Document ID: EPA-R08-OAR-2012-0351-0001
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Wyoming; Interstate Transport of Pollution for the 2006 24-Hour PM2.5 NAAQS
Posted Date: 2015-05-18T04:00Z

[Federal Register Volume 80, Number 95 (Monday, May 18, 2015)]
[Proposed Rules]
[Pages 28209-28215]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-11782]

=======================================================================
-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2012-0351; FRL-9927-81-Region 8]

Approval and Promulgation of State Implementation Plans; State of 
Wyoming; Interstate Transport of Pollution for the 2006 24-Hour PM2.5 
NAAQS

AGENCY: Environmental Protection Agency.

ACTION: Proposed rule.

-----------------------------------------------------------------------

[[Page 28210]]

SUMMARY: The EPA is proposing to approve portions of an August 19, 2011 
State Implementation Plan (SIP) submission from the State of Wyoming 
that are intended to demonstrate that its SIP meets certain interstate 
transport requirements of the Clean Air Act (Act or CAA) for the 2006 
24-hour fine particulate matter (PM2.5) National Ambient Air 
Quality Standards (NAAQS). This submission addresses the requirement 
that Wyoming's SIP contain adequate provisions prohibiting air 
emissions that will have certain adverse air quality effects in other 
states. Specifically, EPA is proposing to approve the portion of the 
Wyoming SIP submission that addresses the significant contribution to 
nonattainment and interference with maintenance transport requirements 
for the 2006 24-hour PM2.5 NAAQS. EPA is also proposing to 
approve the interference with prevention of significant deterioration 
(PSD) of air quality transport requirement for this NAAQS, and is not 
proposing action on the interference with visibility transport 
requirement at this time. EPA will address the visibility requirement 
for this NAAQS in a separate future action.

DATES: Comments must be received on or before June 17, 2015.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2012-0351, by one of the following methods:
     http://www.regulations.gov. Follow the on-line 
instructions for submitting comments.
     Email: clark.adam@epa.gov.
     Fax: (303) 312-6064 (please alert the individual listed in 
the FOR FURTHER INFORMATION CONTACT if you are faxing comments).
     Mail: Director, Air Program, Environmental Protection 
Agency (EPA), Region 8, Mail Code 8P-AR, 1595 Wynkoop Street, Denver, 
Colorado 80202-1129.
     Hand Delivery: Director, Air Program, Environmental 
Protection Agency (EPA), Region 8, Mail Code 8P-AR, 1595 Wynkoop 
Street, Denver, Colorado 80202-1129. Such deliveries are only accepted 
Monday through Friday, 8:00 a.m. to 4:30 p.m., excluding federal 
holidays. Special arrangements should be made for deliveries of boxed 
information.
    Instructions: Direct your comments to Docket ID No. EPA-R08-OAR-
2012-0351. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
http://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through http://www.regulations.gov or email. The http://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an email comment directly to EPA, without 
going through http://www.regulations.gov, your email address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses. For additional instructions on submitting 
comments, go to Section I, General Information of the SUPPLEMENTARY 
INFORMATION section of this document.
    Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly-available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the Air Program, 
Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 
Wynkoop, Denver, Colorado 80202-1129. EPA requests that if at all 
possible, you contact the individual listed in the FOR FURTHER 
INFORMATION CONTACT section to view the hard copy of the docket. You 
may view the hard copy of the docket Monday through Friday, 8:00 a.m. 
to 4:00 p.m., excluding federal holidays.

FOR FURTHER INFORMATION CONTACT: Adam Clark, Air Program, U.S. 
Environmental Protection Agency, Region 8, Mailcode 8P-AR, 1595 
Wynkoop, Denver, Colorado 80202-1129, (303) 312-7104, 
clark.adam@epa.gov.

SUPPLEMENTARY INFORMATION:

Definitions

    For the purpose of this document, we are giving meaning to certain 
words or initials as follows:
    (i) The words or initials Act or CAA mean or refer to the Clean Air 
Act, unless the context indicates otherwise.
    (ii) The initials CAIR mean or refer to the Clean Air Interstate 
Rule.
    (iii) The initials CSAPR mean or refer to the Cross-State Air 
Pollution Rule.
    (iv) The words EPA, we, us or our mean or refer to the United 
States Environmental Protection Agency.
    (v) The initials NAAQS mean or refer to the National Ambient Air 
Quality Standards.
    (vi) The initials NSR mean or refer to New Source Review.
    (vii) The initials PM2.5 mean or refer to fine particulate matter.
    (viii) The initials PSD mean or refer to Prevention of Significant 
Deterioration.
    (ix) The initials SIP mean or refer to State Implementation Plan.
    (x) The initials TSD mean or refer to Technical Support Document.
    (xi) The initial ug/m3 mean or refer to micrograms per cubic meter.
    (xii) The initials WDEQ mean or refer to the Wyoming Department of 
Environmental Quality.
    (xiii) The words Wyoming and State mean the State of Wyoming, 
unless the context indicates otherwise.

Table of Contents

I. General Information
II. Background
    A. 2006 PM2.5 NAAQS and Interstate Transport
    B. Rules Addressing Interstate Transport for the 2006 
PM2.5 NAAQS
    C. EPA Guidance
III. Wyoming's Submittal
IV. EPA's Evaluation
    A. Identification of Nonattainment and Maintenance Receptors
    B. Evaluation of Significant Contribution to Nonattainment
    C. Evaluation of Interference With Maintenance
    D. Evaluation of Interference With Measures To Prevent 
Significant Deterioration
V. Proposed Action
VI. Statutory and Executive Orders Review

I. General Information

What should I consider as I prepare my comments for EPA?

    1. Submitting confidential business information (CBI). Do not 
submit CBI to EPA through http://www.regulations.gov or email. Clearly 
mark the part or all of the information that you claim to be CBI. For 
CBI information in a disk or CD

[[Page 28211]]

ROM that you mail to EPA, mark the outside of the disk or CD ROM as CBI 
and then identify electronically within the disk or CD ROM the specific 
information that is claimed as CBI. In addition to one complete version 
of the comment that includes information claimed as CBI, a copy of the 
comment that does not contain the information claimed as CBI must be 
submitted for inclusion in the public docket. Information so marked 
will not be disclosed except in accordance with procedures set forth in 
40 CFR part 2.
    2. Tips for preparing your comments. When submitting comments, 
remember to:
     Identify the rulemaking by docket number and other 
identifying information (subject heading, Federal Register date and 
page number).
     Follow directions--The agency may ask you to respond to 
specific questions or organize comments by referencing a Code of 
Federal Regulations (CFR) part or section number.
     Explain why you agree or disagree; suggest alternatives 
and substitute language for your requested changes.
     Describe any assumptions and provide any technical 
information and/or data that you used.
     If you estimate potential costs or burdens, explain how 
you arrived at your estimate in sufficient detail to allow for it to be 
reproduced.
     Provide specific examples to illustrate your concerns, and 
suggest alternatives.
     Explain your views as clearly as possible, avoiding the 
use of profanity or personal threats.
     Make sure to submit your comments by the comment period 
deadline identified.

II. Background

A. 2006 PM2.5 NAAQS and Interstate Transport

    On September 21, 2006, EPA promulgated a final rule revising the 
1997 24-hour primary and secondary NAAQS for PM2.5 from 65 
micrograms per cubic meter ([mu]g/m\3\) to 35 [mu]g/m\3\ (October 17, 
2006, 71 FR 61144).
    Section 110(a)(1) of the CAA requires each state to submit to EPA, 
within three years (or such shorter period as the Administrator may 
prescribe) after the promulgation of a primary or secondary NAAQS or 
any revision thereof, a SIP that provides for the ``implementation, 
maintenance, and enforcement'' of such NAAQS. EPA refers to these 
specific submittals as ``infrastructure'' SIPs because they are 
intended to address basic structural SIP requirements for new or 
revised NAAQS. For the 2006 24-hour PM2.5 NAAQS, these 
infrastructure SIPs were due on September 21, 2009. CAA section 
110(a)(2) includes a list of specific elements that ``[e]ach such plan 
submission'' must meet.
    The interstate transport provisions in CAA section 110(a)(2)(D)(i) 
(also called ``good neighbor'' provisions) require each state to submit 
a SIP that prohibits emissions that will have certain adverse air 
quality effects in other states. CAA section 110(a)(2)(D)(i) identifies 
four distinct elements related to the impacts of air pollutants 
transported across state lines. The two elements under 
110(a)(2)(D)(i)(I) require SIPs to contain adequate provisions to 
prohibit any source or other type of emissions activity within the 
state from emitting air pollutants that will (element 1) contribute 
significantly to nonattainment in any other state with respect to any 
such national primary or secondary NAAQS, and (element 2) interfere 
with maintenance by any other state with respect to the same NAAQS. The 
two elements under 110(a)(2)(D)(i)(II) require SIPs to contain adequate 
provisions to prohibit emissions that will interfere with measures 
required to be included in the applicable implementation plan for any 
other state under part C (element 3) to prevent significant 
deterioration of air quality or (element 4) to protect visibility. In 
this action, EPA is addressing elements one, two and three of CAA 
section 110(a)(2)(D)(i).

B. Rules Addressing Interstate Transport for the 2006 PM2.5 NAAQS

    EPA has previously addressed the requirements of CAA section 
110(a)(2)(D)(i)(I) in past regulatory actions.\1\ Most recently, EPA 
published the final Cross State Air Pollution Rule (CSAPR or 
``Transport Rule'') to address CAA section 110(a)(2)(D)(i)(I) in the 
eastern portion of the United States with respect to the 2006 
PM2.5 NAAQS, the 1997 PM2.5 NAAQS, and the 1997 
8-hour ozone NAAQS (August 8, 2011, 76 FR 48208). CSAPR replaces the 
earlier Clean Air Interstate Rule (CAIR) which was judicially 
remanded.\2\ See North Carolina v. EPA, 531 F.3d 896 (D.C. Cir. 2008). 
On August 21, 2012, the U.S. Court of Appeals for the D.C. Circuit 
issued a decision vacating CSAPR, see EME Homer City Generation, L.P. 
v. EPA, 696 F.3d 7 (D.C. Cir. 2012), and ordering EPA to continue 
implementing CAIR in the interim. However, on April 29, 2014, the U.S. 
Supreme Court reversed and remanded the D.C. Circuit's ruling and 
upheld EPA's approach in the CSAPR. EPA v. EME Homer City Generation, 
L.P., 134 S.Ct. 1584, 1610 (2014). After the U.S. Supreme Court 
decision, EPA filed a motion to lift the stay on CSAPR and asked the 
D.C. Circuit to toll CSAPR's compliance deadlines by three years. On 
October 23, 2014 the D.C. Circuit granted EPA's motion and lifted the 
stay on CSAPR. EME Homer City Generation, L.P. v. EPA, No. 11-1302 
(D.C. Cir. Oct. 23, 2014), Order at 3. EPA began CSAPR implementation 
on January 1, 2015 pursuant to the D.C. Circuit's directive lifting the 
stay. The State of Wyoming was not covered by CSAPR, and EPA made no 
determinations in the rule regarding whether emissions from sources in 
Wyoming significantly contribute to nonattainment or interfere with 
maintenance of the 2006 24-hour PM2.5 NAAQS in another 
state.
---------------------------------------------------------------------------

    \1\ See NOX SIP Call, 63 FR 57371 (October 27, 1998); 
Clean Air Interstate Rule (CAIR), 70 FR 25172 (May 12, 2005); and 
Transport Rule or Cross-State Air Pollution Rule, 76 FR 48208 
(August 8, 2011).
    \2\ CAIR addressed the 1997 annual and 24-hour PM2.5 
NAAQS, and the 1997 8-hour ozone NAAQS. It did not address the 2006 
24-hour PM2.5 NAAQS.
---------------------------------------------------------------------------

C. EPA Guidance

    On September 25, 2009, EPA issued a guidance memorandum that 
provides recommendations to states for making submissions to meet the 
requirements of CAA section 110(a)(2)(D)(i) for the 2006 
PM2.5 standards (``2006 PM2.5 NAAQS 
Infrastructure Guidance'' or ``Guidance'').\3\ With respect to element 
1 of CAA section 110(a)(2)(D)(i) to prohibit emissions that will 
contribute significantly to nonattainment of the NAAQS in any other 
state, the 2006 PM2.5 NAAQS Infrastructure Guidance advised 
states to include in their section 110(a)(2)(D)(i)(I) SIP submissions 
an adequate technical analysis to support their conclusions regarding 
interstate pollution transport, e.g., information concerning emissions 
in the state, meteorological conditions in the state and in potentially 
impacted states, monitored ambient pollutant concentrations in the 
state and in potentially impacted states, distances to the nearest 
areas not attaining the NAAQS in other states, and air quality 
modeling.\4\
---------------------------------------------------------------------------

    \3\ See Memorandum from William T. Harnett entitled ``Guidance 
on SIP Elements Required Under Sections 110(a)(1) and (2) for the 
2006 24-Hour Fine Particle (PM2.5) National Ambient Air 
Quality Standards (NAAQS),'' September 25, 2009, available at http://www.epa.gov/ttn/caaa/t1/memoranda/20090925_harnett_pm25_sip_110a12.pdf.
    \4\ The 2006 PM2.5 NAAQS Infrastructure Guidance 
stated that EPA was working on a new rule to replace CAIR that would 
address issues raised by the court in the North Carolina case and 
that would provide guidance to states in addressing the requirements 
related to interstate transport in CAA section 110(a)(2)(D)(i)(I) 
for the 2006 24-hour PM2.5 NAAQS. It also noted that 
states could not rely on the CAIR rule for section 
110(a)(2)(D)(i)(I) submissions for the 2006 24-hour PM2.5 
NAAQS because the CAIR rule did not address this NAAQS. See 2006 
PM2.5 NAAQS Infrastructure Guidance at 3.

---------------------------------------------------------------------------

[[Page 28212]]

    With respect to element 2 of CAA section 110(a)(2)(D)(i) to 
prohibit emissions that would interfere with maintenance of the NAAQS 
by any other state, the Guidance stated that SIP submissions must 
address this independent and distinct requirement of the statute and 
provide technical information appropriate to support the State's 
conclusions, and suggested consideration of the same technical 
information that would be appropriate for element 1 of this CAA 
requirement.
    In this action, EPA is proposing to use the conceptual approach to 
evaluating interstate pollution transport under CAA section 
110(a)(2)(D)(i)(I) that EPA explained in the 2006 PM2.5 
NAAQS Infrastructure Guidance and CSAPR. As such, we find that the CAA 
section 110(a)(2)(D)(i)(I) SIP submission from Wyoming may be evaluated 
using a ``weight of evidence'' approach that takes into account 
available relevant information, including the factors recommended in 
the 2006 PM2.5 NAAQS Infrastructure Guidance. These 
submissions can rely on modeling when acceptable modeling technical 
analyses are available, but EPA does not believe that modeling is 
necessarily required if other available information is sufficient to 
evaluate the presence or degree of interstate transport in a given 
situation.
    With respect to the requirements in section 110(a)(2)(D)(i)(II) 
which address elements 3 (PSD) and 4 (visibility), EPA most recently 
issued an infrastructure guidance memo on September 13, 2013 that 
included guidance on these two elements.\5\ For the purposes of this 
action, this memo will hereon be referred to as the ``2013 I-SIP 
Guidance.''
---------------------------------------------------------------------------

    \5\ See ``Guidance on Infrastructure State Implementation Plan 
(SIP) Elements under Clean Air Act Sections 110(a)(1) and (2)'' 
dated September 13, 2013, in the docket for this action.
---------------------------------------------------------------------------

III. Wyoming's Submittal

    On August 19, 2011, the Wyoming Department of Environmental Quality 
(WDEQ) made a submission certifying that Wyoming's SIP is adequate to 
implement the 2006 24-hour PM2.5 NAAQS for all the 
``infrastructure'' requirements of CAA section 110(a)(2). In this 
analysis, WDEQ simply listed the regulatory and non-regulatory 
documents that it felt demonstrated the Wyoming SIP's adequacy to meet 
the 110(a)(2) requirements with respect to the 2006 24-hour 
PM2.5 NAAQS.\6\
---------------------------------------------------------------------------

    \6\ WDEQ's certification letter, dated August 19, 2011 is 
included in the docket for this action.
---------------------------------------------------------------------------

    To meet the requirements of CAA sections 110(a)(2)(D)(i)(I) 
(elements 1 and 2), WDEQ's submission referenced the State's May 3, 
2007 interstate transport SIP. The May 3, 2007 SIP was determined by 
EPA to meet the interstate transport requirements of CAA section 
110(a)(2)(D)(i) for the 1997 ozone and PM2.5 NAAQS, and was 
therefore approved by EPA on May 8, 2008 (73 FR 26019). However, 
Wyoming's May 3, 2007 SIP did not address the 2006 24-hour 
PM2.5 NAAQS. On April 23, 2015, WDEQ sent EPA a letter 
clarifying that it considered the factors relied upon as part of the 
May 3, 2007 submittal to also be applicable to a transport analysis for 
the 2006 24-hour PM2.5 NAAQS.\7\
---------------------------------------------------------------------------

    \7\ Wyoming's clarification letter is available in the docket 
for this action. Wyoming's May 3rd, 2007 Interstate Transport SIP 
can be found in the docket for that action (EPA-R08-OAR-2007-0648).
---------------------------------------------------------------------------

    To meet the element 3 (PSD) requirement of CAA section 
110(a)(2)(D)(i), Wyoming referenced Wyoming Air Quality Standards and 
Regulations (WAQSR) Chapter 6, section 2, Permit requirements for 
construction, modification, and operation, as well as its May 3, 2007 
Interstate Transport SIP. In its April 23, 2015 letter to EPA, Wyoming 
clarified its element 3 submittal by indicating that it will issue 
permits to sources locating in nonattainment areas pursuant to 40 CFR 
part 51, appendix S until it has a SIP-approved nonattainment NSR 
program.

IV. EPA's Evaluation

    To determine whether the CAA section 110(a)(2)(D)(i)(I) requirement 
is satisfied, EPA first determines whether a state's emissions 
contribute significantly to nonattainment or interfere with maintenance 
in other states. If a state is determined not to have such contribution 
or interference, then section 110(a)(2)(D)(i)(I) does not require any 
changes to that state's SIP.
    Consistent with the first step of EPA's approach in the 1998 
NOX SIP call, the 2005 CAIR, and the 2011 CSAPR, EPA 
evaluated impacts of emissions from Wyoming with respect to specific 
ambient air monitors identified as having nonattainment and/or 
maintenance problems, which we refer to as ``receptors.'' To evaluate 
these impacts, and in the absence of relevant modeling of Wyoming 
emissions, EPA examined factors suggested by the 2006 Guidance such as 
monitoring data, topography, and meteorology. EPA notes that no single 
piece of information is by itself dispositive of the issue. Instead, 
the total weight of all the evidence taken together is used to evaluate 
significant contributions to nonattainment or interference with 
maintenance of the 2006 24-hour PM2.5 NAAQS in another 
state.
    As noted above, Wyoming's August 19, 2011 submission does not 
include a technical demonstration specific to the 2006 24-hour 
PM2.5 NAAQS. Rather, the State relied on the transport 
analysis it conducted for a previous PM2.5 NAAQS, later 
clarifying that it had considered parts of this analysis to be relevant 
for the purposes of the 2006 PM2.5 standard. While EPA does 
not agree with the State's position that the analysis from its May 3, 
2007 is also applicable to the 2006 24-hour PM2.5 NAAQS, we 
agree with Wyoming's determination that the existing SIP has adequate 
provisions to meet the CAA requirements based on EPA's supplemental 
evaluation. For this reason, we propose to approve the 
110(a)(2)(D)(i)(I) portion of the submission based on EPA's 
supplemental evaluation of relevant technical information. Our 
evaluation demonstrates that emissions from Wyoming do not 
significantly contribute to nonattainment or interfere with maintenance 
of the 2006 24-hour PM2.5 NAAQS in any other state and that 
the existing Wyoming SIP is, therefore, adequate to meet the 
requirements of CAA section 110(a)(2)(D)(i)(I) for the 2006 24-hour 
PM2.5 NAAQS.
    Our supplemental evaluation considers several factors, including 
identification of the ambient air monitors in other states that are 
appropriate ``nonattainment receptors'' or ``maintenance receptors,'' 
consistent with EPA's approach in the CSAPR, and additional technical 
information to evaluate whether emissions from Wyoming contribute 
significantly to nonattainment or interfere with maintenance of the 
2006 24-hour PM2.5 NAAQS at these receptors.
    Our Technical Support Document (TSD) contains a detailed evaluation 
and is available in the public docket for this rulemaking, which may be 
accessed online at http://www.regulations.gov, docket number EPA-R08-
OAR-2012-0351. Below, we provide a summary of our analysis.

A. Identification of Nonattainment and Maintenance Receptors

    EPA evaluated data from existing monitors over three overlapping 3-
year periods (i.e., 2009-2011, 2010-2012, and 2011-2013) to determine 
which areas are expected to be violating the 2006 24-hour 
PM2.5 NAAQS and which

[[Page 28213]]

areas might have difficulty maintaining attainment of the standard. If 
a monitoring site measured a violation of the 2006 24-hour 
PM2.5 NAAQS during the most recent 3-year period (2011-
2013), then that monitor location was evaluated for purposes of the 
significant contribution to nonattainment (element 1) of section 
110(a)(2)(D)(i). If, on the other hand, a monitoring site shows 
attainment of the 2006 24-hour PM2.5 NAAQS during the most 
recent 3-year period (2011-2013) but a violation in at least one of the 
previous two 3-year periods (2010-2012 or 2009-2011), then that monitor 
location was evaluated for purposes of the interfere with maintenance 
(element 2) of section 110(a)(2)(D)(i).
    This approach is similar to that used in the modeling done during 
the development of CSAPR, but differs in that it relies on monitoring 
data (rather than modeling) for the western states not included in the 
CSAPR modeling domain.\8\ By this method, EPA has identified those 
areas with monitors to be considered ``nonattainment receptors'' or 
``maintenance receptors'' for evaluating whether the emissions from 
sources in another state could significantly contribute to 
nonattainment in, or interfere with maintenance in, that particular 
area.
---------------------------------------------------------------------------

    \8\ As noted, the State of Wyoming was not included in the CSAPR 
modeling domain.
---------------------------------------------------------------------------

    EPA continues to believe that the more widespread and serious 
transport problems in the eastern United States are analytically 
distinct. For the 2006 24-hour PM2.5 NAAQS, EPA believes 
that nonattainment and maintenance problems in the western United 
States are relatively local in nature with only limited impacts from 
interstate transport. In CSAPR, EPA did not calculate the portion of 
any downwind state's predicted PM2.5 concentrations that 
would result from emissions from individual western states, such as 
Wyoming. Accordingly, EPA believes that section 110(a)(2)(D)(i)(I) SIP 
submissions for states outside the geographic area analyzed to develop 
CSAPR may be evaluated using a ``weight of evidence'' approach that 
takes into account available relevant information, such as that 
recommended by the EPA in the Guidance. Such information may include, 
but is not limited to, the amount of emissions in the state relevant to 
the NAAQS in question, the meteorological conditions in the area, the 
distance from the state to the nearest monitors in other states that 
are appropriate receptors, or such other information as may be 
probative to consider as to whether sources in the state may contribute 
significantly to nonattainment or interfere with maintenance of the 
2006 24-hour PM2.5 NAAQS in other states. These submissions 
can rely on modeling when acceptable modeling technical analyses are 
available, but EPA does not believe that modeling is necessarily 
required if other available information is sufficient to evaluate the 
presence or degree of interstate transport in a given situation.

B. Evaluation of Significant Contribution to Nonattainment

    EPA reviewed technical information to evaluate the potential for 
Wyoming emissions to contribute significantly to nonattainment of the 
2006 24-hour PM2.5 NAAQS at specified monitoring sites in 
the Western U.S.\9\ EPA first identified as ``nonattainment receptors'' 
all monitoring sites in the western states that had recorded 
PM2.5 design values above the level of the 2006 24-hour 
PM2.5 NAAQS (35 [mu]g/m3) during the years 2011-2013.\10\ 
See Section III of our TSD for more a more detailed description of 
EPA's methodology for selection of nonattainment receptors.
---------------------------------------------------------------------------

    \9\ EPA also considered potential PM2.5 transport 
from Wyoming to the nearest nonattainment and maintenance receptors 
located in the eastern, midwestern and southern states covered by 
CSAPR and believes it is reasonable to conclude that, given the 
significant distance from Wyoming to the nearest such receptor (in 
Wisconsin) and the relatively insignificant amount of emissions from 
Wyoming that could potentially be transported such a distance when 
compared to downwind states whose contribution was modeled for 
CSAPR, emissions from Wyoming sources do not significantly 
contribute to nonattainment or interfere with maintenance of the 
2006 24-hour PM2.5 NAAQS at this location. These same 
factors also support a finding that emissions from Wyoming sources 
neither contribute significantly to nonattainment nor interfere with 
maintenance of the 2006 24-hour PM2.5 NAAQS at any 
location further east. See TSD at section I.B.3.
    \10\ Because CAIR did not cover states in the Western United 
States, these data are not significantly impacted by the remanded 
CAIR and thus could be considered in this analysis. In contrast, 
recent air quality data in the eastern, midwestern and southern 
states are significantly impacted by reductions associated with CAIR 
and because CSAPR was developed to replace CAIR, EPA could not 
consider reductions associated with the CAIR in the base case 
transport analysis for those states. See 76 FR at 48223-24.
---------------------------------------------------------------------------

    Because geographic distance is a relevant factor in the assessment 
of potential pollution transport, EPA first reviewed information 
related to potential transport of PM2.5 pollution from 
Wyoming to the nonattainment receptors in states bordering Wyoming, 
which were located in Idaho, Montana and Utah. As detailed in our TSD, 
the following factors support a finding that emissions from Wyoming do 
not significantly contribute to nonattainment of the 2006 24-hour 
PM2.5 NAAQS in Idaho, Montana and Utah: (1) Technical 
information, such as data from monitors in the vicinity of these 
nonattainment receptors, related to the nature of local emissions; (2) 
topographical considerations such as intervening mountain ranges which 
tend to create physical impediments for pollution transport; and (3) 
meteorological considerations such as prevailing winds. While none of 
these factors by itself would necessarily show non-contribution, when 
taken together in a weight-of-evidence assessment they are sufficient 
for EPA to determine that emissions from Wyoming do not significantly 
contribute to nonattainment at the Idaho, Montana and Utah receptors.
    EPA also evaluated potential PM2.5 transport to 
nonattainment receptors in the more distant western states of Oregon 
and California. The following factors support a finding that emissions 
from Wyoming do not significantly contribute to nonattainment of the 
2006 24-hour PM2.5 NAAQS in any of these states: (1) The 
significant distance from Wyoming to the nonattainment receptors in 
these states; (2) technical information, such as data from nearby 
monitors related to the nature of local emissions; and (3) the presence 
of intervening mountain ranges, which tend to impede pollution 
transport.
    Based on our evaluation, we propose to conclude that emissions of 
direct PM2.5 and PM2.5 precursors from sources in 
the State of Wyoming do not significantly contribute to nonattainment 
of the 2006 24-hour PM2.5 standards in any other state, that 
the existing SIP for the State of Wyoming is adequate to satisfy the 
``significant contribution'' requirements of CAA section 
110(a)(2)(D)(i)(I) with respect to the 2006 24-hour PM2.5 
standards, and that the State of Wyoming therefore does not need to 
adopt additional controls for purposes of implementing the 
``significant contribution to nonattainment'' requirement of 
110(a)(2)(D)(i)(I) with respect to that NAAQS at this time.

C. Evaluation of Interference With Maintenance

    We also reviewed technical information to evaluate the potential 
for Wyoming emissions to interfere with maintenance of the 2006 24-hour 
PM2.5 standards at specified monitoring sites in the Western 
U.S. EPA first identified as ``maintenance receptors'' all monitoring 
sites in the western states that had recorded PM2.5 design 
values above the level of the 2006 24-hour PM2.5 NAAQS (35 
[mu]g/m\3\) during the 2009-2011 and/or 2010-2012 periods but below 
this standard during the

[[Page 28214]]

2011-2013 period. See section III of our TSD for more information 
regarding EPA's methodology for selection of maintenance receptors. All 
of the maintenance receptors in the western states are located in 
California, Utah and Montana. EPA therefore evaluated the potential for 
transport of Wyoming emissions to the maintenance receptors located in 
these states. As detailed in our TSD, the following factors support a 
finding that emissions from Wyoming do not interfere with maintenance 
of the 2006 24-hour PM2.5 NAAQS in those states: (1) 
Technical information, such as data from monitors near maintenance 
receptors, relating to the nature of local emissions, and (2) the 
significant distance between Wyoming and these maintenance receptors.
    Based on this evaluation, EPA proposes to conclude that emissions 
of direct PM2.5 and PM2.5 precursors from sources 
in the State of Wyoming do not interfere with maintenance of the 2006 
24-hour PM2.5 standards in any other state, that the 
existing SIP for the State of Wyoming is adequate to satisfy the 
``interfere with maintenance'' requirements of CAA section 
110(a)(2)(D)(i)(I), and that the State of Wyoming therefore does not 
need to adopt additional controls for purposes of implementing the 
``interfere with maintenance'' requirements of CAA section 
110(a)(2)(D)(i)(I) with respect to that NAAQS at this time.

D. Evaluation of Interference With Measures To Prevent Significant 
Deterioration

    With regard to the PSD portion of CAA section 110(a)(2)(D)(i)(II), 
this requirement may be met by a state's confirmation in an 
infrastructure SIP submission that new major sources and major 
modifications in the state are subject to a comprehensive EPA-approved 
PSD permitting program in the SIP that applies to all regulated new 
source review (NSR) pollutants and that satisfies the requirements of 
EPA's PSD implementation rules.\11\ On December 6, 2013, EPA approved 
CAA section 110(a)(2) elements (C) and (J) for Wyoming's infrastructure 
SIP for the 2006 24-hour PM2.5 NAAQS with respect to PSD 
requirements for regulated NSR pollutants (78 FR 73445). As discussed 
in detail in the proposed rulemaking for that final action, the 
concurrent approval of PSD-related revisions which incorporated certain 
requirements of the 2010 PM2.5 Increment Rule to the Wyoming 
SIP action ensured that Wyoming's SIP-approved PSD program meets the 
current structural requirements of 110(a)(2)(C) and (J) to have a PSD 
program that applies to all regulated NSR pollutants.\12\
---------------------------------------------------------------------------

    \11\ See 2013 I-SIP Guidance.
    \12\ As described in the proposed action (78 FR 54828, September 
6, 2013) for the final December 6, 2013 rulemaking, EPA did not 
approve certain portions of the State's incorporation of the 2010 
PM2.5 Increment Rule because these portions were 
ultimately removed from EPA's PSD regulations.
---------------------------------------------------------------------------

    As stated in the 2013 I-SIP Guidance, in-state sources not subject 
to PSD for any one or more of the pollutants subject to regulation 
under the CAA because they are in a nonattainment area for a NAAQS 
related to those particular pollutants may also have the potential to 
interfere with PSD in an attainment or unclassifiable area of another 
state. One way a state may satisfy element 3 with respect to these 
sources is by citing an air agency's EPA-approved nonattainment NSR 
provisions addressing any pollutants for which the state has designated 
nonattainment areas. Alternatively, if an air agency makes a submission 
indicating that it issues permits pursuant to 40 CFR part 51, appendix 
S in a nonattainment area because a nonattainment NSR program for a 
particular NAAQS pollutant has not yet been approved by EPA for that 
area, that permitting program may generally be considered adequate for 
purposes of meeting the requirements of element 3 with respect to 
sources and pollutants subject to such program. Where neither of the 
circumstances described above exist, it may also be possible for EPA to 
find, given the facts of the situation, that other SIP provisions and/
or physical conditions are adequate to prohibit interference by such 
sources with other air agencies' measures to prevent significant 
deterioration of air quality.
    EPA recently finalized a rulemaking which disapproved a portion of 
Wyoming's May 10, 2011 SIP revision that attempted to add nonattainment 
NSR permitting requirements to the state plan for the first time (80 FR 
9194, February 20, 2015). In this partial disapproval, EPA found that 
this SIP revision failed to create unambiguous and enforceable 
obligations for sources that would be subject to the nonattainment NSR 
requirements. Accordingly, the State does not currently have any SIP-
approved nonattainment NSR permitting provisions which would subject 
sources locating in nonattainment areas in the State to regulation. The 
State has confirmed, via a clarification letter sent to EPA on April 
23, 2015, that it will issue permits to sources locating in such 
nonattainment areas pursuant to 40 CFR part 51, appendix S until it has 
a SIP-approved nonattainment NSR program.\13\
---------------------------------------------------------------------------

    \13\ EPA notes that the State's application of appendix S would 
only currently apply to the Upper Green River Basin 2008 ozone 
nonattainment area. Wyoming has had a construction ban in place and 
approved into the SIP for over twenty years in order to meet 
nonattainment NSR requirements in the Sheridan coarse particulate 
matter (PM10) nonattainment area (See WAQSR, Chapter 6, 
section 2(c)(ii)(B)).
---------------------------------------------------------------------------

    Because the State has committed to applying appendix S until it has 
a SIP-approved nonattainment NSR program, EPA is proposing to approve 
the infrastructure SIP submission with regard to the requirements of 
element 3 of section 110(a)(2)(D)(i) for the 2006 24-hour 
PM2.5 NAAQS.

V. Proposed Action

    EPA is proposing to approve the 110(a)(2)(D)(i)(I) portion of 
Wyoming's August 19, 2011 submission. We propose to approve elements 1 
and 2 of this portion of the submission based on EPA's supplemental 
evaluation of relevant technical information, which supports a finding 
that emissions from Wyoming do not significantly contribute to 
nonattainment or interfere with maintenance of the 2006 24-hour 
PM2.5 NAAQS in any other state and that the existing Wyoming 
SIP is, therefore, adequate to meet the requirements of CAA section 
110(a)(2)(D)(i)(I) for the 2006 24-hour PM2.5 NAAQS.
    EPA is also proposing to approve element 3 of 110(a)(2)(D)(i) from 
Wyoming's August 19, 2011 submission, based on a finding that the 
Wyoming SIP is adequate to meet the PSD requirement of CAA section 
110(a)(2)(D)(i)(II).

VI. Statutory and Executive Orders Review

    Under the CAA, 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, EPA's role is to approve state choices, 
provided that they meet the criteria of the CAA. Accordingly, this 
proposed action merely approves state law as meeting federal 
requirements; this proposed action 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 Order 
12866 (58 FR 51735, October 4, 1993);
     Does not impose an information collection burden under the 
provisions

[[Page 28215]]

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 CAA; and,
     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).
    The SIP is not approved to 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, the rule does 
not have tribal implications and will not impose substantial direct 
costs on tribal governments or preempt tribal law as specified by 
Executive Order 13175 (65 FR 67249, November 9, 2000).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Particulate matter, Reporting 
and recordkeeping requirements.

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

    Dated: May 1, 2015.
Shaun L. McGrath,
Regional Administrator, Region 8.
[FR Doc. 2015-11782 Filed 5-15-15; 8:45 am]
 BILLING CODE 6560-50-P