Approval and Promulgation of State Implementation Plan Revisions; State of North Dakota; Air Pollution Control Rules, and Interstate Transport of Pollution for the 1997 PM2.5, 31290-31306 [2010-13051]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 75, Number 106 (Thursday, June 3, 2010)]
[Rules and Regulations]
[Pages 31290-31306]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-13051]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2009-0282; FRL-9155-6]


Approval and Promulgation of State Implementation Plan Revisions; 
State of North Dakota; Air Pollution Control Rules, and Interstate 
Transport of Pollution for the 1997 PM2.5 and 8-Hour Ozone 
NAAQS: ``Significant Contribution to Nonattainment'' and ``Interference 
With Prevention of Significant Deterioration'' Requirements

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency is approving State 
Implementation Plan (SIP) revisions submitted by the State of North 
Dakota on April 6, 2009. Specifically, EPA is approving revisions to 
the North Dakota air pollution control rules regarding prevention of 
significant deterioration of air quality, and partially approving the 
SIP revision ``Interstate Transport of Air Pollution'' addressing the 
requirements of Clean Air Act section 110(a)(2)(D)(i) for the 1997 
PM2.5 and 8-hour ozone National Ambient Air Quality 
Standards (NAAQS). These revisions, referred to as the Interstate 
Transport of Air Pollution SIP, address the requirements of Clean Air 
Act section 110(a)(2)(D)(i) for the 1997 8-hour ozone and 1997 
PM2.5 National Ambient Air Quality Standards (NAAQS). In 
this action, EPA is approving the North Dakota Interstate Transport SIP 
provisions that address the requirement of section 110(a)(2)(D)(i)(I) 
that emissions from the state's sources do not ``contribute 
significantly'' to nonattainment of the 1997 8-hour ozone NAAQS and the 
1997 PM2.5 NAAQS in any other state. In addition, EPA is 
approving the provisions of this SIP that address the requirement of 
section 110(a)(2)(D)(i)(II) that emissions from the state's sources do 
not interfere with measures required in the SIP of any other state 
under part C of the Clean Air Act (CAA) to prevent ``significant 
deterioration of air quality.'' EPA will act at a later date on the 
North Dakota Interstate Transport SIP provisions that address the 
remaining two requirements of section 110(a)(2)(D)(i), that emissions 
from the state's sources do not ``interfere with maintenance'' of the 
1997 8-hour ozone and 1997 PM2.5 NAAQS in any other state, 
and do not interfere with measures required in the SIP of any other 
state to ``protect visibility.'' This action is being taken under 
section 110 of the Clean Air Act.

DATES: Effective Date: This final rule is effective July 6, 2010.

ADDRESSES: EPA has established a docket for this action under Docket ID 
No. EPA-R08-OAR-2009-0282. All documents in the docket are listed on 
the www.regulations.gov Web site. Although listed in the index, some 
information is not publicly available, e.g., Confidential Business 
Information (CBI) or other information whose disclosure is restricted 
by statute. Certain other material, such as copyrighted material, is 
not placed on the Internet and will be publicly available only in hard 
copy form. Publicly available docket materials are available either 
electronically through www.regulations.gov, or in hard copy at the Air 
Program, Environmental Protection Agency (EPA), Region 8, 1595 Wynkoop 
Street, Denver, Colorado 80202-1129. EPA requests that if at all 
possible, you contact the individual listed in the FOR FURTHER 
INFORMATION CONTACT section to view the hard copy of the docket. You 
may view the hard copy of the docket Monday through

[[Page 31291]]

Friday, 8 a.m. to 4 p.m., excluding Federal holidays.

FOR FURTHER INFORMATION CONTACT: Domenico Mastrangelo, Air Program, 
U.S. Environmental Protection Agency, Region 8, Mailcode 8P-AR, 1595 
Wynkoop Street, Denver, Colorado 80202-1129, (303) 312-6416, 
mastrangelo.domenico@epa.gov.

SUPPLEMENTARY INFORMATION:

Definitions

    For the purpose of this document, we are giving meaning to certain 
words or initials as follows:
    (i) The words or initials Act or CAA mean or refer to the Clean Air 
Act, unless the context indicates otherwise.
    (ii) The words EPA, we, us or our mean or refer to the United 
States Environmental Protection Agency.
    (iii) The initials SIP mean or refer to State Implementation Plan.
    (iv) The words State or North Dakota mean the State of North 
Dakota, unless the context indicates otherwise.

Table of Contents

I . Background
II . Response to Comments
III. Section 110(l)
IV. Final Action
V. Statutory and Executive Order Reviews

I. Background and Purpose

    In a proposed rule action published March 31, 2010 EPA proposed 
approval of revisions to the State provisions on the prevention of 
significant deterioration (PSD) of air quality in subsection 33-15-15-
01.2 of the North Dakota Administrative Code (NDAC),\1\ and partial 
approval of the North Dakota Interstate Transport of Air Pollution SIP 
for the 1997 PM2.5 and 8-hour ozone National Ambient Air 
Quality Standards (NAAQS). The revisions to NDAC subsection 33-15-15-
01.2, and the addition to the North Dakota SIP of section 7.8, 
``Interstate Transport of Air Pollution,'' were adopted by the State of 
North Dakota on April 1, 2009 and submitted to EPA on April 6, 2009.
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    \1\ EPA notes that in the referenced proposed rule there were 
references to the revision of ``NDAC subsection 33-15-15-01.02'' (75 
FR 16027). As was clear from the context, the references were the 
results of typographical errors.
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    In chapter 33-15-15, NDAC, Prevention of Significant Deterioration 
of Air Quality, revisions were made to subsection 33-15-15-01.2, Scope. 
The baseline date for incorporation by reference of the federal PSD 
program set out at 40 CFR 52.21 was updated to August 1, 2007. In 
addition, various administrative corrections and clarifications were 
made. In our proposal to approve these revisions, EPA stated that the 
revisions were made to make the North Dakota PSD program consistent 
with federal requirements. EPA did not receive comments that persuade 
the Agency that the revisions are less stringent than or inconsistent 
with federal requirements, and thus EPA is approving them in today's 
final action.
    Section 110(a)(2)(D)(i) of the CAA requires that a state's SIP must 
contain adequate provisions prohibiting any source or other type of 
emissions activity within the state from emitting any air pollutant in 
amounts which will: (1) Contribute significantly to nonattainment of 
the NAAQS in any other state; (2) interfere with maintenance of the 
NAAQS by any other state; (3) interfere with any other state's required 
measures to prevent significant deterioration of air quality; or (4) 
interfere with any other state's required measures to protect 
visibility. In our proposed rule EPA proposed partial approval of the 
North Dakota Interstate Transport of Air Pollution SIP for the 1997 
PM2.5 and 8-hour ozone NAAQS. Specifically, EPA proposed 
approval of the North Dakota SIP sections that addressed the first and 
third requirements, ``significant contribution'' and ``interference 
with PSD'' of the Interstate Transport CAA provisions. EPA will act at 
a later date on the North Dakota Interstate Transport SIP sections that 
address the remaining requirements: ``interference with maintenance'' 
and ``interference with visibility.''
    To assess whether emissions from North Dakota contribute 
significantly to downwind nonattainment for the 1997 PM2.5 
NAAQS, North Dakota and EPA's technical analysis relied on the results 
of CAIR modeling and on monitoring data in neighboring downwind states. 
The CAIR modeling results indicated that the State contribution to the 
closest nonattainment area was below the ``significant contribution'' 
threshold. Monitoring data showed that in downwind states there were no 
monitors violating the 1997 24-hour or annual PM2.5 NAAQS.
    To assess whether emissions from North Dakota contribute 
significantly to downwind nonattainment for the 1997 8-hour ozone 
NAAQS, EPA's technical analysis relied on EPA's 2006 Guidance, 
recommending consideration of available EPA modeling conducted in 
conjunction with CAIR,\2\ or in the absence of such EPA modeling, 
consideration of other information such as the amount of emissions, the 
geographic location of violating areas, meteorological data, or various 
other forms of information that would be relevant to assessing the 
likelihood of significant contribution to violations of the NAAQS in 
another state. Consistent with the NOX SIP Call and CAIR, 
our technical analysis assessed the extent of ozone transport from 
North Dakota not just for areas designated nonattainment, but also for 
areas in violations of the NAAQS. Because EPA did not have detailed 
modeling for North Dakota and nearby downwind states, our approach did 
not rely on a quantitative determination of North Dakota's contribution 
but on a weight-of-evidence approach using quantitative information 
such as North Dakota's distance from areas with monitors showing 
violations of the NAAQS, modeling results outlining wind vectors for 
regional transport of ozone on high ozone days, CAIR modeling results 
for other states, and results of modeling studies for the nonattainment 
areas specifying the range of wind directions along which contribution 
of ozone transport occurred. Given that the assessments for each of 
these pieces of evidence are not individually definitive or outcome 
determinative, EPA concluded in its proposed action that the various 
factual and technical considerations supported a determination of no 
significant contribution from North Dakota emissions to the ozone 
nonattainment areas noted above.
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    \2\ In this action the expression ``CAIR'' refers to the final 
rule published in the May 12, 2005 Federal Register and entitled 
``Rule to Reduce Interstate Transport of Fine Particulate Matter and 
Ozone (Clean Air Interstate Rule); Revisions to Acid Rain Program; 
Revisions to NOX SIP Call; Final Rule'' (70 FR 25162).
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    EPA did not receive comments that persuade the Agency that there is 
such significant contribution for the 1997 ozone or PM2.5 
NAAQS and thus in today's final action EPA is making a final regulatory 
determination that North Dakota's emissions sources do not contribute 
significantly to violations of the 1997 8-hour ozone NAAQS in any other 
state.

II. Response to Comments

    EPA received one letter from WildEarth Guardians (WG) and one 
letter from the Sierra Club commenting on EPA's Federal Register action 
proposing approval of the portion of the North Dakota Interstate 
Transport SIP that addresses the ``significant contribution to 
nonattainment'' and PSD requirements of CAA Section 110(a)(2)(D)(i) for 
the 1997 8-hour ozone and PM2.5 NAAQS, and specific 
revisions to the air quality control rules

[[Page 31292]]

addressed within that proposal. In this section EPA responds to the 
significant adverse comments made by the commenters.
    Comment No. 1--WG opposed EPA's approval of North Dakota's revision 
of its PSD program, based on several alleged deficiencies in that 
program. Although WG does not explicitly state it, in the context of 
this action, which also approves the PSD portion of the interstate 
transport SIP noted above, WG's comments could be taken to argue that 
the alleged deficiencies adversely impact the measures required in 
other states to prevent significant deterioration of air quality in 
such states. To the extent WG makes this argument, EPA responds below.
    As to the first deficiency, WG noted that the current federally-
enforceable version of the North Dakota PSD program incorporates 40 CFR 
52.21 as it stood on October 1, 2003. WG stated that the PSD program in 
North Dakota should be amended to reflect the effects of court opinions 
that vacated portions of that version of 52.21.
    EPA Response--EPA disagrees with the commenter's argument that the 
North Dakota SIP does not reflect current requirements. North Dakota's 
submittal incorporated 40 CFR 52.21 as it stood on August 1, 2007. The 
August 1, 2007 version of 40 CFR 52.21 fully reflected the effects of 
federal court decisions vacating certain portions of NSR rules 
promulgated in 2002 and 2003.\3\ Therefore, EPA believes that the North 
Dakota PSD program approved by EPA in this action also reflects the 
effects of those decisions and is therefore consistent with federal 
requirements.
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    \3\ 67 FR 80186 (Dec. 31, 2002); 68 FR 61248 (Oct. 23, 2003); 
New York v. U.S. EPA, 413 F.3d 3 (D.C. Cir. 2005); New York v. EPA, 
443 F.3d 880 (D.C. Cir. 2006).
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    EPA agrees with the implicit argument (mentioned above) that 
certain deficiencies in a state's existing SIP, or in a section 
110(a)(2)(D) SIP submission itself, could affect the approvability of 
the section 110(a)(2)(D) SIP submission with respect to the PSD 
requirement. As provided in EPA's guidance for such SIP submissions for 
the 1997 8-hour ozone and PM2.5 NAAQS, EPA made 
recommendations with respect to specific SIP revisions that it 
anticipated would be appropriate to address in the section 110(a)(2)(D) 
SIP submissions for these NAAQS, whether by reference to other 
submissions already made or within the same SIP submission. For 
example, for the requirements of the PSD element of section 
110(a)(2)(D) for these NAAQS, EPA indicated that a state's SIP should 
reflect the current requirements for the implementation of the PSD and 
nonattainment NSR requirements for these NAAQS, as a means of 
establishing that the state's SIP would not interfere with measures to 
prevent significant deterioration in other states. EPA believes that 
this assessment is fact specific, however, and that the question of 
whether a state's SIP could cause such interference in another state 
must be examined on a case by case basis.
    In this instance, because the North Dakota program now tracks the 
requirements of 40 CFR 52.21 as of August 1, 2007, WG's concern gives 
no reason to conclude that the revisions could interfere with the 
measures required in other states.
    Comment No. 2--As another potential defect in the North Dakota PSD 
program, WG noted that the North Dakota PSD program adds the sentence: 
``[t]his term does not include effects on integral vistas,'' to 40 CFR 
52.21(b)(29), that is, the definition of ``adverse impact on 
visibility.'' WG argued that this additional language renders the PSD 
program less stringent than federal requirements.
    EPA Response--EPA disagrees with WG's comment. In this comment, and 
others, WG appears to believe that per se any deviation from the 
language of 40 CFR 52.21 is invalid. However, the minimum federal 
requirements for state PSD programs are specified in 40 CFR 51.166, not 
in 52.21.\4\ One way in which a state PSD program may meet the 
requirements of 51.166 is to adopt by reference the federal PSD program 
at 52.21, as North Dakota has here. To determine whether deviations 
from 52.21 in the North Dakota PSD program meet federal requirements 
for a state program, the program is judged against the minimum federal 
requirements for a state PSD program given in 51.166.
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    \4\ ``The EPA implements the statutory PSD requirements through 
two sets of regulations. At 40 CFR 51.166, EPA has set minimum 
program requirements for States to follow in preparing, adopting, 
and submitting a PSD program for inclusion as part of the required 
SIP pursuant to Section 110(c) of the Act. At 40 CFR 52.21, EPA has 
promulgated a Federal PSD program requiring the Administrator's 
preconstruction review and approval of major new or modified 
stationary sources in the absence of an approved State PSD program, 
and for areas such as Indian Lands and Outer Continental Shelf areas 
that are outside of the jurisdiction of individual States.'' 58 FR 
31622, 31623 (June 3, 1993). For states that--unlike North Dakota--
lack a SIP-approved PSD program, EPA may delegate implementation of 
52.21 to the state. E.g., 73 FR 53401 (Sept. 16, 2008) (``Prior to 
approval of Michigan's submitted PSD program, EPA delegated to 
Michigan (via delegation letter dated September 26, 1988) the 
authority to issue PSD permits through the Federal PSD rules at 40 
CFR 52.21.'').
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    As to the requirements of 51.166, section 51.166(o)(1) creates a 
requirement for visibility impact analysis for new major stationary 
sources and major modifications. Federal requirements for protection of 
visibility in state SIPs are set out in subpart P of part 51. 
Procedures for the visibility impact analysis required by 51.166(o)(1) 
are given in 51.307, which, by its placement in subpart P, uses the 
definition of the term ``adverse impact on visibility'' at 51.301. 
North Dakota's definition is consistent with the federal definition; in 
fact, it matches it precisely. In addition, no integral vistas have 
been identified under section 51.304, so the addition of the sentence 
has no effect. Therefore, EPA disagrees with the comment that the North 
Dakota PSD program, by modifying 52.21(b)(29), does not meet federal 
requirements.
    Comment No. 3--As another potential issue, WG noted that the North 
Dakota PSD program deletes references to NAAQS at 52.21(d), (k)(1), and 
(v)(2)(iv)(a). WG argued that the references must be restored to ensure 
that the NAAQS apply everywhere and that PSD increments are federal 
increments.
    EPA Response--The cited references are replaced in the North Dakota 
rules by provisions that apply the state ambient air quality standards 
for areas within North Dakota's jurisdiction and that apply the NAAQS 
elsewhere. As discussed elsewhere in these responses, updates to the 
state ambient air quality standards, consistent with revisions to the 
NAAQS, were submitted by North Dakota to EPA on April 1, 2009. EPA will 
be acting on the revision in a separate action. Also, the North Dakota 
PSD program incorporates 40 CFR 52.21(c), which defines the PSD 
increments, by reference without modification; therefore, the North 
Dakota PSD increments are the federal increments.
    Comment No. 4--As an additional concern, WG noted that the North 
Dakota PSD program replaces 40 CFR 52.21(h) with different state stack 
height requirements. WG argued that these requirements must be at least 
as stringent as federal requirements. Implicitly, WG argued that these 
different stack height requirements would interfere with other states's 
required PSD measures.
    EPA Response--EPA disagrees with this comment. WG did not explain 
or identify any way in which the state requirements are less stringent 
than federal requirements. EPA has reviewed

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the North Dakota state stack height requirements and finds that the 
requirements are at least as stringent as those in 40 CFR 51.166(h), 
which specifies the minimum stack height requirements for a state PSD 
program. Therefore, EPA does not believe that the provision creates a 
deficiency in the North Dakota PSD program or that the North Dakota SIP 
interferes with measures required for prevention of significant 
deterioration in any other state for purposes of the 1997 8-hour ozone 
and PM2.5 NAAQS.
    Comment No. 5--WG further argued that the North Dakota PSD program 
must include 40 CFR 52.21(l)(1) and must update the reference to 
Appendix W to part 51 in order to be consistent with current federal 
law requirements. WG also asserted that the North Dakota guidelines for 
air quality modeling are unacceptable because they are less stringent 
than applicable federal requirements.
    EPA Response--EPA disagrees with the commenter's assessment on this 
point. The federal requirements for modeling in a PSD program are set 
out at 40 CFR 51.166(l). The North Dakota PSD provision that replaces 
52.21(l)(1) is consistent with these requirements. Furthermore, the 
provision does not specify a particular date for incorporation of 
Appendix W; EPA therefore believes no update to the reference is 
necessary. Finally, 51.166(l) provides for modification or substitution 
of models in Appendix W on a case-by-case or generic basis with written 
approval of the Administrator. The Administrator has approved, in 
writing, use of the North Dakota guideline on a generic basis by 
approving previous submittals of the North Dakota PSD program that 
contained the same provision allowing for use of the guideline. 
Therefore, EPA believes that the North Dakota provision is consistent 
with federal requirements in 51.166(l).
    Comment No. 6--WG also identified analyses for visibility as 
another alleged deficiency in the existing PSD program in North Dakota. 
WG noted that the state's PSD program requires visibility analysis for 
new source review to be prepared in accordance with state requirements. 
WG argued that these requirements are less stringent than federal 
requirements, and that the provision must therefore be deleted.
    EPA Response--EPA disagrees with the commenter's assessment. In 
this instance, WG did not explain or identify any way in which the 
state requirements are less stringent than federal requirements. The 
federal requirements for visibility analysis procedures for new source 
review in state PSD programs are provided in 40 CFR 51.307. The 
procedures do not specify a particular method for visibility analysis. 
EPA has reviewed the North Dakota requirements for visibility analysis 
and finds they are consistent with federal requirements. Therefore, 
this is not a basis for disapproval of the North Dakota PSD program 
revision or the section 110(a)(2)(D) submission.
    Comment No. 7--WG expressed concern with certain public process 
provisions in the North Dakota SIP. In particular, WG identified state 
specific provisions for public participation replacing those at 
52.21(q). WG argued that the state should not be allowed to provide 
``summaries'' of other materials it considered in making its permit 
decisions.\5\ WG also argued that the state provisions should require 
the Department to respond to relevant comments.
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    \5\ The commenter refers to section (g) of the provision, but 
from the mention of ``summaries'' it appears the commenter is 
referring to section (b).
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    EPA Response--EPA disagrees with the commenter's view of these 
specific requirements. The minimum federal requirements for public 
participation in a state PSD program are set out in 51.166(q). The 
state provision cited by WG is consistent with the requirements at 
51.166(q)(2)(ii); in fact, the provision matches 51.166(q)(2)(ii) 
precisely. Therefore, EPA believes that the North Dakota PSD program 
meets federal requirements for public participation. As such, this is 
not a basis for disapproval of the North Dakota PSD program revision or 
the section 110(a)(2)(D) submission.
    Comment No. 8--WG identified other procedural requirements as 
potential defects in the North Dakota SIP. WG noted that the North 
Dakota PSD program adds to 52.21(r)(2) the sentence: ``[i]n cases of 
major construction projects involving long lead times and substantial 
financial commitments, the department may provide by a condition to the 
permit to construct a time period greater than eighteen months when 
such time extension is supported by sufficient documentation by the 
applicant.'' WG argued that this provision should be removed because it 
allows major sources to be built with stale determinations of ambient 
air impacts and best available control technology.
    EPA Response--Federal requirements for source obligations in a 
state PSD program are set out at 51.166(r). This federal regulatory 
provision does not impose any particular time period for validity of a 
PSD permit. In addition, 52.21(r)(2) currently provides for extensions 
beyond the given eighteen-month period, if an applicant makes a 
satisfactory showing that an extension is justified. Thus, EPA believes 
that the state regulatory provision cited by the commenter is 
consistent with both 51.166(r) and 52.21(r)(2). Given this conclusion, 
EPA does not consider this a basis for disapproval of the North Dakota 
PSD program revision or the section 110(a)(2)(D) submission.
    Comment No. 9--WG also opposed EPA's proposed approval of the North 
Dakota section 110(a)(2)(D) SIP submission with respect to PSD 
requirements for the 1997 8-hour ozone and PM2.5 NAAQS 
because the submission did not address other, more recent NAAQS. WG 
noted that the current EPA-approved version of the North Dakota SIP at 
NDAC 33-15-02 does not incorporate all current NAAQS, including the 
2006 PM2.5 NAAQS, the 2008 ozone NAAQS, and the 2010 
NO2 NAAQS. WG stated its concern that the failure to 
incorporate the latest NAAQS implies that these NAAQS will not be 
addressed in permitting and planning determinations by the state.
    EPA Response--EPA disagrees with the commenter on this point. 
First, in this action, EPA is approving the North Dakota interstate 
transport SIP for the 1997 8-hour ozone and PM2.5 NAAQS; EPA 
is also approving a revision to North Dakota's PSD program. WG does not 
explain how a failure to incorporate the current NAAQS in the state 
ambient air quality standards is relevant to EPA's action on the North 
Dakota interstate transport SIP for the 1997 8-hour ozone and 
PM2.5 NAAQS. Thus, the comment does not give grounds for 
disapproval of the interstate transport SIP for the NAAQS at issue in 
this rulemaking.
    Furthermore, as noted in the proposal for this action, EPA has 
included the revision to North Dakota's PSD program in this action to 
address an issue specifically mentioned in the 2006 guidance. The 
guidance recommended that in order to satisfy the PSD requirement of 
110(a)(2)(D)(i), the state's interstate transport SIP, or existing SIP, 
should meet the requirements of the Phase II implementation rule for 
the 1997 8-hour ozone NAAQS. In particular, this means the state's SIP 
should identify NOX as a precursor to ozone, and the SIP 
revision submitted by North Dakota has done so. Thus, the current NAAQS 
are not relevant to this action.
    Finally, EPA disagrees that approval of this SIP submission implies 
that North Dakota will not take appropriate required actions with 
respect to other,

[[Page 31294]]

more recent, NAAQS. Consistent with the requirements of the CAA and 
applicable regulations, EPA expects North Dakota to consider other more 
recent NAAQS in permitting decisions. As additional SIP revisions are 
necessary, EPA anticipates that the state will comply, as indeed it has 
in this very action with respect to necessary revisions for the 1997 8-
hour ozone NAAQS.
    Comment No. 10--WG asserted that EPA's proposed approval was based 
on a ``flawed legal standard.'' According to WG, EPA erred in the 
proposal by explaining that various factual or technical assessments 
indicate that it is ``highly unlikely'' that emissions from North 
Dakota sources significantly contribute to violations of the 1997 8-
hour ozone NAAQS, or to violations of the 1997 PM2.5 NAAQS 
in other states. WG's position is that EPA cannot approve a SIP 
submission based upon ``unlikelihood'' because CAA Section 
110(a)(2)(D)(i)(I) prohibits emissions that contribute significantly to 
nonattainment in other States and does not allow EPA to approve SIPs 
simply because a state's emissions are ``unlikely'' to contribute 
significantly to nonattainment.
    EPA Response--EPA disagrees with WG's characterization of EPA's 
analysis and WG's interpretation of the statutory requirements. First, 
EPA notes that the discussion in the proposal was intended to present 
the various factual and technical considerations available to assess 
whether there is or is not significant contribution to nonattainment in 
other states as a result of emissions from North Dakota sources. Given 
that these assessments are not individually definitive or outcome 
determinative, EPA believes that it is entirely appropriate to present 
and describe the relative probative value of the various considerations 
accurately. Second, EPA notes that all such technical evaluations are 
by their nature subject to some degree of uncertainty. Indeed, the 
modeling that WG elsewhere contends should be the sole method for 
evaluating interstate transport is itself but one means of evaluating 
the real world impacts of emissions in light of meteorological 
conditions, wind direction, and other such variables, and produces a 
result that is itself subject to some degree of uncertainty. Third, EPA 
believes that it was also appropriate to describe the various factual 
and technical considerations and whether they indicated a 
``likelihood'' of significant contribution to nonattainment in another 
state because the proposal was seeking comment from the public upon 
whether these considerations together supported a determination of no 
such significant contribution. EPA did not receive comments that 
persuade the Agency that there is such significant contribution, and 
thus in today's final action EPA is making a final regulatory 
determination that North Dakota emissions sources do not significantly 
contribute to violations of the 1997 8-hour ozone NAAQS, or to 
violations of the 1997 PM2.5 NAAQS in any other state, for 
the reasons explained elsewhere in this notice. In other words, EPA has 
concluded that the existing SIP for North Dakota already contains 
adequate provisions to prevent emission from North Dakota sources from 
significantly contributing to violations of the 1997 8-hour ozone 
NAAQS, or to violations of the 1997 PM2.5 NAAQS in other 
states and is therefore approving North Dakota's submission for this 
purpose.
    Comment No. 11--WG argued that North Dakota and EPA did not 
appropriately assess impacts to nonattainment in downwind states. 
According to WG, North Dakota failed to assess significance of downwind 
impacts in accordance with EPA guidance and precedent. Although this is 
unclear from the comment, WG evidently believes that EPA's applicable 
guidance for this purpose appears only in the 1998 NOX SIP 
call. WG asserts that, based on the precedent of the NOX SIP 
Call, the following issues need to be addressed in determining whether 
or not an area is significantly contributing to nonattainment in 
downwind States: (a) The overall nature of the ozone problem; (b) the 
extent of downwind nonattainment problems to which upwind States' 
emissions are linked; (c) the ambient impact of the emissions from 
upwind States' sources on the downwind nonattainment problems; and (d) 
the availability of high cost-effective control measures for upwind 
emissions. (63 FR 57356-57376, October 27, 1998).
    EPA Response--EPA disagrees with WG on this point. Section 
110(a)(2)(D) does not explicitly specify how states or EPA should 
evaluate the existence of, or extent of, interstate transport and 
whether that interstate transport is of sufficient magnitude to 
constitute ``significant contribution to nonattainment'' as a 
regulatory matter. The statutory language is ambiguous on its face and 
EPA must reasonably interpret that language when it applies it to 
factual situations before the Agency.
    EPA agrees that the NOX SIP Call is one rulemaking in 
which EPA evaluated the existence of, and extent of, interstate 
transport. In that action, EPA developed an approach that allowed the 
Agency to evaluate whether there was significant contribution to ozone 
nonattainment across an entire region that was comprised of many 
states. That approach included regional scale modeling and other 
technical analyses that EPA deemed useful to evaluate the issue of 
interstate transport on that geographic scale and for the facts and 
circumstances at issue in that rulemaking. EPA does not agree, however, 
that the approach of the NOX SIP Call is necessarily the 
only way that states or EPA may evaluate the existence of, and extent 
of, interstate transport in all situations, and especially in 
situations where the state and EPA are evaluating the question on a 
state by state basis, and in situations where there is not evidence of 
widespread interstate transport.
    Indeed, EPA issued specific guidance making recommendations to 
states about how to address section 110(a)(2)(D) in SIP submissions for 
the 8-hour ozone and PM2.5 NAAQS. EPA issued this guidance 
document, entitled ``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 National 
Ambient Air Quality Standards'' on August 15, 2006.\6\ This guidance 
document postdated the NOX SIP Call, and was developed by 
EPA specifically to address SIP submissions for the 1997 8-hour ozone 
and PM2.5 NAAQS.
---------------------------------------------------------------------------

    \6\ Memorandum from William T. Harnett entitled 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 National Ambient Air Quality Standards 
(Aug. 15, 2006) (``2006 Guidance''); p. 3. An electronic copy is 
available for review at the regulations.gov web site as Document ID 
No. EPA-R08-OAR-2007-1032.0004.1.
---------------------------------------------------------------------------

    Within that 2006 guidance document, EPA notes that it explicitly 
stated its view that the ``precise nature and contents of such a 
submission [are] not stipulated in the statute'' and that the contents 
of the SIP submission ``may vary depending upon the facts and 
circumstances related to the specific NAAQS.'' \7\ Moreover, within 
that guidance, EPA expressed its view that ``the data and analytical 
tools available'' at the time of the SIP submission ``necessarily 
affect[] the content of the required submission.'' \8\ To that end, EPA 
specifically recommended that states located within the geographic 
region covered by the ``Clean Air Interstate Rule (CAIR),'' comply with 
section 110(a)(2)(D) for the 1997 8-hour

[[Page 31295]]

ozone and PM2.5 NAAQS by complying with CAIR itself. For 
states outside the CAIR rule region, however, EPA recommended that 
states develop their SIP submissions for section 110(a)(2)(D) 
considering relevant information.
---------------------------------------------------------------------------

    \7\ Id. at 3.
    \8\ Id.
---------------------------------------------------------------------------

    EPA explicitly recommended that relevant information for section 
110(a)(2)(D) submissions addressing significant contribution to 
nonattainment ``might include, but is not limited to, information 
concerning emissions in the State, meteorological conditions in the 
State, the distance to the nearest nonattainment area in another State, 
reliance on modeling conducted by EPA in determining that such State 
should not be included within the ambit of the CAIR, or such other 
information as the State considers probative on the issue of 
significant contribution.'' \9\ In addition, EPA recommended that 
states might elect to evaluate significant contribution to 
nonattainment using relevant considerations comparable to those used by 
EPA in CAIR, including evaluating impacts as of an appropriate year 
(such as 2010) and in light of the cost of control to mitigate 
emissions that resulted in significant contribution.
---------------------------------------------------------------------------

    \9\ Id. at 5.
---------------------------------------------------------------------------

    WG did not acknowledge or discuss EPA's actual guidance for section 
110(a)(2)(D) SIP submissions for the 1997 8-hour ozone and 
PM2.5 NAAQS, and thus it is unclear whether WG was aware of 
it. In any event, EPA believes that the North Dakota submission and 
EPA's evaluation of it was consistent with EPA's guidance for the 1997 
8-hour ozone and PM2.5 NAAQS. For example, as discussed in 
the proposal notice, the State and EPA considered information such as 
monitoring data in North Dakota and downwind states, geographical and 
meteorological information, and technical studies of the nature and 
sources of nonattainment problems in various downwind states. These are 
among the types of information that EPA recommended and that EPA 
considers relevant. Thus, EPA has concluded that the state's 
submission, and EPA's evaluation of that submission, meet the 
requirements of section 110(a)(2)(D) and are consistent with applicable 
guidance.
    Finally, EPA notes that the considerations the Agency recommended 
to States in the 2006 Guidance document are consistent with the 
concepts that WG enumerated from the NOX SIP Call context: 
(a) The overall nature of the ozone problem; (b) the extent of downwind 
nonattainment problems to which upwind State's emissions are linked; 
(c) the ambient impact of the emissions from upwind States' sources on 
the downwind nonattainment problems; and (d) the availability of high 
cost-effective control measures for upwind emissions. The only 
distinction in the case of the North Dakota submission at issue here 
would be that because the available evidence indicates that there is 
very little contribution from emissions from North Dakota sources to 
nonattainment in other states, it is not necessary to advance to the 
final step and evaluate whether the cost of controls for those sources 
is above or below a certain cost of control as part of determining 
whether the contribution constitutes ``significant contribution to 
nonattainment'' for regulatory purposes, as was necessary in the 
NOX SIP Call and in CAIR.
    Comment No. 12--WG argued that EPA's assessment that North Dakota 
will not significantly contribute to nonattainment of the ozone NAAQS 
in downwind States is based primarily on modeling prepared in 
conjunction with CAIR, and yet ``EPA admits that CAIR only addressed 
PM2.5 impacts.''
    EPA Response--EPA agrees with WG that CAIR evaluated only 
PM2.5 impacts for North Dakota. However, EPA disagrees that 
the CAIR ozone modeling results are irrelevant to this action: as the 
NPR made clear, it is actually the CAIR modeling analyses for ozone 
transport from Minnesota--not North Dakota--that EPA considered as 
evidence in this action.\10\ Furthermore, we do not think that within 
the proposed rule of March 31, 2010, EPA suggested that the assessment 
of impacts from North Dakota's emissions to nonattainment of the ozone 
NAAQS in downwind States was based primarily on modeling prepared in 
conjunction with CAIR. Instead, EPA made clear that the CAIR modeling 
analysis results for Minnesota, considered in combination with 
emissions levels in Minnesota and North Dakota, and their respective 
distances from the Illinois/Wisconsin nonattainment counties, was only 
one piece of relevant evidence in EPA's weight-of-evidence 
determination. The comment seems to reflect a misreading of our 
proposed rule action, or a misinterpretation of one of the pieces of 
evidence in our technical analysis. Thus, EPA does not see in its 
proposed rule the contradiction alleged by this comment.
---------------------------------------------------------------------------

    \10\ Specifically, the relevant portion of our proposed rule 
reads: ``The CAIR modeling domain for 8-hour ozone transport 
analysis included only the eastern half of North Dakota, and the 
CAIR modeling analysis did not determine whether NOX 
emissions from North Dakota sources contributed significantly to 
ozone nonattainment in any downwind states. However, the CAIR 
modeling analysis results for Minnesota provide us the opportunity 
to draw inferences about ozone contribution from North Dakota 
sources to nonattainment in the Illinois/Wisconsin area. It must be 
noted that Minnesota is nearly half as distant from this 
nonattainment area as North Dakota (400 miles as compared with 700), 
and that to reach the Illinois/Wisconsin nonattainment area, ozone 
transport winds from Minnesota would have to have a northwesterly 
orientation similar to that necessary for substantial ozone 
transport from North Dakota. In addition, the CAIR modeling analysis 
estimated the Minnesota's NOX emissions for the 2010 base 
year to be approximately twice as large as the NOX 
emissions from North Dakota's sources (381,500 as compared with 
182,800 tons.) Finally, the CAIR analysis determined that emissions 
from Minnesota were below the initial threshold for including states 
in CAIR. In light of this CAIR determination, and of Minnesota's 
larger NOX emissions and shorter distance to the 
nonattainment area, it is plausible to conclude that NOX 
emissions from North Dakota sources are not likely to contribute 
significantly to nonattainment of the 1997 8-hour ozone standard in 
the Illinois and Wisconsin counties along the southwestern shores of 
Lake Michigan.'' 75 FR 16030.
---------------------------------------------------------------------------

    Comment No. 13--WG reiterated its concern that the North Dakota 
section 110(a)(2)(D) submission was deficient because it did not 
strictly follow WG's summary of the structure of the analysis of 
interstate transport in the NOX SIP Call: (a) The overall 
nature of the ozone problem; (b) the extent of downwind nonattainment 
problems to which upwind States' emissions are linked; (c) the ambient 
impact of the emissions from upwind States' sources on the downwind 
nonattainment problems; and (d) the availability of high cost-effective 
control measures for upwind emissions.
    EPA Response--EPA disagrees with WG's view that any analysis of 
interstate transport must follow a specific formulaic structure to be 
approvable. As noted above, EPA issued specific guidance to states 
making recommendations for section 110(a)(2)(D) SIP submissions for the 
1997 8-hour ozone and PM2.5 NAAQS. Within that guidance, EPA 
recommended various types of information that states might wish to 
consider in the process of evaluating whether their sources contributed 
significantly to nonattainment in other states. EPA has concluded that 
the submission from North Dakota, augmented by EPA's own analysis, 
sufficiently establishes that North Dakota sources do not significantly 
contribute to violations of the 1997 8-hour ozone and PM2.5 
NAAQS in other states. As noted above, EPA believes that the state's 
submission, and EPA's analysis of it, address the same conceptual 
considerations that the commenter advocated.
    Comment No. 14--WG asserted that North Dakota and EPA provided ``no 
analysis'' of the contribution from North Dakota to downwind states and 
no

[[Page 31296]]

``actual assessment'' of the significance of any such contribution.
    EPA Response--EPA disagrees with WG's position. WG again assumes 
that section 110(a)(2)(D) explicitly requires the type of modeling 
analysis that the commenter advocates throughout its comments. Because 
WG apparently views the NOX SIP Call as the applicable 
guidance, WG contends that any analytical approach that is not 
identical to that approach is impermissible. In addition, WG overlooks 
the fact that in other actions based upon section 110(a)(2)(D), EPA has 
also used a variety of analytical approaches, short of modeling, to 
evaluate whether specific states are significantly contributing to 
violations of the NAAQS in another state (e.g., the west coast states 
that EPA concluded should not be part of the geographic region of the 
CAIR rule based upon qualitative factors, and not by the zero out 
modeling EPA deemed necessary for some other states).
    In the proposed approval, EPA explained that other forms of 
available information were sufficient to make the determination that 
there is no significant contribution from North Dakota sources to 
downwind nonattainment of the 1997 8-hour ozone NAAQS. As stated in the 
proposal:

    EPA's evaluation of whether emissions from North Dakota 
contribute significantly to the ozone nonattainment in these areas 
is based on an examination of how geographical and meteorological 
factors affect transport from North Dakota to the two areas noted 
above. Our approach does not rely on a quantitative determination of 
North Dakota's contribution, as EPA did for other states in its CAIR 
rulemaking, but on a weight-of-evidence analysis based on 
qualitative assessments and estimates of the relevant factors. While 
conclusions reached for each of the factors considered in the 
following analysis are not in and by themselves determinative, 
consideration of the likely effect of all factors provides a 
reliable qualitative conclusion on whether North Dakota's emissions 
are likely to contribute significantly to nonattainment in the DMA/
NFR area and the Illinois/Wisconsin Counties.\11\
---------------------------------------------------------------------------

    \11\ 75 FR 16030.

    EPA acknowledged that the various forms of information considered 
in the proposal (such as distance, orientation of surface and regional 
transport winds, back trajectory analyses, monitoring data) were not 
individually outcome determinative, but concluded that when taken 
together served to establish that North Dakota sources do not 
significantly contribute to downwind nonattainment of the 1997 8-hour 
ozone NAAQS in other states. Thus, contrary to WG's assertion, EPA did 
perform an ``analysis'' and an ``assessment'' that was a reasonable 
basis for its conclusion that emissions from North Dakota do not 
contribute significantly to downwind ozone nonattainment, using a 
combination of quantitative data and qualitative analyses. EPA does not 
agree that only the type of analysis advocated by WG could adequately 
evaluate the issue and support a rational determination in this 
instance.
    Comment No. 15--WG objected to EPA's proposed approval because 
North Dakota assessed impacts in downwind states by considering 
monitoring data in those states as a means of evaluating significant 
contribution to nonattainment. In other words, WG is concerned that 
North Dakota did not assess impacts in areas that have no monitor. WG 
likewise objected to EPA's ``endorsement'' of this approach. WG argued 
that this reliance on monitor data is inconsistent with both section 
110(a)(2)(D) and with EPA's guidance, by which the commenter evidently 
means the NOX SIP Call. In support of this assertion, WG 
quoted from the NOX SIP Call proposal in which EPA addressed 
the proper interpretation of the statutory phrase ``contribute 
significantly to nonattainment:''

    The EPA proposes to interpret this term to refer to air quality 
and not to be limited to currently-designated nonattainment areas. 
Section 110(a)(2)(D) does not refer to ``nonattainment areas,'' 
which is a phrase that EPA interprets to refer to areas that are 
designated nonattainment under section 107 (section 107 
(d)(1)(A)(I)).

According to WG, this statement, and similar ones in the context of the 
final NOX SIP Call rulemaking, establish that States and EPA 
cannot utilize monitoring data to evaluate the existence of, and extent 
of, interstate transport. Furthermore, WG interprets the reference to 
``air quality'' in these statements to support its contention, 
amplified in later comments, that EPA must evaluate significant 
contribution in areas in which there is no monitored nonattainment.
    EPA Response--EPA disagrees with WG's arguments. First, WG 
misunderstands the point that EPA was making in quoted statement from 
the NOX SIP Call proposal (and that EPA has subsequently 
made in the context of CAIR). When EPA stated that it would evaluate 
impacts on air quality in downwind states, independent of the current 
formal ``designation'' of such downwind states, it was not referring to 
air quality in the absence of monitor data. EPA's point was that it was 
inappropriate to wait for either initial designations of nonattainment 
for a new NAAQS under section 107(d)(1), or for a redesignation to 
nonattainment for an existing NAAQS under section 107(d)(3), before EPA 
could assess whether there is significant contribution to nonattainment 
of a NAAQS in another state.
    For example, in the case of initial designations, section 107(d) 
contemplates a process and timeline for initial designations that could 
well extend for two or three years following the promulgation of a new 
or revised NAAQS. By contrast, section 110(a)(1) requires states to 
make SIP submissions that address section 110(a)(2)(D) and interstate 
transport ``within 3 years or such shorter period as the Administrator 
may prescribe'' of EPA's promulgation of a new or revised NAAQS. This 
schedule does not support a reading of section 110(a)(2)(D) that is 
dependent upon formal designations having occurred first. This is a key 
reason why EPA determined that it was appropriate to evaluate 
interstate transport based upon monitor data, not designation status, 
in the CAIR rulemaking.
    WG's misunderstanding of EPA's statement concerning designation 
status evidently caused WG to believe that EPA's assessment of 
interstate transport in the NOX SIP Call was not limited to 
evaluation of downwind areas with monitors. This is simply incorrect. 
In both the NOX SIP Call and CAIR, EPA evaluated significant 
contribution to nonattainment as measured or predicted at monitors. For 
example, in the technical analysis for the NOX SIP Call, EPA 
specifically evaluated the impacts of emissions from upwind states on 
monitors located in downwind states. The NOX SIP Call did 
not evaluate impacts at points without monitors, nor did the CAIR 
rulemaking. EPA believes that this approach to evaluating significant 
contribution is correct under section 110(a)(2)(D), and EPA's general 
approach to this threshold determination has not been disturbed by the 
courts.\12\
---------------------------------------------------------------------------

    \12\ Michigan v. U.S. EPA, 213 F.3d 663, 674-681 (D.C. Cir. 
2000); North Carolina v. EPA, 531 F.3d 896, 913-916 (D.C. Cir. 2008) 
(upholding EPA approach to determining threshold despite remanding 
other aspects of CAIR).
---------------------------------------------------------------------------

    Finally, EPA disagrees with WG's argument that the assessment of 
significant contribution to downwind nonattainment must include 
evaluation of impacts on non-monitored areas. First, neither section 
110(a)(2)(D)(i)(I) provisions, nor the EPA guidance issued for the 1997 
8-hour ozone NAAQS on August 15, 2006 support WG's position, as neither 
refers to any requirement or recommendation to assess air quality in

[[Page 31297]]

non-monitored areas.\13\ The same focus on monitored data as a means of 
assessing interstate transport is found in the NOX SIP Call 
and in CAIR. An initial step in both the NOX SIP Call and 
CAIR was the identification of areas with current monitored violations 
of the ozone and/or PM2.5 NAAQS.\14\ The subsequent modeling 
analyses for NAAQS violations in future years (2007 for the SIP Call 
and 2010 for CAIR) likewise evaluated future violations at monitors in 
areas identified in the initial step. Thus, WG is simply in error that 
EPA has not previously evaluated the presence and extent of interstate 
transport under section 110(a)(2)(D) by focusing on monitoring data. 
Indeed, such monitoring data was at the core of both of these efforts. 
In neither of these rulemakings did EPA evaluate significant 
contribution to nonattainment in areas in which there was no monitor. 
This is reasonable and appropriate, because data from a properly placed 
federal reference method monitor is the way in which EPA ascertains 
that there is a violation of the 1997 8-hour ozone or PM2.5 
NAAQS in a particular area. Put another way, in order for there to be 
significant contribution to nonattainment for the 1997 8-hour ozone or 
PM2.5 NAAQS, there must be a monitor with data showing a 
violation of that NAAQS. EPA has concluded that by considering data 
from monitored areas, its assessment of whether emissions from North 
Dakota contribute significantly to ozone or PM2.5 
nonattainment in downwind States is consistent with the 2006 Guidance, 
and with the approach used by both the CAIR rule and the NOX 
SIP Call.
---------------------------------------------------------------------------

    \13\ 2006 Guidance, p. 5.
    \14\ ``Based on this approach, we predicted that in the absence 
of additional control measures, 47 counties with air quality 
monitors [emphasis ours] would violate the 8-hour ozone NAAQS in 
2010. * * *'' From the CAIR proposed rule of January 30, 2004 (69 FR 
4566, 4581). The NOX SIP call proposed rule action reads: 
``* * * For current nonattainment areas, EPA used air quality data 
for the period 1993 through 1995 to determine which counties are 
violating the 1-hour and/or 8-hour NAAQS. These are the most recent 
3 years of fully quality assured data which were available in time 
for this assessment,'' 62 FR 60336.
---------------------------------------------------------------------------

    Comment No. 16--In support of its comments that EPA should assess 
significant contribution to nonattainment in nonmonitored areas, WG 
argued that existing modeling performed by another organization 
``indicates that large areas of neighboring states will likely violate 
the ozone NAAQS.'' According to WG, these likely ``violations'' of the 
ozone NAAQS were predicted for the year 2018, as reflected in a slide 
from a July 30, 2008 presentation before the Western Regional Air 
Partnership (``Review of Ozone Performance in WRAP Modeling and 
Relevant to Future Regional Ozone Planning''). WG asserted that: 
``Slide 28 of this presentation displays projected 4th highest 8-hour 
ozone reading for 2018 and indicates that air quality throughout large 
portions of the West will exceed and/or violate the 1997 ozone NAAQS. * 
* *'' \15\ In short, WG argues that modeling performed by the WRAP 
establishes that there will be violations of the 1997 8-hour ozone 
NAAQS in 2018 in non-monitored areas Western states.
---------------------------------------------------------------------------

    \15\ The presentation is available for review as Document ID 
 EPA-R08-OAR-2007-1032-0007.8 at Regulations.gov, Docket ID 
 EPA-R08-OAR-2009-0282.
---------------------------------------------------------------------------

    EPA Response--EPA disagrees with this comment on several grounds. 
First, as explained in response to other comments, EPA does not agree 
that it is appropriate to evaluate significant contribution to 
nonattainment for the 1997 8-hour ozone NAAQS by modeling ambient 
levels in areas where there is no monitor to provide data to establish 
a violation of the NAAQS in question. Section 110(a)(2)(D) does not 
require such an approach, EPA has not taken this approach in the 
NOX SIP Call or other rulemakings under section 
110(a)(2)(D), and EPA's prior analytical approach has not been 
disturbed by the courts.
    Second, WG's own description of the ozone concentrations predicted 
for the year 2018 as projecting ``violations'' of the ozone NAAQS is 
inaccurate. Within the same sentence, quoted above, slide 28 is 
described as displaying the projected 4th max ozone reading for the 
year 2018, and as indicating that ``* * * air quality * * * will exceed 
or violate [our emphasis] the 1997 ozone NAAQS.'' By definition, a one 
year value of the 4th max above the NAAQS only constitutes an 
exceedance of the NAAQS; to constitute a violation of the 1997 8-hour 
ozone NAAQS, the standard must be exceeded for three consecutive years 
at the same monitor. Thus, even if the WRAP presentation submitted by 
WG were technically sound, the conclusion drawn from it by WG is 
inaccurate and does not support its claim of projected violations of 
the NAAQS in western States south and west of North Dakota.
    EPA has also reviewed the WRAP presentation submitted by WG, and 
believes that there was a substantial error in the WRAP modeling 
software that led to overestimation of ground level ozone 
concentrations. A recent study conducted by Environ for the Four 
Corners Air Quality Task Force (FCAQTF; Stoeckenius et al., 2009) has 
demonstrated that excessive vertical transport in the CMAQ and CAMx 
models over high terrain was responsible for overestimated ground level 
ozone concentrations due to downward transport of stratospheric 
ozone.\16\ Environ has developed revised vertical velocity algorithms 
in a new version of CAMx that eliminated the excessive downward 
transport of ozone from the top layers of the model. This revised 
version of the model is now being used in a number of applications 
throughout high terrain areas in the West. In conclusion, EPA believes 
that this key inadequacy of the WRAP model, noted above, makes it 
inappropriate support for WG's concerns about large expanses of 8-hour 
ozone nonattainment areas projected for 2018 in areas without monitors.
---------------------------------------------------------------------------

    \16\ Stoeckenius, T.E., C.A. Emery, T.P. Shah, J.R. Johnson, 
L.K. Parker, A.K. Pollack, 2009. ``Air Quality Modeling Study for 
the Four Corners Region.'' Prepared for the New Mexico Environment 
Department, Air Quality Bureau, Santa Fe, NM, by ENVIRON 
International Corporation, Novato, CA.
---------------------------------------------------------------------------

    Finally, it must be noted that even if the ozone exceedances 
predicted for the year 2018 were based on a sound modeling analysis, 
even the closest areas showing exceedances are several hundred miles 
southwest of North Dakota and, as indicated in our proposed rule, the 
northeasterly winds required for ozone transport from North Dakota to 
these areas are a rarity (75 FR 16030).
    Comment No. 17--As additional support for its assertion that EPA 
should require modeling to assess ambient levels in unmonitored 
portions of other States, WG relied on an additional study entitled the 
``Uinta Basin Air Quality Study (UBAQS).'' The commenter argued that 
the UBAQS study further supports its concern that limiting the 
evaluation of downwind impacts only to areas with monitors fails to 
assess ozone nonattainment in non-monitored areas. According to the 
commenter, UBAQS modeling results show that: (a) The Wasatch front 
region is currently exceeding and will exceed in 2012 the 1997 8-hour 
ozone NAAQS; and (b) based on 2005 meteorological data, portions of the 
four counties in the southwest corner of Utah are also currently in 
nonattainment and will be in nonattainment in 2012.\17\
---------------------------------------------------------------------------

    \17\ The southwestern area referred to by the commenter includes 
portions of Washington, Iron, Kane, and Garfield Counties.
---------------------------------------------------------------------------

    EPA Response--As noted above, EPA does not agree that it is 
appropriate to assess significant contribution to nonattainment for the 
1997 8-hour

[[Page 31298]]

ozone NAAQS in the way advocated by WG. Even taking the UBAQS modeling 
results at their face value, however, EPA does not agree that the 8-
hour ozone nonattainment (current and projected) in the Wasatch Front 
Range area supports the commenter's concerns about the need to evaluate 
the possibility of significant contribution to nonattainment in non-
monitored areas. EPA sees several problems with the commenter's 
interpretation of the UBAQS analysis results for counties in Utah's 
southwestern corner: ``based on 2005 meteorological data, portions of 
Washington, Iron, Kane, and Garfield Counties are also in nonattainment 
and will be in nonattainment in 2012.''
    First, WG's interpretation of the predicted ozone concentrations 
shown in Figures 4-3a and 4-3b (pages 5 and 6 of the comment letter) is 
inaccurate. A close review of the legend in these figures indicates 
that the highest ozone concentrations predicted by the model for 
portions of the counties noted above are somewhere between 81.00 and 
85.99 ppb, but a specific concentration is not provided. If the ozone 
concentration is actually predicted to be smaller than or equal to 84.9 
ppb, then the area is attaining; if it is predicted as greater than 
84.9 ppb then it is not attaining. This means that current and 
predicted design values for the southwestern Utah area identified in 
Figures 4-3a and 4-3b could both be in attainment or both in 
nonattainment, or one of them in attainment and the other in 
nonattainment, for the 1997 8-hour ozone NAAQS.
    Second, even if the design values predicted for these unmonitored 
areas were at the top of the 81.00-85.99 ppb range, their reliability 
would remain questionable. The UBAQS itself identifies and illustrates 
major shortcomings of its modeling analysis, only to neglect assessing 
the impact of these shortcomings on the modeling results.\18\ The study 
deviates in at least two significant ways from EPA's 2007 guidance on 
SIP modeling.\19\ One issue is the UBAQS modeling reliance on fewer 
than the five years of data recommended by EPA to generate a current 8-
hour ozone design value (DVC). UBAQS relaxed this requirement so that 
sites with as little as 1 year of data were included as DVCs in the 
analysis. The other issue is the computation of the relative responsive 
factor (RRF), which directly affects the modeling's future design value 
(DVF).\20\ Again due to unavailability of data satisfying EPA's 
recommendation that the RRF be based on a minimum of five days of ozone 
concentrations above 85 ppb, UBAQS modeling uses RRFs based on one or 
more days of ozone concentrations above 70 ppb.\21\ EPA concludes that 
the modeling analysis results used by the WG are unreliable for 
projecting non-attainment status and therefore do not support its 
comments.
---------------------------------------------------------------------------

    \18\ See ``UBAQS,'' pages 4-27 to 4-29.
    \19\ EPA. 2007. Guidance on the Use of Models and other Analyses 
for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5 
and Regional Haze. Office of Air Quality Planning and Standards, Air 
Modeling Group. Research Triangle Park, North Carolina (https://www.epa.gov/scram001/guidance/guide/final-03-pm-rh-guidance.pdf).
    \20\ DVC x RRF = DVF.
    \21\ See UBAQS, p. 4-28.
---------------------------------------------------------------------------

    Finally, the predicted attainment status of unmonitored areas in 
the southwestern corner of Utah is not relevant to our assessment of 
whether emissions from North Dakota contribute significantly to 
downwind ozone nonattainment. The counties identified that draw the 
commenter's attention are almost a 1,000 miles from Bismarck, North 
Dakota, in a southwestern direction. As indicated in our response to 
the previous comment, the northeasterly winds required for ozone 
transport from North Dakota to these areas are a rarity.
    Comment No. 18--In support of its arguments that EPA should not 
limit assessment of significant contribution to