[Federal Register Volume 86, Number 176 (Wednesday, September 15, 2021)]
[Proposed Rules]
[Pages 51318-51326]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-19801]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

[EPA-R10-OAR-2020-0305; FRL-8878-01-R10]


Air Plan Approval; ID; West Silver Valley Redesignation to 
Attainment for the 2012 Annual PM2.5 Standard

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
redesignate the West Silver Valley, Idaho nonattainment area to 
attainment for the 2012 annual fine particulate matter 
(PM<INF>2.5</INF>) National Ambient Air Quality Standard (NAAQS). EPA 
is also proposing to approve a maintenance plan for the area 
demonstrating continued compliance with the NAAQS through 2031, which 
the Idaho Department of Environmental Quality (IDEQ) submitted along 
with the redesignation request on June 2, 2020, for inclusion into the 
Idaho State Implementation Plan (SIP). Additionally, EPA is proposing 
to approve the 2031 motor vehicle emissions budgets included in Idaho's 
maintenance plan for PM<INF>2.5</INF>, nitrogen oxides (NO<INF>X</INF>) 
and volatile organic compounds (VOCs). EPA is proposing this action 
pursuant to the Clean Air Act (CAA or the Act).

DATES: Comments must be received on or before October 15, 2021.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R10-
OAR-2020-0305, at https://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from Regulations.gov. EPA may publish any comment 
received to its public docket. Do not electronically submit any 
information you consider to be Confidential Business Information (CBI) 
or other information the disclosure of which 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. 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, 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.

FOR FURTHER INFORMATION CONTACT: Claudia Vaupel, (206) 553-6121, 
<a href="/cdn-cgi/l/email-protection#a0d6c1d5c5d0cc8ec3ccc1d5c4c9c1e0c5d0c18ec7cfd6"><span class="__cf_email__" data-cfemail="146275617164783a77787561707d75547164753a737b62">[email protected]</span></a>.

SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,'' 
``us,'' or ``our'' is used, it is intended to refer to EPA.

Table of Contents

I. Background
II. Requirements for Redesignation to Attainment
III. EPA's Analysis of Idaho's Submittal
    A. Attainment Determination
    B. Applicable Requirements Under Section 110 and Part D of the 
CAA
    1. CAA Section 110 General SIP Requirements
    2. Part D of Title I Requirements
    C. Improvement in Air Quality Due to Permanent and Enforceable 
Measures
    D. Fully Approved Maintenance Plan
    1. Attainment Inventory
    2. Maintenance Demonstration
    3. Monitoring Network
    4. Verification of Continued Attainment
    5. Contingency Plan
    E. Requirements for Transportation Conformity and Motor Vehicle 
Emissions Budgets (MVEBs)
IV. Proposed Action
V. Statutory and Executive Order Reviews

I. Background

    On December 14, 2012, EPA promulgated a revised primary annual 
PM<INF>2.5</INF> NAAQS to provide increased protection of public health 
from fine particle pollution. 78 FR 3086 (January 15, 2013). In that 
action, EPA strengthened the primary annual PM<INF>2.5</INF> standard 
from 15.0 micrograms per cubic meter (mg/m\3\) to 12.0 mg/m\3\, which 
is attained when the 3-year average of the annual arithmetic means does 
not exceed 12.0 mg/m\3\. On December 18, 2014, EPA promulgated initial 
designations for the 2012 primary PM<INF>2.5</INF> NAAQS based on 2011-
2013 air quality monitoring data for the majority of the United States. 
80 FR 2206 (January 15, 2015). In that action, EPA designated the West 
Silver Valley in Shoshone County, Idaho as a moderate nonattainment 
area for the 2012 annual PM<INF>2.5</INF> NAAQS. See 40 CFR 81.313.
    On April 6, 2018, EPA published a ``finding of failure to submit'' 
required SIP elements for the 2012 annual PM<INF>2.5</INF> NAAQS for 
several nonattainment areas nationwide, including the West Silver 
Valley in Idaho. See 83 FR 14759. In particular, Idaho failed to submit 
the following specific moderate area SIP elements for the West Silver 
Valley: An attainment demonstration; control strategies, including 
reasonably available control measures (RACM) and reasonably available 
control technologies (RACT); a reasonable further progress (RFP) plan; 
quantitative milestones; and contingency measures. This finding 
triggered the sanctions clock under section 179 of the CAA, as well as 
an obligation under section 110(c) of the CAA for EPA to promulgate a 
Federal Implementation Plan no later than 2 years from the effective 
date of the finding, if Idaho has not submitted, and EPA has not 
approved, the required SIP submission.
    On December 21, 2018, EPA determined that the West Silver Valley 
attained the 2012 annual PM<INF>2.5</INF> NAAQS based on 2015-2017 
ambient air quality monitoring data and made a ``clean data 
determination.'' 83 FR 65535. A clean data determination suspends 
certain planning requirements for the area, including the requirement 
to submit an attainment demonstration and associated RACM, including 
RACT, an RFP plan, and contingency measures for failure to attain or 
meet RFP. These requirements are suspended as long as the area 
continues to meet the 2012 annual PM<INF>2.5</INF> NAAQS. When the area 
is redesignated to attainment, the requirements are permanently 
discharged.

II. Requirements for Redesignation to Attainment

    The CAA provides the requirements for redesignating a nonattainment 
area to attainment. Specifically, section 107(d)(3)(E) of the CAA, 42 
U.S.C. 7407(d)(3)(E), allows for redesignation provided that: (1) EPA 
determines that the area has attained the applicable NAAQS; (2) EPA has 
fully approved the applicable implementation plan for the area under 
section 110(k) of the CAA; (3) EPA determines that the improvement in 
air quality is due to permanent and enforceable reductions

[[Page 51319]]

in emissions resulting from implementation of the applicable SIP and 
applicable Federal air pollutant control regulations and other 
permanent and enforceable reductions; (4) EPA has fully approved a 
maintenance plan for the area as meeting the requirements of section 
175A of the CAA; and (5) the state containing such area has met all 
requirements applicable to the area under section 110 and part D of the 
CAA. In this proposed action, EPA will review CAA section 107(d)(3)(E) 
requirements (2) and (5) together as part of our evaluation of Idaho's 
redesignation request.
    EPA has provided guidance on redesignation in the CAA ``General 
Preamble,'' \1\ and has provided further guidance on processing 
redesignation requests in the following documents: (1) ``Procedures for 
Processing Requests to Redesignate Areas to Attainment,'' Memorandum 
from John Calcagni, Director, Air Quality Management Division, 
September 4, 1992 (Calcagni memorandum); (2) ``State Implementation 
Plan (SIP) Actions Submitted in Response to Clean Air Act (CAA) 
Deadlines,'' Memorandum from John Calcagni, Director, Air Quality 
Management Division, October 28, 1992; and (3) ``Part D New Source 
Review (Part D NSR) Requirements for Areas Requesting Redesignation to 
Attainment,'' Memorandum from Mary D. Nichols, Assistant Administrator 
for Air and Radiation, October 14, 1994. These documents are included 
in the docket for this proposed action.
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    \1\ See ``State Implementation Plans; General Preamble for the 
Implementation of Title I of the Clean Air Act Amendments of 1990,'' 
57 FR 13498, April 16, 1992.
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III. EPA's Analysis of Idaho's Submittal

    EPA is proposing to redesignate the West Silver Valley to 
attainment for the 2012 annual PM<INF>2.5</INF> NAAQS and to approve 
Idaho's related maintenance plan. EPA's proposed approval of the 
redesignation request and maintenance plan is based upon EPA's 
determination that the area continues to attain the 2012 annual 
PM<INF>2.5</INF> NAAQS and that all other redesignation criteria have 
been met for the area. The following is a description of how Idaho's 
June 2, 2020, submission satisfies the requirements of section 
107(d)(3)(E) of the CAA for the 2012 annual PM<INF>2.5</INF> standard.

A. Attainment Determination

    To redesignate an area from nonattainment to attainment, the CAA 
requires EPA to determine that the area has attained the applicable 
NAAQS (CAA section 107(d)(3)(E)(i)). An area is attaining the 2012 
annual PM<INF>2.5</INF> NAAQS if it meets the standard, as determined 
in accordance with 40 CFR 50.13 and appendix N of 40 CFR part 50. To 
attain the 2012 annual PM<INF>2.5</INF> NAAQS, the 3-year average of 
the annual arithmetic mean concentration, as determined in accordance 
with 40 CFR part 50, appendix N, must be less than or equal to 12.0 mg/
m\3\ at all relevant monitoring sites in the subject area over a 3-year 
period. The relevant data must be collected and quality-assured in 
accordance with 40 CFR part 58 and recorded in EPA's Air Quality System 
(AQS) database.
    There is one PM<INF>2.5</INF> ambient air quality monitor in the 
West Silver Valley, located in Pinehurst, Idaho (AQS ID 160790017). As 
noted, EPA first determined that the West Silver Valley attained the 
2012 annual PM<INF>2.5</INF> NAAQS based on 2015-2017 ambient air 
quality monitoring data at this monitor on December 21, 2018. 83 FR 
65535.
    EPA has reviewed the certified, quality-controlled and quality-
assured PM<INF>2.5</INF> Pinehurst monitoring data for the 2018-2020 
design value period and determined that the design value is 10.9 mg/
m\3\, which is less than or equal to 12.0 mg/m\3\, and therefore the 
area continues to meet the 2012 annual PM<INF>2.5</INF> NAAQS. On this 
basis, EPA is proposing to determine that the West Silver Valley is 
attaining the 2012 annual PM<INF>2.5</INF> NAAQS. The monitoring data 
is summarized in Tables 1 and 2 is also available in the docket for 
this action available online at https://www.regulations.gov, Docket ID: 
EPA-R10-OAR-2020-0305.

                   Table 1--2015 to 2020 PM2.5 Annual Means in the West Silver Valley in Idaho
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                                                                         Annual means in [mu]g/m\3\
                Area/county                 Monitor AQS ID -----------------------------------------------------
                                                              2015     2016    2017 *    2018     2019     2020
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Pinehurst/Shoshone........................       160790017     13.6      9.3     12.3     12.8     9.63     11.1
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* EPA excluded five 24-hr PM2.5 values during September 2017 because those NAAQS exceedances were caused by a
  wildfire exceptional event. (See 83 FR 65535, December 21, 2018).


               Table 2--2015 to 2020 PM2.5 Annual Design Values in the West Silver Valley in Idaho
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                                                                Annual design values in [mu]g/m\3\
           Area/county            Monitor AQS ID ---------------------------------------------------------------
                                                    2015-2017 *     2016-2018 *     2017-2019 *      2018-2020
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Pinehurst/Shoshone..............       160790017            11.7            11.2            11.3            10.9
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* EPA excluded five 24-hr PM2.5 values during September 2017 because those NAAQS exceedances were caused by a
  wildfire exceptional event. (See 83 FR 65535, December 21, 2018).

B. Applicable Requirements Under Section 110 and Part D of the CAA

    In accordance with section 107(d)(3)(E)(v) of the CAA, Idaho must 
meet all the requirements applicable to the West Silver Valley under 
section 110 of the CAA (general SIP requirements) and part D of title I 
of the CAA (SIP requirements for nonattainment areas). Under section 
107(d)(3)(E)(ii) of the CAA, Idaho's SIP revisions for the 2012 annual 
PM<INF>2.5</INF> NAAQS for the West Silver Valley must be fully 
approved under section 110(k) of the CAA. Section 110(k) of the CAA 
sets out the requirements for EPA's actions on SIP revision submittals.
    The September 4, 1992 Calcagni memorandum describes EPA's 
interpretation of section 107(d)(3)(E) with respect to the timing of 
applicable requirements. Under this interpretation, to qualify for 
redesignation, states requesting redesignation to attainment must meet 
only the relevant CAA requirements that come due prior to the

[[Page 51320]]

submittal of a complete redesignation request. See also Shapiro 
memorandum, September 17, 1993,\2\ and 60 FR 12459, 12465-12466, (March 
7, 1995) (redesignation of Detroit-Ann Arbor). Applicable requirements 
of the CAA that come due subsequent to the area's submittal of a 
complete redesignation request remain applicable until a redesignation 
is approved but are not required as a prerequisite to redesignation. 
See CAA section 175A(c). Sierra Club v. EPA, 375 F .3d 537 (7th Cir. 
2004). See also 68 FR 25418, 25424 and 25427 (May 12, 2003) 
(redesignation of the St. Louis/East St. Louis area to attainment of 
the 1-hour ozone NAAQS).
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    \2\ ``State Implementation Plan (SIP) Requirements for Areas 
Submitting Requests for Redesignation to Attainment of the Ozone and 
Carbon Monoxide (CO) National Ambient Air Quality Standards (NAAQS) 
on or after November 15, 1992,'' Memorandum from Michael H. Shapiro, 
Acting Assistant Administrator, Air and Radiation, September 
17,1993.
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    In the case of the West Silver Valley, the base year emissions 
inventory was due prior to Idaho's submittal of the complete 
redesignation request for the area. Therefore, the base year inventory 
is an applicable requirement. The attainment plan, including RACM/RACT, 
and contingency measures for failure to attain or meet RFP, were also 
due prior to Idaho's submittal of complete redesignation requests for 
the West Silver Valley. However, as described in detail later in this 
notice of proposed rulemaking (NPRM), the clean data determination 
suspended these requirements for as long as the West Silver Valley 
continues to meet the 2012 annual PM<INF>2.5</INF> NAAQS. When the area 
is redesignated to attainment, these requirements are permanently 
discharged.
1. CAA Section 110 General SIP Requirements
    Section 110(a)(2) of title I of the CAA delineates the general 
requirements for a SIP, which include enforceable emissions limitations 
and other control measures, means, or techniques, provisions for the 
establishment and operation of appropriate devices necessary to collect 
data on ambient air quality, and programs to enforce the limitations. 
The general SIP elements and requirements set forth in section 
110(a)(2) of the CAA include, but are not limited to the following: (1) 
Submittal of a SIP that has been adopted by the state after reasonable 
public notice and hearing; (2) provisions for establishment and 
operation of appropriate procedures needed to monitor ambient air 
quality; (3) implementation of a minor source permit program; (4) 
provisions for the implementation of part C requirements (referred to 
as prevention of significant deterioration or PSD); (5) provisions for 
the implementation of part D requirements for nonattainment new source 
review (referred to as part D NNSR, NNSR, nonattainment NSR, or NSR) 
permit programs; (6) provisions for air pollution modeling; and (7) 
provisions for public and local agency participation in planning and 
emission control rule development.
    CAA section 110(a)(2)(D) requires that SIPs contain certain 
measures to prevent sources in a state from significantly contributing 
to air quality problems in another state. However, CAA section 
110(a)(2)(D) requirements for a state are not linked with a particular 
nonattainment area's designation and classification in that state. EPA 
believes that the requirements linked with a particular nonattainment 
area's designation and classifications are the relevant measures to 
evaluate in reviewing a redesignation request. The transport SIP 
submittal requirements, where applicable, continue to apply to a state 
regardless of the designation of any one particular area in the state. 
Thus, EPA does not believe that these requirements are applicable 
requirements for purposes of redesignation.
    In addition, EPA believes that the other CAA section 110(a)(2) 
elements not connected with nonattainment plan submissions and not 
linked with an area's attainment status are not applicable requirements 
for purposes of redesignation because the area will still be subject to 
these requirements after it is redesignated. EPA concludes that the CAA 
section 110(a)(2) and part D requirements, which are linked with a 
particular area's designation and classification, are the relevant 
measures to evaluate in reviewing a redesignation request, and that CAA 
section 110(a)(2) elements not linked to the area's nonattainment 
status are not applicable for purposes of redesignation. This approach 
is consistent with EPA's existing policy on applicability of conformity 
(i.e., for redesignations) and oxygenated fuels requirement. See 
Reading, Pennsylvania, proposed rulemaking and final rule (61 FR 53174, 
October 10, 1996), (62 FR 24826, May 7, 1997); Cleveland-Akron-Lorain, 
Ohio final rule (61 FR 20458, May 7, 1996); and Tampa, Florida, final 
rule (60 FR 62748, December 7, 1995). See also, the discussion on this 
issue in the Cincinnati, Ohio redesignation (65 FR at 37890, June 19, 
2000), and in the Pittsburgh-Beaver Valley, Pennsylvania redesignation 
(66 FR at 53099, October 19, 2001).
    EPA has reviewed the Idaho SIP and has concluded that it meets the 
general SIP requirements under section 110(a)(2) of the CAA to the 
extent they are applicable for the purposes of redesignation. EPA has 
previously approved provisions of Idaho's SIP as demonstrating 
compliance with the CAA section 110(a)(2) requirements for the 2012 
annual PM<INF>2.5</INF> NAAQS (82 FR 57132, December 4, 2017 and 83 FR 
48240, September 24, 2018). However, as noted above, the requirements 
of section 110(a)(2) are statewide requirements that are not linked to 
the PM<INF>2.5</INF> nonattainment status of the West Silver Valley 
area. Therefore, EPA believes that these SIP elements are not 
applicable requirements for purposes of review of this proposed 
redesignation.
    Because PSD requirements will apply after redesignation, areas 
being redesignated must have an approved PSD program. Once the West 
Silver Valley is redesignated to attainment, Idaho's PSD program, and 
not NNSR, will become effective in the area. Idaho's PSD regulations 
are codified in the Idaho Administrative Procedures Act (IDAPA) at 
58.01.01.200-228. We most recently approved revisions to Idaho's PSD 
program on August 20, 2018 (83 FR 42033), May 12, 2017 (82 FR 22083) 
and August 12, 2016 (81 FR 53290).
    Areas seeking redesignation need not comply with the requirement 
that a NNSR program be approved prior to redesignation, provided that 
the area demonstrates maintenance of the NAAQS without NNSR. A more 
detailed rationale for this is described in the Nichols memorandum. 
Nevertheless, on August 20, 2018, EPA approved Idaho's SIP as meeting 
applicable NNSR requirements. (83 FR 42033). EPA has reviewed the Idaho 
SIP and has concluded that it meets the general SIP requirements under 
section 110(a)(2) of the CAA to the extent they are applicable for 
purposes of redesignation, namely a SIP-approved PSD program.
2. Part D of Title I Requirements
    Part D of Title I of the CAA sets forth the basic nonattainment 
plan requirements applicable to all nonattainment areas at subpart 1 
(CAA sections 172-176) and requirements specific to PM<INF>10</INF> and 
PM<INF>2.5</INF> areas at subpart 4 (CAA section 189). On August 24, 
2016, EPA promulgated the Fine Particulate Matter National Ambient Air 
Quality Standards; State Implementation Plan Requirements

[[Page 51321]]

rule.\3\ This rule implements the requirements of part D of title I of 
the CAA for areas designated nonattainment for any PM<INF>2.5</INF> 
NAAQS.
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    \3\ 81 FR 58010, August 24, 2016. Codified at 40 CFR part 51, 
subpart Z.
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    EPA's longstanding interpretation of the nonattainment planning 
requirements of CAA section 172 is that once an area is attaining the 
NAAQS, those requirements are not ``applicable'' for purposes of CAA 
section 107(d)(3)(E)(ii) and therefore need not be approved into the 
SIP before EPA can redesignate the area. In the 1992 General Preamble 
for Implementation of CAA title I, EPA set forth its interpretation of 
applicable requirements for purposes of evaluating redesignation 
requests when an area is attaining a standard. See 57 FR 13498, 13564 
(April 16, 1992). EPA noted that the requirements for RFP and other 
measures designed to provide for attainment do not apply in evaluating 
redesignation requests because those nonattainment planning 
requirements ``have no meaning'' for an area that has already attained 
the standard. Id. This interpretation was also set forth in the 
Calcagni memorandum. EPA's understanding of CAA section 172 also forms 
the basis of its Clean Data Policy, which was articulated with regard 
to PM<INF>2.5</INF> in 40 CFR 51.1015 and suspends a state's obligation 
to submit most of the attainment planning requirements that would 
otherwise apply, including an attainment demonstration and planning 
SIPs to provide for RFP, RACM, and contingency measures under section 
172(c)(9).\4\ Courts have upheld EPA's interpretation of CAA section 
172(c)(1)'s ``reasonably available'' control measures and control 
technology as meaning only those controls that advance attainment, 
which precludes the need to require additional measures where an area 
is already attaining. NRDC v. EPA, 571 F.3d 1245, 1252 (D.C. Cir. 
2009); Sierra Club v. EPA, 294 F.3d 155, 162 (D.C. Cir. 2002); Sierra 
Club v. EPA, 314 F.3d 735, 744 (5th Cir. 2002).
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    \4\ This regulation was promulgated as part of the 1997 
PM<INF>2.5</INF> NAAQS implementation rule that was subsequently 
challenged and remanded in NRDC v. EPA, 706 F.3d 428 (D.C. Cir. 
2013), as discussed in section III.B of this document. However, the 
Clean Data Policy portion of the implementation rule was not at 
issue in that case.
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    As stated previously, EPA determined that the West Silver Valley 
has attained the 2012 annual PM<INF>2.5</INF> NAAQS in a ``clean data 
determination.'' 83 FR 65535, December 21, 2018. Furthermore, as shown 
in section III.A of this document, the West Silver Valley continues to 
attain the 2012 annual PM<INF>2.5</INF> NAAQS. Therefore, because 
attainment has been reached in the West Silver Valley, no additional 
measures are needed to provide for attainment, and CAA section 
172(c)(1) requirements for an attainment demonstration and RACM are no 
longer considered to be applicable for purposes of redesignation as 
long as the West Silver Valley continues to attain the standard until 
redesignation.
    The CAA section 172(c)(2) requirement that nonattainment plans 
contain provisions promoting reasonable further progress toward 
attainment is also not relevant for purposes of redesignation because 
EPA has determined that the West Silver Valley has monitored attainment 
of the 2012 annual PM<INF>2.5</INF> NAAQS. In addition, because the 
West Silver Valley has attained the 2012 annual PM<INF>2.5</INF> NAAQS 
and is no longer subject to RFP requirements, the requirement to submit 
the section 172(c)(9) contingency measures is not applicable for 
purposes of redesignation. CAA section 172(c)(6) requires the SIP to 
contain control measures necessary to provide for attainment of the 
NAAQS. Because attainment has been reached, no additional measures are 
needed to provide for attainment.
    Section 172(c)(3) of the CAA requires submission and approval of a 
comprehensive, accurate and current inventory of actual emissions. The 
requirement under CAA section 172(c)(3) was not suspended by EPA's 
clean data determination for the 2012 annual PM<INF>2.5</INF> NAAQS and 
is the only remaining requirement under CAA section 172 to be 
considered for purposes of redesignation of the West Silver Valley. On 
September 29, 2017, Idaho submitted to EPA a 2013 base year emissions 
inventory for the West Silver Valley for the 2012 annual 
PM<INF>2.5</INF> NAAQS. The 2013 base year inventory covers the general 
source categories of point sources, nonroad mobile sources, area 
sources, and onroad mobile sources and includes PM<INF>2.5</INF> 
emissions and precursors, NO<INF>X</INF>, sulfur dioxide 
(SO<INF>2</INF>), VOCs, and ammonia (NH<INF>3</INF>). EPA approved the 
2013 base year inventory on September 11, 2018 (83 FR 45830).
    CAA section 172(c)(4) requires the identification and 
quantification of allowable emissions for major new and modified 
sources in an area, and section 172(c)(5) requires source permits for 
the construction and operation of new and modified major stationary 
sources anywhere in the nonattainment area. As stated previously in 
this document, EPA has determined that, since PSD requirements will 
apply after redesignation, areas being redesignated need not comply 
with the requirement that a NNSR program be approved prior to 
redesignation, provided that the area demonstrates maintenance of the 
NAAQS without NNSR. A more detailed rationale for this view is 
described in the Nichols memorandum. Nevertheless, EPA first approved 
the requirements of the part D NSR permit program for Idaho under 
subpart 1 on November 26, 2010 (75 FR 72719). Subsequently, on March 
20, 2018, Idaho submitted rule revisions to meet additional part D NSR 
requirements promulgated by EPA under subpart 4 (81 FR 58010, August 
24, 2016). We approved Idaho's submission on August 20, 2018 (83 FR 
42033).
    Once the West Silver Valley is redesignated to attainment, Idaho's 
PSD program, and not NNSR, will become effective in the area. Idaho's 
PSD regulations are codified in the Idaho Administrative Procedures Act 
(IDAPA) at 58.01.01.200-228 (permit to construct) and governed by IDAPA 
58.01.01.205 (permit requirements for new major facilities or major 
modifications in attainment or unclassifiable areas). We most recently 
approved revisions to Idaho's PSD program on August 20, 2018 (83 FR 
42033), May 12, 2017 (82 FR 22083) and August 12, 2016 (81 FR 53290). 
EPA finds that Idaho's PSD provisions meet all applicable Federal 
requirements for any area designated unclassifiable or attainment.
    CAA section 172(c)(7) requires the SIP to meet the applicable 
provisions of CAA section 110(a)(2). As noted above, we find that the 
Idaho SIP meets the CAA section 110(a)(2) applicable requirements for 
purposes of redesignation.
    Section 175A of the CAA requires a state seeking redesignation to 
attainment to submit a SIP revision to provide for the maintenance of 
the NAAQS in the area ``for at least 10 years after the 
redesignation.'' In conjunction with its requests to redesignate the 
West Silver Valley to attainment, Idaho submitted a plan to provide for 
maintenance of the 2012 annual PM<INF>2.5</INF> NAAQS in the West 
Silver Valley for at least 10 years after redesignation, through 2031. 
Idaho is requesting that EPA approve the submission as meeting the 
requirement of section 175A of the CAA. Once approved, the maintenance 
plan will ensure that the Idaho SIP meets the requirements of the CAA 
regarding maintenance of the 2012 annual PM<INF>2.5</INF> NAAQS for the 
West Silver Valley. EPA's analysis of the maintenance plan is provided 
in section III.D of this document.
    EPA concludes that Idaho has met the requirements of subpart 1 of 
part D relevant for redesignation. Specifically,

[[Page 51322]]

pursuant to section 110(k) of the CAA, EPA has approved Idaho's 2013 
base year inventory for the West Silver Valley into the Idaho SIP.

C. Improvement in Air Quality Due to Permanent and Enforceable Measures

    CAA section 107(d)(3)(E)(iii) of the CAA provides that for an area 
to be redesignated to attainment, the Administrator must determine that 
the improvement in air quality is due to permanent and enforceable 
reductions in emissions resulting from implementation of the applicable 
implementation plan, implementation of applicable Federal air pollutant 
control regulations, and other permanent and enforceable reductions.
    In making this demonstration for the West Silver Valley, Idaho 
explained that control measures for the area focused on residential 
wood combustion, onroad, and nonroad sources, which contributed to 
PM<INF>2.5</INF> formation in the 2013 base year emissions inventory 
(2013 was one of the years used to designate the area as 
nonattainment). The 2017 attainment year emissions inventory recorded 
reductions in directly emitted PM<INF>2.5</INF> and precursors for 
those categories (2017 is one of the years used to monitor attainment). 
Idaho states that the emissions reductions occurred because of 
permanent and enforceable federal reduction programs, public outreach, 
and financial incentives.
Residential Wood Heating
    Idaho's residential wood combustion control measures for the West 
Silver Valley addressed smoke from heating devices, such as fireplaces 
and wood stoves. In comparing emissions between the 2013 base year 
inventory and the 2017 attainment year inventory for the West Silver 
Valley, Idaho showed a 63 percent decrease in PM<INF>2.5</INF> 
emissions from residential wood combustion, from 55.38 tons per year 
(tpy) in the 2013 base year emissions inventory to 20.45 tpy in the 
2017 attainment year emissions inventory. Idaho attributed these 
emission reductions primarily to Federal standards for wood heaters and 
to the West Silver Valley woodstove changeout program.
    Idaho explained that EPA's 2015 Standards of Performance for New 
Residential Wood Heaters strengthened emissions limits for residential 
wood heaters, making devices significantly cleaner.\5\ The 2015 rule 
requires, among other things, that new residential wood heaters be 
certified to meet the 2015 emission limits before they may be imported, 
sold, or distributed in the U.S. To accelerate the removal of 
uncertified wood stoves, Idaho incentivized wood stove replacements in 
the West Silver Valley through a wood stove changeout program. 
Participants in the changeout program replaced uncertified wood stoves 
with EPA-certified devices or gas appliances, and were required to 
surrender their uncertified wood stoves, making the emissions 
reductions permanent. Between 2013 and 2017, Idaho replaced 65 wood 
stoves in the West Silver Valley. Although Idaho's future year 
emissions projections assume residential wood combustion to be constant 
for years beyond 2017, Idaho anticipates additional emissions 
reductions as phase II of the Standards of Performance for New 
Residential Wood Heaters is implemented and as remaining funding for an 
additional 140 wood stove replacements in the West Silver Valley is 
distributed.
---------------------------------------------------------------------------

    \5\ EPA promulgated standards for residential wood heaters on 
February 26, 1988 (53 FR 5860). On March 16, 2015, EPA revised the 
rule (80 FR 13672). EPA recently revised the rule on April 2, 2020 
(85 FR 18448).
---------------------------------------------------------------------------

Mobile Sources
    Idaho states that despite increasing vehicle populations and 
vehicle miles traveled, emissions from mobile sources in the West 
Silver Valley have decreased as a result of Federal motor vehicle 
regulations. In comparing the 2013 base year emissions inventory with 
the 2017 attainment year emissions, EPA found that onroad emissions 
decreased by 2.55 tpy and nonroad emissions decreased by 3.65 tpy.\6\
---------------------------------------------------------------------------

    \6\ The 2013 base year EI onroad emissions were 17.30 tpy and 
nonroad emissions were 14.7 tpy (see 83 FR 21976, May 11, 2018).
---------------------------------------------------------------------------

    Idaho primarily attributes the reduction in onroad emissions to the 
Federal Tier 2 (65 FR 6698, February 10, 2000) and Tier 3 (79 FR 23414, 
April 28, 2014) vehicle emissions standards and gasoline sulfur control 
requirements, and to the Federal rule for heavy-duty engine and vehicle 
standards and highway diesel fuel sulfur control requirements (66 FR 
5002, January 18, 2001). Idaho explained that the vehicle standards 
reduce tailpipe and evaporative emissions, reductions which increase as 
vehicle turnover increases over time, and that the gasoline sulfur 
standards make emissions control systems more effective for both 
existing and new vehicles.
    Idaho identified several Federal rules that have been promulgated 
to address nonroad mobile emissions sources. On June 29, 2004, EPA 
adopted a comprehensive national program to reduce emissions from 
nonroad diesel engines (69 FR 38958). The rule phased in tighter 
emissions limits for large nonroad diesel engines and requirements for 
reducing the sulfur content of nonroad diesel fuel.
Statewide SIP-Approved Rules
    Idaho has several SIP-approved rules that apply statewide and 
complement the Federal control strategies in the West Silver Valley. 
For example, the following rules assist in the control of 
PM<INF>2.5</INF> in the West Silver Valley: The rules for the control 
of open burning at IDAPA 58.01.01.600 through 624; the requirements to 
reasonably control fugitive dust at sections 650 through 652; the 
permitting of industrial sources (sections 200, 300 and 400), and the 
specific requirements for nonmetallic mineral processing plants at 
sections 795 through 799. Additionally, sections 550 through 562 
provide authority to limit emissions during degraded air quality 
episodes.
    Idaho also assessed the potential role that changing meteorological 
conditions might have played in improving air quality in the West 
Silver Valley. Idaho reviewed temperature and precipitation data as 
well as the frequency of wintertime stagnation events. Idaho concluded 
that it is unlikely that favorable meteorological conditions played a 
significant role in attaining the 2012 annual PM<INF>2.5</INF> NAAQS.
    Based on the evaluation of these control measures, EPA proposes to 
determine that the improvement in air quality is reasonably 
attributable to permanent and enforceable reductions in emissions 
resulting from implementation of the applicable Federal air pollutant 
control regulations, and other permanent and enforceable emissions 
reductions.

D. Fully Approved Maintenance Plan

    In conjunction with Idaho's request to redesignate the West Silver 
Valley to attainment, Idaho submitted SIP revisions to provide for 
maintenance of the 2012 annual PM<INF>2.5</INF> NAAQS through 2031. EPA 
is proposing to approve Idaho's maintenance plan for the West Silver 
Valley. If this proposed action is finalized, the West Silver Valley 
will have an approved maintenance plan.
    CAA section 107(d)(3)(E)(iv) requires that, for a nonattainment 
area to be redesignated to attainment, EPA must fully approve a 
maintenance plan which meets the requirements of CAA section 175A. The 
plan must demonstrate continued attainment of the relevant NAAQS in the 
area for at least 10 years after our approval of the redesignation. 
Eight years after our approval of a redesignation, the State must 
submit a

[[Page 51323]]

revised maintenance plan demonstrating attainment for the 10 years 
following the initial 10-year period. The maintenance plan must also 
contain a contingency plan to ensure prompt correction of any violation 
of the NAAQS. The Calcagni Memo provides additional guidance on the 
content of a maintenance plan, stating that a maintenance plan should 
include the following elements: (1) An attainment emissions inventory; 
(2) a maintenance demonstration showing attainment for 10 years 
following redesignation; (3) a commitment to maintain the existing 
monitoring network; (4) verification of continued attainment; and (5) a 
contingency plan to prevent or correct future violations of the NAAQS. 
The following paragraphs describe how each of these elements is 
addressed in Idaho's maintenance plan.
1. Attainment Inventory
    As discussed in the CAA General Preamble (see 57 FR 13498, April 
16, 1992) and the Calcagni Memo, PM<INF>2.5</INF> maintenance plans 
should include an attainment emission inventory to identify the level 
of emissions in the area which is sufficient to maintain the NAAQS. The 
attainment inventory should be consistent with EPA's most recent 
guidance on emission inventories for nonattainment areas available at 
the time and should include the emissions during the time period 
associated with the monitoring data showing attainment.
    Idaho submitted a maintenance plan for the West Silver Valley that 
includes an attainment year inventory for the area for 2017, which is 
one of the years in the period during which the West Silver Valley 
first monitored attainment of the 2012 annual PM<INF>2.5</INF> NAAQS 
(see section III.A of this document). The attainment year inventory 
includes emissions of PM<INF>2.5</INF>, NO<INF>X</INF>, SO<INF>2</INF>, 
VOC, and NH<INF>3</INF>. The 2017 attainment levels of emissions are 
summarized in Table 3, along with future year projected emissions for 
2026 and 2031.

                       Table 3--West Silver Valley Maintenance Plan Emissions Inventories
                                               [In tons per year]
----------------------------------------------------------------------------------------------------------------
                                   2017                            2031        Difference from   Difference from
       Source category          attainment     2026 interim     maintenance     2026 and 2017     2031 and 2017
----------------------------------------------------------------------------------------------------------------
                                         PM (condensable and filterable)
----------------------------------------------------------------------------------------------------------------
Point.......................           0.642           0.742           0.742              0.10              0.10
Area........................         259.710         259.070         258.720             -0.64             -0.99
Onroad......................          14.700           8.760           9.250             -5.94             -5.45
Nonroad.....................           3.590           1.780           1.590             -1.81             -2.00
                             -----------------------------------------------------------------------------------
    Total...................         278.642         270.352         270.302             -8.29             -8.34
----------------------------------------------------------------------------------------------------------------
                                                       NO
----------------------------------------------------------------------------------------------------------------
Point.......................           1.610           6.430           9.200              4.82              7.59
Area........................          51.130          51.500          51.700              0.37              0.57
Onroad......................         484.160         324.140         338.400           -160.02           -145.76
Nonroad.....................          62.080          29.910          27.260            -32.17            -34.82
                             -----------------------------------------------------------------------------------
    Total...................         598.980         411.980         426.560           -187.00           -172.42
----------------------------------------------------------------------------------------------------------------
                                                       SO
----------------------------------------------------------------------------------------------------------------
Point.......................           0.080           0.110           0.130              0.03              0.05
Area........................          16.170          16.350          16.450              0.18              0.28
Onroad......................           0.700           0.760           0.900              0.06              0.20
Nonroad.....................           0.100           0.080           0.090             -0.02             -0.01
                             -----------------------------------------------------------------------------------
    Total...................          17.050          17.300          17.570              0.25              0.52
----------------------------------------------------------------------------------------------------------------
                                                       VOC
----------------------------------------------------------------------------------------------------------------
Point.......................           5.710          13.820          13.980              8.11              8.27
Area........................       3,307.970       3,350.320       3,373.840             42.35             65.87
Onroad......................         134.200          83.670          73.450            -50.53            -60.75
Nonroad.....................          32.050          28.080          28.200             -3.97             -3.85
                             -----------------------------------------------------------------------------------
    Total...................       3,479.930       3,475.890       3,489.470             -4.04              9.54
----------------------------------------------------------------------------------------------------------------
                                                       NH
----------------------------------------------------------------------------------------------------------------
Point.......................           0.020           0.160           0.250              0.14              0.23
Area........................          35.200          35.090          35.030             -0.11             -0.17
Onroad......................           4.430           4.490           5.300              0.06              0.87
Nonroad.....................           0.110           0.110           0.110              0.00              0.00
                             -----------------------------------------------------------------------------------
    Total...................          39.760          39.850          40.690              0.09              0.93
----------------------------------------------------------------------------------------------------------------


[[Page 51324]]

    Based our review of the emissions inventories Idaho provided in its 
submission, we propose to find that Idaho prepared an adequate 
attainment inventory for the West Silver Valley area.\7\
---------------------------------------------------------------------------

    \7\ ``Emissions Inventory Guidance for Implementation of Ozone 
and Particulate Matter National Ambient Air Quality Standards 
(NAAQS) and Regional Haze Regulations,'' May 2017.
---------------------------------------------------------------------------

2. Maintenance Demonstration
    CAA section 175A requires a state seeking redesignation to 
attainment to submit a SIP revision to provide for the maintenance of 
the NAAQS in the area ``for at least 10 years after the 
redesignation.'' A state can make this demonstration by either showing 
that future emissions of a pollutant or its precursors will not exceed 
the level of the attainment inventory, or by modeling to show that the 
future mix of sources and emissions rates will not cause a violation of 
the NAAQS.\8\ In its maintenance plan, Idaho demonstrates maintenance 
by showing that emissions projected over the maintenance period will 
not exceed emissions levels that were present when the area came into 
attainment of the 2012 annual PM<INF>2.5</INF> NAAQS. In its 
maintenance demonstration for the West Silver Valley, Idaho projected 
emissions forward to 2026 and 2031, which satisfies the 10-year 
interval required in section 175A of the CAA. As discussed previously, 
Idaho selected 2017 as the attainment emissions inventory year for the 
West Silver Valley. The attainment inventory identifies the level of 
emissions that is sufficient to attain the 2012 annual PM<INF>2.5</INF> 
NAAQS. Idaho has previously submitted a 2013 base year inventory, which 
EPA approved into the Idaho SIP on September 11, 2018 (83 FR 45830).
---------------------------------------------------------------------------

    \8\ See Calcagni Memo, pages 9-10.
---------------------------------------------------------------------------

    The emissions inventories in the West Silver Valley maintenance 
plan address four major source categories: Point, area, onroad mobile 
and nonroad mobile. Idaho estimated future year emissions inventories 
using the latest socioeconomic growth indicators and applying emissions 
reduction benefits from adopted control strategies when appropriate.
    Idaho identified five minor point sources in the West Silver Valley 
and projected emissions to future years by using either their potential 
to emit as a conservative estimate of growth, the average annual growth 
of population, or assumed little or no expected growth based on data 
evidence or conversations with facility owners. Area sources in the 
West Silver Valley emissions inventory include residential wood 
combustion, solvent use, agricultural production, fuel transport, 
combustion (residential, commercial, and industrial), unpaved road 
dust, industrial processes, outdoor burning, prescribed fire, and waste 
disposal, treatment and recovery processes. Idaho estimated future year 
emissions based on the average annual growth rate of the appropriate 
activity sector in the previous 5 years through to the final year of 
the maintenance plan, 2031. Idaho developed the mobile source inventory 
for Shoshone County using the latest version of EPA's Motor Vehicle 
Emissions Simulator (MOVES) model at the time,\9\ MOVES2014b, and 
apportioned it to the West Silver Valley nonattainment area. Idaho used 
local inputs and applied growth rates to the 2017 vehicle miles 
travelled and vehicle populations to develop inputs for the 2026 and 
2031 projections. Idaho calculated paved road dust emissions according 
to AP-42 guidance for Shoshone County and apportioned the emissions 
estimates to the West Silver Valley area. To estimate nonroad mobile 
source emissions, Idaho used the nonroad component of the MOVES model 
and used the model defaults, except for meteorological data.
---------------------------------------------------------------------------

    \9\ MOVES 2014b was the latest model version when Idaho 
submitted the West Silver Valley redesignation request and 
maintenance plan to EPA on June 2, 2020. Since that time, EPA 
published model version MOVES3 on January 7, 2021, making it the 
latest version of the MOVES model as of this publication. 86 FR 
1106. As explained in the notice of availability for MOVES3, state 
and local agencies should use the latest version of MOVES that is 
available at the time that a SIP is developed. However, state and 
local agencies that have already completed significant work on a SIP 
with a version of MOVES2014 may continue to rely on the earlier 
version of MOVES. Because Idaho submitted the SIP to EPA before 
MOVES3 was released, it was appropriate for Idaho to have used 
MOVES2014b.
---------------------------------------------------------------------------

    EPA has reviewed the documentation provided by Idaho for developing 
the 2026 and 2031 emissions inventories for the West Silver Valley and 
finds that Idaho prepared them in accordance with EPA requirements. 
These inventories indicate a decrease in emissions of PM<INF>2.5</INF> 
(38.34 tpy or 3%) and NO<INF>X</INF> (172.42 tpy or 28.79%) throughout 
the maintenance period, between 2017 and 2031. Although there are 
slight increases in emissions of SO<INF>2</INF> (0.52 tpy or 3.05%), 
VOC (9.54 tpy or 0.28%) and NH<INF>3</INF> (0.93 tpy or 2.34%) between 
2017 and 2031, which Idaho attributes to population growth, Idaho 
demonstrated that this increase will not prevent maintenance of the 
NAAQS through 2031.
3. Monitoring Network
    In the maintenance plan, Idaho committed to continue to operate the 
air monitoring network in accordance with 40 CFR part 58. Idaho stated 
that it will work with EPA each year through the air monitoring network 
review process to determine the adequacy of the monitoring network, if 
additional monitoring is needed, and if or when the site can be 
discontinued or relocated.\10\ EPA proposes to determine that the 
maintenance plan contains adequate provisions for continued operation 
of an air quality monitoring network to verify maintenance of the 2012 
annual PM<INF>2.5</INF> NAAQS.
---------------------------------------------------------------------------

    \10\ See EPA's November 9, 2020 approval of Idaho's 2020 Annual 
Monitoring Network Plan, included in the docket for this action.
---------------------------------------------------------------------------

4. Verification of Continued Attainment
    Idaho remains obligated to continue to quality-assure monitoring 
data and enter all data into AQS in accordance with Federal guidelines. 
Idaho will use air monitoring results to verify continued attainment of 
the 2012 annual PM<INF>2.5</INF> NAAQS and to track progress of the 
maintenance plan. Idaho is also required to periodically update the 
emissions inventory for Shoshone County in accordance with the Annual 
Air Emissions Reporting Requirements Rule (AERR). This includes 
developing annual inventories for major point sources and a 
comprehensive periodic inventory covering all source categories every 3 
years.
5. Contingency Plan
    CAA section 175A(d) requires that a maintenance plan also include 
contingency provisions, as necessary, to promptly correct any violation 
of the NAAQS that occurs after redesignation of the area to attainment. 
For the purposes of CAA section 175A, a state is not required to have 
fully adopted contingency measures that will take effect without 
further action by the state in order for the maintenance plan to be 
approved. However, the contingency plan is an enforceable part of the 
SIP and should ensure that contingency measures are adopted promptly 
once they are triggered. The maintenance plan should discuss the 
measures to be adopted and a schedule and procedure for adoption and 
implementation. The contingency plan must require that the state will 
implement all measures contained in the Part D nonattainment plan for 
the area prior to redesignation. The state should also identify the 
specific indicators, or triggers, which will be used to determine when 
the contingency plan will be implemented.
    The West Silver Valley maintenance plan identifies actions Idaho 
will promptly take to prevent or correct a violation of the 2012 annual 
PM<INF>2.5</INF>

[[Page 51325]]

NAAQS. If the annual average PM<INF>2.5</INF> concentration reaches 
12.5 ug/m\3\ or greater in a single calendar year, Idaho will evaluate 
all appropriate data to determine the cause of the elevated levels and 
whether the elevated PM<INF>2.5</INF> levels are likely to continue. 
Idaho will evaluate all appropriate data including air quality data, 
meteorology, evaluation of wood smoke programs and information on 
wildfires or winter power outages to determine the cause of the 
exceedance within 6 months of the year in which the annual average 
reaches 12.5 ug/m\3\ or greater. If the evaluation indicates that 
additional control measures are necessary, Idaho will implement 
appropriate contingency measures as expeditiously as possible, no later 
than 18 months from the determination of a single year exceedance based 
on quality-assured data. If Idaho determines that an exceptional event 
contributes to a violation of the 2012 annual PM<INF>2.5</INF> 
standard, it will follow EPA's exceptional events rule.\11\
---------------------------------------------------------------------------

    \11\ Treatment of Data Influenced by Exceptional Events, October 
3, 2016, 81 FR 68216.
---------------------------------------------------------------------------

    Idaho has identified the following potential contingency measures 
for the West Silver Valley maintenance plan:
    <bullet> Increase efforts to control mud and dirt track out from 
industrial, construction, and agricultural operations onto paved roads.
    <bullet> Adopt local ordinance addressing nonresidential slash 
burning to require burn permits year-round.
    <bullet> Adopt local ordinances that reduce the residential open 
burning days.
    <bullet> Adopt a local ordinance that prohibits installing 
uncertified wood stoves in residential and commercial buildings.
    <bullet> Expand educational efforts to reduce PM<INF>2.5</INF> from 
wood smoke.
    <bullet> Pursue funds to continue offering wood stove changeouts 
and fireplace conversions within the West Silver Valley nonattainment 
area.
    Based on our analysis of Idaho's submittal, we propose to find that 
the contingency measure provisions provided in the West Silver Valley 
maintenance plan are sufficient and meet the requirements of CAA 
section 175A(d).

E. Requirements for Transportation Conformity and Motor Vehicle 
Emissions Budgets (MVEBs)

    Transportation conformity is required by CAA section 176(c). EPA's 
transportation conformity rule at 40 CFR part 93, subpart A, requires 
that transportation plans, programs, and projects conform to SIPs and 
establishes the criteria and procedures for determining whether or not 
they conform to the SIP. Conforming to a SIP means that onroad 
transportation activities will not produce new air quality violations, 
worsen existing violations, or delay timely attainment of the NAAQS. 
Thus, EPA's transportation conformity rule requires a demonstration 
that emissions from a metropolitan planning organization's regional 
transportation plan and transportation improvement program, involving 
Federal Highway Administration (FHWA) or Federal Transit Administration 
(FTA) funding or approval, are consistent with the motor vehicle 
emissions budgets (MVEBs) contained in a control strategy SIP revision 
or maintenance plan (40 CFR 93.101, 93.118, and 93.124). The MVEB is 
the level of mobile source emissions of a pollutant relied upon in the 
attainment or maintenance demonstration to attain or maintain 
compliance with the NAAQS in the nonattainment or maintenance area. A 
PM<INF>2.5</INF> maintenance plan should identify MVEBs for direct 
PM<INF>2.5</INF>, NO<INF>X</INF> and all other PM<INF>2.5</INF> 
precursors from onroad mobile source emissions that are determined to 
significantly contribute to PM<INF>2.5</INF> levels in the area.\12\
---------------------------------------------------------------------------

    \12\ See 40 CFR 93.102(b)(2)(iv) and (v), and (b)(3).
---------------------------------------------------------------------------

    Idaho indicated that the West Silver Valley nonattainment area 
meets the definition of an ``isolated rural nonattainment area'' at 40 
CFR 93.109(g) because the area does not contain, and is not part of, a 
metropolitan planning organization. Neither a transportation 
improvement plan nor a regional transportation plan was developed for 
the West Silver Valley. Instead, transportation projects for the West 
Silver Valley are included in a statewide transportation improvement 
plan. The Idaho Transportation Department is responsible for 
transportation conformity determinations in this isolated rural 
nonattainment area.
    The maintenance plan submitted by Idaho for the West Silver Valley 
identifies MVEBs for PM<INF>2.5</INF>, NO<INF>X</INF> and VOCs, which 
are displayed in Table 4. To determine which precursor pollutants were 
required to be included in the MVEB, Idaho reviewed PM<INF>2.5</INF> 
speciation at the Pinehurst monitor (AQS ID 160790017). Idaho did not 
include emissions from paved road dust because those emissions were 
found to be insignificant. Idaho also found that vehicle emissions of 
SO<INF>2</INF> and NH<INF>3</INF> contributed minimally to 
PM<INF>2.5</INF> in the area and did not include MVEBs for these 
precursors in accordance with 40 CFR 93.102(b)(2)(v).

         Table 4--2017 and 2031 MVEBs for the West Silver Valley
------------------------------------------------------------------------
                                    Motor vehicle emissions budget (tpy)
               Year               --------------------------------------
                                      PM2.5         NOX          VOC
------------------------------------------------------------------------
2017.............................        10.84       484.16       134.20
2031.............................         3.76       338.14        73.45
------------------------------------------------------------------------

    EPA is proposing to find that Idaho has evaluated the appropriate 
pollutants and precursors and appropriately established MVEBs for 
PM<INF>2.5</INF>, NO<INF>X</INF> and VOCs. Idaho used the most up-to-
date model (MOVES2014b) available at the time of submission in order to 
appropriately calculate these budgets. The MVEBs are based on the 
control measures in the maintenance plan and consistent with 
maintaining the 2012 annual PM<INF>2.5</INF> NAAQS.

IV. Proposed Action

    EPA is proposing to redesignate the West Silver Valley 2012 annual 
PM<INF>2.5</INF> nonattainment area, and to approve the associated 
maintenance plan for the area. If this proposal is finalized, the 
designation status of the West Silver Valley under 40 CFR part 81 will 
be revised to attainment upon the effective date of the final action.

V. Statutory and Executive Order Reviews

    Under the CAA, redesignation of an area to attainment and the 
accompanying approval of a maintenance plan under section

[[Page 51326]]

107(d)(3)(E) are actions that affect the status of a geographical area 
and do not impose any additional regulatory requirements on sources 
beyond those imposed by state law. A redesignation to attainment does 
not in and of itself create any new requirements, but rather results in 
the applicability of requirements contained in the CAA for areas that 
have been redesignated to attainment. Moreover, the Administrator is 
required to approve a SIP submission that complies with the provisions 
of the CAA and applicable Federal regulations. 42 U.S.C. 7410(k); 40 
CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to 
approve state choices, provided that they meet the criteria of the CAA. 
Accordingly, this action merely approves state law as meeting Federal 
requirements and does not impose additional requirements beyond those 
already imposed by state law. For that reason, this action:
    <bullet> 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);
    <bullet> Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
    <bullet> 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.);
    <bullet> 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);
    <bullet> Does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
    <bullet> Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
    <bullet> Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
    <bullet> 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 CAA; and
    <bullet> Does not provide EPA with the discretionary authority to 
address, as appropriate, disproportionate human health or environmental 
effects, using practicable and legally permissible methods, under 
Executive Order 12898 (59 FR 7629, February 16, 1994).
    In addition, this proposed action does not apply on any Indian 
reservation land or in any other area where EPA or an Indian tribe has 
demonstrated that a tribe has jurisdiction. In those areas of Indian 
country, this rulemaking does not have tribal implications as specified 
by Executive Order 13175 (65 FR 67249, November 9, 2000), because 
redesignation is an action that affects the status of a geographical 
area and does not impose any new regulatory requirements on tribes, 
impact any existing sources of air pollution on tribal lands, nor 
impair the maintenance of ozone national ambient air quality standards 
in tribal lands.

List of Subjects

40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Lead, Nitrogen dioxide, Ozone, 
Particulate matter, Reporting and recordkeeping requirements, Sulfur 
oxides, Volatile organic compounds.

40 CFR Part 81

    Environmental protection, Air pollution control, National parks, 
Wilderness areas.

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

    Dated: September 8, 2021.
Michelle L. Pirzadeh,
Acting Regional Administrator, Region 10.
[FR Doc. 2021-19801 Filed 9-14-21; 8:45 am]
BILLING CODE 6560-50-P


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