DAQ-2024-011601

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UTAH
State Implementation Plan

Control Measures for Area and Point Sources, Fine Particulate Matter,
PM2.5 SIP for the Logan, UT-ID Nonattainment Area

Section IX. Part A.23

Adopted by the Utah Air Quality Board
December 3, 2014
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Acronyms ……………………………………...................................................................................... 3
Table of Contents ................................................................................................................ 5
List of Figures .......................................................................................................................7
List of Tables ........................................................................................................................ 8

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Acronyms

BACT Best Available Control Technology
CAA Clean Air Act
CFR Code of Federal Regulations
CMAQ Community Multiscale air Quality
CTG Control Techniques Guideline documents
DAQ Utah Division of Air Quality (also UDAQ)
EPA Environmental Protection Agency
FRM Federal Reference Method
MACT Maximum Available Control Technology
MATS Model Attainment Test Software
MPO Metropolitan Planning Organization
μg/m3 Micrograms Per Cubic Meter
Micron One Millionth of a Meter
NAAQS National Ambient Air Quality Standards
NESHAP National Emissions Standards for Hazardous Air Pollutants
NH3 Ammonia
NOx Nitrogen Oxides
NSPS New Source Performance Standard
NSR New Source Review
PM Particulate Matter
PM10 Particulate Matter Smaller Than 10 Microns in Diameter
PM2.5 Particulate Matter Smaller Than 2.5 Microns in Diameter
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RACM Reasonably Available Control Measures
RACT Reasonably Available Control Technology
RFP Reasonable Further Progress
SIP State Implementation Plan
SMOKE Sparse Matrix Operator Kernal Emissions
SO2 Sulfur Dioxide
SOx Sulfur Oxides
TSD Technical Support Document
VOC Volatile Organic Compounds
UAC Utah Administrative Code
WRF Weather Research and Forecasting
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TABLE OF CONTENTS

Chapter 1 – INTRODUCTION AND BACKGROUND .................................................................. 10
1.1 Fine Particulate Matter .................................................................................................................... 10
1.2 Health and Welfare Impacts of PM2.5 .............................................................................................. 10
1.3 Fine Particulate Matter in Utah ....................................................................................................... 11
1.4 2006, NAAQS for PM2.5 .................................................................................................................... 11
1.5 PM2.5 Nonattainment Areas in Utah ................................................................................................ 11
1.6 PM2.5 Precursors .............................................................................................................................. 13
Chapter 2 – REQUIREMENTS FOR 2006, PM2.5 PLAN REVISIONS ............................................ 15
2.1 Requirements for Nonattainment SIPs ............................................................................................ 15
2.2 PM2.5 SIP Guidance ........................................................................................................................... 16
2.3 Summary of this SIP Proposal ........................................................................................................... 16
Chapter 3 – Ambient Air Quality Data .................................................................................. 17
3.1 Measuring Fine Particle Pollution in the Atmosphere ..................................................................... 17
3.2 Utah’s Air Monitoring Network ........................................................................................................ 17
3.3 Annual PM2.5 – Mean Concentrations .............................................................................................. 18
3.4 Daily PM2.5 – Averages of 98th Percentiles and Design Values ...................................................... 19
3.5 Composition of Fine Particle Pollution – Speciated Monitoring Data .............................................. 20
3.6 PM2.5 Saturation Studies ................................................................................................................... 23
3.7 PCAP Study ....................................................................................................................................... 23
3.8 Ammonia (NH3) Studies .................................................................................................................... 24
Chapter 4 – EMISSION INVENTORY DATA ............................................................................. 25
4.1 Introduction ...................................................................................................................................... 25
4.2 The 2008 Emissions Inventory .......................................................................................................... 26
4.3 Characterization of Utah’s Airsheds ................................................................................................. 26
Chapter 5 – ATTAINMENT DEMONSTRATION ....................................................................... 29
5.1 Introduction ..................................................................................................................................... 29
5.2 Photochemical Modeling ................................................................................................................. 29
5.3 Domain/Grid Resolution .................................................................................................................. 29
5.4 Episode Selection ............................................................................................................................. 30
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5.5 Meteorological Data ........................................................................................................................ 33
5.6 Photochemical Model Performance Evaluation .............................................................................. 34
5.7 Summary of Model Performance .................................................................................................... 41
5.8 Modeled Attainment Test ............................................................................................................... 42
5.9 Air Quality as of the Attainment Date ............................................................................................. 43
Chapter 6 – CONTROL MEASURES ........................................................................................ 44
6.1 Introduction ..................................................................................................................................... 44
6.2 Utah Stakeholder Workgroup Efforts .............................................................................................. 44
6.3 Identification of Measures .............................................................................................................. 45
6.4 Existing Control Measures ............................................................................................................... 46
6.5 SIP Controls ...................................................................................................................................... 52
6.6 Reasonably Available Control Measures (RACM/RACT) .................................................................. 53
Chapter 7 – TRANSPORTATION CONFORMITY ...................................................................... 60
7.1 Introduction ...................................................................................................................................... 60
7.2 Consultation ..................................................................................................................................... 60
7.3 Regional Emission Analysis .............................................................................................................. 61
7.4 Transportation Conformity PM2.5 Components ............................................................................... 62
7.5 Interim PM2.5 Conformity Test ......................................................................................................... 62
7.6 Transportation Conformity PM2.5 Budgets ...................................................................................... 63
Chapter 8 – REASONABLE FURTHER PROGRESS .................................................................... 64
8.1 Introduction ..................................................................................................................................... 64
8.2 Moderate Area Planning Requirements .......................................................................................... 64
8.3 RFP for the Logan, UT-ID Nonattainment Area ............................................................................... 65
8.4 Milestones for the Logan, UT-ID Nonattainment Area ................................................................... 67
Chapter 9 – CONTINGENCY MEASURES ................................................................................. 68
9.1 Background ...................................................................................................................................... 68
9.2 Contingency Measures and Implementation Schedules for the Nonattainment Area ................... 68
9.3 Conclusions ...................................................................................................................................... 69

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List of Figures

Figure 1.1, Nonattainment Areas for the 2006, PM2.5 NAAQS ................................................................... 12

Figure 3.1, Utah’s PM2.5 Air Monitoring Network ...................................................................................... 18

Figure 3.2, Composite Wintertime PM2.5 Speciation Profiles ..................................................................... 22

Figure 5.1: Northern Utah photochemical modeling domain. ................................................................... 30

Figure 5.2: Hourly PM2.5 concentrations for January 11-20, 2007 ............................................................ 31

Figure 5.3: Hourly PM2.5 concentrations for February 14-19, 2008 ........................................................... 32

Figure 5.4: 24-hour average PM2.5 concentrations for December-January, 2009-10. ............................... 33

Figure 5.5: UDAQ monitoring network. ..................................................................................................... 34

Figure 5.6: Spatial plot of CMAQ modeled 24-hr PM2.5 (µg/m3) for 2010 Jan. 03..................................... 35

Figure 5.7: 24-hr PM2.5 time series (Hawthorne). Observed 24-hr PM2.5 (blue trace) and CMAQ
modeled 24-hr PM2.5 (red trace). ............................................................................................................. 36

Figure 5.8: 24-hr PM2.5 time series (Ogden). Observed 24-hr PM2.5 (blue trace) and CMAQ modeled 24-
hr PM2.5 (red trace). .................................................................................................................................... 37
.................................................................................................................................................................... 37

Figure 5.9: 24-hr PM2.5 time series (Lindon). Observed 24-hr PM2.5 (blue trace) and CMAQ modeled 24-
hr PM2.5 (red trace). .................................................................................................................................... 37

Figure 5.10: 24-hr PM2.5 time series (Logan). Observed 24-hr PM2.5 (blue trace) and CMAQ modeled 24-
hr PM2.5 (red trace). .................................................................................................................................... 38

Figure 5.11: An example of the Salt Lake Valley at the end of a high PM2.5 episode. The lowest
elevations of the Salt Lake Valley are still experiencing an inversion and elevated PM2.5 concentrations
while the PM2.5 has been ‘cleared out’ throughout the rest of the valley. These ‘end of episode’ clear
out periods are difficult to replicate in the photochemical model. ........................................................... 38

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Figure 5.12: The composition of observed and model simulated average 24-hr PM2.5 speciation
averaged over days when an observed and modeled day had 24-hr concentrations > 35 µg/m3 at the
Hawthorne STN site. ................................................................................................................................... 39

Figure 5.13: The composition of observed and model simulated average 24-hr PM2.5 speciation averaged
over days when an observed and modeled day had 24-hr concentrations > 35 µg/m3 at the Bountiful STN
site. ............................................................................................................................................................. 40

Figure 5.14: The composition of observed and model simulated average 24-hr PM2.5 speciation averaged
over days when an observed and modeled day had 24-hr concentrations > 35 µg/m3 at the Lindon STN
site. ............................................................................................................................................................. 40

Figure 5.15: The composition of model simulated average 24-hr PM2.5 speciation averaged over days
when a modeled day had 24-hr concentrations > 35 µg/m3 at the Logan monitoring site. No observed
speciation data is available for Logan. ....................................................................................................... 41

Figure 5.16, Model Results for the Logan, UT-ID Nonattainment Area ..................................................... 42

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List of Tables

Table 3.1, PM2.5 Annual Mean Concentrations .......................................................................................... 19

Table 3.2, 24-hour PM2.5 Monitored Design Values ................................................................................... 20

Table 4.1, Emissions Summary for 2010 (SMOKE). Emissions are presented in tons per average winter
day. ............................................................................................................................................................. 27

Table 4.2, Emissions Summaries for the Logan, UT-ID Nonattainment Area; Baseline and Attainment Year
(SMOKE). Emissions are presented in tons per average winter day. ........................................................ 28

Table 5.1, Modeled Concentrations (µg/m3) for the Salt Lake City, UT Nonattainment Area ................... 43

Table 6.1, Tier 1 Emission Standards .......................................................................................................... 48

Table 6.2, Tier 2 Emission Standards .......................................................................................................... 50

Table 6.3 Area Source Strategy Screening.................................................................................................. 55

Table 6.4, Emissions Reductions from Area Source SIP Controls ............................................................... 58

Table 7.1, Emissions Budgets for Transportation Conformity Purposes (EPA MOVES 2010a). Note: VOC
emissions do not include refueling spillage and displacement vapor loss. Budgets are rounded to the
nearest hundredth ton. .............................................................................................................................. 63

Table 8.1, Reasonable Further Progress in the Logan, UT-ID nonattainment area ................................... 66

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Chapter 1 – INTRODUCTION AND BACKGROUND

1.1 Fine Particulate Matter
According to EPA’s website, particulate matter, or PM, is a complex mixture of extremely small particles
and liquid droplets. Particulate matter is made up of a number of components, including acids (such as
nitrates and sulfates), organic chemicals, metals, and soil or dust particles.
The size of particles is directly linked to their potential for causing health problems. EPA is concerned
about particles that are 10 micrometers in diameter or smaller because those are the particles that
generally pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect
the heart and lungs and cause serious health effects. Other negative effects are reduced visibility and
accelerated deterioration of buildings.
EPA groups particle pollution into two categories:
 "Inhalable coarse particles," such as those found near roadways and dusty industries, are larger
than 2.5 micrometers and smaller than 10 micrometers in diameter. Utah has previously addressed
inhalable coarse particles as part of its PM10 SIPs for Salt Lake and Utah Counties, but this fraction is
not measured as PM2.5 and will not be a subject for this nonattainment SIP.

 "Fine particles," such as those found in smoke and haze, are 2.5 micrometers in diameter and
smaller and thus denoted as PM2.5. These particles can be directly emitted from sources such as
forest fires, or they can form when gases emitted from power plants, industries and automobiles
react in the air.
PM concentration is reported in micrograms per cubic meter or µg/m3. The particulate is collected on a
filter and weighed. This weight is combined with the known amount of air that passed through the filter
to determine the concentration in the air.

1.2 Health and Welfare Impacts of PM2.5
Numerous scientific studies have linked particle pollution exposure to a variety of problems, including:
 increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty breathing,
for example;
 decreased lung function;
 aggravated asthma;
 development of chronic bronchitis;
 irregular heartbeat;
 nonfatal heart attacks; and
 premature death in people with heart or lung disease.
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People with heart or lung diseases, children and older adults are the most likely to be affected by
particle pollution exposure. However, even if you are healthy, you may experience temporary symptoms
from exposure to elevated levels of particle pollution.

1.3 Fine Particulate Matter in Utah
Excluding wind-blown desert dust events, wild land fires, and holiday related fireworks, elevated PM2.5
in Utah occurs when stagnant cold pools develop during the winter season.
The synoptic conditions that lead to the formation of cold pools in Utah’s nonattainment areas are:
synoptic scale ridging, subsidence, light winds, snow cover (often), and cool to cold surface
temperatures. These conditions occur during winter months, generally mid-November through early
March.
During a winter-time cold pool episode, emissions of PM2.5 precursors react relatively quickly to elevate
overall concentrations, and of course dispersion is very poor due to the very stable air mass. Episodes
may last from a few days to tens of days when meteorological conditions change to once again allow for
good mixing.
The scenario described above leads to exceedances and violations of the 24-hour health standard for
PM2.5. In other parts of the year concentrations are generally low, and even with the high peaks
incurred during winter, are well within the annual health standard for PM2.5.

1.4 2006, NAAQS for PM2.5
In September of 2006, EPA revised the (1997) standards for PM2.5. While the annual standard remained
unchanged at 15 μg/m3, the 24-hr standard was lowered from 65 µg/m3 to 35 µg/m3.
DAQ has monitored PM2.5 since 2000, and found that all areas within the state have been in compliance
with the 1997 standards. At this new 2006 level, all or parts of five counties have collected monitoring
data that is not in compliance with the 24-hr standard.
In 2013, EPA lowered the annual average to 12 μg/m3. Monitoring data shows no instances of
noncompliance with this revised standard.

1.5 PM2.5 Nonattainment Areas in Utah
There are two distinct nonattainment areas for the 2006, PM2.5 standards residing entirely within the
state of Utah. These are the Salt Lake City, UT, and Provo, UT nonattainment areas, which together
encompass what is referred to as the Wasatch Front. A third nonattainment area is more or less
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geographically defined by the Cache Valley which straddles the border between Utah and Idaho (the
Logan, UT – ID nonattainment area.) Figure 1.1 below shows the geographic extent of these areas.
None of these three areas has violated the annual NAAQS for PM2.5. Without exception, the
exceedances leading to 24-hr NAAQS violations are associated with relatively short-term meteorological
occurrences.

Figure 1.1, Nonattainment Areas for the 2006, PM2.5 NAAQS

Each of these three areas was designated, by the EPA, based on the weight of evidence of the following
nine factors recommended in its guidance and any other relevant information:
 pollutant emissions
 air quality data
 population density and degree of urbanization
 traffic and commuting patterns
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 growth
 meteorology
 geography and topography
 jurisdictional boundaries
 level of control of emissions sources
EPA also used analytical tools and data such as pollution roses, fine particulate composition monitoring
data, back trajectory analyses, and the contributing emission score (CES) to evaluate these areas.
While the general meteorological characteristics are identical between the Wasatch Front and Cache
Valley, there are two important differences related to topography. First, the Cache Valley is a closed
basin while the Wasatch Front has many large outlets that connect it to the larger Great Basin. The
large outlets along the Wasatch Front provide the potential for greater advection of pollutants and for a
potentially weaker cold pool. Second, the Cache Valley is a narrow (<20 km) valley bordered by
extremely steep mountains. These topographical differences lead to faster forming, more intense, and
more persistent cold pools in Cache Valley relative to the Wasatch Front.
Because of these differences, the two Wasatch Front areas and the Cache Valley are designated as
separate nonattainment areas; however, they have all been modeled together within the same
modeling domain.

1.6 PM2.5 Precursors
The majority of ambient PM2.5 collected during a typical cold-pool episode of elevated concentration is
secondary particulate matter, born of precursor emissions. The precursor gasses associated with fine
particulate matter are SO2, NOx, volatile organic compounds (VOC), and ammonia (NH3).
Clean Air Act Section 189(e) requires that the control requirements applicable in plans for major
stationary sources of PM10 shall also apply to major stationary sources of PM10 precursors, except where
the Administrator determines that such sources do not contribute significantly to PM10 levels which
exceed the standard in the area.
As this paragraph now applies also to PM2.5 plans the following should be said about the way this plan is
structured.
CAA Section 172 does not include any specific applicability thresholds to identify the size of sources that
States and EPA must consider in the plan’s RACT and RACM analysis. In developing the emissions
inventories underlying the SIP, the criteria of 40 CFR 51 for air emissions reporting requirements was
used to establish a 100 ton per year threshold for identifying a sub-group of stationary point sources
that would be evaluated individually. The control evaluations for each of these sources included PM2.5
as well as PM2.5 precursors. This principle was extended to the non-stationary source categories as well.
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When evaluating the cost per ton necessary to reduce emissions, consideration was given to the
resulting PM2.5 concentrations. Through this process, reasonable controls were identified affecting
PM2.5, SO2, NOx and VOC.
No such controls were identified for ammonia. Ammonia occurs in such abundance that PM2.5
concentrations are not sensitive to reductions in ammonia unless those reductions are very large.
Within the stationary source category, there really were no significant amounts of ammonia to evaluate.
The largest contributor to the ammonia inventory was the agricultural sector, and the maximum
possible amount of ammonia reduction from that sector would still not be enough to affect a reduction
in PM2.5.
Additional information regarding control measures may be found in Chapter 6 as well as the Technical
Support Document (TSD).

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Chapter 2 – REQUIREMENTS FOR 2006, PM2.5 PLAN REVISIONS

2.1 Requirements for Nonattainment SIPs
Section 110 of the Clean Air Act lists the requirements for implementation plans. Many of these
requirements speak to the administration of an air program in general. Section 172 of the Act contains
the plan requirements for nonattainment areas. Some of the more notable requirements identified in
these sections of the Act that pertain to this SIP include:
 Implementation of Reasonably Available Control Measures (RACM) as expeditiously as
practicable
 Reasonable Further Progress (RFP) toward attainment of the National Ambient Air Quality
Standards by the applicable attainment date
 Enforceable emission limits as well as schedules for compliance
 A comprehensive inventory of actual emissions
 Contingency measures to be undertaken if the area fails to make reasonable further progress or
attain the NAAQS by the applicable attainment date
On January 4, 2013, D.C. Circuit Court of Appeals found that EPA had incorrectly interpreted the Clean
Air Act when determining how to implement the National Ambient Air Quality Standards (NAAQS) for
PM2.5. The January 4, 2013 court ruling held that the EPA should have implemented the PM2.5 NAAQS
based on both Clean Air Act (CAA) Subpart 1 (“Nonattainment Areas in General” of “Part D – Plan
Requirements for Nonattainment Areas”) and Subpart 4 (“Additional Provisions for Particulate Matter
Nonattainment Areas”) of Part D, title 1. EPA had (incorrectly) required states to develop their SIPs
based only on Subpart 1. Therefore, as of January 4, 2013, Subpart 4 also applies.
Under Subpart 4, nonattainment areas for particulate matter may carry the classification of either
moderate or serious. Subpart 4 addresses the attainment dates and planning provisions for both
moderate and serious PM nonattainment areas.
In the wake of the decision by the D.C. Circuit, EPA has promulgated a “Deadlines Rule” that identifies
each of Utah’s three PM2.5 nonattainment areas as moderate. It specifies December 31, 2014 as the SIP
submission deadline for these moderate PM2.5 nonattainment areas, and further specifies December 31,
2015 as the attainment date for each area.
More specific requirements for the preparation, adoption, and submittal of implementation plans are
specified in 40 CFR Part 51. Subpart Z of Part 51 had contained provisions for Implementation of PM2.5
National Ambient Air Quality Standards. However, one consequence of the January 4, 2013 Court ruling
was to revoke Subpart Z. This leaves only the more general requirements of Part 51.

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2.2 PM2.5 SIP Guidance
Beyond what had been codified in Subpart Z of Part 51 concerning the Implementation of the PM2.5
NAAQS, EPA had provided additional clarification and guidance in its Clean Air Particulate
Implementation Rule for the 1997, PM2.5 NAAQS (FR 72, 20586) and its subsequent Implementation
Guidance for the 2006, 24-Hour Fine Particle NAAQS (March 2, 2012). This too was revoked by the D.C.
Circuit Court’s decision. Until such time as a new implementation rule for PM2.5 is promulgated, the
Deadlines Rule recommends the General Preamble, EPA’s longstanding general guidance that interprets
the 1990 amendments to the CAA, as the applicable guidance for states to follow while preparing SIPs
for PM2.5 nonattainment areas.

2.3 Summary of this SIP Proposal
This implementation plan was developed to meet the requirements specified in the law, rule, and
appropriate guidance documents identified above. Discussed in the following chapters are: air
monitoring, reasonably available control measures, modeled attainment demonstration, emission
inventories, reasonable further progress toward attainment, transportation conformity, and
contingency measures. Additional information is provided in the technical support document (TSD).
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Chapter 3 – Ambient Air Quality Data

3.1 Measuring Fine Particle Pollution in the Atmosphere
Utah has monitored PM2.5 in its airsheds since 2000 following the promulgation of the 1997, PM2.5
NAAQS which was set at 65 µg/m3 for a 24-hour averaging period. PM2.5 monitoring sites were initially
located based on concentrations of PM10, which historically were measured at sites located based on
emissions of primary particles. PM2.5 concentrations, especially during Utah’s wintertime valley
temperature inversions, tend to be distributed more homogenously within a specific airshed.
Homogeneity of PM2.5 concentrations supports that one or two monitors are adequate to determine
compliance with the NAAQS in specific airsheds. DAQ’s monitors are appropriately located to assess
concentration, trends, and changes in PM2.5 concentrations. During Utah’s wintertime cold-pool
episodes, every day sampling and real time monitoring are needed for modeling and public notification.

3.2 Utah’s Air Monitoring Network
The Air Monitoring Center (AMC) maintains an ambient air monitoring network in Utah that collects
both air quality and meteorological data. Figure 3.1 shows the location of sites along the Wasatch Front
that collect PM2.5 data. Twelve sites collect PM2.5 data using the Federal Reference Method (FRM); PM2.5
is collected on filters over a 24 hour period and its mass is measured gravimetrically. Seven of those
sites also measure PM2.5 concentrations continuously in real-time. Real-time PM2.5 data is useful both
for pollution forecasting and to compare with 24-hour concentrations of PM2.5 collected on filters. Of
the twelve sites that use the FRM to measure PM2.5, six sites collect PM2.5 data daily and six sites collect
PM2.5 data on every third day. Three sites along the Wasatch Front collect speciated PM2.5. Particulate
matter on the speciated PM2.5 filters is analyzed for organic and inorganic carbon and a list of 48
elements. PM2.5 speciation data is particularly useful in helping to identify sources of particulate matter.
The ambient air quality monitoring network along Utah’s Wasatch Front and in the Cache Valley meets
EPA requirements for monitoring networks.
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Figure 3.1, Utah’s PM2.5 Air Monitoring Network

3.3 Annual PM2.5 – Mean Concentrations
The procedure for evaluating PM2.5 data with respect to the NAAQS is specified in Appendix N to 40 CFR
Part 50. Generally speaking, the annual PM2.5 standard is met when a three-year average of annual
mean values is less than or equal to 12.0 µg/m3. Each annual mean is itself an average of four quarterly
averages.
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Table 3.1, below shows the running 3-year averages of annual mean values for each of Utah’s
monitoring locations. The data in the table spans the years 2008 through 2012. These are the years
surrounding 2010, the year for which the baseline modeling inventory was prepared. It can be seen
from the data that there are no locations at which the annual NAAQS was violated. It should be noted
that the conclusion would be no different if the most recent data from 2013 were considered.

Table 3.1, PM2.5 Annual Mean Concentrations

3.4 Daily PM2.5 – Averages of 98th Percentiles and Design Values
The procedure for evaluating PM2.5 data with respect to the NAAQS is specified in Appendix N to 40 CFR
Part 50. Generally speaking, the 24-hr. PM2.5 standard is met when a three-year average of 98th
percentile values is less than or equal to 35 µg/m3. Each year’s 98th percentile is the daily value below
which 98% of all daily values fall.
Table 3.2, below shows the running 3-year averages of 98th percentile values for each of Utah’s
monitoring locations. Again, the data in the table spans the years 2008 through 2012 which are the
years surrounding 2010, the baseline modeling inventory. It can be seen from the data that there are
many locations at which the 24-hr. NAAQS has been violated, and this SIP has been structured to
specifically address the 24-hr. standard.

Location County 08 - 10 09 - 11 10 - 12
Logan (Combined POC 1 & 2)Cache 10.0 9.7 8.7
Brigham City Box Elder 8.3 8.2 7.7
Ogden 2 (POC 1)Weber 9.7 9.5 9.1
Harrisville Weber 8.6 8.3 7.6
Bountiful Davis 9.8 9.2 8.3
Rose Park (POC 1)Salt Lake 10.4 9.7 9.2
Magna Salt Lake 8.5 8.4 7.7
Hawthorn (POC 1)Salt Lake 10.4 9.7 8.8
Tooele Tooele 6.8 6.8 6.3
Lindon (POC 1)Utah 9.8 9.1 8.3
North Provo Utah 9.4 8.7 8.1
Spanish Fork Utah 8.8 8.5 7.7
3-Year Average of Annual Mean Concentrations
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Table 3.2, 24-hour PM2.5 Monitored Design Values

As mentioned in the forgoing paragraph, this SIP is structured to address the 24-hr. PM2.5 NAAQS. As
such the modeled attainment test must consider monitored baseline design values from each of these
locations. EPA’s modeling guidance1 recommends this be calculated using three-year averages of the
98th percentile values. To calculate the monitored baseline design value, EPA recommends an average
of three such three-year averages that straddle the baseline inventory. 2010 is the year represented by
the baseline inventory. Therefore, the three-year average of 98th percentile values collected from 2008-
2010 would be averaged together with the three-year averages for 2009-2011 and 2010-2012 to arrive
at the site-specific monitored baseline design values. These values are also shown in Table 3.22.

3.5 Composition of Fine Particle Pollution – Speciated Monitoring Data
DAQ operates three PM2.5 speciation sites. The Hawthorne site in Salt Lake County is one of 54
Speciation Trends Network (STN) sites operated nationwide on an every-third day sampling schedule.
Sites at Bountiful/Viewmont in Davis County and Lindon in Utah County are State and Local Air
Monitoring Stations (SLAMS) PM2.5 speciation sites that operate on an every-sixth-day sampling
schedule.

1 Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for ozone,
PM2.5, and Regional Haze (EPA -454B-07-002, April 2007)
2 Recalculating the design values by replacing the 98th percentiles from 2008 with the most recent 98th percentiles
from 2013 has a mixed effect throughout the monitoring network, with some sites increasing and others
decreasing. The design value for Logan, the controlling monitor, would increase by 1.1 µg/m3. This increase is not
significant enough to change the conclusion drawn in Section 5.9.
Location County 08 - 10 09 - 11 10 - 12
Logan (Combined POC 1 & 2)Cache 42.6 42.4 37.2 40.7
Brigham City Box Elder 42.5 40.1 37.2 39.9
Ogden 2 (POC 1)Weber 37.0 41.1 37.4 38.5
Harrisville Weber 35.6 36.6 33.2 35.1
Bountiful Davis 37.7 40.3 34.4 37.5
Rose Park (POC 1)Salt Lake 40.9 40.7 35.4 39.0
Magna Salt Lake 32.8 34.5 30.3 32.5
Hawthorn (POC 1)Salt Lake 43.6 44.5 38.1 42.1
Tooele Tooele 25.9 27.1 24.4 25.8
Lindon (POC 1)Utah 40.5 40.9 32.4 37.9
North Provo Utah 36.4 35.1 28.6 33.4
Spanish Fork Utah 39.3 41.7 34.6 38.5
Site-Specific Baseline Design Values:Baseline Design Value3-Year Average of 98th Percentiles
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Filters are prepared by the EPA contract laboratory and shipped to Utah for sampling. Samples are
collected for particulate mass, elemental analysis, identification of major cations and anions, and
concentrations of elemental and organic carbon as well as crustal material present in PM2.5. Carbon
sampling and analysis changed in 2007 to match the Interagency Monitoring of Protected Visual
Environments (IMPROVE) method using a modified IMPROVE sampler at all sites.
The PM2.5 is collected on three types of filters: teflon, nylon, and quartz. Teflon filters are used to
characterize the inorganic contents of PM2.5. Nylon filters are used to quantify the amount of
ammonium nitrate, and quartz filters are used to quantify the organic and inorganic carbon content in
the ambient PM2.5.
Data from the speciation network show the importance of volatile secondary particulates during the
colder months. These particles are significantly lost in FRM PM2.5 sampling.
During the winter periods between 2009 and 2011, DAQ conducted special winter speciation studies
aimed at better characterization of PM2.5 during the high pollution episodes. These studies were
accomplished by shifting the sampling of the Chemical Speciation Network monitors to 1-in-2 schedule
during the months of January and February. Speciation monitoring during the winter high-pollution
episodes produced similar results in PM2.5 composition each year.
The results of the speciation studies lead to the conclusion that the exceedances of the PM2.5 NAAQS are
a result of the increased portion of the secondary PM2.5 that was chemically formed in the air and not
emitted directly into the troposphere.
Logan – Page 22
Figure 3.2 below shows the contribution of the identified compounds from the speciation sampler both
during a winter atmospheric inversion period and during a clear winter period.

Figure 3.2, Composite Wintertime PM2.5 Speciation Profiles
Ammonium
(17%)
Nitrate
(41%)
Organic Matter
(19%)
Elemental
Carbon
(3%)
Sulfate
(6%)
Crustal:
(3%)
Missing Mass
(11%)
Mean Contributions to PM2.5 During the Inversion
Episodes
(HW, Winter 2010-2011)
Ammonium:
Nitrate:
OC (mass):
EC:
Sulfate:
Crustal:
Sodium:
Missing Mass:
Ammonium
(10%)
Nitrate
(31%)
Organic Mass
(32%)
EC
(8%)
Sulfate: 5%
Crustal:
4%
Sodium:
1%
Missing Mass:
8%
Mean Contributions to PM2.5 During the Non-Inversion
Days
(HW, Winter 2010-2011)
Ammonium:
Nitrate:
OC (mass):
EC:
Sulfate:
Crustal:
Sodium:
Missing Mass:
Logan – Page 23
3.6 PM2.5 Saturation Studies
Utah State University conducted a study of the homogeneity of PM10 in Cache Valley in 2002-2003 and a
study of the homogeneity of PM2.5 in 2003-2004. In addition to the permanent DAQ air quality
monitoring site in Logan, seventeen sites measuring PM2.5 concentrations were established in Cache
Valley. Measurements of PM2.5 concentrations were made every six days from November 2003 –
February 2004. Several temperature inversions developed during the course of the study with PM2.5
concentrations in Logan ranging from 3-128 µg/m3. In general, the study found that PM2.5
concentrations were homogenous throughout the entirety of Cache Valley. On days with PM2.5
concentrations < 65 µg/m3, mean PM2.5 concentrations at 11 of the 17 sites had values within 20% of the
mean PM2.5 concentration for the entire valley. PM2.5 concentrations were generally most homogenous
throughout Cache Valley on days when PM2.5 concentrations were > 65 µg/m3. On high PM2.5 days (> 65
µg/m3), mean PM2.5 concentrations at only two sites were statistically different from the mean PM2.5
concentration for all of Cache Valley. The study concluded that PM2.5 concentrations in Cache Valley
were homogenous, within a 95% confidence interval, during the winter of 2003-2004.1 PM2.5 saturation
studies have not been conducted in other regions of Utah.

3.7 PCAP Study
The Persistent Cold Air Pooling Study (PCAPS) is a National Science Foundation-funded project
conducted by the University of Utah to investigate the processes leading to the formation, maintenance
and destruction of persistent temperature inversions in Salt Lake Valley. The study ended in March of
2014. Field work for the project was conducted in the winter of 2010-2011 and focused on the
meteorological dynamics of temperature inversions in the Salt Lake Valley and in the Bingham Canyon
pit mine in the southwest corner of Salt Lake Valley. In addition to identifying key meteorological
processes involved in the dynamics of temperature inversions in Salt Lake Valley, the other primary
objectives of PCAPS is to determine how persistent temperature inversions affect air pollution transport
and diffusion in urban basins and to develop more accurate meteorological models describing the
formation, persistence and dispersion of temperature inversions in Salt Lake Valley.
Analyses of most data sets collected during the PCAPS are still underway. However, one study
examining PM2.5 concentrations along an elevation gradient north of Salt Lake City (1300-1750 meters)
showed that PM2.5 concentrations generally decreased with altitude and increased with time during a
single temperature inversion event.2 Final results from PCAPS will help DAQ understand both how
persistent temperature inversions affect PM2.5 concentrations along the Wasatch Front and will enhance
DAQ’s ability to accurately forecast the formation and breakup of temperature inversion that lead to
poor wintertime air quality.

1 Martin, R., and G.W. Koford, 2006: Valley-wide PM10 and PM2.5 Saturation (Homogeneity) Studies, found within:
Cache Valley Air Quality Studies: A Summary of Research Conducted.

2 Silcox, G.D., K.E. Kelly, E.T. Crosman, C.D. Whiteman, and B.L. Allen, 2012: Wintertime PM2.5 concentrations in
Utah’s Salt Lake Valley during persistent multi-day cold air pools. Atmospheric Environment, 46, 17-24.
Logan – Page 24
3.8 Ammonia (NH3) Studies
The Division of Air Quality deployed an ammonia monitor as a part of the special winter study for 2009.
A URG 9000 instrument was used to record hourly values of ambient ammonia between the months of
December and February.
The resulting measurements showed that the ambient concentration of ammonia tended to be
generally an order of magnitude higher than those of nitric acid: 12-17 ppbv and 1-2 ppbv, respectively.
Unfortunately, the use of the instrument proved to be excessively labor intensive due to the high
frequency of calibrations and corrections for drift. The data obtained during the winter of 2009, albeit
valuable for rough estimation of the ambient ammonia concentrations, contained an abnormal amount
of error for accurate mechanistic analysis.
Logan – Page 25
Chapter 4 – EMISSION INVENTORY DATA

4.1 Introduction
The emissions inventory is one means used by the state to assess the level of pollutants and precursors
released into the air from various sources. The methods by which emissions inventories are collected
and calculated are constantly improving in response to better analysis and more comprehensive rules.
The inventories underlying this SIP were compiled using the best information available.
The sources of emissions that were inventoried may be discussed as belonging to four general
categories: industrial point sources, on-road mobile sources, off-road mobile sources., and area sources
which represent a collection of smaller, more numerous point sources, residential activities such a
home heating, and in some cases biogenic emissions.
This SIP is concerned with PM2.5, both primary in its origin and secondary, referring to its formation
removed in time and space from the point of origin for certain precursor gasses. Hence, the pollutants
of concern, at least for inventory development purposes, included PM2.5, SO2, NOx, VOC, and NH3.
On-road mobile sources are inventoried using EPA’s MOVES2010 model, in conjunction with information
generated by travel demand models such as vehicle speeds and miles traveled. The inventory
information is calculated in units of tons per day, adjusted for winter conditions. Emissions from the
other three categories are calculated in terms of tons per year.
Prior to use in the air quality model, the emissions are pre-processed to account for the seasonality of
Utah’s difficulty with secondary PM2.5 formation during winter months. These temporal adjustments
also account for daily and weekly activity patterns that affect the generation of these emissions.
To acknowledge the episodic and seasonal nature of Utah’s elevated PM2.5 concentrations, inventory
information presented herein is, unless otherwise noted, a reflection of the temporal adjustments made
prior to air quality modeling. This makes more appropriate the use of these inventories for such
purposes as correlation with measured PM2.5 concentrations, control strategy evaluation, establishing
budgets for transportation conformity, and tracking rates of progress.
There are various time horizons that are significant to the development of this SIP. It is first necessary to
look at past episodes of elevated PM2.5 concentrations in order to develop the air quality model. The
episodes studied as part of the SIP occurred in 2007, 2008, 2009, and 2010. It is then necessary to look
several years into the future when developing emission control strategies. The significant time horizon
for this plan relates to the statutory attainment date, December 31, 2015. A projected inventory for
2015 is prepared and compared with a baseline inventory that is contemporaneous with the monitored
design values discussed in Section 3.4. This baseline is represented by the year 2010. Inventories must
be prepared to evaluate all of these time horizons.

Logan – Page 26
4.2 The 2008 Emissions Inventory
The forgoing paragraph identified numerous points in time for which an understanding of emissions to
the air is important to plan development. The basis for each of these assessments was the 2008 tri-
annual inventory. This inventory represented, at the time it was selected for use, the most recent
comprehensive inventory compiled by UDAQ. In addition to the large major point sources that are
required to report emissions every year, the tri-annual inventories consider emissions from many more,
smaller point sources. These inventories are collected in accordance with state and federal rules that
ensure proper methods and comprehensive quality assurance.
Thus, to develop other inventories for each of the years discussed above, the 2008 inventory was either
back-cast and adjusted for certain episodic conditions, or forecast to represent more typical conditions.

4.3 Characterization of Utah’s Airsheds
As said at the outset, an emissions inventory provides a means to assess the level of pollutants and
precursors released into the air from various sources. This in turn allows for an overall assessment of a
particular airshed or even a comparison of one airshed to another.
The modeling analysis used to support this SIP considers a regional domain that encompasses three
distinct airsheds belonging to three distinct PM2.5 nonattainment areas; The Cache Valley (the Logan
UT/ID nonattainment area), the central Wasatch Front (Salt Lake City, UT nonattainment area), and the
southern Wasatch Front (Provo, UT nonattainment area).
The inventories developed for each of these three areas illustrate many similarities but also a few
notable differences. All three areas are more or less dominated by a combination of on-road mobile and
area sources. However, emissions from large point sources are non-existent in the Cache Valley. These
emissions are situated along the Wasatch Front, and primarily exhibited in the Salt Lake City
nonattainment area. Conversely, most of the agricultural emissions are located in the Cache Valley.

The tables presented below provide a broad overview of the emissions in the respective areas. They are
organized to show the relative contributions of emissions by source category (e.g. point / area / mobile).
Logan – Page 27
Table 4.1 shows the 2010 Baseline emissions in each area of the modeling domain.

Table 4.1, Emissions Summary for 2010 (SMOKE). Emissions are presented in tons per average winter day.
Mobile source emissions summaries are from the AP-42 (road dust) and MOVES model output. PM2.5 for mobile
sources includes tire and brake wear, sulfate, elemental and organic carbon, and road dust. VOC for mobile
sources includes refueling spillage and displacement vapor loss emissions.

NA-Area Source Category PM2.5 NOX VOC NH3 SO2
2010 Logan, UT-ID
Sum of Emissions (tpd)Area Sources 0.54 1.63 4.16 4.31 0.26
Mobile Sources 0.67 6.48 4.99 0.12 0.04
NonRoad 0.13 1.15 2.28 0.00 0.02
Point Sources 0.00 0.02 0.63 0.00 0.00
Total 1.35 9.28 12.06 4.43 0.32
2010 Provo, UT
Sum of Emissions (tpd)Area Sources 1.86 5.56 12.77 6.53 0.28
Mobile Sources 2.20 25.39 15.63 0.44 0.16
NonRoad 0.31 4.40 1.71 0.00 0.09
Point Sources 0.26 0.93 0.67 0.29 0.03
Total 4.63 36.29 30.78 7.26 0.56
2010 Salt Lake City, UT
Sum of Emissions (tpd)Area Sources 5.87 17.71 51.53 17.96 0.88
Mobile Sources 8.59 99.63 62.51 1.86 0.63
NonRoad 1.27 23.04 9.50 0.01 0.66
Point Sources 3.89 20.14 6.48 0.64 10.64
Total 19.62 160.51 130.02 20.47 12.81
2010 Surrounding Areas
Sum of Emissions (tpd)Area Sources 1.78 3.08 13.95 34.29 1.13
Mobile Sources 2.31 28.89 11.03 0.33 0.15
NonRoad 0.57 7.73 10.66 0.00 0.14
Point Sources 3.39 129.34 2.92 0.75 43.43
Total 8.04 169.03 38.57 35.38 44.85
2010 Total
Logan – Page 28
Table 4.2 is specific to the Logan, UT-ID nonattainment area, and shows emissions for both the baseline
year and the attainment year. These totals include projections concerning growth in population, vehicle
miles traveled, and the economy. They also include the effects of emissions control strategies that are
either already promulgated or were required as part of the SIP.

Table 4.2, Emissions Summaries for the Logan, UT-ID Nonattainment Area; Baseline and Attainment Year
(SMOKE). Emissions are presented in tons per average winter day. Mobile source emissions summaries are from
the AP-42 (road dust) and MOVES model output. PM2.5 for mobile sources includes tire and brake wear, sulfate,
elemental and organic carbon, and road dust. VOC for mobile sources includes refueling spillage and
displacement vapor loss emissions.

The 2010 Baseline and 2015 projected emissions estimates are calculated from the Sparse Matrix
Operator Kernel Model (SMOKE). More detailed inventory information may be found in the Technical
Support Document (TSD).
NA-Area Source Category PM2.5 NOX VOC NH3 SO2
2010 Logan, UT-ID
Sum of Emissions (tpd)Area Sources 0.54 1.63 4.16 4.31 0.26
Mobile Sources 0.67 6.48 4.99 0.12 0.04
NonRoad 0.13 1.15 2.28 0.00 0.02
Point Sources 0.00 0.02 0.63 0.00 0.00
Total 1.35 9.28 12.06 4.43 0.32
2015 Logan, UT-ID
Sum of Emissions (tpd)Area Sources 0.40 1.59 3.75 4.08 0.27
Mobile Sources 0.32 4.49 3.36 0.10 0.03
NonRoad 0.10 0.81 1.77 0.00 0.01
Point Sources 0.00 0.00 0.00 0.00 0.00
Total 0.82 6.89 8.88 4.19 0.31
Logan – Page 29
Chapter 5 – ATTAINMENT DEMONSTRATION

5.1 Introduction
UDAQ conducted a technical analysis to support the development of Utah’s 24-hr PM2.5 State
Implementation Plan (SIP). The analyses include preparation of emissions inventories and
meteorological data, and the evaluation and application of regional photochemical model. An analysis
using observational datasets will be shown to detail the chemical regimes of Utah’s Nonattainment
areas.

5.2 Photochemical Modeling
Photochemical models are relied upon by federal and state regulatory agencies to support their
planning efforts. Used properly, models can assist policy makers in deciding which control programs are
most effective in improving air quality, and meeting specific goals and objectives.
The air quality analyses were conducted with the Community Multiscale Air Quality (CMAQ) Model
version 4.7.1, with emissions and meteorology inputs generated using SMOKE and WRF, respectively.
CMAQ was selected because it is the open source atmospheric chemistry model co-sponsored by EPA
and the National Oceanic Atmospheric Administration (NOAA), thus approved by EPA for this plan.

5.3 Domain/Grid Resolution
UDAQ selected a high resolution 4-km modeling domain to cover all of northern Utah including the
portion of southern Idaho extending north of Franklin County and west to the Nevada border (Figure
5.1). This 97 x 79 horizontal grid cell domain was selected to ensure that all of the major emissions
sources that have the potential to impact the nonattainment areas were included. The vertical
resolution in the air quality model consists of 17 layers extending up to 15 km, with higher resolution in
the boundary layer.
Logan – Page 30

Figure 5.1: Northern Utah photochemical modeling domain.

5.4 Episode Selection
According to EPA’s April 2007 “Guidance on the Use of Models and Other Analyses for Demonstrating
Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze” the selection of SIP episodes for
modeling should consider the following 4 criteria:
1. Select episodes that represent a variety of meteorological conditions that lead to elevated
PM2.5.
2. Select episodes during which observed concentrations are close to the baseline design value.
3. Select episodes that have extensive air quality data bases.
4. Select enough episodes such that the model attainment test is based on multiple days at each
monitor violating NAAQS.

Logan – Page 31
In general, UDAQ wanted to select episodes with hourly PM2.5 concentrations that are reflective of
conditions that lead to 24-hour NAAQS exceedances. From a synoptic meteorology point of view, each
selected episode features a similar pattern. The typical pattern includes a deep trough over the eastern
United States with a building and eastward moving ridge over the western United States. The episodes
typically begin as the ridge begins to build eastward, near surface winds weaken, and rapid stabilization
due to warm advection and subsidence dominate. As the ridge centers over Utah and subsidence peaks,
the atmosphere becomes extremely stable and a subsidence inversion descends towards the surface.
During this time, weak insolation, light winds, and cold temperatures promote the development of a
persistent cold air pool. Not until the ridge moves eastward or breaks down from north to south is there
enough mixing in the atmosphere to completely erode the persistent cold air pool.
From the most recent 5-year period of 2007-2011, UDAQ developed a long list of candidate PM2.5
wintertime episodes. Three episodes were selected. An episode was selected from January 2007, an
episode from February 2008, and an episode during the winter of 2009-2010 that features multi-event
episodes of PM2.5 buildup and washout. Further detail of the episodes is below:

 Episode 1: January 11-20, 2007
A cold front passed through Utah during the early portion of the episode and brought very cold
temperatures and several inches of fresh snow to the Wasatch Front. The trough was quickly followed
by a ridge that built north into British Columbia and began expanding east into Utah. This ridge did not
fully center itself over Utah, but the associated light winds, cold temperatures, fresh snow, and
subsidence inversion produced very stagnant conditions along the Wasatch Front. High temperatures in
Salt Lake City throughout the episode were in the high teens to mid-20’s Fahrenheit.
Figure 5.2 shows hourly PM2.5 concentrations from Utah’s 4 PM2.5 monitors for January 11-20, 2007. The
first 6 to 8 days of this episode are suited for modeling. The episode becomes less suited after January
18 because of the complexities in the meteorological conditions leading to temporary PM2.5 reductions.

Figure 5.2: Hourly PM2.5 concentrations for January 11-20, 2007
Logan – Page 32
 Episode 2: February 14-18, 2008
The February 2008 episode features a cold front passage at the start of the episode that brought
significant new snow to the Wasatch Front. A ridge began building eastward from the Pacific Coast and
centered itself over Utah on Feb 20th. During this time a subsidence inversion lowered significantly
from February 16 to February 19. Temperatures during this episode were mild with high temperatures
at SLC in the upper 30’s and lower 40’s Fahrenheit.
The 24-hour average PM2.5 exceedances observed during the proposed modeling period of February 14-
19, 2008 were not exceptionally high. What makes this episode a good candidate for modeling are the
high hourly values and smooth concentration build-up. The first 24-hour exceedances occurred on
February 16 and were followed by a rapid increase in PM2.5 through the first half of February 17 (Figure
5.3). During the second half of February 17, a subtle meteorological feature produced a mid-morning
partial mix-out of particulate matter and forced 24-hour averages to fall. After February 18, the
atmosphere began to stabilize again and resulted in even higher PM2.5 concentrations during February
20, 21, and 22. Modeling the 14th through the 19th of this episode should successfully capture these
dynamics. The smooth gradual build-up of hourly PM2.5 is ideal for modeling.

Figure 5.3: Hourly PM2.5 concentrations for February 14-19, 2008

 Episode 3: December 13, 2009 – January 18, 2010
The third episode that was selected is more similar to a “season” than a single PM2.5 episode (Figure
5.4). During the winter of 2009 and 2010, Utah was dominated by a semi-permanent ridge of high
pressure that prevented strong storms from crossing Utah. This 35 day period was characterized by 4 to
5 individual PM2.5 episodes each followed by a partial PM2.5 mix out when a weak weather system
passed through the ridge. The long length of the episode and repetitive PM2.5 build-up and mix-out
cycles makes it ideal for evaluating model strengths and weaknesses and PM2.5 control strategies.
Logan – Page 33

Figure 5.4: 24-hour average PM2.5 concentrations for December-January, 2009-10.

5.5 Meteorological Data
Meteorological inputs were derived using the Weather Research and Forecasting (WRF), Advanced
Research WRF (WRF-ARW) model version 3.2. WRF contains separate modules to compute different
physical processes such as surface energy budgets and soil interactions, turbulence, cloud microphysics,
and atmospheric radiation. Within WRF, the user has many options for selecting the different schemes
for each type of physical process. There is also a WRF Preprocessing System (WPS) that generates the
initial and boundary conditions used by WRF, based on topographic datasets, land use information, and
larger-scale atmospheric and oceanic models.
Model performance of WRF was assessed against observations at sites maintained by the Utah Air
Monitoring Center. A summary of the performance evaluation results for WRF are presented below:
 The biggest issue with meteorological performance is the existence of a warm bias in surface
temperatures during high PM2.5 episodes. This warm bias is a common trait of WRF modeling
during Utah wintertime inversions.
 WRF does a good job of replicating the light wind speeds (< 5 mph) that occur during high PM2.5
episodes.
 WRF is able to simulate the diurnal wind flows common during high PM2.5 episodes. WRF
captures the overnight downslope and daytime upslope wind flow that occurs in Utah valley
basins.
 WRF has reasonable ability to replicate the vertical temperature structure of the boundary
layer (i.e., the temperature inversion), although it is difficult for WRF to reproduce the inversion
when the inversion is shallow and strong (i.e., an 8 degree temperature increase over 100
vertical meters).
Logan – Page 34
5.6 Photochemical Model Performance Evaluation
The model performance evaluation focused on the magnitude, spatial pattern, and temporal variation of
modeled and measured concentrations. This exercise was intended to assess whether, and to what
degree, confidence in the model is warranted (and to assess whether model improvements are
necessary).
CMAQ model performance was assessed with observed air quality datasets at UDAQ-maintained air
monitoring sites (Figure 5.5). Measurements of observed PM2.5 concentrations along with gaseous
precursors of secondary particulate (e.g., NOx, ozone) and carbon monoxide are made throughout
winter at most of the locations in Figure 5.5. PM2.5 speciation performance was assessed using the three
Speciation Monitoring Network Sites (STN) located at the Hawthorne site in Salt Lake City, the Bountiful
site in Davis County, and the Lindon site in Utah County.

Figure 5.5: UDAQ monitoring network.
Logan – Page 35
A spatial plot is provided for modeled 24-hr PM2.5 for 2010 January 03 in Figure 5.6. The spatial plot
shows the model does a reasonable job reproducing the high PM2.5 values, and keeping those high
values confined in the valley locations where emissions occur.

Figure 5.6: Spatial plot of CMAQ modeled 24-hr PM2.5 (µg/m3) for 2010 Jan. 03.

Time series of 24-hr PM2.5 concentrations for the 13 Dec. 2009 – 15 Jan. 2010 modeling period are
shown in Figs. 5.7 – 5.10 at the Hawthorne site in Salt Lake City (Fig. 5.7), the Ogden site in Weber
County (Fig 5.8), the Lindon site in Utah County (Fig. 5.9), and the Logan site in Cache County (Fig. 5.10).
For the most part, CMAQ replicates the buildup and washout of each individual episode. While CMAQ
builds 24-hr PM2.5 concentrations during the 08 Jan. – 14 Jan. 2010 episode, it was not able to produce
the > 60 µg/m3 concentrations observed at the monitoring locations.
It is often seen that CMAQ “washes” out the PM2.5 episode a day or two earlier than that seen in the
observations. For example, on the day 21 Dec. 2009, the concentration of PM2.5 continues to build while
CMAQ has already cleaned the valley basins of high PM2.5 concentrations. At these times, the observed
Logan – Page 36
cold pool that holds the PM2.5 is often very shallow and winds just above this cold pool are southerly and
strong before the approaching cold front. This situation is very difficult for a meteorological and
photochemical model to reproduce. An example of this situation is shown in Fig. 5.11, where the lowest
part of the Salt Lake Valley is still under a very shallow stable cold pool, yet higher elevations of the
valley have already been cleared of the high PM2.5 concentrations.
During the 24 – 30 Dec. 2009 episode, a weak meteorological disturbance brushes through the
northernmost portion of Utah. It is noticeable in the observations at the Ogden monitor at 25 Dec. as
PM2.5 concentrations drop on this day before resuming an increase through Dec. 30. The meteorological
model and thus CMAQ correctly pick up this disturbance, but completely clears out the building PM2.5;
and thus performance suffers at the most northern Utah monitors (e.g. Ogden, Logan). The monitors to
the south (Hawthorne, Lindon) are not influence by this disturbance and building of PM2.5 is replicated
by CMAQ. This highlights another challenge of modeling PM2.5 episodes in Utah. Often during cold pool
events, weak disturbances will pass through Utah that will de-stabilize the valley inversion and cause a
partial clear out of PM2.5. However, the PM2.5 is not completely cleared out, and after the disturbance
exits, the valley inversion strengthens and the PM2.5 concentrations continue to build. Typically, CMAQ
completely mixes out the valley inversion during these weak disturbances.

Figure 5.7: 24-hr PM2.5 time series (Hawthorne). Observed 24-hr PM2.5 (blue trace) and CMAQ modeled 24-hr
PM2.5 (red trace).

Hawthorne
0
10
20
30
40
50
60
70
80
8-Dec 13-Dec 18-Dec 23-Dec 28-Dec 2-Jan 7-Jan 12-Jan 17-Jan
2009-2010
24
-
h
r

P
M
2
.
5

(
u
g
/
m
3
)
Obs.
Model
Logan – Page 37

Figure 5.8: 24-hr PM2.5 time series (Ogden). Observed 24-hr PM2.5 (blue trace) and CMAQ modeled 24-hr PM2.5
(red trace).

Figure 5.9: 24-hr PM2.5 time series (Lindon). Observed 24-hr PM2.5 (blue trace) and CMAQ modeled 24-hr PM2.5
(red trace).

Ogden
0
10
20
30
40
50
60
8-Dec 13-Dec 18-Dec 23-Dec 28-Dec 2-Jan 7-Jan 12-Jan 17-Jan
2009-2010
24
-
h
r

P
M
2
.
5

(
u
g
/
m
3
)
Obs.
Model
Lindon
0
10
20
30
40
50
60
70
8-Dec 13-Dec 18-Dec 23-Dec 28-Dec 2-Jan 7-Jan 12-Jan 17-Jan
2009-2010
24
-
h
r

P
M
2
.
5

(
u
g
/
m
3
)
Obs.
Model
Logan – Page 38

Figure 5.10: 24-hr PM2.5 time series (Logan). Observed 24-hr PM2.5 (blue trace) and CMAQ modeled 24-hr PM2.5
(red trace).

Figure 5.11: An example of the Salt Lake Valley at the end of a high PM2.5 episode. The lowest elevations of the
Salt Lake Valley are still experiencing an inversion and elevated PM2.5 concentrations while the PM2.5 has been
‘cleared out’ throughout the rest of the valley. These ‘end of episode’ clear out periods are difficult to replicate
in the photochemical model.

Logan – Page 39
Generally, the performance of CMAQ to replicate the buildup and clear out of PM2.5 is good. However, it
is important to verify that CMAQ is replicating the components of PM2.5 concentrations. PM2.5 simulated
and observed speciation is shown at the 3 STN sites in Figures 5.12 – 5.14. The observed speciation is
constructed using days in which the STN filter 24-hr PM2.5 concentration was > 35 µg/m3. For the 2009-
2010 modeling period, the observed speciation pie charts were created using 8 filter days at Hawthorne,
6 days at Lindon, and 4 days at Bountiful. The speciation of this small dataset appears similar to a
comparison of a larger dataset of STN filter speciated data from 2005-2010 for high wintertime PM2.5
days (see Figure 3.2 for one of these at Hawthorne).
The simulated speciation is constructed using modeling days that produced 24-hr PM2.5 concentrations >
35 µg/m3. Using this criterion, the simulated speciation pie chart is created from 18 modeling days for
Hawthorne, 14 days at Lindon, and 14 days at Bountiful.
At all 3 STN sites, the percentage of simulated nitrate is greater than 40%, while the simulated
ammonium percentage is at ~15%. This indicates that the model is able to replicate the secondarily
formed particulates that typically make up the majority of the measured PM2.5 on the STN filters during
wintertime pollution events.
The percentage of model simulated organic carbon is ~13% at all STN sites, which is in agreement with
the observed speciation of organic carbon at Hawthorne and slightly overestimated (by ~3%) at Lindon
and Bountiful.
There is no STN site in the Logan nonattainment area, and very little speciation information available in
the Cache Valley. Figure 5.15 shows the model simulated speciation at Logan. Ammonium (17%) and
nitrate (56%) make up a higher percentage of the simulated PM2.5 at Logan when compared to sites
along the Wasatch Front.
Figure 5.12: The composition of observed and model simulated average 24-hr PM2.5 speciation averaged over
days when an observed and modeled day had 24-hr concentrations > 35 µg/m3 at the Hawthorne STN site.

Logan – Page 40

Figure 5.13: The composition of observed and model simulated average 24-hr PM2.5 speciation averaged over
days when an observed and modeled day had 24-hr concentrations > 35 µg/m3 at the Bountiful STN site.

Figure 5.14: The composition of observed and model simulated average 24-hr PM2.5 speciation averaged over
days when an observed and modeled day had 24-hr concentrations > 35 µg/m3 at the Lindon STN site.

Logan – Page 41

Figure 5.15: The composition of model simulated average 24-hr PM2.5 speciation averaged over days when a
modeled day had 24-hr concentrations > 35 µg/m3 at the Logan monitoring site. No observed speciation data is
available for Logan.

5.7 Summary of Model Performance
Model performance for 24-hr PM2.5 is good and generally acceptable and can be characterized as
follows:
 Good replication of the episodic buildup and clear out of PM2.5. Often the model will clear out
the simulated PM2.5 a day too early at the end of an episode. This clear out time period is
difficult to model (i.e., Figure 5.11).
 Good agreement in the magnitude of PM2.5, as the model can consistently produce the high
concentrations of PM2.5 that coincide with observed high concentrations.
 Spatial patterns of modeled 24-hr PM2.5, show for the most part, that the PM2.5 is being confined
in the valley basins, consistent to what is observed.
 Speciation and composition of the modeled PM2.5 matches the observed speciation quite well.
Modeled and observed nitrate are between 40% and 50% of the PM2.5. Ammonium is between
15% and 20% for both modeled and observed PM2.5, while modeled and observed organic
carbon falls between 10% to 13% of the total PM2.5.

Logan – Page 42
Several observations should be noted on the implications of these model performance findings on the
attainment modeling presented in the following section. First, it has been demonstrated that model
performance overall is acceptable and, thus, the model can be used for air quality planning purposes.
Second, consistent with EPA guidance, the model is used in a relative sense to project future year
values. EPA suggests that this approach “should reduce some of the uncertainty attendant with using
absolute model predictions alone.” Furthermore, the attainment modeling is supplemented by
additional information to provide a weight of evidence determination.

5.8 Modeled Attainment Test
UDAQ employed Model Attainment Test Software (MATS) for the modeled attainment test at grid cells
near monitors. MATS is designed to interpolate the species fractions of the PM mass from the Speciation
Trends Network (STN) monitors to the FRM monitors. The model also calculates the relative response
factor (RRF) for grid cells near each monitor and uses these to calculate a future year design value for
these cells.
MATS results for future year modeling is presented in Figure 5.16. The future year design values are
presented with and without SIP controls for 2015 (the attainment year). For comparison purposes, the
monitored design value is also presented for the base year, 2010.

Figure 5.16, Model Results for the Logan, UT-ID Nonattainment Area

Table 5.1 presents the same information in tabular form, and also includes any additional monitoring
locations in the nonattainment area.
Logan – Page 43

Table 5.1, Modeled Concentrations (µg/m3) for the Salt Lake City, UT Nonattainment Area

The "Control Basket" inventory that is presented in Table 5.1 consists of a combination of SIP reductions
on point sources and new rules to be implemented that will affect smaller commercial and industrial
businesses. All of these changes are detailed in Chapter 6 - Control Measures. Summary tables of the
emission inventories that result from the Control Basket reductions are available in the TSD: Section 3
Baseline and Control Strategies.

5.9 Air Quality as of the Attainment Date
The attainment date for this moderate PM2.5 nonattainment area is December 31, 2015. The plan
provisions for moderate areas call, in Section 189(a)(1)(B), for either a demonstration that the plan will
provide for attainment by the applicable attainment date or a demonstration that attainment by such
date is impracticable.
As shown in the modeled attainment test, the emissions reductions achievable in 2015 allow for a
demonstration that the Logan, UT-ID nonattainment area can attain the 24-hour PM2.5 NAAQS by the
attainment date.
As discussed in Section 6.6, the emissions modeled in the “control basket” scenario reflect all RACM and
RACT measures achievable in practice by the statutory implementation date (December 14, 2014).

2010
Observed Business-As-Usual Control Basket
Logan 41 37 34
Franklin 39 34 32
2015
Logan – Page 44
Chapter 6 – CONTROL MEASURES

6.1 Introduction
Attaining the 2006, 24-hour NAAQS for PM2.5 will require emission controls from directly emitted PM2.5
as well as PM2.5 precursors (SO2, NOx and VOC). It will involve emission sources from each of the four
sectors identified in the discussion on emission inventories (stationary point sources, area sources, on-
road mobile sources and off-road mobile sources). Furthermore, it will entail control measures of three
basic types: existing measures, measures imposed through this SIP, and additional measures requiring
additional development before they are ready for implementation.
This chapter summarizes the overall control strategy for the plan. Additional detail concerning
individual emission control measures, including the emissions reductions to be expected, is contained in
the Technical Support Document.

6.2 Utah Stakeholder Workgroup Efforts
In response to increasing interest in Utah’s air quality problems and the need for greater participation in
reducing air emissions, the Utah Division of Air Quality (DAQ) created a significant and meaningful role
for public participation in the PM2.5 SIP development process. The public involvement process was
driven by a need for transparency and inclusivity of public health and business interests impacted by air
quality issues.
DAQ’s measures of success for the public involvement process were:
 Buy-in from public, stakeholders, and elected officials,
 SIP recommendations that are championed and implemented, and
 Close working relationship with partner organizations to deliver a unified message.
Measures of success for participants were:
 Having a say in plans that impacted their communities,
 Access to information and time to understand issues and provide input,
 Access to DAQ staff and the SIP development process,
 Meaningful participation in the process, and
 Transparency in the process.
Logan – Page 45
Public participation centered on creating workgroups with members from each county within the PM2.5
nonattainment area—Box Elder, Cache, Davis, Salt Lake, Tooele, Utah, and Weber. More than 100
people from agriculture, academia, environmental groups, state and local elected officials, industry, and
the public volunteered to participate. Their participation ensured that the SIP development process
would have grassroots-level input about strategies and their impacts on a countywide level.
Workgroup members were engaged in four rounds of meetings created to provide and gather
information. After providing a baseline level of knowledge during Meeting One, draft emissions
reductions were discussed during Meetings Two and Three, each followed by a survey to capture new
ideas and feedback. Responses from the survey, and other feedback received during the process, were
used to refine emissions inventories, in some cases significantly, refine mitigation strategies, provide
new strategies, and provide ideas for implementation. Meeting Four was an opportunity for workgroup
members to introduce the SIP package to the public and talk about the development process before one
of several public comment hearings held in the nonattainment counties.
The public participation process was not without challenges. One of the most difficult was providing
information that could get a diverse group of stakeholders to understand very complex and technical air
quality and emissions reductions issues. Despite the challenges, the process was successful and
contributed to a well-rounded and well-vetted SIP package.

6.3 Identification of Measures
In considering the suite of control measures that could be implemented as part of this plan several
important principles were applied to expedite the analysis.
Filter data shows that secondary particulate is the portion of mass most responsible for exceedances of
the standard on episode days, and specifically shows that ammonium nitrate is the single largest
component of that material. In addition, it shows that organic carbon represents the bulk of primary
PM2.5.
Priority was given to those source categories or pollutants responsible for relatively larger percentages
of the emissions leading to exceedances of the PM2.5 NAAQS. The emissions inventory compiled to
represent base-year conditions was useful in identifying the contributors to these emissions, particularly
in their relation to the formation of ammonium nitrate.
At the same time, the air quality modeling shed light on the sensitivity of the airshed in its response to
changes in different pollutants. VOC was immediately identified as a significant contributor to elevated
PM2.5 concentrations, and proved to be more limiting in the overall atmospheric chemistry than NOx.
This pointed the search for viable control strategies toward VOC emissions, and somewhat away from
NOx. It also became apparent that directly emitted PM2.5, while a relatively small portion of the overall
filter mass, is independent of the non-linear chemical transformation to particulate matter. Therefore,
any reduction in PM2.5 emissions will directly improve future PM2.5 concentrations, and like VOC, made
Logan – Page 46
these emissions an attractive target for potential control measures. . Subsequent modeling revealed
that, as time progressed and the relative concentrations of NOx and VOC changed, controlling for NOx
would yield more benefit in terms of controlling PM2.5. Ammonia is also prominent in chemical reactions
that produce secondary PM2.5, but it occurs in such abundance that PM2.5 concentrations are sensitive
only to unachievable reductions in ammonia.

6.4 Existing Control Measures
Since about 1970 there have been regulations at both state and federal levels to mitigate air
contaminants. It follows that the estimates of emissions used in modeled attainment demonstration for
this Plan take into account the effectiveness of existing control measures. These measures affect not
only the levels of current emissions, but some continue to affect emissions trends as well.
An example of the former would be the effectiveness of an add-on control device at a stationary point
source. It is presently effective in controlling emissions, and will continue to be that effective five years
from now.
An example of the latter would be a federal rule that affects the manufacture of engines. The engines
already sold into the airshed are effective in reducing emissions, but the number of these engines
replacing older, higher emitting engines is increasing. Therefore, a rule such as this also affects the
trend of emissions for that source category in a positive way.
The effectiveness of any control measure that was in place, and enforceable, at the time this Plan was
written has been accounted for in the tabulation of baseline emissions and projected emissions.
The following paragraphs discuss some of the more important control strategies that are already in
place for the four basic sectors of the emissions inventory.
Stationary Point Sources:
Utah’s permitting rules require a review of new and modified major stationary sources in nonattainment
areas, as is required by Section 173 of the Clean Air Act. Beyond that however, even minor sources and
minor modifications to major sources planning to locate anywhere in the state are required to undergo
a new source review analysis and receive an approval order to construct. Part of this review is an
analysis to ensure the application of Best Available Control Technology (BACT). This requirement is
ongoing and ensures that Utah’s industry is well controlled.
Any of the source-specific emission controls or operating practices that has been required as a result of
the forgoing has been reflected in the baseline emissions calculated for the large stationary sources, and
therefore evaluated in the modeled attainment demonstration.
Logan – Page 47
Area sources:
Stage 1 vapor control was introduced in Salt Lake and Davis Counties as part of the 1981 ozone SIP. This
is a method of collecting VOC vapors, as underground gasoline storage tanks are filled at gas stations,
and returning those vapors to a facility where they are collected and recycled. Since that time it has
been extended to include the entire state.
Energy Efficiency
EPA recognizes the benefits of including energy efficiency programs in SIP’s as a low cost means of
reducing emissions. Two established energy efficiency programs that result in direct emission reductions
within the Wasatch Front are already in place.
Questar Gas ThermWise Rebate Programs
Questar started the ThermWise Rebate Programs on January 1, 2007 as a way to promote the use of
energy-efficient appliances and practices among its customers. The ThermWise Programs offer rebates
to help offset the initial cost of energy-efficient appliances and weatherization. There are also rebates
available for energy efficient new construction. The cost of rebates is built into the Questar gas rate. The
rebates are vetted by the Utah Public Service Commission's strict "cost-effectiveness" tests. To pass
these tests, Questar must prove that the energy cost savings produced by the ThermWise Programs
exceeds the cost of the rebates. There is no scheduled end to the ThermWise Programs. According to
the Questar program information, the program will remain in place as long as rebates remain cost-
effective.
UDAQ calculates area source emissions for natural gas by multiplying emission factors against actual and
projected yearly gas usage data submitted by Questar. In this way, actual realized program reductions
are expressed in the past year (baseline) emission inventory. Future investment in energy efficiency is
not captured in our projected future gas usage. Continuance of this program will result in future gas
emissions that are lower than projected.
Weatherization Assistance Program
The Weatherization Assistance Program helps low-income individuals and families reduce energy costs.
Individuals, families, the elderly and the disabled who are making no more than 200 percent of the
current federal poverty income level are eligible for help. However, priority is given to the elderly and
disabled, households with high-energy consumption, emergency situations and homes with preschool-
age children.
The Utah Division of Housing and Community Development administer the program statewide through
eight government and nonprofit agencies. Benefits are provided in the form of noncash grants to eligible
households to make energy-efficiency improvements to those homes.
The energy efficiency realized from this program is also imbedded within the gas usage data UDAQ
receives from Questar.
Logan – Page 48
On-road mobile sources:
The federal motor vehicle control program has been one of the most significant control strategies
affecting emissions that lead to PM2.5. Since 1968, the program has required newer vehicles to meet
ever more stringent emission standards for CO, NOx, and VOC. Tier 1 standards were established in the
early 1990s and were fully implemented by 1997. The Tier 1 emission standards can be found in Table
6.1. The EPA created a voluntary clean car program on January 7, 1998 (63 FR January 7, 1998), which
was called the National Low Emission Vehicle (NLEV) program. This program asked auto manufacturers
to commit to meet tailpipe standards for light duty vehicles that were more stringent than Tier 1
standards.

EPA Tier 1 Emission Standards for Passenger Cars and Light-Duty Trucks, FTP 75, g/mi
Category
100,000 miles/10 years1
THC NMHC CO
NOx2 NOx
PM3 diesel gasoline
Passenger cars - 0.31 4.2 1.25 0.6 0.1
LLDT, LVW <3,750 lbs 0.8 0.31 4.2 1.25 0.6 0.1
LLDT, LVW >3,750 lbs 0.8 0.4 5.5 0.97 0.97 0.1
HLDT, ALVW <5,750 lbs 0.8 0.46 6.4 0.98 0.98 0.1
HLDT, ALVW > 5,750 lbs 0.8 0.56 7.3 1.53 1.53 0.12
1 - Useful life 120,000 miles/11 years for all HLDT standards and for THC standards for LDT
2 - More relaxed NOx limits for diesels applicable to vehicles through 2003 model year
3 - PM standards applicable to diesel vehicles only

Abbreviations:
LVW - loaded vehicle weight (curb weight + 300 lbs)
ALVW - adjusted LVW (the numerical average of the curb weight and the GVWR)
LLDT - light light-duty truck (below 6,000 lbs GVWR)
HLDT - heavy light-duty truck (above 6,000 lbs GVWR)

Table 6.1, Tier 1 Emission Standards

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Shortly thereafter, EPA promulgated the Tier 2 program. This program went into effect on April 10,
2000 (65 FR 6698 February 10, 2000) and was phased in between 2004 and 2008. Tier 2 introduced
more stringent numerical emission limits compared to the previous program (Tier 1). Tier 2 set a single
set of standards for all light duty vehicles. The Tier 2 emission standards are structured into 8
permanent and 3 temporary certification levels of different stringency, called “certification bins”, and an
average fleet standard for NOx emissions. Vehicle manufacturers have a choice to certify particular
vehicles to any of the available bins. The program also required refiners to reduce gasoline sulfur levels
nationwide, which was fully implemented in 2007. The sulfur levels need to be reduced so that Tier 2
vehicles could run correctly and maintain their effectiveness. The EPA estimated that the Tier 2 program
will reduce oxides of nitrogen emissions by at least 2,220,000 tons per year nationwide in 20201. Tier 2
has also contributed in reducing VOC and direct PM emissions from light duty vehicles. Tier 2 standards
are summarized in Table 6.2 below.

Tier 2 Emission Standards, FTP 75, g/mi
Bin#
Full Useful Life
NMOG* CO NOx† PM HCHO
Temporary Bins
11 MDPVc 0.28 7.3 0.9 0.12 0.032
10a,b,d 0.156 (0.230) 4.2 (6.4) 0.6 0.08 0.018 (0.027)
9a,b,e 0.090 (0.180) 4.2 0.3 0.06 0.018
Permanent Bins
8b 0.125 (0.156) 4.2 0.2 0.02 0.018
7 0.09 4.2 0.15 0.02 0.018
6 0.09 4.2 0.1 0.01 0.018
5 0.09 4.2 0.07 0.01 0.018
4 0.07 2.1 0.04 0.01 0.011
3 0.055 2.1 0.03 0.01 0.011
2 0.01 2.1 0.02 0.01 0.004
1 0 0 0 0 0
* for diesel fueled vehicle, NMOG (non-methane organic gases) means NMHC (non-methane hydrocarbons)
† average manufacturer fleet NOx standard is 0.07 g/mi for Tier 2 vehicles

1 65 FR 6698 February 10, 2000
Logan – Page 50
a - Bin deleted at end of 2006 model year (2008 for HLDTs)
b - The higher temporary NMOG, CO and HCHO values apply only to HLDTs and MDPVs and expire after 2008
c - An additional temporary bin restricted to MDPVs, expires after model year 2008
d - Optional temporary NMOG standard of 0.280 g/mi (full useful life) applies for qualifying LDT4s and MDPVs only
e - Optional temporary NMOG standard of 0.130 g/mi (full useful life) applies for qualifying LDT2s only
Abbreviations:
LDT2 – light duty trucks 2 (0-6,000 lbs. GVWR, 3,751-5,750 lbs. LVW)
LDT4 – light duty trucks 4 (6,001-8,500 lbs. GVWR, 5,751 lbs. and greater ALVW)
MDPV – medium duty passenger vehicle
HLDT - heavy light duty truck (above 6,000 lbs GVWR)

Table 6.2, Tier 2 Emission Standards

In addition to the benefits from Tier 2 in the current emissions inventories, the emission projections for
2015 in this SIP continue to reflect significant improvements in both VOC and NOx as older vehicles are
replaced with Tier 2 vehicles. This trend may be seen in the inventory projections for on-road mobile
sources despite the growth in vehicles and vehicle miles traveled that are factored into the same
projections.
Additional on-road mobile source emissions improvement stemmed from federal regulations for heavy-
duty diesel vehicles. The Highway Diesel Rule, which aimed at reducing pollution from heavy-duty diesel
highway vehicles, was finalized in January 2001. Under the rule, beginning in 2007 (with a phase-in
through 2010) heavy-duty diesel highway vehicle emissions were required to be reduced by as much 90
percent with a goal of complete fleet replacement by 2030. In order to enable the updated emission-
reduction technologies necessitated by the rule, beginning in 2006 (with a phase-in through 2009)
refiners were required to begin producing cleaner-burning ultra-low sulfur diesel fuel. Specifically, the
rule required a 97 percent reduction in sulfur content from 500 parts per million (ppm) to 15 ppm. The
overall nationwide effect of the rule is estimated to be equivalent to removing the pollution from over
90 percent of trucks and buses when the fleet turnover is completed in 2030.

Logan – Page 51
Off-road mobile sources:
Several significant regulatory programs enacted at the federal level will affect emissions from non-road
mobile emission sources. This category of emitters includes airplanes, locomotives, hand-held engines,
and larger portable engines such as generators and construction equipment. The effectiveness of these
controls has been incorporated into the “NONROAD” model UDAQ uses to compile the inventory
information for this source category. Thus, the controls have already been factored into the projection
inventories used in the modeled attainment demonstration.
EPA rules for non-road equipment and vehicles are grouped into various "tiers" in a manner similar to
the tiers established for on-road motor vehicles. To date, non-road rules have been promulgated for
Tiers 0 through IV, where the oldest equipment group is designated "Tier 0" and the newest equipment,
some of which has yet to be manufactured, falls into "Tier IV." Of note are the following:
Locomotives
Locomotive engine regulation began with Tier 0 standards promulgated in 1998, which apply to model
year 2001 engines.
In addition, because of the very long lifetimes of these engines, often up to forty years, Tier 0 standards
include remanufacturing standards, which apply to locomotive engines of model years 1973 through
2001.
Subsequent tier standards for line-haul locomotives apply as follows:
Tier Applicable Model Years
Tier I 2002 - 2004
Tier II 2005 - 2011
Tier III 2012 - 2014
Tier IV 2015 - newer

Yard or "switch" locomotives are regulated under different standards than line-haul.
Lastly, EPA has promulgated remanufacturing standards for Tier I and 2 locomotive engines to date.
Large Engines
Large non-road engines are usually diesel-powered but include some gasoline-powered equipment.
Large land-based diesel equipment (> 37 kw or 50 hp) used in agricultural, construction and industrial
applications are regulated under Tier I rules, which apply to model years 1996 through 2000.
Subsequent Tier II through IV rules apply to newer model-year equipment.
Logan – Page 52
Some large non-road engines are gasoline-powered (spark-ignition). These include equipment such as
forklifts, some airport ground support equipment, recreational equipment such as ATVs, motorcycles
and snowmobiles. These are regulated under various tiers in a manner similar to diesel equipment.
Small Engines
Small engines are generally gasoline-powered (spark-ignition). Equipment includes handheld and larger
non-handheld types. Handheld equipment includes lawn and garden power tools such as shrub
trimmers, saws and dust blowers. Non-handheld equipment includes equipment such as lawnmowers
and lawn tractors. From an emissions standpoint, smaller engine size is offset by the large number of
pieces of equipment in use by households and commercial establishments. This equipment is regulated
under a tiered structure as well.
Emissions Benefit
Each major revision of the non-road tier standards results in a large reduction in carbon monoxide,
hydrocarbons, nitrogen oxides and particulate matter.
For example, the Non-road Diesel Tier II and III Rule, which regulates model-year 2001 through 2008
diesel equipment (> 37 kw or 50 hp) is estimated by EPA, in its Regulatory Announcement for this rule
dated August 1998, to decrease NOx emissions by a million tons per year by 2010, the equivalent of
taking 35 million passenger cars off the road.
EPA further estimates, in its Regulatory Announcement dated May 2004, that the Tier IV non-road diesel
rule is expected to decrease exhaust emissions per piece of equipment by over 90 percent compared to
older equipment.
Low-Sulfur Diesel
Non-road diesel equipment is required to operate on diesel fuel with a sulfur content of no greater than
500 ppm beginning June 1, 2007.
Beginning June 1, 2010, non-road diesel equipment must operate on "ultra-low" sulfur diesel with a
sulfur content of no more than 15 ppm.
Locomotives and certain marine engines must operate on ultra-low sulfur diesel by June 1, 2012.

6.5 SIP Controls
Beyond the benefits attributable to the controls already in place, there are new controls identified by
this SIP that provide additional benefit toward reaching attainment. A summary of the plan strategy is
presented here for each of the emission source sectors.
Overall, within the Logan, UT-ID nonattainment area, the strategy to reduce emissions results in 2.66
tons per day of combined PM2.5, SO2, NOx and VOC in 2015.
Logan – Page 53

6.6 Reasonably Available Control Measures (RACM/RACT)
Section 172 of the CAA requires that each attainment plan “provide for the implementation of all
reasonably available control measures (RACM) as expeditiously as practicable (including such reductions
in emissions from existing sources in the area as may be obtained through the adoption, at a minimum,
of reasonably available control technology (RACT)), and shall provide for attainment of the NAAQS.”
Now that the Courts have determined that Subpart 4 applies to PM2.5 nonattainment areas, it is also
instructive to consider paragraph 189(a)(1)(C), which requires that “provisions to assure that reasonably
available control measures … shall be implemented no later than … 4 years after designation in the case
of an area classified as moderate after the date of the enactment of the Clean Air Act Amendments of
1990.” All three of Utah’s nonattainment areas for PM2.5 were designated so on December 14, 2009.
Hence, December 14, 2013 was the date by which all RACM was to have been implemented.
EPA interprets RACM as referring to measures of any type that may be applicable to a wide range of
sources (mobile, area, or stationary), whereas RACT refers to measures applicable to stationary sources.
Thus, RACT is a type of RACM specifically designed for stationary sources. For Both RACT and RACM
Potential control measures must be shown to be both technologically and economically feasible.
Pollutants to be addressed by States in establishing RACT and RACM limits in their PM2.5 attainment
plans will include primary PM2.5 as well as precursors to PM2.5. For the control strategy in this plan,
those pollutants include SO2, NOx and VOC.
In general, the combined approach to RACT and RACM includes the following steps: 1) identification of
potential measures that are reasonable, 2) modeling to test the control strategy, and 3) selection of
RACT and RACM.
This basic process was applied to each of the four basic sectors of the emissions inventory:
Stationary Point sources:
Reasonably Available Control Technology – As stated above, RACT refers to measures applicable to
stationary sources. Thus, RACT is a type of RACM specifically designed for stationary sources.
Section 172 does not include any specific applicability thresholds to identify the size of sources that
States and EPA must consider in the RACT and RACM analysis. In developing the emissions inventories
underlying the SIP, the criteria of 40 CFR 51 for air emissions reporting requirements was used to
establish a 100 ton per year threshold for identifying a sub-group of stationary point sources that would
be evaluated individually. The cut-off was applied to either a sources reported emissions for 2008 or for
its potential to emit in a given year. The rest of the point sources were assumed to represent a portion
of the overall area source inventory.
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Sources meeting the criteria described above were individually evaluated to determine whether their
operations would be consistent with RACT.
For the Logan, UT-ID nonattainment area, there are no point sources with the potential to emit 100 tons
per year of PM2.5 or any PM2.5 plan precursor.
Additional information regarding the RACT analysis in the nonattainment area may be found in the
Technical Support Document.
New Source Review / Banked Emission Reduction Credits – Under Utah’s new source review rules in
R307-403-8, banking of emission reduction credits (ERCs) is permitted to the fullest extent allowed by
applicable Federal Law as identified in 40 CFR 51, Appendix S, among other documents. Under Appendix
S, Section IV.C.5, a permitting authority may allow banked ERCs to be used under the preconstruction
review program (R307-403) as long as the banked ERCs are identified and accounted for in the SIP
control strategy. In the past, Utah has accounted for existing banked ERCs in SIP control strategies,
ensuring that a pool of ERCs was available for new or modified sources in nonattainment areas. For the
PM2.5 SIP, however, it was not possible to include banked ERCs in the attainment demonstration. The
PM2.5 SIP adopted by the Air Quality Board on December 5, 2012 did not include banked PM2.5 or PM2.5
precursor ERCs in the attainment demonstration1, and therefore under R307-403-8 any ERCs that were
banked prior to December 5, 2012 may not be used as PM2.5 major source or major modification
emission offsets for PM2.5 nonattainment areas. Any ERCs generated after December 5, 2012 for PM2.5
or PM2.5 precursors would have been accounted for in this PM2.5 attainment demonstration and are
eligible to be used as emission offsets for PM2.5 or PM2.5 precursors. DAQ has established a new registry
for PM2.5 ERCs generated after December 5, 2012 to ensure that qualifying ERCs are tracked.
Area sources:
The area source RACM analysis consisted of a thorough review of the entire area source inventory for
anthropocentrically derived direct PM2.5 and precursors constituents. There was no emission threshold
level established in the review process; instead, the analysis centered on whether reasonable control
measures are available for a given source category. The following table identifies these categories as
well as the pollutant(s) likely to be controlled, and provides some remarks as to whether a control
strategy was ultimately pursued. In considering what source categories might be considered, Utah
made use of EPA recommendations included in Control Techniques Guideline Documents (CTG’s), as
well as control strategies from other states. DAQ evaluated each strategy for technical feasibility as part
of the RACM analysis. The screening column in the table identifies whether or not a strategy was
retained for rulemaking or screened out for impracticability.

1 Note that, because no part of Cache County had ever before been designated as a nonattainment area for any
pollutant, there were no ERCs in the registry to even be considered in the modeled demonstration belonging to
the SIP revision adopted by the Utah Air Quality Board on December 5, 2012. Furthermore, no ERCs were created
in the Logan, UT-ID nonattainment area between December 5, 2012 and the effective date of this plan revision
(prepared to also address the requirements of Subpart 4). Hence, no banked emission credits were included in this
demonstration either.
Logan – Page 55

Table 6.3 Area Source Strategy Screening
Strategy Constituent(s) Screening
Status Remarks
1. Repeal current surface coating rule, R307-
340. Replace this rule with individual rules
for each category. New rules include PM2.5
nonattainment areas. New rules update
applicability and control limits to most current
CTG. Current rule includes, paper, fabric
and vinyl, metal furniture, large appliance,
magnet wire, flat wood, miscellaneous metal
parts and graphic arts.
VOC Retained R307-340 previously applied to Davis and
Salt Lake counties. R307-340 was
withdrawn and re-enacted as separate rules
for each existing category. The new rules
were expanded to nonattainment areas and
updated to the most current RACT based
limit(s).
2. New separate surface coating rules for following sources:
a. Aerospace
b. High performance
c. Architectural
d. Marine
e. Sheet, strip & coil
f. Traffic markings
g. Plastic parts

VOC See Remarks Column Aerospace – retained
High performance – not retained, regulated
under Federal Insecticide, Fungicide, and
Rodenticide Act (FIFRA)

Architectural – initially nor retained, further
research indicated that adopting the Ozone
Transport Commission model rule is
feasible.
Marine – not retained, only 1.2 tpy

Sheet, strip & coil – retained

Traffic markings – not retained, regulated
under FIFRA

Plastic parts - retained
3. Agricultural practices using Natural
Resources Conservation Service (NRSC) practice standards
VOC, PM2.5,
ammonia
Not Retained The NRCS has already enrolled most
farmers in the erodible regions in their program thereby negating the need for
rulemaking
4. Consumer products rule regulating VOC
content
VOC Retained
5. Adhesives and sealant rule VOC Retained
6. Expand current solvent degreasing rule
R307-335 to PM2.5 nonattainment areas and
add a new section on industrial solvent
cleaning
VOC Retained
7. Automobile refinishing rule VOC Retained
8. Expand wood furniture manufacturing rule to
PM2.5 nonattainment areas. Update to most
current CTG.
VOC Retained
9. Lower the no burn cut point for residential
use of solid fuel burning devices. Require
new sale of EPA certified stoves/fireplaces.
Prohibit the sale/resale of noncertified stoves
in nonattainment areas.
VOC, PM2.5,
NOx, SOx,
ammonia
Retained
10. Ban new sales of stick type outdoor wood
boilers in nonattainment areas.
VOC, PM2.5,
NOx, SOx,
ammonia
Retained
11. Industrial bakery rule VOC Initially
Retained
Screened out after analysis of public
comment, cost benefit analysis does not
support rulemaking, high cost-low VOC
reduction
12. Restaurant charbroiler emission control:
- Chain-driven
-Underfire
VOC, PM2.5 Chain-driven
Retained

No reasonable control measures available
at this time for underfire charbroiling
Logan – Page 56
Strategy Constituent(s) Screening
Status Remarks
Underfire-Not
Retained
13. Appliance pilot light phase out VOC, PM2.5,
NOx, SOx,
ammonia
Retained
14. Expand current fugitive dust rule, R307-309
to PM2.5 nonattainment areas. Require
BMP’s for dust plans.
PM2.5 Retained
15. Amend fugitive dust rule to include cattle
feed lot
PM2.5 Not Retained Sizeable feed lots are not located in
nonattainment areas
16. Ultra-low NOx burners in commercial,
industrial, and institutional boilers
NOx Tentatively
Retained for
Future
Consideration
Developing technology not readily available
at this time
17. Ultra-low NOx burners in water heaters NOx Tentatively
Retained for
Future
Consideration
High cost and availability concerns
18. Manure management VOC,
ammonia
Not Retained NRCS best management practices already
encourages manure management. Limited
viable options during winter months and
treatment options are costly with low control
efficiency that would not yield significant
ammonia reduction in an ammonia rich
inventory
19. Ban testing of back-up generators on red-
alert days
VOC, PM2.5,
NOx, SOx
Initially
Retained
Screened out after review of public
comment, rule implementation was more
complicated than anticipated, generators
cannot be easily re-programmed
20. Prohibit use of cutback asphalt VOC Not Retained Cities and highway administration personnel
need stockpile for winter time road repair.
Very small inventory.
21. Control limits on aggregate processing
operations and asphalt manufacturing
PM2.5, NOx,
SOx
Retained
22. R307-307 Road Salt and Sanding PM Retained Expand current rule to nonattainment areas

EPA published CTGs and Alternative Control Techniques documents (ACTs) for VOCs for a host of
emission sources. The CTGs are used to presumptively define VOC RACT. The VOC ACTs describe
available control techniques and their cost effectiveness, but do not define presumptive RACT levels as
the CTGs do. Therefore, CTG’s are given highest priority in rule development.
Where a CTG does not exist for an emission source or where a CTG is so dated that it no longer
represents current industry practice, UDAQ considered rules from other states as reference sources.
Additional reference sources include the Ozone Transport Commission (OTC) and the Northeast States
for Coordinated Air Use Management.
As noted above, many CTGs were previously adopted into Utah’s air quality rules to address ozone
nonattainment in Salt Lake and Davis Counties. In conducting this evaluation, consideration was given
to whether an expansion of applicability for an existing CTG into additional counties would provide a
benefit for PM2.5, and whether a strengthening of existing CTG requirements in Salt Lake and Davis
Logan – Page 57
Counties would result in an incremental benefit that was economically feasible. Furthermore, EPA has
updated some of its existing CTGs and added some new ones to the list.
As part of this SIP, Utah has identified relevant source categories covered by CTGs, and promulgated
rules based on the CTGs for reducing emissions from these categories. These rules apply to the
following source categories:
 Control of Volatile Organic Emissions from Surface Coating of Cans, Coils, Paper, Fabrics,
Automobiles, and Light-Duty Trucks
 Control of Volatile Organic Emissions from Solvent Metal Cleaning
 Control of Volatile Organic Emissions from Surface Coating of Insulation of Magnet Wire
 Control of Volatile Organic Emissions from Graphic Arts
 Control of Volatile Organic Compound Emissions from Wood Furniture Manufacturing
Operations
 Control Techniques Guidelines for Industrial Cleaning Solvents
 Control Techniques Guidelines for Flat Wood Paneling Coatings
 Control Techniques Guidelines for Paper, Film, and Foil Coatings
 Control Techniques Guidelines for Large Appliance Coatings
 Control Techniques Guidelines for Metal Furniture Coatings
 Control Techniques Guidelines for Miscellaneous Metal and Plastic Parts Coatings
 Control of Volatile Organic Emissions from Coating Operations at Aerospace Manufacturing and
Rework Operations

While most VOC sources are addressed by CTGs, the remaining emission sources must be evaluated by
engineering analysis, including an evaluation of rulings by other states including model rules developed
by the Ozone Transport Commission. These include VOCs from autobody refinishing, restaurant
charbroiling, and phasing out appliance pilot lights.
CTGs for PM2.5 emissions sources do not exist. RACT for PM2.5 has been established through information
from varied EPA and other state SIP sources. A useful source of data is the AP 42 Compilation of Air
Pollutant Emission Factors, first published by the US Public Health Service in 1968. In 1972, it was
revised and issued as the second edition by the EPA. The emission factor/control information was
applied to fugitive dust and mining strategies.

Logan – Page 58
Table 6.4 shows the effectiveness of the area source SIP control strategy for the Logan, UT-ID
nonattainment area by indicating the quantities of emissions eliminated from the inventory in 2015.
Most of these rules became effective January 1, 2014.

Table 6.4, Emissions Reductions from Area Source SIP Controls

NOX PM2.5 SOX VOC
Area Source Rules
R307-302, Solid fuel burning 64 533 11 666
R307-303, Commercial cooking 25 7
R307-309, Fugitive dust 58
R307-312, Aggregate processing operations 1
R307-335, Degreasing 379
R307-342, Adhesives & sealants 148
R307-343, Wood manufacturing 64
R307-344, Paper, film & foil coating 12
R307-345, Fabric & vinyl coating 686
R307-346, Metal furniture coating
R307-347, Large appliance coating
R307-348, Magnet wire coating
R307-349, Flat wood panel coating 36
R307-350 Miscellaneous metal parts coating 26
machinery 7
other transportation 15
Special 1
R307-351, Graphic arts 298
R307-352, Metal containers
R307-353, Plastic coating 261
R307-354, Auto body refinishing 137
R307-355, Aerospace coatings 25
R307-356, Appliance pilot light 51 0 0 3
R307-357, Consumer products 255
R307-361, Architectural coatings 563
Grand Totals 122 679 12 3,665
Logan, UT-ID Nonattainment Area
2015 lbs/day reduced
Logan – Page 59
On-road mobile sources:
A motor vehicle emission inspection and maintenance (I/M) program is a necessary control strategy for
Cache County to attain the PM2.5 NAAQS based on the modeling conducted by UDAQ. This analysis can
be found in the TSD.
Therefore, pursuant to Utah Code Annotated 41-6a-1642(1), Cache County officials successfully
implemented an I/M program on January 1, 2014. Cache County’s I/M program is comprised of a
decentralized, test and repair network and requires a biennial test for all vehicles 1969 and newer. The
program exempts vehicles less than six years old from an emission inspection. The details of the
program can be found in Section X Part F of the Utah SIP.
The emissions reductions associated with an I/M program for the year 2015 are 0.214 tons per day for
NOx and 0.212 tons per day for VOC.
Off-road mobile sources:
Beyond the existing controls reflected in the projection-year inventories and the air quality modeling
there are no emission controls that would apply to this source category.

Logan – Page 60
Chapter 7 – TRANSPORTATION CONFORMITY

7.1 Introduction
The federal Clean Air Act (CAA) requires that transportation plans and programs within the Logan, UT-ID
PM2.5 nonattainment area conform to the air quality plans in the region prior to being approved by the
Cache Metropolitan Planning Organization (CMPO). Demonstration of transportation conformity is a
condition to receive federal funding for transportation activities that are consistent with air quality goals
established in the Utah State Implementation Plan (SIP). Transportation conformity requirements are
intended to ensure that transportation activities do not interfere with air quality progress. Conformity
applies to on-road mobile source emissions from regional transportation plans (RTPs), transportation
improvement programs (TIPs), and projects funded or approved by the Federal Highway Administration
(FHWA) or the Federal Transit Administration (FTA) in areas that do not meet or previously have not met
the National Ambient Air Quality Standards (NAAQS) for ozone, carbon monoxide, particulate matter
less than 10 micrometers in diameter (PM10), particulate matter 2.5 micrometers in diameter or less
(PM2.5), or nitrogen dioxide.
The Safe, Accountable, Flexible, Efficient Transportation Equity Act – A Legacy for Users (SAFTEA-LU) and
section 176(c)(2)(A) of the CAA require that all regionally significant highway and transit projects in air
quality nonattainment areas be derived from a “conforming” transportation plan. Section 176(c) of the
CAA requires that transportation plans, programs, and projects conform to applicable air quality plans
before being approved by an MPO. Conformity to an implementation plan means that proposed
activities must not (1) cause or contribute to any new violation of any standard in any area, (2) increase
the frequency or severity of any existing violation of any standard in any area, or (3) delay timely
attainment of any standard or any required interim emission reductions or other milestones in any area.
The plans and programs produced by the transportation planning process of the CMPO are required to
conform to the on-road mobile source emissions budgets established in the SIP, or absent an approved
or adequate budget, required to meet the interim conformity test. Approval of conformity is
determined by the FHWA and FTA.

7.2 Consultation
The Interagency Consultation Team (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 responsibilities of the participating agencies. Members of the ICT workgroup collaborated
on a regular basis during the development of the PM2.5 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.
Logan – Page 61
ICT Workgroup Agencies
 Utah Division of Air Quality (UDAQ)
 Metropolitan Planning Organizations MPOs
 CMPO
 Wasatch Front Regional Council
 Mountainland Association of Governments
 Utah Department of Transportation (UDOT)
 Utah Local Public Transit Agencies
 Federal Highway Administration (FHWA)
 Federal Transit Administration (FTA)
 U.S. Environmental Protection Agency (EPA)

During the SIP development process the CMPO coordinated with the ICT workgroup and developed
PM2.5 SIP motor vehicle emissions inventories using the latest planning assumptions and tools for traffic
analysis and the EPA-approved Motor Vehicle Emission Simulator (MOVES2010) emissions model. Local
MOVES2010 modeling data inputs were cooperatively developed by the CMPO and the ICT workgroup
using EPA-recommended methods where applicable.

7.3 Regional Emission Analysis
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 nonattainment
area. On December 2009, EPA designated the only multistate nonattainment area in the State of Utah
by declaring portions of Cache County, Utah and Franklin County, Idaho (Cache Valley) as a PM2.5
nonattainment area. The Deadlines Rule (signed April 25, 2014) later classified this as a moderate PM2.5
nonattainment area. The responsible transportation planning organization for the Utah portion of the
multistate nonattainment area is the CMPO while the Idaho portion is covered by the Idaho Department
of Transportation.
As a condition to receive federal transportation funding, transportation plans, programs, and projects
are required to meet the criteria and procedures for demonstrating and assuring conformity to the
applicable implementation plan developed pursuant to Section 110 and Part D of the CAA. The criteria,
specified in 40 CFR 93.109, differ based on the action under review and the status of the
Logan – Page 62
implementation plan. The satisfaction of criteria and procedures, for implementation plans submitted
under Section 189(a)(1)(B)(i) of the CAA, which demonstrate attainment of the applicable NAAQS by the
applicable attainment date, are addressed generally in paragraph 93.109(b) of the conformity rule. For
such control strategy implementation plan revisions, the conformity test consists of either an interim
emissions test or a motor vehicle emissions budgets test.
Motor vehicle emissions budgets are defined in 40 CFR 93.101 as "that 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." Transportation plans, programs, and
projects are required to meet those emission budgets through strategies that increase the efficiency of
the transportation system and reduce motor vehicle use.
The interim conformity test requirements apply until either EPA has declared the motor vehicle
emissions budgets adequate for transportation conformity purposes or until EPA approves the budget in
the Federal Register.

7.4 Transportation Conformity PM2.5 Components
The transportation conformity requirements found in 40 CFR 93.102 require that the PM2.5 SIP include
motor vehicle emissions budgets for direct PM2.5 (elemental carbon, organic carbon, SO4, brake and tire
wear) and emissions of nitrogen oxide (NOx), a gaseous PM2.5 precursor.
Because UDAQ has identified volatile organic compounds (VOCs) as a PM2.5 precursor that significantly
impact PM2.5 concentrations, the SIP will also require a motor vehicle emissions budget for VOC.
The EPA conformity rule presumes that PM2.5 re-entrained road dust does not need to be included in the
interim conformity test or have an established motor vehicle emissions budget unless either the state or
EPA decides that re-entrained road dust emissions are a significant contributor to the PM2.5
nonattainment problem. The UDAQ conducted a re-entrained road dust study that concluded that PM2.5
re-entrained road dust emissions are negligible in the Utah portion of the Cache Valley PM2.5
nonattainment area. EPA Region 8 reviewed the study and concurred with the UDAQ’s findings.

7.5 Interim PM2.5 Conformity Test
The EPA interim conformity test, for the purposes of this plan revision, will require that NOx, VOC, and
direct PM2.5 (elemental carbon, organic carbon, SO4, brake and tire wear) emissions from RTPs, TIPs, and
projects funded or approved by the FHWA or the FTA not exceed 2008 levels.
Logan – Page 63
Interim emissions budget tests performed by the CMPO must include the whole multistate PM2.5
nonattainment area of Cache Valley, including emissions estimates from Franklin County, Idaho.
The Interim conformity test requirements apply until EPA has declared the motor vehicle emissions
budgets adequate for transportation conformity purposes or until EPA approves the budget in the
Federal Register.

7.6 Transportation Conformity PM2.5 Budgets
Cache County, Utah and Franklin County, Idaho have requested separate motor vehicle emissions
budgets for their respective areas; therefore, the budgets listed below only apply to the Cache MPO.
In this SIP, the State is establishing transportation conformity motor vehicle emission budgets (MVEB) in
the nonattainment portions of Cache County, Utah for 2015. Separate budgets are established for NOx,
VOC, and PM2.5 (elemental carbon, organic carbon, SO4, brake and tire wear).
The Transportation Conformity PM2.5 budgets emissions estimates for the mobile sources are calculated
from the EPA approved Motor Vehicle Emission Simulator Model (EPA MOVES 2010a).
Cache MPO Transportation Conformity Budgets

Direct PM2.5 (tpd) NOx (tpd) VOC (tpd)
2015 0.32 4.49 3.23

Table 7.1, Emissions Budgets for Transportation Conformity Purposes (EPA MOVES 2010a). Note: PM2.5 budget
only includes tire and brake wear, sulfate, elemental and organic carbon and does not include road dust. VOC
emissions do not include refueling spillage and displacement vapor loss. Budgets are rounded to the nearest
hundredth ton.

Per section 93.124 of the conformity regulations, for transportation conformity analyses using these
budgets in analysis years beyond 2015, a trading mechanism is established to allow future increases in
on-road direct PM2.5 emissions to be offset by future decreases in plan precursor emissions from on-
road mobile sources at appropriate ratios established by the air quality model. Future increases in on-
road direct PM2.5 emissions may be offset with future decreases in NOx emissions from on-road mobile
sources at a NOx to PM2.5 ratio of 13.66 to 1 and/or future decreases in VOC emissions from on-road
mobile sources at a VOC to PM2.5 ratio of 22.84 to 1. This trading mechanism will only be used if needed
for conformity analyses for years after 2015. To ensure that the trading mechanism does not impact the
ability to meet the NOx or VOC budgets, the NOx emission reductions available to supplement the direct
PM2.5 budget shall only be those remaining after the 2015 NOx budget has been met, and the VOC
emissions reductions available to supplement the direct PM2.5 budget shall only be those remaining after
the 2015 VOC budget has been met. Clear documentation of the calculations used in the trading should
be included in the conformity analysis.
Logan – Page 64
Chapter 8 – REASONABLE FURTHER PROGRESS

8.1 Introduction
Clean Air Act Section 172(c)(2) requires that plans for nonattainment areas “shall require reasonable
further progress (RFP).” The definition of RFP is given in Section 171 of the CAA. It means “such annual
incremental reductions in emissions of the relevant air pollutant as are required by this part or may
reasonably be required by the Administrator for the purpose of ensuring attainment of the applicable
national ambient air quality standard by the applicable date.”
In general terms, the goal of these RFP requirements is for areas to achieve generally linear progress
toward attainment, as opposed to deferring implementation of all measures, where possible, until the
end.
The pollutants to be addressed in the RFP plan are those pollutants that are identified for purposes of
control measures in the attainment plan: PM2.5, SO2, NOx, and VOC.
8.2 Moderate Area Planning Requirements
Within the context of the moderate area planning requirements given in Subparts 1 and 4 of the CAA,
RFP must be considered in light of the attainment date as well as the date by which all RACT and RACM
must be implemented. The attainment date for all three of Utah’s moderate PM2.5 nonattainment areas
was established in EPA’s Deadlines Rule. That date is December 31, 2015. The deadline for
implementation of all RACT and RACM is described in paragraph 189(a)(1)(C) as four years from the date
these areas were designated nonattainment. That date for implementation of RACM was thus
December 14, 2013.
There are other moderate area planning requirements in Subpart 4 that relate to the showing of RFP.
Paragraph 189(a)(1)(B) requires “either (i) a demonstration (including air quality modeling) that the plan
will provide for attainment by the applicable attainment date; or (ii) a demonstration that attainment by
such date is impracticable.”
This plan demonstrates the former; that with the implementation of all reasonably available controls,
the area will attain the 2006, 24-hour standard for PM2.5 by December 31, 2015.
For plan revisions showing attainment, paragraph 189(c) requires the inclusion of “quantitative
milestones which are to be achieved every three years until the area is redesignated attainment and
which demonstrate reasonable further progress … toward attainment by the applicable date.”

Logan – Page 65
8.3 RFP for the Logan, UT-ID Nonattainment Area
The attainment demonstration for the Logan, UT-ID PM2.5 nonattainment area shows that the 2006, 24-
hr NAAQS can be achieved by the attainment date of December 31, 2015. Essentially, the attainment
demonstration in the SIP may also be considered to demonstrate that the area is achieving RFP
Past Guidance on RFP, for showing generally linear progress towards attainment by the applicable
attainment date, has described a straight line with a downward trend, ending at the attainment date
and representing, there, a level of emissions that is consistent with attainment of the applicable NAAQS.
In this plan, the “reductions in emissions of the relevant air pollutant as are required by this part” have
been determined through the application of all RACM and RACT measures. The emissions reductions
associated with these control measures were factored into an inventory for 2015 that was assessed
using air quality modeling. The air quality modeling demonstrated that these reductions in emissions
would be sufficient to demonstrate attainment of the applicable standard by the applicable attainment
date.
It is also necessary to define a period of time over which the RFP determination will be made.
The starting point for evaluating RFP should be the baseline year used in the modeling analysis. This is a
year (2010) selected to coincide with the period used to establish the monitored design value for the
modeling analysis; a period in which the area is violating the applicable NAAQS.
Thus, the magnitude of emissions reductions should be evaluated over a period spanning from 2010
through 2015.
Quantitatively, the following assessment of emissions and incremental emissions reductions in Table 8.1
will show that RFP is met using the criteria discussed above:

Logan – Page 66

Table 8.1, Reasonable Further Progress in the Logan, UT-ID nonattainment area

In addition to the emissions totals, the table also includes the 2010 baseline design value for the
controlling monitor in the nonattainment area (Logan) and the predicted PM2.5 concentration in 2015.
These concentrations are presented as another metric to establish progress toward meeting the 24-hour
standard.
Control Measures
The inventory for 2015 “with growth and controls” reflects the implementation of all the reasonably
available control measures and reasonably available control technologies identified in this plan, as well
as all pre-existing control measures. As such, this inventory takes into account all controls that “may
reasonably be required by the Administrator.”
For a complete discussion of RACM & RACT, and the control measures factored into the modeled
demonstration for 2015, see Chapter 6 of the Plan.

Reasonable Further Progress
Logan, UT-ID PM2.5 Nonattainment Area
*Emissions / Year 2010 2015 Difference RFP
Annualized
Difference
PM2.5 1.3 0.8 0.5 0.1
NOx 9.3 6.9 2.4 0.5
SO2 0.3 0.3 0.0 0.0
VOC 12.1 8.9 3.2 0.6
Plan precursors 21.7 16.1 5.6 1.1
Total 23.0 16.9 6.1 1.2
**Concentration (ug/m3)41 34 7.1 1.4
* Emissions are presented in tons per average winter day
**Value for 2010 is Baseline design value for the Logan monitor
projected with growth and
controls
Logan – Page 67
8.4 Milestones for the Logan, UT-ID Nonattainment Area
For plan revisions showing attainment, the Act requires quantitative milestones, to be achieved every
three years, which demonstrate reasonable further progress toward attainment by the applicable date.
Under section 189(c), the State is required to submit a SIP revision if it fails to submit the quantitative
milestone demonstration or if EPA determines that the milestone was not met.
These milestones are addressed in EPA’s General Preamble (see Section 2.2 of this plan), which says that
under the milestone requirement, the States must demonstrate to EPA that the SIP measures are being
implemented and the milestones have been met.
The preamble notes that section 189(c) does not articulate the starting point for counting the 3-year
period, and offers that it is reasonable to begin counting from the due date for the applicable plan
revision containing the control measures that will give rise to the emission reductions.
Thus, the first quantitative milestone date is December 31, 2017.
The emission levels at the milestone must demonstrate reasonable further progress toward attainment
by the applicable date. As noted in the introduction to this section, RFP is defined so as to consider the
reductions in emissions required to ensure attainment of the NAAQS by the attainment date or which
may reasonably be required by the Administrator. Since the applicable attainment date (December 31,
2015) precedes the milestone date, the quantification of the emissions reductions to be achieved must
be taken to mean the level of emissions in 2015 used to demonstrate attainment.
From the date of the milestone, the State shall have 90 days to submit to the Administrator “a
demonstration that all measures in the plan approved under this section have been implemented and
that the milestone has been met.”
UDAQ herein commits to prepare and submit a milestone report no later than 90 days from the
milestone.

Logan – Page 68
Chapter 9 – CONTINGENCY MEASURES

9.1 Background
Consistent with section 172(c)(9) of the Act, the State must submit in each attainment plan specific
contingency measures to be undertaken if the area fails to make reasonable further progress, or fails to
attain the PM2.5 NAAQS by its attainment date. The contingency measures must take effect without
significant further action by the State or EPA.
Nothing in the statute precludes a State from implementing such measures before they are triggered,
but the credit for a contingency measure may not be used in either the attainment or reasonable further
progress demonstrations.
The SIP should contain trigger mechanisms for the contingency measures, specify a schedule for
implementation, and indicate that the measures will be implemented without further action by the
State or by EPA.
The CAA does not include the specific level of emission reductions that must be adopted to meet the
contingency measures requirement under section 172(c)(9). Nevertheless, in the preamble to the Clean
Air Fine Particulate Rule (see 72 FR 20643) EPA recommends that the “emissions reductions anticipated
by the contingency measures should be equal to approximately 1 year’s worth of emissions reductions
necessary to achieve RFP for the area.”

9.2 Contingency Measures and Implementation Schedules for the Nonattainment Area
The following measures have been set aside for contingency purposes:
Woodburning Control –As part of the control strategy for the SIP, rule R307-302 has been amended to
change the no-burn call from 35 µg/m3 to 25 µg/m3. Credit for this change is included in the modeled
attainment demonstration as well as the RFP demonstration. However, R307-302 also includes a
mechanism to further revise the no-burn call to only 15 µg/m3 should a contingency situation arise. The
benefit of this rule is to prevent a buildup of particulate matter due to woodsmoke during periods of
poor atmospheric mixing which typically precede exceedances of the 24-hour PM2.5 NAAQS. This rule
has been adopted, and can take effect immediately if so required.
This contingency measure will be triggered by an EPA determination that: 1) the area has, based on the
state’s milestone report under 189(c), failed to make RFP; or 2) has failed to attain the NAAQS by the
applicable attainment date.

Logan – Page 69
9.3 Conclusions
Control measures developed to meet increasingly stringent ozone and fine PM2.5 standards in Utah’s
urbanized areas have likewise become increasingly stringent, and still it is a challenge to attain the 2006,
PM2.5 NAAQS. This leaves little room for additional reductions that can be set aside as contingency
measures.
In the Cache Valley, there are no major stationary point sources. Area sources and on-road mobile
sources contribute the emissions that result in elevated PM2.5 concentrations. For the most part, further
emission controls in these categories extend beyond the authorities of UDAQ. The most meaningful
reductions in future emissions of VOC, an important PM2.5 precursor, will likely result from national
programs that apply additional restrictions of VOC in consumer products, and from what will likely result
from Tier III of the federal motor vehicle control program.