[Federal Register Volume 86, Number 202 (Friday, October 22, 2021)]
[Proposed Rules]
[Pages 58630-58635]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-22662]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2021-0638; FRL-9101-01-R9]


Clean Air Plans; Base Year Emissions Inventories for the 2015 
Ozone Standards; Arizona; Phoenix-Mesa and Yuma Nonattainment Areas

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve, under the Clean Air Act (CAA), revisions to the Arizona State 
Implementation Plan (SIP) concerning the base year emissions inventory 
requirements for the Phoenix-Mesa ozone nonattainment area (``Phoenix-
Mesa'') and Yuma ozone nonattainment area (``Yuma'') for the 2015 ozone 
national ambient air quality standards (NAAQS or ``standard'').

DATES: Any comments must arrive by November 22, 2021.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2021-0638 at https://www.regulations.gov. For comments submitted at 
Regulations.gov, follow the online instructions for submitting 
comments. Once submitted, comments cannot be edited or removed from 
Regulations.gov. The EPA may publish any comment received to its public 
docket. Do not submit electronically any information you consider to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Multimedia submissions (audio, 
video, etc.) must be accompanied by a written comment. The written 
comment is considered the official comment and should include 
discussion of all points you wish to make. The EPA will generally not 
consider comments or comment contents located outside of the primary 
submission (i.e., on the web, cloud, or other file sharing system). For 
additional submission methods, please contact the person identified in 
the FOR FURTHER INFORMATION CONTACT section.

[[Page 58631]]

For the full EPA public comment policy, information about CBI or 
multimedia submissions, and general guidance on making effective 
comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. If you need assistance in a language other than English or if 
you are a person with disabilities who needs a reasonable accommodation 
at no cost to you, please contact the person identified in the FOR 
FURTHER INFORMATION CONTACT section.

FOR FURTHER INFORMATION CONTACT: Ben Leers, Air Planning Office (AIR-
2), EPA Region IX, (415) 947-4279, [email protected].

SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,'' 
and ``our'' refer to the EPA.

Table of Contents

I. Background
    A. Emissions Inventories
    B. State Submittals
    C. Public Notice and Hearing Requirements
II. Arizona's Emissions Inventories
    A. Baseline Emissions Inventory for the Phoenix-Mesa 
Nonattainment Area
    B. Baseline Emissions Inventory for the Yuma Nonattainment Area
III. EPA's Evaluation
IV. Proposed Action and Request for Public Comment
V. Statutory and Executive Order Reviews

I. Background

    On October 26, 2015, the EPA promulgated a revised 8-hour ozone 
NAAQS of 0.070 parts per million (ppm).\1\ In accordance with section 
107(d) of the CAA, the EPA must designate an area ``nonattainment'' if 
it is violating the NAAQS or if it is contributing to a violation of 
the NAAQS in a nearby area.
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    \1\ 80 FR 65292 (October 26, 2015).
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    The EPA designated two areas in Arizona as nonattainment for the 
2015 ozone NAAQS on June 4, 2018, effective August 3, 2018.\2\ The 
Phoenix-Mesa nonattainment area (including Gila, Maricopa, and Pinal 
counties) and Yuma nonattainment area (including Yuma County) were 
classified as ``Marginal'' ozone nonattainment.
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    \2\ 83 FR 25776.
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A. Emissions Inventories

    Sections 172(c)(3) and 182(a)(1) of the CAA require states to 
develop and submit, as a SIP revision, ``base year'' emissions 
inventories for all areas designated as nonattainment for an ozone 
NAAQS. The EPA finalized the 2015 ozone NAAQS SIP Requirements Rule 
(SRR) on December 6, 2018. The SRR established implementation 
requirements for the 2015 ozone NAAQS, including requirements for base 
year emissions inventories under CAA section 182(a)(1).\3\ The SRR for 
the 2015 ozone NAAQS is codified at 40 CFR part 51, subpart CC, and the 
emissions inventory requirements are codified at 40 CFR 51.1315.
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    \3\ 83 FR 62998.
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    An emissions inventory for ozone is an estimation of actual 
emissions of air pollutants that contribute to the formation of ozone 
in an area. Ozone is a gas that is formed by the reaction of volatile 
organic compounds (VOC) and oxides of nitrogen (NOX), 
referred to as ozone precursors, in the atmosphere in the presence of 
sunlight. Therefore, an emissions inventory for ozone focuses on the 
emissions of VOC and NOX. VOC is emitted by many types of 
sources, including power plants, industrial sources, on-road and off-
road mobile sources, smaller stationary sources collectively referred 
to as area sources, and biogenic sources. NOX is primarily 
emitted by combustion sources, both stationary and mobile.
    Emissions inventories provide emissions data that inform a variety 
of air quality planning tasks, including establishing baseline 
emissions levels, calculating emissions reduction targets needed to 
attain the NAAQS and to achieve reasonable further progress (RFP) 
toward attainment of the ozone standard,\4\ determining emissions 
inputs for ozone air quality modeling analyses, and tracking emissions 
over time to determine progress toward achieving air quality and 
emissions reduction goals.
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    \4\ The RFP requirements specified in CAA section 182(b)(1) 
apply to all areas classified as ``Moderate'' or higher ozone 
nonattainment. At the time of submittal of the Phoenix-Mesa and Yuma 
base year emissions inventory SIPs for the 2015 ozone NAAQS, the 
Phoenix-Mesa and Yuma areas were designated Marginal nonattainment 
for the 2015 ozone NAAQS and were therefore not required to 
demonstrate RFP toward attainment of the 2015 ozone NAAQS.
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    For the 2015 ozone NAAQS, states are required to submit ozone 
season day emissions estimates for an inventory calendar year to be 
consistent with the baseline year for RFP plans as required by 40 CFR 
51.1310(b).\5\ Under 40 CFR 51.1310(b), for the 2015 ozone NAAQS, the 
RFP baseline year is the most recent calendar year for which a complete 
triennial inventory is required to be submitted to the EPA under 40 CFR 
51 subpart A.\6\ States may use an alternative baseline emissions 
inventory provided that the year selected corresponds with the year of 
the effective date of designation as nonattainment for that NAAQS. 
Ozone season day emissions are defined in 40 CFR 51.1300(q) as the 
average day's emissions for a typical ozone season work weekday. Under 
the definition in 40 CFR 51.1300(q), states are required to select the 
months in the ozone season and the days in the work week to be 
represented. Per EPA's 2017 guidance on emissions inventory 
development, the selected ozone season should be representative of the 
conditions leading to nonattainment.\7\
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    \5\ 40 CFR 51.1315(a).
    \6\ 83 FR 62998, 63034.
    \7\ EPA, ``Emissions Inventory Guidance for Implementation of 
Ozone and Particulate Matter National Ambient Air Quality Standards 
(NAAQS) and Regional Haze Regulations'' (May 2017), 75.
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B. State Submittals

    On July 8, 2020, the Arizona Department of Environmental Quality 
(ADEQ) submitted a revision to the Arizona SIP titled ``Maricopa 
Association of Governments (MAG) 2020 Eight-Hour Ozone Plan'' (``2020 
Phoenix-Mesa SIP Submittal''). The 2020 Phoenix-Mesa SIP Submittal 
includes a 2017 baseline emissions inventory for Phoenix-Mesa developed 
by the Maricopa Association of Governments (MAG) and supporting 
documentation regarding the development of the baseline emissions 
inventory.
    On July 29, 2020, ADEQ submitted a revision to the Arizona SIP 
titled ``Marginal Ozone Plan for the Yuma Nonattainment Area,'' 
including a 2017 baseline emissions inventory for Yuma and supporting 
documentation regarding the development of the emissions inventory. The 
July 29, 2020 submittal did not include final amendments to the 
emissions statement rule in Arizona Administrative Code R18-2-327 and 
did not adequately satisfy the public notice requirements under 40 CFR 
51.102. On December 22, 2020, ADEQ withdrew the July 29, 2020 submittal 
and submitted as a revision to the Arizona SIP another plan, also 
titled ``Marginal Ozone Plan for the Yuma Nonattainment Area.'' On July 
1, 2021, Arizona provided a technical supplement to the Marginal Ozone 
Plan for the Yuma Nonattainment Area addressing comments and questions 
raised by the EPA following receipt of ADEQ's prior submittals.\8\ 
Arizona's December 22, 2020 submittal and the July 1, 2021 supplement 
are collectively referred to herein as the ``2020 Yuma SIP Submittal.'' 
Where specifically

[[Page 58632]]

referring to information provided in Arizona's supplement to the 2020 
Yuma SIP Submittal, we refer to the July 1, 2021 supplement as the 
``2021 Yuma SIP Supplement.''
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    \8\ Letter dated June 30, 2021, from Joseph Martini, Manager, 
Air Quality Improvement Planning Section, Air Quality Division, 
Arizona Department of Environmental Quality, to Ben Leers, Air 
Planning Office, Air Division, EPA Region IX. Transmitted via email 
dated July 1, 2021, from Farah Esmaeili, Environmental Senior 
Engineer, Technical Analysis Unit, Air Quality Division, Arizona 
Department of Environmental Quality to Ben Leers.
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    In this action, we are evaluating and proposing action on the 2020 
Phoenix-Mesa SIP Submittal and the 2020 Yuma SIP Submittal.

C. Public Notice and Hearing Requirements

    CAA sections 110(a)(1) and 110(l) and 40 CFR 51.102 require states 
to provide reasonable notice and an opportunity for a public hearing 
prior to adoption of SIP revisions. Section 110(k)(1)(B) requires the 
EPA to determine whether a SIP submittal is complete within 60 days of 
receipt. Any plan that the EPA does not affirmatively determine to be 
complete or incomplete will become complete six months after the day of 
submittal by operation of law. A finding of completeness does not 
approve the submittal as part of the SIP, nor does it indicate that the 
submittal is approvable. It does start a 12-month clock for the EPA to 
act on the SIP submittal (see CAA section 110(k)(2)).
    The 2020 Phoenix-Mesa SIP Submittal and 2020 Yuma SIP Submittal 
each document the public review process followed prior to their 
submittal to the EPA as revisions to the SIP.
    Appendix B of the 2020 Phoenix-Mesa SIP Submittal includes 
documentation of notices of opportunity for public hearing and comment 
on the SIP submittal. The notices for opportunity for public hearing 
and comment on the SIP submittal were posted in The Arizona Republic, 
sent by email to interested parties, and posted on MAG's website. Also 
included in Appendix B of the 2020 Phoenix-Mesa SIP Submittal is a 
responsiveness summary indicating that no comments or requests for 
public hearing were received during the 30-day public review period.
    Appendix B of the 2020 Yuma SIP Submittal includes documentation of 
a notice of public comment period and hearing on the SIP submittal 
posted in The Arizona Republic on October 9, 2020, and October 10, 
2020. Appendix B of the 2020 Yuma SIP Submittal also contains 
documentation of the November 12, 2020 public hearing on the SIP 
submittal including a sign-in sheet, transcript, signed certification 
that the public hearing was held, and a compilation of comments 
received and ADEQ's responses to comments.

II. Arizona's Emissions Inventories

    The 2020 Phoenix-Mesa SIP Submittal and 2020 Yuma SIP Submittal 
each address the emissions inventory requirement in CAA section 
182(a)(1). Each submittal provides documentation of a 2017 base year 
inventory of emissions of NOX and VOC. The 2017 base year 
emissions inventory was the most recent triennial emissions inventory 
in the National Emissions Inventory (NEI) at the time the emissions 
inventories were prepared for the Phoenix-Mesa and Yuma areas.
    Each emissions inventory submittal includes emissions estimates for 
the following source categories: Point sources, nonpoint sources, 
nonroad mobile sources, onroad mobile sources, and biogenic sources. 
Point sources are generally large, stationary (i.e., non-mobile) 
sources of air pollutants. MAG's and ADEQ's specific interpretations of 
the point source definition are described in sections II.A and II.B of 
this notice, respectively. Nonpoint sources, also referred to as 
``area'' sources, are the sources of air pollutants that are typically 
too small or too numerous to be categorized as point or mobile sources, 
such as residential combustion or consumer products. Nonroad mobile 
sources, also referred to as ``off-highway'' mobile sources, include 
nonroad engines and nonroad vehicles. Onroad mobile sources, also 
referred to as ``highway mobile sources,'' are motor vehicles traveling 
on local highways and roads. Biogenic sources emit pollutants produced 
by natural sources including vegetation and soils.
    ADEQ and MAG each used a combination of top-down estimation 
techniques (i.e., allocation of regional emissions estimates to a 
smaller, defined geographic area) and bottom-up estimation techniques 
(i.e., development of source or source category emissions estimates 
using emissions factors, models, etc.) to develop the emissions 
inventories in their respective SIP submittals. Specific estimation 
techniques for each source category are described in sections II.A and 
II.B of this notice.

A. Baseline Emissions Inventory for the Phoenix-Mesa Nonattainment Area

    The emissions inventory included in the 2020 Phoenix-Mesa SIP 
Submittal was developed by MAG. The Phoenix-Mesa area includes Maricopa 
County and portions of Gila and Pinal Counties.\9\ MAG selected the 
months of June through August to estimate ozone season day emissions of 
NOX and VOC from sources in the Phoenix-Mesa area.\10\
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    \9\ See 83 FR 25776, 25784-25785, for a detailed description of 
the boundaries of the Phoenix-Mesa nonattainment area for the 2015 
ozone NAAQS.
    \10\ A detailed justification for MAG's selection of months in 
the ozone season is provided in Appendix F of the 2020 Phoenix-Mesa 
SIP Submittal.
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    In the 2020 Phoenix-Mesa SIP Submittal, MAG defines point sources 
consistent with the point source definition put forth in EPA's air 
emissions reporting requirements (AERR).\11\ MAG identified 19 
stationary sources meeting the point source definition in the Phoenix-
Mesa area. As noted in the 2020 Phoenix-Mesa SIP Submittal, while some 
stationary sources in Maricopa County are permitted by ADEQ, no ADEQ-
permitted facilities meet the point source definition, and such sources 
are instead categorized as area sources. All point sources in the 
Phoenix-Mesa area are located in Maricopa County and are permitted by 
the Maricopa County Air Quality District (MCAQD). MAG identified point 
sources in the Phoenix-Mesa area via the MCAQD electronic permit system 
database. MAG calculated emissions from point sources using annual 
source emissions reports, MCAQD investigation reports, permit files and 
logs, or telephone contacts with sources. Point source emissions 
calculations in the Phoenix-Mesa area also considered ``rule 
effectiveness,'' a factor that may be applied to emissions inventory 
estimates to account for regulatory programs which may be less than 100 
percent effective.
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    \11\ Under the AERR, a point source is a facility that is a 
major source under 40 CFR part 70 for one or more of the pollutants 
for which reporting is required by CAA section 51.15(a)(1), but not 
with regard to emissions of hazardous air pollutants. 80 FR 8787 
(February 19, 2015). For major source emissions thresholds by 
pollutant, see 40 CFR 51.30.
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    In the point source category, MAG also accounted for actual and 
potential voluntary emissions reductions at point sources in the 
Phoenix-Mesa area. Major new sources and major modifications in the 
Phoenix-Mesa area must offset the emissions of NOX and VOC 
generated by the new source or modification as a condition for approval 
of permit applications. These emissions offsets are generally obtained 
from existing sources located in the vicinity of the proposed source or 
modification in the form of emissions reduction credits (ERCs). The 
rules governing the generation and use of ERCs in the Phoenix-Mesa area 
area are outlined in MCAQD Rule 240. In the 2017 base year inventory, 
MAG included certified ERCs available in the Arizona Emissions Bank in 
the point source category totals. MAG also included potential (i.e., 
not yet certified) sources of ERCs for NOX and VOC in the

[[Page 58633]]

base year inventory in order to maintain the availability of these 
emissions in the periodic inventory, provided that sufficient 
documentation can be secured to confirm the emissions reductions in the 
future.
    MAG estimated county-level emissions from nonpoint sources using a 
variety of tools, techniques, and assumptions depending on each 
nonpoint source subcategory. MAG's nonpoint source emissions estimates 
were informed by EPA's 2017 nonpoint emissions methodology and operator 
instructions, source-submitted annual emissions reports, and scaling up 
via the use of per-employee emissions factors. For each nonpoint source 
subcategory, county-level emissions estimates were allocated to the 
Phoenix-Mesa area using one of five representative variables: 
Employment, population, land use, general aviation operations, and 
location data. Each nonpoint source emissions calculation and 
allocation method is described in detail in the 2020 Phoenix-Mesa SIP 
Submittal.
    Nonroad mobile source subcategories in the Phoenix-Mesa emissions 
inventory include agricultural equipment (e.g., tractors, combines, and 
balers), recreational equipment (e.g., all-terrain vehicles and off-
road motorcycles), aircraft, and locomotives, among others. For most 
nonroad mobile source subcategories, MAG estimated emissions using the 
latest available version of EPA's Motor Vehicle Emission Simulator 
(MOVES2014b). Inputs to MOVES2014b included default model input files, 
National Oceanic and Atmospheric Administration (NOAA) National Centers 
for Environmental Information (NCEI) local climatological data, 2017 
fuel specifications and vapor recovery program effectiveness from the 
Arizona Department of Agriculture Weights & Measures Services Division, 
and local data from a 2003 survey performed for ADEQ by ENVIRON. For 
aircraft and airport equipment, MAG estimated emissions using the 
Federal Aviation Administration (FAA) Aviation Environmental Design 
Tool version 2d (AEDT 2d). Inputs to AEDT 2d included local aircraft 
activity data from the FAA Operations Network, AirNav.com, and base 
personnel at Luke Air Force Base. Additionally, MAG utilized aircraft 
fleet mix profiles from the FAA Traffic Flow Management System Counts 
database, verification of AirNav.com data using the FAA 5010 Airport 
Master Records database, and general aviation airport survey data 
conducted by MAG in 2017. Emissions from locomotives were estimated 
using survey data from the three railroad companies operating in 
Maricopa County (i.e., Burlington Northern Santa Fe, Union Pacific, and 
Amtrak) and emissions factors published by ENVIRON and the EPA.
    Emissions from onroad mobile sources in the Phoenix-Mesa area were 
calculated using MOVES2014b. For onroad mobile sources, MOVES2014b 
requires local data inputs relating to vehicle inspection and 
maintenance programs, meteorological data, vehicle populations, source 
type age distributions, annual vehicle miles traveled, and alternative 
vehicle and fuel technologies, among others. MAG cited numerous sources 
and assumptions for local data inputs, including vehicle registration 
data from the Arizona Department of Transportation, meteorological data 
from the NOAA NCEI, and the MAG Transportation Modeling Group.
    Emissions from biogenic sources in the Phoenix-Mesa area were 
calculated using the Model of Emissions of Gases and Aerosols from 
Nature (MEGAN) version 2.1. MEGAN requires inputs of land cover and 
meteorological data. MAG utilized 1-kilometer eight-day average leaf 
area index from the National Aeronautics and Space Administration's 
Moderate Resolution Imaging Spectroradiometer satellite observations, 
plant functional type (PFT) data from the National Land Cover Dataset, 
and emission factors derived from PFT distributions. MAG processed 
meteorological data from the Weather Research and Forecasting model 
version 3.9 with the Meteorology-Chemistry Interface Processor (MCIP). 
The model outputs from MCIP were further processed using the MEGAN 
component program called MET2MGN for input to MEGAN.
    MAG employed quality assurance and quality control (QA/QC) measures 
throughout the development of the Phoenix-Mesa emissions inventory. 
Point source emissions reports undergo automated QA/QC upon submission 
to MCAQD's database as well as manual QA/QC performed by air quality 
planning staff. Area source emissions calculations are peer-reviewed by 
air quality planners to ensure calculations can be reproduced. Other 
QA/QC procedures performed by MAG include review of files by personnel 
not involved in the development of the inventory as well as comparison 
of the 2017 inventory to 2014 and 2011 inventories. MAG's QA/QC 
procedures are described in detail in the 2020 Phoenix-Mesa SIP 
submittal.
    Estimates of 2017 ozone season day emissions of NOX and 
VOC in the Phoenix-Mesa area are summarized in Table 1 below.

                                                        Table 1--2017 Ozone Season Day Emissions
                                                          Phoenix-Mesa Ozone Nonattainment Area
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                                                                                    Ozone season day emissions (pounds per day)
                        Pollutant                        -----------------------------------------------------------------------------------------------
                                                               Point         Nonpoint     Nonroad mobile   Onroad mobile     Biogenic       Area total
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NOX.....................................................          24,277          32,880         112,100         140,154           5,896         315,307
VOC.....................................................           8,625         209,885          63,661         112,746       1,283,539       1,678,457
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Source: 2020 Phoenix-Mesa SIP Submittal, Appendix A, 11.

B. Baseline Emissions Inventory for the Yuma Nonattainment Area

    The emissions inventory included in the 2020 Yuma SIP Submittal was 
developed by ADEQ. The Yuma area consists of approximately 52 square 
miles within Yuma County in and around the city of Yuma, Arizona.\12\ 
ADEQ selected the months of April through October to estimate ozone 
season day emissions of NOX and VOC from sources in the Yuma 
area.\13\
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    \12\ See 83 FR 25776, 25785 for a detailed description of the 
boundaries of the Yuma nonattainment area for the 2015 ozone NAAQS.
    \13\ ADEQ's selection of the months in the ozone season is 
consistent with documentation provided by ADEQ along with its 
initial nonattainment boundary recommendations for the 2015 ozone 
NAAQS. See the technical support document ``Phoenix-Mesa and Yuma 
Nonattainment Areas; Intended Area Designations for the 2015 Ozone 
National Ambient Air Quality Standards,'' included in the docket for 
EPA's initial designations for the 2015 ozone NAAQS under docket ID 
EPA-HQ-OAR-2017-0548.

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[[Page 58634]]

    ADEQ obtained emissions estimates for point sources in the Yuma 
area from the 2017 NEI and from source-submitted annual emissions 
inventory reports required for all sources holding a minor permit in 
Arizona. All point sources listed in the 2017 NEI and geographically 
located in the Yuma ozone nonattainment area were included in the point 
source category in the 2020 Yuma SIP Submittal. ADEQ also included 
minor point sources holding permits in the Yuma ozone nonattainment 
area in the point source category.
    Emissions from Yuma area nonpoint sources (also referred to as 
``area sources'' in the 2020 Yuma SIP Submittal) were estimated 
predominantly using data from the 2017 NEI. The 2017 NEI includes 
emissions estimates for numerous area source subcategories on the 
county level. For most nonpoint source subcategories, ADEQ allocated 
county-level emissions estimates from the 2017 NEI to the Yuma area 
based on population, industrial employment, land area, crop land area, 
or railroad length. Emissions calculation methods used for the 
remaining nonpoint source subcategories include per-person emissions 
factors included in 2017 NEI documentation, information from permits, 
and information from source-submitted annual reports.
    ADEQ estimated emissions from nonroad mobile sources in the Yuma 
area by allocating emissions from 2017 NEI data using representative 
factors including population, cropland area, and railroad length. 
Nonroad mobile source categories addressed in the 2020 Yuma SIP 
submittal include: Agricultural equipment; commercial equipment; 
construction and mining equipment; industrial equipment; lawn and 
garden equipment; logging equipment; recreational equipment; pleasure 
craft; and locomotives. Of the eight private and public airports 
identified by ADEQ in Yuma County, none are located within the Yuma 
ozone nonattainment area. Therefore, ADEQ assumed zero nonroad mobile 
source emissions from airports.
    Emissions from onroad mobile sources in the Yuma area were 
calculated using MOVES2014b. In the 2020 Yuma SIP Submittal, ADEQ 
listed MOVES2014b inputs for source type, road type, fuel type, and 
process type. ADEQ notes in the 2020 Yuma SIP Submittal that the Yuma 
area is located adjacent to a major trucking and travel corridor, and 
freight haulers and tractor trailers are primary producers of VOC and 
NOX emissions in the Yuma area.
    ADEQ estimated emissions from biogenic sources in the Yuma area 
using biogenic emissions data from the 2017 NEI. County-level biogenic 
emissions from the 2017 NEI were allocated to the Yuma area using the 
ratio of land area in the Yuma ozone nonattainment area to the land 
area within Yuma County. As described in the 2020 Yuma SIP Submittal, 
ozone season day biogenic emissions were estimated by summing the 
biogenic emissions in the Yuma area for each month in the ozone season 
(April through October) and dividing by the number of days in the ozone 
season (213 days).
    ADEQ engaged numerous QA/QC procedures in the development of the 
2020 Yuma SIP Submittal. ADEQ prepared an inventory preparation plan 
(IPP) and incorporated feedback from the EPA on the IPP to identify and 
follow suitable estimation methodologies. Procedures outlined in ADEQ's 
EPA-reviewed quality assurance project plan were followed to conduct 
QA/QC on emissions estimates submitted by sources.\14\ In general, ADEQ 
conducted peer and management review of the technical support document 
to the 2020 Yuma SIP Submittal and underlying calculations. A detailed 
description of ADEQ's QA/QC procedures is included in the 2020 Yuma SIP 
Submittal.
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    \14\ ADEQ's ``Annual Permitted Source Emissions Inventories 
Quality Assurance Project Plan'' (October 2020) is included in the 
docket for this rulemaking.
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    The 2021 Yuma SIP Supplement provides clarification on emissions 
inventory details including selection of ozone season months, handling 
of seasonal emissions distribution, consideration of weekday emissions 
schedules, and ADEQ's QA/QC process. Based on input from the EPA 
regarding the consideration of weekday emissions schedules and of the 
ozone season in the Yuma nonattainment area, ADEQ made corrections to 
some of its ozone season day emissions estimates compared to the values 
provided in the original 2020 Yuma SIP Suibmittal. All changes to 
estimations of ozone season day emissions are described in detail in 
the 2021 Yuma SIP Supplement.
    Estimates of 2017 ozone season day emissions of NOX and 
VOC in the Yuma area are summarized in Table 2 below.

                                                        Table 2--2017 Ozone Season Day Emissions
                                                              Yuma Ozone Nonattainment Area
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                                                                                    Ozone season day emissions (pounds per day)
                        Pollutant                        -----------------------------------------------------------------------------------------------
                                                               Point         Nonpoint     Nonroad mobile   Onroad mobile     Biogenic       Area total
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NOX.....................................................           1,113           1,275           2,158          10,402              38          14,986
VOC.....................................................             138          15,007           2,737           5,527           2,849          26,259
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Source: 2021 Yuma SIP Supplement, 6.

III. EPA's Evaluation

    Based on the documentation included in Arizona's submittals, the 
EPA finds that the submittals satisfy the procedural requirements of 
sections 110(a)(1) and 110(l) of the Act requiring states to provide 
reasonable notice and an opportunity for public hearing prior to 
adoption of SIP revisions. The 2020 Phoenix-Mesa SIP Submittal became 
complete by operation of law on January 8, 2021, and the 2020 Yuma SIP 
Submittal became complete by operation of law on June 22, 2021, 
pursuant to section 110(k)(1)(B).
    The EPA has reviewed Arizona's submittals for consistency with CAA 
sections 172(c)(3) and 182(a)(1) and the requirements for emissions 
inventories under the EPA's implementing regulations for the 2015 ozone 
NAAQS at 40 CFR 51.1315. The 2017 baseline emissions inventories 
represent the

[[Page 58635]]

most recent calendar year for which a consistent and comprehensive 
statewide inventory was available. The selection of a 2017 baseline 
year for the Phoenix-Mesa and Yuma emissions inventories is therefore 
consistent with the requirement for selection of RFP baseline years 
under 40 CFR 51.1310(b). We find that the Phoenix-Mesa and Yuma 
emissions inventories appropriately estimated the average day's 
emissions for a typical weekday in the ozone season, consistent with 
the definition of ozone season day emissions under 40 CFR 51.1300(q).
    Arizona's submittals document the procedures used by MAG and ADEQ 
to estimate ozone season day emissions for each of the major source 
types. Documentation of emissions estimation procedures in the 2020 
Phoenix-Mesa SIP Submittal and 2020 Yuma SIP Submittal demonstrate that 
MAG and ADEQ followed acceptable procedures to develop emissions 
estimates. The 2020 Phoenix-Mesa SIP Submittal and 2020 Yuma SIP 
Submittal each also describe the specific QA/QC measures implemented to 
ensure the accuracy and integrity of data throughout the development of 
each respective emissions inventory.
    Based upon the documentation of emissions estimation techniques and 
QA/QC procedures employed to develop the emissions inventories in each 
submittal, we find that the 2020 Phoenix-Mesa SIP Submittal and 2020 
Yuma SIP Submittal contain comprehensive, accurate, current inventories 
of actual emissions from all sources in the Phoenix-Mesa and Yuma ozone 
nonattainment areas, respectively. The EPA thereby proposes to approve 
the baseline inventories of NOX and VOC emissions for the 
Phoenix-Mesa and Yuma ozone nonattainment areas for the 2015 ozone 
NAAQS submitted by Arizona pursuant to 40 CFR 51.1315 and CAA sections 
172(c)(3) and 182(b)(1) .

IV. Proposed Action and Request for Public Comment

    We are proposing to approve the 2020 Phoenix-Mesa SIP Submittal and 
2020 Yuma SIP Submittal as meeting the ozone-related baseline emissions 
inventory requirement for the Phoenix-Mesa and Yuma ozone nonattainment 
areas for the 2015 ozone NAAQS. The emissions inventories we are 
proposing to approve into the SIP are summarized in tables 1 and 2 of 
this notice. We are proposing to approve the emissions inventories 
because they contain comprehensive, accurate, and current inventories 
of actual emissions for all relevant sources in accordance with CAA 
sections 172(c)(3) and 182(a). The EPA is soliciting public comments on 
the issues discussed in this proposed rule. We will accept comments 
from the public on this proposal for the next 30 days.

V. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a 
SIP submission that complies with the provisions of the Act and 
applicable federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). 
Thus, in reviewing SIP submissions, the EPA's role is to approve state 
choices, provided that they meet the criteria of the Clean Air Act. 
Accordingly, this proposed action merely proposes to approve state 
plans as meeting federal requirements and does not impose additional 
requirements beyond those imposed by state law. For that reason, this 
proposed action:
     Is not a ``significant regulatory action'' subject to 
review by the Office of Management and Budget under Executive Orders 
12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 
2011);
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of Section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the Clean Air Act; and
     Does not provide the EPA with the discretionary authority 
to address disproportionate human health or environmental effects with 
practical, appropriate, and legally permissible methods under Executive 
Order 12898 (59 FR 7629, February 16, 1994).
    In addition, the SIP is not approved to apply on any Indian 
reservation land or in any other area where the EPA or an Indian tribe 
has demonstrated that a tribe has jurisdiction. The Fort McDowell 
Yavapai Nation, the Gila River Indian Community of the Gila River 
Indian Reservation, the Tohono O'odham Nation of Arizona, and the Salt 
River Pima Maricopa Indian Community of the Salt River Reservation have 
areas of Indian country located within the Phoenix-Mesa nonattainment 
area for the 2015 ozone NAAQS. The Cocopah Tribe of Arizona and the 
Quechan Tribe of the Fort Yuma Indian Reservation have areas of Indian 
country located within the Yuma nonattainment area for the 2015 ozone 
NAAQS. In those areas of Indian country, the proposed rule does not 
have tribal implications and will not impose substantial direct costs 
on tribal governments or preempt tribal law as specified by Executive 
Order 13175 (65 FR 67249, November 9, 2000).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Ozone, Reporting and 
recordkeeping requirements, Volatile organic compounds.

    Authority: 42 U.S.C. 7401 et seq.

    Dated: October 9, 2021.
Deborah Jordan,
Acting Regional Administrator, Region IX.
[FR Doc. 2021-22662 Filed 10-21-21; 8:45 am]
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