Joint Appendix — Oklahoma, et al., Petitioners v. Environmental Protection Agency, et al.
Supreme Court briefDec 13, 2024
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Nos. 23-1067, 1068
In the
Supreme Court of the United States
OKLAHOMA, et al.,
Petitioners,
v.
ENVIRONMENTAL PROTECTION AGENCY, et al.,
Respondents.
PACIFICORP, et al.,
Petitioners,
v.
ENVIRONMENTAL PROTECTION AGENCY, et al.,
Respondents.
On Writs of Certiorari to the United States
Court of A ppeals for the Tenth Circuit
JOINT APPENDIX
Mithun Mansinghani
Counsel of Record
for Petitioners
Oklahoma, et al.
Lehotsky Keller Cohn LLP
629 West Main Street
Oklahoma City, OK 73102
(202) 309-6027
mithun@lkcfirm.com
Elizabeth B. Prelogar
Counsel of Record
for Respondents
Solicitor General
United States
Department of Justice
950 Pennsylvania Avenue, NW
Washington, DC 20530
(202) 514-2217
supremectbriefs@usdoj.gov
PETITIONS FOR CERTIORARI FILED MARCH 28, 2024
CERTIORARI GRANTED OCTOBER 21, 2024
334128
Misha Tseytlin
Counsel for Petitioner
PacifiCorp, et al.
Troutman Pepper
Hamilton Sanders LLP
227 West Monroe, Suite 3900
Chicago, IL 60606
(608) 999-1240
misha.tseytlin@troutman.com
Stanford Edward Purser
Counsel for Petitioner
the State of Utah
Office of Utah
Attorney General
160 East 300 South, 5th Floor
Salt Lake City, UT 84111
(385) 382-4334
spurser@agutah.gov
i
TABLE OF APPENDICES
Page
A P P E N DI X A — E XC E R P T S F R O M
OK LA HOM A
2015
OZONE
INFRASTRUCTURE AND TRANSPORT
SI P ( EPA-R 0 6 - OA R - 2 0 2 1- 0 8 01- 0 0 0 5 ),
DATED OCTOBER 25, 2018 . . . . . . . . . . . . . . . . . . . 1a
APPENDIX B — EXCERPTS FROM UTAH
S TA T E I M PL E M EN TA T ION PL A N:
2008 OZONE IT AND 2015 OZONE ISIP
(EPA-R08-OAR-2022-0315-0007), DATED
JANUARY 24, 2020 . . . . . . . . . . . . . . . . . . . . . . . . . . 33a
APPENDIX C — COMMENT SUBMITTED BY
UTAH DEPARTMENT OF ENVIRONMENTAL
QUALITY (EPA-R08-OAR-2022-0315-0011),
DATED JULY 25, 2022 . . . . . . . . . . . . . . . . . . . . . . 58a
A P P E N DI X D — E XC E R P T S F R O M
COMMENT SUBMITTED BY PACIFICORP
(EPA-R08-OAR-2022-0315-0014), DATED
JULY 25, 2022 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68a
A P P E N DI X E — E XC E R P T S F R O M
RESPONSE TO COMMENTS DOCUMENT
(EPA-HQ-OAR-2021-0663-0083) . . . . . . . . . . . . . . 106a
A PPENDIX F — EXCERPTS FROM AIR
QUA LI T Y MODELI NG T ECH N ICA L
SUPPORT DOCUMENT (EPA-HQ-OAR2021-0663-0085) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234a
1a
Appendix AFROM OKLAHOMA
APPENDIX A — EXCERPTS
2015 OZONE INFRASTRUCTURE AND
TRANSPORT SIP (EPA-R06-OAR-2021-0801-0005),
DATED OCTOBER 25, 2018
Michael J. Teague
Secretary of Energy
& Environment
Mary Fallin
Governor
STATE OF OKLAHOMA
OFFICE OF THE
SECRETARY OF ENERGY & ENVIRONMENT
204 N. ROBINSON, SUITE 1010 • OKLAHOMA CITY,
OK 73102 • 405-285-9213 • FAX 405-285-9212
October 25, 2018
CERTIFIED MAIL, RETURN RECEIPT REQUESTED
Anne Idsal, Regional Administrator (6RA)
U.S. Environmental Protection Agency—Region 6
1445 Ross Avenue, Suite 1200
Dallas, TX 75202-2733
Subject:
Certification of SIP Elements for the 2015
Primary and Secondary Ozone NAAQS under
Clean Air Act Sections 110(a)(1)-(2)
Dear Administrator Idsal:
In a letter dated September 24, 2013 Governor Mary
Fallin appointed me as her designee for the purpose
of submitting documents to the U.S. Environmental
2a
Appendix A
Protection Agency (EPA) for approval and incorporation
into the State Implementation Plan (SIP) for the State of
Oklahoma. The Oklahoma Department of Environmental
Quality (DEQ) is given the primary responsibility and
authority to prepare and implement the state’s air quality
management plan under Oklahoma Statutes.
Sections 110(a)(1) and (2) of the Clean Air Act requires
that each state review and revise as necessary its SIP
following promulgation of a revised National Ambient
Air Quality Standards (NAAQS) (See U.S.C. § 7410(a)(1) and
(2)). On October 1, 2015, the EPA administrator signed the
Primary National Ambient Air Quality Standards for
Ozone (80 Fed. Reg. 65292, October 26, 2015). EPA issued
the “Guidance on Infrastructure State Implementation
Plan (SIP) Elements under Clean Air Act Sections
110(a)(1) and 110(a)(2)” in September 2013. Under this
guidance, states may certify that their existing SIPs meet
the “infrastructure” elements of § 110(a)(2), rather than
submitting a revised SIP for the revised NAAQS such as
the 2015 Ozone NAAQS. Oklahoma’s SIP is codified in 40
CFR Part 52, Subpart LL.
On behalf of the State of Oklahoma, I hereby certify that,
as indicated in the enclosed table titled “Oklahoma’s State
Implementation Plan (SIP) Submittal ‘Infrastructure’
Checklist,” and the enclosed Technical support document
titled “Oklahoma Demonstration of Compliance with
the Good Neighbor Requirements of Clean Air Act
Section 110(a)(2)(D)(i)(I) for the 2015 Ozone National
Ambient Air Quality Standard,” Oklahoma’s SIP meets
the infrastructure and Good Neighbor obligations for the
3a
Appendix A
2015 Primary and Secondary Ozone NAAQS. To date,
the only SIP change required to meet the revised 2015
Ozone NAAQS was a revision to Appendix E and F of
OAC 252:100, to add the new 8-hour Ozone standard
[CAA § 110(a)(2)(H)], which became effective September
15, 2016.
State public participation procedures for such SIP
submittals were submitted to EPA for review under 40
CFR § 51.102. In a letter dated August 23, 2012, EPA
concurred that Oklahoma’s procedures are consistent
with the requirements of 40 CFR § 51.102 and associated
guidance. Public notice for this submittal was posted
on DEQ’s web site on August 15, 2018, to allow the
opportunity to provide comments and to request a public
hearing preliminarily scheduled for September 17, 2018
at DEQ’s Central Office.
No hearing request was received during the minimum
30-day comment period (8/15/18—9/14/18). Therefore, a
notice of hearing cancellation was published on DEQ’s
website on September 14, 2018. Attached is documentation
of the public notice and submittal process. Also attached
are copies of comments received during the comment
period and a Response to Comments document. It is our
understanding that the final results of EPA’s review of
this submittal will be determined through rulemaking
and will be published in the Federal Register.
Please note that Oklahoma currently has no designated
Ozone nonattainment or maintenance areas so no
nonattainment plans are due.
4a
Appendix A
If you have questions, please contact Mr. Eddie
Terrill, Director, Air Quality Division, Department of
Environmental Quality at (405) 702-4100.
Sincerely,
/s/ Michael Teague
Michael Teague
Secretary of Energy and Environment
5a
Appendix A
Oklahoma Demonstration of Compliance with
the Good Neighbor Requirements of Clean Air Act
Section 110(a)(2)(D)(i)(I) for the 2015 Ozone
National Ambient Air Quality Standard
October 2018
Oklahoma Department of Environmental Quality
707 N Robinson
Oklahoma City, OK 73101
Oklahoma 2015 Ozone Transport SIP
6a
Appendix A
[This page intentionally left blank.]
7a
Appendix A
[TABLE INTENTIONALLY OMITTED]
Oklahoma Demonstration of Compliance
with the Good Neighbor Requirements of
Clean Air Act Section 110(a)(2)(D)(i)(I)
for the 2015 Ozone National Ambient
Air Quality Standard
1.0 Introduction
Sections 110(a)(1) and (2) of the Clean Air Act (CAA)
require all states to adopt and submit to the Environmental
Protection Agency (EPA) any necessary revisions to its
State Implementation Plans (SIP) which provide for
the implementation, maintenance, and enforcement of a
new or revised National Ambient Air Quality Standard
(NAAQS). Such revisions are commonly referred to
as “infrastructure SIPs.” The EPA revised the ozone
NAAQS in October 2015 and completed the designation
process to identify most nonattainment areas in April
2018, and finalized designations on July 25, 2018. The
Oklahoma Department of Environmental Quality (DEQ)
is submitting this document to satisfy the transport SIP
requirements of CAA Section 110(a)(2)(D)(i)(I), which is
commonly referred to as the “Good Neighbor” provision.
2.0 Request
CAA section 110(a)(2)(D)(i)(I) prohibits emissions from
states that will contribute significantly to nonattainment
or interfere with maintenance in any other state with
respect to any primary or secondary NAAQS. However,
8a
Appendix A
EPA stated in the notice for the Cross-State Air Pollution
Rule Update for the 2008 Ozone NAAQS (“2016 CSAPR
Update”), that “… EPA does not view the obligation under
the good neighbor provision as a requirement for upwind
states to bear all of the burden for resolving downwind air
quality problems. Rather, it is an obligation that upwind
and downwind states share responsibility for addressing
air quality problems. If, after implementation of reasonable
emissions reductions by an upwind state, a downwind air
quality problem persists, whether due to international
emissions or emissions originating within the downwind
state, the EPA can relieve the upwind state of the obligation
to make additional reductions to address that air quality
problem. But the statute does not absolve the upwind state
of the obligation to make reasonable reductions in the first
instance.” [81 Fed. Reg. 74536, 26 Oct 2016]
The State of Oklahoma, through DEQ, is requesting
the EPA to approve the Oklahoma Demonstration of
Compliance with the Good Neighbor Requirements of
Clean Air Act Section 110(a)(2)(D)(i)(I) for the 2015 Ozone
National Ambient Air Quality Standard as a revision to
the SIP. This revision supplements EPA’s Determination
Regarding Good Neighbor Obligations for the 2008 Ozone
National Ambient Air Quality Standard proposal [83
Fed. Reg. 31915, 10 July 2018], in which EPA finds that
the 2016 CSAPR Update fully addresses CAA section
110(a)(2)(D)(i)(I) (i.e., “Good Neighbor”) requirements
for Oklahoma.
9a
Appendix A
3.0 Background
On October 26, 2015, EPA promulgated a revised NAAQS
for ozone based on 8-hour average concentrations [80 Fed.
Reg. 65292]. EPA revised the level of the 8-hour ozone
NAAQS to 0.070 parts per million (ppm). EPA completed
the designation process to identify nonattainment areas
in April 2018; all areas of Oklahoma were designated as
attainment/unclassifiable [83 Fed. Reg. 25825, 4 June
2018].
Pursuant to section 110(a) of the CAA, states are required
to submit SIPs to provide for the implementation,
maintenance, and enforcement of a new or revised NAAQS
within three (3) years following the promulgation of
such NAAQS, or within a shorter period as EPA may
prescribe. More specifically, section 110(a)(1) provides
the procedural and timing requirements for SIPs.
Section 110(a)(2) lists specific elements that states must
meet for ‘‘infrastructure’’ SIP requirements related to a
newly established or revised NAAQS. These requirements
include basic SIP elements such as requirements for
monitoring, basic program requirements, and legal
authority that are designed to assure attainment and
maintenance of the NAAQS.
On January 28, 2015, DEQ submitted a plan to satisfy the
requirements of section 110(a)(2) of the CAA for the 2008
ozone NAAQS. This submittal addressed the following
infrastructure elements, or portions thereof: section 110(a)(2)
(A), (B), (C), (D), (E), (F), (G), (H), (I), (J), (K), (L), and (M) of the
CAA. On December 9, 2016, EPA approved the submittal [81
10a
Appendix A
Fed. Reg. 89008]. DEQ did not make a submittal to address the
transport portion, (§110(a)(2)(D)(i)(I)) of the Infrastructure
SIP, and on July 13, 2015, [80 Fed. Reg. 39961], EPA
made a Finding of Failure To Submit a Section 110 State
Implementation Plan for Interstate Transport for the 2008
National Ambient Air Quality Standards for Ozone for 24
states, which included Oklahoma. This finding of failure to
submit establish a 2-year deadline for EPA to promulgate
a Federal Implementation Plan (FIP) to address the
interstate transport SIP requirements pertaining to
significant contribution to nonattainment and interference
with maintenance unless, prior to EPA promulgating a
FIP, the state submits, and the EPA approves, a SIP that
meets these requirements.
On June 29, 2018, the EPA proposed [83 Fed. Reg. 31915,
July 10, 2018] that the 2016 CSAPR Update [81 Fed.
Reg. 74504, October 26, 2016] fully addresses 20 states’
interstate pollution transport obligations for the 2008
ozone NAAQS. The proposal relies on EPA’s latest data
and modeling to assess air quality nonattainment and
maintenance for the 2008 ozone NAAQS. This analysis
found that there are projected to be no remaining
nonattainment or maintenance receptors in the eastern
United States by 2023. In accordance with this finding,
EPA is proposing to determine that the 20 states
covered by this proposal would not need to submit SIPs
establishing additional control requirements beyond the
2016 CSAPR Update to address transported ozone and
ozone precursors with respect to the 2008 ozone NAAQS.
Also, EPA would have no obligation to establish additional
control requirements for sources in these states.
11a
Appendix A
4.0 Ozone
4.1 Formation
Ground-level ozone (O3) is a gas that is not usually emitted
directly into the air, but is a secondary pollutant formed
by the reaction of oxides of nitrogen (NOx) and volatile
organic compounds (VOCs) in the presence of sunlight.
Many types of sources emit these precursor pollutants,
including power plants and industrial facilities, onroad and off-road motor vehicles, engines, and small
sources collectively referred to as area sources. Ozone
is predominately a summertime pollutant; however, high
ozone concentrations have been observed in cold months
when snow on the ground reflects ultraviolet light so it
makes a double pass through the atmosphere and provides
more energy for the ozone formation reaction. Ozone and
ozone precursors (NOx and VOCs) can be transported
hundreds of miles.
4.2 Ozone Precursors—NOx and VOCs
The Good Neighbor provision of the CAA “provides both
the states and the EPA with the flexibility to develop
a remedy targeted at a particular air quality problem,
including the flexibility to tailor the remedy to address
the particular precursor pollutants and sources that
would most effectively address the downwind air quality
problem.”1 “In order to address the regional transport
1. Response to December 9, 2013, Clean Air Act Section 176A
Petition From Connecticut, Delaware, Maryland, Massachusetts,
New Hampshire, New York, Pennsylvania, Rhode Island and
Vermont, 82 Fed. Reg. 6516, 19 Jan 2017.
12a
Appendix A
of ozone…., the EPA has promulgated four (4) regional
interstate transport rules focusing on the reduction
of NOx emissions, as the primary meaningful precursor
to address regional ozone, from certain sources located
in states in the eastern half of the U.S. 2 ” The Ozone
Transport Assessment Group’s (OTAG) Regional and
Urban Scale Modeling, and Air Quality Analysis Work
Groups concluded, with which EPA agreed, “Regional
NOx emissions reductions are effective in producing ozone
benefits; the more NOx emissions reduced, the greater
the benefit to air quality; and VOC controls are effective
in reducing ozone locally and are most advantageous
to urban nonattainment areas.” The EPA concluded, “a
regional strategy focusing on NOx reductions across a
broad portion of the region will help mitigate the ozone
problem in many areas of the East” [82 Fed. Reg. 6517,
19 Jan 2017].
4.3 EPA’s Designation Process
On October 1, 2015, the EPA revised both the primary
and secondary NAAQS for ozone to a level of 0.070 ppm;
annual fourth-highest daily maximum 8-hour average
concentration, averaged over 3 years [80 Fed. Reg. 65292,
26 Oct. 2015]. On November 6, 2017, EPA designated
approximately 85% of the counties in the United States
as attainment/unclassifiable with the 2015 ozone standard
based on 2014 -- 2016 design values [82 Fed. Reg. 54232].
EPA completed additional area designations for most of
the remaining portions of the United States in accordance
with the requirements of CAA section 107(d) on April 30,
2018, [83 Fed. Reg. 25825] and designated eight counties in
2. Ibid
13a
Appendix A
the San Antonio area on July 25, 2018 [83 Fed. Reg. 35136].
All counties in Oklahoma were designated “unclassifiable/
attainment” for the 2015 8-hour ozone NAAQS [82 Fed.
Reg. 54232 and 83 Fed. Reg. 25825].
4.4 Transport Modeling
4.4.a. EPA
EPA has provided air quality modeling using a 2011-base
platform to help states address the requirements of CAA
section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS. This
modeling was provided in its Notice of Availability of
the Environmental Protection Agency’s Preliminary
Interstate Ozone Transport Modeling Data for the 2015
Ozone National Ambient Air Quality Standard [82 Fed.
Reg. 1733, 6 Jan. 2017].
4.4.b. Texas Commission on Environmental Quality
(TCEQ)
TCEQ has developed modeling specifically to address the
2015 ozone standard Good Neighbor SIP requirements.
The modeling results and reports can be found at http://
www.deq.state.ok.us/aqdnew/rulesandplanning/o3isip2015/
17039SIP_2015OzoneTransport_ado_backup.pdf.
One major way the TCEQ modeling differs from the EPA
modeling is that TCEQ uses a 2012 base year instead of
a 2011 base year. DEQ and TCEQ have both submitted
comments on the unsuitability of meteorological data
from the May through September 2011 episode for ozone
modeling in response to several EPA ozone model updates.
DEQ specifically submitted comments in response
14a
Appendix A
to the Notice of Availability of the Environmental
Protection Agency’s Preliminary Interstate Ozone
Transport Modeling Data for the 2015 Ozone National
Ambient Air Quality Standard [82 Fed. Reg. 1733, 6
Jan. 2017]. Evidence supporting the fact that 2011 was a
meteorologically anomalous year for Oklahoma and Texas
is found in Attachment A of the October Memorandum from
Peter Tsirigotis, EPA OAQPS, to Regional Air Division
Directors, Regions 1-10, entitled Considerations for
Identifying Maintenance Receptors for Use in Clean Air
Act Section 110(a)(2)(D)(i)(I) Interstate Transport State
Implementation Plan Submission for the 2015 Ozone
National Ambient Air Quality Standards (“Tsirigotis
October 2018 Memo”). 2011 was the hottest year on record,
and the single-worst drought year recorded in Texas
since 1895. In Oklahoma, the 2011 ozone season was the
warmest on record, with the five-month period from May
to September showing a positive temperature departure
from the 20th century mean of 5.3 ºF, and was the third
driest period on record.
4.5 New Information and Analytical Approaches
On March 27, 2018, EPA issued a Memorandum from
Peter Tsirigotis, EPA OAQPS, to Regional Air Division
Directors, Regions 1-10, entitled Information on the
Interstate Transpor t State Implementation Plan
Submission for the 2015 Ozone National Ambient Air
Quality Standards under Clean Air Act Section 110(a)(2)
(D)(i)(I) (“Tsirigotis March 2018 Memo”). The Tsirigotis
March 2018 Memo provided newly-available contribution
modeling results, which are still based on the year 2011,
along with a list of potential flexibilities in analytical
approaches for developing good neighbor SIPs for the
15a
Appendix A
2015 Ozone NAAQS.
Since EPA developed CSAPR, the original rule and
subsequent update were based on EPA’s modeling that
used a screening threshold of one percent (1%) of the
NAAQS to identify contributing upwind states warranting
further review and analysis. EPA has acknowledged this
threshold represents a policy choice, rather than a healthbased threshold grounded in risk assessment. In essence,
this threshold represents a compromise that allowed the
responsibilities for upwind reductions to be spread over a
sufficiently-large number of states so that no state would
be unduly burdened (individually) with requirements for
NOx reductions. Further, in the 2015 transport NODA,3 the
EPA acknowledged that a contribution of 1% of the NAAQS
from an upwind state alone does not determine whether the
upwind state significantly contributes to nonattainment or
interferes with maintenance of a NAAQS to a downwind
state. The 1% threshold represents a screening level and
the magnitude of the reductions required were determined
by a cost-effectiveness analysis with modeling performed
to confirm that the cost-effective reductions would have
the desired result (attainment of the ozone NAAQS in all
but a handful of downwind monitoring sites). It is entirely
possible that estimated emissions reductions resulting
from emission controls selected based on the costeffectiveness analysis would be greater than that required
to bring an upwind state below the 1% significance
threshold and it is also possible that, after achieving the
3. Notice of Availability of the Environmental Protection
Agency’s Preliminary Interstate Ozone Transport Modeling
Data for the 2015 Ozone National Ambient Air Quality Standard
(NAAQS), 82 Fed. Reg. 1740 (January 6, 2017).
16a
Appendix A
cost-effective reductions, a state’s contributions could
remain above the threshold. For the original CSAPR and
2016 CSAPR Update, the 1% threshold represented an
effective policy choice that balanced the need to achieve
reductions with cost and distributional concerns. This
approach was especially well-suited to these rules, because
the targeted sector (fossil-fueled Electricity Generating
Units—EGUs) represented an especially target-rich
environment for cost-effective NOx emission reductions
at that time. Many facilities (older coal-fired boilers,
natural gas-fired turbines, etc.) were decades old and had
not been equipped with simple, cost-effective technologies
like low-NOx burners. In addition, the distribution of
NOx allowances tipped the economic calculus in favor of
dispatching newer, less-polluting units (e.g., combinedcycle turbines with selective catalytic reduction). Because
the electric market is regional, it made sense to bring in a
larger pool of upwind states to participate in the program
to mitigate the possibility that power generation would
switch to states left out of the program, yielding increased
NOx emissions from nonparticipating facilities that would
negate the reductions achieved by participating states.
DEQ concurs with this approach for the original CSAPR
and 2016 CSAPR Update, but DEQ believes that transport
issues that need to be addressed in response to the
adoption of the 2015 ozone NAAQS are more granular
and would benefit from a more focused approach. The
possibility of using a different significance threshold was
one of the areas of flexibility addressed in the Tsirigotis
March 2018 Memo 4 , and later in his August 2018
4. Memorandum from Peter Tsirigotis, EPA OAQPS, to
EPA Regional Air Division Directors, Regions 1-10, “Guidance
on Significant Impact Levels for Ozone and Fine Particles in the
17a
Appendix A
Memo 5 . For the 2015 ozone NAAQS, DEQ believes that 1.0
ppb would be a more appropriate significant impact level
for ozone transport. If EPA recommends a Significant
Impact Level (SIL) for ozone of 1.0 ppb for Prevention
of Significant Deterioration (PSD) determinations, 6
then the significant impact level for ozone transport
should be at least 1.0 ppb. It is illogical to allow a new
single source to have a higher impact before requiring
additional controls than what is required for an entire
state. DEQ believes this is especially relevant for this
transport evaluation, because the previous rulemakings
have harvested most of the low-hanging fruit represented
by available controls on EGUs, most of which were already
equipped with continuous emissions monitoring systems
(CEMS) and whose emissions were already reported to
the Clean Air Markets Division (CAMD). Attainment of
the 2015 ozone NAAQS will likely require more targeted
reductions on smaller sources and enhanced compliance
verification on facilities already covered by New Source
Performance Standards (NSPS). For example, states
with recalcitrant ozone attainment problems which are
experiencing a boom in oil and gas development would
do well to address control of NOx and VOC emissions in
Prevention of Significant Deterioration Permitting Program,”
April 17, 2018.
5. Memorandum from Peter Tsirigotis, EPA OAQPS, to
EPA Regional Division Directors, Regions 1-10, “Analysis of
Contribution Thresholds for Use in Clean Air Act Section 110(a)
(2)(D)(i)(I) Interstate Transport State Implementation Plan
Submissions for the 2015 Ozone National Ambient Air Quality
Standards,” August 31, 2018
6. Also from the April 17, 2018 Tsirigotis memo.
18a
Appendix A
counties not currently classified nonattainment. These
efforts require a more granular approach, including the
adoption of presumptive best available control technologies
(BACT) for new installations. With additional focus on
New Source Review (NSR), it is important to use a similar
metric to evaluate potential impacts. Adoption of a 1.0 ppb
significance threshold to assess interstate transport would
represent a step toward achieving that goal.
4.6 Ozone Transport Assessment for Good Neighbor
SIPs 4-step framework
EPA developed a 4-step framework for addressing the
requirements of the “Good Neighbor” provision in the
CSAPR for the 1997 ozone NAAQS and the 1997 and 2006
PM 2.5 (particulate matter less than 2.5 microns) NAAQS:
(1) identify downwind receptors that are expected to have
problems attaining or maintaining the NAAS;
(2) determine which upwind states significantly contribute
(or are “linked”) to the downwind air quality problems;
(3) for states that are “linked,” quantify the level of
upwind emissions that need to be addressed to satisfy
the “Good Neighbor” provision; and,
(4) adoption of permanent and enforceable emission
reductions in “linked” upwind states.
EPA has used this 4-step process for each successive ozone
standard.
19a
Appendix A
4.7 EPA Modeling Data
DEQ utilized the data provided by EPA7 to perform step
one and two above for Oklahoma. We eliminated all sites
that had an Oklahoma contribution of less than 0.70 ppb,
then eliminated all of the sites that did not have a 2023
average DV, or 2023 maximum DV greater than 70.9 ppb.
The result was the six sites listed below:
Site ID
County
State
2023en8
Average
260050003
Allegan
MI
69.0
481210034
Denton
TX
69.7
484392003
Tarrant
TX
72.5
480391004
Brazoria
TX
74.0
550790085
Milwaukee
WI
71.2
551170006
Sheboygan
WI
72.8
2023en Maximum
Oklahoma Contribution
71.7
1.31
72.0
1.23
7. The data EPA obtained from its modeling for the 2015
ozone transport, is located at https://w w w.epa.gov/sites/
production/files/2018-05/updated_2023_modeling_dvs_collective_
contributions.xlsx
8. Note, 2023en is the scenario name for the updated EPA
modeling.
20a
Appendix A
74.8
1.71
74.9
0.90
73.0
0.76
75.1
0.95
Next, the flexibility EPA has allowed—a modified step
2, using a Significant Impact Level of 1.0 ppb—would
eliminate three sites from consideration, and leave only
the three sites listed below that need further review
and analysis of any Significant Impacts from Oklahoma
emissions:
Site ID
County
State
2023en
Average
260050003
Allegan
MI
69.0
481210034
Denton
TX
69.7
484392003
Tarrant
TX
72.5
2023en Maximum
Oklahoma Contribution
71.7
1.31
72.0
1.23
74.8
1.71
To address its responsibilities for the interstate transport
of ozone, TCEQ performed ozone modeling using a 2012
base year. The TCEQ future year modeling used growth
and control factors based on projected growth in the
demand for goods and services, along with the reduction
21a
Appendix A
in emissions expected from state, local, and federal
control programs. This modeling data can be found at:
http://www.deq.state.ok.us/aqdnew/rulesandplanning/
o3isip2015/texas_ot_2023_dvf_with_state_contributions.
xlsx. In this spreadsheet, note that the 2023 design
value for Denton County TX (481210034) is 68 ppb, and
Tarrant County TX (484392003) is 66 ppb. The modeling
performed by Texas demonstrates that both of these sites
are in attainment in the year 2023, and therefore there is
no need to assess the impact of interstate transport on
these sites.
In the TCEQ modeling, Texas used an alternative method
for developing Maintenance DVs, using annual 4th high
values for years 2012 through 2014. The 2012 through
2014 DVs for the Denton and Tarrant county monitoring
sites are 81 and 77.7 ppb respectively. Using the EPA
method of the highest DV of the three DVs surrounding
the base year, the DVs for Denton and Tarrant County
monitoring sites are both 87 ppb. Applying the Relative
Reduction Factors (RRF) of 0.813 and 0.803 respectively,
the 2023 DVs for these sites are 65.9 and 62.4 for the Texas
method, and 70.7 and 69.9 for the EPA method. Although
Texas’s modeling shows a greater reduction, both sites
demonstrate attainment in 2023 using either EPA’s or
Texas’s method.
The TCEQ “ Transport Demonstration for Ozone”
assesses the impacts of anthropogenic emission sources
that are the largest contributors of NOx in the 10-county
22a
Appendix A
Dallas-Fort Worth ozone nonattainment area.99 Figure
2-5 of the TCEQ SIP shows that mobile sources represent
the largest source category (67,595 tons in 2014 out
of 125,981 tons total). However, anthropogenic NOx
contributions regionally, and mobile sources in particular,
have decreased significantly since 2005 (where mobile
NOx sources contributed 138,704 tons and anthropogenic
sources totaled 232,311 tons). The mobile source fleet
turnover in the Dallas-Ft Worth area is responsible
for approximately a 1 ppb per year reduction in ozone.
These trends are expected to continue as newer vehicles
continue to replace existing vehicles over the next 5 years.
Extrapolating from recent trends, it is expected that the
Denton and Tarrant sites will be in attainment by 2023.
Data relating to the remaining site to examine, Allegan
County Michigan, is listed below.
Site ID
County &
State
2023en
Average
2023en
Maximum
260050003
Allegan, MI
69.0
71.7
Oklahoma
Contribution
International
Contribution
Initial &
Boundary
1.31
0.54
11.85
The 2023en Average value is below 71 ppb, which means
this site is assumed to demonstrate attainment by 2023.
9. The link to the TCEQ Transport SIP was provided on
page 6 of this document.
23a
Appendix A
Since the 2023en Maximum is above 71 ppb, it is assumed
to be a maintenance area in 2023. The DV for the Allegan
site has had a substantial reduction in the last 6 years
from 84 ppb in 2012 to 73 ppb in 2017, a 1.8 ppb per
year decrease. The Allegan county site is substantially
influenced by mobile sources from the Chicago area, and
like the DFW area, these emissions are expected to be
greatly reduced in the near future, by roughly a 1 ppb per
year decrease, leading to Attainment for the Allegan site.
A flexibility provided by EPA in the Tsirigotis March
2018 Memo was to determine a state’s share of the ozone
in excess of the standard for the downwind monitor
to determine the amount of ozone reduction they are
modelled to be responsible for. In the EPA modelling, the
sum of contributions from all upwind states to the Allegan
site is 42.90 ppb, and the Oklahoma contribution is 1.31
ppb, which is 3%. We believe that our weight-of-evidence
approach (below) is sufficient to demonstrate trends that
will bring the Allegan County site into attainment by 2023.
However, even if that analysis was rejected, the relatively
small contribution from Oklahoma (3% of total upwind
state contributions) combined with the distance between
Oklahoma sources and the receptor, warrants a focus on
nearby states with greater proportional contributions
as the most prudent approach to addressing interstate
transport of ozone precursors.
5.0 Weight of evidence
Due to the emission reductions required by rules like
CSAPR, the 2016 CSAPR Update, and the regional haze
24a
Appendix A
requirements, the NOx emissions from electric generation
in Oklahoma has dropped significantly during the ozone
season in the last seven years. Oklahoma EGU Acid Rain
Ozone Season Emissions are listed below:
Oklahoma EGU Acid Rain Ozone
Season Emissions
Year
NOx Emissions
TPY
2011
38,285
2012
31,242
2013
23,462
2014
16,230
2015
12,997
2016
12,163
2017
10,435
The Southwest Power Pool (SPP) footprint changed in
2015 from part or all of 8 mostly central and southern
states to 13 states, including Montana, North and South
Dakota, and Wyoming. The SPP runs a day-ahead
market to provide the lowest cost electricity possible.
This means that in the summertime when the southern
states are in need of additional generation, the northern
states can supply it, reducing emissions in the southern
states on high electric demand days.
Electric generation in the state of Oklahoma in the last 8
years has been very dynamic, with the changes in the SPP,
25a
Appendix A
building of additional windfarms, and electric utilities
installing solar generation facilities having all led to
NOx reductions for the state.
The low-cost emission reductions have been obtained
from the electric generation sector, and any additional
reductions would require more costly emission controls.
Due to time and resource constraints, the modelling EPA
performed for the states to use for Good Neighbor SIPs,
used a 2011 base year (performing a 12 year projection to
2023), and therefore the Maintenance Monitor calculations
were based on the Maximum design value for years 2009
through 2013. The value for the Allegan County monitor
was 86 ppb (4 ppb higher than any other Michigan monitor).
If the modelling were performed using a 2016 base year
(performing a 7 year projection), the Maintenance monitor
design value would have been 75 ppb. Assuming a constant
rate of reduction, 86 ppb minus 71.7 ppb (future year
modelled value) equals a 14.3 ppb difference. 14.3 divided
by 12 (years) equals a 1.1917 ppb reduction per year
from EPA’s modeling. Applying the 1.1917 ppb per year
reduction to the 2016 Allegan County Maximum design
value of 75 ppb, results in a 66.66 ppb Design Value in the
seventh year (2023) , easily demonstrating attainment.
Oklahoma anthropogenic NOx and VOC data provided as
supporting data for the previously mentioned Tsirigotis
October 2018 Memo demonstrate a substantial reduction
of NOx and VOC from 2011 to 2023. The reductions for
NOx are from 405,000 to 235,000 tpy and VOC are from
414,000 to 295,000 tpy. These reductions should result in
26a
Appendix A
considerable ozone reductions.
6.0 Conclusions
DEQ has control measures in place to address ozone
precursor emissions and these measures have resulted
in significant decreases in 8-hour ozone design values in
Oklahoma. The average reduction in 8-hour ozone design
values for the State of Oklahoma monitoring sites is 0.79
ppb per year for the last 15 years (2004 -- 2017). Additional
NOx controls would not be cost effective.
Also, DEQ has a robust, SIP-approved NSR permitting
program and therefore has met the CAA infrastructure
requirements relating to PSD. The DEQ has also
determined that Oklahoma meets the visibility transport
provisions for the 2015 ozone NA AQS, as the state
is not contributing significantly to nonattainment or
maintenance issues in any other state.
In conclusion, this SIP revision demonstrates that
Oklahoma meets the interstate transport requirements of
CAA section 110(a)(2)(D)(i)(I) as well as the requirements
of section 110(a)(2)(D)(i)(II) for PSD and visibility
protection, and the interstate pollution abatement and
international air pollution requirements of section 110(a)
(2)(D)(ii) without further reductions.
27a
Appendix A
Summary of Comments and Responses
Oklahoma’s I-SIP Submittal for the Oklahoma
Demonstration of Compliance with the Good
Neighbor Requirements of Clean Air Act Section
110(a)(2)(D)(i)(I) for the 2015 Ozone National
Ambient Air Quality Standard
DEQ received no request for a public hearing during
the notice period, therefore, as stated in the public notice,
a hearing was not held. One set of comments was received
on September 17, 2018 from Guy Donaldson, Associate
Director for Air, Multimedia Division, EPA Region 6.
EPA’s comments were limited to the “Good Neighbor”
transport portion of the SIP submittal and all page
numbers below are references thereof.
1. COMMENT:
Section 4.5 New Information and Analytical
Approaches
EPA suggests factoring in information from the EPA
memo of August 31, 2018, “Analysis of Contribution
Thresholds for use in Clean Air Act Section 110(a)(2)
(D)(i)(I)Interstate Transport State Implementation
Plan Submissions for the 2015 Ozone National
Ambient Air Quality Standards.”
RESPONSE: We have added a reference to the
memo on page 9.
28a
Appendix A
2. COMMENT:
Section 4.7 EPA Modeling Data
EPA suggests an evaluation of the collective
contribution in the Dallas/Ft. Worth (DFW) and
Allegan, Michigan areas. Also, EPA is interested in
Oklahoma’s recommendations on whether different
contribution thresholds are appropriate based on
regional differences in the nature or extent of the
transport problem.
RESPONSE: The first sentence of this comment
is addressed on pages 12 and 13. As for the second
sentence in this comment, Oklahoma as not analyzed
the regional differences in the nature or extent
of the transport problem, so for now, we have no
recommendation on whether different contribution
thresholds are appropriate.
3. COMMENT:
Section 4.7 EPA Modeling Data
It would be helpful to add additional discussion
about the differences between the EPA and
TCEQ’s modeling results and why the two modeling
approaches reach different conclusions regarding
whether monitors in DFW will be in attainment in
2023 and whether the DFW area monitors should be
considered maintenance receptors. This discussion
should also include evaluation of the difference
29a
Appendix A
bet ween the EPA and TCEQ’s maintenance
receptor methodology calculations and the ozone
conduciveness of the 2011 vs. 2012 period.
RESPONSE: Most of page 12, and the first
paragraph of page 13 was added to address these
comments.
4. COMMENT:
Section 4.7 EPA Modeling Data
As weight of evidence in support of Oklahoma’s
conclusion that the DFW monitors will be in
attainment and should not be considered maintenance
receptors, EPA also suggests evaluation of recent
ozone levels coupled with monitoring trends
and modeling analyses for the DFW area. When
considering recent monitoring data, please assess
whether the recent period was conducive to ozone
formation. The TCEQ monitoring analyses indicate
that DFW 8-hour ozone monitoring values have
been dropping at a rate of over 1 ppb/year largely due
to mobile fleet turnover which is also supported by
past TCEQ modeling for future years 2017 and 2018.
Much of this information can be found in recent TCEQ
Attainment Demonstration SIP submittal materials
for the DFW area, which also include conceptual model
and analyses of high ozone events in DFW.
RESPONSE: We provide a link to the Texas Good
Neighbor SIP data and documents on page 6. We
address the annual decrease in ozone on page 12.
30a
Appendix A
5. COMMENT:
Section 4.7 EPA Modeling Data
EPA notes the TCEQ modeling which Oklahoma is
relying upon for its SIP has Allegan projected to be
a nonattainment receptor in 2023 and the EPA’s
modeling has Allegan projected to be a maintenance
receptor. Oklahoma may want to consider recent DV
trends at Allegan (2015-2017 is 73 ppb) and any
information on ozone formation and DV trends due
to fleet turnover, etc. that could support a conclusion
that the Allegan monitor will be in attainment in
2023 and should not be considered a maintenance
receptor.
RESPONSE: We address this on pages 12 and 13.
6. COMMENT:
Section 4.7 EPA Modeling Data
Regarding international contr ibutions, EPA
suggests that a conclusion that the monitor will not
have attainment or maintenance issues in 2023 will
require a more fulsome discussion with respect to the
relative contributions of anthropogenic international
emissions and upwind domestic anthropogenic
emissions, and such discussion should address why
it is technically and legally supportable to “subtract
100%” of anthropogenic and non-anthropogenic
contributions from Canada and Mexico as well as 2%
31a
Appendix A
of the initial and boundary contribution.
RESPONSE: On page 12 we used other arguments
to substantiate our case that the Allegan county site
will gain attainment by 2023.
7. COMMENT:
Section 4.7 EPA Modeling Data
The proposed SIP revision indicates that reductions
of nitrogen oxide emissions from Oklahoma electric
generators to comply with the 2016 Cross-State Air
Pollution Rule Update should be enough to address
any Oklahoma obligation to reduce emissions that
interfere with maintenance of the 2015 ozone NAAQS
at the Allegan receptor. The EPA did estimate these
CSAPR emission reductions and take them into
account in the 2023 EPA modeling. If there are
additional reductions in NOx and/or VOC emissions
at Oklahoma EGUs or other industry sectors that
have not been included in the EPA’s 2023 modeling,
please provide details on the sources and reason for
additional reductions, amount of additional reduction,
some relative comparison to total emissions for
their industry sector(s) in Oklahoma and how
these additional reductions might meet any transport
obligations. EPA understands that Oklahoma’s EGU
sector may have recently switched to a market
based dispatch system and it may help to explore
if this will result in changes in NOx emissions in the
future compared to the EPA’s projections.
32a
Appendix A
RESPONSE: These comments are addressed on
page 14.
8. COMMENT:
Section 4.7 EPA Modeling Data
Finally, EPA notes that the EPA’s analysis does
indicate impacts from Oklahoma emissions on DFW
and Allegan monitors. Because of these potential
impacts, Oklahoma may wish to consider proceeding
to step 3 of the transport framework and considering
whether there are reasonable controls that might be
implemented to assure the state meets the Clean Air
Act’s transport requirements.
RESPONSE: Oklahoma believes that the 2016
CSAPR Update is the only reasonable control
warranted based on Oklahoma’s limited contributions
to the DFW and Allegan County monitors.
33a
Appendix B
APPENDIX B — EXCERPTS
FROM UTAH STATE
IMPLEMENTATION PLAN: 2008 OZONE IT AND
2015 OZONE ISIP (EPA-R08-OAR-2022-0315-0007),
DATED JANUARY 24, 2020
State of Utah
Office of the Governor
Salt Lake City, Utah
84114-2220
Gary R. Herbert
Spencer J. Cox
Governor
Lieutenant Governor
January 24, 2020
Gregory Sopkin, Regional Administrator
US EPA Region 8
1595 Wynkoop Street
Denver, Colorado 80202-1129
Dear Mr. Sopkin,
On January 31, 2013, to meet the Clean Air Act (CAA)
2008 ozone National Ambient Air Quality Standard
(NAAQS), the State of Utah submitted State of Utah
110(a)(2) SIP Infrastructure Elements for Ozone to
the Environmental Protection Agency (EPA) for its
approval. Based on EPA Assistant Administrator Gina
McCarthy’s memorandum titled Next Steps for Pending
Redesignation Requests and State Implementation
Plan Actions Affected by the Recent Court Decision
Vacating the 2011 Cross-State Air Pollution Rule issued
on November 19, 2012, the Division of Air Quality did not
address the good neighbor obligation of Section 110(a)(2)
34a
Appendix B
(D)(i)(I), commonly referred to as Prong 2, in its January
2013 submission. On April 29, 2014, the U.S. Supreme
Court reversed a D.C. Circuit decision, holding that the
CAA clearly requires that States address Prong 2 of the
CAA within three years of any new or revised NAAQS
promulgation. In response, the EPA issued a memorandum
entitled Information on the Interstate Transport “Good
Neighbor” Provision/or the 2008 Ozone National Ambient
Air Quality Standard (NAAQS) under Clean Air Act
(CAA) Section 1100(a)(2)(D)(i) in January of 2015.
On December 22, 2015, Utah submitted a supplement
to address CAA Section 110(a)(2)(D)(i)(I) with respect to
the 2008 ozone NAAQS. Utah’s submittal was disapproved
on October 19, 2016, by the EPA with reasoning found at
81 FR 71991. To satisfy the requirements identified in
both the EPA’s January 2015 memorandum and 81 FR
71991, the DAQ has prepared a document enclosed for your
approval titled State of Utah 110(a)(2) SIP Infrastructure
Elements for Ozone.
On December 28, 2015, the EPA promulgated a
new eight-hour concentration NAAQS for ozone. As a
result, the Division of Air Quality is required to submit
an Infrastructure State Implementation Plan (ISIP) to
demonstrate that Utah can implement, maintain, and
enforce the new standard. The CAA requires states to
submit ISIPs with specific elements outlined in Section
110(a)(2). To meet the requirements outlined in 110(a)(2),
the State has prepared a document titled 2015 State
Implementation Plan Infrastructure Elements for Ozone
which is also enclosed for your approval.
35a
Appendix B
Supporting documentation for both ISIPs are being
submitted by the Utah Division of Air Quality. If you
have questions about this request, please call Bryce Bird,
Director of the Division of Air Quality, at (801) 536-4064.
Sincerely,
/s/ Gary R. Herbert
Gary R. Herbert
Governor
Enclosures
36a
Appendix B
***
SIP Section VIII: Prevention of Significant Deterioration
was established as required by the Clean Air Act and
applies to all air pollutants regulated under the CAA. SIP
Section VIII is codified in R307-110-9 and R307-405, and
EPA approved it most recently on July 15, 2011, in 76 FR
41712. On April 14, 2011, Utah DAQ submitted revisions
to R307-405 to incorporate the federal Tailoring Rule
provisions that were promulgated on June 3, 2010. EPA
has not yet acted upon this submittal. Utah amended
R307-405 on November 6, 2019, to comply with EPA’s
January 17, 20127 revisions to Appendix W.
Utah’s permitting rules require sources to install best
available control technology (BACT) for all pollutants,
including ozone precursors.
Section 110(a)(2)(D)(i)(I): Interstate Transport
Provisions— Contribution to Nonattainment or
Maintenance
Requirement Summary
“Each such plan shall—contain adequate provisions:
(i) prohibiting, consistent with the provisions of this
subchapter, any source or other type of emissions activity
within the state from emitting any air pollutant in
amounts which will—
(I) contribute significantly to nonattainment in,
or interfere with maintenance by, any other state with
37a
Appendix B
respect to any such national primary or secondary
ambient air quality standard
Utah’s Infrastructure
Overview
Utah has authority required to revise its Infrastructure
SIP in accordance with CAA 110(a)(2)(H). This SIP
revision employs a weight-of-evidence approach to
demonstrate that emissions from the State of Utah do not
contribute to nonattainment or interfere with maintenance
of the 2015 8-hour ozone NAAQS in any other state.
EPA Modeling
The EPA began implementing the Cross-State Air
Pollution Rule (CSAPR) on January 1, 2015 to address
the interstate transport of nitrogen oxides (NO x) and
sulfur dioxide (SO2) between certain eastern states by
imposing limits on NOx and SO2 produced in those states.
Upwind states must control any NOx or SO2 emissions
that interfere with a downwind state’s agbility to attain
or maintain compliance with the NAAQS for PM 2.5 and
ozone. An upwind state is greater than 1% of the Ozone
NAAQS. The EPA finalized the CSAPR Update (Update)
on October 26, 2016, which affected 22 eastern states.
The Update also defined the western U.S. (or the West)
as consisting of 11 states, including Utah. The Update
noted that “the EPA is not addressing interstate emission
transport in this action for the 11 western contiguous
United States” and that “the EPA and western states,
38a
Appendix B
working together, are continuing to evaluate interstate
transport obligations on a case-by-case basis.”1
Following the Update, the EPA issued a Notice of Data
Availability (NODA) on January 7, 2017, for preliminary
interstate ozone transport modeling data and methods
for the 2015 ozone NAAQS. 2 The EPA stated the data was
issued to assist states with developing Infrastructure SIPs
to address the “good neighbor” requirements of the CAA.
The October 2017 NODA provided projected ozone values
for the 2023 analytic year and used base-year emissions
for 2011. The EPA then issued a memo on March 27, 2018,
that provided an update to the contribution modeling
in the January NODA. 3 Additionally, the March memo
listed potential flexibilities in analytical approaches for
developing a good neighbor SIP for each step of the fourstep transport framework.
The contribution modeling conducted for the CSAPR used
the Comprehensive Air Quality Model with Extensions
(CAMx) to run photochemical grid modeling simulations.4
1. Cross-State Air Pollution Rule Update for the 2008 Ozone
NAAQS. Final Rule. 81 Fed. Reg. 74523
2. 82 Fed. Reg. 1734.
3 . In for mat ion on t he Int er st at e T r a nsp or t St at e
Implementation Plan Submissions for the 2015 Ozone National
Ambient Air Quality Standards Under Clean Air Act Section
110(a)(2)(D)(i)(I). March 27, 2018.
4. Air Quality Modeling Technical Support Document for
the Final Cross State Air Pollution Rule Update, August 2016.
39a
Appendix B
The model used a 2011 modeling platform to project
ozone concentrations at individual monitoring sites for
the future year 2023. In the CSAPR rulemaking, the
EPA established a 1% threshold to determine, for eastern
states, whether an upwind state contributes significantly
to a downwind state’s receptor. 5 The modeling also
included contributions from western states and showed
that emissions from Utah would contribute more than
one percent of the 2015 ozone NAAQS to some monitors
in Colorado. However, in the CSAPR Update, the EPA
recognized that it was not appropriate to extend CSAPR
to western states without first considering important
“geographically specific factors.” States in the western
region thus appropriately continue to use a “weight-ofevidence” approach to demonstrate that air pollution
transport is addressed in accord with the Clean Air Act.6
Four-step Analysis
In the March 2018 Memorandum, the EPA adapted the
CSAPR four-step analysis framework for identifying
linkages between states not covered by the CSAPR. The
four steps are:
1. Identify downwind air quality problems;
5. Cross-State Air Pollution Rule Update for the 2008 Ozone
NAAQS. Proposed Rule. 80 Fed. Reg. 75714.
6. Pa r tial Approval and Pa r tial Disapproval of A i r
Quality State Implementation Plans; Arizona; Infrastructure
Requirements to Address Interstate Transport for the 2008 Ozone
NAAQS. Proposed Rule. 81 Fed. Reg. 15200, 15204.
40a
Appendix B
2. Identify upwind states that contribute enough to
those downwind air quality problems to warrant
further review and analysis;
3. Identifying the emissions reductions necessary
to prevent an identified upwind state from
contributing significantly to those downwind air
quality problems; and
4. Adopting permanent and enforceable measures
needed to achieve those emissions reductions.
Along with newly modeled contributions to downwind
receptor sites for the 2015 Ozone NAAQS, the March 2018
memo included a list of potential flexibilities in analytical
approaches for developing a good neighbor SIP.
DAQ identified the Denver Metro/North Front Range
nonattainment area (Denver NAA) as the only potential
area with air quality problems that could potentially be
affected by emissions from Utah. EPA’s modeling lists
five air quality monitors (See Table 1) within the Denver
NAA at which Utah contributes greater than 1% of the
2015 Ozone NAAQS. These receptors are discussed in
greater detail below.
In the preliminary list of potential flexibilities for step
1, EPA listed consideration of the downwind air quality
context, specifically assessing “the current and projected
local emission reductions and whether downwind areas
have considerd and/or used available mechanisms for
regulatory relief.” Considering the downwind air quality
41a
Appendix B
context in transport between western states, especially
with respect to emission reductions, is necessary because
of the nature of interstate transport in the West versus
the East. As the California Air Resources Board (CARB)
pointed out in its California Tranport Plan, receptors in the
West may primarily be impacted by local contributions.7
Therefore, it is reasonable in step 1 of this assessment to
considfer the current and projected emission reductions
in the Denver NAA.
Colorado’s Air Quality Control Commission recently
changed the oil and gas control requirements in Colorado’s
air quality regulations for compressors, pneumatic pumps,
equipment leaks, and fugitive emissions in the Denver
NAA. 8 Specific changes include requiring leak detection
and repair (LDAR) inspections at some compressor
stations, 95% emission reductions at some compressors
and pneumatic pumps, changes to inspection frequency,
and applicability clarifications. The changes strengthen
Colorado’s air regulations in the Denver NAA. However,
only two of the changes apply statewide: one change that
clarifies the definition of “venting” statewide, and the
7. The California Transport Plan states that “[i]n the West,
local contributions dominate contributions from other sources by
a factor of 8:1. In contrast, what is seen in the East is that local
contributions show a much lower impact resulting in a factor
of 1:2. This is an indication of a major difference between the
contributions that interstate transport makes to the local ozone
problem in the two areas of the country.” p. D-3.
8. Colorado Air Quality Control Commission’s 2017 Revisions
to Regulation Number 7—Oil and Gas Emissions Fact Sheet.
December 20, 2017.
42a
Appendix B
other that adds new recordkeeping elements in the LDAR
provisions of Regulationj Number 7. EPA’s HYSPLIT
analyses in the accompanhying technical support
documenht of Colorado’s ozone I-SIP approgal shows that
many of the emissions at the violating monitors originate
from in-state areas outside of the Denver NAA.9 Colorado
continues to evaluate local methods of control.
The identification of the Denver NAA satisfies step 1 of
the four-step process to identify downwind air quality
problems. To satisfy step 2, DAQ will use a weight-ofevidence analysis to show that emissions from Utah are
not contributing to nonattainment or interfering with
maintenance in the Denver NAA.
Weight-of-Evidence Analysis
The EPA recognizes a weight-of-evidence approach as
a valid method for western states to use to determine
interference. The EPA used a weight-of-evidence approach
in its assessment for Arizona’s Infrastructure SIP,
and approved prong’s 1 and 2 of Arizona’s 2008 Ozone
Infrastructure SIP on May 6, 2016, despite the state’s one
percent modeled contribution to receptors in California.10
9. COLOR A DO: Denver Met ro/ Nor th Front Range
Nonattainment Area Final Area Designations for the 2015 Ozone
National Ambient Air Quality Standards Technical Support
Document (TSD). Docket ID: EPA-HQ-OAR-2017-0548-0069.
10. Partial Approval and Partial Disapproval of A ir
Quality State Implementation Plans; Arizona; Infrastructure
Requirements to Address Interstate Transport for the 2008 Ozone
NAAQS. Final Rule. 81 Fed. Reg. 31513.
43a
Appendix B
Where Arizona does contribute over one percent of the
NAAQS to a projected downwind receptor in California
the EPA found, based on the overall weight-of-evidence,
that those receptors are not significantly impacted by
transported ozone from upwind states.
The EPA has also approved California’s transport SIP for
the 2008 ozone NAAQS, which uses a weight-of-evidence
approach for its demonstration.11 In the action, EPA found
that the plan met the requirements of CAA 110(a)(2)(D)
(i)(I) for the 2008 ozone NAAQS because California’s
emission control program adequately addressed the
transport requirement. As part of step two, DAQ will use
the weight-of-evidence approach to demonstrate that Utah
does not contribute enough to Colorado’s nonattainment
area to warrant further review and analysis.
Modeled Contributions
According to the modeling in EPA’s 2018 Memorandum,
DAQ has identified three nonattainment receptor sites
and two maintenance receptor sites in Colorado that
are within the samje Denver Metro/North Front Range
Nonattainment Area. Data from EPA’s March 27, 2018
memorandum and updated CSAPR modeling, shown
in Error! Reference source not found., identifies the
receptors in Colorado where Utah contributes more
than 1 percent of the 2015 Ozone NAAQS. The highest
contribution at any one receptor site is 1.23 ppb. Therefore,
11. Approval and Promulgation of A ir Quality State
Implementation Plans; California; Interstate Transpor t
Requirements for Ozone, Fine Particulate Matter, and Sulfur
Dioxide. Final Rule. 83 FR 65093
44a
Appendix B
Utah’s analysis below is meant to address both the prong
1 (significant contribution to nonattainment) and prong 2
(interference with maintenance) requirements of section
110(a)(2)(D)(i)(I).
2023
2023
Base
Base
Case
UT
Case
Maxi- Modeled
Average mum ContriMonitor
Design Design bution
ID
State County Value Value (ppb)
Nonattainment Receptors
80690011 CO Larimer
71.2
73
1.05
80350004 CO Douglas
71.1
73.2
1.08
80590006 CO Jefferson
71.3
73.7
0.83
Maintenance Receptors
80050002 CO Arapahoe 69.3
71.3
1.23
80590011 CO Jefferson
70.9
73.9
1.04
Table 1: Nonattainment and Maintenance receptors
identified in the Updated CSAPR Modeling
In EPA’s March 2018 Memorandum they pointed to states
whose contributions were greater than one percent of
the NAAQS as a threshold for establishing a “link” to
a receptor site. In a subsequent memo from EPA dated
August 31, 201812 , they analyzed, and found appropriate,
12. Analysis of Contribution Thresholds for Use in Clean
Air Act Section 110(a)(2)(D)(i)(I) Interstate Transport State
Implementation Plan Submissions for the 2015 Ozone National
Ambient Air Quality Standards.
45a
Appendix B
the use of different contribution thresholds. In the memo
EPA recommended that some states may use a 1.0 ppb
threshold for establishing a “link” to a receptor site if
the 1 ppb threshold captures a large percentage of the
total upwind contribution as compared to a one percent
threshold. There are five receptor sites in Colorado, shown
in Table 2, where Utah contributes more than 1 percent
of the 2015 NAAQS. All five of the sites are within the
same Denver NAA. The total upwind contribution across
these four sites is 32.29 ppb. When summed across all
four receptors a one percent threshold captures 60%
of the upwind contribution. A 1 ppb threshold captures
47% of the upwind contribution. Individually, two of the
receptor sites capture the same contribution at both one
percent and 1 ppb. Because the capture rate at 1 ppb and
1% are comparable, Utah finds that a one ppb threshold
is appropriate. Utah is then linked to four of the five
receptors in Table 1. Though DAQ uses the 1 ppb threshold
for this analysis, it will still evaluate contributions at the
fifth receptor to make a more complete assessment of the
modeled results.
Table 2: Comparison of contribution thresholds at receptor sites in Colorado
Sum of
Percent
Upwind
Sum of of Upwind Percent
ContriUpwind Contribu- of Upwind
bution
Contrition Cap- ContribuTotal Up- Captured
bution
tured us- tion Capwind State with 0.70 Captured ing a 0.70 tured usContribu- ppb (1%) with 1 ppb ppb (1%) ing a 1 ppb
Site
State County tion (ppb) Threshold Threshold Threshold Threshold
80050002 CO Arapahoe
5.98
3.47
3.47
58.00%
58.00%
80350004 CO
Douglas
5.94
3.35
3.35
56.40%
56.40%
80590006 CO Jefferson
7.06
4.68
2.34
66.30%
33.10%
80590011 CO Jefferson
6.98
4.51
3.57
64.60%
51.10%
80690011 CO Larimer
6.33
3.48
2.6
55.00%
41.10%
46a
Appendix B
47a
Appendix B
In EPA’s proposed approval of prongs 1 and 2 of Arizona’s
ozone transport I-SIP for the 2008 ozone NAAQS, it stated
that a factor it considers in making a weight-of-evidence
determination “is the magnitude of ozone attributable to
transport from all upwind states collectively contributing
to the air quality problem.”13 EPA considered the total
contributions from all states that contributed to the
same receptors linked to Arizona, and concluded that
upwind state contributions were negligible “particularly
when compared to the relatively large contributions from
upwind states in the East.” EPA’s modeling update in
March 27, 2018, illustrates this disparity between upwind
contributions from states in the East versus the West. For
example, the modeling shows that upwind contributions
for one site in Connecticut were 44.24 ppb, 12 times as
much as the in-state contributions of 3.71 ppb.14 A site
in New York shows upwind contributions (30.68 ppb) are
more than double the in-state contributions (13.55 ppb).15
13. 81 Fed. Reg. 15203.
14. Site ID 90019003 in Connecticut.
15. Site ID 360810124 in New York.
2023 Average
DV (ppb)
69.3
71.1
71.3
70.9
71.2
In-State
Upwind State
Contribution Contribution
(ppb)
(ppb)
22.94
5.98
24.71
5.94
25.52
7.06
24.72
6.98
21.74
6.33
Table 3: Comparison of in-state contributions to upwind state contributions
Site
State County
80050002 CO Arapahoe
80350004 CO
Douglas
80590006 CO Jefferson
80590011 CO
Jefferson
80690011 CO
Larimer
2023
Maximum
DV (ppb)
71.3
73.2
73.7
73.9
73
48a
Appendix B
49a
Appendix B
In the West, however, in-state contributions are much more
significant, while upwind contributions are much smaller.
The highest collective contribution from upwind states to
any of the five previously listed receptors in Colorado (Site
80590006) is 7.06 ppb, while in-state contributions for the
same receptor are 25.52 ppb. Table 3 shows the same case
for the other Colorado sites. Because of the difference
in magnitude between Colorado’s in-state contributions
and Utah’s modeled contributions to the five identified
receptors, Utah considers its contributions negligible.
Non-Anthropogenic and International Emissions
Consideration of non-anthropogenic and international
contributions is identified as a flexibility under Step 3 in
EPA’s March memo. Attachment C of that memo contains
modeled contributions for Canada/Mexico, offshore, fire,
biogenic, and initial/boundary conditions. While this
flexibility is intended for step 3, it is still worth addressing
here to illustrate the magnitude of these emissions
compared to those modeled as coming from Utah. Table
4 shows the uncontrollable emissions from Canada/
Mexico, Offshore, Fire, and Biogenic emissions and the
Initial/Boundary Conditions at each modeled receptor in
the Denver NAA comprise over 50 percent of emissions
at those sites. Ozone precursors from biogenics alone
contribute 4.19 to 5.71 ppb to the Colorado receptors. By
comparison, Utah’s contribution ranges from 0.83 to 1.23
ppb, or approximately one-quarter the contribution of
biogenics.
Table 4: Contributions from Canada/Mexico, Offshore, Fire, and Biogenic emissions
and the Initial/Boundary Conditions to Colorado receptor sites
* Includes contributions from Canada/Mexico, Offshore, Fire, and Biogenic sources
NonInitial
Total
U.S./Non
and
Uncon2023 Max- Anthro- Boundary trollable Percent
imum DV pogenic* Condi- Contribu- of MaxiSite
State County
(ppb)
(ppb)
tions
tion (ppb) mum DV
80050002 CO Arapahoe
71.3
5.39
34.84
40.23
56%
80350004 CO
Douglas
73.2
5.53
34.74
40.27
55%
80590006 CO Jefferson
73.7
7.13
31.41
38.54
52%
80590011 CO Jefferson
73.9
6.05
32.96
39.01
53%
80690011 CO
Larimer
73
8.42
34.54
42.96
59%
50a
Appendix B
51a
Appendix B
Consider ing the deg rees to which in-state, nonanthropogenic, and international emissions contribute
to each of the previously listed receptors, the DAQ
determines that it is unnecessary to consider step 3 in
this analysis, which involves identifying the emissions
reductions necessary to prevent contributions to
downwind air quality problems.
Emissions Reductions from Existing Regulations
EWPA’s contribution modeling for interstate ozone
transport relied on a 2011 base emission year Since
2011, Utah’s emissions have decreased significantly. This
decrease in emissions is a result of permitting actions
and regulatory requirements. Based on DAQ’s statewide
inventories Volatile Organic Compounds (VOCs) were
reduced by 30% (59,353 tpy) and NOx was reduced by 37%
(88,973 tpy) between 2011 and 2017. While Utah is unable
to require controls for mobile sources, it is expected that
regulations such as the Tier 3 Vehicle Emissions and
Fuel Standards will reduce emissions from these sources
nationally. DAQ expects additional reductions beyond 2017
as adopted air quality rules listed below become fully
implemented by the sources.
As part of a SIP for the Salt Lake City, UT PM 2.5
Nonattainment area, the Utah Air Quality Board amended
numerous area source rules to comply with Best Available
Control Technology (BACT) requirements. Three of the
rules apply statewide. The rules and their subsequent
emissions reductions by 2020 are shown in Table 3.
Overall, the emissions reductions from these rules are
projected to be 1,440 tons/year of NOx and 5,624 tons/
year of VOCs by 2020.
52a
Appendix B
Rule
Number
R307208*
R307221*
R307230*
R307302
R307303
R307304 &
R307335
R307342
Rule Name
Utah Air
Quality
Board
Final
Adoption
Date
Emissions
Reduced in
Pounds Per Day
(lb/day) by 2020
NOx
VOC
Outdoor Wood
10-AprBoilers
2013
5.8
186
Emission
Standard:
Emission Controls for Existing
Municipal Solid
8-FebWaste Landfills
2008
0
299.37
NOx Emission
Limits for
Natural GasFired Water
Heaters
3-Aug-2017 1,632.52
0
Solid Fuel
Burning Devices 1-Feb-2017 1,327.61 10,311.50
Commercial
15-DecCooking
2015
0
54.29
Industrial
6-Dec-2017
Solvent Use and & 29-OctDegreasing
2017
Adhesive and
Sealants
1-Dec-2014
0
1,527.89
0
1,533.71
53a
Appendix B
R307343
R307344
R307345
Emissions Standards for Wood
Furniture Manufacturing Operations
6-Dec-2017
Paper, Film &
Foil Coating
6-Dec-2017
Fabric & Vinyl
Coating
6-Dec-2017
R307346
Metal Furniture
Surface Coating 6-Dec-2017
R307347
R307348
R307349
Large Appliance
Surface Coating 6-Dec-2017
Magnet Wire
Coating
6-Dec-2017
Flat Wood Panel
Coating
6-Dec-2017
Miscellaneous
Metal Parts &
Products Coating
6-Dec-2017
R307350
R307351
R307352
R307353
0
910.88
0
147.62
0
442.96
0
249.51
0
0.69
0
22.18
0
17.15
0
411.43
Graphic Arts
6-Dec-2017
0
1,062.39
Metal Containers, Closure &
Coil Coating
Plastic Parts
Coating
6-Dec-2017
0
125
6-Dec-2017
0
222.41
54a
Appendix B
R307354
R307355
R307356
R307357
R307361
Auto body
refinishing
6-Dec-2017
0
1,817.76
Control of
Emissions from
Aerospace
Manufacture
& Rework
8-MarFacilities
2018
0
43.13
Appliance Pilot
Light
1-Jan-2013 4,926.20 361.78
Consumer
8-MayProducts
2014
0
4,625.34
Architectural
31-OctCoatings
2013
0
6,441.84
Total Emissions Reduced:
(lb/day) 7,892.10 30,814.80
* Rule applies statewide
Table 5: Area source rules approved by the Utah Air
Quality Board
On April 28, 2017, the EPA Administrator signed a final
action to reclassify the Salt Lake PM2.5 nonattainment
area from Moderate to Serious for the 2006 24-hour PM2.5
NAAQS. As required, the Utah Division of Air Quality
completed a BACT analysis for point source emissions.
Sources that emit 70 tons per year (tpy) or more of PM2.5
or any PM2.5 precursors—nitrogen oxides (NOx), volatile
organic compounds (VOCs), sulfur dioxide (SO2), and
ammonia—were subject to BACT. In addition, sources
that met or exceeded the 70 tpy threshold for a single
55a
Appendix B
precursor were reclassified as major sources subject to
Title V permit regulations. Under the Serious Area SIP
requirements, point sources underwent an updated review
of control techniques to ensure all controls met BACT.
DAQ identified best available controls to limit emissions of
direct PM2.5, NOx, SO2 and VOCs, and drafted new permit
limits based upon those controls and control techniques.
DAQ identified 26 stationary point sources that met or
meet the threshold of 70 tons or more per year for PM2.5
or any precursor. The actual emission limits and operating
procedures that reflect the implementation of BACM/
BACT are included Utah’s SIP Subsection IX. Part H,
11 & 12, which is made enforceable via incorporation into
the Utah Air Quality Rules in R307-110-17. The Utah Air
Quality Board adopted this SIP section and rule January
2, 2019.
Eight rules related to oil and gas sources were approved
by the Utah Air Quality Board in 2018 and 2019. The
purpose of these rules was to increase compliance with
existing BACT standards in the State. Under Utah’s
previous rules, compliance officers were unable to inspect
oil and gas sources unless they had a permit. A change
to permit-by-rule (PBR) regulations required all oil
and gas facilities, regardless of size, to register with
the state. Facilities emitting more than five tons of any
criteria pollutant must comply with BACT requirements.
Some rules, such as R307- 504, are a requirement for
all operations. Inspections have increased by 46% since
approval of the PBR regulations. Leaks are detected at
approximately 70% of the inspected sites. Of the leaks
56a
Appendix B
detected, 95% are repaired within 15 days. The increased
inspection and compliance has decreased NOx and VOC
emissions from oil and gas sources. While the rules are
not currently incorporated into Utah’s SIP, they will be
incorported into a SIP and submitted to EPA by spring
2020. The rules, and their effective dates, are shown in
Table 5.
Rule Number
R307-504
R307-505
R307-506
R307-507
R307-508
R307-509
R307-510
R307-511
Rule Name
Tank Truck
Loading
(amended to add
controls for tank
truck loading)
Registration
Requirements
(new rule)
Storage Vessel
(new rule)
Dehydrators
(new rule)
VOC Control
Devices (new
rule)
Leak Detection
and Repair
Requirements
Natural
Gas Engine
Requirements
Associated Gas
Flaring
Effective Date
March 1, 2109
March 1, 2109
March 1, 2109
March 1, 2109
March 1, 2109
March 1, 2109
March 1, 2109
March 5, 2109
57a
Appendix B
Table 6: Oil and Gas Sector Rules to reduce NOx and
VOC emissions
Requiring additional emissions reductions under steps
three and four of the 4-step analysis framework is not
necessary because of emissions reductions already
achieved since the 2011 base year and anticipated future
reductions.
Assessment
The evidence presented above demonstrates that
interstate transport I-SIP for the 2015 8-hour ozone
NAAQS contains provisions that meet the requirements of
CAA section 110(a)(2)(D)(i)(I). The combined information
contained in this weight-of-evidence analysis shows that
emissions from Utah do not contribute to nonattainment
or interfere with maintenance of the 2015 8-hour ozone
NAAQS in the Denver NAA in Colorado. NOx and VOC
emissions have decreased in Utah since 2011 through a
combination of regulatory and permitting actions. The
EPA’s modeling also shows that contributions from Utah
are not significant when considering the total emission
contributions from all upwind states and the contributions
from within the state of Colorado. These pieces of evidence
demonstrate that Utah
nor contributing
to the interference of maintenance of the NAAQS in
downwind states.
58a
Appendix C SUBMITTED BY
APPENDIX C — COMMENT
UTAH DEPARTMENT OF ENVIRONMENTAL
QUALITY (EPA-R08-OAR-2022-0315-0011),
DATED JULY 25, 2022
STATE OF UTAH
Spencer J. Cox
Governor
Deidre Henderson
Lieutenant Governor
July 22, 2022
Department of
Environmental Quality
K imberly D. Shelley
Executive Director
Division of A ir Quality
Bryce C. Bird
Director
DAQP-065-22
Kathleen Becker, Administrator
U.S. Environmental Protection Agency
EPA Docket Center, OAR,
Docket EPA-R08-OAR-2022-0315
Mail Code 28221T, 1200 Pennsylvania Avenue NW
Washington, DC 20460
[submitted electronically through www.regulations.gov]
Re: Docket ID No. EPA-R08-OAR-2022-0315, Air Plan
Disapproval; Utah; Interstate Transport of Air
Pollution for the 2015 8-Hour Ozone National Ambient
Air Quality Standard
Dear Administrator Becker,
Thank you for considering comments from the Utah
Division of Air Quality (UDAQ) regarding the proposed
59a
Appendix C
disapproval of Utah’s 2015 ozone standard interstate
transport State Implementation Plan (SIP). The UDAQ
appreciates the opportunity to provide specific comments
on the significant proposed action of disapproving
Utah’s SIP revision. On June 22, 2022, UDAQ submitted
comments on EPA’s proposed Federal Implementation
Plan (FIP) Addressing Regional Ozone Transport for the
2015 National Ambient Air Quality Standard (NAAQS)
(EPA-HQ-OAR-2021-0668).1 Given the link between these
two proposed actions, our comments here are similar in
nature. As requested in our comments on the proposed
FIP, given the overlapping time periods for public
commenting on both actions coupled with the technical
complexity of each, Utah requests a 60-day extension
to the current comment period, allowing the state until
September 23, 2022, to provide further analysis and
comments.
The UDAQ disagrees with EPA’s disapproval of the SIP
for the following reasons. First, through coordination
with EPA Region 8, UDAQ developed and submitted
what the agency thought to be a fully approvable SIP that
met EPA’s guidance and requirements at the time. The
EPA’s change of position at these late stages of the SIP
process wastes the state’s resources and time devoted to
this rulemaking. Second, the proposed disapproval relies
heavily on modeling results that were unavailable to the
state during the development of the SIP. Third, UDAQ
thinks that EPA's proposed rule to disapprove Utah's
1. Comment submitted by Utah Department of Environmental
Quality (UDAQ); June 22, 2022. DAQP-055-22, EPA docket ID
number EPA-HQ-OAR-2021-0668-0436.
60a
Appendix C
SIP is not rooted in the technically accurate analysis but
instead is motivated by the desire to include Utah in the
proposed interstate transport FIP. Fourth, UDAQ thinks
that the modeling and logic justifying Utah’s inclusion
in the proposed FIP are flawed. Lastly, we note regionspecific challenges in regulating ozone pollution, which
underscore a need for stronger cooperation between Utah
and EPA.
EPA’s Proposed Disapproval Goes Against the
Principles of Cooperative Federalism
Prior to this proposed disapproval, UDAQ was successful
in implementing the requirements of the Clean Air Act
(CAA) by working closely with our co-regulatory partners
at EPA’s Region 8 office, as envisioned by the principles
of cooperative federalism. This close working relationship
directly contributed to significant recent achievements
including reducing ambient PM 2.5 concentrations and
allowing all three of Utah’s PM 2.5 nonattainment areas
to reach attainment by the attainment date for the
current NAAQS. As the state regulatory agency, UDAQ
understands the nuances of our airsheds and the people’s
priorities, and can create state implementation plans that
are best for Utah. The benefit of cooperative federalism is
having the autonomy to do what’s best for the state, but
do so in partnership with EPA to ensure that the CAA
intent and requirements are met.
In this same spirit, UDAQ engaged early and often with
our counterparts at Region 8 in the development of our
interstate transport SIP. Through this collaboration and
61a
Appendix C
EPA’s guidance2 , Utah selected the alternative threshold
of 1 ppb. As noted in the guidance, the use of an alternative
threshold provides greater flexibility to states while SIPs
are developed. 3 Specifically, the guidance states that “a
threshold of 1 ppb may be appropriate for states to use
to develop SIP revisions addressing the good neighbor
provision for the 2015 ozone NAAQS”, since “the amount of
upwind collective contribution captured with the 1 percent
and 1 ppb threshold is generally comparable overall.”4
Thus, UDAQ was surprised when EPA proposed to include
Utah in the proposed FIP, and subsequently disapproved
the state’s SIP based in large part on the selection of the
1 ppb over the 1% of the NAAQS threshold. If the 1 ppb
threshold was in fact inappropriate for the development
of this SIP, EPA should have communicated that view to
UDAQ during the early engagement and development
process or during the state’s public comment period.
Additionally, EPA released no new guidance directing
states to use a 1% threshold either prior to or after SIP
submittal deadlines.
The EPA’s decision to change the acceptable criteria after
the development and submission of SIPs, and to do so
with no additional guidance, puts states in the difficult
2. Memorandum: Analysis of Contribution Thresholds
for Use in Clean Air Act Section 110(a)(2)(D)(i)(I) Interstate
Transport State Implementation Plan Submissions for the 2015
Ozone National Ambient Air Quality Standards (Contribution
Thresholds Memo). August 31, 2018.
3. See id. at 2.
4. Id. at 4.
62a
Appendix C
position of trying to plan with a moving set of criteria.
This whipsaw approach inevitably results in wasted state
time and resources. It has become apparent to UDAQ that
working closely with our EPA region has no bearing on the
outcome of some of EPA’s final regulatory actions and is
inconsistent with principles of cooperative federalism. As
mentioned in Utah’s FIP comments, UDAQ respectfully
requests EPA to consider ways to align its agency more
efficiently so that the policy priorities of the current
administration better align with the implementation and
timing of CAA requirements at the regional and state
level.
EPA’s Proposed Disapproval Relies on the Modeling
Results That Were Unavailable During the SIP
Development
The EPA indicates that its proposed decision to disapprove
Utah’s SIP relies heavily on using the updated modeling
platform 2016v2. The EPA explains that “by using the
updated modeling results, the EPA is using the most
current and technically appropriate information for
this proposed rulemaking.”5 However, as EPA knows,
these results were not available to the states during the
development and submittal of the interstate transport
SIPs. Because SIP planning is a lengthy process, it
is unacceptable for EPA to use modeling results for
their rulemaking that were developed after state SIP
preparation. As with all planning, SIP revisions are a
representation of the best available data and modeling
5. 87 Fed. Reg. 31,470, 31,472 (May 24, 2022).
63a
Appendix C
at that time. Using results from a modeling effort that
post-dated the states’ SIP development period is an
additional example of EPA changing expectations without
issuing appropriate and timely guidance. By relying
on modeling results not available during the time of
state SIP development, EPA is setting a precedent that
creates significant uncertainty for any planning effort,
further eroding the trust required for effective state and
federal cooperation. This is clearly inconsistent with the
cooperative federalism structure of the CAA.
EPA’s Proposed Disapproval is Motivated by the Desire
to Include Utah in the FIP
Upon review, UDAQ finds the timing and sequence of
the proposed actions in question to be highly irregular
compared to a traditional rulemaking process. The fact
that EPA proposed to include Utah in the broad and highly
impactful FIP prior to issuing proposed disapproval of
the state’s SIP is unusual. This may suggest that EPA’s
proposed SIP disapproval aims to regulate a select set
of point sources by including Utah in the proposed FIP.
EPA’s Inclusion of Utah in the FIP Relies on Flawed
Logic
As noted above and outlined in our comments related
to the proposed FIP, UDAQ believes that the proposed
disapproval of Utah’s SIP is an effort to fulfill an agenda
outside of the original intent of the interstate transport
provisions of the CAA. Specifically, the intent is to force
Utah’s inclusion in the FIP to target emission reductions
64a
Appendix C
from fossil fuel-fired electric generating units (EGUs)
located in the state. The UDAQ has provided extensive
comments on the substantial limitations and problems
with the modeling used to justify the inclusion of Utah in
the proposed FIP. These limitations are significant and
include inappropriate modeling resolution, inadequate
modeling of atmospheric transport, significant negative
modeling bias, and a likely misrepresentation of the
atmospheric chemical regime as a result of issues with
the inventories used.
Beyond these limitations, EPA concedes that the estimates
for air quality impacts for emission sources were conducted
using an inferior method, in direct conflict with EPA’s own
modeling guidance. As EPA states in its own technical
support document, “Air quality modeling would be the
optimal way to estimate the air quality impacts at each
cost threshold level from EGUs and non-EGUs emissions
reductions. However, due to time and resource limitations
EPA was unable to use photochemical air quality modeling
for all but a few emissions scenarios. Therefore, in order
to estimate the air quality impacts for the various levels
of emission reductions and to ensure that each step of its
analysis is informed by the evolving emissions data, EPA
used a simplified air quality assessment tool (AQAT).”6
Given that the modeling used as the justification for the
inclusion of Utah in the proposed FIP is not technically
6. Technical Support Document (TSD) for the proposed
Federal Implementation Plan Addressing Regional Ozone
Transport for the 2015 Ozone National Ambient Air Quality
Standard. Ozone Transport Policy Analysis. Docket ID No. EPAHQ-OAR-2021-0668.
65a
Appendix C
sound, EPA should have not included Utah in the FIP and
proposed to approve the state’s SIP instead.
Regionally-Specific Ozone Challenges
The UDAQ would also like to note the exceptional
challenges of reducing ozone in the Western United
States. States in the West face significant and regionallyspecific challenges in meeting ozone standards including
elevated natural background ozone levels,7 increasing
instances of wildfire, 8 significant biogenic contributions,9
as well as the influence of internationally transported
pollutants.10 Beyond these regionally-specific challenges, a
significant portion of the emissions of Oxides of Nitrogen
(NOx) in Utah comes from mobile sources, an area over
which the State has limited regulatory authority. These
combined regionally-specific challenges paired with the
fact that a substantial portion of emissions is under federal
7. Scientific Assessment of background ozone over the U.S.:
Implications for air quality management
8. Buchholz, R.R., Park, M., Worden, H.M. et al. New
seasonal pattern of pollution emerges from changing North
American wildfires. Nature Communications 13, 2043 (2022).
https://doi.org/10.1038/s41467-022-29623-8
9. EPA Webinar; Description and preliminary evaluation of
BELD 6 and BEIS 4. ORD. Jesse O. Bash and Jeff Vukovich
10. Entrainment of stratospheric air and Asian pollution by
the convective boundary layer in the southwestern U.S.; Langford,
A.O. et al. (2017), J. Geophysics. Res. Atmos., 122, 1312-1337,
doi:10.1002/2016JD025987
66a
Appendix C
jurisdiction make successful ozone reductions exceedingly
challenging, furthering the need for strong cooperative
federalism and active collaboration between our respective
agencies. The actions proposed by the EPA to deny
our SIP to fulfill a specific agenda undermine the trust
required for successful cooperative federalism, which only
serves to further complicate the shared goals of reducing
ozone concentrations and protecting public health.
Conclusion
For the reasons outlined in these comments, as well as
those submitted in opposition to the proposed FIP, EPA
is acting in error when proposing the disapproval of the
SIP and UDAQ requests that EPA reconsider this action.
In direct collaboration with Region 8, and using the best
available modeling results and guidance available at the
time, Utah developed and submitted a fully approvable SIP.
By relying on data and modeling results not available to
the states at the time of the SIP planning, and by changing
the acceptable thresholds without issuing guidance in a
timely manner, EPA is setting the wrong precedent. It
is the precedent of changing the acceptance criteria for
a SIP after the plans have been submitted in an effort
to fulfill an agenda not aligned with the original intent
of the interstate transport provisions of the CAA. The
UDAQ is committed to the development and enforcement
of SIPs that meet all of the CAA requirements based on
the best available data and guidance and is committed to
doing so in the spirit of cooperative federalism with our
federal partners. However, the actions proposed in this
67a
Appendix C
disapproval actively work to erode the trust, built over
years of cooperation, which is required to fulfill these
obligations and collaboratively protect public health.
Sincerely,
/s/
Bryce C. Bird
Director
68a
Appendix DFROM COMMENT
APPENDIX D — EXCERPTS
SUBMITTED BY PACIFICORP
(EPA-R08-OAR-2022-0315-0014),
DATED JULY 25, 2022
PacifiCorp
1407 W. North Temple, STE 110
Salt Lake City, UT 8416
July 25, 2022
ATTN: Adam Clark
Air and Radiation Division
EPA, Region 8
Mailcode 8ARD-IO
1595 Wynkoop Street
Denver, Colorado, 80202-1129
telephone number: (303) 312-7104
email address: clark.adam@epa.gov.
Re: PacifiCorp Public Comments on EPA’s Proposed
Disapproval of Utah’s Ozone Transport Ozone SIP;
Docket ID No. EPA-R08-OAR-2022-0315
Dear Mr. Clark:
PacifiCorp submits these public comments in opposition
to the U.S. Environmental Protection Agency’s (“EPA’s”)
proposed disapproval of Utah’s State Implementation
Plan for the Interstate Transport of Air Pollution for
the 2015 8-Hour Ozone National Ambient Air Quality
(“Utah Ozone Transport SIP” or “Utah SIP”). EPA’s
proposed disapproval was published on May 24, 2022, at
87 Federal Register 31,470, in an action entitled “Air Plan
Disapproval; Utah; Interstate Transport of Air Pollution
for the 2015 8-Hour Ozone National Ambient Air Quality
Standards” (“Proposed Disapproval”).
69a
Appendix D
PacifiCorp supports reasonable, effective and achievable
regulation that complements its ability to deliver affordable
electric service safely and reliably to customers and endusers. The Proposed Disapproval does not meet these
criteria—in large part because EPA was compelled to
take action via a settlement agreement after neglecting to
respond to a number of State Implementation Plans (“SIPs”)
for the interstate transport of ozone under the Clean Air
Act’s (“CAA”) good neighbor provisions. The relevant ozone
standard was finalized in 2015, and Utah submitted a plan to
address its good neighbor obligations based on information
provided by EPA; but EPA took no action on that plan
for over 28 months until the Proposed Disapproval. In
addition, EPA did not follow the chronology required in the
CAA because it first proposed a federal implementation
plan (“Proposed FIP” or “FIP”) that included Utah before
proposing, let alone finalizing, the Utah SIP disapproval
necessary to issue the FIP. EPA’s delay and flawed process
inextricably ties the FIP to this Proposed Disapproval
and forecloses any opportunity for Utah to respond with
appropriate data or clarifications. After delaying action
for so long, imposing the Proposed FIP through the
flawed Proposed Disapproval falls short of a reasoned
and balanced approach to interstate ozone transport and,
instead, creates a one-size-fits-all approach that threatens
electric reliability in the western United States.
*
*
*
70a
Appendix D
reductions are surplus and the control equipment
installations are not necessary to meet the CA A
requirements. The only remaining nonattainment receptor
in 2026 (the NREL receptor) is not significantly impacted
by Utah sources. Utah has a 0.90 parts per billion (“ppb”)
ozone contribution to the NREL receptor in 2026 and,
as discussed above, this contribution is not a statistically
significant contribution and should not be considered
significant. By taking the Colorado reductions and the
more appropriate and representative Colorado modeling
of the impacted monitors into account, there is further
support that Utah does not have a significant impact on
these monitors and Utah’s SIP should be approved.
EPA should follow its long-standing practice of recognizing
home-state emission reductions in determining up-wind
state impacts on their air quality monitors. EPA followed
that approach in its 2021 Revised CSAPR Update Rule
and should do so now.
c.
EPA acted contrary to its Threshold Guidance
and procedural due process in the Proposed
Disapproval.
EPA’s Threshold Guidance provided states a pathway to
use a 1 ppb threshold for significant impacts on downwind
monitors. Utah and almost every other state followed this
pathway, but EPA has now changed its mind and rejects
the very pathway it opened for all of these states for
“policy reasons”.43 Utah relied on the Threshold Guidance
43. See 87 FR at 31,478.
71a
Appendix D
to justify using the 1 ppb threshold at Step 2 as a basis to
assert that Utah would not be linked to some projected
downwind nonattainment or maintenance receptors
and that other linkages were not significant given other
EPA-suggested considerations. 44 See Sub-Section II.d
below. In the Proposed Disapproval, EPA insists that
only a 1 percent (“%”) threshold, or 0.7 ppb, can be
used. EPA explains it has moved on from the positions it
stated in the August 2018 Threshold Guidance, and EPA
ultimately applies the 1%threshold to justify the Proposed
Disapproval.45 EPA should allow use of the 1 ppb threshold.
EPA ignores a significant EPA study supporting use
of the 1 ppb threshold. Admittedly, EPA determined
the one-percent threshold was appropriate when it first
adopted the original CSAPR rule. This was based on 2011
modeling analysis that compared a 5% threshold, a 1%
threshold, and 1/2% threshold.46 Based on this modeling
analysis, EPA concluded that the upwind capture rates
under the 1% and 1/2% threshold options were similar,
indicating that little benefit would be achieved with the
lower threshold. EPA did find that raising the threshold
44. Id.
45. See e.g. 87 FR at 31,479 (“ . . . us[ing] a 1 percent of
NAAQS approach ensures that as the NAAQS are revised and
made more stringent, an appropriate increase in stringency at
Step 2 occurs.”); (“. . . . These data were examined to determine if
Utah contributes at or above the threshold of 1 percent of the 2015
8-hour ozone NAAQS (0.70 ppb) to any downwind nonattainment
or maintenance receptor.”).
46. 76 FR 48,208, 48,237 (August 8, 2011).
72a
Appendix D
to 5% would leave too many upwind states and emission
sources unregulated.
EPA conducted further analysis in 2018 when it issued
the Threshold Guidance that re-analyzed the minimum
threshold using a tighter range of options and more upto-date modeling techniques and data. 47 Specifically,
EPA evaluated the difference in capture rates between
the previous threshold of 0.7 ppb (1%), a threshold of 1
ppb, and a threshold of 2 ppb. Like the 2011 analysis,
EPA’s 2018 analysis again concluded that the difference
between the two lower options—0.7 ppb and 1 ppb—was
minimal, while the higher threshold of 2 ppb left too
many emissions unregulated. As a result, EPA considered
capture rates at the 0.7 ppb and 1 ppb thresholds to be
generally comparable, and thus concluded that “it may
be reasonable and appropriate for states to use a 1 ppb
contribution threshold, as an alternative to a 1 percent
threshold,” in addressing interstate transport under the
CAA good neighbor provision.48 Notably, a threshold of
1 ppb is just 1.4% of the ozone standard of 70 ppb, and
therefore would round down to 1%.
47. EPA Memorandum, Analysis of Contribution Thresholds
for Use in Clean Air Act Section 110(a)(2)(D)(i)(I) Interstate
Transport State Implementation Plan Submissions for the 2015
Ozone National Ambient Air Quality Standards (Aug. 31, 2018)
(“Threshold Guidance”).
48. Id. at 4.
73a
Appendix D
i.
The fact that EPA’s new 1 ppb interpretation
runs contrary to 49 states’ understanding
signals error.
In the Proposed Disapproval EPA states:
Following receipt and review of 49 good
neighbor SIP submittals for the 2015 8-hour
ozone NA AQS, the EPA’s experience has
been that nearly every state that attempted
to rely on a 1 ppb threshold did not provide
sufficient information and analysis to support
a determination that an alternative threshold
was reasonable or appropriate for that state.49
The fact that nearly every state got it wrong is more an
indication that EPA changed course without notice than
that the states are unable to read and interpret EPA
guidance. While technically retaining the Threshold
Guidance, EPA proposes to disapprove numerous state
submissions that relied on the guidance, including Utah’s
SIP, claiming that those states should have somehow
done more analysis than EPA required in the memo,
and asserting without explanation that consistency is
needed across the country. This is an about face for
EPA, which clarified in a previous ozone rulemaking that
western states should not be treated the same as other
areas of the country because the different geography,
meteorology, background ozone levels, wildfire impacts
and stratospheric ozone events in the West necessitated
49. 87 FR at 31,478.
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case-by-case treatment . 50 To justify its about face, EPA
now claims that the Threshold Guidance may only be
relied on, even for high altitude western states like Utah,
50. See, e.g., National Ambient Air Quality Standards
for Ozone, 80 FR 65,292, 65,300 (Oct. 26, 2015) (“observational
and modeling analyses have concluded that O3 concentrations
in some locations in the U.S. on some days can be substantially
influenced by sources that cannot be addressed by domestic
control measures. In particular, certain high-elevation sites in
the western U.S. are impacted by a combination of non-U.S.
sources like international transport, or natural sources such as
stratospheric O3, and O3 originating from wildfire emissions.”);
Memorandum from Stephen D. Page, Director, OAQPS, EPA,
“Information on Interstate Transport ‘Good Neighbor’ Provision
for the 2008 Ozone National Ambient Air Quality Standards
(NAAQS) under Clean Air Act (CAA) Section 110(a)(2)(D)(i)
(I)” (January 22, 2014), at 4 (recommending ozone transport in
western states should be evaluated on a case-by-case basis);
CARB, California Infrastructure State Implementation Plan
(SIP) Revision, at 15, January 19, 2016 (finding that in contrast
to the East, ozone transport in the West has a much smaller
proportion of local emissions and that the larger states and
complex terrain in the West make modeling less accurate and
helpful); Lin M, Fiore AM, Cooper OR, Horowitz LW, Langford
AO, Levy H, et al., “Springtime high surface ozone events over
the western United States: quantifying the role of stratospheric
intrusions,” J Geophys Res. 2012; 1 17:D00V22; Lefohn AS,
Wernli H, Shadwick D, Oltmans SJ, Shapiro M., Quantifying the
importance of stratospheric-tropospheric transport on surface
ozone concentrations at high- and low-elevation monitoring sites in
the United States. Atmos Environ. 2012;62:646-656; Lefohn AS,
Wernli H, Shadwick D, Limbach S, Oltmans SJ, Shapiro M., The
importance of stratospheric-tropospheric transport in affecting
surface ozone concentrations in the western and northern tier of
the United States. Atmos Environ. 2011;45:4845-4857.
75a
Appendix D
when a state meets its new, unannounced standards
by providing “a technically sound assessment of the
appropriateness of using this alternative threshold based
on the facts and circumstances underlying its application
in the particular SIP submission.”51 EPA’s new demand for
the states to provide a technical analysis to support the
use of the 1 ppb threshold identified in the August 2018
Threshold Guidance is inconsistent with EPA’s earlier
communications with Utah (and other states) and with
the stated purpose of the Threshold Guidance, which was
to “provide analytical information” and to allow states to
use that “information to make recommendations about
what thresholds may be appropriate for use” in SIPs. 52
EPA is essentially punishing Utah and almost all other
states for using the “recommendation” that EPA made in
the Threshold Guidance.
Like so many states, Utah used the 1 ppb threshold in its
Interstate Transport Ozone SIP. In fact, EPA commented
on Utah’s use of the 1 ppb threshold and recommended
that it rely on the Threshold Guidance to do so. In EPA’s
comments on Utah’s SIP during the state rulemaking
process, EPA instructed: “[g]iven that the draft analysis
makes use of the 1 ppb threshold, the EPA recommends
the state review the August 31, 2018 Memo and the
associated rationale for the use of this threshold.”53 Utah
51. 87 FR at 31,474.
52. August 2018 Threshold Guidance at 1.
53. See EPA Preliminary Comments on Utah’s Draft
2 015 Ozone In f ra st r uctu re Subm itt a l, at 2 , EPA-R0 8 OAR-2022-0314-003, found at regulations.gov.
76a
Appendix D
did just that, providing analysis in its SIP based on the
August 2018 Threshold Guidance and supporting the use
of the 1 ppb threshold with data and analysis. 54 Utah and
the numerous other states were not acting unreasonably
to rely on EPA’s Threshold Guidance, particularly when
EPA published the Threshold Guidance for that very
purpose during the very time states were drafting their
SIPs. EPA was aware of Utah’s reliance on the Threshold
Guidance, and provided direction to Utah supporting its
use of the Threshold Guidance.
Despite the fact that the Threshold Guidance was based
on the same principles as EPA’s 2011 analysis and was
improved through use of a tighter range of options and
more current data and modeling, EPA now all but disavows
it. 55 Moreover, EPA is proposing to disapprove of Utah’s
use of an alternative 1 ppb threshold in part due to EPA’s
determination that use of an alternative threshold “may
be impractical or otherwise inadvisable for a number
of additional policy reasons.” 56 Under the appliable
requirements of the CAA, changing policy reasons play
no part in authorizing EPA to disapprove a SIP.
Pacif iCorp asks EPA to reconsider its minimum
contribution threshold because EPA has not identified
54. See October 23, 2019, State of Utah 119(a)(2) SIP
In f ra st r uctu re Element s for Ozone , at 7- 8 , EPA-R0 8 OAR-2022-0314-007, found at regulations.gov.
55. See e.g., 87 FR at 31,478 (“The EPA views the 1 percent
of NAAQS threshold as the more appropriate threshold. . . .”).
56. See 87 FR at 31,478.
77a
Appendix D
any rational basis for preferring its older—and now
superseded—2011 analysis. The 2018 analysis is superior
and more appropriate for both identifying significant
contributions and avoiding the likelihood of over-control.
EPA should not disapprove Utah’s Interstate Transport
Ozone SIP based on an unfounded requirement to only
use the 1 percent threshold.
i.
EPA’s new “after-the-fact” standard on a 1
ppb threshold is arbitrary and capricious.
While EPA may claim some deference for its decisionmaking, it is not unlimited. EPA cannot act in a manner
that is inconsistent with the authorizing statute or that is
arbitrary and capricious. 57 The agency must “articulate
. . . a rational connection between the facts found and
the choice made.”58 Particularly applicable here, when
an agency’s “new policy rests upon factual findings that
contradict those which underlay its prior policy, or when
its prior policy has engendered serious reliance interests,”
the Administrative Procedure Act requires an agency to
provide “a more detailed justification” than it otherwise
would.59 Here, Utah and other states undoubtedly relied on
the Threshold Guidance and “engendered serious reliance
interests.” EPA acknowledges as much in the Proposed
57. See 5 U.S.C. 706(2)(A).
58. See Motor Vehicle Mfrs. Ass’n of U.S., Inc. v. State Farm
Mut. Auto. Ins. Co., 463 U.S. 29, 43 (1983).
59. See FCC v. Fox Television Stations, Inc., 556 U.S. 502,
515 (2009).
78a
Appendix D
Disapproval.60 EPA’s failure to acknowledge and account
for Utah’s “reliance interests” renders its Proposed
Disapproval both arbitrary and capricious.
ii.
EPA’s insistence on a 1 percent threshold is
not based on sound reasoning or science.
EPA engaged in robust statistical analysis in other
guidance that defined a Significant Impact Level (“SIL”)
for ozone to be used as part of the Prevention of Significant
Deterioration (“PSD”) permitting process (setting it at
1 ppb) (“SILs Memo”).61 The purpose of the SILs Memo
was to
*
*
*
60. See 87 FR at 31,472.
61. Guidance on Significant Impact Levels for Ozone and Fine
Particles in the Prevention of Significant Deterioration Permitting
Program. Memorandum from Peter Tsirigotis, Director, EPA
*
*
*
79a
Appendix D
BHE COMMENTS ON THE PROPOSED
INTERSTATE OZONE TRANSPORT RULE
EPA has presented the Proposed Rule as its best effort
to implement the good neighbor provision of the Clean
Air Act by adopting additional regulations to eliminate
upwind contributions to nonattainment and interference
with maintenance of the 2015 ozone standard in downwind
states. While BHE appreciates these efforts, BHE
believes that EPA’s Proposed Rule goes too far, too
fast, and imposes a program on western states that is
not designed for them. BHE has identified significant
concerns with the Proposed Rule and suggests potential
solutions that would remedy those concerns and lead to
a more reasonable, effective and achievable final rule
that addresses the interstate transport of ozone while
preserving the reliability of the bulk electric system
and delivering a just and orderly transition for affected
communities and western states.
I.
Western States Should Be Removed from the
Proposed Ozone Transport Rule.
EPA’s attempt to incorporate western states into the
Proposed Rule is a poor fit that is based on flawed
modeling. The compliance timeline in the Proposed Rule
severely limits compliance alternatives for affected EGUs,
especially in the West. Installation of selective catalytic
reduction (SCR) technology cannot be achieved at the
scale and timing required by the Proposed Rule. Further,
EPA has proposed restrictions and limitations on the NOX
allowance trading program that severely restrict, if not
80a
Appendix D
eliminate, market opportunities to achieve compliance.
Consequently, the Proposed Rule sets the stage for early
coal-unit retirements that will undermine the reliability
of the bulk electric system and adversely impact affected
coal communities as well as customers and electricity
consumers in the West.
After evaluating the Proposed Rule and its impacts on both
EGUs and non-EGUs, BHE has concluded that EPA’s basis
for including western states in the rule is inadequately
supported and that the costs and other negative impacts
of including these states will far outweigh the benefits
of pulling them into the proposal. The Proposed Rule
does not recognize the unique scientific considerations
underpinning ozone transport in the West. Nor does
it account for the significant uncertainty and learning
curve for sources in states that have not historically been
regulated under federal NOX allowance trading programs.
These sources must invest substantial time and effort to
prepare for compliance in only 11 months with a rule still
in its formative stage (and even less time than that once
the rule is finalized). Most importantly, BHE’s analysis
indicates that the stringency and timeline of the rule will
introduce catastrophic reliability risk in western states
where there are numerous affected sources that do not
currently have the kinds of controls EPA has deemed
cost-effective in its proposal. As a result, the Proposed
Rule lays out a path for potentially disastrous reliability
events for the West.
Finally, BHE is deeply concerned about applying the
pre-determined, one-size-fits-all CSAPR approach to
81a
Appendix D
western states given the administrative process EPA has
employed. By proposing denial of SIPs in the western
states where BHE operates affected EGUs (Nevada,
Wyoming, and Utah) only after issuing a FIP that includes
these states, EPA seems to signal that the outcome has
been pre-determined. BHE believes states are best
positioned to provide the right solutions to ozone transport
and encourages EPA to follow the CAA procedures for
states, not EPA, to act as the primary decision makers on
how best to achieve the good neighbor provisions of the
2015 ozone NAAQS.
A.
CSAPR is Not Well-Designed for Western
States.
CSAPR is a longstanding regulatory program designed
to address interstate ozone transport in eastern states.
Now, for the first time, EPA proposes to expand CSAPR
to four western states, with Nevada, Utah, and Wyoming
included in the EGU trading program for the first time.
While CSAPR has been a good fit for eastern states and
has accomplished reductions in the transport of ozone
to downwind states, there are a number of reasons that
it does not make sense for EPA to pull western states
into the CSAPR regulatory scheme. BHE urges EPA to
reconsider inclusion of these states in the Proposed Rule.
As EPA is aware, the scientific underpinnings of ozone
formation and transport in the West are fundamentally
different from the East. First, background levels of
ozone in the West are higher, in some cases just below the
current 2015 ozone NAAQS of 70 parts per million (ppm).
82a
Appendix D
Some background ozone is naturally occurring due to
nonanthropogenic sources of ozone precursors, including
wildfires and stratospheric ozone intrusion, while some
of it is directly attributable to international transport.
Furthermore, in mountainous areas of the West, ozone
formation is often attributable to, and exacerbated by,
geographical and meteorological conditions, rather than
the industrial source emissions targeted by EPA’s ozone
transport rule.1
1. See, e.g., National Ambient Air Quality Standards for
Ozone, 80 FR 65,292, 65,300 (Oct. 26, 2015) (“observational
and modeling analyses have concluded that O3 concentrations
in some locations in the U.S. on some days can be substantially
influenced by sources that cannot be addressed by domestic
control measures. In particular, certain high-elevation sites in
the western U.S. are impacted by a combination of non-U.S.
sources like international transport, or natural sources such as
stratospheric O3, and O3 originating from wildfire emissions.”);
Memorandum from Stephen D. Page, Director, OAQPS, EPA,
“Information on Interstate Transport ‘Good Neighbor’ Provision
for the 2008 Ozone National Ambient Air Quality Standards
(NAAQS) under Clean Air Act (CAA) Section 1 10(a)(2)(D)(i)
(I)”, at 4, January 22, 2015 (recommending ozone transport in
western states should be evaluated on a case-by-case basis);
CARB, California Infrastructure State Implementation Plan
(SIP) Revision, at 15, January 19, 2016 (finding that in contrast
to the East, ozone transport in the West has a much smaller
proportion of local emissions and that the larger states and
complex terrain in the West make modeling less accurate and
helpful); Lin M, Fiore AM, Cooper OR, Horowitz LW, Langford
AO, Levy H, et al., “Springtime high surface ozone events over
the western United States: quantifying the role of stratospheric
intrusions”, J Geophys Res. 2012; 1 17:D00V22; Lefohn AS,
Wernli H, Shadwick D, Oltmans SJ, Shapiro M., Quantifying the
importance of stratospheric-tropospheric transport on surface
ozone concentrations at high- and low-elevation monitoring sites in
83a
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Utah provided significant evidence, including preliminary
photochemical modeling results, of how these factors
influence ozone levels along the Northern Wasatch Front
area of Utah. 2,3 Even if EPA does not recognize Utah’s
exceptional event arguments, it is beyond dispute that
the ozone levels in western states are influenced by high
background levels and international emissions. EPA has
historically recognized the need to account for these
additional factors when evaluating western states and that
a case-by-case consideration of ozone impacts is necessary
in the West.4
Furthermore, EPA’s analysis and modeling in support of
the Proposed Rule are grounded in methods and data that
presume conditions in eastern states. 5 For example, EPA
conducted national-scale modeling using a 12-kilometer
the United States. Atmos Environ. 2012;62:646-656; Lefohn AS,
Wernli H, Shadwick D, Limbach S, Oltmans SJ, Shapiro M., The
importance of stratospheric-tropospheric transport in affecting
surface ozone concentrations in the western and northern tier of
the United States. Atmos Environ. 2011;45:4845-4857.
2. See Utah, Technical Support Document, Northern
Wasatch Front (NWF), Utah: Failure to Attain 2015 Ozone
National Ambient Air Quality Standard by Attainment Date;
Reclassification and Disapproval of International Emissions
Demonstration, January 2022, at 6-20.
3. See Memorandum from Barron Henderson and Heather
Simon (EPA, OAQPS) on Modeled U.S. and International
Contributions for 2015 Ozone NAAQS Nonattainment Areas
(December 10, 2021).
4. 81 FR 74504, 74506, EPA, Cross-State Air Pollution Rule
Update for the 2008 Ozone NAAQS, Oct. 26, 2016.
84a
Appendix D
(km) resolution grid. However, that grid is too coarse to
accurately model ozone in the mountainous western states
where PacifiCorp and NV Energy operate.6 This error
is one reason that states are better suited to determine
appropriate measures to address impacts on neighboring
states. The most recent Denver ozone SIP used a 4-km
grid to capture the meteorology and terrain more
accurately in the very areas EPA claims are impacted by
Utah and Wyoming.7 The Denver modeling shows that the
monitors EPA claims are significantly impacted by Utah
and Wyoming will achieve or make significant progress
towards attainment by 2026, without and before the most
stringent requirements for EGUs go into effect under the
Proposed Rule. 8
Unlike eastern states, which have been subject to both
CSAPR and its predecessor rules, the Clean Air Interstate
Rule (CAIR) and the NOX SIP Call, western states have
5. 81 FR 74504, 74523-24 (“EPA is not addressing interstate
emission transport in this action for the 11 western contiguous
United States. The CSAPR framework builds on previous easternfocused efforts to address collective contributions to interstate
transport . . . ”)
6. See Section I.B.
7. See 87 FR 20036, 27050, Federal Implementation Plan
Addressing Regional Ozone Transport for the 2015 Ozone National
Ambient Air Quality Standard (Apr. 6, 2022).
8. The problem of resolution is not solely a western state
problem, but it is particularly pronounced in the mountainous
western states where BHE businesses operate and where EPA
claims significant impacts are occurring.
85a
Appendix D
a tremendous uphill climb to prepare for participation
in a NOX allowance market. Affected sources in these
states face the requirement to install costly controls on
an infeasible timeline, involving significant decisions
that must be made before the rule is even finalized, and,
even then, will still have insufficient lead time. Under
the Proposed Rule, affected sources will have only a few
months to comply once the rule is finalized, and so must
start immediately to develop a compliance strategy and
facilitate the possible purchase and sale of allowances by
the 2023 ozone season. In addition, EPA forces utilities to
make decisions within an unreasonably short timeframe
about investments in fossil fuel retrofit technologies that
will have major ramifications on customer rates, reliability,
and system operations. The Proposed Rule simply does
not account for the fact that western states are beginning
at a very different starting point than states that have
historically been regulated for more than a decade under
interstate NOX trading schemes.
Finally, western states are already taking significant
regulatory actions that would accomplish the goals that
the ozone transport rule is designed to achieve. For
example, western states are identifying additional controls
for certain units under the Regional Haze program,
and various facilities in these states have committed to
cease burning coal or to retire coal units under the Clean
Water Act’s effluent limitations guidelines and Resource
Conservation and Recovery Act’s coal combustion
residuals programs.
86a
Appendix D
Ramboll—Evaluation of Utah and Wyoming Ozone
Contributions in EPA’s Proposed Good Neighbor Plan
for the 2015 Ozone NAAQS
4.5.1 Effects of Higher Resolution 4-km Grid in DM/
NFR SIP Modeling
The DM/NFR ozone NAA roughly corresponds to the
Front Range Urban Corridor that had a population
of approximately 5 million and includes the Denver
Metropolitan Statistical Area that had a population of
almost 3 million people in the 2020 census. The DM/
NFR ozone NAA also includes a portion of the DenverJulesburg (D-J) oil and gas (O&G) basin. The urban and
suburban areas and O&G production result in high density
NOX and VOC emissions in the DM/NFR NAA. Figure
4-3 displays the total NOX and VOC emissions at 4-km
resolution for the 2016 base case and differences between
the 2016 and 2023 base cases. The high density NOX and
VOC emissions in the DM/NFR NAA and D-J O&G basin
are clearly evident. In the CAMx model, emissions are
emitted into and instantaneously dispersed evenly across
the grid cell volume. In order to properly simulate ozone
formation in the DM/NFR NAA, a high resolution grid
cell size needs to be used. All of the Denver ozone SIPs in
the past have used a 4-km grid resolution to simulate the
correct meteorology and chemistry and resolve the urban
plumes so that the model has a chance to reproduce the
highest observed ozone concentrations. Use of a coarse 12km grid will instantaneously disperse emissions across a
grid cell volume that is almost an order magnitude larger
than when a 4-km grid size is used making it difficult for
87a
Appendix D
the model to reproduce the high observed ozone peaks
due to overdiluting the ozone concentrations and its
precursors.
Note that use of a coarse 12-km grid resolution will also
reduce ozone peaks due to local sources in the Upwind
State due to failure to resolve urban and other highly
concentrated ozone precursor emission sources (e.g.,
industrial facilities, O&G, etc.) and their resultant ozone
plumes. However, by the time the ozone and precursor
concentrations from the Upwind State travel 100s of miles
to the receptor in the downwind state the “plumes” will
be many 12-km grid cells across so that the effects of the
coarse resolution on underestimating ozone concentrations
at the receptor in the downwind state due to emissions in
the Upwind State is less important.
Figure 4-3. Total anthropogenic NOX (top) and VOC
(bottom) emissions (tons per day) within the CAMx
4-km Colorado domain used in the DM/NFR 2023
Severe/Moderate ozone SIP. Shown are emissions for
the 2016 base case (left) and differences between the
2023 and 2016 base cases (right) (Source: RAQC Ozone
Modeling Forum28).
28. https://ragc.egnyte.com/dl/kzR8aJm0zl/2022_Modeling_
Forum_-_2023_and_2026_Design_Value_Projections.pdf
88a
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89a
Appendix D
90a
Appendix D
4.5.2 Effects of Higher Resolved Meteorological
Inputs on Ozone Concentrations in the DM/NFR Ozone
SIP Modeling
Obtaining the correct depiction of meteorology is critically
important for simulating ozone formation in the complex
terrain conditions of the DM/NFR NAA. To better
understand this importance, we first discuss the conditions
that lead to the highest ozone concentrations in the DM/
NFR NAA.
4.5.2.1 Conceptual Model of Ozone Formation in the
DM/NFR NAA
The DM/NFR 2020 Serious ozone SIP for the 2008
ozone NAAQS (RAQC and CDPHE, 2020) included a
report “Conceptual Model of High Ozone for the Denver
Metro/North Front Range” (Ramboll, 2020). The highest
ozone concentrations in the DM/NFR NAA are due to a
combination of ozone transport and locally generated ozone
under specific meteorological regimes that favor ozone
photochemistry and limited dispersion. Reddy and Pfister
(2016) explored the relationships between meteorology and
ozone in the Rocky Mountain states and concluded that
increases in upper level high pressure strength “lead to
high July ozone in much of the western U.S., particularly
in areas of elevated terrain near urban sources with high
emissions of NO2 and other ozone precursors.” In addition
to bringing warmer temperatures, upper level ridges in
this region reduce westerly winds at the surface and aloft
to allow cyclic terrain-driven circulations that reduces
transport away from sources. This includes the formation
91a
Appendix D
of thermally driven upslope flows along the Front Range in
the DM/NFR NAA where ozone and ozone precursors are
transported up the slopes during the day and can return
at night to lower elevations in large scale basin drainage
(downslope) flows. Upper level ridges can also increase
background ozone concentrations within the ridge. Ozone
and NOX concentrations build locally, and deeper vertical
mixing in this region provides a potential mechanism for
recapture of ozone in layers aloft (e.g., from transport or
remnants of the previous days ozone) that are mixed down
to the surface.
The three key elements of a conceptual model for highconcentration ozone episodes along Colorado’s Front
Range are:
1. The presence of an upper-level high pressure
system or ridge.
2. Reduced westerly winds, especially during
the day.
3. Thermally-driven upslope flow towards
the Continental Divide during the day and
downslope drainage flows into the Platte
Valley at night. This diurnal cycle of winds
enhances the potential for the accumulation
of ozone precursors and ozone within the
region, especially when this cyclic pattern
recurs over a period of several days.
92a
Appendix D
4.5.2.2 Requirements for WRF Meteorological Model
to Reproduce DM/NFR NAA Ozone Conceptual Model
In order for the Weather Research and Forecasting (WRF)
meteorological model to reproduce the meteorological
conditions that lead to the highest ozone concentrations
in the DM/NFR NAA it needs to be able to simulate the
high pressure system/ridge and the thermally driven slope
flows. Getting the high pressure system or ridge correctly
requires using analysis fields used in the WRF initial and
boundary conditions (IC/BC) and four-dimensional data
assimilation (FDDA) inputs. Such analysis fields that
contain the presence of the high pressure/ridges include
the North American Mesoscale Forecast System (NAM 29)
analysis fields that were used in the WRF simulations to
develop the CAMx 2016 meteorological inputs for both the
DM/NFR 2023 Severe/Moderate ozone SIP and Proposed
Transport Rule CAMx 2016 modeling platforms.
For WRF to obtain an accurate depiction of the thermally
driven slope flows requires the terrain inputs for the
model to be representative of actual terrain. Figure 4-4
shows the terrain heights (meters above mean sea level,
MSL) using 12-km and 4-km grid resolutions. Use of a
12-km grid resolution smooths the terrain and greatly
reduces the terrain heights and the elevation differences
of the “slopes” of the terrain along the Front Range. The
slope between western Denver County to the continental
divide spans approximately 7,800 feet in elevation using
a 4-km grid resolution but only approximately 4,500
feet in elevation change using the 12-km grid resolution.
93a
Appendix D
Thus, WRF’s ability to reproduce the thermally driven
daytime upslope and nighttime downslope flows will be
severely compromised using a 12-km grid resolution
and simulated much more accurately using a 4-km grid
resolution because a 12-km grid resolution fails to resolve
the terrain in the region.
The higher resolution complex terrain in the 4-km
data, and in reality, will also affect transport of ozone
and precursors from Wyoming to the DM/NFR NAA
differently than if a 12-km grid resolution is used. The
higher variable wind fields from more highly resolved
terrain features will disperse ozone and precursors from
Wyoming as they are transported to the DM/NFR NAA
than if a 12-km grid resolution is used.
Figure 4-4. Representation of terrain (m MSL) over
Colorado using a 12-km grid resolution (top) and 4-km
grid resolution (bottom) (Note: domain is similar but
not the same as the DM/NFR ozone SIP CAMx 4-km
Colorado domain).
94a
Appendix D
95a
Appendix D
4.5.3 Comparison of CAMx Ozone Model Performance
and Its Implications
We conducted an ozone model performance of the CAMx
2016 base case simulation used in the Proposed Transport
Rule and compared it to the ozone performance of the
DM/NFR 2023 Severe/Moderate ozone SIP CAMx S17
2016 base case simulation. At this time, only limited
publicly available information is available on ozone model
performance for the DM/NFR ozone SIP CAMx S17 2016
base case from presentations given at the May 18, 2022
RAQC Ozone Modeling Forum. 30
Ozone model performance goals and criteria have been
established by Emery and co-workers (2016) for the
Normalized Mean Bias (NMB) and Normalized Mean
Error (NME) model performance metrics. The NMB
ozone model performance goal is ≤±5% and the NMB
ozone performance criterion is ≤±15%. The NME ozone
model performance goal and criterion are ≤15% and
≤25%, respectively.
Table 4-6 compare the NMB and NME performance
statistics for the CAMx 2016 base case simulations
performed as part of EPA’s Proposed Transport Rule and
as part of the DM/NFR 2023 Severe/Moderate ozone SIP.
NMB and NME performance statistics that achieve the
ozone model performance goals are colored green, and
those that fall between the performance goals and criteria
are colored yellow. The DM/NFR ozone SIP CAMx 2016
base case ozone performance is clearly performing better
30. https://raqc.org/event/2022-raqc-modeling-forum/
96a
Appendix D
than the EPA Proposed Transport Rule CAMx 2016 base
case at all four sites in the DM/NFR NAA. The EPA
CAMx 2016 base case exhibits an ozone underestimation
bias, which was expected given the coarse 12-km grid
resolution used. At CHAT, the Proposed Transport Rule
CAMx 2016 base case has an NMB underestimation of
-7.6% while the DM/NFR 2023 Severe/Moderate ozone
SIP has essentially zero bias (0.1%). The underestimation
bias in the Proposed Transport Rule CAMx 2016 base
case is even greater at the RFNO (-8.1%), NREL (-8.4%)
and FTCW (-12.5%) sites while the DM/NFR ozone SIP
CAMx 2016 base case bias achieves the bias performance
goal by a wide margin.
Table 4-6. Comparison of NMB and NME ozone
performance statistics (%) at the four key monitoring
sites in the DM/NFR NAA and the CAMx 2016 base
case simulations from EPA’s Proposed Transport Rule
and the DM/NFR Severe/Moderate ozone SIP. NMB/
NME performance statistics that meet the ozone model
performance goal are colored green.
EPA Proposed Rule
Site
CHAT
RFNO
NREL
FTCW
NMB
-7.6%
-8.1%
-8.4%
-12.5%
NME
11.6%
11.3%
11.9%
14.3%
DM/NFR Ozone
SIPa
NMB
NME
0.1%
9.2%
-0.4%
8.8%
-2.0%
8.6%
-2.5%
7.8%
a. Source: https://raqc.egnyte.com/dl/8AGJMMksXC/2022_
Modeling _Forum_-_ 2016_Base_Year_Modeling _Platform_
Updates.pdf_
97a
Appendix D
Ozone attainment/nonattainment is determined by the
ozone design value (DV) that is defined as the three-year
average of the fourth highest maximum daily average
8-hour (MDA8) ozone concentrations. Thus, how well
the model simulates the four highest observed MDA8
ozone concentrations is an important model performance
attribute. Table 4-7 compares the predicted and observed
four highest MDA8 ozone concentrations at Chatfield
during 2016 from the Proposed Transport Rule and
DM/NFR Severe/Moderate ozone SIP CAMx 2016 base
case simulations. The highest observed MDA8 ozone
concentration at Chatfield during 2016 was 86.6 ppb that
was underestimated by the Proposed Transport Rule
CAMx 2016 base case (74.9 ppb) by 11.7 ppb (-13.5%).
Whereas, the DM/NFR ozone SIP CAMx 2016 base case
highest estimated ozone concentration at Chatfield (86.4)
matched the observed value (86.6 ppb) almost exactly
(within 0.2 ppb or 0.0% difference). The fourth highest
observed MDA8 ozone concentration at Chatfield (78.0
ppb) is underestimated by the Proposed Transport Rule
CAMx 2016 base case (71.9 ppb) by 6.1 ppb (-7.8%), while
the DM/NFR ozone SIP CAMx base case fourth highest
ozone at Chatfield (78.1 ppb) matches the observed fourth
highest ozone very well (0.1 ppb and 0.0% difference).
98a
Appendix D
Table 4-7. Comparison of the observed and modeled
four highest MDA8 ozone concentrations at the
Chatfield monitoring site in 2016 for the EPA Proposed
Transport Rule and DM/NFR 2023 Severe/Moderate
ozone SIP CAMx 2016 base case simulations.
EPA Proposed
Observed
Transport Rule
Ozone
Ozone
Percent
(ppb)
(ppb) Difference
86.6
74.9
-13.5%
81.0
73.1
-9.8%
80.3
72.6
-9.6%
78.0
71.9
-7.8%
DM/NFR
Ozone SIPa
Ozone
Percent
(ppb) Difference
86.4
-0.2%
81.6
0.7%
80.1
-0.2%
78.1
0.1%
a. Source: https://raqc.egnyte.com/dl/8AGJMMksXC/2022_
Modeling _Forum_-_2016_Base_Year_Modeling _Platform_
Updates.pdf_
Table 4-8 compares the predicted and observed four
highest MDA8 ozone concentrations at the Rocky Flats
North (RFNO) monitoring site in the DM/NFR NAA
and the Proposed Transport Rule and DM/NFR Severe/
Moderate ozone SIP CAMx 2016 base case simulations.
The ozone under-prediction bias of the Proposed
Transport Rule CAMx 2016 base case at RFNO is even
greater than at CHAT with the four highest observed
ozone concentrations underestimated by -11% to -19%.
The DM/NFR ozone SIP CAMx 2016 base case also
underestimates the four highest observed MDA8 ozone
concentrations at RFNO but the underestimation bias
(-4% to -10%) is approximately half of the Proposed
99a
Appendix D
Transport Rule underestimation bias. For example, the
observed fourth highest MDA8 ozone at RFNO (79.5%) is
underestimated by the Proposed Transport Rule by -11%
(70.9 ppb) but is only underestimated by the DM/NFR
ozone SIP CAMx 2016 base case by -4% (76.3 ppb), which
achieves the ≤±5% ozone performance goal.
Table 4-8. Comparison of the observed and modeled
four highest MDA8 ozone concentrations at the Rocky
Flats North monitoring site in 2016 for the EPA
Proposed Transport Rule and DM/NFR 2023 Severe/
Moderate ozone SIP CAMx 2016 base case simulations.
EPA Proposed
Observed
Transport Rule
Ozone
Ozone
Percent
(ppb)
(ppb) Difference
89.6
72.9
-18.6%
82.4
72.7
-12.4%
81.6
72.6
-11.0%
79.5
70.9
-10.8%
DM/NFR
Ozone SIPa
Ozone
Percent
(ppb) Difference
81.1
-9.5%
77.8
-5.6%
77.5
-5.0%
76.3
-4.0%
a. Source: https://raqc.egnyte.com/dl/8AGJMMksXC/2022_
Modeling _Forum_-_2016_Base_Year_Modeling _Platform_
Updates.pdf_
The performance of the two CAMx 2016 base case
simulations in predicting the highest ozone concentrations
at NREL is shown in Table 4-9. Both CAMx 2016 base
cases exhibit an underestimation of the four highest
observed MDA8 ozone concentrations at NREL with the
Proposed Transport Rule underestimation (-11% to -13%)
100a
Appendix D
being worse than the DM/NFR ozone SIP CAMx 2016
base case (-6% to -10%).
Table 4-9. Comparison of the observed and modeled
four highest MDA8 ozone concentrations at the NREL
monitoring site in 2016 for the EPA Proposed Transport
Rule and DM/NFR 2023 Severe/Moderate ozone SIP
CAMx 2016 base case simulations.
EPA Proposed
Observed
Transport Rule
Ozone
Ozone
Percent
(ppb)
(ppb) Difference
88.6
78.0
-12.0%
86.3
74.3
-13.9%
83.3
74.1
-11.0%
83.3
73.8
-11.4%
DM/NFR
Ozone SIPa
Ozone
Percent
(ppb) Difference
81.3
-8.2%
80.3
-9.5%
78.3
-6.0%
76.1
-8.6%
a. Source: https://raqc.egnyte.com/dl/8AGJMMksXC/2022_
Modeling _Forum_-_2016_Base_Year_Modeling _Platform_
Updates.pdf_
4.6 Conclusions On Future Year Projected Ozone
Design Values at DM/NFR Nonattainment/Maintenance
Receptors
Based on scientific technical arguments, the coarse 12km grid resolution used in the Proposed Transport Rule
CAMx modeling will likely overstate future year design
value projections. This was confirmed by the DM/NFR
2023 Severe/Moderate ozone SIP CAMx 4-km grid
resolution modeling that produced lower future year
101a
Appendix D
projected design values resulting in Chatfield and Rocky
Flats North no longer being nonattainment/maintenance
receptors in 2026. As Chatfield was the only receptor
that Wyoming was linked to, the Proposed Transport
Rule overcontrols Wyoming emissions by proposing 2026
EGU and non-EGU control in Wyoming even though it
is not contributing to nonattainment or interfering in
maintenance of the 2015 ozone NAAQS at any receptor
in a downwind state.
Utah was linked to three receptors in the DM/NFR
NAA (CHAT, RFNO and NREL). Two of these receptors
(CHAT and RFNO) become attainment receptors based
on the refined DM/NFR Severe/Moderate ozone SIP
CAMx modeling, although NREL receptor remained
a nonattainment receptor in the DM/NFR ozone SIP
CAMx modeling (see Table 4-5). However, Utah has a 0.90
ppb ozone contribution to the NEWL receptor in 2026
and, as discussed in Chapter 7, this contribution is not a
statistically significant contribution to an ozone design
value. This argues that Utah should also not be subject
to the 2026 EGU and non-EGU controls in the Proposed
Transport Rule.
4.7
References
Emery, C.E., Z. Liu, A.G. Russell, M.T. Odman, G. Yarwood
and N. Kumar. 2016. Recommendations on statistics and
benchmarks to assess photochemical model performance.
J. of the Air and Waste Management Assoc., Vol. 67,
Issue 5. DOI: 10.1080/10962247.2016.1265027. (https://
www.tandfonline.com/doi/full/10.1080/10962247.2016.1
265027).
102a
Appendix D
EPA. 2022. Technical Support Document (TSD) for the
Proposed Federal Implementation Plan Addressing
Regional Ozone Transport for the 2015 Ozone National
Ambient Air Quality Standard. Docket ID No. EPAHQ-OAR-2021-0668. Ozone Transport Policy Analysis
Proposed Rule TSD. U.S. Environmental Protection
Agency, Office of Air and Radiation. February. (https://
www.epa.gov/system/files/documents/2022-03/ozonetransport-policyanalysis-proposed-rule-tsd.pdf ).
Ramboll. 2020. Conceptual Model of High Ozone for the
Denver Metro/North Front Range 2020 Serious Ozone
State Implementation Plan. Ramboll US Corporation,
Novato, CA. August. https://raqc.egnyte.com/dl /
FlJGHQ j2fI/DMN_FR_2020-O3SIP_Conceptual_
Model_Ozone_v6. pdf_
RAQC and CDPHE. 2020. Serious State Implementation
Plan for the Denver Metro and North Front Range
Ozone Nonattainment Area. Regional Air Quality
Council and Colorado Department of Health and
Environment, Denver, CO. Adopted by Colorado Air
Quality Control Commission December 18, 2020. (https://
raqc.egnyte.com/dl/g2nFZlaoLc/Ozone_SIP_Element__Adopted_121820%2BApdx12-C.pdf_).
Reddy, P.J. and G.G. Pfister. 2016. Meteorological
factors contributing to the interannual variability
of midsummer surface ozone in Colorado, Utah,
a nd ot her we st er n U. S . st at e s . J. Geo. Res .:
Atmospheres (JGR). 10.1002/2015JD023840. March.
103a
Appendix D
( ht t p s: //a g up u b s .on l i ne l i br a r y.w i ley. c o m /doi /
epdf/10.1002/2015JD023840).
5.0 UPWIND STATE OZONE CONTRIBUTIONS
AT D OW N W I N D STAT E R EC EP T OR S A R E
OVERSTATED
As described in detail in Chapter 1, an Upwind State 2023
and 2026 ozone contribution to an ozone design value at
a nonattainment/maintenance receptor in a downwind
State is based on the Contribution Factor (CF) that is
the ratio of the Upwind State MDA8 ozone contribution
to the receptor divided by the total MDA8 ozone at the
receptor averaged over the top 10 CAMx 2023 modeled
total MDA8 ozone days at the receptor. The Contribution
Factor is multiplied by the 2023 and 2026 average ozone
design value (Avg DV) to obtain the Upwind State 2023
and 2026 ozone contribution to the downwind receptor:
CF = ∑ UpwindState_Ozone / ∑ Total_Ozone
UpwindState_Ozone_Contribution =
CF x Ozone_AvgDV
Thus, any assumptions, errors or omissions that would
either: (1) increase the total MDA8 ozone concentrations
at the receptor (i.e., increase the denominator in CF);
or (2) reduce Upwind State’s ozone contribution at the
receptor (i.e., decrease the numerator in CF), would
reduce the Contribution Factor and the Upwind State’s
ozone contribution to the downwind receptor 2023 and
2026 ozone design values.
104a
Appendix D
5.1
Missing Emissions in Proposed Transport
Modeling Results in Overstating Utah’s and
Wyoming’s Ozone Contribution to Receptors in
the DM/NFR NAA
The Proposed Transport Rule CAMx modeling failed
to include NOX emissions from lightning (LNOX). This
is particularly important in the Front Range area of
Colorado where summer thunderstorms regularly occur.
Emissions from lightning can be a significant source of
NOX concentrations and resultant ozone formation. Zhang
and co-workers (2003) estimate that 5% of the annual
and 14% of the summer NOX emissions in the U.S. comes
from lightning. Kang and co-workers (2020) analyzed the
effects of including LNOX emissions and found they were
particularly important for simulating ozone in the U.S.
Mountain West States (MWS), which include Colorado,
Utah and Wyoming, and found LNOX emissions could
increase MDA8 ozone concentrations by up to 17 ppb and
concluded “summertime surface-level O3 levels in the
MWS region could be significantly influenced by lightning
NOX.” (Kang et al., 2020). If naturally occurring LNOX
emissions were included in the Proposed Transport Rule
CAMx modeling that would increase the total MDA8
ozone concentrations at the DM/NFR NAA receptors
resulting in a reduced Utah and Wyoming Contributions
Factors and lower Utah and Wyoming ozone contributions
to 2023 and 2026 ozone design values at the DM/NFR
NAA receptors.
EPA developed the 2016v2 modeling platform 2016, 2023,
2026 and 2032 model-ready emissions for the CMAQ
105a
Appendix D
model and converted them to the CAMx format using a
CMAQ2CAMx emissions converter. In doing the CMAQ
to CAMx emissions conversion for the Proposed Transport
Rule CAMx modeling, EPA dropped methane (CH4)
emissions and some secondary organic aerosol (SOA)
precursor species. The SOA precursors probably have
minimal effect on ozone formation but methane acts
*
*
*
106a
Appendix EFROM RESPONSE
APPENDIX E — EXCERPTS
TO COMMENTS DOCUMENT
(EPA-HQ-OAR-2021-0663-0083)
Commenter: West Virginia Department of Environmental
Protection
Commenter ID: 49
Docket ID: EPA-R03-OAR-2021-0873
Comment:
In the WV 2015 Ozone Good Neighbor SIP, DAQ applied
independent modeling performed by Alpine Geophysics
utilizing 2023 projected emissions. Alpine modeled at a
finer 4-km grid within the maintenance and nonattainment
receptor areas rather than the 12-km grid utilized by
EPA. Also, at this time, the Lake Michigan Air Directors
Consortium (“LADCO”) regional planning organization
(“RPO”) performed similar modeling. All three of these
efforts modeled remarkably comparable impacts at the
downwind monitor locations. As such, DAQ is further
puzzled by EPA’s abandonment of its own modeling results
by this proposed disapproval action.
Response
See Section V.A.4. of the preamble for our general
response to comments on the use of updated modeling to
support the EPA’s action. The EPA notes that the EPA
is not disapproving any SIP submission for its choice of
modeling. The EPA’s evaluations of each SIP submission
107a
Appendix E
were explained at proposal. See, e.g., 87 FR 9867-9869
(February 22, 2022) (Minnesota); 87 FR 9818-9824
(February 22, 2022) (Oklahoma); 87 FR 31492-31493
(May 24, 2022) (Nevada); and 87 FR 31477-31483 (May
24, 2022) (Utah). We respond to several additional specific
comments here.
One commenter claimed, “By delaying its decision on
Maryland’s submittal for nearly 2.5 years, the EPA
moved the goal post for Maryland—an act the DC Circuit
admonished in New York v. EPA, 964 F.3d 1214, 1223 (D.C.
Cir. 2020).” First, as explained in the preamble, the timing
of the EPA’s action is not moving the goal posts, nor does
availing ourselves of the most recent 2015 ozone transport
modeling and monitoring information do so. Second, New
York is inapposite. The court there found fault with the
EPA’s denial of a CAA section 126(b) petition from New
York, which had identified many upwind-state sources
with relatively large NOX emissions that the state alleged
significantly contributed in violation of the good neighbor
provision. The court found the EPA’s explanation for why
the state had not made out at least a facially plausible
showing of significant contribution to be arbitrary and
capricious. The court noted that downwind petitioning
states may lack the ability to conduct the kinds of analysis
the Agency’s denial suggested may be required and also
found internal inconsistencies in the Agency’s position
during litigation. None of that is relevant here. First,
this holding was not about air quality determinations,
but rather Step 3 analysis of source emissions reduction
potential. Second, upwind states are charged by the Act
with evaluating, defining, and prohibiting their sources’
significant contribution. Unlike a downwind jurisdiction,
108a
Appendix E
they possess all requisite authority to undertake an
analysis of emissions and emissions reduction potential
within their borders. See generally CAA section 110(a)(2). Nor
is the Agency obligated to define “significant contribution”
for upwind states before acting on these SIP submissions.
See EPA v. EME Homer City, 572 U.S. 489, 508-09 (2014).
APC and PacifiCorp both cite Texas v. EPA, 829 F.3d
405 (5th Cir. 2016) to argue that “EPA’s approval or
disapproval of a SIP should adhere to the guidance, data,
and evidence available and on the record at the time of
EPA’s timely review of the SIP.” In Texas, the 5th Circuit
granted a preliminary stay of the EPA’s disapproval of
Oklahoma’s and Texas’ regional haze SIP submissions
and promulgation of FIPs and did not reach the merits
of either the EPA’s assessment of the SIP submissions’
compliance with the requirements of the CAA or the
FIPs. 2 Although the court noted that the EPA proposed
amendments to the regional haze rule subsequent to Texas
and Oklahoma submitting regional haze SIP submissions,
that proposal was not relevant to the submissions before
the court. 3 Moreover, the EPA has not promulgated any
regulations to implement CAA section 110(a)(2)(D)(i)(I).
2. Texas v. EPA, 829 F.3d 405 (5th. Cir. 2016)
3. See, e.g., P rot ect ion of Visibi l ity: A mendment s t o
Requirements for State Plans; Proposed Rule, 81 Fed. Reg. 26941,
26944 (May 4, 2016) (explaining that the proposed “changes would
apply to periodic comprehensive state implementation plans
developed for the second and subsequent implementation periods
and for progress reports submitted subsequent to those plans.” And
that EPA “[did] not intend for the proposed changes to affect the
development of state plans for the first implementation period or the
first progress reports due under the existing Regional Haze Rule.”)
109a
Appendix E
Rather, EPA is applying its longstanding framework
for implementing CAA section 110(a)(2)(D)(i)(I) while
recognizing and considering any alternative approaches
states presented. EPA further notes that to the extent
APC objects to EPA’s consideration of 2016v2 modeling
or the updated 2016v3 modeling (adjusted in response to
public comment on this action), Alabama’s June 21, 2022,
SIP submission was submitted after the EPA made the
2016v2 modeling available and included arguments with
respect to that modeling, which the EPA has evaluated
in this final action.
APC, The Luminant Companies, and PacifiCorp quote
Sierra Club v. EPA, 356 F.3d 296, 308 (D.C. Cir. 2004):
“To require states to revise completed plans every time a
new model is announced would lead to significant costs and
potentially endless delays in the approval process.” In that
case, Sierra Club challenged EPA’s conditional approval
of Maryland, Virginia, and Washington, D.C.’s attainment
plans to address the Washington, D.C. Metropolitan
Area’s “Severe” classification for several reasons. 356
F.3d at 300. One reason was that the rate-of-progress
plans relied on an older emissions model (MOBILE5
as opposed to the more recent MOBILE6). Id. EPA
regulation specifically required states to use the latest
emission model available during the development their
rate-of-progress plans for the purposes of meeting Severe
requirements, CAA section 172(c)(3); 40 CFR 51.112(a)(1),
but because MOBILE6 became available one month before
these SIP submissions were submitted, the EPA accepted
the rateof-progress plan based on MOBILE5. 356 F.3d
at 308. The court agreed it was reasonable for EPA to
110a
Appendix E
not require Maryland, Virginia, and Washington, D.C.
to revise their rate-of-progress plans using MOBILE6.
Id. The EPA notes the timing consideration quoted by
commenters related to attainment planning in a Serious
nonattainment area. Here, however, the EPA has no
regulations that require any state to use any particular
type of model to address statutory requirements under
CAA section 110(a)(2)(D)(i)(I), nor is the EPA disapproving
any SIP submission on the basis of its choice of modeling
(as compared to EPA’s evaluation of the results of the
modeling). Further, the Sierra Club case does not stand
for the proposition that EPA is prevented from considering
the most up-to-date data in assessing whether upwind
states may be potentially significantly contributing to
downwind nonattainment or maintenance.
APC and The Luminant Companies cite Wisconsin v.
EPA, 938 F.3d 303, 336 (D.C. Cir. 2019) for the premise
that the EPA’s disapproval of a SIP submission on the
basis of “reliance on data compiled after the SIP action
deadline” may be challenged. The EPA acknowledges that
Wisconsin noted such was the States’ argument, but the
D.C. Circuit did not opine on the validity of the assertion
since it was not relevant to the court’s evaluation of the
CSPAR Update FIP.
A comment specifically pointed to the EPA’s proposed error
correction of its approval of Delaware’s SIP submission
(which is a component of the proposed FIP rulemaking
published April 6, 2022) to suggest the EPA had created
an unworkable standard for states. The commenter went
on to argue that the EPA must approve Tennessee’s
111a
Appendix E
SIP submission based on the information available at
the time Tennessee submitted it to the EPA. However,
this argument is illogical. If the EPA were to do that, it
would be treating Delaware and Tennessee dissimilarly.
In fact, the proposed error correction for Delaware only
illustrates the futility of commenters’ arguments for using
outdated information to approve their SIP submissions.
Had the EPA done that, then just as it proposed for
Delaware, the Agency would likely have simply conducted
error corrections of those approvals in light of the updated
projections of air quality and contributions in 2023 that
are now available.
Finally, it bears observance that if the EPA’s evaluation
of information regarding 2023 projections was arrested at
the time of some deadline in the past or with the issuance
of some older set of modeling results, then the purpose of
notice and comment rulemaking would itself be frustrated,
because no matter what arguments commenters could
make about more recent or current real-world conditions
or updated projections regarding 2023, the Agency would
be forced to ignore them. As an example, the EPA would
be obligated to ignore many of the comments on these
proposals providing updates to the EPA’s emissions
inventories, which we have considered in developing the
2016v3 modeling of 2023.
In response to Louisiana Chemical Association, the EPA
clarifies that the Agency found Louisiana’s SIP submission
complete on November 15, 2019. In response to Tennessee
Department of Environment and Conservation, the
EPA notes that the Agency is deferring final action on
112a
Appendix E
Tennessee’s good neighbor SIP submission at this time. In
response to Midwest Ozone Group, the EPA notes that the
Agency met with Multi-Jurisdictional Organizations such
as Central States Air Resource Agencies and others in
Summer 2021 to discuss the concerns outlined in the July
2021 letter cited in the comment.4 The EPA subsequently
made emissions data available on September 20, 2021, as
discussed in more detail in the preamble in Sections II.C
and III.A.1.
Other issues raised by these comments are addressed
in the preamble in Sections II.C, II.D, III.A.1., V.A.,
and V.B.2, and V.A.6, as well as in Section 1.2 (Guidance
for SIP Submissions), Section 5 (Updates to Modeling
and Changes in Linkages), 6.1.2 (Step 1 Receptors
Linked to Texas), 7.4 (August 2018 Memorandum), 8.1
(Determination of Significant Contribution), 10.2 (SIP
Call), and 10.3 (Cooperative Federalism and the EPA’s
Authority).
***
Commenter: Utah Division of Air Quality
Commenter ID: 47
Docket ID: EPA-R08-OAR-2022-0315
Comment:
The benefit of cooperative federalism is having the
autonomy to do what’s best for the state, but do so in
113a
Appendix E
partnership with EPA to ensure that the CAA intent and
requirements are met.
In this same spirit, UDAQ engaged early and often with
our counterparts at Region 8 in the development of our
interstate transport SIP. Through this collaboration and
EPA’s guidance, Utah selected the alternative threshold of
1 ppb. [...] Thus, UDAQ was surprised when EPA proposed
to include Utah in the proposed FIP, and subsequently
disapproved the state’s SIP based in large part on the
selection of the 1 ppb over the 1% of the NAAQS threshold.
If the 1 ppb threshold was in fact inappropriate for the
development of this SIP, EPA should have communicated
that view to UDAQ during the early engagement and
development process or during the state’s public comment
period. Additionally, EPA released no new guidance
directing states to use a 1% threshold either prior to or
after SIP submittal deadlines.
Response
Some commenters assert that the EPA did not provide
sufficient input to states during the development of the SIP
submissions, while others allege that the EPA led the states
astray or implied to states that the SIP submissions were
approvable. The EPA is required under CAA section 110
to review a SIP submission revision that has been formally
submitted; based on the EPA’s determination of whether
that submission meets applicable CAA requirements, the
EPA must then approve or disapprove the SIP submission.
There is no CAA requirement that the EPA must review,
evaluate, and comment on a state’s draft SIP submission
114a
Appendix E
revision during the state rulemaking process, and no legal
basis for states to assume that the EPA’s silence during
a state public comment period constitutes the Agency’s
endorsement of such SIP submission revision. Where
the EPA did communicate views to these states on draft
SIP submission revisions, the EPA disagrees that such
preliminary feedback should now bind the Agency, and
the EPA disagrees that we could in any way lawfully
provide “implied consent” to states regarding their draft
SIP submissions before they have completed the required
rulemaking processes at both the state and federal level.
After all, EPA cannot assure any state in advance of the
EPA’s public notice and comment process what the EPA’s
final action on a SIP submission will be. Catawba County
v. EPA, 571 F.3d 20, 34 (D.C. Cir. 2009) (“[a]n agency
pronouncement is not deemed a binding regulation merely
because it may have some substantive impact, as long as
it leave[s] the administrator free to exercise his informed
discretion.”) citing Panhandle Producers & Royalty
Owners Ass’n v. Econ. Regulatory Admin., 822 F.2d 1105,
1110 (D.C. Cir. 1987) (quoting Brock v. Cathedral Bluffs
Shale Oil Co., 796 F.2d 533, 537 (D.C. Cir. 1986) (internal
quotation marks omitted))).
The EPA encourages state air agencies to engage as early
as possible with the Agency on the development of any SIP
submission revisions in an effort to address all technical
and policy approvability issues prior to submitting a
final SIP submission package and appreciates states’
willingness to involve regional offices at the initial SIP
submission development stage. Further, the EPA makes
its best efforts to work closely with states, but EPA
115a
Appendix E
cannot be expected to provide states definitive guidance
on what will ultimately be approvable. Nonetheless, the
suggestions we made to states on their SIP submissions
in this instance are not inconsistent with the final action
we are now taking.
Other issues raised by these comments are addressed
in Section V.A.3., V.A.6., and V.B.7. of the preamble
and the following sections: 1.1 (Timing of SIP Actions),
1.2 (Guidance for SIP Submissions), 7.4 (August 2018
Memorandum), 10.3 (Cooperative Federalism and the
EPA’s Authority), 11.6 (Economic Impacts), and 11.12
(Consent Decrees).
116a
Appendix E
Commenter: Pacif iCor p (Attachment – Ramboll
Evaluation)
Commenter ID: 38
Docket ID: EPA-R08-OAR-2022-0315
Comment:
4.5.1 Effects of Higher Resolution 4-km Grid in DM/NFR
SIP Modeling
[...] In order to properly simulate ozone formation in the
DM/NFR NAA, a high resolution grid cell size needs to be
used. All of the Denver ozone SIPs in the past have used a
4-km grid resolution to simulate the correct meteorology
and chemistry and resolve the urban plumes so that the
model has a chance to reproduce the highest observed
ozone concentrations. Use of a coarse 12-km grid will
instantaneously disperse emissions across a grid cell
volume that is almost an order of magnitude larger than
when a 4- km grid size is used making it difficult for the
model to reproduce the high observed ozone peaks due to
overdiluting the ozone concentrations and its precursors.
Note that use of a coarse 12-km grid resolution will also
reduce ozone peaks due to local sources in the Upwind
State due to failure to resolve urban and other highly
concentrated ozone precursor emission sources (e.g.,
industrial facilities, O&G, etc.) and their resultant ozone
plumes. However, by the time the ozone and precursor
concentrations from the Upwind State travel 100s of miles
117a
Appendix E
to the receptor in the downwind state the “plumes” will
be many 12-km grid cells across so that the effects of the
coarse resolution on underestimating ozone concentrations
at the receptor in the downwind state due to emissions in
the Upwind State is less important.
[...]
4.5.2 Effects of Higher Resolved Meteorological Inputs
on Ozone Concentrations in the DM/NFR Ozone SIP
Modeling
Obtaining the correct depiction of meteorology is critically
important for simulating ozone formation in the complex
terrain conditions of the DM/NFR NAA. [...]
4.5.2.1 Conceptual Model of Ozone Formation in the DM/
NFR NAA
The DM/NFR 2020 Serious ozone SIP for the 2008
ozone NAAQS (RAQC and CDPHE, 2020) included a
report “Conceptual Model of High Ozone for the Denver
Metro/North Front Range” (Ramboll, 2020). The highest
ozone concentrations in the DM/NFR NAA are due to a
combination of ozone transport and locally generated ozone
under specific meteorological regimes that favor ozone
photochemistry and limited dispersion. Reddy and Pfister
(2016) explored the relationships between meteorology and
ozone in the Rocky Mountain states and concluded that
increases in upper-level high pressure strength “lead to
high July ozone in much of the western U.S., particularly
in areas of elevated terrain near urban sources with high
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Appendix E
emissions of NO2 and other ozone precursors.” In addition
to bringing warmer temperatures, upper-level ridges in
this region reduce westerly winds at the surface and aloft
to allow cyclic terrain-driven circulations that reduces
transport away from sources. This includes the formation
of thermally driven upslope flows along the Front Range
in the Denver NAA where ozone and ozone precursors are
transported up the slopes during the day and can return
at night to lower elevations in large scale basin drainage
(downslope) flows. Upper-level ridges can also increase
background ozone concentrations within the ridge. Ozone
and NOX concentrations build locally, and deeper vertical
mixing in this region provides a potential mechanism for
recapture of ozone in layers aloft (e.g., from transport or
remnants of the previous days ozone) that are mixed down
to the surface.
The three key elements of a conceptual model for highconcentration ozone episodes along Colorado’s Front
Range are:
1. The presence of an upper-level high pressure
system or ridge.
2. Reduced westerly winds, especially during
the day.
3. Thermally-driven upslope f low towards
the Continental Divide during the day and
downslope drainage f lows into the Platte
Valley at night. This diurnal cycle of winds
enhances the potential for the accumulation of
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Appendix E
ozone precursors and ozone within the region,
especially when this cyclic pattern recurs over
a period of several days.
4.5.2.2 Requirements for WRF Meteorological Model to
Reproduce DM/NFR NAA Ozone Conceptual Model
In order for the Weather Research and Forecasting (WRF)
meteorological model to reproduce the meteorological
conditions that lead to the highest ozone concentrations in
the Denver NAA it needs to be able to simulate the high
pressure system/ridge and the thermally driven slope
flows. Getting the high pressure system or ridge correctly
requires using analysis fields as inputs into WRF that
reflects their presence that are used in the WRF initial
and boundary conditions (IC/BC) and four-dimensional
data assimilation (FDDA) inputs. Such analysis fields that
contain the presence of the high pressure/ridges include
the North American Mesoscale Forecast System (NAM29)
analysis fields that were used in the WRF simulations to
develop the CAMx 2016 meteorological inputs for both the
DM/NFR 2023 Severe/Moderate ozone SIP and Proposed
Transport Rule CAMx 2016 modeling platforms.
For WRF to obtain an accurate depiction of the thermally
driven slope flows requires the terrain inputs for the
model to be representative of actual terrain. Use of a
12-km grid resolution smooths the terrain and greatly
reduces the terrain heights and the elevation differences
of the “slopes” of the terrain along the Front Range. The
slope between western Denver County to the continental
divide spans approximately 7,800 feet in elevation using
120a
Appendix E
a 4-km grid resolution but only approximately 4,500
feet in elevation change using the 12-km grid resolution.
Thus, WRF’s ability to reproduce the thermally driven
daytime upslope and nighttime downslope flows will be
severely compromised using a 12-km grid resolution
and simulated much more accurately using a 4-km grid
resolution because a 12-km grid resolution fails to resolve
the terrain in the region.
The higher resolution complex terrain in the 4-km data,
and in reality, will also affect transport of ozone and
precursors from Wyoming to the Denver NAA differently
than if a 12-km grid resolution is used. The higher variable
wind fields from more highly resolved terrain features
will disperse ozone and precursors from Wyoming as they
are transported to the Denver NAA than if a 12-km grid
resolution is used that smooths the actual terrain features.
[...]
4.5.3 Comparison of CAMx Ozone Model Performance
and Its Implications
[Ramboll] conducted an ozone model performance of the
CAMx 2016 base case simulation used in the Proposed
Transport Rule and compared it to the ozone performance
of the DM/NFR 2023 Severe/Moderate ozone SIP CAMx
S17 2016 base case simulation. At this time, only limited
publicly available information is available on ozone model
performance for the DM/NFR ozone SIP CAMx S17 2016
base case from presentations given at the May 18, 2022
RAQC Ozone Modeling Forum.
121a
Appendix E
Ozone model performance goals and criteria have been
established by Emery and co-workers (2016) for the
Normalized Mean Bias (NMB) and Normalized Mean
Error (NME) model performance metrics. The NMB
ozone model performance goal is ≤±5% and the NMB
ozone performance criterion is ≤±15%. The NME ozone
model performance goal and criterion are ≤15% and
≤25%, respectively.
[...]
The DM/NFR ozone SIP CAMx 2016 base case ozone
performance is clearly performing better than the EPA
Proposed Transport Rule CAMx 2016 base case at all four
sites in the DM/NFR NAA. The EPA CAMx 2016 base
case exhibits an ozone underestimation bias, which was
expected given the coarse 12-km grid resolution used. At
CHAT, the Proposed Transport Rule CAMx 2016 base
case has an NMB underestimation of -7.6% while the DM/
NFR 2023 Severe/Moderate ozone SIP has essentially
zero bias (0.1%). The underestimation bias in the Proposed
Transport Rule CAMx 2016 base case is even greater at
the RFNO (-8.1%), NREL (-8.4%) and FTCW (-12.5%)
sites while the DM/NFR ozone SIP CAMx 2016 base case
bias achieves the bias performance goal by a wide margin.
[...]
Ozone attainment/nonattainment is determined by
the ozone design value (DV) that is defined as the
three-year average of the fourth highest maximum
daily average 8-hour (MDA8) ozone concentrations.
122a
Appendix E
Thus, how well the model simulates the four highest
observed MDA8 ozone concentrations is an important
model performance attribute. The highest observed
MDA8 ozone concentration at Chatfield during 2016
was 86.6 ppb that was underestimated by the Proposed
Transport Rule CAMx 2016 base case (74.9 ppb) by 11.7
ppb (-13.5%). Whereas, the DM/NFR ozone SIP CAMx
2016 base case highest estimated ozone concentration at
Chatfield (86.4) matched the observed value (86.6 ppb)
almost exactly (within 0.2 ppb or 0.0% difference). The
fourth highest observed MDA8 ozone concentration at
Chatfield (78.0 ppb) is underestimated by the Proposed
Transport Rule CAMx 2016 base case (71.9 ppb) by 6.1
ppb (-7.8%), while the DM/NFR ozone SIP CAMx base
case fourth highest ozone at Chatfield (78.1 ppb) matches
the observed fourth highest ozone very well (0.1 ppb and
0.0% difference).[...] The ozone under-prediction bias of
the Proposed Transport Rule CAMx 2016 base case at
RFNO is even greater than at CHAT with the four highest
observed ozone concentrations underestimated by -11%
to -19%. The DM/NFR ozone SIP CAMx 2016 base case
also underestimates the four highest observed MDA8
ozone concentrations at RFNO but the underestimation
bias (-4% to -10%) is approximately half of the Proposed
Transport Rule underestimation bias. For example, the
observed fourth highest MDA8 ozone at RFNO (79.5%) is
underestimated by the Proposed Transport Rule by -11%
(70.9 ppb) but is only underestimated by the DM/NFR
ozone SIP CAMx 2016 base case by -4% (76.3 ppb), which
achieves the ≤±5% ozone performance goal.
[...]
123a
Appendix E
4.6 Conclusions On Future Year Projected Ozone Design
Values at DM / NFR Nonattainment / Maintenance
Receptors
Based on scientific technical arguments, the coarse 12km grid resolution used in the Proposed Transport Rule
CAMx modeling will likely overstate future year design
value projections. This was confirmed by the DM/NFR
2023 Severe/Moderate ozone SIP CAMx 4-km grid
resolution modeling that produced lower future year
projected design values resulting in Chatfield and Rocky
Flats North no longer being nonattainment/maintenance
receptors in 2026.
[...]
Utah was linked to three receptors in the DM/NFR
NAA (CHAT, RFNO and NREL). Two of these receptors
(CHAT and RFNO) become attainment receptors based
on the refined DM/NFR Severe/Moderate ozone SIP
CAMx modeling, although NREL receptor remained
a nonattainment receptor in the DM/NFR ozone SIP
CAMx modeling (see Table 4-5 [available in full comment]).
However, Utah has a 0.90 ppb ozone contribution to the
NREL receptor in 2026 and, as discussed in Chapter 7, this
contribution is not a statistically significant contribution to
an ozone design value. This argues that Utah should also
not be subject to the 2026 EGU and non-EGU controls in
the Proposed Transport Rule.
5.2 Coarse Grid Resolution Will Understate O
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