Air Plan Approval; Arizona; Bullhead City; Second 10-Year PM10, 70070-70078 [2021-26619]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 86, Number 234 (Thursday, December 9, 2021)]
[Proposed Rules]
[Pages 70070-70078]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-26619]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2021-0819; FRL-9266-01-R9]


Air Plan Approval; Arizona; Bullhead City; Second 10-Year PM10 
Limited Maintenance Plan

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve a revision to the Bullhead City portion of

[[Page 70071]]

the Arizona State Implementation Plan (SIP). These revisions concern 
the second 10-year maintenance plan for Bullhead City for the 1987 
National Ambient Air Quality Standards (NAAQS or ``standards'') for 
particulate matter less than 10 micrometers in diameter 
(PM10).

DATES: Comments must be received on or before January 10, 2022.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2021-0819 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. 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: Panah Stauffer, EPA Region IX, 75 
Hawthorne St., San Francisco, CA 94105. By phone: (415) 972-3247 or by 
email at [email protected].

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

Table of Contents

I. Background
    A. Clean Air Act Requirements and Air Quality Designations
    B. Limited Maintenance Plan Option for the Bullhead City Area
II. Arizona's SIP Submittal
III. The EPA's Evaluation of Arizona's SIP Submittal
    A. Procedural Requirements
    B. Limited Maintenance Plan Option
    C. Additional Maintenance Plan Requirements
    D. Transportation and General Conformity Requirements
IV. The EPA's Proposed Action

I. Background

A. Clean Air Act Requirements and Air Quality Designations

    The EPA has established health-based standards for PM10. 
On July 1, 1987, the EPA promulgated two standards for PM10: 
A 24-hour standard of 150 micrograms per cubic meter ([micro]g/m\3\) 
and an annual PM10 standard of 50 [micro]g/m\3\.\1\ 
Effective December 18, 2006, the EPA revoked the annual PM10 
standard but retained the 24-hour PM10 standard.\2\ In this 
document, references to the PM10 NAAQS or PM10 
standard refer to the 24-hour average standard of 150 [micro]g/m\3\, 
unless otherwise noted.
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    \1\ 52 FR 24634 (July 1, 1987).
    \2\ 71 FR 61144 (October 17, 2006).
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    Under section 107(d) of the CAA, the EPA is required to designate 
areas of the country, based on ambient air quality data, as attainment, 
unclassifiable, or nonattainment for each NAAQS. Under the CAA 
Amendments of 1990, the Bullhead City area was designated as part of a 
large ``unclassifiable'' area in Arizona for the PM10 
NAAQS.\3\ In 1993, in light of PM10 NAAQS violations 
monitored in 1989 and 1990, the EPA redesignated the Bullhead City air 
quality planning area as a ``Moderate'' nonattainment area for the 
PM10 standard.\4\ To meet the SIP planning requirements for 
such areas, state and local agencies adopted and implemented a number 
of control measures to reduce PM10 emissions and lower 
ambient PM10 concentrations in the Bullhead City area, 
including paving of certain unpaved roads. In 2002, the EPA determined 
that the Bullhead City area had attained the PM10 NAAQS by 
the applicable attainment date of December 31, 2000.\5\ The 24-hour 
standard is attained when the expected number of days with levels above 
150 [micro]g/m\3\ (averaged over a 3-year period) is less than or equal 
to one.
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    \3\ For the definition of the Bullhead City maintenance area, 
see 40 CFR 81.303. The Bullhead City maintenance area is located in 
western Arizona. The original nonattainment area was defined by the 
equivalent of approximately six townships covering more than 200 
square miles: T21N, R20-21W, excluding Lake Mead National Recreation 
area; T20N, R20-22W; and T19N, R21-22W, excluding the Fort Mohave 
Indian Reservation. On June 26, 2002, the EPA approved the State's 
request that some areas of undisturbed desert terrain containing no 
industrial or commercial activity be excluded from the Bullhead City 
PM10 planning area (67 FR 43020, 43022). As a result of 
the boundary change, the townships comprising the maintenance area 
include: T21N, R21W, excluding Lake Mead National Recreation Area; 
T20N, R21-22W; and T19N, R22W, excluding the Fort Mohave Indian 
Reservation.
    \4\ 58 FR 67334 (December 21, 1993).
    \5\ 67 FR 7082 (February 15, 2002).
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B. Limited Maintenance Plan Option for the Bullhead City Area

    Under CAA section 175A, one of the criteria for an area to be 
redesignated from nonattainment to attainment is the approval of a 
maintenance plan. The maintenance plan must, among other requirements, 
ensure control measures are in place such that the area will continue 
to maintain the standard for the period extending 10 years after 
redesignation and include contingency provisions to assure that 
violations of the NAAQS will be promptly remedied.
    In 2002, the Arizona Department of Environmental Quality (ADEQ) 
submitted a maintenance plan, titled ``Bullhead City Moderate Area 
PM10 Maintenance Plan and Request for Redesignation to 
Attainment'' (February 2002) (``First 10-Year Limited Maintenance 
Plan'' or ``First 10-Year LMP'') to the EPA as a revision to the 
Arizona SIP, and requested that the EPA redesignate the Bullhead City 
area to attainment.\6\ The First 10-Year LMP provided for maintenance 
of the PM10 NAAQS in the Bullhead City area for 10 years 
after redesignation. On June 26, 2002, the EPA approved the First 10-
Year LMP for the Bullhead City area as providing for maintenance 
through 2012.\7\
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    \6\ ADEQ, Bullhead City Moderate Area PM10 
Maintenance Plan and Request for Redesignation to Attainment, 
February 2002.
    \7\ 67 FR 43020.
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    The EPA's primary guidance on maintenance plans is a 1992 
memorandum entitled ``Procedures for Processing Requests to Redesignate 
Areas to Attainment'' (``Calcagni memo'').\8\ In August 2001, the EPA 
issued guidance on streamlined maintenance plan provisions for certain 
Moderate PM10 nonattainment areas seeking redesignation to 
attainment (``LMP policy'').\9\ Herein, the option set forth in the LMP 
policy is referred to as the ``LMP option.''
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    \8\ Memorandum dated September 4, 1992 from John Calcagni, 
Director, Office of Air Quality Planning and Standards, to Directors 
of EPA Regional Air Programs.
    \9\ Memorandum dated August 9, 2001, from Lydia Wegman, 
Director, Office of Air Quality Planning and Standards, to Directors 
of EPA Regional Air Programs entitled ``Limited Maintenance Plan 
Option for Moderate PM10 Nonattainment Areas'' or ``LMP 
policy.''
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    The LMP policy does not require areas to project a demonstration of 
maintenance into the future. Instead, the LMP policy allows areas 
meeting certain air quality criteria to use a statistical

[[Page 70072]]

method to demonstrate, with a high degree of probability, that the area 
will maintain the standard 10 years into the future. The maintenance 
demonstration requirement of the Act is considered to be satisfied when 
a moderate nonattainment area meets the air quality criteria outlined 
in the LMP policy, and there is no need for qualifying areas to project 
emissions over the maintenance period.
    To qualify for the LMP option for redesignation to attainment, the 
area should be attaining the 1987 24-hour PM10 NAAQS and the 
average PM10 24-hour design value concentration, based upon 
the most recent five years of air quality data at all monitors in the 
area, should be at or below 98 [mu]g/m\3\ or the respective site-
specific critical design value (CDV). The CDV is a calculated design 
value concentration that indicates the area has a low probability (1 in 
10) of exceeding the NAAQS in the future. In addition, the area should 
expect only limited growth in on-road motor vehicle PM10 
emissions (including fugitive dust) and should have passed a motor 
vehicle regional emissions analysis test. The LMP option also 
identifies core provisions that must be included in all LMPs. These 
provisions include an attainment year emissions inventory, assurance of 
continued operation of an EPA-approved air quality monitoring network, 
and contingency provisions. If the State determines that the area in 
question meets the above criteria, it may select the LMP option for the 
first 10-year maintenance period.\10\
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    \10\ Id.
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    The LMP policy also states that once the LMP option is in effect, 
the state must verify in each subsequent year that the area still 
qualifies for the LMP option by recalculating the area's average design 
value concentration annually and determining that the LMP criteria are 
met for that year.
    As noted above, in June 2002, the EPA approved the First 10-Year 
LMP for the Bullhead City area. This action affirmed that Bullhead 
City's plan met the limited maintenance plan requirements through 2012 
and redesignated the area to attainment for the PM10 NAAQS.

II. Arizona's SIP Submittal

    CAA section 175A(b) requires states to submit an additional SIP 
revision to maintain the NAAQS for 10 years after the expiration of the 
10-year period covered by the initial maintenance plan approved in 
connection with the redesignation of the area from nonattainment to 
attainment. On May 24, 2012, ADEQ submitted a second 10-year 
maintenance plan, titled ``Limited Maintenance Plan Update for the 
Bullhead City PM10 Maintenance Area'' (May 2012) (``2012 
Bullhead City Second 10-Year LMP'' or ``Second 10-Year LMP''), to meet 
the requirement for the subsequent maintenance plan under CAA section 
175A(b). The 2012 Bullhead City Second 10-Year LMP is intended to 
provide for continued maintenance of the PM10 NAAQS for the 
10-year period following the end of the first 10-year period, i.e., 
through June 2022.
    Consistent with the requirements at the time, the First 10-year LMP 
provided for maintenance of both the 24-hour average and annual average 
PM10 NAAQS. However, since then (as noted above), the EPA 
has revoked the annual average PM10 NAAQS, and thus, the 
Second 10-Year LMP addresses only maintenance of the 24-hour 
PM10 NAAQS.

III. The EPA's Evaluation of Arizona's SIP Submittal

A. Procedural Requirements

    Section 110(l) of the act requires states to provide reasonable 
notice and public hearing prior to adoption of SIP revisions. Documents 
in ADEQ's submittal describe the public review process followed by ADEQ 
for the Second 10-year LMP for the Bullhead City area prior to adoption 
and submittal to the EPA as a revision to the Arizona SIP. The 
documentation provides evidence that reasonable notice of a public 
hearing was provided, and a public hearing was conducted prior to 
adoption.
    The documentation is found in Enclosure 4 of the May 24, 2012 
submittal. Enclosure 4 includes evidence that reasonable notice of a 
public hearing was provided to the public and that a public hearing was 
conducted prior to adoption. Specifically, the affidavit of publication 
included in Enclosure 4 shows that notices of a public hearing and the 
opening of a comment period of at least 30 days for the 2012 Bullhead 
City Second 10-Year LMP were published on March 23, 2012 and March 30, 
2012, in a newspaper of general circulation within the Bullhead City 
area. The public hearing was held on May 3, 2012. No comments were 
received during the public comment period or at the public hearing. 
ADEQ adopted the plan and submitted it to the EPA for approval on May 
24, 2012.
    Based on the documentation provided in Enclosure 4 of the 2012 
Bullhead City Second 10-Year LMP, we find that the submittal of the 
plan as a SIP revision satisfies the procedural requirements of section 
110(l) of the Act.

B. Limited Maintenance Plan Option

    Bullhead City qualified for the LMP option in 2002 for the first 
10-year maintenance period. ADEQ's second 10-year maintenance plan 
provides the same categories of information as the first plan, based on 
the LMP option. In addition, the majority of the second maintenance 
period, which ends in 2022, has already passed and the area has not 
violated the standard during this period. For the reasons given below, 
we conclude that the Bullhead City area continues to qualify for the 
LMP option and that the 2012 Bullhead City Second 10-Year LMP meets all 
applicable requirements for subsequent maintenance plans under CAA 
section 175A(b).
1. Continued Attainment of the NAAQS
    The first criterion for the LMP option is attainment of the NAAQS. 
Generally, the EPA determines whether an area's air quality is meeting 
the PM10 NAAQS based upon complete,\11\ quality-assured, and 
certified data gathered at established state and local air monitoring 
stations (SLAMS) in the nonattainment area and entered into the EPA Air 
Quality System (AQS) database. Data from air monitors operated by 
state, local, or tribal agencies in compliance with EPA monitoring 
requirements must be submitted to AQS. These monitoring agencies 
certify annually that these data are accurate to the best of their 
knowledge. Accordingly, the EPA relies primarily on data in AQS when 
determining the attainment status of an area.\12\ All valid data are 
reviewed to determine the area's air quality status in accordance with 
40 CFR part 50, Appendix K.
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    \11\ For PM10, a ``complete'' set of data includes a 
minimum of 75 percent of the scheduled PM10 samples per 
quarter. See 40 CFR part 50, appendix K, section 2.3(a).
    \12\ 40 CFR 50.6; 40 CFR part 50, appendix J; 40 CFR part 53; 
and 40 CFR part 58, appendices A, C, D, and E.
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    The PM10 standard is attained when the expected number 
of exceedances averaged over a three-year period is less than or equal 
to one. The expected number of exceedances averaged over a three-year 
period at any given monitor is known as the PM10 design 
value. The PM10 design value for the area is the highest 
design value within the nonattainment area. Three consecutive years of 
air quality data are required to show attainment of the PM10 
standard.\13\
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    \13\ 40 CFR part 50, appendix K.

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[[Page 70073]]

    ADEQ is responsible for monitoring ambient air quality in the 
Bullhead City area and submits annual monitoring network plans to the 
EPA. The annual monitoring network plans submitted to the EPA discuss 
the status of, and describe the air monitoring network operated by 
ADEQ, as required under 40 CFR 58.10. The EPA reviews these annual 
monitoring network plans for compliance with the applicable reporting 
requirements in 40 CFR part 58. With respect to PM10, the 
EPA has found that ADEQ's annual monitoring network plans meet the 
applicable reporting requirements for the area under 40 CFR part 58. 
The EPA has also found that ADEQ currently meets or exceeds the 
requirements for the minimum number of SLAMS for PM10 in the 
Lake Havasu City-Kingman, AZ Metropolitan Statistical Area (MSA), which 
includes the Bullhead City PM10 maintenance area.\14\
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    \14\ Letter dated October 29, 2021, from Gwen Yoshimura, 
Manager, Air Quality Analysis Office, EPA Region IX, to Daniel 
Czecholinski, Director, Air Quality Division, Arizona Department of 
Environmental Quality.
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    The EPA also concluded from its 2018 Technical System Audit (TSA) 
that ADEQ's air monitoring program meets EPA requirements.\15\ ADEQ 
annually certifies that the data it submits to the AQS database are 
quality-assured.\16\
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    \15\ Letter dated April 25, 2019, from Elizabeth J. Adams, 
Director, Air Quality Analysis Office, EPA Region IX, to Timothy J. 
Franquist, Director, Air Quality Division, Arizona Department of 
Environmental Quality.
    \16\ Letter dated April 26, 2021, from Daniel Czecholinski, 
Director, Air Quality Division, Arizona Department of Environmental 
Quality to Gwen Yoshimura, Manager, Air Quality Analysis Office, EPA 
Region 9.
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    Since November 1997, ADEQ has operated a SLAMS PM10 
monitor in Bullhead City (AQS ID: 04-015-1003), located at the U.S. 
Post Office Building northeast of SR 95 and 7th Street. The surrounding 
area is commercial and residential to the west and south. The Colorado 
River lies to the west less than 300 meters. To the northeast/east, 
about 675 meters, is the Bullhead City Airport. The Second 10-Year LMP 
was submitted to EPA in 2012 and analyzes monitoring data from 2006-
2010 for LMP qualification. During those years, ADEQ was operating the 
Bullhead City monitor on a once-every-sixth-day sampling schedule. ADEQ 
later switched to daily sampling in July 2012.
    Table 1 shows the maximum monitored 24-hour PM10 
concentrations at the Bullhead City monitoring site for 2001-2020. The 
table reflects that values for the Bullhead City area are typically 
well below the PM10 NAAQS of 150 [micro]g/m\3\, with some 
exceedances measured in 2012, 2013, and 2020.

       Table 1--Bullhead City PM10 Maximum 24-Hour Concentrations
     [Bullhead City Monitor, AQS Identification Number 04-015-1003]
------------------------------------------------------------------------
                                                             Maximum
                          Year                            concentration
                                                         ([micro]g/m\3\)
------------------------------------------------------------------------
2001...................................................               39
2002...................................................               55
2003...................................................               44
2004...................................................               48
2005...................................................               48
2006...................................................               72
2007...................................................               52
2008...................................................               46
2009...................................................               98
2010...................................................               33
2011...................................................              132
2012...................................................              185
2013...................................................              208
2014...................................................              108
2015...................................................               69
2016...................................................              119
2017...................................................              125
2018...................................................              118
2019...................................................               92
2020...................................................              185
------------------------------------------------------------------------
Source: EPA Air Quality System Quicklook Report 2001-2021, accessed
  November 5, 2021.

    Table 2 shows the estimated number of exceedances for the Bullhead 
City PM10 area for the three-year design value periods 
starting in 2001 and ending in 2020. The design values from 2001 
through 2007 were invalid due to incomplete quarters in 2001, 2002, and 
2005. However, there were no exceedances at the Bullhead City monitor 
from 2001 to 2007. Between the 2008 through 2020 design value periods, 
there were three exceedances of the NAAQS. However, no violations of 
the NAAQS (design values greater than 1.0) were recorded at the 
Bullhead City monitor from 2008 through 2020.

                Table 2--Bullhead City PM10 Design Values
     [Bullhead City Monitor, AQS Identification Number 04-015-1003]
------------------------------------------------------------------------
                                                           Design value
                   Design value period                      ([micro]g/
                                                               m\3\)
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1999-2001...............................................         \a\ 0.0
2000-2002...............................................         \a\ 0.0
2001-2003...............................................         \a\ 0.0
2002-2004...............................................         \a\ 0.0
2003-2005...............................................         \a\ 0.0
2004-2006...............................................         \a\ 0.0
2005-2007...............................................         \a\ 0.0
2006-2008...............................................             0.0
2007-2009...............................................             0.0
2008-2010...............................................             0.0
2009-2011...............................................             0.0
2010-2012...............................................         \b\ 0.3
2011-2013...............................................         \b\ 0.7
2012-2014...............................................         \b\ 0.7
2013-2015...............................................             0.3
2014-2016...............................................             0.0
2015-2017...............................................             0.0
2016-2018...............................................             0.0
2017-2019...............................................             0.0
2018-2020...............................................             0.3
------------------------------------------------------------------------
Sources: EPA Air Quality System Design Value Report 2001-2020, accessed
  November 5, 2021, and EPA PM10 Design Value Spreadsheet, August 6th,
  2015.
\a\ Invalid design value due to incomplete data in data years 2001,
  2002, and 2005.
\b\ Due to a method change-out, AQS does not reflect the combination of
  the methods; however, the 2014 EPA PM10 design value spreadsheets
  manually calculated these design values.

    As such, based on complete, quality-assured and certified data for 
the 2010 design value, we conclude that the Second 10-Year LMP 
submittal accurately reflected that the Bullhead City area was 
attaining the standard. Similarly, the most recent design value for 
2020 continues to reflect attainment of the standard.
2. Five-Year Average Design Value Concentrations
    The LMP guidance provides two methods for review of monitoring data 
for the purpose of meeting the second criterion for the LMP option. The 
first method is a comparison of a site's average design value 
concentration, based on the most recent 5 years of data, to 98 
[micro]g/m\3\ for the 24-hour PM10 NAAQS. If the area cannot 
meet this test, then a second test can be calculated for determination 
of qualification. This second method is a comparison of the site-
specific CDV with the site's average design value concentration. The 
CDV is a margin of safety value and is the value at which an area has 
been determined to have a 1 in 10 probability of exceeding the NAAQS.

  Table 3--Bullhead City PM10 Design Concentrations and 3-Year Average
                       Design Value Concentrations
     [Bullhead City Monitor, AQS Identification Number 04-015-1003]
------------------------------------------------------------------------
                                                              Design
                   Design value years                     concentration
                                                           ([mu]g/m\3\)
------------------------------------------------------------------------
2006-2008..............................................               72
2007-2009..............................................               98

[[Page 70074]]

 
2008-2010..............................................               98
                                                        ----------------
    Average Design Value Concentration (2006-2010).....               89
------------------------------------------------------------------------


  Table 4--Bullhead City PM10 Design Concentrations and 3-Year Average
                       Design Value Concentrations
     [Bullhead City Monitor, AQS Identification Number 04-015-1003]
------------------------------------------------------------------------
                                                              Design
                   Design value years                     concentration
                                                           ([mu]g/m\3\)
------------------------------------------------------------------------
2016-2018..............................................              110
2017-2019..............................................               92
2018-2020..............................................              102
                                                        ----------------
    Average Design Value Concentration (2016-2020).....              101
------------------------------------------------------------------------

    ADEQ's Second 10-Year LMP submittal included data from 2006-2010. 
As noted in Table 3 above, the average design value concentration for 
that five-year period was 89 [micro]g/m\3\. Because the average design 
value concentration was below 98 [micro]g/m\3\, the area qualified for 
the LMP average PM10 design value concentration criterion 
based on the first method in the LMP guidance.\17\ We also evaluated 
the most recent five-year period of 2016-2020; the average design value 
concentration was 101 [micro]g/m\3\, as noted in Table 4 above. Because 
the average design value concentration was above 98 [mu]g/m\3\ from 
2016-2020, we conducted the additional comparison of the site-specific 
CDV with the site's average design value concentration and calculated a 
site-specific CDV for 2016-2020 of 128 [mu]g/m\3\.\18\ Because the 
average design value concentration was below the site-specific CDV, the 
area also qualified for the LMP average PM10 design value 
concentration criterion for 2016-2020 based on the second method in the 
LMP guidance. Based on both the time period in the Second 10-Year LMP 
submittal and the most recent five-year average design value 
concentration, the Bullhead City area meets the second criterion for 
the LMP option.\19\
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    \17\ In its Second 10-Year LMP submittal, ADEQ calculated the 
design value concentration for the years 2006-2010 as 98 [micro]g/
m\3\. That value was the maximum design concentration across all 
five years, rather than the average design value concentration (of 
the three most recent design value concentrations). We use the 
average design value concentration here of 89 [micro]g/m\3\ because 
that is the value the LMP option intended to be compared with the 
CDV threshold.
    \18\ Technical Support Document (TSD) for the EPA's Rulemaking 
for the Arizona State Implementation Plan; Bullhead City Area 2nd 
Period Limited Maintenance Plan (LMP); November 2021.
    \19\ Our TSD includes additional CDV information for 2013-2020 
(all complete data years with daily sampling).
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3. Motor Vehicle Regional Emissions Analysis Test
    The third criterion for the LMP option is referred to as the motor 
vehicle regional emissions analysis test. The methodology for this test 
is found in Attachment B to the LMP policy and is used to determine 
whether increased emissions from on-road mobile sources could, in the 
next 10 years, increase design value concentrations in the area. As a 
general matter, the methodology increases the monitor-based design 
value concentration based on the expected growth in motor vehicle 
traffic over the maintenance period. Specifically, the motor vehicle 
fraction of the design concentration is assumed to equal the motor 
vehicle fraction of the overall emissions inventory. The motor vehicle 
fraction of the design concentration is then multiplied by the 
projected percentage increase in vehicle miles traveled (VMT) in the 
area over the next 10 years. The product of this calculation is then 
added to the monitor-based design value concentration and compared with 
the 98 [mu]g/m\3\ or site-specific CDV.
    ADEQ calculated a site-specific CDV in its submittal for use in the 
motor vehicle regional emissions analysis test. ADEQ calculated its CDV 
with a 1 in 5 probability instead of the 1 in 10 probability provided 
in the LMP option. This made the site-specific CDV more stringent, or 
lower, and yielded a CDV of 101 [micro]g/m\3\.
    For comparison, EPA calculated a site-specific CDV for the same 
years using a 1 in 10 probability and using the average design value 
concentration, as described in the LMP option.\20\ This calculation 
yields 114 [micro]g/m\3\, which is higher than ADEQ's site-specific CDV 
calculation.
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    \20\ Technical Support Document (TSD) for EPA's Rulemaking for 
the Arizona State Implementation Plan; Bullhead City Area 2nd Period 
Limited Maintenance Plan (LMP); November 2021.
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    ADEQ's motor vehicle growth analysis demonstration yielded 99.6 
[micro]g/m\3\, which is lower than both site-specific CDV thresholds 
that ADEQ and the EPA calculated. However, ADEQ calculated the motor 
vehicle design value concentration based on the on-road mobile portion 
of the 2008 inventory instead of the entire mobile source emissions 
inventory. ADEQ also used the maximum design value concentration 
instead of the average design value concentration as the basis for 
calculating the motor vehicle fraction of the design concentration. 
Using the EPA's calculated average design value concentration of 89 
[micro]g/m\3\ and the full mobile source portion of the 2008 emissions 
inventory yields a motor vehicle design value concentration of 7.5 
[micro]g/m\3\ and a motor vehicle regional analysis value of 91.4 
[micro]g/m\3\.\21\
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    \21\ See the EPA's TSD for additional details on our 
calculation.
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    Both ADEQ's and the EPA's calculated motor vehicle regional 
analysis values are lower than ADEQ's calculated site-specific CDV 
threshold of 101 [micro]g/m\3\ and the EPA's calculated site-specific 
CDV threshold of 114 [micro]g/m\3\. Consequently, we confirm that the 
motor vehicle growth analysis the Second 10-Year LMP was within the 
margin of safety required by the LMP option. Therefore, the third 
criterion for eligibility for the LMP option for the second 10-year 
maintenance period is met. Both site-specific values of 101 [micro]g/
m\3\ and 114 [micro]g/m\3\ are significantly above the Bullhead City 
average design value concentration, thereby reaffirming the second 
criterion as well.
    In addition, the Second 10-Year LMP notes that Bullhead City is 
located in rural Mohave County. Like other rural counties, Bullhead 
City experienced population growth during the 1970s; this growth 
continued into the 1980s. Growth slowed in the 1990s and 2000s. The 
Second 10-Year LMP included Bullhead City's population of 39,540 as of 
the 2010 U.S. Census. The submittal noted that the population was 
projected to continue growing, but at a lower rate than had 
historically been observed. As of the 2020 Census, Bullhead City has a 
population of 41,348.\22\ Although not directly related to the LMP 
option criteria, the low population growth in Bullhead City appears 
consistent with the Second 10-Year LMP's projection of low vehicle 
growth.
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    \22\ https://www.census.gov/quickfacts/fact/table/bullheadcitycityarizona,mohavecountyarizona,AZ,US/POP010220 (last 
visited on October 25, 2021).
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    Under the LMP policy, the maintenance demonstration requirement 
under CAA section 175A is considered satisfied for areas meeting the 
three LMP criteria discussed above.

[[Page 70075]]

Because the Bullhead City area continues to meet the LMP criteria, we 
conclude that no further demonstration of maintenance through the 
second 10-year period is necessary.

C. Additional Maintenance Plan Requirements

1. Emissions Inventory
    The State's approved attainment plan should include an emissions 
inventory (attainment inventory), which can be used to demonstrate 
attainment of the NAAQS. The inventory should represent emissions 
during the same five-year period associated with air quality data used 
to determine whether the area meets the LMP applicability requirements.
    As part of the 2012 Bullhead City Second 10-Year LMP, ADEQ prepared 
a PM10 emissions inventory for 2008 for the Bullhead City 
area. 2008 is one of the years within the five-year period included in 
the Second 10-Year LMP PM10 design value concentration and 
thus is an acceptable inventory year. Based on ADEQ's estimates, shown 
in Table 5 below, on-road motor vehicles (including fugitive dust from 
entrainment of PM10 from travel on paved and unpaved roads, 
as well as exhaust, brake and tire wear) contributed approximately 8.4 
percent to the total PM10 inventory, while construction and 
windblown dust contributed 9.2 and 82.4 percent, respectively. 
Industrial sources contributed less than 0.1 percent.

Table 5--2008 Emissions Inventory for the Bullhead City PM10 Maintenance
                                  Area
------------------------------------------------------------------------
                                  Bullhead City
                                 maintenance area  Percent of total PM10
        Source category           PM10 emissions   emissions in Bullhead
                                 (tons per year)   City maintenance area
 
------------------------------------------------------------------------
Unpaved Roads--Fugitive Dust..             373.42  5.1
Paved Roads--Fugitive Dust....             223.88  3.0
Paved and Unpaved Roads--                   18.93  0.3
 Exhaust, Tire, and Brake Wear.
                               -----------------------------------------
    Subtotal--Motor Vehicles..             616.23  8.4
Construction..................                679  9.2
Windblown Dust................             6075.1  82.4
Industrial Sources............               5.26  Less than 0.1
                               -----------------------------------------
        Total.................           7,375.59  100
------------------------------------------------------------------------
Source: Table 3.6 (p. 18) of the 2012 Bullhead City Second 10-Year LMP.

    Section 3.2 of the 2012 Bullhead City Second 10-Year LMP describes 
the methodology used to develop the emissions inventory. The emissions 
inventory categories are the same as those identified in the first 10-
year LMP, and the methodology used to determine the contribution of 
sources is largely the same as was used in the first 10-year LMP. ADEQ 
used updated emissions factors for each source category based on 
current emissions models, vehicle activity, population, and employment 
figures.
    For instance, ADEQ updated motor vehicle emissions estimates using 
the EPA's National Mobile Inventory Model (NMIM) to develop emissions 
factors for motor vehicle exhaust, tire, and brake wear for motor 
vehicles. NMIM used the EPA's MOBILE6.2 emissions factors, which were 
the most current factors at the time the 2012 Bullhead City Second 10-
Year LMP was being developed. ADEQ used updated emissions factors in 
the EPA's Compilation of Air Pollutant Emissions Factors (AP-42) to 
estimate PM10 entrained by vehicle movement over paved 
roads. ADEQ also updated the non-mobile source inventory with 2008 
National Emissions Inventory (NEI) data, primarily by adjusting county-
specific estimates by the ratio of population in the Bullhead City area 
to the population of Mohave County. For point sources in Bullhead City, 
ADEQ used industrial source data collected in an annual survey of 
permitted facilities.
    During the period in which the draft 2012 Bullhead City Second 10-
Year LMP was being developed, the EPA replaced MOBILE6.2 with a new 
motor vehicle emission factor model, known as Motor Vehicle Emission 
Simulator (or ``MOVES''). In response to an EPA request to consider the 
impact on the inventory due to the release of MOVES, ADEQ re-calculated 
the motor vehicle emissions estimates using MOVES and projected a 17.9 
tons per year increase in emissions from motor vehicle exhaust, brake 
wear, and tire wear relative to the estimate made using MOBILE6.2.\23\ 
This incremental increase corresponded to a 0.24 [micro]g/m\3\ increase 
in ADEQ's motor vehicle regional analysis calculation. As such, use of 
MOVES, rather than MOBILE6.2, did not affect the continued eligibility 
of the Bullhead City area to use the LMP option.\24\
---------------------------------------------------------------------------

    \23\ ADEQ, ``Bullhead City Update using MOVES,'' November 8, 
2013.
    \24\ See the EPA's TSD for additional details.
---------------------------------------------------------------------------

    Based on our review of the methods, models, and assumptions used by 
ADEQ to develop the PM10 emissions inventory, we find that 
the 2012 Bullhead City Second 10-Year LMP includes a comprehensive 
inventory of PM10 emissions and conclude that the plan's 
inventory is acceptable for the purposes of a subsequent maintenance 
plan, in this case, a subsequent LMP, under CAA section 175A(b).
    Since submitting the Second 10-Year LMP, ADEQ has reported its 
emissions annually to the EPA under the Air Emissions Reporting Rule 
and has completed its reporting requirements for the 2011, 2014 and 
2017 National Emissions Inventories.\25\ For comparison with the 2008 
emissions inventory in the Second 10-Year LMP, ADEQ provided 2011, 2014 
and 2017 NEI data and windblown dust estimates for Bullhead City, as 
well as MOVES calculations for 2017.\26\ The 2017 data are shown in 
Table 6 below along with the percentage of total emissions for each 
category.
---------------------------------------------------------------------------

    \25\ The docket for this rulemaking includes a spreadsheet of 
ADEQ's statewide emissions data for the 2011, 2014 and 2017 National 
Emissions Inventories.
    \26\ Email dated October 26, 2021, from Jessica Wood, ADEQ, to 
Panah Stauffer, EPA Region IX, Subject: ``Bullhead City EI 
Analysis,'' and attached ``Bullhead EI workbook'' spreadsheet.

[[Page 70076]]



   Table 6--2017 Emissions for the Bullhead City PM10 Maintenance Area
------------------------------------------------------------------------
                                                       Percent of  total
           Source sector                2017 PM10       PM10  emissions
                                     emissions  (tpy)
------------------------------------------------------------------------
Unpaved Road Dust.................           1,526.05                7.0
Paved Road Dust...................             202.56                0.9
MOVES Tire, Exhaust, and Brake                  44.47                0.2
 wear.............................
                                   -------------------------------------
    Subtotal--Motor Vehicles......           1,773.09                8.1
------------------------------------------------------------------------
Construction......................             119.71                0.5
Windblown Dust....................          19,891.89               91.3
Industrial Sources................                  0                  0
                                   -------------------------------------
    Total.........................          21,784.69                100
------------------------------------------------------------------------

    The motor vehicle fraction of the emissions inventory is 
approximately 8 percent for 2017, which is similar to the motor vehicle 
percentage of the 2008 inventory. The emissions calculated in MOVES 
have also not changed significantly, from 36.88 tpy in 2008 to 44.47 
tpy in 2017. Construction dust in 2017 was approximately one-sixth of 
the 2008 emissions. All permitted industrial sources from the 2008 
inventory had terminated their permits, were no longer required to hold 
a permit, or had ceased operation as of 2017.\27\
---------------------------------------------------------------------------

    \27\ Id.
---------------------------------------------------------------------------

    The calculated windblown dust emissions were significantly higher 
in 2017 than in 2008. This is likely because of a change in the 
frequency of wind measurements at the Bullhead City airport. The 
Bullhead City Airport's meteorological station began taking wind 
measurements every 20 minutes on February 20, 2009. Prior to this, the 
monitor was taking hourly measurements for only 8-12 hours out of the 
day.\28\ Because the windblown dust figure is calculated using the 
number of hours when wind speed exceeded 24 mph, the lower frequency of 
readings and lower windblown dust figure in the 2008 inventory indicate 
that number in the Second 10-Year LMP was likely underestimated.\29\
---------------------------------------------------------------------------

    \28\ Id.
    \29\ The underestimated windblown dust figure in the 2008 
emissions inventory does not affect the area's eligibility for the 
LMP Option The criteria for attainment and a design value 
concentration that falls below the 98 [mu]g/m\3\ or site-specific 
CDV are unaffected by emissions inventory numbers. The motor vehicle 
criterion for LMP eligibility would only have been strengthened by a 
higher windblown dust figure for 2008 because the motor vehicle 
fraction of the inventory would have decreased.
---------------------------------------------------------------------------

    In general, the inventory that was provided in the Second 10-Year 
LMP was comprehensive, and recent emissions confirm our conclusions 
about the submitted inventory and the area's LMP eligibility. Further, 
as noted above, the area has stayed in attainment and its second 
maintenance period will end in June 2022.
2. Control Measures
    As discussed in our 2002 approval of the first 10-year LMP for the 
Bullhead City area, the measures that brought the area into attainment 
are permanent and enforceable.\30\ The 2012 Bullhead City Second 10-
Year LMP relies on the same control measures to continue to maintain 
the NAAQS for PM10 through 2022. These measures have not 
been revised and continue to be permanent and enforceable.
---------------------------------------------------------------------------

    \30\ 67 FR 43020 at 43025 (June 26, 2002).
---------------------------------------------------------------------------

3. PM10 Air Quality Monitoring Network
    As described earlier, ADEQ has operated a single PM10 
monitoring site in the Bullhead City area since November 1997. 
Operating a single monitor in this area is consistent with the EPA's 
monitoring requirements. In Section 6 of the Second 10-Year LMP, ADEQ 
committed ``to continue to operate an appropriate PM10 air 
quality monitoring network to verify the attainment status'' of the 
Bullhead City area in accordance with 40 CFR part 58. In 2012, ADEQ 
replaced the PM10 sampler that operated on a once every 
sixth-day sampling period with a continuous (hourly) monitor. ADEQ's 
monitoring network continues to meet EPA's requirements for Bullhead 
City.
4. Contingency Provisions
    Section 175A(d) states that a maintenance plan must include 
contingency provisions, as necessary, to ensure prompt correction of 
any violation of the NAAQS which may occur after redesignation of the 
area to attainment. These contingency provisions do not have to be 
fully adopted measures at the time of redesignation. However, the 
contingency provisions are considered to be an enforceable part of the 
SIP and the State should ensure that contingency measures are adopted 
as soon as possible once they are triggered by a specific event. The 
contingency provisions should identify the measure to be adopted and 
provide a schedule and procedure for adoption and implementation of the 
measure if required.
    In the Second 10-Year LMP, ADEQ has, in most respects, carried 
forward the contingency provisions adopted in the first 10-year LMP, 
which EPA approved in 2002. First, ADEQ committed to continue to submit 
annual reports to the EPA that will include calculation of the Bullhead 
City area PM10 design value concentration to verify 
continued attainment and continued eligibility to use the LMP 
option.\31\ ADEQ made a similar commitment in the first 10-year LMP and 
submitted reports of annual PM10 design value concentrations 
to the EPA for the first 10-year maintenance period. Since submitting 
the Second 10-Year LMP in 2012, ADEQ has continued to send reports of 
annual PM10 design value concentrations to the EPA. These 
annual reports are included in the docket for this proposed action.
---------------------------------------------------------------------------

    \31\ Section 6.0 of the 2012 Bullhead City Second 10-Year LMP.
---------------------------------------------------------------------------

    Second, as part of the contingency provisions, ADEQ committed to 
determine whether PM10 NAAQS violations have been recorded 
within six months of the close of each calendar year, and to review and 
determine the appropriate contingency measure(s) by the end of the same 
calendar year.\32\ Table 7 below lists the measures that ADEQ committed 
to consider for implementation in the event of a violation of the 
PM10 NAAQS or in the event the annual recalculation of the 
area's design value concentration exceeded the applicable LMP option

[[Page 70077]]

criteria. ADEQ noted, ``the cause of the violation or exceedance of the 
LMP option criteria will help to determine the appropriate contingency 
measure(s) to be implemented.''
---------------------------------------------------------------------------

    \32\ See section 5.3 of the 2012 Bullhead City Second 10-Year 
LMP.

            Table 7--Bullhead City Area Contingency Measures
------------------------------------------------------------------------
            Contingency measures                 Implementing entity
------------------------------------------------------------------------
Review of Bullhead City grading ordinance    Bullhead City.
 to determine if additional action is
 needed.
Increased enforcement efforts, or develop a  Bullhead City.
 compliance survey, for standards for the
 installation and maintenance of
 landscaping and screening (Bullhead City
 Zoning Regulation, Chapter 17.48,
 Landscaping and Screening Regulations).
Pave or stabilize unpaved roads located in   Bullhead City and/or Mohave
 the PM10 maintenance area.                   County.
Pave additional unpaved parking areas in     Mohave County.
 the Davis Camp Park (south beach parking
 areas).
Cleanup of roadways after rainstorms.......  Mohave County.
Increase enforcement efforts, or develop a   Mohave County.
 compliance survey, for the requirement for
 all commercial establishments to pave
 parking lots (Mohave County Zoning
 Regulations, Section 26 Off-Street Parking
 standards).
Exercise authority under the Enhanced Smoke  U.S. Forest Service, U.S.
 Management Plan--state and federal land      Bureau of Land Management,
 managers conducting prescribed burning       Arizona State Land
 must register with ADEQ for proposed         Department, ADEQ.
 burning activities (Arizona Administrative
 Code R18-2-Article 15--Forest & Range
 Management Burns). ADEQ maintains the
 ability to deny permission for burning on
 certain high risk days (dependent on
 meteorological conditions) and may
 increase outreach and enforcement
 resources.
Review of the requirement for dust control   ADEQ.
 measures for material storage piles to
 determine if revision is needed (A.A.C.
 R18-2-607.
------------------------------------------------------------------------
Source: 2012 Bullhead City Second 10-Year LMP, Section 5.3, p. 25.

    Finally, the State committed to implement the selected contingency 
measure(s) within one year of determining that a PM10 NAAQS 
violation has occurred. We conclude that these measures and commitments 
meet the requirements of CAA section 175A(d). The Bullhead City area 
did not violate the PM10 standard and has stayed in 
attainment with the PM10 NAAQS to date.

D. Transportation and General Conformity Requirements

    Section 176(c) of the CAA requires that all federal actions conform 
to an applicable SIP. Conformity is defined in section 176(c) of the 
Act as conformity to a SIP's purpose of eliminating or reducing the 
severity and number of violations of the NAAQS and achieving 
expeditious attainment of such standards, and that such activities will 
not: (1) Cause or contribute to any new violation of any standard in 
any area; (2) increase the frequency or severity of any existing 
violation of any standard in any area; or (3) delay timely attainment 
of any standard or any required interim emission reductions or other 
milestones in any area.
    The EPA has established criteria and procedures for federal 
agencies to follow in determining conformity of their actions. The 
EPA's rule governing transportation plans, programs, and projects 
approved or funded by the Federal Highway Administration or Federal 
Transit Administration is referred to as the ``transportation 
conformity'' rule,\33\ and the EPA's rule governing all other types of 
federal agency actions is referred to as the ``general conformity'' 
rule.\34\
---------------------------------------------------------------------------

    \33\ 40 CFR part 93, subpart A.
    \34\ 40 CFR part 93, subpart B.
---------------------------------------------------------------------------

    The transportation conformity rule and the general conformity rule 
apply to nonattainment and maintenance areas. Both rules provide that 
conformity can be demonstrated by showing that the expected emissions 
from planned actions are consistent with the emissions budget for the 
area. While the EPA's LMP option does not exempt an area from the need 
to affirm conformity, the LMP policy explains that the area may 
demonstrate conformity without submitting an emissions budget.
1. Transportation Conformity
    Under the conformity rule, areas submitting an LMP for the second 
10-year maintenance plan may demonstrate conformity without a regional 
emissions analysis as outlined in 40 CFR 93.109(e). Under the LMP 
option, emissions budgets are not treated as constraining for the 
length of the maintenance period because it is unreasonable to expect 
that qualifying areas would experience so much growth in that period 
that a violation of the NAAQS would result. Therefore, in areas with 
approved LMPs, federal actions requiring conformity determinations 
under the transportation conformity rule are considered to satisfy the 
``budget test'' required in 40 CFR 93.118.
    While areas with maintenance plans approved under the LMP option 
are not subject to the budget test, the areas remain subject to other 
transportation conformity requirements of 40 CFR part 93, subpart A. 
Because no metropolitan planning organization exists for Bullhead City, 
the Arizona Department of Transportation will still need to document 
and ensure that applicable conformity requirements are met. 
Specifically, for conformity determinations, projects will have to 
demonstrate that they are fiscally constrained (40 CFR 93.108) and meet 
the criteria for consultation (40 CFR 93.105 and 40 CFR 93.112) and 
timely implementation (as applicable) of Transportation Control 
Measures (40 CFR 93.113). Projects in the Bullhead City area will also 
be required to be evaluated for potential PM10 hot-spot 
issues to satisfy the ``project level'' conformity determination 
requirements. As appropriate, a project may then need to address the 
applicable criteria for a PM10 hot-spot analysis as provided 
in 40 CFR 93.116 and 40 CFR 93.123.
    Upon approval of the 2012 Bullhead City Second 10-Year LMP, the 
State (in this case, the Arizona Department of Transportation) will 
continue to be exempt from performing a regional emissions analysis but 
must continue to meet project-level analyses as well as the 
transportation conformity criteria mentioned above.
2. General Conformity
    Federal actions, other than transportation conformity, that meet 
specific criteria need to be evaluated with respect to the requirements 
of 40 CFR part 93, subpart B. The EPA's

[[Page 70078]]

general conformity rule requirements are designed to ensure that 
emissions from a federal action will not cause or contribute to new 
violations of the NAAQS, exacerbate current violations, or delay timely 
attainment. However, as noted in the LMP policy and similar to the 
above discussed transportation conformity provisions, federal actions 
subject to general conformity requirements would be considered to 
satisfy the ``budget test,'' as specified in 40 CFR 93.158(a)(5)(i)(A). 
As discussed above, the basis for this provision in the LMP policy 
memorandum is that it is unreasonable to expect that an LMP area will 
experience so much growth during the maintenance period that a 
violation of the PM10 NAAQS would result. Therefore, for 
purposes of general conformity, a general conformity PM10 
emissions budget does not need to be identified in the maintenance 
plan, nor submitted, and the emissions from federal agency actions are 
essentially considered to not be limited.

IV. The EPA's Proposed Action

    Under CAA section 110(k), the EPA is proposing to approve the 
Second 10-Year LMP for the Bullhead City air quality planning area for 
the PM10 NAAQS that was submitted by ADEQ on May 24, 2012, 
as a revision to the Arizona SIP. The EPA is approving this plan based 
on the conclusion that it adequately provides for continued maintenance 
of the PM10 NAAQS in the Bullhead City area through 2022 and 
thereby meets the requirements for subsequent maintenance plans under 
section 175A of the Act. The effect of this action is to make the 
State's continuing commitments with respect to maintenance of the 
PM10 NAAQS in the Bullhead City area federally enforceable 
for the second 10-year maintenance period. These commitments include 
continued monitoring; continued implementation of control measures that 
were responsible for bringing the area into attainment; preparation and 
submittal of annual reports; consideration and implementation of 
contingency measures, as necessary; and submittal of a full maintenance 
plan if contingency measures fail to provide the required remedy.

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 law 
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, there are no areas of Indian country within the 
Bullhead City planning area, and the State plan for which the EPA is 
proposing approval does not 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. In those areas of Indian country, this proposed 
action 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, Particulate matter, Reporting 
and recordkeeping requirements.

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

    Dated: December 2, 2021.
Deborah Jordan,
Acting Regional Administrator, EPA Region IX.
[FR Doc. 2021-26619 Filed 12-8-21; 8:45 am]
BILLING CODE 6560-50-P