
[Federal Register Volume 82, Number 22 (Friday, February 3, 2017)]
[Rules and Regulations]
[Pages 9142-9155]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-02197]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2016-0521; FRL-9959-15-Region 8]


Approval and Disapproval and Promulgation of Air Quality 
Implementation Plans; Interstate Transport for Wyoming

AGENCY: The Environmental Protection Agency.

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is taking final 
action on portions of six submissions from the state of Wyoming that 
are intended to demonstrate that the State Implementation Plan (SIP) 
meets certain interstate transport requirements of the Clean Air Act 
(Act or CAA). These submissions address the 2006 and 2012 fine 
particulate matter (PM2.5) National Ambient Air Quality 
Standards (NAAQS), 2008 ozone NAAQS, 2008 lead (Pb) NAAQS, 2010 sulfur 
dioxide (SO2) NAAQS and 2010 nitrogen dioxide 
(NO2) NAAQS. The interstate transport requirements under the 
CAA consist of four elements (or prongs): Significant contribution to 
nonattainment (prong 1) and interference with maintenance (prong 2) of 
the NAAQS in other states; and interference with measures required to 
be included in the plan for other states to prevent significant 
deterioration of air quality (prong 3) or to protect visibility (prong 
4). Specifically, the EPA is approving Wyoming's submissions for 
interstate transport prongs 1 and 2 for the 2008 Pb and 2010 
NO2 NAAQS, and approving prong 1 and disapproving prong 2 
for the 2008 ozone NAAQS. The EPA is also approving interstate 
transport prong 4 for the 2008 Pb and 2010 SO2 NAAQS, and 
disapproving prong 4 for the 2006 PM2.5, 2008 ozone, 2010 
NO2 and 2012 PM2.5 NAAQS.

DATES: This final rule is effective on March 6, 2017.

ADDRESSES: The EPA has established a docket for this action under 
Docket Identification Number EPA-R08-OAR-2016-0521. All documents in 
the docket are listed on the http://www.regulations.gov index. Although 
listed in the index, some information may not be publicly available, 
e.g., Confidential Business Information 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 
through http://www.regulations.gov or in hard copy at the Air Program, 
Environmental Protection Agency, Region 8, 1595 Wynkoop Street, Denver, 
Colorado 80202-1129. The EPA requests that 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, Mail Code 8P-AR, 1595 
Wynkoop Street, Denver, Colorado 80202-1129, (303) 312-7104, 
clark.adam@epa.gov.

I. Background

    On November 18, 2016, the EPA proposed action on six submittals 
from Wyoming intended to address the interstate transport requirements 
of CAA section 110(a)(2)(D)(i) for the 2008 Pb, 2008 ozone, 2010 
NO2, 2010 SO2, and 2006 and 2012 PM2.5 
NAAQS. 81 FR 81712. In that action, the EPA proposed to approve CAA 
section 110(a)(2)(D)(i)(I) prongs 1, 2 and 4 for the 2008 Pb NAAQS, 
prong 1 for the 2008 ozone NAAQS, prongs 1 and 2 for NO2, 
and prong 4 for the 2010 SO2 NAAQS, and proposed to 
disapprove prong 4 for the 2006 PM2.5, 2008 ozone, 2010 
NO2 and 2012 PM2.5 NAAQS, and prong 2 for the 
2008 ozone NAAQS. An explanation of the CAA requirements, a detailed 
analysis of the State's submittals, and the EPA's rationale for all 
proposed actions were provided in the notice of proposed rulemaking, 
and will not generally be restated here.
    The public comment period for this proposed rule ended on December 
19, 2016. The EPA received seven comments on the proposal, which will 
be addressed in the ``Response to Comments'' section, below. All of the 
comments relate to the EPA's proposed action with respect to prongs 1 
and 2 of CAA section 110(a)(2)(D)(i)(I) for the 2008 ozone NAAQS. We 
had proposed to approve the portion of the Wyoming SIP submittal 
pertaining to the CAA requirement that the State prohibit any emissions 
activity within the State from emitting air pollutants which will 
significantly contribute to nonattainment (prong 1) of the 2008 ozone 
NAAQS in other states and proposed to disapprove the portion of the 
Wyoming SIP submittal pertaining to the requirement that the state 
prohibit any emissions activity within the state interfering with 
maintenance (prong 2) of the 2008 ozone NAAQS in other states. In 
proposing to take this action, we noted two deficiencies in Wyoming's 
submittal: (1) Wyoming limited its

[[Page 9143]]

technical analysis to a discussion on general wind patterns relative to 
areas designated nonattainment in certain states that are 
geographically closest to Wyoming, and did not consider whether 
emission activity in the State specifically contributed to such areas 
on days with measured exceedances of the NAAQS or in other areas not 
designated nonattainment; and (2) Wyoming did not give the ``interfere 
with maintenance'' clause of CAA section 110(a)(2)(D)(i)(I) independent 
significance because its analysis did not attempt to evaluate the 
potential impact of Wyoming's emissions on ozone in areas that may have 
issues maintaining air quality.
    In addition, the EPA cited at proposal certain technical 
information and a related analysis the agency conducted in order to 
facilitate efforts to address interstate transport requirements for the 
2008 ozone NAAQS, which was also used to support the recently finalized 
Cross-State Air Pollution Rule Update for the 2008 ozone NAAQS (CSAPR 
Update).\1\ In particular, the EPA cited to air quality modeling which 
(1) identified locations in the U.S. where the EPA anticipates 
nonattainment or maintenance issues in 2017 for the 2008 ozone NAAQS 
(these are identified as nonattainment and maintenance receptors), and 
(2) quantified the projected contributions from emissions from upwind 
states to downwind ozone concentrations at the nonattainment and 
maintenance receptors in 2017. The notice also proposed to apply an air 
quality threshold of one percent of the NAAQS, equivalent to 0.75 ppb 
with respect to the 2008 ozone NAAQS, to determine whether a state was 
``linked'' to an identified downwind air quality problem in another 
state such that the upwind state may significantly contribute to 
nonattainment or interfere with maintenance of the NAAQS in the 
downwind state.
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    \1\ ``Cross-State Air Pollution Rule Update for the 2008 Ozone 
NAAQS.'' 81 FR 74504, October 26, 2016.
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    The modeling data showed that emissions from Wyoming contribute 
above the one percent threshold to one identified maintenance receptor 
in the Denver, Colorado area. Accordingly, as the Wyoming Department of 
Environmental Quality (WDEQ) did not provide technical analysis 
sufficient to support the State's conclusion that emissions originating 
in Wyoming do not interfere with maintenance of the 2008 ozone NAAQS in 
any other state, the EPA proposed to disapprove the Wyoming SIP as to 
prong 2 of CAA section 110(a)(2)(D)(i)(I). The proposal also noted 
that, despite the deficiencies in Wyoming's SIP submission as to prong 
1, the modeling data confirmed the State's conclusion that it does not 
significantly contribute to nonattainment of the 2008 ozone NAAQS in 
any other state. Accordingly, the EPA proposed to approve Wyoming's SIP 
as meeting the prong 1 requirements of CAA section 110(a)(2)(D)(i)(I) 
for the 2008 ozone NAAQS.

II. Response to Comments

    Comment: Several commenters asserted that the State should be given 
more time to review the CSAPR Update modeling analysis before the EPA 
takes final action on Wyoming's SIP submittal addressing the prong 1 
and 2 requirements as to the 2008 ozone NAAQS. WDEQ submitted a comment 
letter on November 23, 2016, requesting a 90-day extension to the 30-
day comment period that the State asserted was necessary ``to devote 
significant time and energy reviewing the EPA's basis for the approval 
and disapproval of the State Plans named in the Proposed Rule.'' The 
State noted that the EPA had taken over two years and nine months to 
review Wyoming's February 6, 2014 submittal, and that it was therefore 
reasonable to allow 120 days for the State to review the EPA's proposed 
action and to provide additional information in support of its original 
SIP submission. The EPA responded to WDEQ with a December 6, 2016 
letter informing the State that we would not be extending the comment 
period for the proposed rule.\2\
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    \2\ EPA's December 6, 2016 letter is available in the docket for 
this action.
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    Commenter Utility Air Regulatory Group (UARG) asserted that the 
EPA's refusal to extend the comment period is unreasonable. UARG stated 
that the EPA did not dispute that the State needed additional time, but 
rather denied the extension request on grounds that opposing counsel in 
a proposed consent decree negotiated between the EPA and the Sierra 
Club had refused to extend the negotiated deadline. See Sierra Club v. 
McCarthy, Case No. 3:15-cv-04328-JD, (N.D. Cal), Joint Motion to Enter 
Partial Consent Decree (Oct. 15, 2015) (Document 57). UARG asserted 
that, because the consent decree was still proposed and therefore had 
not been entered by the court, the EPA could have taken action to 
modify the proposed consent decree or filed a motion with the district 
court to modify the deadline. The commenter asserted that the EPA 
should have either taken one of these actions, or disputed WDEQ's 
statement that it needed additional time.
    Several commenters asserted that Wyoming should be given an 
opportunity to review the recently-finalized CSAPR Update modeling to 
determine whether it is accurate or appropriate for Wyoming or the West 
overall. Commenter WEST Associates requested that the EPA allow Wyoming 
to re-examine and resubmit the prong 2 portion of the State's February 
6, 2014 submittal before moving forward with a final action.
    Response: The EPA disagrees with the commenters that the State has 
not had sufficient time to review the modeling analysis associated with 
the CSAPR Update Rulemaking. The EPA has provided several opportunities 
for states to review its modeling information relative to the 2008 
ozone NAAQS. The EPA first issued a memo to all states on January 22, 
2015, which included the preliminary modeling results assessing 
interstate transport with respect to the 2008 ozone NAAQS.\3\ This 
preliminary modeling showed that in 2018 Wyoming would contribute to a 
maintenance receptor above the one percent screening threshold used in 
the original CSAPR rulemaking. The EPA subsequently issued updated 
modeling in an August 4, 2015 Notice of Data Availability (NODA), which 
included a docket with substantial technical information on how the 
modeling was conducted, notably an Air Quality Modeling Technical 
Support Document.\4\ The updated air quality modeling also identified 
linkages between Wyoming and nonattainment and maintenance receptors in 
the Denver, Colorado area, and Wyoming submitted comments on the docket 
for the NODA. The modeling released in the NODA was used to support the 
proposed CSAPR Update, and the EPA provided additional, robust 
explanation and technical support for the modeling in that proposal (80 
FR 75706, December 23, 2015) and again in the final rule (81 FR 74504, 
October 26, 2016), which once more demonstrated a linkage between 
Wyoming and a maintenance receptor in the Denver, Colorado area, as 
described in the EPA's

[[Page 9144]]

proposed action on Wyoming's SIP submission.\5\
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    \3\ ``Information on the Interstate Transport ``Good Neighbor'' 
Provision for the 2008 Ozone National Ambient Air Quality Standards 
(NAAQS) under Clean Air Act (CAA) Section 110(a)(2)(D)(i)(I).'' 
January 22, 2015. This document, and the associated January 2015 
``Air Quality Modeling Technical Support Document for the 2008 Ozone 
NAAQS Transport Assessment,'' are available in the docket for this 
action.
    \4\ ``Updated Air Quality Modeling Technical Support Document 
for the 2008 Ozone NAAQS Transport Assessment,'' August 2015.
    \5\ The Air Quality Modeling Technical Support Document (AQM 
TSD) for each of these actions in the docket for this rulemaking.
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    Moreover, the EPA proposed a similar action with respect to Utah's 
SIP submission addressing interstate transport with respect to the 2008 
ozone NAAQS based on several deficiencies in that state's SIP and 
citing to the air quality modeling conducted to support the CSAPR 
Update, which demonstrated that Utah was also linked to nonattainment 
and maintenance receptors in Denver. May 10, 2016, 81 FR 28807. WDEQ 
reviewed and commented on the EPA's proposed disapproval action on 
Utah's interstate transport SIP submission in a June 9, 2016 comment 
letter submitted to the EPA.\6\ In that letter, WDEQ discussed the 
impact that the EPA's application of the one percent screening 
threshold to states linked to the Denver receptors would have on the 
state of Wyoming. Accordingly, Wyoming had several opportunities 
(including time since January 2015) to review and comment on the EPA's 
modeling conducted over the last two years and, as necessary, to 
supplement its submission with additional technical analysis addressing 
the linkages repeatedly identified in the EPA's analysis.
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    \6\ WDEQ's comment letter on the EPA's May 10, 2016 proposed 
action on the Utah submittal can be found on www.regulations.gov in 
the docket for that action, EPA-R08-OAR-2016-0107.
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    Finally, although the commenters focus on concerns relative to an 
opportunity to review the applicability of the EPA's air quality 
modeling, they do not address the clear deficiency in Wyoming's SIP 
identified in the EPA's proposed disapproval as to the prong 2 
requirements. As explained at proposal, in remanding the Clean Air 
Interstate Rule (CAIR) to the EPA in North Carolina v. EPA, the D.C. 
Circuit explained that the regulating authority must give the 
``interfere with maintenance'' clause of section 110(a)(2)(D)(i)(I) 
``independent significance'' by evaluating the impact of upwind state 
emissions on downwind areas that are at risk of future nonattainment, 
considering historic variability, even if they currently measure clean 
data.\7\ Wyoming's SIP submission did not give the ``interfere with 
maintenance'' clause of section 110(a)(2)(D)(i)(I) independent 
significance because its analysis did not evaluate the potential impact 
of Wyoming emissions on areas that may have issues maintaining that air 
quality, even if they are currently measuring clean data. Thus, even 
absent the EPA's modeling, the SIP submission was deficient as to 
addressing the requirements of prong 2 with respect to the 2008 ozone 
NAAQS. Finally, the EPA notes that finalization of this action in no 
way precludes the state of Wyoming from subsequently submitting a SIP 
or SIP revision to address the deficiencies identified here.
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    \7\ 531 F.3d 896, 910-11 (D.C. Cir. 2008) (holding that the EPA 
must give ``independent significance'' to each prong of CAA section 
110(a)(2)(D)(i)(I)).
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    Comment: Commenters WEST Associates and Basin Electric Power 
Cooperative (BEPC) stated that the EPA should wait for the litigation 
on the EPA's Federal Implementation Plan (FIP) for NOX-
related portions of the Wyoming Regional Haze SIP/FIP to be resolved 
before taking final action on prong 2 of Wyoming's February 6, 2014 
submittal. The commenters asserted that it is counterproductive to 
engage in a prong 2 analysis for ozone while the EPA's Regional Haze 
NOX FIP is still under appeal before the United States Court 
of Appeals for the 10th Circuit. Commenter BEPC noted that the 
representatives for the Laramie River Station are currently 
participating in good faith negotiations with the EPA aimed at reaching 
an agreement on the Regional Haze NOX controls for the 
source.
    Response: The EPA disagrees that it would be appropriate to wait 
until resolution of the legal challenges to the EPA's January 30, 2014 
partial approval and partial disapproval of Wyoming's Regional Haze SIP 
and the EPA's concurrent promulgation of a FIP (79 FR 5032) before 
acting on Wyoming's prong 2 SIP submission. The Regional Haze and 
interstate transport planning requirements address different air 
quality concerns and are addressed under different statutory provisions 
and timeframes. The Regional Haze requirements concern visibility in 
Class I areas, whereas the interstate transport requirements are 
concerned with attainment and maintenance of the NAAQS, which are 
designed to address public health and welfare. Thus, while actions 
taken to address one set of requirements may assist with meeting the 
other set of requirements, neither Wyoming nor the commenters have 
explained how implementation of either the disputed SIP or FIP 
requirements for Regional Haze would necessarily address the 
110(a)(2)(D)(i)(I) interstate transport requirements.
    Moreover, Wyoming's prong 2 SIP was submitted on February 6, 2014 
and was deemed complete by operation of law on August 7, 2014. 
Accordingly, CAA section 110(k)(2) requires the EPA to have taken final 
action to approve or disapprove a state's SIP within one year 
thereafter. As the EPA's action on this submission is already belated, 
the EPA does not find it appropriate to further delay action on the 
State's interstate transport SIP until there is resolution of 
litigation for an unrelated SIP requirement. Delaying action on the 
State's interstate transport SIP would only further delay potential 
emission reductions that may be necessary to address maintenance of the 
NAAQS in Denver, and thereby further delay the public health benefits 
that would accrue from such emission reductions. To the extent Wyoming 
believes that the NOX emission reductions that would be 
achieved through the State's implementation of the Regional Haze 
requirements will assist in meeting the State's interstate transport 
requirements, once the ongoing dispute is resolved, Wyoming may submit 
a revised SIP submission making an appropriate demonstration at that 
time.
    Comment: Commenter WDEQ disagrees with the EPA's basis for 
disapproving the State's SIP submission as to the prong 2 requirements 
for the 2008 ozone NAAQS, and believes its February 6, 2014 submittal 
contains the necessary information to meet these requirements. WDEQ 
asserted that it had relied upon the EPA's most recent guidance at the 
time that directly addressed the prong 1 and 2 requirements. WDEQ noted 
that the EPA's September 2013 infrastructure SIP guidance did not 
address the prongs 1 and 2 requirements, and therefore relied on prior 
guidance documents issued in 2006 and 2007 regarding reliance on the 
EPA's prior interstate transport rulemaking, CAIR, for purposes of 
developing interstate transport SIPs. \8\ WDEQ noted that these 
guidance documents state that a negative declaration from states not 
covered by CAIR certifying that the state meets prongs 1 and 2 is 
adequate to satisfy the requirements of CAA section 110(a)(2)(D)(i). 
WDEQ added that the guidance documents made no indication that the EPA 
expected states to consider contributions on days where downwind states 
measured an exceedance, neither in nonattainment nor maintenance areas. 
WDEQ contends that the EPA's proposed finding that WDEQ's analyses for 
prongs 1 and 2 are deficient because ``transported

[[Page 9145]]

emissions may cause an area to measure exceedances of the standard even 
if that area is not formally designated nonattainment by the EPA'' is 
unreasonable because such a showing was not stated as a requirement for 
approval. WDEQ also noted that the EPA previously approved Wyoming's 
ozone infrastructure plan which used the same methodology and approach 
used by the State in its February 6, 2014 submittal.
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    \8\ ``Guidance for State Implementation Plan (SIP) Submissions 
to Meet Current Outstanding Obligations Under Section 
110(a)(2)(D)(i) for the 8-Hour Ozone and PM2.5 NAAQS,'' 
August 15, 2006, and ``Guidance on SIP Elements Required Under 
Sections 110(a)(1) and (2) for the 1997 8-hour Ozone and 
PM2.5 National Ambient Air Quality Standards,'' October 
2, 2007.
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    WDEQ asserted that the EPA's proposed prong 2 disapproval indicates 
a radical change from its prior approach for determining adequacy of 
such plans. WDEQ asserted that the EPA has made statements indicating 
that the Agency has not evaluated the applicability of a transport rule 
in the western states, and that the EPA does not have an understanding 
of the nature of interstate ozone transport in the West. WDEQ suggested 
that the EPA should conduct interstate transport modeling and analysis 
specific to western states and then use the outcome of such analysis in 
the development and evaluation of future plans, but not plans 
previously submitted.
    Commenter Western Energy Alliance stated that the EPA's proposed 
action runs contrary to long-standing agency practice of accepting a 
``weight of evidence'' approach to evaluating interstate transport in 
downwind states, and contends that is inappropriate for the EPA to hold 
the WDEQ analysis to standards that did not exist when the SIP was 
developed.
    Response: For the reasons described at proposal and in this final 
action, the EPA disagrees that Wyoming's SIP submission contains 
adequate provisions to address the prong 2 requirements with respect to 
the 2008 ozone NAAQS. In particular, the State did not give the 
``interfere with maintenance'' clause of CAA section 110(a)(2)(D)(i)(I) 
independent significance, because its analysis did not attempt to 
evaluate the potential impact of Wyoming emissions on areas that may 
have issues maintaining that air quality, even if they currently 
measure clean data. As we noted at proposal, the EPA's most recent 
technical information demonstrates that emissions from Wyoming will 
impact air quality in other states relative to the 2008 ozone NAAQS.
    The EPA disagrees that it needed to issue guidance for states to be 
aware of the requirement to evaluate areas that might be at risk of 
violating the standard, regardless of whether those areas are or have 
been designated nonattainment. The court in North Carolina was 
specifically concerned with areas not designated nonattainment when it 
rejected the view that ``a state can never `interfere with maintenance' 
unless the EPA determines that at one point it `contribute[d] 
significantly to nonattainment.' '' 531 F.3d at 910. The court pointed 
out that areas barely attaining the standard due in part to emissions 
from upwind sources would have ``no recourse'' pursuant to such an 
interpretation. Id. Accordingly, and as described in the proposal, the 
court explained that the regulatory authority must give ``independent 
significance'' to the maintenance prong of CAA section 
110(a)(2)(D)(i)(I) by separately identifying such downwind areas for 
purposes of defining states' obligations pursuant to the good neighbor 
provision. Thus, the court's decision in North Carolina gave Wyoming 
sufficient notice, without further guidance from the EPA, that it 
needed to consider the potential impact of its emissions on areas that 
may have issues maintaining the standard. In addition, as noted at 
proposal, the EPA has stated in many actions before Wyoming made their 
submission that the obligation to address impacts on downwind air 
quality is independent of formal designations because exceedances can 
happen in any area.\9\ Wyoming's SIP submission did not attempt to 
evaluate such areas and was thus deficient as to the prong 2 
requirements. In so finding, the EPA is not engaged in a ``radical 
departure'' from its prior approach to evaluating SIPs, but merely 
measuring Wyoming's SIP against the statutory requirements, as 
interpreted by the court in North Carolina.\10\
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    \9\ The EPA notes that, in approving the state's SIP to address 
the requirements of section 110(a)(2)(D)(i)(I) with respect to the 
1997 ozone NAAQS, the EPA supplemented the State's technical 
analysis in order to ensure that that independent analysis was given 
to the prong 2 requirements. See 73 FR 26023, May 8, 2008.
    \10\ See, e.g., Clean Air Interstate Rule, 70 FR 25162, 25265 
(May 12, 2005) (``As to impacts, CAA section 110(a)(2)(D) refers 
only to prevention of `nonattainment' in other States, not to 
prevention of nonattainment in designated nonattainment areas or any 
similar formulation requiring that designations for downwind 
nonattainment areas must first have occurred.''); Cross-State Air 
Pollution Rule, 76 FR 48208, 48211 (Aug. 8, 2011) (evaluating 
nonattainment and maintenance concerns based on modeled 
projections); Brief for Respondents U.S. Environmental Protection 
Agency at 23-24, EME Homer City Generation, L.P. v. EPA, Case No. 
11- 1302 (D.C. Cir. Jan. 16, 2015), ECF No. 1532516 (defending the 
EPA's identification of air quality problems in CSAPR independent of 
area designations). Cf. Final Response to Petition from New Jersey 
Regarding SO2 Emissions From the Portland Generating 
Station, 76 FR 69052 (Nov. 7, 2011) (finding facility in violation 
of the prohibitions of CAA section 110(a)(2)(D)(i)(I) with respect 
to the 2010 SO2 NAAQS prior to issuance of designations 
for that standard). Thus, it was unnecessary for the EPA to issue 
formal guidance to alert states to its interpretation of CAA section 
110(a)(2)(D)(i)(I) requirements.
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    While EPA appreciates the helpful role guidance can provide to 
states, whether the EPA chooses to issue guidance or not does not 
relieve either states of the obligation to submit SIPs that address CAA 
section 110(a)(2)(D)(i)(I) by the statutory deadline or the EPA of the 
obligation to review SIPs consistent with those statutory requirements. 
States bear the primary responsibility to demonstrate that their plans 
contain adequate provisions to address the statutory interstate 
transport provisions, specifically to demonstrate that the plan 
properly prohibits emissions that will significantly contribute to 
nonattainment or interfere with maintenance of the NAAQS in downwind 
states. Furthermore, in EPA v. EME Homer City Generation, L.P., the 
Supreme Court clearly held that ``nothing in the statute places the EPA 
under an obligation to provide specific metrics to States before they 
undertake to fulfill their good neighbor obligations.'' 134 S. Ct. 
1584, 1601 (2014).\11\ While the EPA has taken a different approach in 
some prior rulemakings by providing states with an opportunity to 
submit a SIP after we quantified the states' emission reduction 
obligations (e.g., the NOX SIP Call and CAIR \12\), the CAA 
does not require such an approach. As discussed earlier, the EPA did 
provide information to assist states with developing or supplementing 
their SIP submittals for the 2008 ozone NAAQS, including the January 
22, 2015 memorandum providing preliminary modeling information 
regarding potential downwind air quality problems and levels of upwind 
state contributions and the August 4, 2015 NODA providing

[[Page 9146]]

updated modeling. All of these documents consistently indicated that 
the EPA's technical analysis showed that Wyoming emissions contribute 
to downwind air quality problems with respect to the 2008 ozone NAAQS; 
yet Wyoming did not revise or supplement its SIP submittal with 
additional data showing the State had satisfied its statutory 
obligation.\13\
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    \11\ ``Nothing in the Act differentiates the Good Neighbor 
Provision from the several other matters a State must address in its 
SIP. Rather, the statute speaks without reservation: Once a NAAQS 
has been issued, a State `shall' propose a SIP within three years, 
Sec.  7410(a)(1), and that SIP `shall' include, among other 
components, provisions adequate to satisfy the Good Neighbor 
Provision, Sec.  7410(a)(2).'' EPA v. EME Homer City Generation, 
L.P., 134 S. Ct. at 1600; see also Nat'l Ass'n of Mfrs. v. EPA, 750 
F.3d 921, (D.C. Cir. 2014) (``Finally, petitioners argue that EPA 
should not have issued, or at least should not require compliance 
with, the 2013 NAAQS without first providing States and regulated 
parties certain implementation guidance. We disagree. The NAAQS sets 
a clear numerical target specifying the maximum levels of emissions 
in the States. Under the law, States will devise implementation 
plans to meet that target. Nothing in the law dictates additional 
guidance from EPA at this point.'').
    \12\ For information on the NOX SIP call see 63 FR 
57356 (October 27, 1998). For information on CAIR (the Clean Air 
Interstate Rule) see 70 FR 25162 (May 12, 2005).
    \13\ The EPA does not agree that its statements explaining the 
EPA's intent to work with western states are an indication that the 
EPA does not have an understanding of interstate transport in the 
West. The EPA's statement that the EPA and the states should have a 
``common understanding of inter-state ozone transport in each part 
of the country'' was intended to indicate the Agency's desire to 
work with the states to develop appropriate solutions to interstate 
transport problems, not an indication that the EPA lacks an 
understanding of interstate transport in the West. As explained 
further below, the EPA believes the modeling provides a reliable 
projection of the nature of interstate transport in western states.
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    Moreover, it is inappropriate to rely on older EPA guidance to 
demonstrate compliance with the prong 2 requirements for the 2008 ozone 
NAAQS as those guidance documents do not address this specific NAAQS. 
Both the 2006 and 2007 guidance documents WDEQ claims to have relied on 
are inapplicable to the State's obligation to address the prong 2 
requirements for the 2008 ozone NAAQS. First, WDEQ concedes that both 
guidance documents were aimed at the addressing the prongs 1 and 2 
requirements for the 1997 ozone and fine particulate matter 
(PM2.5) NAAQS, not the 2008 ozone NAAQS at issue here. To 
the extent the guidance documents recommended relying on the analysis 
conducted to support the CAIR rulemaking, that rulemaking also only 
addressed the 1997 standards, and not the more stringent 2008 ozone 
NAAQS. The guidance documents in no way suggested that states could 
rely on the analysis from CAIR to address the prong 1 and 2 
requirements for any other NAAQS. Moreover, even were the CAIR analysis 
in some way relevant to the consideration of the 2008 ozone NAAQS, the 
EPA did not evaluate the impact of emissions from western states, 
including Wyoming, on air quality in the course of that rulemaking.\14\ 
Accordingly, there would be no basis on which either Wyoming or the EPA 
could conclude that the CAIR analysis supports a conclusion that 
Wyoming does not contribute significantly to nonattainment or interfere 
with maintenance either for the NAAQS explicitly addressed by CAIR or 
for any other NAAQS.\15\
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    \14\ See AQM TSD for CAIR final rule, at 3. WDEQ's citation to 
CSAPR is also unavailing. CSAPR also addressed only the 1997 ozone 
NAAQS, not the more stringent 2008 ozone NAAQS, and did not evaluate 
interstate transport as to any of these standards in western states, 
including Wyoming. 76 FR 48229 (describing modeling of states in the 
central and eastern U.S.). Accordingly, it would also be 
inappropriate for Wyoming to conclude that, because the state was 
not included in CSAPR, it does not significantly contribute to 
nonattainment or interfere with maintenance of the 2008 ozone NAAQS.
    \15\ Additionally, the 2006 guidance to which WDEQ points 
explicitly noted that any negative declaration indicating a state 
was not covered by CAIR should also be supported by a technical 
demonstration. See 2006 iSIP Guidance, p. 5.
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    More importantly, in North Carolina v. EPA, the D.C. Circuit held 
that CAIR was ``fundamentally flawed,'' 531 F.3d 896, 929 (D.C. Cir. 
2008), in part because CAIR did not satisfy the statutory requirement 
to ``achieve something measurable towards the goal of prohibiting 
sources `within the State' from contributing to nonattainment or 
interfering with maintenance in `any other State.' '' Id. at 908. The 
D.C. Circuit held in EME Homer City Generation, L.P. v. EPA, ``when our 
decision in North Carolina deemed CAIR to be an invalid effort to 
implement the requirements of the good neighbor provision, that ruling 
meant that the initial approval of the CAIR SIPs was in error at the 
time it was done.'' 795 F.3d 118, 133 (2015). States therefore did not 
need formal guidance to understand that it was no longer appropriate to 
rely on CAIR for purposes of satisfying the state's interstate 
transport obligations with respect to the 2008 ozone NAAQS, 
particularly when Wyoming submitted its SIP revision, six years after 
the North Carolina decision issued. Nonetheless, in a subsequent 
guidance document issued addressing the prong 1 and 2 requirements for 
the 2006 PM2.5 NAAQS, the EPA explicitly stated that states 
should no longer rely on CAIR as a means of addressing the interstate 
transport requirements because the rule had been remanded by the court 
in North Carolina.\16\
---------------------------------------------------------------------------

    \16\ Memo from William T. Harnett to Regional Air Division 
Directors, Regions I-X, ``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)'' 
(Sept. 25, 2009), p. 3. Notably, this guidance document explicitly 
stated as to the prong 2 requirements, ``This provision requires 
evaluation of impacts on areas of other states that are meeting the 
2006 24-hour PM2.5 NAAQS, not merely areas formerly 
designated nonattainment that are subject to a maintenance SIP. 
Therefore, the state's submission must explain whether or not 
emissions from the state have this impact and, if so, address the 
impact.'' Id. p. 3-4. The EPA continued by providing specific 
factors a state could consider: ``A state's submission for this 
requirement should provide the technical information which the state 
deems appropriate to support its conclusions. Suitable information 
might include, but is not limited to, information concerning 
emissions in the state, meteorological conditions in the state and 
the potentially impacted states, monitored ambient concentrations in 
the state and the potentially impacted states, and air quality 
modeling.'' Id. p. 4.
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    Although WDEQ questions how it could have developed an approvable 
SIP without explicit guidance from the EPA and before the EPA had 
conducted air quality modeling evaluating downwind air quality and 
contributions, as explained earlier, states bear the primary 
responsibility for demonstrating that their plans contain adequate 
provisions to address the statutory interstate transport provisions 
whether or not the EPA issues such guidance or conducts such modeling. 
The commenters are correct to note that, in separate interstate 
transport actions, the EPA has reviewed and finalized action on 
interstate transport SIPs in states where air quality modeling was not 
available or where the total weight of evidence for finalizing action 
on the state's SIP was not solely based on air quality modeling.\17\ As 
evidenced by these actions, consideration of monitoring data and wind 
patterns, properly used, can be relevant to evaluating potential 
interstate transport impacts, but such consideration does not absolve a 
state from evaluating its downwind impact regardless of formal area 
designations and considering the requirements of both prongs of the 
good neighbor provision. A state can and should submit all of the 
technical information it considers relevant to evaluate its 
contribution to downwind air quality, including anticipated changes in 
the emissions from sources within the state and any additional factors 
specific to the state that influence its emissions and air pollution 
which may transport to other states. As we noted above and as found by 
the Supreme Court in EME Homer City Generation, L.P., the lack of 
guidance does not relieve either the states of the obligation to submit 
SIPs that address CAA section 110(a)(2)(D)(i)(I) nor the EPA of the 
obligation to review such SIPs consistent with the statutory 
requirements of the good neighbor provision. Though Wyoming submitted

[[Page 9147]]

a technical analysis that considers certain factors which align with 
the EPA's actions on prior SIP submissions, the EPA could not conclude 
based on this analysis that the State is not interfering with 
maintenance of the NAAQS in other states, particularly in light of air 
quality modeling demonstrating that emissions from Wyoming impact air 
quality in Denver, Colorado. The basis for this conclusion was 
explained in the proposal for this final action.
---------------------------------------------------------------------------

    \17\ See, e.g., Air Quality State Implementation Plans; 
Approvals and Promulgations: Utah; Interstate Transport of Pollution 
for the 2006 PM2.5 NAAQS May 20, 2013 (78 FR 29314); 
Final Rule, 78 FR 48615 (August 9, 2013); Approval and Promulgation 
of Implementation Plans; State of California; Interstate Transport 
of Pollution; Significant Contribution to Nonattainment and 
Interference With Maintenance Requirements, Proposed Rule, 76 FR 
146516, 14616-14626 (March 17, 2011); Final Rule, 76 FR 34872 (June 
15, 2011); Approval and Promulgation of State Implementation Plans; 
State of Colorado; Interstate Transport of Pollution for the 2006 
24-Hour PM2.5 NAAQS, Proposed Rule, 80 FR 27121, 27124-
27125 (May 12, 2015); Final Rule, 80 FR 47862 (August 10, 2015).
---------------------------------------------------------------------------

    Comment: Commenter WDEQ stated that the EPA is applying new 
criteria retroactively. WDEQ asserted that the EPA had not established 
any technical requirements for demonstrating impacts on nearby states 
at the time of Wyoming's February 6, 2014 submission, but then 
retroactively applied ``a technical analysis developed almost three 
years after Wyoming's submittal to evaluate Wyoming's plan.'' The State 
submitted a timeline to argue that the EPA's proposed action is out of 
sequence with appropriate rulemakings. Commenter WDEQ noted that it had 
commented on the EPA's August 4, 2015 NODA, ``stating that it 
understood that the rule applied only to eastern states and would 
provide additional comments when the EPA proposed additional SIP 
requirements for western states.'' Wyoming asserted that the EPA did 
not provide a response to this comment. Finally, WDEQ stated that the 
EPA failed to indicate that a revision to submitted plans might be 
required, as it had done in its October 2, 2007 guidance document.
    Response: As discussed previously, the EPA's primary basis for 
disapproving Wyoming's prong 2 SIP submission as to the 2008 ozone 
NAAQS is based on the State not giving the ``interfere with 
maintenance'' clause of CAA section 110(a)(2)(D)(i)(I) independent 
significance as required by North Carolina, a decision which was issued 
six years before Wyoming submitted the SIP at issue here. The EPA also 
has technical information demonstrating that emissions from Wyoming 
impact a downwind maintenance receptor in Denver, Colorado, but even 
absent this information, the State did not provide an adequate 
technical analysis meeting the basic statutory requirements outlined by 
the D.C. Circuit and supporting its conclusion.
    Wyoming is correct to note that the EPA stated the CSAPR Update 
does not apply to Wyoming, and the final CSAPR Update does not impose 
any implementation obligations on the state of Wyoming or sources 
within the State. 81 FR 74523, October 26, 2016. However, in the 
context of that rulemaking, the EPA developed technical information 
relevant to western states, including Wyoming, while in this final 
action on the Wyoming SIP the EPA is adopting an approach to analyzing 
that data as it applies to Wyoming. While the modeling cited in this 
action was conducted after Wyoming submitted its SIP addressing the 
requirements of CAA section 110(a)(2)(D)(i)(I) for the 2008 ozone 
NAAQS, it would not be appropriate for the EPA to ignore modeling data 
indicating that the emissions from the State would impact air quality 
in other states. Rather, the EPA must evaluate each SIP submission 
based on the information available and consistent with the Act as we 
and courts interpret it at the time of our action, not at the time of 
the state's submittal. Wyoming was aware that the EPA had data 
indicating a potential impact as early as January 2015, but did not 
submit additional information to supplement or revise its SIP 
submission addressing CAA section 110(a)(2)(D)(i)(I) requirements for 
the 2008 ozone NAAQS.\18\ Wyoming also had an opportunity to review the 
modeling information in the context of the EPA's proposed action on the 
SIP submission, and could comment on the appropriateness of using the 
modeling for this purpose, and how the EPA should interpret the 
modeling results as they apply to Wyoming, which both Wyoming and a 
number of other commenters have done. The EPA addresses those specific 
comments regarding the EPA's technical analysis below.
---------------------------------------------------------------------------

    \18\ The EPA explained in issuing the January 2015 memo that its 
``goal is to provide information and to initiate discussions that 
inform state development and EPA review of `Good Neighbor' SIPs, 
and, where appropriate, to facilitate state efforts to supplement or 
resubmit their `Good Neighbor' SIPs,'' at 1. With respect to western 
states, the EPA indicated it would evaluate potential linkages on a 
case-by-case basis and recommended that states consult with the EPA 
regional offices. Id. at 4.
---------------------------------------------------------------------------

    Comment: Commenter WDEQ stated that the EPA's use of CSAPR Update 
modeling as a screening tool is not appropriate for interstate 
transport in the West, citing its June 9, 2016 comment letter opposing 
the EPA's proposed action for Utah. Commenters UARG, WEST Associates, 
and BEPC also referenced or attached comment letters submitted on the 
CSAPR Update proposal.\19\
---------------------------------------------------------------------------

    \19\ These comment letters can be found in the docket for the 
CSAPR Update, EPA-HQ-OAR-2015-0500.
---------------------------------------------------------------------------

    Response: Commenters should identify with reasonable specificity 
any objections or issues with the proposed action rather than only 
referring or citing to comments made in other contexts. It is not 
appropriate to cite to or attach comments made on separate rulemaking 
actions without identifying which portions of such comments are 
relevant to the present proposed action. Accordingly, the EPA is not 
here responding to comments made on separate rulemaking actions.
    Comment: Commenter Western Energy Alliance stated that the CSAPR 
Update modeling results are flawed because the model has not been 
adapted to the unique concerns of western states. The commenter stated 
that ``the CSAPR model fails to account for the topography, altitude, 
and climate of the western United States. Climate factors 
characteristic of the West include stratospheric intrusions, a long and 
severe wildfire season, abundant sunshine, and lack of summertime 
precipitation, all of which the CSAPR model fails to adequately 
consider.'' The commenter asserted that the EPA did not provide 
evidence explaining why the modeling results need not consider these 
factors. Finally, the commenter stated that the EPA inappropriately put 
the onus on the State to provide evidence to support or deny the EPA's 
decisions on the appropriateness of the CSAPR modeling, while the 
burden should rest on the EPA to justify the reversal of its long-
standing policy about the CSAPR modeling deficiencies in the West.
    Commenter WEST Associates stated that the EPA had noted in the 
CSAPR Update proposal that the modeling for that rule was conducted 
specifically for Eastern states. The commenter also referenced language 
from the CSAPR Update and the Wyoming proposal in which the EPA stated 
that there may be geographically specific factors to consider in 
evaluating ozone transport in the West affecting modeling and modeling 
results. Citing 81 FR 81715, November 18, 2016. The commenter suggested 
that these factors could include broad expanses of public land, high 
altitude settings, international transport and elevated background 
ozone concentrations that can comprise a significant portion of ambient 
concentrations, especially on high ozone days in the Western United 
States.
    Response: The commenters do not provide evidence or technical bases 
for their claims about the inadequacies of the modeling for projecting 
air quality and contributions in the West. As described in the CSAPR 
Update Final Air Quality Modeling Technical

[[Page 9148]]

Support Document (2016 AQM TSD),\20\ the CSAPR modeling was performed 
for a nationwide domain that accounted for the differences in emissions 
(including actual wild fires), meteorology, and topography in various 
regions across the U.S. The precipitation and other meteorological 
factors used in the EPA's modeling were found to correspond closely to 
measured data.\21\ The 2016 AQM TSD includes an evaluation of 2011 base 
year model performance for 8-hour daily maximum concentrations on a 
regional and statewide basis as well as for individual monitoring 
sites. For example, the performance evaluation results for Wyoming 
indicate that the model tends to under predict measured 8-hour daily 
maximum ozone concentrations by 10.3 percent, on average, during the 
period May through September, which is the season the EPA used for 
analyzing 2017 model-predicted interstate contributions. For the 
Douglas County maintenance receptor in Colorado, the 2011 modeling 
under predicts measured 8-hour daily maximum ozone concentrations by 
7.5 percent, on average for the May through September time period. As 
described more fully in the 2016 AQM TSD, the EPA's use of the 
Comprehensive Air Quality Model with Extensions (CAMx) source 
apportionment modeling for the CSAPR Update is appropriate and the 
Agency finds its use sufficient for the purposes of assessing and 
identifying downwind air quality problems and contributions from upwind 
states in both the eastern and the western U.S.\22\ The emissions 
modeling TSD for the CSAPR Update final rule ``Preparation of Emission 
Inventories for the version 6.3, 2011 Emissions Modeling Platform'' 
describes how fire emissions were developed and modeled using a 
consistent approach for the contiguous United States. As described 
earlier, the most updated modeling continues to indicate that emissions 
from Wyoming will interfere with maintenance of the 2008 ozone NAAQS at 
one receptor in the Denver, Colorado area (i.e., Douglas County).
---------------------------------------------------------------------------

    \20\ ``Air Quality Modeling Technical Support Document for the 
Final Cross State Air Pollution Rule Update.'' August 2016. This 
document was included in the docket for the proposed action.
    \21\ ``Meteorological Model Performance for Annual 2011 
Simulation WRF v3.4'' in the docket for the CSAPR Update Rulemaking, 
at EPA-HQ-OAR-2015-0500-0076.
    \22\ ``The EPA used CAMx photochemical source apportionment 
modeling to quantify the impact of emissions in specific upwind 
states on downwind nonattainment and maintenance receptors for 8-
hour ozone. CAMx employs enhanced source apportionment techniques 
that track the formation and transport of ozone from specific 
emissions sources and calculates the contribution of sources and 
precursors to ozone for individual receptor locations. The strength 
of the photochemical model source apportionment technique is that 
all modeled ozone at a given receptor location in the modeling 
domain is tracked back to specific sources of emissions and boundary 
conditions to fully characterize culpable sources.'' 80 FR 75726, 
December 3, 2015.
---------------------------------------------------------------------------

    The EPA does not find the information provided by the commenters to 
indicate flaws in the modeling conducted by the EPA. Rather, the 
commenters point to factors which the CSAPR Update modeling 
specifically took into account.\23\ As described in the CAMx model 
User's Guide, ``CAMx is an Eulerian photochemical dispersion model that 
allows for integrated ``one-atmosphere'' assessments of tropospheric 
air pollution (ozone, particulates, air toxics, and mercury) over 
spatial scales ranging from neighborhoods to continents. It is designed 
to unify all of the technical features required of ``state-of-the-
science'' air quality models into a single open-source system that is 
computationally efficient, flexible, and publicly available.'' \24\ For 
these reasons, the EPA disagrees with these comments and finds the use 
of the CSAPR Update modeling to evaluate Wyoming's contributions to 
interstate transport is reasonable and supported.
---------------------------------------------------------------------------

    \23\ Stratospheric intrusions are short-term events that have a 
relatively local impact on ground-level ozone concentrations and are 
unrelated to the impacts of interstate transport on downwind ozone 
formed from anthropogenic sources in upwind states. The modeling 
performed by the EPA did not explicitly account for these events 
within the modeling domain. However, the global modeling EPA used to 
provide boundary concentrations that reflect international transport 
into the domain did simulate processes that can result in 
stratospheric intrusions.
    \24\ User's Guide Comprehensive Air Quality Model with 
Extensions version 6.2. Environ International Corporation, Novato, 
CA, March, 2015.
---------------------------------------------------------------------------

    The EPA did acknowledge in the CSAPR Update final rule that ``for 
western states, there may be geographically specific factors to 
consider in evaluating interstate ozone pollution transport,'' and that 
``given the near-term 2017 analysis and implementation of the CSAPR 
Update FIPs, the EPA focused this rulemaking on eastern states where 
the CSAPR method for assessing collective contribution has proven 
effective.'' 81 FR 74523, October 26, 2016. However, these statements 
were not an indication that the EPA believed the modeling of air 
quality in the West was flawed. Rather, the EPA was suggesting that 
additional factors may be relevant in determining whether an upwind 
state that was projected to impact air quality in a downwind state 
should be determined to significantly contribute to nonattainment or 
interfere with maintenance of the NAAQS in that state. The EPA's recent 
action approving Arizona's interstate transport SIP, discussed in more 
detail at proposal, demonstrates some of the geographically specific 
factors that the EPA was referring to with these statements. See 
Proposed Rule, 81 FR 15202, March 22, 2016; Final Rule, 81 FR 31513, 
May 19, 2016.\25\
---------------------------------------------------------------------------

    \25\ See also Notice of Availability of the Environmental 
Protection Agency's Preliminary Interstate Ozone Transport Modeling 
Data for the 2015 Ozone National Ambient Air Quality Standard 
(NAAQS), 82 FR 1740 (January 6, 2017): ``While the 1 percent 
screening threshold has been traditionally applied to evaluate 
upwind state linkages in eastern states where such collective 
contribution was identified, the EPA noted in the CSAPR Update that, 
as to western states, there may be geographically specific factors 
to consider in determining whether the 1 percent screening threshold 
is appropriate. For certain receptors, where the collective 
contribution of emissions from one or more upwind states may not be 
a considerable portion of the ozone concentration at the downwind 
receptor, the EPA and states have considered, and could continue to 
consider, other factors to evaluate those states' planning 
obligation pursuant to the Good Neighbor provision. However, where 
the collective contribution of emissions from one or more upwind 
states is responsible for a considerable portion of the downwind air 
quality problem, the CSAPR framework treats a contribution from an 
individual state at or above 1 percent of the NAAQS as significant, 
and this reasoning applies regardless of where the receptor is 
geographically located.''
---------------------------------------------------------------------------

    Comment: Commenter Western Energy Alliance stated that it is 
unclear whether the CSAPR Update modeling accounted for background 
ozone, which can contribute up to 60 ppb in the western U.S. Commenters 
West Associates and BEPC also note that approximately half of the ozone 
measured at the Denver monitor is from background ozone. These 
commenters suggest that this presents ``nearly identical'' facts to the 
grounds used to propose approval of Nevada's interstate transport SIP 
for the 2008 ozone NAAQS. 81 FR 87859, December 6, 2016.
    Response: The commenters do not explain how the EPA's modeling has 
allegedly failed to account for background ozone. This modeling 
includes emissions from biogenic sources which are a major component of 
natural background ozone that is particularly relevant to summertime 
high ozone concentrations. The modeling also includes emissions from 
large portions of Canada and Mexico that are adjacent to the U.S. 
within the modeling domain. Background ozone due to transport from more 
distant international sources was accounted for by the use of global 
air quality modeling to provide ozone and precursor concentrations 
along the boundary of the modeling domain. The commenters

[[Page 9149]]

have not explained how they believe the EPA must consider background 
ozone levels in evaluating interstate transport in the West, nor cited 
any specific provision of the statute that specifically requires such 
consideration. While the EPA does not view the obligation under the 
good neighbor provision as a requirement for upwind states to bear all 
of the burden for resolving downwind air quality problems, the CAA 
requires that upwind states (as well as the downwind states themselves) 
take reasonable steps to control emissions impacting downwind air 
quality even in areas affected by high levels of background 
concentrations of ozone. Were the EPA to absolve upwind states of the 
responsibility to make such reasonable reductions simply because of 
such background ozone concentrations, the area's citizens would suffer 
the health and environmental consequences of such inaction.
    Moreover, the EPA does not agree that, because background ozone 
contributes to the projected design values at the Denver monitor, the 
factual circumstances are ``nearly identical'' to the circumstances 
supporting the proposed approval of the Nevada SIP. In fact, the 
circumstances here are substantially different than the facts 
considered in the Nevada SIP approval. The EPA proposed to approve 
Nevada's SIP submission because, among other factors, it determined 
that the cumulative contribution from upwind states to the downwind 
receptors to which Nevada was linked (all of which were located in 
California) was low relative to the cumulative contribution to air 
quality problems similarly identified elsewhere in the country and 
because Nevada was the only state contributing above the one percent 
threshold to those receptors. 81 FR 87860, Dec. 6, 2016. Because the 
EPA determined that emissions that result in transported ozone from 
upwind states have limited impacts on the projected air quality 
problems at the California receptors, the EPA proposed to determine 
that the sites should not be treated as receptors for purposes of 
determining interstate transport obligations. Id. This is in contrast 
to the air quality problem identified at the Denver receptor wherein 
the EPA determined that a significant portion of the ozone 
concentration was attributable to the collective contribution from 
anthropogenic emissions in multiple states, three of which contribute 
at or above the one percent screening threshold. 81 FR 81714 through 
81715, December 6, 2016. The Denver receptor is comparable to receptors 
the EPA has addressed in the East in rulemakings such as the CSAPR 
Update wherein the EPA determined that downwind air quality problems 
resulted in part from the contributions of multiple upwind states that, 
although individually relatively small, collectively contribute a large 
portion of the ozone concentration at downwind receptors. See 81 FR 
74518-19.\26\
---------------------------------------------------------------------------

    \26\ The EPA's analysis showed, for example, that upwind states 
collectively contributed in the range of 9.7% to 12.6% to the total 
ozone concentrations for receptors in Denton County, Harris County, 
and Tarrant County, Texas. This range is similar to the collective 
contribution at the Douglas County receptor in Colorado. See 
document EPA-R08-OAR-2016-0521-0002, ``Final CSAPR Update_Ozone 
Design Values & Contributions_All Sites,'' in the docket for this 
action.
---------------------------------------------------------------------------

    Moreover, consistent with the EPA's approach to background 
concentrations in this action, the EPA disagreed with Nevada's 
contention that background concentrations should necessarily excuse an 
upwind state from reducing emissions where such emissions reductions 
may nonetheless improve downwind air quality. 81 FR 87860. The EPA 
noted that even areas with high background ozone may still have a 
relatively large amount of ozone from the collective contribution of 
upwind U.S. emissions. Id. Therefore, regardless of the level of 
background ozone, emissions reductions from upwind states may be an 
important component of solving the local nonattainment problem.
    Comment: Commenter WDEQ stated that the EPA's decisions on 
interstate transport SIPs do not follow a consistent approach, and that 
the EPA is applying a piecemeal decision-making approach rather than a 
systematic analysis. WDEQ also asserted that the EPA is making 
arbitrary decisions as to what constitutes ``significant'' or 
``insignificant'' contribution levels. WDEQ asserted that the EPA is 
not applying the one percent threshold as a screening threshold, as 
stated in the proposal. Referring to the EPA's October 19, 2016 final 
action on the Utah interstate transport SIP (81 FR 71991), WDEQ argued 
that the EPA gave no consideration to information submitted by Utah in 
its analysis beyond the one percent contribution. WDEQ further stated 
that the EPA approved the Colorado interstate transport submittal which 
otherwise ``did not provide a detailed analysis supporting its 
conclusion, including any quantification of the distance to other 
nonattainment areas or the amount of ozone emission reductions within 
the state and over what timeframe,'' solely because it was modeled 
below the one percent contribution threshold. 80 FR 72939, November 23, 
2015. WDEQ also asserted that the Colorado approval is counter to the 
EPA actions disapproving plans from western states on the basis that 
they did not provide enough technical analysis.
    WDEQ further asserted that the approval of the Arizona interstate 
transport SIP for 2008 ozone was inconsistent with the proposed action 
on Wyoming, because the EPA based its Arizona action on a weight of 
evidence analysis and a determination that Arizona's contribution was 
``negligible'' although it was over the one percent threshold. The 
State also asked the EPA to explain why it determined the cumulative 
contribution percentages for Arizona were negligible, and at what 
percentage such contributions became negligible.
    Response: The EPA disagrees that it has taken an inconsistent 
approach to reviewing states' interstate transport SIPs with respect to 
the 2008 ozone NAAQS. Where the EPA has determined that a state's SIP 
has not addressed all of the statutory requirements or provided a 
technical analysis to justify its conclusion regarding the state's 
impact on downwind air quality problems, the EPA has identified those 
deficiencies in acting upon the state's SIP submission. Where the EPA 
had analysis available that nonetheless supported the state's 
conclusion despite these deficiencies in the state's SIP submission, 
the EPA has proposed to approve the state's SIP submission, as it did 
with Colorado. However, where the EPA does not have its own analysis to 
support a state's conclusion, it does not have a basis to nonetheless 
approve the state's otherwise deficient SIP submission, as in Utah for 
prong 2. Accordingly, the EPA is in this rule finalizing approval as to 
Wyoming's otherwise deficient prong 1 demonstration because the EPA has 
an independent analysis that supports the conclusion that the state 
does not significantly contribute to nonattainment downwind. However, 
the EPA cannot approve Wyoming's deficient prong 2 demonstration 
because it has no independent basis on which it can conclude that the 
state does not interfere with maintenance of the 2008 ozone NAAQS 
downwind.
    The EPA furthermore disagrees that it is not using the one percent 
contribution threshold as a screening threshold. States are not 
determined to significantly contribute to nonattainment or interfere 
with maintenance downwind merely because impacts from the state exceed 
the one percent threshold. As noted in the proposal for this final 
action, the one

[[Page 9150]]

percent threshold identifies a state as ``linked,'' prompting further 
inquiry into whether the contributions are significant and whether 
there are cost-effective controls that can be employed to reduce 
emissions. In the case of Colorado, as it was determined that state was 
not linked to any downwind nonattainment or maintenance receptors, 
further inquiry was unnecessary in spite of deficiencies identified 
with the Colorado transport analysis. In the case of states like 
Wyoming and Utah, the linkage to Denver area receptors indicated that 
each state's emissions require further evaluation, taking into account 
both air quality and cost considerations, to determine what, if any, 
emissions reductions might be necessary to address the states' emission 
reduction obligation pursuant to 110(a)(2)(D)(i)(I). As Wyoming's SIP 
submission does not adequately evaluate whether additional emissions 
reductions are necessary or achievable, the EPA could not conclude that 
the State's SIP submission had demonstrated that the state prohibits 
emissions that interfere with maintenance of the NAAQS downwind.
    With regard to the EPA's action on the Arizona submittal, the EPA 
found that the maximum total contribution from anthropogenic emissions 
in all states to either of the two California receptors to which 
Arizona contributed above the one percent threshold was 4.4 percent of 
the total ozone concentration at that receptor, and that only one state 
contributed above the one percent threshold. 81 FR 15203, March 22, 
2016. Thus, the EPA determined that, unlike receptors identified in 
prior rulemakings, the air quality problems at the California receptors 
could not be attributed to the collective contribution of numerous 
upwind states. Given this information, the EPA determined that 
interstate transport to the California receptors is negligible overall, 
meaning that all states together (including Arizona) do not contribute 
significantly to the ozone problems at these receptors. Because the EPA 
determined that emissions that result in transported ozone from upwind 
states have limited impacts on the projected air quality problems at 
the California receptors, the EPA determined that the sites should not 
be treated as receptors for purposes of determining interstate 
transport obligations. Id. As stated in the proposal for this final 
action, EPA found that the contribution to ozone concentrations from 
all states upwind of the Douglas County, Colorado maintenance receptor 
is about 9.7 percent, and that three upwind states made contributions 
greater than one percent to the receptor. 81 FR 81715, November 18, 
2016. The EPA has not defined a specific level which delineates between 
``negligible'' and ``significant'' collective contribution, but has 
rather looked at each of these cases individually and reached 
conclusions based on our review of the information specific to each 
case. In the case of the Douglas County, Colorado receptor, the 
contributions from upwind states are comparable to receptors the EPA 
has addressed in the East in rulemakings such as the CSAPR Update 
wherein the EPA determined that downwind air quality problems resulted 
in part from the relatively small individual contributions of upwind 
states that collectively contribute a large portion of the ozone 
concentration at downwind receptors. See 81 FR 74518 through 74519.\27\ 
Thus, the EPA has identified no basis on which it can distinguish the 
Douglas County, Colorado receptor from those receptors addressed in the 
East--nor have the commenters presented any such basis for the EPA to 
make a distinction when upwind states contribute more than twice as 
much to downwind nonattainment than was present at the California 
receptors addressed in the Arizona action.
---------------------------------------------------------------------------

    \27\ The EPA's analysis showed, for example, that upwind states 
collectively contributed in the range of 9.7% to 12.6% to the total 
ozone concentrations for receptors in Denton County, Harris County, 
and Tarrant County, Texas. This range is similar to the collective 
contribution at the Douglas County receptor in Colorado. See 
document EPA-R08-OAR-2016-0521-0002, ``Final CSAPR Update_Ozone 
Design Values & Contributions_All Sites,'' in the docket for this 
action.
---------------------------------------------------------------------------

    Comment: Commenter WDEQ stated that the EPA's analysis does not 
consider new emissions information or reductions since the most recent 
modeling. The State asserted that because the EPA conducted the CSAPR 
Update modeling using an emissions inventory from a 2011 base year, the 
analysis fails to account for any emissions reductions in Wyoming 
between 2011 and when the updated modeling was conducted. WDEQ 
specifically pointed to the following ozone emissions reduction 
measures in the State: Participation in the EPA's Ozone Advance 
Program; emissions reductions in the Upper Green River Basin (UGRB), a 
marginal nonattainment area which was determined by the EPA to have 
timely attained the 2008 Ozone NAAQS on May 4, 2016 (81 FR 26697); 
reductions in NOX emissions from 2011 and 2014 of 34 percent 
for Title V facilities and 76 percent for non-Title V facilities that 
are not oil and gas reductions facilities. The State ``believes a more 
accurate assessment of Wyoming's contribution to the receptor in 
Colorado could be made using more recent emission inventory data 
available from the Division,'' and asked that the EPA use more recent 
data to conduct modeling for Wyoming.
    The State asserted that it had made several attempts to provide the 
EPA with additional information, citing its November 23, 2016 letter 
requesting an extension to the comment period as an example, and 
claimed that the EPA has told Wyoming it will not consider any 
additional information beyond the February 6, 2014 submission.
    Response: The EPA disagrees that the CSAPR Update modeling failed 
to account for any emissions reductions in Wyoming between 2011 and 
2016, despite the use of a 2011 base year. As shown in the supporting 
documentation for the CSAPR Update Rule, significant emissions 
reductions for multiple pollutants, including NOX, were 
accounted for in the modeling analysis.\28\ At the EPA's request, on 
September 13, 2016 and September 14, 2016, the State submitted to the 
EPA an emissions inventory and an inventory summary that compared 2011 
to 2014 Wyoming NOX and VOC emissions.\29\ The State also 
included two graphs describing Wyoming NOX and VOC emission 
reductions in certain sectors in its December 19, 2016 comment letter 
on the proposal for this final action. EPA staff compared this 
information to the emissions reductions anticipated from base case year 
2011 to projected future year 2017 in the CSAPR Update Modeling, and 
found that NOX and VOC emissions reductions included in the 
CSAPR Update modeling were greater than the NOX and VOC 
reductions in Wyoming emissions from 2011 to 2014, per the State's 
inventory.\30\ The EPA does not dispute that NOX emission 
reductions have taken place in Wyoming between 2011 and 2014, as the 
inventory and the December 19, 2016 comment letter graphs indicate 
substantial reductions have occurred in certain sectors. However, the 
inventory

[[Page 9151]]

taken on its own did not lead the EPA to the conclusion that the 
NOX reductions during this time were sufficient to show that 
Wyoming does not interfere with maintenance of the 2008 ozone NAAQS. In 
other words, the information was inconclusive, and so did not alter the 
EPA's decision to propose disapproval for prong 2. The EPA has reached 
the same conclusion regarding the comment letter graphs, and is 
therefore finalizing disapproval as to the prong 2 requirements.
---------------------------------------------------------------------------

    \28\ ``Final Rule Emissions Modeling TSD: Preparation of 
Emissions Inventories for the Version 6.3, 2011 Emissions Modeling 
Platform'' in the docket for the CSAPR Update Rulemaking, at EPA-HQ-
OAR-2015-0500-0523.
    \29\ See September 12-14, 2016 email exchanges between Adam 
Clark, EPA Region 8, and Amber Potts and Tyler Ward, WDEQ, as well 
as attached emissions inventory documents submitted by the State, in 
the docket for this action.
    \30\ See document ``2011ek_2017ek_state_full_SCC_summary'' in 
the docket for this action. This document is also available in the 
docket for the CSAPR Update Rulemaking at EPA-HQ-OAR-2015-0500-0498.
---------------------------------------------------------------------------

    The EPA also disagrees that the State made several attempts to 
provide EPA with additional information. The State submitted the 
aforementioned September 13, 2016 inventory, which the EPA reviewed. 
The State also submitted the June 9, 2016 comment letter on the Utah 
proposal as discussed previously, and the November 23, 2016 letter 
requesting an extension to the comment period. The EPA has reviewed and 
addressed all of these documents. Finally, the EPA is unaware that any 
staff told Wyoming that we will not consider any additional information 
beyond the February 6, 2014 submission. The EPA has continuously 
encouraged the State to submit additional technical information that 
might better inform our analysis, as discussed in detail earlier.
    Comment: Commenter WDEQ asked whether the EPA's CSAPR Update 
modeling considered the impact ozone sources in the Colorado portion of 
the Front Range Urban Corridor, which extends from Pueblo, Colorado to 
Cheyenne, Wyoming, may have on attainment in Wyoming. The State then 
asserted that, because 98 percent of the population in this corridor 
resides in Colorado, and because the population in the Colorado portion 
of the corridor is much larger and denser than the population of the 
state of Wyoming, the mobile source and urban emissions emanating from 
Colorado are far more likely to contribute to Wyoming than the other 
way around.
    Commenter Western Energy Alliance stated that Colorado's ozone 
nonattainment is affected by the northern Front Range's climate, 
geography, and local emissions sources, and not by Wyoming emissions. 
The commenter supported Wyoming's assessment that the year-round 
westerly prevailing wind direction makes it reasonable to infer that 
Cheyenne is not a driving cause of ozone nonattainment in Colorado's 
Front Range.
    Commenter Western Energy Alliance also asserted that Wyoming is not 
contributing to ozone nonattainment in the Uintah Basin or in the Salt 
Lake Valley in Utah.
    Response: In the CSAPR Update modeling, the EPA modeled 
contributions from all 48 contiguous states, including Colorado, to 
receptors in Wyoming. As the EPA did not project any nonattainment or 
maintenance receptors in the state of Wyoming for 2017, the EPA has 
determined that no state contributes significantly to nonattainment or 
interferes with maintenance of the 2008 ozone NAAQS in Wyoming. The EPA 
approved prongs 1 and 2 of Colorado's 2008 ozone interstate transport 
SIP on February 16, 2016. 81 FR 7706. The EPA did not receive any 
comments requesting that either portion of the Colorado SIP submission 
be disapproved.
    The EPA agrees that Colorado emissions contribute more to ozone 
pollution in the Denver area than emissions from any other state. 
Indeed, the CSAPR Update modeling projected that Colorado would 
contribute 34.6% percent of the ozone at the Douglas County, Colorado 
maintenance receptor in 2017, compared to 9.7 percent of the emissions 
from all other states and tribes combined, with Wyoming projected to 
contribute 1.5 percent of the ozone. Although there are intrastate 
contributions to maintenance receptors in Denver, Colorado, those 
contributions do not relieve upwind states, like Wyoming, from 
controlling their within state emissions that significantly contribute 
to a downwind state's nonattainment or interfere with maintenance of 
the NAAQS in other states.
    Thus, while CAA section 110(a)(2)(D)(i)(I) does not hold upwind 
areas solely responsible for attainment and maintenance of the NAAQS in 
downwind states, the statute requires upwind states to address their 
fair share of downwind air quality problems. As noted, the EPA finds 
that Wyoming contributions to the Douglas County, Colorado maintenance 
receptor are such that the State's emissions require further evaluation 
of potential emission reduction obligations pursuant to 
110(a)(2)(D)(i)(I).
    Regarding Wyoming's contribution to ozone issues in Utah, the EPA 
has not found that Wyoming emissions contribute significantly to 
nonattainment or interfere with maintenance of the 2008 ozone NAAQS in 
Utah.
    Comment: Commenter WDEQ asserted that ``EPA has not yet worked with 
western states or western regional planning organizations on region-
appropriate analysis for interstate transport.'' The State listed 
examples in which the EPA committed to working with western states to 
address interstate transport.
    Commenter WDEQ requested that the EPA honor the commitment made in 
the Utah Final Rulemaking to ``assisting the states in conducting or 
reviewing air quality modeling and other relevant technical information 
for the purposes of determining compliance with CAA section 
110(a)(2)(D)(i)(I).'' 81 FR 71996, October 19, 2016. Specifically, the 
State requested that the EPA commit to work with WDEQ to conduct the 
necessary modeling and analysis for developing a SIP revision in the 
event that the EPA finalizes the proposed disapproval.
    Response: Prior to the State's February 2014 SIP submission, the 
EPA held a meeting in Denver, Colorado on April 17, 2013 (and held a 
conference call) with western states to discuss next steps to address 
transport of air pollution across state boundaries. Subsequent to the 
release of the January 2015 memo and the August 2015 NODA with air 
quality modeling results, the EPA notes that it also held a webinar, a 
workshop and conference calls with states. Moreover, while we 
appreciate the importance of working with states in the SIP development 
process, states have the primary responsibility for developing SIPs to 
address the requirements of CAA section 110(a)(2)(D)(i)(I). As noted 
earlier, in EPA v. EME Homer City Generation, L.P., the Supreme Court 
clearly held that ``nothing in the statute places the EPA under an 
obligation to provide specific metrics to States before they undertake 
to fulfill their good neighbor obligations.'' 134 S. Ct. at 1601. 
However, EPA remains committed to working with the State on reviewing 
technical information for the purposes of determining compliance with 
the requirements of 110(a)(2)(D)(i)(I).
    Comment: Commenter Western Energy Alliance stated that ``EPA has 
failed to provide sufficient evidence that it reviewed and considered 
state exceptional events packages that may provide mitigating 
circumstances for NAAQS violations based on events such as wildfires or 
stratospheric intrusions of ozone.''
    Response: In order for emissions to be excluded on the basis of an 
exceptional event per CAA 319(b), all exceptional event criteria 
applicable to the activity must be met. No exceptional event 
demonstrations relevant to the Douglas County, Colorado monitor were 
submitted to the EPA for evaluation, so no evidence was available with 
regard to the impact of exceptional event emissions on the violating 
monitor in the design value period considered. To the extent that the 
EPA approves an

[[Page 9152]]

exceptional events demonstration for this area in the future, the EPA 
can consider the impacts that action or other new information would 
have on the modeling results either in reviewing a subsequent SIP 
submission from Wyoming, which the State may submit at any time, or in 
evaluating whether any emissions reductions are necessary to address 
downwind air quality in addressing the Agency's FIP obligation 
triggered by this disapproval.
    Comment: Commenter Sierra Club stated that the EPA should 
disapprove Wyoming's prong 1 submission for the 2008 ozone NAAQS. The 
commenter asserted that the Douglas County, Colorado maintenance 
receptor (to which Wyoming was modeled to contribute above one percent) 
\31\ should instead be a nonattainment receptor, but it is not because 
the modeling under-predicts the receptor's 2017 ozone design value. The 
commenter based this assertion on a weight of evidence approach using 
ambient air monitoring data collected at the receptor. The commenter 
stated that such a weight of evidence approach was appropriate to 
determine this receptor should be nonattainment, and noted that the EPA 
had used a weight of evidence approach in its action on Arizona's 
transport SIP. The CSAPR Update modeling projected that the Douglas 
County, Colorado receptor would have a 2017 average design value of 
75.5 ppb, with a maximum design value of 77.6 ppb.\32\ The commenter 
first asserted that the 75.5 ppb level should indicate nonattainment 
rather than maintenance because the design value exceeds the 75.0 level 
of the NAAQS, referring to EPA's basis for a maintenance categorization 
as ``bad math.'' The commenter then stated that the Douglas County, 
Colorado receptor will indeed be nonattainment for the 2015-2017 
period. The commenter included the 4th highest daily maximum values, on 
which the 2008 ozone NAAQS is based, for the years 2010 through 2016, 
which the EPA has replicated (with edits) in Table 1, below.
---------------------------------------------------------------------------

    \31\ For details about the Douglas County, Colorado receptor, 
see the proposal for this final rulemaking at 81 FR 81715.
    \32\ See document EPA-R08-OAR-2016-0521-0002, ``Final CSAPR 
Update_Ozone Design Values & Contributions_All Sites,'' in the 
docket for this action.

   Table 1--4th Highest Daily Max at Douglas County, Colorado Receptor
------------------------------------------------------------------------
                                                               4th Max
                            Year                                (ppb)
------------------------------------------------------------------------
2016.......................................................           78
2015.......................................................           81
2014.......................................................           74
2013.......................................................           83
2012.......................................................           79
2011.......................................................           81
2010.......................................................           78
------------------------------------------------------------------------

    The commenter stated that the 2015-2017 monitored design value at 
the Douglas County, Colorado receptor could only attain the NAAQS if 
the receptor recorded a 4th daily maximum value of 66 ppb in 2017, a 
value well below the smallest value since 2010. The commenter asserted 
that the previous 7 years of monitoring data provide a weight of 
evidence analysis demonstrating that this receptor will be 
nonattainment for the 2015-2017 design value period. The commenter also 
asserted that it is unsurprising that the CSAPR Update modeling 
analysis under-predicts the 2017 design values because it included 2009 
monitoring data which was impacted by the Great Recession, during which 
time ozone levels decreased. The commenter therefore recommended that 
the EPA disapprove Wyoming's February 6, 2014 prong 1 submittal for the 
2008 ozone NAAQS.
    Response: First, the EPA does not agree that because the receptor 
is projected to have an average design value of 75.5, that the EPA 
should label this receptor a nonattainment receptor. As explained in 
the 2016 AQM TSD, ``In determining compliance with the NAAQS, ozone 
design values are truncated to integer values. For example, a design 
value of 75.9 ppb is truncated to 75 ppb which is attainment. In this 
manner, design values at or above 76.0 ppb are considered to be 
violations of the NAAQS.'' \33\ This method is consistent with the 
method to compliance with the 2008 ozone NAAQS.\34\ Therefore a design 
value of 75.5 is not considered a violation of the standard.
---------------------------------------------------------------------------

    \33\ See 2016 AQM TSD at pg. 11.
    \34\ See 40 CFR part 50, Appendix P--Interpretation of the 
Primary and Secondary National Ambient Air Quality Standards for 
Ozone; Section 2.1: ``Computing 8-hour averages. Hourly average 
concentrations shall be reported in parts per million (ppm) to the 
third decimal place, with additional digits to the right of the 
third decimal place truncated.''
---------------------------------------------------------------------------

    The EPA agrees that recent monitoring data at the Douglas County, 
Colorado monitor suggest that the site faces a risk of not attaining 
the NAAQS in 2017. However, that risk is uncertain as the future 
monitored 2017 design value is unknown at this time. In light of this 
uncertainty and the statute's silence on how nonattainment and 
maintenance should be identified under the good neighbor provision, the 
EPA has developed a reasonable approach to identify downwind 
nonattainment and maintenance receptors. When evaluating air quality 
modeling for purposes of interstate transport, the EPA has routinely 
identified nonattainment receptors as those with monitors that are both 
projected to be unable to attain in an appropriate future year and that 
are measuring nonattainment based on current data--i.e., if the 
projected average design value in the future year does not exceed the 
standard, the EPA does not identify that receptor as a nonattainment 
receptor, but rather as a maintenance receptor. See 81 FR 74517 (CSAPR 
Update); 80 FR 75723 through 75724 (Proposed CSAPR Update); 76 FR 48227 
through 48228 (CSAPR); 70 FR 25243-33 (CAIR); see also North Carolina, 
531 F.3d at 913-914 (affirming as reasonable EPA's approach to defining 
nonattainment in CAIR). Given the EPA's modeling does not project that 
the Douglas County, Colorado receptor will be in nonattainment in 2017, 
even though it may currently be measuring nonattainment, it would be 
inconsistent with the EPA's past practice to identify that receptor as 
a nonattainment receptor.
    Moreover, the EPA does not agree that it should identify a 
nonattainment receptor based on the formula proposed by the commenter 
because the data cited by the commenter does not conclusively prove 
that this monitor will be in nonattainment based on 2017 data.\35\ 
First, the commenter notes that it would be possible for the 2017 
design value to be sufficiently low such that the 3-year average is 
attaining the NAAQS. Second, the CAA provides that should 2017 data 
yield a fourth highest 8-hour concentration of 75.9 ppb or below, the 
state can petition EPA for additional time to demonstrate attainment of 
the NAAQS. See CAA section 181(a)(5).
---------------------------------------------------------------------------

    \35\ Although the commenter is correct that the EPA evaluated 
the weight of the evidence in the Arizona SIP submission, the EPA 
did not use the approach proposed by the commenter to average 
projections and monitored data in identifying potential receptors.
---------------------------------------------------------------------------

    That said, the EPA agrees that the receptor may have problems 
maintaining the standard in 2017 and has therefore identified this site 
as a maintenance receptor. As a result of this finding, the EPA and the 
State of Wyoming will need to evaluate what

[[Page 9153]]

further emissions reductions may be required to ensure that the State's 
impact on downwind air quality is mitigated such that the State will 
not interfere with maintenance of the standard at that receptor.
    The weight of evidence analysis in our action on the Arizona SIP 
determined the nature of the projected receptor's interstate transport 
problem as to the magnitude of ozone attributable to interstate 
transport from all upwind states collectively contributing to the air 
quality problem, not to the identification of that receptor. In the EPA 
action on the Arizona SIP, Arizona was the only state that contributed 
greater than the 1 percent threshold to the projected 2017 levels of 
the 2008 ozone NAAQS at the El Centro receptor. The EPA's assessment 
concluded that emissions reductions from Arizona are not necessary to 
address interstate transport because the total collective upwind state 
ozone contribution to these receptors is relatively low compared to the 
air quality problems typically addressed by the good neighbor 
provision. As discussed previously, the EPA similarly evaluated 
collective contribution to the Douglas County, Colorado monitor and 
finds the collective contribution of transported pollution to be 
substantial. Furthermore, in our action on the Arizona SIP we did not 
deviate from our past practice in identifying nonattainment and 
maintenance receptors in the way that commenter suggests we should do 
here.
    The EPA does not agree that its projections are unreliable because 
the 2009 data are affected by the ``Great Recession.'' In determining 
our 2009-2013 base period average design values, the data from 2009 are 
only weighted once, whereas, data in 2011 which has higher ozone is 
weighted 3 times in the calculations. In addition, our emissions data 
are projected from 2011 to 2017 and, thus, the effects of the recession 
on 2009 emissions have very little influence our 2017 projected 
emissions. In this respect, the air quality and emissions in 2009 have 
only a very limited influence on the projected design values. As 
described in EPA's air quality modeling guidance for ozone attainment 
demonstrations, the use of 5[hyphen]year weighted average design 
values, as applied here, is intended to focus the base period air 
quality on the year of base case emissions, 2011 for this analysis, and 
to smooth out, to some extent, the effects of inter[hyphen]annual 
variability in ozone concentrations.\36\ Thus, EPA continues to believe 
that including ambient data from 2009 is appropriate for projecting 
future year ozone concentrations as part of the final rule.
---------------------------------------------------------------------------

    \36\ Modeling Guidance for Demonstrating Attainment of Air 
Quality Goals for Ozone, PM2.5, and Regional Haze 
available in the docket and at: http://www.epa.gov/ttn/scram/guidance/guide/Draft_O3-PM-RH_Modeling_Guidance-2014.pdf.
---------------------------------------------------------------------------

    Comment: Commenter Sierra Club asserted that the EPA's analysis of 
Wyoming's February 6, 2014 submittal ignores wintertime ozone levels. 
The commenter asserted that the EPA relies on the CSAPR Update analysis 
for its Wyoming ozone transport analysis, and that the CSAPR Update 
analysis throws out wintertime ozone data.\37\ The commenter stated 
that it is inappropriate for the EPA to exclude the wintertime ozone 
data because the EPA has elsewhere acknowledged that wintertime ozone 
is an important issue in Wyoming and neighboring states. To support 
this point, the commenter cited the EPA's revision to the 2008 ozone 
NAAQS, which states that ``Elevated levels of winter-time O3 have also 
been measured in some western states where precursor emissions can 
interact with sunlight off the snow cover under very shallow, stable 
boundary layer conditions.'' 80 FR 65416, October 26, 2015. The 
commenter also cited the ozone NAAQS revision to show that the ozone 
seasons for both Colorado and Utah are year-round, and that the EPA 
must therefore include an evaluation of wintertime ozone before it can 
approve any ozone transport provisions for Wyoming. 80 FR 65419 through 
65420, October 26, 2015.
---------------------------------------------------------------------------

    \37\ Id. The commenter specifically cited the following language 
from the document: ``In addition, there are 7 sites in 3 counties in 
the West that were excluded from this file because the ambient 
design values at these sites were dominated by wintertime ozone 
episodes and not summer season conditions that are the focus of this 
transport assessment.'' Citing EPA-R08-OAR-2016-0521-0002 at 
``Readme'' tab.
---------------------------------------------------------------------------

    Response: As stated in the CSAPR Update Final, ``Ozone levels are 
generally higher during the summer months.'' 81 FR 74513, October 26, 
2016. The 2016 AQM TSD states that ``High winter ozone concentrations 
that have been observed in certain parts of the Western U.S. are 
believed to result from the combination of strong wintertime 
inversions, large NOX and VOC emissions from nearby oil and 
gas operations, increased UV intensity due to reflection off of snow 
surfaces and potentially still uncharacterized sources of free 
radicals.'' 2016 AQM TSD at 14. Thus, high winter-time ozone episodes 
are due to a build-up of local emissions combined with local stagnation 
meteorological conditions rather than interstate transport. The EPA 
therefore disagrees that it must evaluate wintertime ozone before 
approving Wyoming's SIP as to the prong 1 requirements of section 
110(a)(2)(D)(i)(I).

III. Final Action

    The EPA is approving CAA section 110(a)(2)(D)(i)(I) prongs 1, 2 and 
4 for the 2008 Pb NAAQS, prong 1 for the 2008 ozone NAAQS, prongs 1 and 
2 for the 2010 NO2 NAAQS, and prong 4 for the 2010 
SO2 NAAQS, as shown in Table 2, below. The EPA is 
disapproving prong 4 for the 2006 PM2.5, 2008 ozone, 2010 
NO2 and 2012 PM2.5 NAAQS, and prong 2 for the 
2008 ozone NAAQS, as shown in Table 3. Disapproval of prong 2 for the 
2008 ozone NAAQS will establish a 2-year deadline, under CAA section 
110(c), for the EPA to promulgate a FIP, unless the EPA approves a SIP 
that meets these requirements. As stated at proposal, the prong 4 
disapprovals do not have additional practical consequences for the 
State or the EPA because the FIP already in place will satisfy the 
prong 4 requirements for these NAAQS. The EPA will work with Wyoming to 
provide assistance as necessary to help Wyoming develop an approvable 
SIP submittal and the EPA is committed to taking prompt action on a SIP 
submitted by the State. Disapproval does not start a mandatory 
sanctions clock for Wyoming pursuant to CAA section 179 because this 
action does not pertain to a part D plan for nonattainment areas 
required under CAA section 110(a)(2)(I) or a SIP call pursuant to CAA 
section 110(k)(5).

  Table 2--List of Wyoming Interstate Transport Prongs That the EPA Is
                                Approving
------------------------------------------------------------------------
                                Approval
-------------------------------------------------------------------------
February 6, 2014 submittal--2008 Ozone NAAQS: (D)(i)(I) prong 1.
October 12, 2011 submittal--2008 Pb NAAQS: (D)(i)(I) prongs 1 and 2,
 (D)(i)(II) prong 4.
January 24, 2014 submittal--2010 NO2 NAAQS: (D)(i)(I) prongs 1 and 2.
March 6, 2015 submittal--2010 SO2 NAAQS: (D)(i)(II) prong 4.
------------------------------------------------------------------------


  Table 3--List of Wyoming Interstate Transport Prongs That the EPA Is
                              Disapproving
------------------------------------------------------------------------
                               Disapproval
-------------------------------------------------------------------------
August 19, 2011 submittal--2006 PM2.5 NAAQS: (D)(i)(II) prong 4.
February 6, 2014 submittal--2008 Ozone NAAQS: (D)(i)(I) prong 2,
 (D)(i)(II) prong 4.

[[Page 9154]]

 
January 24, 2014 submittal--2010 NO2 NAAQS: (D)(i)(II) prong 4.
June 24, 2016 submittal--2012 PM2.5 NAAQS: (D)(i)(II) prong 4.
------------------------------------------------------------------------

IV. Statutory and Executive Order Reviews

    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 actions, 
provided that they meet the criteria of the CAA. Accordingly, this 
action merely approves some state law provisions as meeting federal 
requirements and disapproves other state law because it does not meet 
federal requirements; this action does not impose additional 
requirements beyond those imposed by state law. For that reason, this 
action:
     Is not a significant regulatory action subject to review 
by the Office of Management and Budget under Executive Orders 12866 (58 
FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have Federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of Section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the Clean Air Act; and
     Does not provide 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, the SIP 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, 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).
    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the 
Small Business Regulatory Enforcement Fairness Act of 1996, generally 
provides that before a rule may take effect, the agency promulgating 
the rule must submit a rule report, which includes a copy of the rule, 
to each House of the Congress and to the Comptroller General of the 
United States. EPA will submit a report containing this action and 
other required information to the U.S. Senate, the U.S. House of 
Representatives, and the Comptroller General of the United States prior 
to publication of the rule in the Federal Register. A major rule cannot 
take effect until 60 days after it is published in the Federal 
Register. This action is not a ``major rule'' as defined by 5 U.S.C. 
804(2).
    Under section 307(b)(1) of the CAA, petitions for judicial review 
of this action must be filed in the United States Court of Appeals for 
the appropriate circuit by April 4, 2017. Filing a petition for 
reconsideration by the Administrator of this final rule does not affect 
the finality of this action for the purposes of judicial review nor 
does it extend the time within which a petition for judicial review may 
be filed, and shall not postpone the effectiveness of such rule or 
action. This action may not be challenged later in proceedings to 
enforce its requirements. (See CAA section 307(b)(2).)

List of Subjects in 40 CFR Part 52

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

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

    Dated: January 17, 2017.
Debra H. Thomas,
Acting Regional Administrator, Region 8.
    40 CFR part 52 is amended to read as follows:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

0
1. The authority citation for part 52 continues to read as follows:

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

Subpart ZZ--Wyoming

0
2. In Sec.  52.2620, the table in paragraph (e) is amended by adding 
the entry ``(27) XXVII'' at the end of the table to read as follows:


Sec.  52.2620   Identification of plan.

* * * * *
    (e) * * *

[[Page 9155]]



----------------------------------------------------------------------------------------------------------------
                                                                     EPA
       Rule No.               Rule title        State effective   effective      Final rule         Comments
                                                     date            date       citation/date
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
(27) XXVII............  Interstate transport   2/6/2014; 10/12/     3/6/2017  [Insert Federal
                         SIP for Section        2011; 1/24/                    Register
                         110(a)(2)(D)(i)        2014; 3/6/2015.                citation] 2/3/
                         prong 1-2008 Ozone                                    2017.
                         NAAQS; prongs 1, 2
                         and 4-2008 Pb NAAQS;
                         prong 1 and 2-2010
                         NO2 NAAQS; prong 4-
                         2010 SO2 NAAQS.
----------------------------------------------------------------------------------------------------------------


[FR Doc. 2017-02197 Filed 2-2-17; 8:45 am]
BILLING CODE 6560-50-P


