[Federal Register Volume 86, Number 234 (Thursday, December 9, 2021)]
[Proposed Rules]
[Pages 70070-70078]
[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

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:<PHONE_NUMBER> 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

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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    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\)
------------------------------------------------------------------------
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

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.

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.

   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

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

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