protecting visibility.
Lastly, the UDAQ also considered inflationary forces when determining a reasonable cost-
effectiveness threshold. Since 2000, the United States has seen a cumulative price increase associated
with inflationary pressures of 77.18%.85 Similar upward price pressures have been observed in other
parts of the economy that impact the price of pollution controls. For example, the building cost index for
construction for nonresidential buildings over the same period cited for inflation above (2000 – 2023)
has risen from ~50 to just over 130—a 160% increase.86 If inflationary pressures are not taken into
consideration over time when determining reasonable cost-effectiveness thresholds, the ever-increasing
costs associated with building and installing controls would result in a diminished ability for responsible
air agencies to identify and require effective controls. These same inflationary economic forces have
been realized elsewhere in the regulatory world, resulting in an increase in the statutory civil monetary
penalties for violations as enforced by the EPA for the CAA violations rising from $25,000 in 1991 to
$55,808 in 2023 for each day of continued noncompliance.
When all three of these factors (existing regulatory framework, similar NAA thresholds, and
inflationary pressures) are taken together, the UDAQ has determined that the controls outlined in Table
54 are reasonable for an area in which beyond-RACT controls are necessary to attain the standard.87 A
SIP is intended to be a plan that matches the unique characteristics of each NAA, which is why the
responsible air agency has primacy to develop and implement the plan it determines best meets the
unique challenges of its air shed. When considering appropriate cost thresholds for a NAA, it is
important to recognize that the cost effectiveness for controls for that air shed will also be unique to the
NAA in question.

Table 54: Controls identified by RACT analysis for the NWF NAA.
Source Control Part H
Reference
Implementation
Timeline
Emission
Reductions
Tesoro Refining &
Marketing
Company LLC
Marathon
Refinery
NOx emission limits on
cogeneration turbines
with heat recovery
steam generation CG1
and CG2
XI.H.32.j.b October 1, 2028 68.78 tpy NOx
Tesoro Refining &
Marketing
Company LLC
Marathon
Refinery

Replacement of
wastewater API
separator and DAF unit
with a closed vent to
carbon adsorption
controls
XI.H.32.j. d December 31,
2025
10.0 tpy VOCs
Tesoro Refining &
Marketing
Company LLC
Secondary seal
installation on Tank
321
XI.H.32.j.c May 1, 2026 2.30 tpy VOCs

85 Bureau of Labor Statistics Consumer Price Index (CPI), available at https://www.bls.gov/cpi/.
86 Construction Analytics, Construction Inflation 2023, available at https://edzarenski.com/2022/12/20/construction-inflation-2023/.
87 42 U.S.C § 7545(d)(1); 40 CFR § 19.4.

UTAH DIVISION OF AIR QUALITY
95

Marathon
Refinery

US Magnesium LLC Steam stripper in
series with RTO
XI.H.32.k October 1, 2024 161.70 tpy VOCs

Based on all available data including the examination of past submitted BACT reports, newly
submitted RACT analyses, and by requiring the implementation of “beyond-RACT” controls as identified
in Table 54, the NWF NAA has met all RACT criteria as required under CAA Section 182(b)(2) for this SIP
revision. Furthermore, the implementation of technologically feasible “beyond-RACT” controls
demonstrates not only completion of RACT requirements, but that the area will demonstrate attainment
as expeditiously as practicable.
4.21 Nonattainment New Source Review (NNSR)
NNSR is a CAA permitting program which requires industrial facilities to install modern pollution
control equipment when they are built, or when making a change that increases emissions significantly.
The purpose of an NNSR program is to protect public health and the environment, even as new
industrial facilities are built, by ensuring that air quality does not worsen in the NAA and air quality is not
significantly degraded. This is accomplished through preconstruction permitting.
Utah Administrative Rule R307-403; Permits: New and Modified Sources in Nonattainment and
Maintenance Areas,88 implements federal NAA permitting programs for major sources as required by 40
CFR § 51.165 and contains new source review provisions for some non-major sources in the ozone
NAAs. Rule R307-403 is applicable any new major stationary source or major modification that is major
for the pollutant or precursor pollutant for which the area is designated nonattainment if the stationary
source or modification is located anywhere in the designated NAA. This includes requirements that a
major stationary source in the NWF NAA obtain a ratio of total actual emission reductions of VOCs
compared to the emission increase of VOCs of at least 1.15:1 prior to commencement of operations and
permitting by the UDAQ. EPA determined that rule R307-403 meets the requirement for nonattainment
new source review under 40 CFR § 51.131489 on February 02, 202290 Therefore, this SIP revision
adequately addresses the CAA NAA requirements for NOx and VOC emission offsets.

88 Utah Admin. Code r. R307-403.
89 40 CFR § 51.1314 New source review requirements.
90 Approval and Promulgation of Implementation Plans; Utah; Emissions Statement Rule and Nonattainment New Source Review Requirements for the 2015 8-
Hour Ozone National Ambient Air Quality Standard for the Uinta Basin, Northern Wasatch Front and Southern Wasatch Front NAAs, 87 Fed. Reg. 5,435 (Feb. 1,
2022).

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Chapter 5 - Reasonably Available Control Measures (RACM) Analysis
5.1 Overview
CAA section 172(c)(1) requires states to implement all RACM as expeditiously as practicable,
including RACT, to meet both RFP requirements and to demonstrate attainment of the NAAQS. The CAA
requires RACM to be implemented for point, area, non-road, and on-road sources categories to meet
the attainment standard.
The general approach to the RACM analysis is to evaluate control measures that have been
implemented at the federal level, in other states and other local air districts and, if reasonable and
practicable, to implement the controls to help the area attain the ozone standard. A RACM analysis
determines potential control measures for each source category by considering the following
requirements:
• technological feasibility of the control measure,
• economic feasibility of the control measure,
• if the control measure would cause substantial widespread and long-term adverse impacts,
• if the control measure is absurd, unenforceable, or impracticable, and
• if the control measure can advance the attainment date by at least one year.
UDAQ conducted a RACM analysis by analyzing the following materials:
• EPA guidance documents and regulations including:
o CTG,
o ACT,
o Ozone Transport Commission model rules.
• A comparison of existing Utah administrative rules to other EPA SIP-approved rules of the three
western air districts that were moderate nonattainment for the 2008 ozone standard. The
rationale for this comparison is that the selected air districts have already implemented ozone
controls approved by EPA. The three air districts are Imperial County, CA, Mariposa County, CA,
and Phoenix-Mesa (Maricopa County), AZ. These NAAs were selected for comparison since they
have comparable climatic conditions to those experienced in the NWF NAA during summer and
similar industrial activities present in the NWF NAA. Each area has served as a basis for RACT
and RACM comparisons for other ozone NAAs, hence emission reduction strategies adopted in
these areas serve as a base for many other current ozone NAAs.
• Lastly, an evaluation of newly identified technological and economically feasible controls, or if
enhancement of existing controls were available.
The RACM analysis for the NWF NAA examined control measures for all potential VOC and NOx
emission sources. As part of this analysis, UDAQ reviewed existing Utah administrative rules, many of
which were implemented as part of the Salt Lake PM2.5 serious SIP and were developed under the
regulatory guidelines of best available control measures (BACM) which allow for more stringent
measures to be implemented than those conforming to RACM. The rules adopted under the BACM
approach for state efforts to address PM2.5 pollution include 24 VOC-related administrative rules, which
are identified in Table 55. Furthermore, as the implementation rules under PM2.5 allow for the
implementation of emission reduction strategies beyond the attainment dates, the VOC emission

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reduction rules implemented during the PM2.5 SIP were not constrained by timelines and further
contribute to the exhaustive list of existing regulations in the NWF NAA. As the requirements for BACM
are significantly more stringent than for RACM, the majority of this analyses concluded that current
control measures are as, or more stringent than, the requirements for the moderate ozone SIP.

Table 55: Existing area source VOC rules in the NWF NAA91
Rule Name
R307-211 Emission Standards: Emission Controls for Existing Municipal Solid Waste Landfills
R307-230 NOx Emission Limits for Natural Gas-Fired Water Heaters
R307-303 Commercial Cooking
R307-304 Industrial Solvent Use
R307-328 Gasoline Transfer and Storage
R307-335 Degreasing
R307-341 Cutback Asphalt
R307-342 Adhesive and Sealants
R307-343 Emission Standards for Wood Furniture Manufacturing Operations
R307-344 Paper, Film & Foil Coating
R307-345 Fabric & Vinyl Coating
R307-346 Metal Furniture Surface Coating
R307-347 Large Appliance Surface Coating
R307-348 Magnet Wire Coating
R307-349 Flat Wood Panel Coating
R307-350 Miscellaneous Metal Parts & Products Coating
R307-351 Graphic Arts
R307-352 Metal Containers, Closure & Coil Coating
R307-353 Plastic Parts Coating
R307-354 Auto Body Refinishing
R307-355 Control of Emissions from Aerospace Manufacturing & Rework Facilities
R307-356 Appliance Pilot Light
R307-357 Consumer Products
R307-361 Architectural Coatings
5.2 RACM Analysis
To evaluate the VOC and NOX sources in the NWF NAA, UDAQ first evaluated the 2017 baseline
emission inventory described in section 3, examining emission categories with the highest emissions
contributions first, then proceeding to examine smaller emission categories, in an attempt to identify
the most impactful strategies first. Thus, Tables 56 and 57, which overview the results of UDAQ’s RACM
analysis, are presented in descending order of the magnitude of emission category, as is the
corresponding TSD for this analysis.92 Next, the UDAQ identified control techniques currently in place for

91 All these rules are found in the Utah Administrative Code.
92 Northern Wasatch Front Area Source Reasonable Available Control Measures (RACM) Analysis for Ozone Control. Technical Support ing Document (TSD).
https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001246.pdf

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source categories and determine if existing controls and rules are up to date with federal guidance and
other states moderate ozone NAA rules.

Table 56: VOC RACM Assessment Summary
Source Category Utah Existing Rules/Statute and
Federal Rules
Comments
Solvent,
Consumer/commercial Use
Products
R307-357 Consumer Products R307-357 is the most current OTC
model rule, no further action
warranted
Solvent, Graphic Arts R307-351 Graphic Arts UDAQ worked closely with the
national printing trade association to
derive a BACM rule that would be in
line with printing rules found in the
most stringent California air districts.
No further analysis warranted.
Surface Coating, Industrial
Maintenance*
Surface coating rules R307-
343,344, 345,346,
347,348,349,350,352,353,354
and 355.

Surface Coatings, Traffic
Markings –
R307-361 Architectural Coatings
Most current control strategies for
surface coating and deemed to be
BACM by UDAQ.

R307-361 is the most current OTC
model rule and deemed to be BACM
by UDAQ.
Chemical Stripper R307-304 Solvent Cleaning
R307-335 Degreasing
UDAQ created the new rule R307-304
by removing sections of R307-335, in
which the applicability was
dramatically lowered, and a low vapor
pressure solvent option was added.
UDAQ determined that R307-304 was
BACM. No further analysis warranted.
Surface Coatings,
Architectural
R307-361 Architectural Coatings R307-361 is the most current OTC
model rule, no further action
warranted
Gas Pipelines 40 CFR 49 Subtitle B U.S. Dept. of Transportation is
responsible for pipeline safety and
spill prevention. No further action
warranted.
Asphalt R307-341 Cutback Asphalt Imperial and Maricopa counties
require lower VOC limits which were
not considered in this evaluation for
safety reasons. Reducing the VOC
content requires the asphalt to be
heated at a higher temperature
leading to possible flashing and
increase fuel usage negating any
VOC reductions.
Industrial Bakery

UDAQ issued a proposed rule for
public comment in 2016. Commenters
submitted documentation that the
estimated cost would be at least
$19,000/ton, requiring double-walled
stainless-steel stack plus catalytic

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oxidation of ethanol. High capital cost
would require a rule with high
applicability threshold that would
preclude regulating most bakeries that
comprise these emissions. No further
action warranted.
Residential & Commercial
Portable Gas Cans
Evaporation/Spillage etc.
40 CFR Part 59, Subpart F,
Control of Evap. Emission from
New & In-use Portable Fuel
Containers
No further action warranted
Gas Under Ground
Storage Tank

DAQ enforces Federal UST
regulation. No further action
warranted.

Waste Disposal, Treatment,
and Recovery;
Composting;100% Green
Waste
R315-312 Recycling and
Composting Facility Standards
Composting operations are managed
by the Utah Solid Waste Division.
R315-312 includes facility and
material management requirements
to reduce air, soil and groundwater
impairment. The 3 comparative air
districts do not have air quality rules
for compost operations. No further
action warranted.
Leaking Underground
Storage Tanks
Title 19 Chapter 6 Part 4,
Underground Storage Tank Act
UDEQ enforces the EPA UST
regulation, no further action
warranted
Pesticide Application,
Commercial/Consumer
(FIFRA)
R307-357 Consumer Products R307-357 is the most current OTC
model rule, no further action
warranted
Fuel Gas/Gasohol Bulk
Plants
R307-328 Gasoline Transfer and
Storage
Maricopa County has additional EPA
SIP rules for gasoline transfer and
storage based upon federal stage 1
vapor recovery guidance. An
evaluation of Maricopa County’s rules
with Utah’s determined that no
additional control technique would
be beneficial, and our current rules
associated with these processes were
determined to be BACM.

Landfills R307-221 Emission Standards:
Emission Controls for Existing
Municipal Solid Waste Landfills
No further action warranted.
Combustion, Natural Gas,
Residential
R307-356 Appliance Pilot Light R307-356 prohibits appliance from
utilizing a pilot light thereby reducing
VOC’s. No further action warranted.

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100

Gas Stage 1 R307-328 Gasoline Transfer and
Storage
Refer to discussion in section 5.2.1
Commercial Cooking Researchers in California have
been unable to identify cost
effective technology for this
emission source. Known control
measures have a high capitol cost
(>$50k) and demanding
maintenance such that the
removal cost would likely exceed
$20K/ton. Prohibitive cost would
shutter most sources. No further
action warranted.

Livestock Production

According to local USDA
representatives, most Utah producers
use National Resource Service best
management practices to protect soil,
water and air. No further action
warranted.

Sewer Treatment in Publicly
Owned Treatment Works
(POTW)
Clean Water Act: all POTW’s have
to report to EPA VOC
concentrations in discharges.
All major POTW’s meet Best Available
Technology, no further action
warranted.
Consumer and Commercial,
Miscellaneous Products
R307-357 Consumer Products R307-357 is the most current OTC
model rule, no further action
warranted
Fuel, Jet, Stage 1
(Storage)
Regulated under 40 CFR Subpart
Kb
Not technically feasible for jet fuel due
to low vapor pressure (0.125 psi). No
further action warranted.

Fires, Structural

Uncontrollable, no further action
warranted.

Backyard BBQ

Statutory Exemption, no further action
warranted.

Dairy and Beef Cattle
Composite

According to local USDA
representative, most Utah producers
use national conservation best
management practices.

Gas Tank Truck Transport R307-328 Gasoline Transfer and
Storage
Refer to discussion in section 5.2.1
Solvent, Dry Cleaning

Solvent dry cleaners use no transfer
machines that eliminate vapor loss
during transfer from washing to
drying. Additional built-in controls
include refrigerated condensers.
Some units also include built-in stills

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to further recover vapors. No further
controls would be feasible. No further
analysis warranted.

Poultry According to the Utah Farm Bureau,
operations apply best management
practices to maintain healthy stock.

Fuel, Jet, Stage 2
(Dispensing)

Regulated under 40 CFR Subpart
CC or Subpart R
Not technically feasible for jet fuel due
to low vapor pressure (0.125 psi). No
further action warranted.

Commercial Cooking -
Conveyorized Charbroiling
R307-303 Commercial Cooking R307-303 requires all units to utilize
catalytic oxidizers. UDAQ and a
nonprofit environmental group
worked together to fund and install
catalysts in all units in the Wasatch
Front. No further action warranted.
Industrial Boiler Liquid
Propane Gas (LPG)

No known control measures. Source
may require permit with conditions
under R307-401.
LPG Fuel

No known control measures exist, no
further action warranted.

Fires, Vehicle

Uncontrollable, no further action
warranted.

Combustion, Natural Gas,
Industrial Boilers and IC
Engines

No known control measures exist.
Source may require permit conditions
under air quality permitting R307-401-
4(3) requiring low-NOx burners.

Commercial/institutional
wood Fuels

There are no reasonably cost-
effective control strategies for this de
minimis emission. No further action
warranted.

Residential Oil Fuel

No known control exists, no further
action warranted.

Cremation, Human and
animal

Catalytic oxidizer control cost would
readily exceed $15k/ton, an
unreasonable cost for a de minimis
emission. No further action warranted.

Commercial/institutional
Kerosene Combustion

No known control, no further action
warranted.

Aircraft/Rocket Engine
Firing and Testing

Uncontrollable event for aircraft
maintenance/testing (no rocket
engine). No further action warranted.

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102

Solvents; Hot Mix Asphalt NEW Administrative Rule:
R307-313; VOC and Blue Smoke
Controls for Hot Mix Asphalt
Plants
The UDAQ has identified blue smoke
controls reducing VOC emissions
associated with blue smoke from Hot
Mix Asphalt plants being RACM. As a
result, the Utah Air Quality Board has
adopted Utah Administrative Rule
R307-313 to fulfill this requirement.
*Surface Coating, Industrial Maintenance: EPA has aggregated coatings of the following surfaces: wood
furniture, paper, film, foil, fabric, vinyl, metal furniture, large appliances, magnet wire, wood panel,
metal parts, metal containers, plastic parts, autobody and aerospace parts.

Table 57: NOX RACM Assessment Summary
Source Category Utah Existing
Rules/Statute and Federal
Rules
Comments
Combustion, Natural
Gas
R307-356 Appliance Pilot
Light.

R307-230 NOx Emission
Limits for Natural Gas-Fired
Water Heaters

PROPOSED: R307-315 &
R307-316
Prohibits the sale of appliance pilot lights (with
the exception of water heaters) after January 1,
2014. A Canadian study determined that a gas
fireplace pilot light accounts for 48% of the
annualized gas usage for the appliance.
Reduced gas consumption translates to a
reduction in PM2.5, VOC, NOx, SOx and NH3. We
are not aware of other comparable rules.

Ultra-low NOx water heaters reduce emissions to
10 ng/Joule for residential units and slightly
higher limits for commercial units. R307-230 is
consistent with the most stringent California
rules. No further action warranted.

The UDAQ has identified ultra-low NOx burners
(9 ppmv) as being RACM in most instances when
applied to replacement of end-of-life equipment
or replacement burners. Some instances,
particularly for high MMBtu units, may exceed
RACM requirements and require regulatory
flexibility.

UDAQ is proposing the adoption of
administrative rules R307-315 and R307-316 to
fulfill this RACM requirement.

Combustion, Natural
Gas, Commercial &
Institutional Boilers
and IC Engines

May be subject to air quality permitting. R307-
401-4(3) may apply requiring low-NOx burners.

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103

Industrial Boiler LPG

May be subject to air quality permitting
depending on size of emission sources.

Combustion,
Industrial, Distillate
Oil, All IC Engines
May be subject to air quality permitting
depending on size of emission sources.

Combustion,
Commercial,
Institutional LPG

No known control.

Combustion,
Industrial, Distillate
Oil, All Boilers
May be subject to air quality permitting. R307-
401-4(3) may apply requiring low-NOx burners
depending on the size of emission source.

Residential LPG Fuel

No known control.

Combustion, Natural
Gas, Industrial Boilers
and IC Engines

May be subject to air quality permitting. R307-
401-4(3) may apply requiring low-NOx burners.

Commercial,
institutional wood
Fuels
There are no reasonably cost-effective control
strategies for this de minimis emission. No further
action warranted.

Backyard BBQ

Statutory Exemption, no further action warranted.

Structural fires

Uncontrollable

Residential Oil Fuel

No known control, no further action warranted.

Waste Disposal, Open
Burning, Yard Waste
and Household Waste
R307-202, General Burning
regulates yard waste
burning by permit and
prohibits household waste
burning by homeowners.
No further action warranted.
Cremation, Human
and animal

Catalytic oxidizer control cost would readily
exceed $15k/ton, an unreasonable cost for a de
minimis emission. No further action warranted.

Combustion,
Kerosene

No known control, no further action warranted.

Aircraft/Rocket
Engine Firing and
Testing

Uncontrolled event for aircraft
maintenance/testing (no rocket engine). No
further action warranted.

Motor vehicle fires

Uncontrollable.

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104

Table 58: RACM Identified Control Strategies
Source Category New or Proposed
Administrative Rules
Comments
Combustion, Natural Gas Proposed:

R307-315; NOx
Emission Controls for
Natural Gas-Fired
Boilers 2.0-5.0 MMBtu

R307-316; NOx
Emission Controls for
Natural Gas-fired
Boiler greater than 5.0
MMBtu

The UDAQ has identified ultra-low NOx
burners (9 ppmv) as being RACM in most
instances when applied to replacement of
end-of-life equipment or replacement burners.
Some instances, particularly for high MMBtu
units, may exceed previously established
RACM thresholds and require regulatory
flexibility.

UDAQ is proposing the adoption of
administrative rules R307-315 and R307-316
to fulfill this RACM requirement.

Solvents; Hot Mix Asphalt Utah Administrative:
R307-313; VOC and
Blue Smoke Controls
for Hot Mix Asphalt
Plants

The UDAQ has identified blue smoke controls
reducing VOC emissions associated with blue
smoke from Hot Mix Asphalt plants being
RACM. As a result, the Utah Air Quality Board
has adopted Utah Administrative Rule R307-
313 to fulfill this requirement.

5.3 RACM Analysis Conclusion
The evaluation of existing Utah administrative rules, EPA issued CTGs, ACTs, and OTC rules, as
well as similar western counties with moderate ozone NAAs determined that the NWF NAA has adopted
an expansive list of both VOC and NOx emission reduction rules for area sources. Through this process,
and in parallel with UDAQ working groups, two additional control techniques were identified as RACM
that will result in the reduction of NOx emissions from natural gas boiler as well as VOC emission
reduction from hot mix asphalt facilities (Table 58). These controls were determined to be reasonable
and will help the NAA reach attainment as expeditiously as practicable. As a result, the UDAQ has
adopted administrative rule R307-313; VOC and Blue Smoke Controls for Hot Mix Asphalt Plants as a
RACM strategy to reduce VOC emissions. Additionally, the UDAQ has adopted administrative rules R307-
315; NOx Emission Controls for Natural Gas-Fired Boilers 2.0-5.0 MMBtu and R307-316: NOx Emission
Controls for Natural Gas-fired Boiler greater than 5.0 MMBtu. These reduction strategies, and their
implementation timelines, are discussed further in section 7. The UDAQ has determined that the NWF
NAA has met RACM requirements with the RACM analysis and the implementation of the two new
control strategies.
Beyond the RACM controls identified for natural gas-fired boilers and hot mix asphalt facilities,
the UDAQ has identified that the application of in-use limitations for small non-road engines,
particularly those used in lawn and garden operations, are likely to be reasonable in scope and could
result in significant emission reductions of both VOCs and NOx. Section 209 of the CAA prohibits states
from regulating mobile sources in certain ways,93 with section 209(e) specifically preempting states from
regulating emissions from non-road sources. While section 209 does prohibit a state from regulating

93 42 U.S.C. § 7543

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mobile source emissions, the prohibition is not absolute. In particular, section 209(d) allows states to
impose restrictions on when or where these engines can be operated (i.e., “in use“ restrictions),
including for source covered under 209(e). Thus, the UDAQ has identified that states are not preempted
from implementing meaningful emission reduction strategies covering non-road mobile sources through
in-use requirements. The UDAQ plans to develop and implement policies that address emissions from
these sources as the NAA works towards demonstrating attainment as expeditiously as possible.
However, the scope of implementing a policy that covers such a large amount of small and distributed
sources like non-road engines requires more time than allotted for in this SIP revision. The UDAQ
intends to develop and implement a policy aimed at reducing VOC emissions from these sources in
subsequent SIP revisions.

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Chapter 6 – Inspection and Maintenance (I/M) Program
6.1 Overview of I/M Programs
The transportation sector is a major source of both NOx and VOCs in and around the NWF NAA.
Although modern vehicles (1996 and newer) emit far less pollution than older vehicles due to improved
emission reduction technologies, these reductions depend on the on-board emission control systems
being adequately maintained and operating. If not properly maintained, vehicles will not perform as
originally designed, resulting in increased emissions. Malfunctions in emission control technologies can
cause emissions to increase substantially beyond federal vehicle standards, with even minor
malfunctions resulting in increased emissions. Therefore, identifying and repairing malfunctioning
vehicles is imperative to reducing vehicle-related emissions in NAAs.
Vehicle I/M programs require mandatory and periodic testing of on-road motor vehicles for
compliance with emission standards, and the repair of vehicles that do not meet standards. These tests
are designed to determine whether a vehicle’s emission controls are functioning properly, and whether
emissions levels are acceptable. The goal of an I/M program is to identify and repair high-emitting
vehicles to improve air quality in areas not attaining the NAAQS. EPA sets vehicle emission standards to
protect public health, however, these regulations do not guarantee proper operation and maintenance
of a vehicle’s emission controls over its lifetime. State and local governments implement I/M programs
to identify high-emitting vehicles and notify owners and operators to have these vehicles repaired. Once
repaired, vehicles must be retested to verify their emissions are within the standards. The 1990
amendments to the CAA mandated I/M programs for ozone and CO NAAs based on criteria such as air
quality status, population, and/or geographic location.
In parallel with CAA requirements, Utah Code requires that, if identified as necessary to attain or
maintain any NAAQS, a county must create an I/M program as authorized by the Utah Air Quality Board
to formally establish those requirements for county I/M programs after obtaining agreement from the
affected counties.94 Similarly, Utah Code also allows any county with an established I/M program to
subject individual motor vehicles to I/M testing at times other than the annual inspection.95
As a result of the NWF NAA’s previous designation as marginal nonattainment, as well as a CO
NAA that overlaps portions of the NWF NAA, under CAA Section 182(a) and Section 187, Utah was
previously required to implement and maintain an I/M program in the most populated counties in the
NWF NAA including: Davis, Salt Lake, and Weber Counties. Beyond the NWF NAA, Utah was also
required to implement an I/M program in the SWF NAA, which includes Utah County, to the south of the
NWF NAA (figure 1). These programs are required to be at least as effective as the EPA's Basic
Performance Standard.96
6.2 Federal Requirements
I/M programs are mandatory under CAA Section 182 for ozone NAAs. These programs may be
removed if the state can demonstrate that the program is no longer needed. However, the I/M program
would still be retained in the SIP as a contingency control measure, which would be triggered if the area

94 Utah Code Section 41-6a-1642 & Utah Code Ann. § 19-2-104(1)(g).
95 Utah Code Section 41-6a-1642
96 40 CFR § 51.352

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ever exceeds the applicable NAAQS.97 Additionally, states have the flexibility to develop their own I/M
programs based on local conditions, if the state can show that impacted areas will continue to meet air
quality standards.
There are two performance levels of any I/M program—basic or enhanced. Basic I/M programs
are a requirement for moderate ozone NAAs98 which requires testing for light-duty cars for any
urbanized population over 200,000 residents.99 An enhanced I/M program is required for serious,
severe, and extreme ozone NAAs100 with urbanized populations over 200,000. An enhanced I/M
program requires inspection of both light duty cars and light duty trucks.101 As a moderate NAA, the
NWF is only required to demonstrate that its existing I/M programs meet the basic I/M criteria. Since all
counties in the NWF NAA with populations over 200,000 have existing programs, no new I/M programs
are required as part of this SIP revision.
6.3 I/M Testing
There are three types of I/M testing that can be performed on vehicles:

• Visual Inspections: These inspections discourage tampering by checking for the presence of
certain required emission control parts such as catalytic converters.
• Tailpipe Testing: This inspection consists of measuring the exhaust emissions when a vehicle is
idle or under certain engine loads. This inspection is typically for models made in 1995 and
older.
• On-Board Diagnostics (OBD): Vehicles made in 1996 or later have been equipped with OBD
computerized systems. These systems continuously monitor emission control systems and will
activate the “check engine” light if a diagnostic trouble code is detected concerning the vehicle’s
emission controls.
6.4 Utah I/M Program History and General Authority
I/M programs were adopted in the early 1980’s in Utah as a required strategy to attain both the
ozone and CO NAAQS.102 These programs have played a critical role in reducing emissions that
contribute to ozone and CO and have been highly effective in improving air quality in urbanized parts of
the state. Utah's I/M programs are initially authorized in Utah Code Section 41-6-163.61, which was
enacted during the First Special Session of the Utah legislature in 1983. 103 I/M programs were initially
implemented in Davis and Salt Lake counties in 1984, by Utah County in 1986, and by Weber County in
1990. In 1994, Utah Code was amended to authorize the implementation of I/M programs stricter than
minimum federal requirements in counties where it is necessary to attain or maintain a NAAQS. 104

97 40 CFR § 51.905 (A)(4)(i).
98 CAA Section 182(b)(4), 42 U.S.C. § 7511a(b)(4).
99 40 CFR § 51.350(a)(4).
100 CAA Section 182(c)(3), 42 U.S.C. § 7511a(c)(3).
101 40 CFR § 51.350(7) and (8).
102 Davis, Salt Lake, Utah, and Weber counties are required to have I/M programs under Section 182(b)(4) and/or Section 187(a)(4) of the CAA.
103 This section has been renumbered as section 41-6a-1642 by Laws 2005, c. 2, § 216, eff. Feb. 2, 2005.
104 1994 Utah Code.

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This section of the Utah Code required preference be given to a decentralized program to the
extent that a decentralized program would attain and maintain ambient air quality standards and would
meet federal requirements. Thus, I/M programs in Utah are implemented at the county level, and not
directly by the state of Utah. Utah Code also required affected counties and the Utah Air Quality Board
to give preference to the most cost-effective means to achieve and maintain the maximum benefit
regarding air quality standards, and to meet federal air quality requirements related to motor vehicles.
The Utah legislature indicated preference for a reasonable phase-out period for replacement of air
pollution test equipment made obsolete by program in accordance with applicable federal
requirements, and if such a phase-out does not otherwise interfere with attainment of ambient air
quality standards.
By January 1, 2002, OBD inspections and OBD-related repairs were required as a routine
component of Utah I/M programs on model year 1996 and newer light-duty vehicles and light-duty
trucks equipped with certified OBD systems. The federal performance standard requires repair of
malfunctions or system deterioration identified by or affecting OBD systems. In addition, in 2002, the
Utah State Legislature amended the Utah Code to allow for biannual inspection of cars six years old or
newer.105 This provision is applicable to the extent allowed under the current SIP for each county within
the NAA. Meaning the state would need to determine if the I/M programs in counties within the NAA
would need to have their testing frequency modified to comply with NAAQS standards. The state would
then work with local health departments to alter their requirements.
Most recently, in 2005 the Utah State Legislature renumbered and amended Utah Code to allow
counties with an I/M program to require college students and employees who park a motor vehicle on
college or university campus that is not registered in a county subject to I/M provisions to provide proof
of compliance with an emission inspection.106
6.5 UDAQ Evaluation of Current I/M Program
I/M programs in Utah are currently using OBD and tailpipe testing. However, I/M programs rely
mostly on OBD testing because most of the fleet is equipped with OBD systems, but there are still some
tailpipe tests being performed. Details on Utah existing I/M programs, relevant county ordinances and
regulations, network types and enforceability can be found in the applicable I/M TSD.107
In an effort to evaluate if existing I/M programs in the NWF NAA meet the requirements of a
moderate NAA, the UDAQ conducted basic performance standard modeling to show how the existing
I/M programs of Davis, Salt Lake, and Weber counties meet the applicable performance standard for a
basic I/M Program for the summer of 2023. 2023 was chosen as the analysis year to be consistent with
the year used for this modeling demonstration. This evaluation used the same MOVES modeling
assumptions used to develop the on-road mobile source 2023 projection inventory for the NWF NAA
covering Davis, Salt Lake, Weber, and Utah counties.108 Utah County provides reciprocity testing and,
given the proximity of Utah County to the NWF, its I/M program was included in the analysis. Tooele
County was not included in this analysis since the area does not meet the population threshold of
200,000 or more residents in which an I/M program is required.109

105 Utah Code Section 41-6-163.6
106 Utah Code Section 41-6a-1642
107 NWF Inspection and Maintenance (I/M) Program; 2015 Ozone NAAQS Moderate Ozone SIP, TSD
108 2023 EXISTING BASIC INSPECTION AND MAINTENANCE PERFROMANCE STANDARD MODELING TECHNICAL SUPPORT DOCUMENT:
https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001726.pdf
109 40 CFR § 51.350(a)(2) and (a)(3).

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The performance standard compares the modeling results of the existing program and
performance standard benchmark for a basic program for 2023. For a basic I/M program, if the
proposed/existing program achieves the same or lower emissions levels for VOC and NOx as the
performance standard benchmark program, then the proposed/existing program is considered to have
met the basic performance standard. Areas required to operate an I/M program as the result of being
classified (or reclassified) as moderate for an 8-hour ozone NAAQS must use the basic performance
standard, using the program design elements at 40 CFR § 51.352(e). Emission estimates are confined to
the EPA approved MOVES 3.0.3. This model produces emissions daily estimates for on-road vehicles by
providing emissions profiles for starts, exhaust, evaporative and hot soak conditions. Inputs include
speeds, vehicle fuel profiles and specifications, VMT, I/M profiles, VMT mix, vehicle age distributions,
and meteorological conditions. These inputs were chosen to meet EPA and Department of
Transportation guidance on updating local planning assumptions every 5 years.110
Compliance factors were compiled utilizing local 2017 I/M EPA data covering: Total Vehicles
tested, Total Failures, Waivers, and Failure Rate for the following testing procedures: Two Speed Idle,
OBD, and Gas Cap. The compliance data is from EPA prepared compliance data dated 2/21/2019. Since
this modeling exercise had been completed, 2020 I/M testing compliance factors have become available
(EPA prepared compliance data dated 8/12/2021)111. The only difference between the 2017 I/M and
2020 I/M compliance factors is in Weber County for light duty trucks model years 1996-2007 creating a
difference of 1%. Results of this analysis including county specific I/M program details utilized within
MOVES 3.0.3 are included in the Table 59 to Table 62.112

Table 59: 2023 Davis County Summer Basic Performance Modeling
2023 Davis County Summer Basic Performance Modeling (Tons Per Day)

NOx VOC
Davis I/M 7.42 2.77
Basic I/M 7.55 2.91
Difference 0.14 0.13
Table 60: 2023 Salt Lake Summer Basic Performance Modeling
2023 Salt Lake County Summer Basic Performance Modeling (Tons Per
Day)

NOx VOC
Salt Lake I/M 20.98 8.51
Basic I/M 21.42 8.94
Difference 0.44 0.43

110 EPA420-B-08-901 Dec 2008
111 https://www.epa.gov/compliance-and-fuel-economy-data/annual-certification-data-vehicles-engines-and-equipment
112 Utah’s 2023 Existing Basic Inspection and Maintenance Performance Standard Modeling Technical Support Document can be found on the NWF Moderate
Ozone SIP TSD web page at https://deq.utah.gov/air-quality/northern-wasatch-front-moderate-ozone-sip-technical-support-documentation#supporting-tsd.

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Table 61: 2023 Utah County Summer Basic Performance Modeling
2023 Utah County Summer Basic Performance Modeling (Tons Per Day)

NOx VOC
Utah I/M 10.39 3.37
Basic I/M 10.56 3.48
Difference 0.16 0.12

Table 62: 2023 Weber County Summer Basic Performance Modeling
2023 Weber County Summer Basic Performance Modeling (Tons Per Day)

NOx VOC
Weber I/M 5.87 2.12
Basic I/M 5.97 2.22
Difference 0.11 0.10

The analysis provided in this section, with the results highlighted in tables 59 – 62, indicates that
the existing I/M programs currently in place in the NWF meet the CAA requirements for moderate ozone
NAAs.
6.6 Implementation of I/M Program in Tooele County

To determine if the implementation of an I/M program in Tooele County would provide
significant benefit for the NWF NAA to demonstrate attainment of the NAAQS, UDAQ conducted an
analysis of the effects of implementing an I/M program in Tooele County using MOVES parameters
similar to those described in section 6.5. Tooele county has a relatively small population of
approximately 76,000 residents, and only a portion of the total county is included within the boundary
of the NWF NAA (Figure 1). Tooele county has not previously been required to implement an I/M
program since they are below the population threshold of 200,000 residents.
The results of this analysis are shown in Table 63. Based on these results, the UDAQ has
concluded that the emission reductions associated with implementing a Basic I/M program in Tooele
County would yield minimal emission reductions. Thus, the UDAQ has decided not to implement an I/M
program in Tooele County especially in light of the fact that the county does not meet the population
requirements found in 40 CFR § 51.350(a)(3), and the associated emission reductions would be small.
This determination does not exclude the possibility of an I/M program implemented in Tooele County at
a later date.

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Table 63: I/M Program Implementation Evaluation for Tooele County in 2023

NOx VOC VOC
Refuel
NH3 PM2.5 Vehicle Miles
Traveled
No I/M Program 3.783 0.875 0.13 0.097 0.081 3,476,298
OBD I/M Program 3.74 0.833 0.13 0.097 0.081 3,476,298
Percentage Emission
Reduction
-1.14% -4.80% 0.00% 0.00% 0.00% 0.00%
TPD Emission
Reduction
-0.043 -0.042 0 0 0 0

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Chapter 7 – Reasonable Further Progress (RFP)
7.1 Reasonable Further Progress
CAA section 172(c)(2) requires emission reductions of that SIP provisions include Reasonable
Further Progress (RFP)113, which is defined as “annual incremental reductions in emissions of the
relevant air pollutant”114, or ozone precursor emissions including NOx and/or VOCs[referred to as
Reasonable Further Progress (RFP)]. Section 182(b)(1)(A)(i) of the CAA further states that for a moderate
ozone NAA, “the State shall submit a revision to the applicable implementation plan to provide for
volatile organic compound emission reductions, within 6 years” after being designated as a
nonattainment area.115 This section goes on to say that “such a plan shall provide annual reductions in
emissions of volatile organic compounds and oxides of nitrogen as necessary to attain the national
primary ambient air quality standard for ozone.”116 Section 182(b)(1)(A)(i) further details RFP
requirements for a newly designated moderate NAAs, which is a demonstrated 15% reduction
specifically for VOC emissions, known as Rate of Progress (ROP).117 [Since the NWF does not have a
previously approved ROP plan related to ozone, the state must meet the 182(b)(1)(A) requirements for
this moderate SIP.] The EPA has consistently interpreted the 15% VOC-only requirements as a one-time
requirement throughout several implementation rules. Starting with the 1997 8-hour ozone NAAQS
implementation rule,118 which was revised and later replaced by the 2008 NAAQS implementation
rule,119 and finally affirming the same approach in the 2015 NAAQS implementation. This interpretation
has been upheld by the DC Circuit.120
Therefore, the 15% VOC only component achieved over a 6-year period identified in Section
182(b)(1)(A) of the CAA represents a one-time requirement, and once an area has achieved a 15%
reduction of VOCs relative to an established NAAQS baseline year, the area can fulfill subsequent RFP
requirements utilizing NOx and/or VOC reductions, as instructed by the CAA.
Having previously met the one-time 15% VOC only reduction as part of the substantial VOC
emission reductions achieved under previous PM2.5 SIPs, including a 21.2% VOC reduction relative to the

113 42 U.S.C. § 7502(c)(2).
114 Id. § 7501(1).
115 Id. § 7511a(b)(1)(a)(i).
116 Id.
117 Id.
118 Final Rule to Implement the 8-Hour Ozone National Ambient Air Quality Standard—Phase 2; Final Rule To Implement Certain Aspects of the 1990 Amendments
Relating to New Source Review and Prevention of Significant Deterioration as They Apply in Carbon Monoxide, Particulate Matter and Ozone NAAQS; Final Rule for
Reformulated Gasoline, 70 Fed. Reg. 71,612, 71,615 (Nov. 29, 2005) (“Areas that are classified as moderate under the 8 -hour standard that have already
implemented their 15 percent plans under their 1-hour ozone SIPs would be considered to have met the statutory 15 percent requirement. Reasonable further
progress for the first 6 years from the baseline year would be covered under the more generic RFP re quirements of subpart 1. “).
119 Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State Implementation Plan Requirements, 80 Fed. Reg. 12,264, 12,271 (March 6,
2015) (“With respect to RFP requirements, we interpret the 15 percent VOC emission reduction requirement in CAA section 182(b)(1) such that an area that has
already met the 15 percent requirement for VOC under either the 1-hour ozone NAAQS or the 1997 ozone NAAQS (for the first 6 years after the RFP baseline year
for the prior ozone NAAQS) would not have to fulfill that requirement again. Instead, such areas would be treated like areas covered und er CAA section 172(c)(2) if
they are classified as Moderate for the 2008 ozone NAAQS, and would need to meet the RFP requirements under CAA section 182(c)(2)(B) if they are classified as
Serious or above for the 2008 ozone NAAQS.”).
120 Natural Resources Defense Council v Environmental Protection Agency, 571 F.3d 1245 (D.C. Cir. 2009) (holding that EPA reasonably interpreted the CAA
provision requiring a moderate or greater nonattainment area to provide for VOC emission reductions of at least 15 percent). Thi s decision should not be disturbed
by the holding in Loper Bright Enterprises v. Raimondo, No. 22-1219, 2024 WL 3208360, at *5 (U.S. June 28, 2024) overruling Chevron, U.S.A., Inc. v. Natural
Resources Defense Council, Inc., 467 U.S. 837 (1984) because Loper Bright expressly held that by overruling Chevron the Court “does not call into question prior
cases that relied on the Chevron framework.” Further “[t]he holdings of those cases that specific agency actions are lawful—including the Clean Air Act holding of
Chevron itself—are still subject to statutory stare decisis despite the Court's change in interpretive methodology. Mere reliance on Chevron cannot constitute a
“special justification” for overruling such a holding.” Loper Bright, 2024 WL 3208360, at *5 (cleaned up).

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2010 PM2.5 base year achieved in a 6-year period,121 and a 43.2% VOC reduction relative to the 1980 1-
hour ozone standard, the state of Utah is pursuing compliance with RFP / ROP for this SIP revision
through both NOx and VOC emission reductions under CAA Section 172(c)(2) and 182(b)(1(A). Therefore,
the[The] RFP requirement for this SIP revision is to reduce [VOC]ozone precursor emissions by 15%
[within six years]relative to the VOC emissions of the established 2017 baseline year within six years for
the purpose of ensuring attainment of the NAAQS by the attainment date of August 3, 2024. The state
must identify and implement emission reduction strategies equal to or greater than 15% of the 2017
baseline VOC inventory described in Section 3.2 (Table 7) by January 1, 2023. In order for reductions to
count towards RFP, they must occur at sources located within the boundary of the NAA, and “have
actually occurred”122[113], meaning they are quantifiable with strategies developed to reduce emissions
being enforceable.
Details regarding past SIP emission reductions of ozone precursor emissions, including
demonstrations of a 15% VOC reduction relative to a base year for multiple primary NAAQS, and an
overview of how the state is meeting current RFP requirements, are discussed in detail in Section 7.5.
7.2 Methodology
The methodology for determining compliance with CAA Section 182(b)(1)(A) RFP requirements
are as follows:
1) Develop an anthropogenic VOC baseline inventory (2017) for the NAA.
2) Develop an anthropogenic VOC projected inventory (2023) for the NAA that incorporates
anticipated emission reductions.
3) Demonstrate that VOC emissions in the projected year inventory (2023) are at least 15% lower
than the baseline (2017) (i.e., 2023 emissions – 2017 emissions >= 15% of 2017 emissions) and
meet the criteria described in Section 7.1.
Alternatively, if a state is pursuing compliance under Section 172(c)(2) of the CAA, the 15%
emission reduction requirement identified in steps 1-3 serve as the NAA wide emission reduction
requirement, however NOx reductions can be substituted in place of VOC reductions. Beyond
demonstrating the total 15% reduction requirement is fulfilled, a state must also show that the
reductions in NOx deliver an equivalent, or greater, improvement to air quality as would have been
achieved had RFP been met through VOC reductions alone. This demonstration can include
photochemical modeling analysis, as is discussed in sections 7.4.1.123 Lastly, the extent of the current
NAA boundary needs to be considered. NOx substitutions are only an available pathway in areas which
overlap the same geographic extent in which the previously approved VOC reductions occur.
7.3 RFP and Anthropogenic VOC Emission Reductions
Table 64 shows anthropogenic VOC emission for the NWF NAA for the baseline year of 2017 and
the projected year of 2023, as well as the change in emissions from 2017 compared to 2023 (i.e., 2017 –

121 Utah State Implementation Plan Section IX, Part A.21: Control Measures for Area and Point Sources, Fine Particulate Matter, PM2.5 SIP for the Salt Lake City, UT
Nonattainment Area. Adopted December 3, 2014.
122 [113] 42 USC § 7511a(b)(1)(C).
123 NOx Substitutions Guidance. U.S. EPA. December, 1993.
https://www3.epa.gov/ttn/naaqs/aqmguide/collection/cp2_old/19931201_oaqps_nox_substitution_guidance.pdf

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2023 VOC emissions). The total anthropogenic VOC emissions for the NWF NAA in 2017 account for 93.7
tpd. As a result, the RFP requirement for the NWF NAA is 14.0 tpd reduction to achieve the 15%
reduction.

Table 64: Anthropogenic VOC Emission Reductions from 2017 to 2023 for the NWF
Source Sector
2017 Baseline
Anthropogenic VOC
Emissions (tpd)
2023 Projected
Anthropogenic
VOC Emissions
(tpd)
Δ Anthropogenic
VOC Emissions
(tpd)
% Δ
Anthropogenic
VOC Emissions
Airports 1.3 1.4 0.2 15.4
Livestock 0.7 0.7 ---- ----
Area 8.5 8.3 -0.2 -2.4
Non-Road
Mobile 12.5 12.6 0.1 0.8
On-Road
Mobile 20.5 15.3 -5.2 -25.4
Point 5.9 6 0.1 1.7
Point-Electric
Generating
Units
0 0 ---- ----
Rail 0.5 0.4 -0.1 -20
Solvents 43.2 44.5 1.3 3.0
ERC Bank 0.7 0.7 ---- ----
Total 93.7 90 -3.7 -3.9

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Figure 4: NWF Anthropogenic VOC Emission Inventories
As shown in Table 64 and Figure 4, there have been substantial VOC reductions in the on-road
mobile sector, resulting in 5.2 tpd of VOC reductions. These reductions are overwhelmingly due to
improvements in vehicle emission reduction technologies for personal automobiles and the introduction
of cleaner, tier 3 fuels, into the NAA. Other source sectors such as rail and area sources show small
emission reductions of 0.2 and 0.1 tpd, respectively.
While the area has experienced emission reductions across multiple sectors, the area is also
experiencing rapid population growth, with Utah being the fastest growing state in the nation in 2022
and projected to add 2.2 million more residents by 2060.124[114] As a result of this rapid population
growth, the NWF NAA has had emission increases in certain source sectors, including the non-road and
solvents sectors accounting for an added 0.2 tpd and 1.3 tpd, respectively.
The increased emissions in some source sectors that closely track population growth offset the
emission reductions in other sectors. As a result, the net total reductions of anthropogenic VOC
emissions in the NWF NAA are 3.7 tpd, accounting for a decrease of 3.9% of the baseline 2017
emissions.[ This means that the State of Utah still has 11.1% of its RFP requirements to fulfill, or 10.3 tpd
of additional emission reductions required to fulfill the CAA sections 172(c)(2) and 182(b)(1)(A)
requirements.]

[114]124 Kem C. Gardner Policy Institute research and data, available at https://gardner.utah.edu/utah-population-to-increase-by-2-2-million-people-through-2060/
1.3 0.7
8.5
12.5
20.5
5.9
0 0.5
43.2
0.71.4 0.7
8.3
12.6
15.3
6
0 0.4
44.5
0.7
0
5
10
15
20
25
30
35
40
45
50
To
n
s

P
e
r

D
a
y
NWF Anthropogenic VOC Emission Inventories
2017 Baseline Anthropogenic VOC Emissions (tpd)2023 Projected Anthropogenic VOC Emissions (tpd)

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7.4 Anthropogenic NOx Emissions
Table 65 shows anthropogenic NOx emissions for the NWF NAA for the baseline year of 2017
and the projected year of 2023, as well as the change in emissions from 2017 compared to 2023 (i.e.,
2017 – 2023 NOx emissions). [NOx emissions are not part of the ROP requirement for this moderate SIP;
however, t] The area has experienced significant NOx reductions despite the substantial population
growth. [While NOx reductions do not count towards the CAA sections 172(c)(2) and 182(b)(1)(A)
requirements, t]These reductions have played an important role in the area progressing towards
attaining the standard as expeditiously as possible, which is further discussed in section 7.4.1.

Table 65: Anthropogenic NOx Emission Reductions from 2017 to 2023 for the NWF
Source Sector
2017 Baseline
Anthropogenic NOX
Emissions (tpd)
2023 Projected
Anthropogenic NOX
Emissions (tpd)
Δ Anthropogenic
NOX Emissions
(tpd)
% Δ
Anthropogenic
NOx Emissions
Airports 3.1 3.7 +0.6 19.4
Livestock 0 0.0 ---- ----
Area 5.4 4.9 -0.5 -9.3
Non-Road Mobile 10.5 8.0 -2.5 -23.8
On-Road Mobile 55.5 35.4 -20.1 -36.2
Point 20.4 22.0 +1.6 7.8
Point-Electric
Generating Units 0.4 0.4 ---- ----
Rail 9.2 8.8 -0.5 -5.4
Solvents 0.6 0.7 +0.1 16.7
ERC Bank 3.1 3.1 ---- ----
Total 108.3 87.0 -21.3 -19.7

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117

Figure 5: NWF Anthropogenic NOx Emission Inventories
As shown in both Table 65 and Figure 5, the total anthropogenic NOx emissions for the NWF
NAA in 2017 account for 108.3 tpd, decreasing to 87.0 tpd in 2023, accounting for a 21.3 tpd reduction
in daily NOx emissions in this time period from 2017 to 2023. A substantial portion of these emission
reductions, much like those observed in VOC emission reductions (Section 7.3), come from the on-road
mobile sector because of continued improvements to vehicle engine standards and the introduction of
cleaner burning fuels, resulting in 20.1 tpd of emission reductions relative to the baseline year. The NAA
has also experienced NOx reductions in other sectors including non-road mobile, rail and area sources,
accounting for an additional 2.5, 0.5, and 0.5 tpd respectively. While some sectors have had small
amounts of emission growth, such as airports, the majority of emission source sectors are showing
reductions of anthropogenic NOx emissions.
7.4.1 Effectiveness of NOx emission reductions in the NWF NAA
Reductions in NOx have been identified as an effective strategy in reducing ozone formation in
the NWF NAA. A source apportionment modeling analysis conducted by the UDAQ using CAMx
(Comprehensive Air Quality Model with Extensions) OSAT (Ozone Source Apportionment Tool) (section
9.2) at the Hawthorne and Bountiful monitoring stations found that a little more than half of the
modeled ozone at both monitoring sites is attributable to NOx sources (Figure 6). Specifically, on
average, 54% of the ozone is attributable to NOx sources and 46% is attributable to VOC sources at the
Hawthorne station. Similarly, 53% of the ozone is attributable to NOx and 47% is attributable to VOCs at
the Bountiful station. These results indicate that ozone at the controlling monitors in the NWF NAA is
formed under both NOx- and VOC-limited conditions, with a little more than half of the ozone formed
under NOx-limited conditions.
3.1
0
5.4
10.5
55.5
20.4
0.4
9.2
0.6 3.13.7
0
4.9
8
35.4
22
0.4
8.8
0.7 3.1
0
10
20
30
40
50
60
To
n
s

P
e
r

D
a
y
NWF Anthropogenic NOx Emission Inventories
2017 Baseline Anthropogenic NOx Emissions (tpd)2023 Projected Anthropogenic NOx Emissions (tpd)

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118

While the modeling results have some uncertainty, the findings are consistent with those from a
VOC/NOx ratio analysis conducted by the UDAQ which utilized VOC measurements collected at the
Hawthorne monitoring site during the summer of 2021125[115]. 8-hr time-integrated carbonyls
measurements and hourly Gas Chromatograph (GC) data with VOC concentrations weighted by their
Maximum Incremental Reactivity (MIR) (i.e. reactivity respective to ozone production/per unit VOC),
collected from June-August 2021, were used in this ratio analysis. Results showed that the area is in a
transitional regime, with controls on both VOCs and NOx emissions as potentially effective strategies to
reduce ozone formation. These findings are consistent with the CAMX results reported in this section.

Figure 6: NOx-attributable (brown) and VOC-attributable (green) ozone at Hawthorne (left panel) and Bountiful (right)
monitoring stations on average over all days of the modeling episode.
These findings support the UDAQ’s conclusion that the implementation of NOx reduction
controls as identified in section 4 (Table 54) as part of this SIP revision are necessary for the NWF NAA to
demonstrate attainment of the NAAQS as expeditiously as practicable.
The UDAQ also conducted a High-Order Decoupled Direct Method (HDDM) photochemical
analysis examining the predicted reductions in ozone concentrations for a given reduction of
anthropogenic NOx or VOC emissions to further assess the effect of NOx and VOC emission reductions
within the NAA. This analysis is particularly important as ozone chemistry is non-linear, and therefore a
1:1 relationship between NOx and/or VOC reduction and decreased ozone concentrations cannot be
assumed. The resulting isopleth plots (Figure 7) shows that much of the NWF NAA is fairly insensitive to
VOC emission reductions, especially at the controlling monitor.

[115]125 https://harbor.weber.edu/Airqualityscience/docs/conferences/AQSfS-2022/AQSfS2022Posters/sghiatti_sci_4_sol_poster_2022.pdf

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119

Figure 7: Average maximum daily 8-hour ozone isopleths representing NOx and VOC reductions and the resulting predicted
ozone concentrations at Bountiful (left) and Hawthorne (right) monitoring station. Analysis was conducted using CAMx version
7.1 HDDM and demonstrates the sensitivity to NOx reductions vs. VOC reductions at the two monitoring sites.
This analysis further identified that much of the NAA is more sensitive to NOx reductions on
exceedance days, however significant reductions of greater than 50% of NAA anthropogenic emissions
would still be needed to attain 2015 8-hr ozone NAAQS. This analysis highlights that NOx reductions play
a critical role in Utah pursuing a reasonable pathway towards attaining the standard, with a NOx heavy -
limited VOC reduction pathway being the most beneficial pathway for the NWF NAA to improve
summertime air quality. These results confirm the unique characteristics of the NWF NAA airshed and
show that an equivalent reduction in NOx emissions provides as great, or greater, of an improvement in
air quality than VOC emission reduction alone. Therefore, the 21.5 tpd of NOx reductions implemented
as part of the moderate ozone SIP delivers a greater improvement to air quality than would have been
seen with a 15% reduction of VOC emissions alone. As a result, the 25.0 tpd of ozone precursor
emissions (NOx + VOC) reductions documented in this SIP revision represents the best possible pathway
for delivering the maximum improvement in air quality.
7.5 CAA Section 172(c)(2) and NOx Substitutions
As discussed in Section 7.1, the EPA interprets the 15% VOC reduction requirement of CAA
Section 182(b)(1)(A) as a one-time requirement for a nonattainment area. This is supported by the 2015
ozone implementation rule stating that a NAA designated as moderate that has implemented federally
enforceable VOC emission reductions equal to or greater than the current 15% requirement from a
previous ozone NAAQS SIP revision, are granted the opportunity to substitute a comparable amount of
NOx emission reductions under Section 172(c)(2), as long as those reductions deliver an equivalent

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improvement in air quality.126 This section provides the necessary evidence to document past SIP-
approved VOC reductions in excess of 15% relative to a NAAQS base year in a 6 or less year window, as
well as the benefits to air quality associated with NOx reductions within the NWF NAA. Taken together,
this demonstrates the requirements needed to comply with CAA Section 172(c)(2) RFP requirements
utilizing the substitution of NOx emission reductions in place of VOC reductions. This approach is
consistent with the stated intent of RFP requirements, to “provide annual reductions in emissions of
volatile organic compounds and oxides of nitrogen as necessary to attain the national primary ambient
air quality standard for ozone”.127 Furthermore, as clearly demonstrated in Section 7.4.1, this approach
is the most appropriate for the NWF NAA where a combination of both NOx and VOC reductions
provides the most effective pathway towards attainment.
7.5.1 Past and Current SIP Emission Reductions
Table 66 overviews the substantial VOC emissions reductions achieved for both moderate128 and
serious129 PM2.5 SIPs for the Salt Lake City, UT nonattainment area, as well as the 1979 1-hour ozone
standard for the Davis – Salt Lake NAA. This table demonstrates that in the five-year period from the
moderate PM2.5 base year of 2010 to the attainment year of 2015, VOC emissions were reduced from
130 tpd to 102.5 tpd, a reduction of 27.5 tpd. To meet the 15% RFP VOC reduction requirements
specified in 182(b)(1)(A), a decrease of VOC emissions by 19.5 tpd would have been necessary. As a
result, the 27.6 tpd of documented VOC emission reductions far exceeds a 15% threshold of 19.5 tpd,
and therefore serves to fulfill a past RFP plan, with more than a 15% reduction occurring within a 6-year
period. In fact, this reduction represents a 21.2% reduction, far in excess of the 15% required to
demonstrate RFP.

Table 66: VOC reductions in the NWF NAA during past SIPs timelines demonstrating a 15% VOC reduction relative to NAAQS
base years.
Moderate PM2.5 SIP
(2010 - 2015)
Combined Moderate and
Serious PM2.5 SIP (2010 -
2020)
1979 1-hour Ozone SIP
(1980 - 1987)
VOC (tpd
reduced)
27.6 tpd 35.7 tpd 67.7 tpd
15% of base year 19.5 tpd NA (10-year period) 23.5 tpd
182(b) RFP
fulfilled
Yes (21.2% reduction)* NA (10-year period) Yes (43.2% reduction)
* The federally approved reductions from the moderate PM2.5 SIP represent an appropriately equivalent 6-year reduction of
VOC emission to fulfill a 15% reduction relative to a NAAQS base year.

126 83 Fed. Reg. at 63,004 (“Areas classified Moderate for the 2015 ozone NAAQS that had SIPs previously approved to meet the ROP [RFP] requirements for the 1-
hour, 1997 8-hour or 2008 8-hour ozone NAAQS would be treated like areas covered under CAA section 172(c)(2)… the EPA continues to inte rpret CAA section
172(c)(2) as requiring Moderate areas with an approved SIP under the 1-hour ozone NAAQS or prior 8-hour ozone NAAQS to achieve 15 percent ozone precursor
(NOX and/or VOC) emission reductions.”).
127 § 7511a(b)(1)(a)(i).
128 Utah State Implementation Plan Section IX, Part A.21: Control Measures for Area and Point Sources, Fine Particulate Matter, PM2.5 SIP for the S alt Lake City, UT
Nonattainment Area. Adopted December 3, 2014.
129 Utah State Implementation Plan Section IX, Part A.31: Control Measures for Area and Point Sources, Fine Particulate Matter, Serious Area PM2.5 SIP for the Salt
Lake City, UT Nonattainment Area. Adopted January 2, 2019.

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Additionally, as the entirety of the NWF ozone NAA resides within the slightly larger Salt Lake
City PM2.5 NAA boundary, with nearly identical boundaries except for the inclusion of Box Elder County
to the north in the PM2.5 boundary, the past VOC reductions highlighted in Table 67 apply to the entire
NWF ozone NAA. Therefore, a single RFP plan demonstrating compliance through the utilization of NOx
substitutions is suitable for the NWF NAA as all areas of the current boundary can demonstrate past
applicable VOC reductions.
Furthermore, the state of Utah also implemented significant VOC reductions under the 1979 1-
hour ozone NAAQS, which resulted in 67.7 tpd of reductions.130 This reduction represents a 43.2%
reduction in VOC relative to the 1980 base year, far in excess of the 15% required to demonstrate a
successful RFP plan, which additionally serves to fulfill a past 182(b)(1)(A) requirement. However, as air
quality subsequently improved, the area was ultimately granted a clean data determination which
resulted in the suspension of RFP requirements.131 Therefore, VOC emission reductions achieved under
this standard were not federally approved and therefore are not considered a previously approved RFP
plan. While this plan was never acted upon by the EPA, such action was unnecessary since the EPA
issues a clean data determination instead. The act of issuing a clean data determination serves as
verification that the emission reductions were implemented and successful in reducing emissions and
improving air quality, demonstrating the continued effectiveness of this RFP plan.

Table 67: VOC and NOx reduction in the NWF NAA during the moderate SIP timeline relative to RFP requirements for a moderate
SIP as 15% of the 2017 base year.

RFP Requirements 2017 - 2023 moderate
ozone SIP
% of Moderate Ozone
SIP RFP
VOC (tpd reduced) 14.0 tpd 3.7 tpd 26%
NOx (tpd reduced) -- 21.3 tpd 152%
Combined (tpd reduced) -- 25.0 tpd 178%

Lastly, as overviewed in Section 7.3 and Section 7.,4 and shown in Table 67, the state of Utah
has been able to account for 3.7 tpd of VOC emission reductions from 2017 to 2023 as part of this
moderate ozone SIP revision, as well as a 21.3 tpd reduction of NOx emissions over the same six-year
period. Combined, ozone precursor emissions were reduced 25.0 tpd during the 6-year period of this SIP
revision, representing 178% of the 14.0 tpd RFP requirement, and therefore fulfilling RFP requirements
for this SIP revision.
7.5.2 PM2.5 Chemistry and VOC Reductions
While northern Utah’s PM2.5 air quality challenges are predominantly a wintertime issue, the
emission reductions implemented under these past SIPs to address PM2.5 pollution episodes were largely
adopted as year-round emission reduction strategies. As a result, the associated NOx and VOC emission
reductions decrease both wintertime PM2.5 and serve to improve summertime ozone throughout the
NWF NAA. The interconnectedness of ozone and wintertime PM2.5 in the Wasatch Front is complex, but
breaks down into three essential components:

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1. While the reaction of NO2 with sunlight (hv) initiates the formation of ozone (O3), VOC emissions
accelerate the daytime formation of ozone (O3) in both the wintertime and summertime which
subsequently drives the availability of hydroxyl radicals (OH) within the troposphere. A
simplified cycle of this chemistry is included in the equations below (equations 2 - 4):

Equation 2
NO2 + sunlight(hv) → NO + O3
O + O2 + M → O3 + M (M=air)
O3 + hv → O2 + O
O + H2O → 2OH
VOC + OH → RO2
RO2 + NO → RO + NO2

2. The newly formed NO2 at the end of the reactions above subsequently cycles back to form
additional ozone. The presence of ozone as formed in the reactions above during the day
determines the availability of OH radicals. OH radicals subsequently act as fuel for daytime PM2.5
chemistry wherein the NOx-HOx cycle is responsible for daytime production of ozone and nitric
acid (HNO3).132 This cycle begins when VOCs are oxidized by OH, generating HO2 or RO2 radicals
(equation 3).

Equation 3
OH + VOC → HO2 + RO2
HO2 + NO → NO2 + OH
OH + NO2 → HNO3

HNO3 undergoes an acid-based reaction with gas phase ammonia (NH4) to form particulate
ammonium nitrate (NH4NO3), the predominant secondary particulate compound found in
wintertime Persistent Cold Air Pool (PCAP) events in northern Utah.133

3. Lastly, the presence of ozone plays a direct instigating (oxidative) force in the nighttime PM2.5
chemistry as at night NOx converts to particulate ClNO2 and HNO3 through NO3 and N2O5
(equation 4).134

Equation 4
NO2 + O3 → NO3
NO3 + NO2 ⇆ N2O5
N2O5 + H2O (het.) → 2HNO3

132 Womack, C. C., McDuffie, E. E.,Edwards, P. M., Bares, R., de Gouw, J. A.,Docherty, K. S., et al. (2019). An oddoxygen framework for wintertime ammonium
nitrate aerosol pollution in urban areas: NOx and VOC control as mitigation strategies. Geophysical Research Letters,46, 4971 –4979.
https://doi.org/10.1029/2019GL082028.
133 Kelly, K. E.; Kotchenruther, R.; Kuprov, R.; Silcox, G. D. Receptor model source attributions for Utah’s Salt Lake City airshed and the impacts of winte rtime
secondary ammonium nitrate and ammonium chloride aerosol. J. Air Waste Manage. Assoc. 2013, 63 (5), 575−590.
134 Munkhbayar Baasandorj, Sebastian W. Hoch, Ryan Bares, John C. Lin, Steven S. Brown, Dylan B. Millet, Randal Martin, Kerry Kelly, Kyle J. Za rzana, C. David
Whiteman, William P. Dube, Gail Tonnesen, Isabel Cristina Jaramillo, and John Sohl. Environmental Science & Technol ogy 2017 51 (11), 5941-5950. DOI:
10.1021/acs.est.6b06603.

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N2O5 + HCl (het.) → HNO3 + ClNO2

As with daytime chemistry, the resulting HNO3 reacts with NH3 to form particulate nitrate
NH4NO3, with NO3, N2O5, and ClNO2 converted back to NO2 and O3 the following morning and further
contributing to daytime chemistry.

The importance of ozone in wintertime PM2.5 is reinforced by the fact that tropospheric ozone is
completely depleted during PCAP events (0.00 ppb) throughout the Wasatch Front, as ozone acts as a
fuel driving secondary particulate formation. Because of the important role ozone plays in both the
daytime and nighttime formation of PM2.5, Utah’s PM2.5 SIPs specifically targeted reductions of ozone
and its precursor emissions to limit the effectiveness of these pathways. Utah’s most recent PM2.5 SIP
explains this interconnectedness of ozone and PM2.5 formation.135 The explicit efforts to target the
formation of ozone, even during the wintertime, as well as the year-round nature of the emission
reduction policies implemented as part of these efforts, demonstrates why VOC emission reductions
achieved under a PM2.5 NAAQS SIP should be applied toward RFP compliance through NOx substitutions
under CAA Section 172(c)(2) for this ozone SIP revision.
7.5.3 NOx Effectiveness
As discussed in detail in section 7.4.1 and highlighted in Figure 7, the airshed of the NWF NAA is
more sensitive to reduction in NOx than in VOCs, especially at the controlling monitor. As an example, a
50% reduction of VOCs at the Bountiful monitoring site (~46 tpd reduction) results in a 1-2 ppb decrease
in modeled 8-hour ozone concentrations. Conversely, the same 50% reduction in NOx (also ~46 tpd
reduction) results in a 4-5 ppb decrease, approaching attainment of the standard at that location.
However, as demonstrated by the fact that the Hawthorne monitor is far less sensitive to NOx
reductions than the Bountiful monitor, the ozone photochemistry in the NWF NAA is highly localized
with each monitoring location responding differently to NOx and VOC reductions. Regardless of location,
however, all sites respond to paired VOC and NOx reduction strategies well, further demonstrating that a
NOx-heavy - limited VOC reduction pathway provides the most reasonable pathway to attainment.
Furthermore, these results demonstrate that NOx emission reductions deliver an equivalent, or better,
improvement to air quality at the controlling monitor, especially when paired with the VOC reductions
documented in this SIP revision. Therefore, the 21.3 tpd NOx emission reductions highlighted in Section
7.4 serve to not only fulfill the 14.0 tpd RFP requirement but also to deliver a greater overall benefit to
air quality than a 15% reduction in VOC emissions alone. Lastly, the NOx and VOC emission reductions
combined in this SIP revision result in a total of 25.0 tpd, representing a 26.7% reduction in ozone
precursor emissions, or 178% of the RFP requirement, while delivering the most effective and
reasonable pathway towards attaining the standard.
7.5.4 Conclusion
The significant VOC emission reductions implemented under past PM2.5 SIPs and ozone SIPs in
the NWF allow the area to pursue compliance with RFP requirements136 for this SIP revision through the
reduction of both NOx and VOC emissions, as is consistent with the EPAs interpretation of Section

135 https://documents.deq.utah.gov/air-quality/planning/technical-analysis/research/northern-utah-airpollution/utah-winter-fine-particulate-study/DAQ-2018-
004037.pdf (“Aerosol chloride can also contribute to the formation of nitryl chloride (ClNO2), a source of radicals which act to enhance the daytime photochemical
production of ozone and nitrate, both of which are important contributors to PM2.5 formation. This formation of ClNO2 is particularly active in the Salt Lake Valley, as
shown by recent aircraft measurements (2017 Utah Winter Fine Particulate Study (UWFPS)).”)
136 42 U.S.C. § 7511a(b)(1)(A)(i).

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172(c)(2) of the CAA. As demonstrated in Table 66, under the moderate PM2.5 SIP, the state
implemented a 21.23% reduction of VOC emissions relative to the 2010 base year in less than a 6-year
period, significantly exceeding the 15% requirement for an RFP plan. Furthermore, the state
demonstrated a 43.2% reduction in VOCs for the 1979 1-hour ozone standard. As a result, the state has
twice, prior to this SIP revision, implemented a full 15% VOC-only reduction in a 6-year period within the
NAA, fulfilling the one-time 182(b)(2)(A) VOC-only obligation. As a result, the RFP requirement for this
SIP revision, calculated as 15% of the 2017 VOC emission inventory, is a reduction of 14.0 tpd of NOx
and/or VOC emissions. From 2017 to 2023, the NWF NAA has seen a combined 25.0 tpd reduction of
ozone precursor emissions, representing a a 26.7% reduction in of ozone forming precursor emissions.
The combined NOx and VOC emission reductions have also been demonstrated to provide a greater
improvement to air quality than a 15% reduction in VOC emissions alone. Therefore, the NWF NAA has
met RFP requirements as a moderate NAA for the 2015 ozone NAAQS.
[7.5]7.6 Future SIP Emission Reductions
The UDAQ has identified several emission reduction strategies that, once fully implemented, will
result in the reduction of both VOC and NOx emissions within the NWF NAA and count towards RFP
requirements. However, due to the short implementation timeframe afforded to states under this SIP
revision, paired with the added difficulty of finding viable VOC reduction strategies after the extensive
emission reductions associated with Utah’s PM2.5 planning efforts, these strategies will not be fully
implemented by the implementation deadline of January 1, 2023[116]137 and thus, will not count towards
RFP under the moderate SIP. Utah is working to have these strategies fully implemented prior to the
summer of 2026 in an effort to count these reductions towards RFP requirements during the state’s
submission of a potential serious SIP for the same NAA. The UDAQ is simultaneously implementing NOx
emission reductions both in anticipation of future SIP creditability as well as in an effort to demonstrate
attainment of the standard at the earliest achievable date.
[7.5.1]7.6.1 Hot Mix Asphalt; Utah Administrative Code Rule R307-313
The UDAQ has identified reducing VOC emissions associated with hot mix asphalt manufacturing
as a technologically viable and economically feasible control strategy. UDAQ has proposed R307-313
requiring hot mix asphalt (HMA) plants in the NAA to install emission capture and control devices to
reduce VOC and blue Smoke emissions associated with the production and loading of HMA and oil
storage tanks. Blue smoke is a visible emission generated during the production of HMA plants that
results from the process of mixing hot oil with aggregate which consists of oils heated to the point of
volatilization resulting in aerosols containing VOCs. Blue Smoke controls work to control both the visible
emissions and VOC emissions from HMA plants by capturing the emissions at various points of the
production process and routing these emissions through ducting to a destruction point, either using
filters and activated carbon, or through post-capture combustion. Emissions from the associated oil
tanks can be captured and reduced using similar technologies.
The UDAQ identified 15 HMA plants operating in the NWF NAA as well as 48 oil tanks associated
with asphalt manufacturing at these plants. UDAQ estimates that the aggregated PTE emissions from
these activities result in a combined 0.34 tpd (125.32 tpy) of VOC emissions in the NAA, of which 0.26
tpd (95.63 tpy) would be reduced with the implementation of controls as required by R307-313. It is
important to note that these numbers are represented as PTE, and when applied to actual emissions

[116]137 87 Fed. Reg. 60,897.

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from the sources based on annual production the emission reductions will be lower. This difference
explains why associated inventoried emissions described in section 3 do not match those reported here,
and thus it is expected that the actual emission reductions will be lower as many facilities are permitted
to produce more asphalt per year than what is actually produced annually.
Administrative rule R307-313 was adopted by the Utah Air Quality Board on February 1, 2023.
However, the lead time for the engineering and installation of these controls, as well as the additional
testing and emission destruction verification required for the implementation of a novel emission
reduction strategy, mean that the emission reductions associated with this rule will not be creditable
under the moderate SIP timeline. As impacted facilities have until May 1, 2025 to install controls, these
emissions reductions are expected to be creditable for future SIP reductions.
[7.5.2]7.6.2 Boilers; Utah Administrative Code Rules R307-315 and R307-316
In an effort to reduce NOx emissions in and around the NWF NAA, UDAQ has proposed the
adoption of R307-315; NOx Emissions Controls for Natural Gas-Fired Boilers 2.0-5.0 MMBtu and R307-
316; NOx Emission Controls for Natural Gas-Fired Boilers greater than 5.0 MMBtu. These rules both
implement an emission standard of 9ppmv for natural gas-fired boilers in the NAA in the effected
MMBtu ranges. In aggregate, these rules will apply to an estimated 2,136 boilers in the NAA which
combine to emit an estimated 8.55 tpd (3,122 tpy) of NOx emissions. It is important to note that these
emission estimates are independent bottom-up estimates of the total potential emissions from boilers,
and were determined using different datasets and methods than those used in the development of the
inventories described in section 3. The UDAQ believes that these numbers are a more accurate
representation of actual emissions from boilers within the NAA. However, these numbers may be
different than those reported in section 3, and any future SIP credited emission reductions associated
with the implementation of these rules would rely instead on the numbers reported in the inventory.
The implementation of R307-315 and R307-316 has the potential to reduce 6.9 tpd (2,522 tpy) of these
combined emissions. However, R307-315 and R307-316 do not require the retrofit or replacement of
any boiler currently operating in the NAA, and instead require new boilers or burner replacements to
meet the 9ppmv standard. Thus, the implementation of this rule will take place over a long period of
time as the average lifespan of this equipment can be greater than 20 years.
Since the emission reductions from the implementation of R307-315 and R307-316 will occur
beyond the moderate SIP timeline[are targeted at the reduction of NOx emissions], the reductions
associated with these rules will not count towards RFP requirements for this SIP revision but are
anticipated to be creditable for future SIP reductions.
[7.5.3]7.6.3 US Magnesium LLC
The UDAQ also examined major industrial point sources that contribute to the degradation of
the NWF NAA’s airshed but are located outside of the existing boundary. This examination identified
one source that met this criteria, US Magnesium LLC, located in Tooele County on the southwestern
edge of the Great Salt Lake. This facility produces significant amounts of highly reactive precursor
emissions that contribute to both ozone and PM2.5 formation along the Wasatch Front.
US Magnesium LLC is the largest producer of primary magnesium in the US and operates the
Rowley Plant production facility on the western edge of the Great Salt Lake in Tooele County near the
NAA boundary. Here, water from the Great Salt Lake is evaporated to produce a brine solution that is
then purified and dried before going through a melt reactor and electrolytic process which separates
magnesium metal from chlorine. Byproducts of this industrial process include VOCs and NOx, as well as
chlorine which is converted into hydrochloric acid. All of these byproducts contribute to ozone and

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secondary particulate matter formation in the NWF NAA. In 2021, US Magnesium’s permitted potential
to emit was 894 tpy of VOCs, 1,261 tpy of NOx and 8,522 tpy of Hazardous Air Pollutants (HAPs). These
emissions make US Magnesium’s Rowley plant one of the largest point sources of VOCs and NOx in the
greater Wasatch Front and the largest point source of HAPs in Utah.
As a result of the magnitude of emissions and proximity to the NWF NAA boundary, UDAQ
required US Magnesium to perform a RACT analysis for VOC and NOx emissions. As described in detail in
section 4.15, the RACT analysis submitted by US Magnesium identified that the installation of a steam
stripper and regenerative thermal oxidizer on the wastewater ponds at the boron plant would be
feasible. Once installed, this control will result in the reduction of 0.44 tpd (161.7 tpy) of VOC. However,
since the source is located outside of the current NAA (see section 1.4.2), and the timeline for the
installation of these controls are beyond what is statutorily required, these emission reductions are not
creditable towards RFP requirements but will be included as a contingency measure as discussed in
section 11.2.2.
[7.5. 4]7.6.4 Tesoro Refining & Marketing Company LLC Marathon Refinery
As described in section 4.12, a RACT analysis submitted by Tesoro Refining & Marketing
Company LLC Marathon Refinery identified that the installation of selective catalytic reduction for
reducing NOx emissions from the cogeneration turbines with heat recovery steam generation CG1 and
CG2 would be technologically feasible. As a result, these controls will be required to be installed by
October 1, 2028, in order for the NAA to demonstrate attainment of the standard as expeditiously as
practicable. The installation of these controls will result in an emission reduction of approximately 0.18
tpd (68.78 tpy) of NOx once installed. Since the timeline for the installation of these controls is beyond
the implementation timeline for this SIP revision, and the controls will result in the reduction of NOx
emissions and not VOC emissions, these emission reductions are not creditable towards RFP
requirements but are anticipated to be accounted for in subsequent SIP revisions.
In addition to the NOx reductions associated with controls on CG1 and CG2, Tesoro Refining &
Marketing Company LLC Marathon Refinery will be required to install a secondary seal on Tank 321 and
replace the wastewater system API Separator and DAF unit with a closed vent to a carbon adsorption
control system. These controls, once installed, will result in reductions of VOC emissions by 0.006 tpd
(2.30 tpy) and 0.027 tpd (10.0 tpy) respectively. Thus, the combined VOC reductions associated with
these controls is expected to be .033 tpd (12.3 tpy).
[7.5.5]7.6.5 Lawn and Garden Small Non-Road Engines
As noted in section 5.3, the UDAQ has identified emission reduction policies aimed at reducing
VOCs and NOx emissions from small non-road engines used in lawn and garden operations as being
reasonable. While there are some substantial limitations on the state in how emissions from these
sources can be regulated due to CAA Section 209 preemption, the implementation of in-use restrictions
for this class of equipment on ozone exceedance days, colloquially known as “mandatory action days,”
complies with Section 209 preemption while simultaneously allowing for significant VOC emission
reductions on days in which reductions are the most critical. The state has identified that the
implementation of a rule based on these criteria could net a VOC emission reduction of approximately
2.84 tpd throughout the NWF NAA[, which would account for a significant portion of the state’s
remaining RFP requirement]. It is the intent of the UDAQ to introduce an administrative rule during
subsequent ozone state implementation planning efforts that aligns with reducing emissions from these
sources through mandatory action days restrictions.

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7.7 RFP Conclusions
As described in section 7.5.4, this SIP revision demonstrates compliance with RFP requirements
for a moderate NAA under CAA section 172(c)(2) through the utilization of NOx substitutions as allowed
for NAAs with previously approved SIPs demonstrating comparable past VOCs emissions reductions.

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Chapter 8 - Attainment Demonstration and Weight of Evidence
8.1 Background
CAA Section 182(b)(1)(I) requires SIP revisions for moderate ozone NAAs to contain an
attainment demonstration, with the ozone implementation rule[117]138 further specifying that an
approvable demonstration rely on a photochemical model, or another equivalent analytical method
determined to be at least as effective as that required for a serious NAA. For this SIP revision, the UDAQ
has developed a photochemical model following EPA guidance, with supplemental analyses to perform
the attainment demonstration modeling. In the previous sections of this SIP revision, ozone
concentrations have been reported using the unit ppm to be consistent with CAA and CFR (Code of
Federal Regulations) language. In this all subsequent sections (sections 8 – 12), the UDAQ will be
reporting ozone concentrations in the unit of parts per billion (ppb), in order to be consistent with
literature and EPA technical guidance.
The photochemical model developed for this SIP serves as a useful tool for projecting future
ozone concentrations, determining source regions that contribute to local ozone levels, and estimating
the impacts of emission source categories. This model also represents a significant step forward in
understanding the transport and formation of ozone throughout the NWF and the broader state of
Utah. Though the predictive ability of this model is scientifically sound and meets established
performance criteria, all models have inherent limitations since they are a simplified approximation of
complex real-world systems. Therefore, results presented from this modeling analysis should not be
considered the sole source of information relied upon when determining if a region will attain the 2015
ozone standard by the attainment date.
EPA’s modeling guidance139[118] overviews supplemental analyses, termed “weight of evidence”
(WOE), that can be used to further support an attainment determination if the maximum MDA8 ozone
DV is close to the 70-ppb (0.070 ppm) standard at one or more monitoring sites. A WOE analysis is “a
totality of the circumstances approach, one that considers all available data to evaluate the
reasonableness of the modeled result which supplements those results.”140 [119] EPA’s modeling guidance
outlines the basic types of analysis that could be included a part of a WOE analysis including:
• Additional modeling analyses,
• Analysis of trends in ambient air quality and/or emissions, and
• Additional unaccounted emission controls or reactions
The results of the UDAQ’s photochemical modeling and WOE are presented in section 8.2.

[117]138 83 FR 62998
[118]139 Modeling Guidance for Demonstrating Air Quality Goals for Ozone, PM2.5, and Regional Haze: https://www.epa.gov/sites/default/files/2020-
10/documents/o3-pm-rh-modeling_guidance-2018.pdf
[119]140 Environmental Defense Fund v. Unites States EPA, 369 F.3d 193, 198 (2d Cir. 204).

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8.2 Photochemical Modeling Platform
The UDAQ conducted an air quality modeling analysis in support of the NWF NAA attainment
demonstration. Modeling was performed following EPA’s modeling guidance141[120]. This modeling
platform includes emissions modeling, meteorological modeling, and photochemical modeling.
Photochemical modeling was conducted using the CAMxv7.1 model. Emissions inventories were
collected and processed through the Sparse Matrix Operating Kernel Emissions Model (SMOKE) version
4.8.1. With the exception of lightning NOx and oceanic emissions, modeling was based on scripts and
data from EPA’s 2016v2 modeling platform.142[121] Sea salt and lightning NOx emissions were calculated
in CAMx by running the corresponding CAMx tools (oceanic_v4.2 and lnox_v1.1, respectively).
Meteorological fields for input into CAMx were produced using the Weather Research and Forecasting
(WRFv4.2) model. A detailed description of each of these models, their configuration, settings, and
performance are provided in their respective TSDs.143 [122]
For this attainment demonstration, the period of June 15 - August 1, 2017, was selected as the
modeling episode, where June 15 - 25 corresponds to spin-up days. 2017 was also selected as the base
year for modeling and 2023 was selected as the future year with local emissions projected from the
2017 inventory as described in section 3. The modeling domain consisted of three nested grid domains
at 12/4/1.33 km. The 12 km domain covers the Western United States and is aligned with EPA’s 12US1
domain, with the north-south extent of this domain matching the EPA’s domain. The 4 km domain is
nested within the 12 km domain and covers the state of Utah as well as parts of neighboring states. The
1.33 km domain is nested within the 12/4 km domains and extends over the northern Wasatch Front
non-attainment area to provide higher resolution modeling within this area. The 12/4/1.33 km nested
grid modeling domain configuration is shown in Figure [7]8.

[120]141 Modeling Guidance for Demonstrating Air Quality Goals for Ozone, PM 2.5, and Regional Haze: https://www.epa.gov/sites/default/files/2020-
10/documents/o3-pm-rh-modeling_guidance-2018.pdf
[121]142 EPA 2016v2 Emissions Modeling Platform TSD https://www.epa.gov/system/files/documents/2021-
09/2016v2_emismod_tsd_september2021.pdf
[122]143 SMOKE Technical Support Documentation for NWF SIP Attainment Demonstration: https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-
001603.pdf & Meteorological Modeling for Wasatch Front O3 SIP Technical Support Documentation and Model Performance Evaluation:
https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001605.pdf

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Figure [7]8: 12/4/1.33 km CAMx Modeling Domains
Time- and space-variable initial and boundary conditions (ICs and BCs, respectively) for the
outermost domain (i.e., 12 km domain) were derived from GEOS-Chem global chemistry model outputs
for 2017, with the modeling performed by Ramboll under contract with WESTAR.144 [123] Following EPA
guidance, the same GEOS-Chem-derived ICs and BCs for the 2017 base case were used for the 2023
future case. BCs and ICs for the 4 km domain, which was run in a two-way nested configuration with the
1.33 km domain, were extracted from the 3-D CAMx output concentration files for the 12 km domain.
Concentrations were extracted along the lateral boundaries of the 4 km domain.
CB6r5h (version 6, revision 5 with halogens) gas-phase chemical mechanism, which includes
halogens chemistry, was used for all simulations. At the request of the UDAQ, this mechanism was
specifically developed and implemented by Ramboll, developer of CAMx, in a special version of CAMx
v7.1 as a replacement for CB6r5 (version 6, revision 5). CB6r5h was developed to account for
interactions between inorganic halogen species, ozone, VOCs, and NOx, where reactions involving
chlorine (Cl) and bromine (Br) were added to CB6r5. Halogens emissions are significant in the valley and
play a significant role in PM and ozone formation in the NWF. An aircraft monitoring campaign
conducted by the National Oceanic and Atmospheric Administration (NOAA) in winter 2017 indicated
that US Magnesium, an industrial plant located on the southwest edge of the Great Salt Lake, emits
large quantities of HCl and dihalogens (Cl2, Br2, BrCl), with the facility being the single largest halogen
emission source in the US.145 [124] Using a photochemical box model and a 3D chemical transport model,
the investigators also showed that, while these halogens induce ozone depletion near the plant, they

[123]144 [1] https://views.cira.colostate.edu/docs/IWDW/Modeling/WRAP/2017/Ramboll_WESTAR_GEOS -Chem_Report_8Apr_2021.pdf
[124]145 C. C. Womack, W. S. Chace, S. Wang, M. Baasandorj, D. L. Fibiger, A. Franchin, L. Goldberger, C. Harkins, . S. Jo, B. H. Lee, J. C. Lin, B. C. McDonald, E. E.
McDuffie, A. M. Middlebrook, A. Moravek, J. G. Murphy, J. A. Neuman, J. A. Thornton, P. R. Veres, S. Brown. Midlatitude Ozone Depletion and Air Quality Impacts
from Industrial Halogen Emissions in the Great Salt Lake Basin. Environ. Sci. Technol. 2023, 57, 5, 1870–1881.

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lead to significant increases in the formation of particulate ammonium nitrate, PM2.5, ozone, and other
oxidants in populated regions of the Salt Lake Valley located downwind of the plant. Regional PM2.5
increases of 10%-25% were attributed to this single industrial halogen source. Given that the chemical
cycles leading to ozone and ammonium nitrate are linked146[125] implementing CB6r5h in our
summertime ozone modeling is increasingly important.
8.2.1 Model Performance Evaluation (MPE)
Model performance was evaluated by comparing the 2017 modeled ozone concentrations to
measured concentrations of ozone and ozone precursors, including NOx, NO2 and VOCs. The evaluation
was focused on results for the 1.33 km modeling domain and results for spin-up days are excluded from
this analysis. Results showed that the CAMx model performs well at simulating ozone at all sites within
the NWF NAA. While the model generally underestimates MDA8 ozone concentrations at the local
monitors, site-specific performance statistics are within established performance criteria. For all days of
the modeling episode, modeled MDA8 ozone concentrations are within established performance criteria
for Normalized Mean Bias (NMB), Normalized Mean Error (NME) and correlation coefficient (R). NMB
values for all sites are within the performance criteria of ±15% (Table [66]]68). Similarly, NME and R
values for all sites are within their respective performance criteria of < 25% and > 0.5 (Table [67]69).
These performance statistics suggest that the model performs well at simulating MDA8 ozone
concentrations. On days with elevated ozone (observed MDA8 > 60 ppb), model performance was
overall acceptable with NME values falling within their performance thresholds at all sites (< 25%) and
NMB performance threshold being slightly exceeded at one of the sampling sites (NMB of -15.86%)
(Table [67]69). At some sites, the correlation coefficient R displayed some values below 0.5, which is
likely related to the model switching from an underprediction to an overestimation of MDA8 ozone on a
few days (< 8% of high ozone modeling days), which impacted the modeled ozone temporal trend.
These days were characterized by a variable cloud cover, which WRF did not simulate completely. More
details on this are provided in the CAMx MPE TSD.

Table [66]68: Performance statistics for MDA8 ozone on all days of the modeling episode. Results are shown for monitors in the
1.33 km modeling domain.
AQS Site ID Site Name NMB (%) NME (%) R
49-011-0004 Bountiful -11.36 13.32 0.735
49-035-3006 Hawthorne -9.75 12.48 0.653
49-035-3013 Herriman -13.73 14.46 0.61
49-045-0004 Erda -14.66 16.04 0.663
49-057-0002 Ogden -10.51 12.8 0.652
49-057-1003 Harrisville -14.12 14.56 0.763

[125]146 C.C. Womack, E.E. McDuffie, P.M. Edwards, R. Bares, J.A. de Gouw, K.S. Docherty, W.P. Dubé, D.L. Fibiger, A. Franchin, J.B. Gilman, L. Goldberger, B.H. Lee,
J.C. Lin, R. Long, A.M. Middlebrook, D.B. Millet, A. Moravek, J.G. Murphy, P.K. Quinn, T.P. Riedel, J.M. Roberts, J.A. Thornton, L.C. Valin, P.R. Veres, A.R. Whitehill,
R.J. Wild, C. Warneke, B. Yuan, M. Baasandorj, S.S. Brown, An Odd Oxygen Framework for Wintertime Ammonium Nitrate Aerosol Pollution in Urban Areas: NO x
and VOC Control as Mitigation Strategies. Geophys. Res. Lett., 46, 4971-4979 (2019).

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Table [67]69]: Performance statistics for MDA8 ozone on high O3 days (observed MDA8 > 60 ppb). Results are shown for
monitors in the 1.33 km modeling domain.
AQS Site ID Site Name NMB (%) NME (%) R
49-011-0004 Bountiful -11.49 13.22 0.56
49-035-3006 Hawthorne -9.12 12.22 0.276
49-035-3013 Herriman -13.86 13.9 0.294
49-045-0004 Erda -15.86 16.78 0.565
49-057-0002 Ogden -10.16 12.46 0.318
49-057-1003 Harrisville -14.02 14.57 0.586

Moreover, the model generally captures well the temporal variability of MDA8 ozone
concentrations, with the timing of peak and low ozone values being well represented (Figure[8]9 to
Figure[13]14). The underestimation in modeled MDA8 ozone concentrations is likely primarily related to
an underestimation in local emissions, rather than background emissions. Background ozone is well-
replicated as indicated by the overall good agreement between modeled and observed MDA8 ozone
concentrations at Gothic Colorado, a high-altitude (10,000 ft) monitoring site in the Colorado Rockies
that serves as a good indicator of mid-tropospheric air (Figure [14]15).
Overall, the model exhibited a level of agreement with measurements that has typically been
achieved for US regulatory modeling for this region.147 [126] These results provide confidence in the ability
of the modeling platform to provide a reasonable projection of future year ozone concentrations and
source contributions in the NWF NAA.

Figure [8]9: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone concentration
(O3_8hrmax) at the Bountiful monitoring station.

[126]147 https://www.epa.gov/system/files/documents/2022-03/aq-modeling-tsd_proposed-fip.pdf & Denver Metro/North Front Range 2017 8-Hour Ozone State
Implementation Plan: 2011 Base Case Modeling and Model Performance Evaluation.
https://views.cira.colostate.edu/wiki/Attachments/Source%20Apportionment/Denver/Denver_2017SIP_MPE_Finalv1.pdf

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Figure [9]10: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone concentration
(O3_8hrmax) at the Hawthorne monitoring station.

Figure [10]11: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone concentration
(O3_8hrmax) at the Erda monitoring station.

Figure [11]12: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone concentration
(O3_8hrmax) at the Herriman monitoring station.

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Figure [12]13: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone concentration
(O3_8hrmax) at the Harrisville monitoring station.

Figure [13]14: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone concentration
(O3_8hrmax) at the Ogden monitoring station.

Figure [14]15: Time series of observed (grey line) and modeled (red line) maximum daily 8-hr average ozone concentration
(O3_8hrmax) at Gothic Colorado monitoring station.
8.2.2 Determination of Future Year (2023) Design Values
The ozone predictions from the CAMx model simulations were used to project ambient ozone
DVs for the year 2023 following EPA’s ozone modeling guidance for SIP demonstrations148[127]. Five-year
weighted average DVs centered on the base modeling year of 2017 were first calculated by averaging
ambient 8-hour ozone DVs for 2015-2017, 2016-2018, and 2017- 2019. The 5-year weighted average

[127]148 https://www.epa.gov/sites/default/files/2020-10/documents/o3-pm-rh-modeling_guidance-2018.pdf

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DVs at each site were then projected to 2023 using the Software for Model Attainment Test Software –
Community Edition (SMAT-CE version 1.6).149[128] This program predicts future year ozone DVs (FDVi) for
each monitoring site within the NWF NAA by calculating site-specific relative response factors (RRFi) and
scaling the 5-year weighted average base year ozone DV (BDVi) at each site (i) using its corresponding
RRFi.

Equation [2]5
𝑫𝑫𝑽𝒊=𝑹𝑹𝑫𝒊 × 𝑨𝑫𝑽𝒊

The RRFi for each monitoring site corresponds to the fractional change in MDA8 ozone between
the base and future year. It is based on the average ozone on model-predicted “high” ozone days in a
3x3 grid cell array centered on the grid cell containing the monitor. Following EPA modeling guidance,
RRFs were calculated based on the highest 10 modeled ozone days in the base year simulation at each
monitoring site. Specifically, the RRF for an individual monitoring site is the ratio of the average MDA8
ozone concentration in the future year to the average MDA8 concentration in the 2017 base year. The
average values are calculated using MDA8 model predictions in the future year and in 2017 for the 10
highest days in the 2017 base year modeling. High ozone days correspond to days when modeled ozone
MD8A concentration exceeds, or is or equal, to 60 ppb. For cases in which the base year model
simulation does not include 10 days with MDA8 ozone values >= 60 ppb at a site, all days with ozone >=
60 ppb are used in the calculation, as long as there were at least 5 days that meet this criterion. At
monitor locations with less than 5 days with modeled 2017 base year ozone >= 60 ppb, no RRF or FDV is
calculated for the site and the monitor in question is not included in the analysis. A detailed description
of SMAT configuration is provided in the SMAT TSD.150[129]
Following this approach, FDVs and RRFs were calculated for each monitoring site within the
NWF NAA, where FDV for Bountiful, Hawthorne and Herriman were based on an adjusted BDV (Table
[68). BDV for Bountiful, Hawthorne and Herriman, which correspond to the three highest monitors in
the NAA, were adjusted to reflect DVs after exclusion of wildfire smoke-impacted ozone exceedance
values. In a separate technical document (“Analysis in Support of Exceptional Event Flagging and
Exclusion from Modeling for the Weight of Evidence Analysis”), the UDAQ determined that ozone
concentrations exceeding the 2015 ozone NAAQS on August 4, 2016, and September 2, 5 and 6 2017
qualify as wildfire smoke-impacted ozone exceedances. These events were excluded from the 2017 BDV
calculations for Hawthorne, Bountiful and Herriman. Excluding these events results in a decrease of 1.7 -
2.0 ppb in the BDV and 2.0 ppb in the FDV for these sites (Table [68]70). Note that consistent with the
truncation and rounding procedures for the 8-hour ozone NAAQS, the projected DVs are truncated to
the first decimal place in units of ppb.

[128]149 https://www.epa.gov/scram/photochemical-modeling-tools & UDAQ Ozone SIP SMAT-CE Configuration Utah Division of Air Quality TSD:
https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001838.pdf
[129]150 UDAQ Ozone SIP SMAT-CE Configuration Utah Division of Air Quality: https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001838.pdf

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Table [68]70: Baseline design values (BDV), relative response factors (RRF), future design values (FDV) at Bountiful, Hawthorne
and Herriman monitoring locations. DVs before and after exclusion of days impacted by wildfire smoke are shown.* indicates DV
after removal of wildfire smoke-impacted ozone exceedance values.
Flagged Data Not Excluded
3x3 grid-cell array Max Paired
in Space
Flagged Data Excluded
3x3 grid-cell array Max Paired in Space
Site Site ID County BDV RRF FDV Final
FDV
BDV RRF FDV Final
FDV
Bountiful 490110
004
Davis 76.7 0.9593 73.5 73 75* 0.9593 71.9* 71
Hawthorne 490353
006
Salt
Lake
76.7 0.9698 74.3 74 75* 0.9698 72.7* 72
Herriman 490353
013
Salt
Lake
76 0.9686 73.6 73 75* 0.9686 72.6* 72
Erda 490450
004
Tooele 73 0.9673 70.6 70 73 0.9673 70.6 70
Harrisville 490571
003
Weber 72.7 0.9676 70.3 70 72.7 0.9676 70.3 70

8.2.3 Model Attainment Test
Table [69]71 summarizes the finalized BDV, FDV and RRF at each monitoring site within the NWF
NAA, where the BDV for Bountiful, Hawthorne and Herriman, are adjusted to reflect BDV after removal
of ozone exceedance values impacted by wildfire smoke. Only sites that had an ozone monitor operating
in the 5-year period (2015-2019) were used to calculate the 5-year weighted average ambient BDV and
are currently still part of UDAQ air monitoring network were included in this analysis.
Results show that the FDV are projected to reach between 70 - 72 ppb by the attainment date
across all sites in the non-attainment area, with the Hawthorne monitoring site projected to be the
controlling monitor at 72 ppb. It is important to note the way in which ozone DVs are truncated to the
lowest whole number when being calculated, a FDV of 70.9 ppb is needed to demonstrate attainment.
Therefore, considering the range of projected FDV, monitoring sites that show nonattainment are all
demonstrating FDV very near attaining the standard.

Table [69]71: Baseline design values (BDV), relative response factors (RRF), future design values (FDV) at monitors within the
northern Wasatch Front ozone non-attainment area.
3x3 grid-cell array Max Paired in
Space
Site Site ID County BDV RRF FDV Final FDV
Bountiful 490110004 Davis 75 0.9593 71.9 71
Hawthorne 490353006 Salt Lake 75 0.9698 72.7 72
Herriman 490353013 Salt Lake 75 0.9686 72.6 72
Erda 490450004 Tooele 73 0.9673 70.6 70
Harrisville 490571003 Weber 72.7 0.9676 70.3 70

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8.3 Weight of Evidence (WOE)
8.3.1 Overview
While the modeled attainment demonstration described in section 8.1 (Table [69]71) indicates
that the MDA8 at the Hawthorne monitor will reduce to 72 ppb by the attainment date, slightly above
the 70.9 ppb required to demonstrate attainment, the UDAQ has implemented substantial additional
efforts to combat summertime ozone not accounted for during this modeling effort should be taken into
consideration when determining if the area is demonstrating attainment. In this section, as part of a
WOE approach151[130], the UDAQ will present an overview of additional efforts and analysis to provide
further insights into to be considered when determining if the area is demonstrating attainment.
8.3.2 Uncertainties in Modeling and Inventory
While the photochemical modeling results presented in section 8.1 meet EPA performance
metrics and represent a significant improvement in past efforts to model ozone in the NWF, there are
uncertainties in any modeling effort that may result in an overestimation in future predicted ozone
concentrations.
These uncertainties can result from a wide array of parameters involved in complex modeling
efforts, including the process of compiling the emission inventories modeling efforts rely on. For
instance, the mobile on-road sector of the inventory is estimated using models developed by the EPA
that have many versions EPA released over the years. Estimations of NOx have differed significantly as
one model replaced the next, and changes in the vehicle fleets over time such as the electrification of
the mobile sector may be underrepresented (see section 8.3.4). Further, since SIPs are legally binding
documents and will be enforced in the event certain conditions are not met, emission reductions
associated with past SIP efforts have included conservative estimates of total reductions. Therefore,
emission reductions accounted for in inventories may underrepresent the full extent of real-world
reductions.
Additionally, for the development of the attainment demonstration included in this SIP revision,
the UDAQ relied on VOC emissions estimates within the solvent sector from an EPA supplied product.
This product, VCPy, has substantial benefits over past methods used in the quantification of emissions
within this category. However, some uncertainties remain in the emission estimates produced by VCPy
that could result in overestimations of VOC emissions within the NWF NAA. For instance, as described in
section 3.2.2, this SIP revision sourced its VOC emissions for the solvents sector from EPA’s 2016v2
platform. EPA has subsequently released an updated version (2016v3) of this platform152[131] in which
EPA revised its estimated for Utah statewide VOC emissions as adjusted to account for “indoor usage
assumptions” as well as “control assumptions”. These updates resulted in a statewide decrease of
estimated VOC emissions by 1,699 tpy. As these emissions are generally allocated in modeling based on
population metrics, and the NWF represents a significant proportion of Utah’s population, it stands to
reason that the majority of the decrease in VOC emission from 2016v2 to 2016v3 would be observed in
the NWF NAA.

[130]151 Modeling Guidance for Demonstrating Air Quality Goals for Ozone, PM 2.5, and Regional Haze
[131]152 Technical Support Document (TSD): Preparation of Emissions Inventories for the 2016v3 North American Emissions Modeling Platform. U.S. EP A. January
2023

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8.3.3 Background, Interstate, and International Transport
8.3.3.1 Background Ozone
The EPA identifies “background” ozone in the United States (USB) as ozone formed from sources
or processes other than anthropogenic emissions of NOx, VOCs, methane (CH4) and CO originating from
within the United States.153 [132] This definition does not include intra or inter-state transport of ozone
impacting downwind areas, which are covered by other sections of the CAA including section
110(a)(2)(D). NAAs in the Intermountain West face significant and regionally specific challenges meeting
ozone standards especially as it relates to the amount of USB present.154[133] The region faces further
challenges due to the increasing instances of wildfire,155[134] significant regional and local biogenic
contributions,156[135] as well as the influence of internationally transported pollutants,157[136] all of which
contributing to a large proportion of ozone on any given day. These challenges are highlighted in
multiple analysis identifying significantly elevated USB ozone concentrations throughout the region
when compared to the eastern United States.158[137]
The substantial contribution of USB ozone impacting Utah’s total ozone concentrations and can
be seen at the remote sites located throughout the state, such as the monitoring sites located in
Escalante National Monument, or Bryce and Canyonlands National Parks. These sites are typically free of
impacts from localized anthropogenic emissions, and they regularly report 8-hour summertime ozone
concentrations above 0.050 ppm. Source apportionment modeling performed by the UDAQ (see section
9.2 for details) further found USB ozone concentrations (including interstate anthropogenic emissions)
along the Wasatch Front account for up to 85.5% of the ozone comprising the daily 8-hour
concentrations observed at the Hawthorne site (Figure [15]16 and Figure [16]17), with the remaining
14.5% attributable to Utah anthropogenic emissions.

[132]153 Implementation of the 2015 Primary Ozone NAAQS: Issues Associated with Background Ozone”. USEPA, December 2015
[133]154 Scientific Assessment of background ozone over the U.S.: Implications for air quality management
[134]155 Buchholz, R.R., Park, M., Worden, H.M. et al. New seasonal pattern of pollution emerges from changing North American wildfires. Nature Communications
13, 2043 (2022). https://doi.org/10.1038/s41467-022-29623-8
[135]156 EPA Webinar; Description and preliminary evaluation of BELD 6 and BEIS 4. ORD. Jesse O. Bash and Jeff Vukovich
[136]157 Entrainment of stratospheric air and Asian pollution by the convective boundary layer in the southwestern U.S.; Langford, A.O . et al. (2017), J. Geophysics.
Res. Atmos., 122, 1312-1337, doi:10.1002/2016JD025987
[137]158 Entrainment of stratospheric air and Asian pollution by the convective boundary layer in the southwestern U.S.; Langford, A.O . et al. (2017), J. Geophysics.
Res. Atmos., 122, 1312-1337, doi:10.1002/2016JD025987 & Implementation of the 2015 Primary Ozone NAAQS: Issues Associated with Background Ozone; USEPA,
December 2015

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Figure [15]16: Ozone Attributed to Domain-Wide Sources at Hawthorne as simulated 8-hour daily ozone concentrations along
the Wasatch Front.

Figure [16]17: Episode average of simulated 8-hour daily ozone concentrations at Hawthorne along the Wasatch Front.

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8.3.3.2 Interstate Transport
In 2022, as part of its ongoing efforts to model nationwide ozone and transport of precursor
emissions, the EPA released results from its updated North American Emission Modeling Platform
2016v2. This analysis identified the contributions from multiple upwind states for the modeled year of
2023 to ozone concentrations along the NWF NAA (Table [70]72).159[138] The states impacting the NWF
NAA include California, Nevada, Arizona, Idaho, Oregon, and Washington. The combined contributions
to counties in the NWF from these upwind states result in impacts ranging from 4.0 ppb to 4.91 ppb.
Given that the attainment demonstration described in section 8.2 identified the FDV of 72 ppb for Salt
Lake, and 71 ppb for Davis counties, the combined upwind contribution from western states accounts
for 6 - 7% of the total predicted ozone concentrations in the NWF NAA.

Table [70]72: 2023 contributions from upwind states to NWF NAA (ppb) as identified by EPA 2016v2 modeling
Salt Lake Davis Weber
California 2.46 2.25 2.24
Nevada 0.89 0.86 0.58
Arizona 0.22 0.22 0.13
Idaho 0.55 0.37 0.57
Oregon 0.58 0.44 0.41
Washington 0.21 0.16 0.13
Total 4.91 4.30 4.06

Section 110(a)(2)(D)(i)(I) of the CAA, known as the “Good Neighbor” provision, requires states
with a contribution more than the EPA’s determined significance threshold to develop a SIP revision
with provisions to address contributions to downwind states. This threshold was set at 1% of the
NAAQS, or 0.7 ppb for the 2015 ozone NAAQS. Of the six states listed in Table [70]72, both California
and Nevada were identified by the EPA as contributing to Utah’s ability to attain or maintain the NAAQS
in a regulatorily significant way (>= 0.7 ppb). On April 4, 2022, the EPA proposed a Federal
Implementation Plan (FIP) to address disapprovals or deficiencies in twenty-six states’ Good Neighbor
SIPs, including those of California and Nevada.160[139] The proposed FIP will require emission reductions
from an array of industrial activities including fossil fuel-fired power plants, natural gas pipeline
transportation, cement production, glass, iron and steel manufacturing, as well as reductions from
chemical, petroleum, and paper manufacturing processes. If the proposed FIP becomes final, emission
reductions covered under this rule will begin taking effect the summer of 2023, with full implementation
of emission reductions by summer 2026. Given that California and Nevada combine to generate upwind
contributions of 3.35 ppb of ozone to the NWF NAA, as these proposed controls take effect, they may
further aid in the NWF NAA’s ability to attain the standard by the attainment date.

8.3.3.3 International Transport
The transport of ozone and its precursor emissions from international sources will be discussed
in depth in section 9 of this SIP revision. However, international contributions to ozone along the

[138]159 Federal Implementation Plan Addressing Regional Ozone Transport for the 2015 Ozone National Ambient Air Quality Standard, 87 Fed. Reg. 20,036 (April 6,
2022).
[139]160 Id.

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Wasatch Front, much like interstate contributions described in section 8.3.3.2, plays an important role in
the area’s observed ozone concentrations and the NWF NAA’s ability to meet ozone health-based
standards. Thus, it is important to include a discussion of international contributions in a WOE analysis.
In short, emissions from international sources have long been shown to impact ozone
concentrations throughout the Intermountain West.161[140] These studies generally identified
international contributions in the range of 3 – 4 ppb, predominantly observed as contributing to USB
ozone conditions. International contributions tend to be relatively consistent throughout the spring and
summer seasons. The range of international contributions reported in these studies are similar in scale
to those seen from upwind states impacting the NWF NAA as described in section 8.3.3.2 and shown in
Table [70]71.
To examine international contributions to the NWF NAA, the UDAQ conducted source
apportionment modeling (see section 9.2 for details), in which international contributions were tagged.
The results of this exercise (Figure [17]18 & Figure [18]19) identified a contribution of 6.2% of ozone
along the Wasatch Front attributable to international transport on non-exceedance days, with a similar
but slightly higher contribution identified during exceedance days of 6.7%. While the model
underestimates absolute ozone concentrations when compared to monitored values, and thus absolute
apportioned contributions should be considered with that limitation in mind, the reported
concentrations of international contributions range from 3.74 ppb over the episode and average, up to
4.5 ppb on the top 10 modeled exceedance days. This range is well in line with those reported in the
literature and is highly similar in scale when compared to inter-state transport contributions.

[140]161 Langford, A.O., Alvarez, R.J., Brioude, J., Fine, R., Gustin, M.S., Lin, M.Y., Marchbanks, R.D., Pierce, R.B., Sandberg, S.P., Senff, C.J., Weickmann, A.M.,
Williams, E.J., 2017. Entrainment of stratospheric air and Asian pollution by the convective bou ndary lauer in the southern U.S. J. Geophysical Res. Atmos., 122,
1312-1337, doi:10.1002/2016JD025987 & Jaffe, D.A., O.R. Cooper, A.M. Fiore, B.H. Henderson, G.S. Tonnesen, A.G. Russell, D.K. Henze, A.O. Langford, M. Lin, T.
Moore, 2018. Scientific assessment of background ozone over the U.S.: Implications for air quality management. Elem. Sci. Anth., 6: 56. DOI:
https://doi.org/10.1525/elementa.309.

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Figure [17]18: Ozone Attributed to Domain-Wide Sources

Figure [18]19: Domain-Wide OSAT exceedance vs. non-exceedance days

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8.3.3.4 Federal vs. State Regulatory Authority
As noted in Utah’s comments162[141] submitted to EPA on EPA’s proposed FIP for interstate
transport,163 [142] “A significant portion of states’ total contribution to downwind areas include emissions
that states have limited regulatory authority and, in some cases, no regulatory authority at all, including
emissions that are federally regulated.” These federally regulated emission sources include the mobile
sector, an area in which the state has significantly limited authority to regulate due to CAA section 209’s
preemption. This is particularly relevant for anthropogenic NOx emissions, which are dominated by the
mobile sector. For the NWF NAA, the emissions from federally regulated sources account for 55.96 tpd
(64%) of the total NAA NOx inventory, and 29.8 tpd (33%) of the VOC inventory (section 3).
The discrepancy between regulatory authority can be further seen in Figures 15 – 18, where
federally regulated sources account for 59.7% of the ozone attributable to anthropogenic emissions,
while emissions under state authority account for the remaining 40.3% of ozone formation. As the state
of Utah strives to attain the NAAQS, it is doing so with limited authority to reduce a substantial portion
of the emissions contributing to the formation of ozone within the NAA.
8.3.4 Trends in Emissions
Trends in emission reductions along the Wasatch Front are presented in Table [71]73, providing
further evidence that the area is progressing towards attaining the standard by the attainment date. As
described in detail in section 3 and section 7 of this SIP revision, the NWF NAA has experienced
substantial emission reductions of both anthropogenic VOCs and NOx during the corresponding years of
this implementation timeframe—2017 to 2023. During this time, NOx emissions decreased by 21.3 tpd
and VOC emissions decreased by 3.7 tpd in large part due to improvements in the on-road mobile sector
and as a result of past SIP efforts.

Table [71]73: NOx and VOC reductions resulting from PM2.5 SIPs.
State Implementation Plan Years NOx Reduction
(tpd)
VOC Reductions
(tpd)
*Salt Lake City Moderate PM2.5 SIP (2014)164
[143]
2010 - 2015 24.86 27.57
*Salt Lake City Serious PM2.5 SIP (2019)165
[144]
2016 - 2020 15.75 8.27
Total 40.61 35.84
* Includes portions of Box Elder County which is not included in NWF ozone NAA

As shown in Table [71]73, past SIP efforts have resulted in significant reductions of NOx and VOC
emissions along the Wasatch Front. Additionally, as described in detail in section 7.3 and section 7.4, the
areas have experienced significant decreases in both precursor pollutants as a result of improvements to
the mobile on-road sector associated with lower emissions from Tier 3 fuels and engines. Beyond the

[141]162 Docket ID No. EPA-HQ-OAR-2021-0668, Federal Implementation Plan Addressing Regional Ozone Transport for the 2015 Primary Ozone National Ambient
Air Quality Standard. Comments Submitted by Utah Department of Environmental Quality (UDAQ). DAQP-055-22. June 21, 2022
[142]163 87 Fed. Reg. 20,0036.
[143]164 Utah State Implementation Plan Section IX. Part A.21; Control Measures for Area and Point Sources, Fine Particulate Matter, PM2.5 SIP for the Salt Lake
City, UT NAA
[144]165 Utah State Implementation Plan Section XI. Part A.31; Control Measures for Area and Point Sources, Fine Particulate Matter, S erious Area PM2.5 SIP for the
Sal Lake City, UT NAA.

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inventoried reductions, these reductions likely underestimate the full extent of emission reductions in
this sector since they fail to capture Utah’s high adoption rate of zero emission vehicles (ZEV),
predominantly in the light duty sector. The growth of ZEV and electric-hybrid vehicles has grown 940.3%
and 101.6% respectively from 2015 – 2021 in the state of Utah.166 [145] While the total proportion of ZEV
and electric-hybrid vehicles in Utah’s fleet was still relatively low, at ~2.4% in 2021167[146], given the
growth rate of electric vehicle (EV) adoption in the state, and the fact that Utah is ranked fifth in the
nation for access to EV charging infrastructure per capita,168 [147] the percentage of Utah’s on-road fleet is
likely to continue to shift towards ZEV and low emission vehicles which will further advance emission
reductions in this sector.
In addition to the potential underestimation in the electrification of the on-road mobile sector,
further market penetration of Tier 3 fuels is expected to continue. In 1970, the EPA set the first light-
duty vehicle emission standards. These standards have been updated over time with generations of the
standard termed Tier 1, Tier 2, and most recently, Tier 3. The Tier 2 and Tier 3 standards also included
sulfur standards for gasoline to help ensure that vehicle emissions control operates optimally. By 2025,
NOx emission standards for light-duty vehicles will represent a 98% improvement from 1975 levels, with
sizable improvements for VOCs.
The UDAQ anticipates that the transition from Tier 2 and older vehicles to Tier 3 vehicles will
yield dramatic reductions in ozone precursor emissions. While MOVES modeling attempts to capture
these emissions reductions, and thus should be represented to some degree in emissions inventories
used for this SIP revision, it is important to note that Utah has taken significant additional steps to
ensure that the benefit of the Tier 3 vehicle and fuel standards is fully realized throughout the NWF NAA
and thus some emission reductions may be underestimated in this modeling demonstration.
Unlike many other metropolitan areas throughout the U.S., the NWF is served by the relatively
small number of refineries. Importantly, all but one of these refineries (Sinclair) are considered to be
“small volume” under the Tier 3 regulations169[148] – i.e., they produce less than 75,000 barrels per day.
Because of this, and due to the older age of facilities in the NWF, it may be more cost-effective for
operators to comply with Tier 3 regulations by upgrading their larger, or newer, refineries elsewhere
and using credits generated at these facilities and the averaging, banking, and trading provisions of the
Tier 3 rule to comply in Utah. This compliance structure would result in higher-sulfur gasoline being sold
throughout the NWF NAA, which would erode the benefits of Tier 3 fuels.
Although states are restricted from directly establishing new fuel requirements by the Energy
Policy Act of 2005, the State of Utah has used a combination of state-led pressure, public awareness
initiatives, and incentives in the form of tax credits, to encourage refineries to produce Tier 3 fuel
instead of using credits to comply, giving UDAQ greater confidence that the full benefits of the Tier 3
fuels will be realized locally. This is especially important in the early years of the Tier 3 program when
most of the emissions reduction benefits stem from using Tier 3 fuels in Tier 2 and older vehicles. In
particular, the WFRC found that the use of Tier 3 fuel in existing light-duty vehicles results in a NOx
reduction of 14.5% and in a VOC reduction of 3.9% as compared with the same vehicles using Tier 2 fuel

[145]166 Adoption of Electric and Alternative Fuel Vehicles. OFFICE OF LEGISLATIVE RESEARCH AND GENERAL COUNSEL; May 18, 2021:
https://le.utah.gov/interim/2021/pdf/00002047.pdf
[146]167 Adoption of Electric and Alternative Fuel Vehicles. OFFICE OF LEGISLATIVE RESEARCH AND GENERAL COUNSEL; May 18, 2021:
https://le.utah.gov/interim/2021/pdf/00002047.pdf
[147]168 https://www.governing.com/next/new-data-shows-states-ith-highest-and-lowest-number-of-ev-charging-stations?utm_campaign=Newsletter%20-
%20GOV%20-%20Daily&utm_medium=email&_hsmi=235987835&_hsenc=p2ANqtz--VWjg_LxXqDi4qNgUMKfC7NQ8O47DG-
58ltMXtUweN0QB986ZcszciRfLRxIBQmqBB1mJcfUdxIrvMrh7tWVVucfX1yw&utm_content=235987835&utm_source=hs_email
[148]169 81 FR 23641: Amendments Related to: Tier 3 Motor Vehicle Emission and Fuel Standards

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(30 ppm sulfur).170[149] These dramatic benefits begin to accrue almost immediately after the first few
refueling cycles once the lower-sulfur fuel is available, making the State’s efforts to bring these cleaner
burning fuels to the NWF NAA critical for reducing ozone precursor emissions and ultimately
demonstrating attainment of the NAAQS.
There are seven refineries that provide the majority of the fuel consumed within the NWF NAA.
Five of those refineries are located in the NWF NAA, while two additional facilities – the Sinclair
refineries in Sinclair and Casper, WY – are connected to the NWF via a product pipeline. Utah has
received public commitments from all but one of these refineries that the fuel provided along the
Wasatch Front meets the Tier 3 10-ppm sulfur average requirements. The last remaining refinery is
expected to make the full transition to Tier 3 fuels by 2024.171[150] As the last of Utah’s refineries makes
the transition to refining and distributing the cleaner burning Tier 3 fuels, additional potentially
underestimated reductions in estimated on-road mobile emissions are possible.
In addition to potential underestimations of on-road emission reductions, the state of Utah has
taken steps to reduce emissions through improving the effectiveness of existing administrative rules. On
February 1, 2023, the Utah Air Quality Board adopted amendments to Utah Administrative Rule R307-
328; Gasoline Transfer and Storage. These amendments resulted in the addition of clarifying language to
the rule which requires all gasoline service stations to install pressure relief valves to underground
storage tanks. While the requirement for pressure relief valves was preexisting in R307-328, the
language did not adequately explain the requirements. The UDAQ had identified 266 underground
storage tanks located in the NWF NAA that either did not have, or could not be confirmed to have, the
required pressure relief valve. The resulting emission reductions from these amendments are not
represented in the inventory since the inventory assumed compliance with this requirement, however
these amendments will result in additional reductions of VOC emissions within the NWF NAA.
8.3.5 Unaccounted Controls and Emission Reductions
As described in section 7, emissions reductions that are creditable towards RFP, and thus
included in a subsequent attainment demonstration, emission reductions have strictly prescriptive
requirements attached. While the attainment demonstration in this SIP revision utilized inventories that
attempt to quantify emission reductions associated with past SIP work and improvements to the on-
road sector, the inventory does not account for emission reductions associated with non-RFP creditable
reductions. However, the state of Utah has multiple and extensive incentive and non-creditable
emission reduction programs that result in substantial emission reductions. As a result, the attainment
demonstration outlined in Section 8.2 does not fully account for ongoing emission reduction in, and
around, the NWF NAA. This section highlights these programs and, where possible, reports emission
reductions associated with these programs. Some of these programs include regions beyond the NWF
NAA, however being the most densely populated region in the State, a substantial portion of the
emission reductions highlighted in this section are targeted to areas within the NAA boundary.

8.3.5.1 Utah Clean Diesel Program (UCDP) and Diesel Emission Reduction Act (DERA)
Utah’s Clean Diesel Program provides incentives to fleet owners to retire older vehicles and
replace them with newer vehicles that meet more stringent emission standards. The program began in

[149]170 “Improved air quality through the use of Tier 3 fuels in Utah", Utah Clean Air Caucus, June 14, 2016
[150]171 “Four Utah refineries now produce cleaner Tier 3 fuels, and the fifth says it will soon.” Salt Lake Tribune. January 22, 2023:
https://www.sltrib.com/renewable-energy/2023/01/22/four-utah-refineries-now-produce/

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2008 and will continue beyond this SIP revision and includes incentives available under the Diesel
Emission Reduction Act (DERA)172[151] and the National Clean Diesel (NCD) program. Table [72]73
indicates the annual targeted number of vehicles included in the program and their estimated annual
and lifetime emission reductions for both NOx and VOCs for the years associated with this SIP revision.

8.3.5.2 Volkswagen Settlement Funds
In 2016, Volkswagen (VW) entered into a settlement173[152] as a result of a lawsuit filed against
the company for defeating emission testing programs and engine certifications for its light-duty diesel
vehicles. The state of Utah was the beneficiary of this settlement and received $35,177,506. The Utah
Department of Environmental Quality was designated as the lead agency to administer this funding,
which has been used to replace older class 4 – 8 freight trucks, school buses, shuttle and transit buses,
fund electrical vehicle supply equipment, and assist the Diesel Emissions Reduction Act (DERA) program
described in section 8.2.6.1. The results of this program are highlighted in Table [72]74.

8.3.5.3 Vehicle Repair and Replacement Assistance Program (VRRAP)
In 2018 the EPA awarded the state of Utah with Targeted Air Shed Grant funding. Targeted Air
Shed Grants provide funds to reduce air pollution in the nation’s NAAs with the highest levels of ozone
and PM2.5. UDAQ application was for the development of a Vehicle Repair and Replacement Assistance
Program (VRRAP) for the Salt Lake PM2.5 NAA.
Through the VRRAP, low-income individuals with a vehicle that fails an emissions inspection are
offered funding assistance to either repair the vehicle or replace it with a newer, cleaner vehicle.
Qualifications for financial assistance are based on a matrix that considers the vehicle owner’s
household income as a percent of the national income poverty level, the value of the repairs being done
on the vehicle, and the vehicle’s mechanical life expectancy. The program is set up to augment and
improve the overall effectiveness of counties’ I/M programs.
Since starting in 2020 the VRRAP has repaired 163 and replaced 48 vehicles. UDAQ expects
these activities to reduce emissions annually by 1.26 tons of Nonmethane Organic Gas (NMOG) and NOx
and reduce lifetime emissions of NMOG and NOx by 11.17 tons (Table [72]74).

[151]172 42 U.S.C. §§ 16131 through 16137.
[152]173 VOLKSWAGEN “CLEAN DIESEL” MARKETING, SALES PRACTICES, AND PRODUCTS LIABILITY LITIGATION. Case Number: MDL No. 2672 CRB (JSC)

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Table [72]74: Emission reductions associated with incentive programs in and around the NWF NAA. * VOC emission reductions
not available. ** Combined NOx and NMOG emission reductions
Year Vehicles
Replaced
NOx Annual
Reduction (tpy)
NOx Lifetime
Reduction (tpy)
VOC Annual
Reduction (tpy)
VOC Lifetime
Reduction (tpy) Program
2017 95 35.77 144.19 8.68 12.77 DERA / NCD
2018 87 9.66 176.40 0.89 16.91 DERA / NCD
2019 60 20.91 62.73 1.04 3.12 DERA / NCD
2020 44 4.75 14.26 0.55 1.65 DERA / NCD
2021 59 7.2 26.34 0.66 2 DERA / NCD
2019 -
Ongoing 78 23.49 10.34 * * VW
Settlement
2020 -
Ongoing 48 11.17** 1.26** ** ** VRRAP
2022 13 1.54 4.62 NCD
Total 484 103.32 438.88 11.82 36.45

8.3.5.4 Diesel I/M Programs
In 2018 the Utah State Legislature passed H.B. 101, which established a pilot program to require
diesel vehicle emissions inspections in Utah County. This program was made permanent in 2021 when
the Utah State Legislature passed S.B. 146. While diesel I/M programs have not historically been
awarded SIP emissions reduction credit, UDAQ nevertheless anticipates additional NOx and VOC
emissions reductions from this program. Currently, all counties that are required to have an emission
inspection program are required to have a diesel emissions program for vehicles model year 2007 or
newer with a gross vehicle weight of 14,000 pounds or less (see 41-6a-1642(7)). Salt Lake and Davis
Counties also require all diesel vehicles to go have an emission inspection.

8.3.5.5 Lawn & Garden Equipment Exchange Program
Beginning in 2015, as part of the Utah Clean Air Retrofit, Replacement, and Off-Road Technology
(CARROT) program,174[153] the UDAQ has administered a lawn and garden exchange program aimed at
replacing gas powered lawn and garden equipment with zero emission alternatives. This equipment
includes lawn mowers and string trimmers but is expected to be expanded in the coming years to
include a wider array of 2-stroke lawn and garden equipment. Since 2017, this program has replaced an
estimated 6,638 pieces of summertime operated lawn and garden equipment resulting in an estimated
reduction of 0.13 tpy of NOx and 2.26 tpy of VOCs.

[153]174 Utah Code Ann. §§ 19-2-201 through 19-2-204.

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8.3.5.6 UCAIR Summer Education Program
The Utah Clean Air Partnership (UCAIR) is a statewide non-profit entity created to bring together
individuals, business, and communities to help improve Utah’s air. In 2022, UCAIR received a grant from
the Utah Department of Environmental Quality to conduct an outreach and education campaign aimed
at educating Utah’s population about summertime ozone pollution. The campaign ran from July 5
through September 11, 2022. During this time the campaign measured over 45 million unique
impressions through a combination of television (2.9 million), outdoor (27.68 million) and online (14.45
million) outlets. Post-campaign research identified that 92% of residents were concerned with the air
quality where they live during summer ozone season, with 99% of respondents familiar with personal
actions they can take to improve air quality.

8.3.5.7 UCAIR Personal Fuel Can Exchange Program
In addition to the education campaign discussed in section 8.3.5.6, UCAIR operates a Personal
Fuel Canister (PFC) exchange program, in which UCAIR collects and recycles old PFCs and replaces them
with EPA compliant canisters, which reduces VOC emissions associated with the evaporative loss of
gasoline. The program began targeting PFCs for replacement in 2019, and since that time has
successfully upgraded over 5,000 PFCs in Utah’s NAAs.

8.3.5.8 UTA Free Fare Days
In 2019, Utah enacted H.B. 353: Reductions of Single Occupancy Vehicle Trip Pilot
Program.175[154] This bill designated the UDAQ as the lead agency in administering a program to make all
public transit free on days associated with poor air quality in an attempt to reduce emissions associated
with vehicle emissions. While much of this program was aimed at reducing emissions during Utah’s
wintertime PM2.5 season, the program has been enacted during two separate periods of high
summertime ozone. These “free fare days” were August 12 - 13 of 2021, and September 1 - 2 of 2022.

8.3.5.9 Surge Teleworking
During the 2021 legislative session, Utah adopted S.B. 15: Workforce Solutions for Air Quality.
This bill encourages eligible State employees to telecommute on mandatory action days for air quality
and on other special circumstances to help decrease on-road emissions. This law covers an estimated
10,185 eligible state employees and contributes to reductions of NOx and VOC emissions on ozone
exceedance days throughout the NAA.

8.3.5.10 Emission Reductions Beyond the NAA Boundary
On July 6, 2022, the Utah Air Quality Board adopted SIP revisions including Utah’s Second
Implementation Period for Regional Haze176[155] and associated emission limits177[156]. The emission
reductions associated with these actions are broad and include the following measures: (1) requiring
flue gas recovery on boilers at US Magnesium by summer of 2028; (2) mandating a shutdown of units 1
and 2 at the Intermountain Generation Station by December of 2027; (3) imposing new plantwide NOx
emission limits for the coal-fired Hunter and Huntington power plants that phase in between July of
2022 and January of 2028; and (4) making many existing permitted limits across the state federally
enforceable. While much of the emission reductions highlighted here are beyond the temporal scope of

[154]175 Id. § 19-2a-104, repealed pursuant to § 63I-1-219, eff. July 1, 2022.
[155]176 Utah State Implementation Plan. Section XX.A, Regional Haze
[156]177 Utah State Implementation Plan, Emission Limits and Operating Practices. Section IX, Part H.21 and Part H.23

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this SIP revision, occur outside of the NWF NAA, or make permanent emission reductions that have
already occurred, they serve to further demonstrate efforts by the state of Utah to reduce ozone
forming precursor emissions.

8.3.5.11 Science for Solutions Applied Research Grants
In 2018, UDAQ received an ongoing annual $500,000 appropriation from the Utah State
Legislature specifically intended to fund applied air quality research projects. In response, the UDAQ
established the competitive Science for Solutions research grant program. Over the last five years,
successful grant applicants have submitted proposals targeting UDAQ’s goals and priorities. In recent
years, UDAQ has placed a high emphasis on improving the understanding of summertime ozone
pollution throughout the NWF NAA.
An abbreviated list of applied research projects funded by the UDAQ’s Science for Solutions
research grant are listed below. These projects focus on summertime ozone in the NWF NAA:

• The Salt Lake Regional Smoke, Ozone and Aerosol Study (SAMOZA); University of Washington
• Improving Smoke Detection and Quantifying the Wildfire Smoke Impacts on Local Air Quality
Using Modeling and Machine Learning Techniques; University of Utah
• Improved Vegetation Data for the Biogenic Emission Inventory of Wasatch Front; Ramboll US
Consulting
• Impacts of the Great Salt Lake on Summer Ozone Concentrations Along the Wasatch Front;
University of Utah
• Development of a WRF-based Urban Canopy Model for the Greater Salt Lake City Area;
Brigham Young University
• Quantitative Attribution of Wildfires on Summertime Ozone Concentrations along the Wasatch
Front; San Jose State University
These projects, along with others, were specifically funded to improve UDAQ’s SIP model
performance and better inform state policy and rulemaking. Science for Solutions projects have already
made a difference in improving UDAQ’s model performance. For example, these projects have improved
shortwave albedo in the CAMx model to realistically reflect salt-crust and playa surfaces around the
Great Salt Lake. UDAQ also learned more about the unique role of halogens in ozone formation in the
Salt Lake Valley. Motivated by this information, UDAQ funded the development of an enhanced
chemical mechanism (CB6r5h) that includes a broader range of halogen pathways to use in our air
quality modeling. These enhancements have led to demonstrable improvements in model performance.
Future projects will help UDAQ determine critical factors in summertime ozone formation.
Biogenic emissions are a large source of uncertainty in the region. Recent evaluations of BEIS/BELD have
shown that isoprene, a key reactive biogenic VOC, is largely underpredicted in regional modeling.
Through Science for Solutions, UDAQ is funding a comprehensive project to greatly improve inputs (e.g.,
leaf area index, tree species) to biogenic models using local information and high-resolution satellite
imagery. In addition, UDAQ is funding projects to better understand wildfire impact on ozone pollution.
These projects will not only enhance UDAQ’s understanding of wildfire contributions to ozone
concentrations throughout the NWF NAA but will also improve the UDAQ’s understanding of local
contributions.

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8.4 Conclusion
Results of any modeled outcome will include some degree of uncertainties. As a result of these
uncertainties, it is important to consider additional factors within the range of those uncertainties and
consider factors beyond the scope of the analysis. The predicted FDV for ozone concentrations outlined
in section 8.2, paired with the additional WOE analysis, results in a strong case that this attainment
demonstration adequately demonstrates the NWF NAA attaining the 8-hour ozone NAAQS by the
attainment date of August 3, 2024.

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Chapter 9 - 179B(a) Prospective Demonstration
9.1 Overview
Section 179B(a) of the CAA states that a SIP revision shall be approved by the EPA if the state
can demonstrate that the implementation plan is “adequate to attain and maintain the relevant national
ambient air quality standards... but for emissions emanating from outside of the United States.”178[157] As
noted in the preambles of both the 2008179[158] and 2015180[159] ozone implementation rules, section
179B of the CAA does not prohibit non-international border states from submitting a demonstration.
However, as noted in EPA guidance,181[160] demonstrations from states that do not directly share an
international border will require additional technical rigor compared to international border areas.
Section 179B of the CAA has two mechanisms to demonstrate that international contributions
impact a NAA’s ability to attain or maintain a NAAQS. A state may demonstrate independent of a SIP
revision that a NAA would have attained the standard at a past attainment date but for the presence of
international emissions, known as a retrospective 179B(b) demonstration, and thus should not be
advanced in nonattainment classifications.182[161] Conversely, a state may demonstrate as part of a SIP
revision that a NAA will attain the standard by a future attainment date, but for the presence of
international emissions. This is known as a prospective 179B(a) demonstration.183[162]
There are also substantial differences in the outcomes of approved prospective and
retrospective 179B demonstrations. An approved retrospective 179B(b) acts to prevent a NAA from
being further redesignated to a more stringent nonattainment status. A prospective 179B(a) however,
acts as additional information used by the EPA in determining if a SIP modeling attainment
demonstration adequately demonstrates attainment by the attainment date, but for the presence of
international emissions. As a result, a NAA with an approved 179B(a) demonstration that subsequently
fails to attain the standard by the attainment date would not be prevented from a further
reclassification to a more stringent nonattainment status.
On May 28, 2021, the UDAQ submitted to the EPA for consideration a retrospective 179B(b)
demonstration for the NWF NAA184[163] for the marginal attainment date of August 3, 2021. In the
demonstration, UDAQ provided three separate analyses examining international contributions including
a synoptic weather analysis, Hybrid Single–Particle Lagrangian Integrated Trajectory (HYSPLIT) backward
dispersion modeling, and photochemical modeling results performed by a third party showing that the
area would have attained the standard by the marginal attainment date, but for the presence of
international contributions.
Upon publication of the Determination of Attainment by the Attainment Date,185[164] the EPA
found Utah’s demonstration was not approvable and subsequently reclassified the area as a moderate

[157]178 42 U.S.C. § 7509a(a)(2).
[158]179 Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State Implementation Plan Requirements, 80 Fed. Reg. 12,264 (March 6,
2015).
[159]180 Implementation of the 2015 National Ambient Air Quality Standards for Ozone: NAA State Implementation Plan Requirements, 83 F ed. Reg. 62,998 (Dec.
6, 2018). s
[160]181 Guidance on the Preparation of Clean Air Act Section 179B Demonstrations for NAAs Affected by International Transport of Emissions (Dec. 2020) (179B
Demonstrations Guidance).
[161]182 42 U.S.C. § 7509a(b)-(d); see also 179B Demonstrations Guidance at 15-18.
[162]183 42 U.S.C. § 7509a(a); see also 179B Demonstrations Guidance at 12-15.
[163]184 Retrospective 179B(b) Demonstration for Utah’s Northern Wasatch Front Ozone NAA. May 28, 2021. DAQP -048-21
[164]185 87 Fed. Reg. 60,897.

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NAA. The EPA cited four primary reasons for its disapproval186[165] including: (1) a lack of technical
information; (2) a divergence in interpretation of section 179B including the importance of the
proportion of local versus international contributions; (3) a failure to demonstrate sufficient
implementation of feasible emission reduction measures; and (4) the presence of a nearby NAA that
attained the standard despite the presence of international contributions.
In this section, the UDAQ will demonstrate attainment under Section 179B(a) prospectively,
using an updated and improved photochemical modeling, that the NWF NAA would attain the 2015 8-
hour ozone NAAQS by the attainment date of August 3, 2024, but for the presence of international
emissions. Further, UDAQ will utilize and expand on the wealth of technical information included in this
SIP revision to address each of EPA reasons for denying Utah’s previous 179B(b) demonstration.
9.2 Ozone Source Apportionment (OSAT) Modeling
To determine the contribution of different source emission groups and regions to measured
ozone concentrations at individual monitoring sites within the NAA, OSAT modeling was performed
using emissions projected to 2023. Modeling was conducted using the OSAT tool in CAMx v7.1, which
was used for this SIP demonstration modeling as described in section 8. At the request of the UDAQ,
OSAT was integrated by Ramboll (developer of CAMx) with CB6r5h in a special version of CAMx v7.1.
CB6r5h (version 6, revision 5 with halogens) gas-phase chemical mechanism, which includes halogens
chemistry and was specifically developed by Ramboll for this SIP application, was used for all modeling
simulations. Source apportionment was conducted for the 4 and 1.33 km domains, where the two
domains were run in a two-way nested configuration. 2023 emission inputs were used for source
apportionment modeling.187[166] Meteorological fields, ozone column values and photolysis rates
remained unchanged from those used for the attainment demonstration modeling. Six geographic
source regions were used in the source apportionment modeling (Figure [19]20), where each county
within the NAA was considered as an individual region (Salt Lake, Davis, Weber, Tooele counties).
Counties within Utah but outside the NAA were considered as a single region (Other Utah). Regions
within the 4 km domain but outside the State of Utah were considered as a single region. 25 different
source emission sectors were considered for this OSAT simulation and tracer species that track ozone
formation from VOC and NOx emissions from these source categories were tagged. Source groups that
were considered in OSAT included emissions from consumer solvents, on-road heavy duty mobile source
emissions, on-road light duty mobile source emissions, lawn and garden equipment emissions, point
source emissions, biogenic emissions, in addition to several other source emission sectors. A complete
list of these source emission groups is provided in Table 75.
[Six geographic source regions were used in the source apportionment modeling (Figure [19]20), where each county within the
NAA was considered as an individual region (Salt Lake, Davis, Weber, Tooele counties). Counties within Utah but outside the
NAA were considered as a single region (Other Utah). Regions within the 4 km domain but outside the State of Utah were
considered as a single region. 25 different source emission sectors were considered for this OSAT simulation and tracer species
that track ozone formation from VOC and NOx emissions from these source categories were tagged. Source groups that were
considered in OSAT included emissions from consumer solvents, on-road heavy duty mobile source emissions, on-road light duty
mobile source emissions, lawn and garden equipment emissions, point source emissions, biogenic emissions, in addition to
several other source emission sectors. A complete list of these source emission groups is provided in ]

[165]186 Technical Support Document (TSD): Northern Wasatch Front (NWF), Utah: Failure to Attain the 2015 Ozone National Ambient Air Q uality Standard by the
Attainment Date; Reclassification and Disapproval of International Emission Demonstration, Docket Id. No. EPA-HQ-OAR-2021-0742-0043 (Jan. 2022) (179B NWF
TSD).
[166]187 SMOKE Technical Support Documentation for NWF SIP Attainment Demonstration; https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-
001603.pdf

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To determine the contribution of international anthropogenic source emissions to local ozone
concentrations, initial and boundary conditions (IC and BC) for the 4 km domain were also considered as
their own separate source groups. The contribution of international anthropogenic source emissions
was determined based on two CAMx simulations for the 12 km domain. These included a base (BASE)
simulation and a sensitivity (ZROW) simulation. The BASE case simulation included 2023 emissions from
all source emissions while the ZROW simulation included all 2023 emissions with the exception of non-
US anthropogenic emissions, leaving only US and global natural emissions. This ZROW simulation was
based on 2017 ZROW GEOS-Chem global chemistry model outputs, where all anthropogenic emissions
outside the US were set to zero188[167].
Source-apportioned boundary and initial conditions for the 4 km domain were then derived
using CAMx “saicbc” tool and model outputs from the base and ZROW 12 km simulations. Using IC and
BC extracted from model outputs from the base and ZROW 12 km simulations, the tool was used to
generate two source apportionment IC and BC groups for the 4 km domain, where one group represents
international anthropogenic emissions, and one represents global natural and US emissions within the
12 km CAMx domain that are transported into the 4 km domain from the lateral boundaries.

Figure [19]20: Map of source regions used in 2023 OSAT modeling for the 4 and 1.33 km domains. Each color represents a
different source region.

[167]188 https://views.cira.colostate.edu/docs/IWDW/Modeling/WRAP/2017/Ramboll_WESTAR_GEOS-Chem_Report_8Apr_2021.pdf

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Table [73]75: Emission source categories considered in 2023 OSAT modeling. *Only VOCs and NOx tracer species from US
Magnesium are tagged.
Source Group ID Source Group Description
1 Solvents: Consumer Products All personal care and household cleaning products
2 Solvents: Other Any non-personal care or household cleaning product
solvents: Surface coatings, dry cleaning, asphalt
paving, degreasing, etc.
3 Non-road: Lawn & Garden All lawn & garden equipment: 2- & 4-stroke gasoline-
powered mowers, trimmers, leaf blowers etc.
4 Non-road: Other Any non-lawn & garden non-road equipment:
construction equipment, aircraft ground support
equipment
5, 7 On-road: Light Duty Passenger vehicles
6, 8 On-road: Heavy Duty Commercial trucks, haul trucks, buses, motor homes
9 Rail
10 Biogenics
11 EGUs
12 Point Oil & Gas
13 Nonpoint Oil & Gas
14 Point: Other All other point sources not specifically tagged
15 Point: US Magnesium* all emissions associated with US Magnesium Rowley
Plant (point source ID = 10716)
16 Point: Mine Trucks Mobile Sources; Off-highway Vehicle Diesel;
Construction and Mining Equipment; Off-highway
Trucks
17 Wildfires, Prescribed Fires
18 Agricultural Fires
19 Lightning NOx
20 Airports
21 ERC Bank Emissions Reduction Credit bank
22 Fertilizer
23 Livestock
24 Nonpoint

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25 Area Fugitive Dust
International
Anthropogenic
Non-US anthropogenic emissions estimated based on
12 km base case and zero-out modeling simulations
that use GEOS-Chem global model outputs
Global Natural + Non-
Utah US
Anthropogenic
Global natural emissions plus any US anthropogenic
emissions that are transported into the 4km domain
(California anthropogenic, etc.). These were
estimated based on 12 km base case and zero-out
modeling simulations that use GEOS-Chem global
model outputs
Top Boundary
Conditions

Source group contributions to MDA8 ozone concentrations at each monitoring station and on
each day of the modeling episode were determined using modeled hourly contributions from each
source sector and region, where, for each group, contributions under “NOx-limited” and “VOC-limited”
chemical regimes were combined to obtain the net contribution from each group. For each day and
monitoring station, hourly contributions were processed to calculate 8-hour average source group
contributions at each individual monitoring site, where the contribution values were calculated using
model predictions for the grid cell that includes the monitoring station. For each day and monitoring
station, 8-hr average contributions were then summed to calculate total 8-hr average ozone
concentrations for each source group and region. Maximum daily 8-hr average ozone concentrations
and their contributions were then determined based on these total 8-hr values.
9.3 Ozone Source Apportionment Modeling Results
Source apportionment modeling results showed that non-Utah natural and non-Utah US
anthropogenic emissions contribute to most of the ozone measured at the Hawthorne monitoring
station, which corresponds to the monitor with the highest predicted FDV, accounting for about 67%
(39.07 ppb) of its modeled maximum daily 8-hour ozone concentrations on average during the modeling
episode (Figure [20] 21). Local anthropogenic and biogenic sources had smaller contributions,
accounting for nearly 14.5% (8.44 ppb) and 7.4% (4.28 ppb) of ozone at the same location, while
international anthropogenic emissions source contribution averaged 6.5% (3.74 ppb). The contributions
for background ozone (international anthropogenic emissions, global natural and US anthropogenic
emissions) are consistent with contributions reported for the Western US in other modeling
studies189[168],190[169],191[170]. Contributions from other sources, such as wildfires, prescribed (Rx) fires,
lightning NOx, were more minor (<= 4% at 2.3 ppb). Figures in this section represent a low bound of 8-
hour ozone source apportionment results and are subject to increase in future modeling.

[168]189 Denver Metro/North Front Range 2017 Ozone Source Apportionment Modeling. HYPERLINK "https://views.cira.colostate.edu/wiki/wiki/9132/denver-
metronorth-front-range-2017-ozone-source-apportionment-modeling"https://views.cira.colostate.edu/wiki/wiki/9132/denver-metronorth-front-range-2017-
ozone-source-apportionment-modeling
[169]190 2017 Denver Metro/North Front Range Moderate Area 8-Hour Ozone SIP. https://raqc.egnyte.com/dl/uJJfKleU67/FinalModerateOzoneSIP_2016-11-
29.pdf_
[170]191 Scientific assessment of background ozone over the U.S.: Implications for air quality management .
https://online.ucpress.edu/elementa/article/doi/10.1525/elementa.309/112835/Scientific -assessment-of-background-ozone-over-the

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Figure [20]21: Source contributions by region and emission sector to 8-hour ozone concentration (ppb) at the Hawthorne
monitoring station for each day of the modeling episode (left panel) and on average over all days of the modeling episode (right
panel). Results are based on 2023 OSAT model outputs for the 1.33 km modeling domain and spin-up days are excluded.
These source contributions displayed some differences across exceedance, top 10 exceedance
and non-exceedance days (Figure [20]21). Compared to contributions on non-exceedance days, the
contributions from local anthropogenic and biogenic source emissions are greater on exceedance
(modeled MDA8 ozone >= 60 ppb) and top 10 exceedance days, on average, consistent with
expectations [(Table 21)]Figure 22. Ozone exceedance days are characterized by an upper-level high
pressure system that brings warm temperatures, lack of frontal passage, low surface winds and
increased solar radiation; all of which are conducive to the build-up of ozone and its precursors. The
contribution of international anthropogenic emissions to average ozone also increased on exceedance
days compared to non-exceedance days, but the increase was not as significant as that determined for
local anthropogenic and biogenic source emissions. Their contribution estimate increased from 3.25 ppb
(6.2%) on non-exceedance days to 4.47 ppb (6.7%) on exceedance days. A similar increase is also noted
for background natural and US anthropogenic emissions. The upper-level ridge on exceedance days can
increase background concentrations within the ridge, where the complex topography of the region can
enhance vertical transport and recapture of ozone from aloft.192[171]

[171]192 Reddy, P. J., & Pfister, G. (2016). Meteorological factors contributing to the interannual variability of midsummer surface o zone in Colorado, Utah, and
other western U.S. states. Journal Of Geophysical Research-Atmospheres, 121, 2434-2456. doi:10.1002/2015JD023840.

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Figure [21]22: Source contributions by region and emission sector ozone concentration (ppb) at the Hawthorne monitoring
station for each day of the modeling episode (upper panel) and on average over all days of the modeling episode, exceedance
days, top 10 exceedance days and non-exceedance days (lower panel). Results are based on 2023 OSAT model outputs for the
1.33 km modeling domain and spin-up days are excluded.
9.4 Future Design Values after Removal of Contributions from International
Anthropogenic Emissions

Overall, the source apportionment modeling results show that background ozone emission
sources, contribute to the majority of the ozone measured along the Wasatch Front, accounting for about
66% of modeled ozone concentrations, on average on modeled top 10 exceedance days. This includes
59.3% (40.82 ppb) contribution from natural and US anthropogenic emissions outside Utah and 6.5% (4.5
ppb) contribution from international anthropogenic emission sources. Using the source contribution
estimate for international anthropogenic emissions, the projected FDV were adjusted to reflect what the
FDV would be but for the presence of international emissions. For each site, FDV were adjusted by
subtracting the OSAT source contribution estimate for international anthropogenic emissions (IAE) from
the FDV calculated in the attainment demonstration (section 8).
Average source contribution estimate for international anthropogenic emissions on top 10
exceedance days were used for this calculation. For cases in which the model simulation does not include
10 days with MDA8 ozone values >= 60 ppb at a site, all days with MDA8 O3 values >= 60 ppb are used in
the calculation. Given that the model does well at simulating background ozone (section 8.2[, Table 69]),
subtracting the OSAT source contribution estimate for international anthropogenic emissions from the
FDV calculated in the attainment demonstration is considered adequate. This approach is shown in
equation [3]6. Moreover, since the model tended to be biased low for local ozone production, this
approach is more adequate than a scaling technique where the FDV at each monitoring site is scaled by

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the relative modeled changes in ozone between a 2023 baseline and a 2023 sensitivity modeling scenario
that includes emissions from all sources except for international anthropogenic emissions.

Equation [3]6
𝑫𝑫𝑽𝒊, 𝒂𝒅𝒊=𝑫𝑫𝑽𝒊−𝑰𝑨𝑫𝒊,

where “i” corresponds to a given monitoring site.
Resulting adjusted FDV are shown in Table [74]76. Consistent with the truncation and rounding
procedures for the 8-hour ozone NAAQS, the projected DVs are truncated to integers in units of
ppb193[172]. All sites demonstrate attainment when the contribution of international anthropogenic
emission sources is subtracted from the FDV calculated in the attainment demonstration modeling.

Table [74]76: Future design values (FDV), source contribution estimates for international anthropogenic emissions (IAE) and
adjusted future design values (FDV adj) at monitoring locations within the northern Wasatch Front non -attainment area.
Site Site ID County FDV (ppb) IAE (ppb) FDV_adj
Bountiful 490110004 Davis 71 4.54 66
Hawthorne 490353006 Salt Lake 72 4.50 67
Herriman 490353013 Salt Lake 72 3.81 68
Erda 490450004 Tooele 70 4.06 65
Harrisville 490571003 Weber 70 3.12 66
9.5 Conclusion
In its document overviewing the disapproval of Utah’s retrospective 179B(b) demonstration,
EPA cited a lack of “sufficient technical information”194[173] to support the modeled conclusions including:
a lack of emission data, observations, and meteorological analyses. Further, EPA noted that the model
UDAQ relied on for its submission did not demonstrate adequate model performance to creditably
determine the influence of international contributions in the NAAs ability to attain the standard.195[174]
The 179B(a) demonstration provided as part of this SIP revision leverages the wealth of
information included within the SIP and in the technical supporting documentation. This includes
detailed information on the underlying emission inventories (section 3), modeled and observed
concentrations (section 8), and meteorological modeling (section 8).196[175] The improved modeling also
conforms with EPA’s modeling performance metrics (section 8). Thus, the analysis and conclusions
provided in this 179B(a) demonstration and SIP revision fulfill the technical deficiencies EPA noted in
Utah's retrospective submission, and conclusively identifies the role international emissions play in the
NWF NAA’s ability to attaining the standard by the attainment date.
Beyond the lack of technical information cited by EPA in its disapproval of Utah’s 179B(b)
demonstration, EPA noted that the state’s demonstration diverged from EPA’s interpretation of criteria

[172]193 40 CFR Part 50, Appendix P to Part 50 – Interpretation of the Primary and Secondary National Ambient Air Quality Standards for Ozone.
[173]194 179B NWF TSD at 2.2
[174]195 Id.
[175]196 Meteorological Modeling for Wasatch Front O3 SIP. Technical Support Documentation and Model Performance Evaluation.

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for a successful demonstration in several ways.197[176] EPA noted that the states did not demonstrate that
international transport is significantly different on ozone exceedance days compared to non-exceedance
days and that international contributions appear to contribute less than local ozone production.198[177]
As shown in Figure [22]23, the UDAQ has identified that international emissions contribute to
~6% of ozone in NWF NAA on non-exceedance days. That contribution increases to ~7% of the total
modeled ozone across all exceedance days. The observed increase during exceedance days relative to
non-exceedance days represents a significant additional contribution to the observed ozone
concentrations when considering that only 18.5% of the overall ozone contributions are attributed to in-
state anthropogenic emissions. Thus, the additional 1% observed international contributions on
exceedance days represents excess international contributions relative to modeled non-exceedance day
contributions.

Figure [22]23: International contributions at Hawthorne monitor site on exceedance and non-exceedance days.
As further demonstrated by Figure 22, international emissions represent a significant
contribution to the NAA relative to ozone attributable to anthropogenic emissions within the NAA, and
thus emissions which this SIP can regulate. For instance, on the top 10 exceedance day during the
modeling episode, anthropogenic emissions represent just 19.3% of modeled ozone, with emissions
from sources under federal jurisdiction accounting for 11.8% and emissions under state authority
accounting for the remaining 7.5%. However, contributions from international anthropogenic emissions
account for 6.5% of the modeled ozone concentrations.

[176]197 179B NWF TSD at 2-3.
[177]198 Id. at 3.

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The EPA further notes in its disapproval of Utah’s 179B(b) submission that the state failed to
adequately demonstrate that all “feasible” emission reduction strategies had been implemented.199[178]
As noted in the ozone implementation rules,200[179] emission reduction strategies implemented as part of
ozone SIPs are to be reasonably available (i.e., RACT or RACM), and thus feasible controls in the context
of ozone reductions strategies should be held to a comparable standard. While section 179B of the CAA
makes no specific mention of the requirement for implementation of feasible controls, sections 4 and 5
of this SIP revision clearly demonstrate that the state of Utah has implemented an exhaustive list of VOC
and NOx emission reduction strategies throughout the NAA as a result of past SIPs targeting wintertime
PM2.5, many of which go beyond what would be considered reasonably available. Beyond the controls
implemented to date, the UDAQ has identified additional emission reduction controls and strategies as
outlined in Sections 4, 5 and 7 of this SIP revision, some of which have been determined to be ”beyond-
RACT”. These emission reductions are planned to be implemented in the coming years and serve as
further evidence that the state has implemented feasible controls, and thus the contributions of
international emissions should be considered when determining attainment.
Lastly, in its disapproval of Utah’s 179B(b) demonstration EPA argued that the presence of a
nearby ozone NAA, the Southern Wasatch Front (SWF) (figure 1) which recently attained the standard
by the marginal attainment date, is evidence that the NWF NAA can attain the current standard despite
the presence of international emissions. However, in the same document, EPA demonstrates that the
SWF has an order of magnitude lower anthropogenic NOx emissions and almost a third of the
anthropogenic VOC emissions when compared to the NWF201[180]. To this point, the SWF has
approximately 1.2 million fewer residents than the NWF and a substantially different industrial sector.
While the SWF did attain the 2015 ozone NAAQS by the marginal attainment date of August 3, 2021, it
did so by just 1.0 ppb, and has subsequently exceeded this standard. The fact that a bordering NAA, with
fewer residents, fewer emissions, and a substantially different industrial make-up, is marginally attaining
the standard further demonstrates why it is critical that the presence of international emissions be
appropriately acknowledged as regulatorily significant. Unless it is the intent of the EPA to suggest that
the NWF NAA must reduce its NOx and VOC emissions to levels similar to that of the SWF, which is
impossible given the lack of reasonably available control options available to the state as demonstrated
in sections 4 and 5 of this SIP revision, the state does not see how the attainment status of the SWF is
relevant. In fact, comparisons between two substantially different NAAs, both of which are facing the
Intermountain West’s regionally specific challenges in addressing ozone, only further supports that
international emissions are regulatorily significant to the region. Thus, section 179B of the CAA is an
appropriate mechanism to provide regulatory flexibility to NAAs within this unique geographic region.
As discussed in the introduction of this section, an approved 179B(a) demonstration would not
prevent the NWF NAA from being reclassified to a more stringent nonattainment status if the area fails
to attain the standard by the attainment date based on ambient monitoring data. Instead, this
demonstration serves as further evidence that the modeling attainment demonstration and WOE
analysis provided in section 8.3 of this SIP revision adequately demonstrates the NWF NAA is projected
to attain the standard by the attainment date, but for the presence of international emissions.

[178]199 Id. at 3.
[179]200 83 Fed. Reg. 62,998.
[180]201 179B NWF TSD at 14, Tables 2 and 3.4

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Chapter 10 - Transportation Conformity and Motor Vehicle Emission
Budget
10.1 Introduction
Motor Vehicle Emission Budgets (MVEB) for NOx and VOCs were submitted to the EPA in 1997 as
part of Utah’s maintenance plan for the 1979 1-hour ozone standard. EPA approved these MVEB for
transportation conformity purposes when it finalized the approval of that maintenance plan,202[181]
further reaffirming this budget in subsequent rulemaking.203[182] As a result, the local MPO Wasatch
Front Regional Council (WFRC) has been using these budgets for subsequent transportation conformity
determinations within the ozone NAA. Following this same approach, the UDAQ has developed an
updated MVEB for the NWF NAA to be used in future transportation conformity determinations in
relation to the 2015 NAAQS standard for ozone. As required by Section 176(c) of the CAA, this MVEB is
based on the best available data for emissions, population, and travel estimates available during the
development of this SIP.
10.2 Transportation Conformity
Transportation conformity is a requirement under CAA Section 176(c).204[183] This requirement
ensures that any federally funded or approved highway or transportation activity conforms to the
relevant promogulated air quality SIPs, in a way that planned transportation activities do not interfere
with a SIPs success in reducing the severity or number of exceedances of a NAAQS. The federal level
transportation conformity rules establish the criteria and procedures for determining if a metropolitan
transportation plan, TIP, or federally supported highway and transportation projects conform to the
SIP.205[184] State level transportation conformity requirements are codified in Utah’s SIP Section XII.206 [185]
Transportation conformity requirements apply to any designated NAA or maintenance area for a
primary NAAQS and must be included in any SIP submitted for these areas.
The metropolitan planning responsibilities for the area encompassed by the NWF NAA are
covered by a single MPO—Wasatch Front Regional Council (WFRC). WFRC serves as the MPO for Box
Elder, Davis, Salt Lake, Tooele, and Weber counties.
Upon a finding of adequacy or approval by the EPA, the impacted MPO in the NAA will use these
budgets to demonstrate that estimated emissions resulting from the implementation of approved
transportation plans and TIPs are less than or equal to the budgets included in this SIP revision.
10.3 – Consultation
The ICT is an air quality workgroup in Utah that makes technical and policy recommendations
regarding transportation conformity issues related to the SIP development and transportation planning
process. Section XII of the Utah SIP established the ICT workgroup and defines the roles and

[181]202 62 Fed. Reg. 38,213.
[182]203 Approval, Disapproval and Promulgation of Air Quality Implementation Plan; Utah; Maintenance Plan for the 1-Hour Ozone Standard for Salt Lake and
Davis Counties, 77 Fed. Reg. 35,873 (June 15, 2012).
[183]204 42 U.S.C. § 7506(c).
[184]205 40 CFR Part 51; 40 CFR Part 93.
[185]206 Utah State Implementation Plan; Section XII, Transportation Conformity Consultation. Adopted by the Utah Air Quality Board Ma y 2, 2007

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responsibilities of the participating agencies. Members of the ICT workgroup collaborated on a regular
basis during the development of the ozone SIP. They also meet on a regular basis regarding
transportation conformity and air quality issues.

The ICT workgroup is comprised of management and technical staff members from the affected
agencies associated directly with transportation conformity including the following agencies:
• UDAQ
• Cache MPO
• Mountainland Association of Governments
• Wasatch Front Regional Council
• Utah Department of Transportation (UDOT)
• Utah Local Public Transit Agencies
• FHWA
• Federal Transit Administration (FTA)
• EPA

The regional emissions analysis is the primary component of transportation conformity and is
administered by the lead transportation agency located in the EPA designated air quality NAA. The
responsible transportation planning organization for the Salt Lake City, UT NAA is the WFRC. During the
SIP development process, the WFRC coordinated with the ICT workgroup and developed ozone SIP
motor vehicle emissions inventories using the latest planning assumptions and tools for traffic analysis
and the EPA-approved Motor Vehicle Emission Simulator (MOVES2014a) emissions model. The WFRC
and the ICT worked cooperatively to develop local MOVES2014a modeling data inputs using EPA
recommended methods where applicable.
10.4 Motor Vehicle Emission Budgets (MVEB)
MVEBs are defined as the “portion of the total allowable emissions defined in the submitted or
approved control strategy implementation plan revision or maintenance plan for a certain date for the
purpose of meeting reasonable further progress milestones or demonstrating attainment or
maintenance of the NAAQS, for any criteria pollutant or its precursors, allocated to highway and transit
vehicle use and emissions.”207[186]
Thus, a MVEB refers to the maximum allowable emissions originating from the on-road mobile
sector for each applicable regulated pollutant (i.e., NOx and VOCs) as defined in the SIP and required by
the CAA. The MVEB must be used in all future transportation conformity analysis and areas must
demonstrate that the estimated emissions from transportation plans, programs, and projects do not
exceed the MVEB. MVEBs were developed in collaboration with the MPO WFRC. Details regarding the
development of the budget can be found in the accompanying Technical Supporting Document
(TSD).208[187]

[186]207 40 CFR § 93.101.
[187]208 TECHNICAL SUPPORT DOCUMENT FOR ON-ROAD MOBILE SOURCES: MOTOR VEHICLE EMISSIONS BUDGET DERIVIATION FOR THE NORTHERN WASATCH
FRONT, UT NONATTAINMENT OZONE AREA: https://documents.deq.utah.gov/air-quality/planning/DAQ-2023-001700.pdf

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For the purpose of this SIP revision, MVEBs for precursor emissions of VOC and NOx are
established for the attainment year of 2023, and are based on the projected on-road mobile inventory
for the same year as described in section 3.2.6. This MVEB represents a single NAA-wide MVEB to be
used in transportation conformity purposes.
Within the NWF NAA, both Tooele and Weber counties are not entirely contained within the
NAA boundary. Thus, portions of the counties are located outside of the boundary, while most of the
population of each county resides within the boundary. To account for the proportion of on-road mobile
emissions attributable to the NAA, and thus to be included in a MVEB, 2020 census data was used to
determine the percentage of on-road vehicle activity relative to census tracts located within the NAA,
and emissions were revised accordingly. For Salt Lake and Davis counties, which are entirely located
within the NAA, no such adjustments were made.
10.5 Emission Budgets for the Northern Wasatch Front NAA
For the purposes of transportation conformity in the NWF NAA, Table [75]77 includes a MVEB in
tpd for daily summertime weekday emissions of both VOCs and NOx.

Table [75]77: NWF Ozone 2023 NAA MVEB
NWF, UT Ozone 2023 NAA MVEB
Year County NOx (tpd) VOC** (tpd)
2023* Davis (NA) 7.42 2.78
2023* Salt Lake (NA) 20.98 8.53
2023* Tooele (NA) 3.49 0.81
2023* Weber (NA) 5.69 2.06
Total 37.58 14.18
NA = NAA County Portion
* Gasoline 10 PPM Sulfur
**VOC = VOC does not include Refueling Displacement and Spillage

It is important to note that the MVEBs presented in Table [75]77 are somewhat different from
the on-road mobile emission inventory presented in Table 8. The emissions established for this MVEB
were calculated using MOVES3 to reflect an average summer weekday. The totals presented in the
summary emissions inventory in section 3, however, represent a summer average-episode-day. Thus,
the temporal averaging used to generate these two different products results in slightly different values.
10.6 Implementation of MVEB in Transportation Conformity Determinations
The MVEB for the NWF NAA, once determined adequate or approved by the EPA, will be used
for purposes of transportation conformity determinations of Regional Transportation Plans (RTPs) and
TIPs for the respective MPOs and planning areas. Once the included MVEB is in effect, the local MPO
must make a new determination of conformity for their respective RTP and TIP within two years of EPA’s
finding of adequacy or SIP approval.209 [188] Throughout the process of determining conformity with the

[188]209 40 CFR § 93.104(e).

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MVEB included in this SIP revision, the impacted MPO shall consult with federal, state, and local air
agencies through the normal interagency consultation process established in Section XII of the Utah SIP.

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Chapter 11 - Contingency Measures
11.1 Overview
Section 172(c)(9) of the CAA requires SIPs to include provisions for specific emission reduction
measures to be undertaken if the area fails to demonstrate RFP requirements or attain the NAAQS by
the attainment date. These provisions are known as contingency measures. These contingency
measures shall take effect “without further action by the State, or the [EPA] Administrator”, thus no
further rulemaking activities by the State or EPA would be needed to implement them if the area fails to
attain the standard by the attainment date or if a SIP revision fails to demonstrate RFP.210[189]
Contingency measures should consist of other available control measures or emission reduction
strategies beyond those reasonably required (i.e., RACT or RACM) to expeditiously attain the
NAAQS.211[190]
The attainment date for the 2015 8-hour ozone NAAQS moderate SIP for the NWF NAA is August
3, 2024. Thus, if triggered, contingency measures must result in additional emission reductions after that
date, or upon a disapproval of the RFP plan included in this SIP revision by the EPA. Contingency
measures shall provide demonstratable emission reductions of one year’s worth of emission reductions,
or approximately 3% of the 2017 base year emission inventory.212[191] Unlike the RFP requirements of a
moderate SIP, emission reductions associated with contingency measures can consist entirely, or in part,
of NOx emission reduction strategies.213[192]
11.2 Contingency Measures
11.2.1 NOx Emission Reductions from Boilers
The UDAQ has proposed R307-315; NOx Emission Controls for Natural Gas-Fired Boilers 2.0-5.0
MMBtu, and R307-316; NOx Emission Controls for Natural Gas-Fired Boilers greater than 5.0 MMBtu,
both of which were described in section 5.3, Table 58. These rules were adopted by the Utah Air Quality
Board in May of 2023, with an implementation beginning in May of 2024. These rules require new and
modified industrial and commercial boilers installed in the NWF NAA to comply with an emission
threshold of 9 parts per million by volume (ppmv). The NOx emission reductions from these combined
rules are anticipated to result in a total reduction of 7.3 tpd, or 2,689 tpy once the full emission
potential of the rules are realized. While these rules do not require retrofits or replacements of existing
equipment, when accounting for the useful life span of this equipment it is anticipated that the full
emission potential of these rules will be realized in 10 – 20 years. Thus, it is expected that these two
rules combined will result in ~0.36 tpd of emission reductions per year, compounding over time to the
full 7.3 tpd. Given the implementation timeline of these control strategies, one year of emission
reductions (0.36 tpd) should be creditable towards contingency measure requirements.

[189]210 State Implementation Plans; General Preamble for the Implementation of Title I of the Clean Air Act Amendments of 1990, 57 Fed. Reg. 13,498, 13,512
(April 16, 1992).
[190]211 Id. 57 Fed. Reg. at 13,543.
[191]212 83 Fed. Reg. 62,998; 80 Fed. Reg. 12,285.
[192]213 83 Fed. Reg. 62,998.

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11.2.2 US Magnesium
As part of this SIP revision, and as overviewed in section 4.15, the UDAQ is requiring US
Magnesium to install a steam stripper and thermal oxidizer to reduce VOC emissions from its
wastewater and deboronated pond water systems.214[193] The installation of these controls will reduce
0.44 tpd (161.7 tpy) of VOC emissions from the airshed. It is anticipated that these controls will be
installed by October of 2024. US Magnesium is located outside of the existing NAA boundary and thus
emission reductions are not creditable towards RFP, emission reductions implemented in areas outside
of a NAA may count towards contingency measures as long as they improve air quality in the subject
NAA.215[194]
11.2.3 NAA NOx Emission Reductions
As described in detail in section 7.4, the NWF NAA has experienced significant emission
reduction of anthropogenic NOx. From the baseline year of 2017 to the attainment year for this SIP
revision of 2023, NOx emission decreased from 108.3 tpd down to 87.0 tpd. Thus, the area experienced a
21.3 tpd reduction in NOx emissions, representing a 19.6% decrease. These emission reductions are
largely the result of the introduction of more stringent vehicle emission reduction tiers and the
introduction of cleaner burning Tier 3 fuels into the NWF NAA. Thus, as the market penetration of Tier 3
fuels continues throughout the NAA as the local refineries finish the transition to refining fuels at these
standards, and older vehicles are replaced with newer cleaner vehicles, the emission reductions seen in
this sector are expected to continue without further action required.
11.3 Contingency Measures Emission Reduction Demonstration
Currently, no rulemaking exists that precludes a state from implementing a contingency
measure before they are triggered, but emission reductions credited towards contingency measures
may not be accounted for as part of the RFP demonstration. The emission reductions described in
sections 11.2.1 and 11.2.2 will be in effect prior to the attainment date but are not counted towards
RFP. The emission reductions described section 11.2.3 are already in place and do not count towards
RFP or are being used as a control measure for this SIP revision. Table [76]78 demonstrates how the
area has met the contingency measure requirement of reductions of 3% of baseline emissions.

Table [76]78: Percent Emission Reductions Based on 2017 Base Year Inventory
NOx Emissions (tpd) VOC Emissions (tpd)
2017 Baseline Inventory 108.3 93.7
3% Baseline Inventory 3.2 2.8
Emission Reductions for Contingency
Measures (Percent of 2017 Inventory)
21.66
(20%)
0.44
(0.47%)
Meets Contingency Measure
Requirements?
Yes --

[193]214 Utah State Implementation Plan; Section IX, Part H.32.k
[194]215 See e.g., Louisiana Env't Action Network v. U.S. E.P.A., 382 F.3d 575, 585 (5th Cir. 2004).

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Chapter 12 - Environmental Justice & Title VI Considerations
12.1 Environmental Justice
EPA defines Environmental Justice (EJ)
as the fair treatment and meaningful
involvement of all people regardless of race,
color, national origin, or income, with respect
to development, implementation, and
enforcement of environmental laws,
regulations, and policies.216[195] Fair treatment
ensures no group of people are
disproportionately burdened by environmental
harms or risks, including those resulting from
industrial, governmental, and commercial
operations, programs, or policies. Meaningful
involvement ensures that populations
potentially affected by an action have an
opportunity to participate in decisions
impacting their environment and health.
Meaningful involvement also includes the
stipulations that the public’s contributions can
influence a regulatory agency’s decision, the
concerns of the public will be considered in the
decision-making process, and the rule-writers
and decision-makers will seek out and facilitate the involvements of these potentially-affected
populations. Executive Order (E.O.) 12898: Environmental Justice,217[196] directs federal agencies to
incorporate environmental justice initiatives into their missions. E.O. 14008 issued in 2021218[197] further
reiterated a national focus on EJ. As a result, EPA has encouraged states to consider EJ in their SIP
development process as their resulting actions may have impacts on disproportionately affected areas.
EPA has also issued guidance on incorporating EJ consideration during the development of regulatory
actions.219[198]
12.2 Title VI of the Civil Rights Act
Title VI of the Civil Rights Act is a federal law that prohibits recipients of federal financial
assistance (e.g., states, universities, and local governments) from discriminating based on race, color, or
national origin in any program or activity.220[199] This prohibition against discrimination under Title VI has
been a statutory mandate since 1964 and EPA has had Title VI regulations since 1973. Title VI allows

[195]216 https://www.epa.gov/environmentaljustice
[196]217 Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations, 59 Fed. Reg. 7,629 (Feb. 11, 1994).
[197]218Tackling the Climate Crisis at Home and Abroad, 86 Fed. Reg. 7,619 (Jan. 27, 2021).
[198]219 Guidance on Considering Environmental Justice During the Development of Regulatory Actions (May 2015), available at
https://www.epa.gov/environmentaljustice/guidance-considering-environmental-justice-during-development-action.
[199]220 Title VI, 42 U.S.C § 2000d et seq.
Figure [23]24: EJ Indexes >80th percentile in Each NWF NAA Census Block

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persons to file administrative complaints with federal departments and agencies alleging discrimination
based on race, color, or national origin and EPA has a responsibility to ensure its funds are not being
used to subsidize discrimination. Should a complaint be filed, EPA’s Office of Civil Rights is responsible
for the Agency’s administration of Title VI, including investigation of such complaints. In accordance with
Title VI, federal agencies shall ensure that all programs and activities receiving federal financial
assistance that affect human health or the environment do not discriminate based on race, color, or
national origin. The NWF NAA SIP revision falls under this category of programs and has potential
impacts on such areas.
12.3 Screening-Level Analysis
Using Utah’s Environmental Interactive Map,221[200] UDAQ conducted an analysis of the EJ indices
surrounding the NWF NAA. UDAQ reviewed all pollution and sources as well as socioeconomic indicators
(a total of 20 indices) as percentiles calculated by comparing data from census blocks within the State of
Utah. UDAQ notes that this SIP revision does not have the authority to control the following indexes
included in this analysis: lead paint, superfund sites, wastewater discharge, RMP facilities, hazardous
waste, or underground storage tanks. Figure [23]24 shows the count of EJ indexes above the 80th
percentile in each of the census blocks within the NWF NAA. Table [77]79 shows the number of census
blocks in the NFW NAA at the 80th percentile and above for each EJ index.
Table [77]79: Environmental Justice Indexes Over the 80th Percentile in the NWF NAA
EJ Index Number of Census
Blocks >80th Percentile
Superfund Proximity 400
PM2.5 387
Ozone 364
Hazardous Waste Proximity 318
Air Toxics Respiratory Health Index 306
People of Color 294
Diesel PM 291
Air Toxics Cancer Risk 282
Underground Storage Tanks 267
Traffic Proximity 262
RMP Facility Proximity 258
Demographic Index 250
Less than High School Education 244
Lead Paint 236
Limited English Speaking 215
Low Income 181
Wastewater Discharge 153
Unemployment Rate 136
Under Age 5 113
Over Age 64 61

[200]221 https://enviro.deq.utah.gov/

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12.3.1 EJ Screening Findings
Based on Figure [23]24, the areas within the NWF NAA with the highest concentrations of indexes
above the 80th percentile include Ogden, Salt Lake City, West Valley City, and West Jordan. There is a
total of 498 census blocks within the NWF NAA.
Table [77]78 shows a high number of census blocks at the 80th percentile or greater for all EJ indexes,
with the most prevalent indexes in the NAA being:
• Superfund Proximity
• PM2.5
• Ozone
• Hazardous Waste Proximity
• Air Toxics Respiratory Health Index
• People of Color
• Diesel PM
• Air Toxics Cancer Risk
• Underground Storage Tanks
• Traffic Proximity
12.4 Identified Stakeholders
As a result of this EJ analysis, UDAQ has identified the general public and public health
departments within the Ogden, Salt Lake City, West Valley City, and West Jordan areas as populations
potentially affected by the decisions made in this SIP. UDAQ identified these stakeholders as entities and
groups requiring additional facilitation and involvement in the SIP development process.
12.5 Stakeholder Outreach, Meaningful Involvement, and Information Distribution
UDAQ made it a priority to ensure that the identified stakeholders would have ample and equal
opportunity within the division’s ability to participate in this SIP process through the measures described
in section 12.5.1 to 12.5.5.
12.5.1 Public Informational Meetings
UDAQ hosted two virtual public meetings on the subject of “Finding Ozone Emissions Reduction
Ideas.” The first meeting took place on Wednesday, March 23, 2022, from 6 to 7 PM MST, and the
second meeting took place on Saturday, May 3, 2022, also from 6 to 7 PM MST. These times were
selected to maximize attendance from households with traditional working hours. Handouts for this
meeting were issued via an interactive webpage222[201] and potential attendees were invited to submit
comments through a public Google Form to be addressed at each of the meetings. 67 individuals
attended the first meeting. 45 individuals attended the second meeting. Recordings of each of these
meetings are publicly available on YouTube.223 [202]
UDAQ also presented SIP-related updates to the State of Utah Governance Committee, a joint
coordination effort by the Utah Department of Health and local health departments. These
presentations took place on September 27, 2022, and on January 24, 2023, to inform the committee of
the progress UDAQ has made in the SIP development process and emission reduction strategies
employed.

[201]222 https://deq.utah.gov/air-quality/northern-wasatch-front-ozone-emissions-inventory
[202]223 https://www.youtube.com/watch?v=ip5D7nRaLTI & https://www.youtube.com/watch?v=b0fHNSFczvE

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12.5.2 Environmental Advocate and Industrial Stakeholder Meetings
UDAQ holds regular environmental advocate meetings, industrial stakeholder meetings, and
academic stakeholder meetings where UDAQ updated these groups on the development of this SIP and
online postings of the SIP-related documents. Members of all groups were provided equal opportunities
to ask questions and were encouraged to comment during these meetings as well as follow up
afterward.
12.5.3 Public Commenting Period
Upon the approval of the Air Quality Board on April 5, 2023, this SIP and all relating documents
were made available for public comment from June 1 to July 17, 2023. Public notices for the
commenting period were issued on the UDAQ webpage, via electronic mail, and in the Utah State
Bulletin. Commenters included:
• 49 private citizens;
• US EPA Region 8;
• Breathe Utah;
• HEAL Utah;
• Utah Petroleum Association and Utah Mining Association;
• Chevron Products Company;
• Marathon Tesoro Refining & Marketing Company LLC;
• Rio Tinto Kennecott;
• Western Resource Advocates; and
• Utah Manufacturers Association

12.5.4 Public Hearing
As part of the public commenting period, a public hearing was conducted at the State of Utah
Multi-Agency State Office Building on July 12, 2023 at 12:00 PM. The public hearing information was
advertised in the Utah State Bulletin, and the UDAQ webpage 41 days prior to the event. Attendance to
this hearing was available both in-person as well as virtually. Commenters included:
• Nick Schou of Western Resource Advocates;
• Alex Veilleux of Heal Utah; and
• Gregor Green a private citizen

All comments made by groups and individuals listed in Sections 12.5.3 and 12.5.4 were duly
considered in the decision-making process of this SIP. These comments are summarized and responded
to in APPENDIX B with original versions of each group or individual’s comments available at
https://deq.utah.gov/air-quality/northern-wasatch-front-moderate-ozone-sip-technical-support-
documentation.

12.5.5 Information Dissemination
All materials related to this SIP have been posted on UDAQ’s public platforms as the division has
received and processed them throughout the development of this SIP. UDAQ uses all resources at its
disposal to disseminate information to its stakeholders including:

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• UDAQ webpage 224[203]
• State Bulletin
• Ozone SIP webpage 225[204]
• Stakeholder meetings
• Local newspapers in identified stakeholder
communities.

[203]224 https://deq.utah.gov/division-air-quality
[204]225 https://deq.utah.gov/air-quality/northern-wasatch-front-moderate-ozone-sip-technical-support-documentation