Approval and Promulgation of Implementation Plans; New Mexico; Interstate Transport of Pollution, 33174-33190 [2010-13686]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 75, Number 112 (Friday, June 11, 2010)]
[Rules and Regulations]
[Pages 33174-33190]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-13686]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R06-OAR-2007-0993; FRL-9160-2]


Approval and Promulgation of Implementation Plans; New Mexico; 
Interstate Transport of Pollution

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: EPA is approving a portion of a State Implementation Plan 
(SIP) submitted by the State of New Mexico for the purpose of 
addressing the ``good neighbor'' provisions of the Clean Air Act (CAA) 
section 110(a)(2)(D)(i) for the 1997 ozone National Ambient Air Quality 
Standard (NAAQS) and the 1997 PM2.5 NAAQS. This SIP revision 
satisfies a portion of the State of New Mexico's obligation to submit a 
SIP that demonstrates that adequate provisions are in place to prohibit 
air emissions from adversely affecting another state's air quality 
through interstate transport. This rulemaking action is being taken 
under section 110 of the CAA and addresses one element of CAA section 
110(a)(2)(D)(i), which pertains to prohibiting air pollutant emissions 
from within New Mexico from contributing significantly to nonattainment 
of the 1997 8-hour ozone and PM2.5 NAAQS in any other state.

DATES: This final rule will be effective July 12, 2010.

ADDRESSES: EPA has established a docket for this action under Docket 
Identification No. EPA-R06-OAR-2007-0993. All documents in the docket 
are listed at www.regulations.gov. Although listed in the index, some 
information is not publicly available, e.g., Confidential Business 
Information 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 
Planning Section (6PD-L), Environmental Protection Agency, 1445 Ross 
Avenue, Suite 700, Dallas, Texas 75202-2733. The file will be made 
available by appointment for public inspection in the Region 6 Freedom 
of Information Act (FOIA) Review Room between the hours of 8:30 a.m. 
and 4:30 p.m. weekdays except for legal holidays. Contact the person 
listed in the FOR FURTHER INFORMATION CONTACT paragraph below or Mr. 
Bill Deese at 214-665-7253 to make an appointment. If possible, please 
make the appointment at least two working days in advance of your 
visit. There will be a 15 cent per page fee for making photocopies of 
documents. On the day of the visit, please check in at the EPA Region 6 
reception area at 1445 Ross Avenue, Suite 700, Dallas, Texas.

FOR FURTHER INFORMATION CONTACT: Emad Shahin, Air Planning Section 
(6PD-L), Environmental Protection

[[Page 33175]]

Agency, Region 6, 1445 Ross Avenue, Suite 700, Dallas, Texas 75202-
2733, telephone (214) 665-6717; fax number (214) 665-7263; e-mail 
address shahin.emad@epa.gov.

SUPPLEMENTARY INFORMATION: Throughout this document wherever ``we,'' 
``us,'' or ``our'' is used, we mean the EPA.

Outline

I. What action is EPA taking?
II. What is the background for this action?
III. What comments did EPA receive and how has EPA responded to 
them?
IV. Final Action
V. Statutory and Executive Order Reviews

I. What action is EPA taking?

    We are approving a portion of the submission from the State of New 
Mexico demonstrating that New Mexico has adequately addressed one of 
the required elements of the CAA section 110(a)(2)(D)(i), the element 
that prohibits air pollutant emissions from sources within a state from 
contributing significantly to nonattainment of the relevant NAAQS in 
any other state. We have determined that emissions from sources in New 
Mexico do not significantly contribute to nonattainment of the 1997 8-
hour ozone NAAQS or the 1997 PM2.5 NAAQS in any other state. 
Because emissions from sources in New Mexico do not significantly 
contribute to nonattainment in any other state, section 
110(a)(2)(D)(i)(I) does not require any substantive changes to New 
Mexico's SIP.
    The remaining three elements of section 110(a)(2)(D) are that a 
state's SIP contain adequate provisions to prevent: Interference with 
maintenance of the NAAQS in any other state; interference with measures 
required to prevent significant deterioration of air quality in any 
other state; and interference with measures required to protect 
visibility in any other state. EPA will evaluate the New Mexico SIP and 
SIP submissions for compliance with these other requirements of section 
110(a)(2)(D) for the 1997 8-hour ozone and 1997 PM2.5 NAAQS 
in future rulemakings.

II. What is the background for this action?

    On July 18, 1997, EPA promulgated new standards for 8-hour ozone 
and fine particulate matter (PM2.5). This action is being 
taken in response to the July 18, 1997 revision to the 8-hour ozone 
NAAQS and PM2.5 NAAQS. This action does not address the 
requirements for the 2006 PM2.5 NAAQS or the 2008 8-hour 
ozone NAAQS; those standards will be addressed in a later action.
    Section 110(a)(1) of the CAA requires states to submit SIPs to 
address a new or revised NAAQS within 3 years after promulgation of 
such standards, or within such shorter period as EPA may prescribe. 
Section 110(a)(2) lists the elements that such new SIPs must address, 
as applicable, including section 110(a)(2)(D)(i) which pertains to 
interstate transport of certain emissions. On August 15, 2006, EPA 
issued its ``Guidance for State Implementation Plan (SIP) Submission 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'' (2006 Guidance) for SIP submissions that states should use 
to address the requirements of section 110(a)(2)(D)(i). EPA developed 
this guidance to make recommendations to states for making submissions 
to meet the requirements of section 110(a)(2)(D) for the 1997 8-hour 
ozone NAAQS and 1997 PM2.5 NAAQS.
    On September 17, 2007, EPA received a SIP submission from the State 
of New Mexico to address the requirements of section 110(a)(2)(D)(i) 
for both the 1997 8-hour ozone NAAQS and 1997 PM2.5 NAAQS. 
The state based its submittal on EPA's 2006 Guidance. As explained in 
the 2006 Guidance, the ``good neighbor'' provisions in section 
110(a)(2)(D)(i) require each State to submit a SIP that contains 
adequate provisions to prohibit emissions from sources within that 
state from adversely affecting another state in the ways contemplated 
in the statute. Section 110(a)(2)(D)(i) contains four distinct 
requirements related to the impacts of interstate transport. In this 
rulemaking EPA is addressing only the requirement that pertains to 
preventing sources in the state from emitting pollutants in amounts 
which will contribute significantly to nonattainment of the 1997 8-hour 
ozone NAAQS and the 1997 PM2.5 NAAQS in any other state. In 
its submission, the State of New Mexico indicated that its current SIP 
is adequate to prevent such significant contribution to nonattainment 
in any other state, and thus no additional emissions controls are 
necessary at this time to alleviate interstate transport.
    On April 8, 2010, we published a direct final rule and a parallel 
proposal to approve the portion of New Mexico's SIP submission that 
addressed one element of the CAA section 110(a)(2)(D)(i), which 
pertains to prohibiting air pollutant emissions from within New Mexico 
from contributing significantly to nonattainment of the 1997 8-hour 
ozone and 1997 PM2.5 NAAQS in any other state (75 FR 17868). 
The direct final rule and proposal stated that if EPA received any 
relevant adverse comments during the public comment period ending on 
May 10, 2010, then EPA would withdraw the direct final rule and respond 
to such comments in a subsequent final action based upon the proposal. 
EPA received adverse comments during the comment period, and 
accordingly EPA withdrew the direct final rule on May 3, 2010 (75 FR 
23167). The April 8, 2010, proposal (75 FR 17894) provides the basis 
for today's final action.

III. What comments did EPA receive and how has EPA responded to them?

    EPA received three comment letters on the April 8, 2010, direct 
final rule and proposal. The letters can be found on the internet in 
the electronic docket for this action. To access the letters, please go 
to https://www.regulations.gov and search for Docket No. EPA-R06-OAR-
2007-0993, or contact the person listed in the FOR FURTHER INFORMATION 
CONTACT paragraph above. The discussion below addresses those comments 
and our response.

A. Comments From WildEarth Guardians

    Comment No. 1--The commenter argued that New Mexico and EPA did not 
appropriately assess impacts to nonattainment in downwind states. 
According to the commenter, New Mexico failed to assess the 
significance of downwind impacts in accordance with EPA precedent and 
refers to the 1998 NOX SIP Call.
    EPA Response--EPA disagrees with the commenter 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 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

[[Page 33176]]

rulemaking. EPA does not agree, however, that the approach of the 
NOX SIP Call is 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 with recommendations to states 
about how to address section 110(a)(2)(D) in SIP submissions for the 
1997 8-hour ozone 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.\1\ This guidance document postdated the 
NOX SIP Call, and was developed by EPA specifically to 
address SIP submissions for the 1997 8-hour ozone NAAQS.
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    \1\ 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.
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    Within the 2006 Guidance, 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.'' \2\ 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.'' \3\ To that end, EPA specifically 
recommended that states located within the geographic region covered by 
the Clean Air Interstate Rule (CAIR) \4\ comply with section 
110(a)(2)(D) for the 1997 8-hour ozone 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.
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    \2\ Id. at 3.
    \3\ Id.
    \4\ 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 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.'' \5\ 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 interstate transport.
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    \5\ Id. at 5.
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    The commenter did not acknowledge or discuss EPA's actual guidance 
for section 110(a)(2)(D) SIP submissions for the 1997 8-hour ozone 
NAAQS, and thus it is unclear whether the commenter was aware of it. In 
any event, EPA believes that the New Mexico submission and EPA's 
evaluation of it is consistent with EPA's guidance for the 1997 8-hour 
ozone NAAQS. For example, as discussed in the direct final notice, the 
State of New Mexico and EPA considered information such as monitoring 
data in other 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 are consistent with the concepts of the 
NOX SIP Call referenced by the commenter: (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 New Mexico submission at issue here would be that because the 
available evidence indicates that there is so very little contribution 
of emissions from New Mexico 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. 2--The commenter believes that New Mexico and EPA did 
not appropriately assess impacts to nonattainment in downwind states in 
terms of air quality. Specifically, the commenter objected to EPA's 
proposed approval because New Mexico assessed impacts in downwind 
states by considering only areas that had monitoring data as for 
evaluating significant contribution to nonattainment. In other words, 
the commenter is concerned that New Mexico did not assess impacts in 
areas that have no monitor. The commenter implied 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, the commenter 
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 the commenter, 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, the commenter 
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 the commenter's arguments. First, 
the commenter misunderstands the point that EPA was making in the 
quoted statement from the NOX SIP Call proposal (and that 
EPA has subsequently made in the context of

[[Page 33177]]

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.
    The commenter's misunderstanding of EPA's statement concerning 
designation status evidently caused the commenter 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.\6\
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    \6\ Michigan v. U.S. EPA, 213 F.3d 663, 674-681 (DC Cir. 2000); 
North Carolina v. EPA, 531 F.3d 896, 913-916 (DC Cir. 2008) 
(upholding EPA approach to determining threshold despite remanding 
other aspects of CAIR).
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    Finally, EPA disagrees with the commenter's argument that the 
assessment of significant contribution to downwind nonattainment must 
include evaluation of impacts on non-monitored areas. Neither section 
110(a)(2)(D)(i)(I) provisions, nor the 2006 Guidance EPA issued for the 
1997 8-hour ozone NAAQS, support the commenter's position, as neither 
refers to any explicit mandatory or recommended approach to assess air 
quality in non-monitored areas.\7\ The same focus on monitor 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.\8\ 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, 
the commenter 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 NAAQS or of the 1997 
PM2.5 NAAQS in a particular area.
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    \7\ 2006 Guidance, p. 5.
    \8\ ``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.'' See, 62 FR 60336.
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    EPA did not use photochemical modeling to determine if an area is 
violating the 1997 8-hour ozone or 1997 PM2.5 NAAQS to 
designate the area as nonattainment without supporting monitoring data. 
EPA's regulations for these NAAQS, the monitoring requirements for 
these NAAQS, and EPA's guidance for designations for these NAAQS 
provide for such designations for violating areas to be based only on 
monitoring data. In addition, this is reasonable for these particular 
NAAQS because photochemical models, while based on the best science 
available, only provide a best estimate of air quality. EPA's 2007 
modeling guidance \9\ recognizes that model results and projections 
will continue to have uncertainty.
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    \9\ EPA-454/B-07-002, April 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, available at https://www.epa.gov/scram001/guidance/guide/final-03-pm-rh-guidance.pdf.
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    Therefore, even if modeling analyses indicated violation of the 
1997 8-hour ozone NAAQS in other states, EPA would not make a 
determination that these areas should be designated nonattainment for 
these NAAQS without monitoring data in the area to support a 
determination of nonattainment. In summary, in order for there to be 
significant contribution to nonattainment for either of these specific 
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 New Mexico contribute 
significantly to ozone 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, and EPA modeling guidance.
    Comment No. 3--In support of its comments that EPA should assess 
significant contribution to nonattainment in nonmonitored areas, the 
commenter argued that existing modeling performed by another 
organization ``indicates that large areas of neighboring states will be 
likely to violate the ozone NAAQS.'' According to the commenter, 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'').\10\ In 
short, the commenter 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 of states adjacent to New Mexico.
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    \10\ The presentation is available for review as Document ID 
 EPA-R06-OAR-2007-0993-0008.9 at Regulations.gov, Docket ID 
 EPA-R06-OAR-2007-0993.
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    EPA Response--EPA disagrees with this comment on several grounds. 
First, EPA does not agree that it is appropriate when satisfying the 
requirements of Section 110(a)(2)(D) to evaluate significant 
contribution to nonattainment for the 1997 8-hour ozone NAAQS by 
modeling ambient

[[Page 33178]]

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, the commenter'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 fourth maximum ozone reading 
for the year 2018, and as indicating that ``* * * air quality * * * 
will exceed or violate [emphasis ours] the 1997 ozone NAAQS.'' By 
definition, a one year value of the fourth maximum above the NAAQS only 
constitutes an exceedance of the NAAQS; to constitute a violation of 
the 1997 8-hour ozone NAAQS, the average of the fourth high for three 
consecutive years at the same monitor must exceed the standard. Thus, 
even if the WRAP presentation submitted by the commenter were 
technically sound, the conclusion drawn from it by the commenter is 
inaccurate and does not support its claim of projected violations of 
the NAAQS in large areas (monitored or unmonitored) of New Mexico's 
neighboring states.
    Even if EPA believed that it was appropriate to use modeling to 
establish violations of the 1997 8-hour ozone NAAQS, EPA has reviewed 
the WRAP presentation submitted by the commenter, 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) \11\ 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.\12\ 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 the commenter's 
concerns about large areas of other states violating the 1997 8-hour 
ozone NAAQS projected for 2018 in areas without monitors.
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    \11\ This document is available for review at the 
regulations.gov Web site under Docket ID No. EPA-R06-OAR-2007-0993.
    \12\ 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,'' pp. ES-3, ES-4, 3-4, 3-12, 3-30, 5-1. 
Prepared for the New Mexico Environment Department, Air Quality 
Bureau, Santa Fe, NM, by ENVIRON International Corporation, Novato, 
CA.
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    Comment No. 4--As additional support for its assertion that EPA 
should require modeling to assess ambient levels in unmonitored 
portions of other states, the commenter relied on an additional study 
entitled the ``2009 Uinta Basin Air Quality Study'' (UBAQS). The 
commenter argued that the UBAQS further supports its concern that New 
Mexico and EPA, having limited the evaluation of downwind impacts only 
to areas with monitors, failed to assess ozone nonattainment in non-
monitored areas. According to the commenter, UBAQS modeling \13\ 
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 
southwestern corner of Utah are also currently in nonattainment and 
will be in nonattainment in 2012.\14\
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    \13\ In this action the expression ``UBAQS'' refers to the 
``FINAL REPORT UBAQS TECHNICAL REPORT'', June 30, 2009. The 
presentation is available for review as Document ID  EPA-
R06-OAR-2007-0993-0008.9 at regulations.gov, Docket ID  
EPA-R06-OAR-2007-0993.
    \14\ UBAQS. The southwestern area referred to by the commenter 
includes portions of Washington, Iron, Kane, and Garfield Counties.
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    EPA Response--As noted above, EPA does not agree that it is 
appropriate to assess significant contribution to nonattainment for the 
1997 8-hour ozone NAAQS in the way advocated by the commenter. In 
particular, EPA does not agree that it is necessary to evaluate 
significant contribution to areas where only the model predicts 
nonattainment where there are no monitors. Even if EPA felt it was 
appropriate to use model results to determine areas that are not 
attaining the standard, EPA does not agree that the modeled 
nonattainment of the 1997 8-hour ozone NAAQS (current and projected) in 
the Wasatch Front Range area in the UBAQS supports the commenter's 
concerns about the need to evaluate the possibility of significant 
contribution from New Mexico to nonattainment in these areas. Based on 
what the commenter presented, 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.'' \15\ First, the 
commenter's interpretation of the predicted ozone concentrations shown 
in Figures 4-3a and 4-3b (pages 4 and 5 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 the exact modeled value is not specified and there are 
only three grid cells with this value range estimated. If the actual 
model prediction is less than or equal to 84.94 ppb then the area is 
attaining the 1997 8-hour ozone NAAQS, if it is predicted as greater 
than 84.94 ppb then the modeling is indicating that it is not attaining 
those NAAQS. Thus, the current and predicted design values for the 
three grid cells in 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. EPA does not believe that this evidence adequately 
establishes that one or both areas definitely violate the NAAQS, even 
if the information were taken at face value.
---------------------------------------------------------------------------

    \15\ WG's April 16, 2010 comment letter, pp. 3. The letter is 
available for review at the regulations.gov Web site Docket ID No. 
EPA-R06-OAR-2007-0993.
    Page three of the commenter's letter.
---------------------------------------------------------------------------

    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.\16\ The study 
deviates in at least two significant ways from EPA's 2007 guidance on 
SIP modeling.\17\ One deviation is the UBAQS modeling reliance on fewer 
than the five years of data recommended by EPA to generate an 8-hour 
ozone current 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 deviation is in the computation of the relative 
responsive

[[Page 33179]]

factor (RRF), which directly affects the modeling's future design value 
(DVF).\18\ 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.\19\ Also, looking at 
Figures 3-19a-j of the UBAQS report, which cover ozone modeling 
performance through September of 2005, shows the modeling to have an 
over prediction bias for ozone. So, EPA concludes that the modeling 
analysis results provided by the commenter are unreliable for 
projecting nonattainment status even if EPA believed it was appropriate 
to use modeling for this purpose for the 1997 8-hr ozone NAAQS.
---------------------------------------------------------------------------

    \16\ See UBAQS, pp. 4-27 to 4-29.
    \17\ EPA, 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 (2007), available at https://www.epa.gov/scram001/guidance/guide/final-03-pm-rh-guidance.pdf.
    \18\ Id., DVC x RRF = DVF.
    \19\ See UBAQS, p. 4-28.
---------------------------------------------------------------------------

    Finally, even if it were appropriate to consider modeled violations 
and the modeling were reliable for this purpose, the commenter has not 
raised any convincing evidence that emissions from New Mexico sources 
are impacting southwestern Utah during the predicted high ozone events. 
Specifically, no assessment or source apportionment was performed that 
indicated sources in New Mexico contributed to the three grid cells 
with modeled high values that may be modeled nonattainment values in 
Utah. In fact, the predominant wind direction would not carry emissions 
from New Mexico into southwestern Utah. Furthermore, in evaluating the 
Figures provided (Fig 4-3a to 4-4b) and other information in the 
modeling report, the modeling also does not indicate that emissions 
from New Mexico are impacting the higher modeled ozone values in the 
southwestern Utah area.
    In summary, EPA does not agree that it is appropriate for purposes 
of section 110(a)(2)(D) to use modeled nonattainment as a basis for 
evaluation, for these two NAAQS (1997 8-hour ozone NAAQS and PM 2.5 
NAAQS) especially in light of the concerns with the modeling discussed 
above. Even if EPA were to use modeling for this purpose, the UBAQS 
modeling analyses does not clearly predict violations of the 1997 8-
hour ozone NAAQS in western Colorado and eastern Utah. In particular, 
the UBAQS modeling does not clearly establish violations of the NAAQS 
in southwestern Utah because of the way the results were reported. 
Significantly, the model does project violations in the Salt Lake City 
area (in 2006 and 2012 model years), but monitors in the area do not 
substantiate these modeled predictions. Based on monitoring data for 
2007-2009, the Salt Lake City area does not have a monitored design 
value within 6 ppb of the level of the 1997 8-hour ozone NAAQS. In 
addition, EPA does not consider the UBAQS modeling reliable because the 
modeling deviates from EPA guidance and appears to have an over-
prediction bias. Finally, the commenter did not provide evidence that 
emissions from New Mexico in fact contributed significantly to the 
modeled exceedances or violations projected in this modeling.
    Comment No. 5--In support of its arguments that EPA should not 
assess significant contribution to nonattainment through evaluation of 
impacts at monitors instead of modeling impacts where there is no such 
monitor, the commenter cited a past statement by EPA to the effect that 
the ozone monitoring network in the western United States needs to be 
expanded. The quoted statements included EPA's observation that: 
``[v]irtually all States east of the Mississippi River have at least 
two to four non-urban O3 monitors, while many large mid-
western and western States have one or no non-urban monitors.'' 74 FR 
34525 (July 16, 2009). From this statement, the commenter argues that 
it is not appropriate for EPA to limit evaluation of significant 
contribution to nonattainment of the ozone NAAQS in other states to 
reliance on monitoring data instead of modeled ambient levels.
    EPA Response--EPA does not disagree that there are relatively few 
ozone monitors in the western states, and that relatively few of these 
ozone monitors are currently located in non-urban areas of western 
states. However, the commenter failed to note that the quoted statement 
from EPA concerning the adequacy of western monitors came from the 
Agency's July 16, 2009, proposed rulemaking entitled ``Ambient Ozone 
Monitoring Regulations: Revisions to Network Design Requirements.'' 
This statement was thus taken out of context, because EPA was in that 
proposal referring to changes in state monitoring networks that it 
anticipates will be necessary in order to implement not the 1997 8-hour 
ozone NAAQS, the subject of this rulemaking, but rather the next 
iteration of the ozone NAAQS. Because the new ozone standard is likely 
to be significantly more stringent than the 1997 8-hour ozone NAAQS, it 
is anticipated there will be a need to evaluate ambient levels in 
previously unmonitored areas of the western United States. The fact 
that additional monitors may be necessary in the future for a newer 
ozone NAAQS does not mean that the existing ozone monitoring networks 
are insufficient for the 1997 8-hour ozone NAAQS, as the commenter 
implies. Indeed, states submit annual monitor network reports to EPA 
and EPA evaluates these to insure that the deployment of monitors in 
the state meets the applicable regulatory requirements and guidance 
recommendations.
    For example, New Mexico itself submits just such a report on an 
annual basis, and EPA reviews it for adequacy.\20\ All states submit 
comparable reports. Absent a specific concern that another state's 
current monitor network is inadequate to evaluate ambient levels of the 
1997 8-hour ozone NAAQS, EPA has no reason to believe that the 
evaluation of possible significant contribution from New Mexico sources 
in reliance on those monitors is incorrect.
---------------------------------------------------------------------------

    \20\ See the New Mexico Annual Monitoring Network Plan dated 
July 14, 2009. The plan is available for review at the 
regulations.gov Web site under Docket ID No.  EPA-R06-OAR-
2007-0993.
---------------------------------------------------------------------------

    Comment No. 6--The commenter objected to EPA's proposed approval of 
the New Mexico's SIP submission because neither New Mexico nor EPA 
performed a specific modeling analysis to assure that emissions from 
New Mexico sources do not significantly contribute to nonattainment of 
the 1997 8-hour ozone NAAQS in downwind States.
    EPA Response--First, this comment is incorrect. EPA and New Mexico 
did provide modeling as part of the evaluation of whether emissions 
from sources in New Mexico impact monitors with violating data in other 
states. The modeling is discussed in the proposed federal register and 
technical support document for this action and is one of the primary 
considerations in EPA's approval. The modeling that the commenter 
claims is necessary but absent, is modeling to assess impacts in areas 
with no monitors. As explained above, EPA believes that the assessment 
of significant contribution to nonattainment under section 110(a)(2)(D) 
for these NAAQS should be based upon impacts at monitors.
    Second, EPA disagrees with the commenter's belief that only 
modeling can establish whether or not there is significant contribution 
from one state to another. As noted above, EPA does not believe that 
section 110(a)(2)(D) requires modeling. While modeling can be useful, 
EPA believes that other forms of analysis can be sufficient to evaluate 
whether or not there is significant contribution to nonattainment. For 
this reason, EPA's 2006 Guidance

[[Page 33180]]

recommended other forms of information that states might wish to 
evaluate as a qualitative approach as part of their section 
110(a)(2)(D) submissions for the 1997 8-hour ozone NAAQS. EPA has 
concluded that the qualitative approach used by New Mexico in addition 
to modeling to assess the existence of, and extent of, any significant 
contribution to downwind ozone nonattainment is consistent with EPA's 
2006 Guidance.
    Comment No. 7--In further support of its argument that EPA must use 
modeling to evaluate whether there is significant contribution to 
nonattainment under section 110(a)(2)(D), the commenter noted that EPA 
itself asks other agencies to perform such modeling in other contexts. 
As examples, the commenter cited four examples in which EPA commented 
on actions by other agencies in which EPA recommended the use of 
modeling analysis to assess ozone impacts prior to authorizing oil and 
gas development projects. As supporting material, the comment includes 
quotations from and references to EPA letters to Federal Agencies on 
assessing impacts of oil and gas development projects.\21\ The 
commenter questioned why EPA's recommendation for such an approach in 
its comments to other Federal Agencies, did not result in its use of 
the same approach to evaluate the impacts from New Mexico's emissions 
and to insure compliance with Section 110(a)(2)(D)(i)(I). The commenter 
reasoned that the emissions that would result from the actions at issue 
in the other agency decisions, such as selected oil and gas drilling 
projects, would be of less magnitude and importance than the statewide 
emissions at issue in an evaluation under section 110(a)(2)(D).
---------------------------------------------------------------------------

    \21\ WG's April 16, 2010 comment letter, pp. 8-9. Complete 
versions of the EPA comment letters referenced here were attached to 
the comment as Exhibits 3 through 6, and are viewable on the 
Regulations.gov Web site as Documents ID No. EPA-R06-OAR-2007-0993-
0008.3 through 0993-0008.6.
---------------------------------------------------------------------------

    EPA Response--As explained above, this comment is misplaced because 
EPA and New Mexico did employ modeling as part of the evaluation. 
Further, EPA disagrees with the commenter's fundamental argument that 
modeling is mandatory in all instances in order to evaluate significant 
contribution to nonattainment, whether by section 110(a)(2)(D), by EPA 
guidance, or by past EPA precedent. EPA's applicable guidance made 
recommendations as to different approaches that could lead to 
demonstration of the satisfaction of the interstate transport 
requirements for significant contribution to nonattainment in other 
states. 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.'' Even EPA's own CAIR analysis relied on a 
combination of qualitative and quantitative analyses. EPA's CAIR 
analysis excluded certain western states on the basis of a qualitative 
assessment of topography, geography, and meteorology.\22\
---------------------------------------------------------------------------

    \22\ See 69 FR 4581, January 30, 2004.
---------------------------------------------------------------------------

    Furthermore, EPA believes that the commenter's references to EPA 
statements commenting on the actions of other agencies are inapposite. 
As the commenter is aware, those comments were made in the context of 
the evaluation of the impacts of various federal actions pursuant to 
National Environmental Policy Act, not the Clean Air Act. As explained 
above, in the context of section 110(a)(2)(D), EPA does not agree that 
only modeling is always required to make that different type of 
evaluation, and EPA itself has relied on other more qualitative 
evidence when it deemed that evidence sufficient to reach a reasoned 
determination.
    Comment No. 8--In further support of its argument that EPA should 
require a specific type of modeling to evaluate significant 
contribution to nonattainment, the commenter referred to EPA 
regulations governing nonattainment SIPs. The commenter noted 40 CFR 
51.112(a)(1), which states that: ``[t]he adequacy of a control strategy 
shall be demonstrated by means of applicable air quality models, data 
bases, and other requirements specified in appendix W of [Part 51] 
(Guideline on Air Quality Models).'' The commenter argues that this 
regulation appears to support the commenter's position that modeling is 
required to satisfy the significant contribution element of 
110(a)(2)(D).
    EPA Response--EPA disagrees with this comment. The cited language 
implies that the need for control strategy requirements has already 
been demonstrated, and sets a modeling analysis requirement to 
demonstrate the adequacy of the control strategy developed to achieve 
the reductions necessary to prevent an area's air quality from 
continuing to violate the NAAQS. EPA's determination that emissions 
from sources in New Mexico do not contribute significantly to 
nonattainment for the 1997 8-hour ozone NAAQS in any other state 
eliminates the need for a control strategy aimed at satisfying the 
section 110(a)(2)(D) requirements. Moreover, EPA interprets the 
language at 40 CFR 51.112(a): ``[e]ach plan must demonstrate that the 
measures, rules, and regulations contained in it are adequate to 
provide for the timely attainment and maintenance of the national 
standard that it implements,'' to refer to modeling for attainment 
demonstrations, an integral part of nonattainment area SIPs under part 
D of the CAA. This interpretation was upheld by the Sixth Circuit Court 
of Appeals. Wall v. U.S. EPA, 265 F.3d 426, 436 (6th Cir. 2001). This 
modeling may also be appropriate under certain circumstances for 
maintenance SIPs under section 110(a)(1). Thus, the commenter's cited 
regulation is not relevant to EPA's technical demonstration assessing 
whether emissions from New Mexico contribute significantly to 
nonattainment in any other states under section 110(a)(2)(D)(i).
    Comment No. 9--The commenter expressed concern with EPA statements 
in the proposed approval about the current factual attainment of the 
Denver Metro/North Front Range area of Colorado. The commenter noted 
that nine counties in the Denver area are currently formally designated 
``nonattainment'' for the 1997 8-hour ozone NAAQS. The commenter took 
issue with EPA's description of the nature of the nonattainment problem 
in this area as resulting from an unusually bad ozone season that 
``temporarily'' resulted in violations of the NAAQS. The commenter 
argued that data from the 2001-2003 period and the 2005-2007 period 
showed consistent violations of the 1997 8-hour ozone NAAQS in the 
Denver area, and that these violations are the reason for the current 
nonattainment designation.
    EPA Response--EPA disagrees that formal designation status of an 
area is the most important consideration in evaluating the existence 
of, and extent of, the impacts of interstate transport from one state 
to another. In past actions under section 110(a)(2)(D), EPA has 
interpreted that provision to turn upon the actual monitored ambient 
levels in a downwind area, regardless of the formal designation status 
of the area. For example, EPA developed the CAIR

[[Page 33181]]

rule based upon evaluation of monitor data showing violations of the 
1997 PM2.5 NAAQS in certain areas, in advance of completing 
the designation process for those NAAQS under section 107(d). \23\ EPA 
agrees that the designation status of an area is a relevant 
consideration, but the actual monitored ambient levels are an 
appropriate measure, especially when there is evidence that the 
monitored levels are different than reflected by the designation for 
the area. EPA itself has also looked to future attainment status as a 
means of evaluating the presence of, and extents of, interstate 
transport. This analysis depends not upon the anticipated formal 
designation status of the area, but rather upon the anticipated 
monitored level of the area.\24\
---------------------------------------------------------------------------

    \23\ See: Final CAIR rule, 70 FR 25,162, 25,263-25,269.
    \24\ EPA notes that the commenter itself also made the argument 
that nonattainment for purposes of section 110(a)(2)(D) should be 
viewed ``in terms of air quality, and not in terms of area 
designations'' on page 2 of its own comment letter.
---------------------------------------------------------------------------

    EPA believes that the commenter is placing undue importance upon 
the EPA's characterization of the data from Denver area monitors as 
``temporarily'' in nonattainment based on the ``bad'' ozone season of 
2007. EPA agrees that this area has historically had relatively high 
ambient levels. However, as explained in the proposal, these levels 
have improved, and more importantly, have improved during the period 
that is most relevant and most recent. As noted in the proposal, recent 
monitoring data from the Denver area for the 2007-2009 period indicates 
that the area is below the level of the NAAQS. For this trend to 
change, EPA anticipates that the Denver area would have to have 
dramatically higher ozone levels in 2010 than the area has experienced 
for many years. EPA believes that it is more reasonable to conclude 
that the monitored attainment of this area at the time of the analysis 
done by New Mexico will continue. Therefore there could not be 
significant contribution from sources in New Mexico to nonattainment in 
Denver.
    EPA believes that the downward trend in monitored nonattainment in 
the Denver area supports this conclusion. At the time the modeling was 
performed to support the state's section 110(a)(2)(D) submission, 
Denver was monitoring attainment (the 2004-2006 8-Hour Ozone Design 
Value (DV) was 81 ppb).\25\ In 2007, the Denver area experienced a 
particularly bad ozone season, and inclusion of the data from this year 
did temporarily affect the monitored values in this area. However, the 
most recent data for this area, preliminary data for 2007-2009 DV 
(awaiting final data validation), is 82 ppb even with inclusion of the 
very high ozone values from 2007. Thus, the area's most recent DV based 
upon preliminary data is several ppb below the 1997 8-hour ozone NAAQS, 
and the area is therefore currently monitoring attainment.
---------------------------------------------------------------------------

    \25\ Data from EPA's Air Quality System which is EPA's 
repository of ambient air quality data. (https://www.epa.gov/ttn/airs/airsaqs/).
---------------------------------------------------------------------------

    The downward trend in ozone concentrations is in part the result of 
a sustained effort to attain the NAAQS in the Denver area. The Denver 
area has seen a drop in ozone levels in the last 10 years attributable 
in part to federal measures that have reduced mobile source emissions. 
In addition, Colorado adopted an Ozone Action Plan in December 2008 
that included additional reductions in emissions of ozone precursors 
(NOX and VOCs), that will further aid the area in 
maintaining attainment. Given these facts, EPA concludes that the 
monitored attainment of the 1997 8-hour ozone NAAQS in the Denver area 
is likely to continue.
    Comment No. 10--The commenter also disputed the EPA statement in 
the proposal that it is ``unlikely that Denver will be in nonattainment 
at the end of the 2010 ozone season,'' and questioned why EPA did not 
cite or include any actual model data to support this assertion. The 
commenter specifically took issue with EPA's reference to the ``2010 
ozone season'' in the proposal because section 110(a)(2)(D) would 
prohibit significant contribution to nonattainment at all times, not 
simply during the ``2010 ozone season.''
    EPA Response--As discussed above, EPA believes the monitoring data 
adequately demonstrates that the Denver area is attaining the standard 
and is likely to continue to do so. The commenter is correct that EPA 
did not cite modeling that showed that Denver would be in attainment in 
2010 in the proposal. We are aware, however, of the photochemical 
modeling for Denver completed as part of the ``Ozone Action Plan'' 
adopted by Colorado in December 2008.\26\ This plan included the 
benefits of federal measures and fleet turnover and additional local 
NOX and VOC reductions. The plan also included photochemical 
modeling that indicated all monitors in the area would be in attainment 
of the 1997 8-hour ozone NAAQS in 2010. The modeling results supplement 
the monitoring results discussed previously indicating the area is in 
attainment and will be in attainment in 2010.
---------------------------------------------------------------------------

    \26\ ``Denver Metro Area & North Front Range Ozone Action Plan 
Including Revisions to the State Implementation Plan'', Approved by 
Colorado Air Quality Control Commission, December 12, 2008.
---------------------------------------------------------------------------

    Further, EPA believes that the commenter is mistakenly assuming 
that EPA's reference to the ``2010 ozone season'' implied that section 
110(a)(2)(D) would not require the elimination of emissions from 
sources in an upwind state that significantly contributed to violations 
of a NAAQS at any time of the year. In the case of the 1997 8-hour 
ozone NAAQS, however, it is a fact that there is an ``ozone season'' in 
many places across the county. Higher ozone concentration levels 
typically occur during the warmer, sunnier portions of the year, 
especially the summer. Like most areas, Denver has an ozone season. 
Therefore, it is not unreasonable for EPA to evaluate the likely 
impacts of data from monitors in this area during the ``ozone season.''
    EPA also disagrees that an evaluation focused on impacts on 2010 
levels is not adequate for purposes of section 110(a)(2)(D). As further 
discussed elsewhere in this notice, EPA's 2006 Guidance to states for 
section 110(a)(2)(D) SIP submissions recommended that states might 
elect to evaluate the existence of, and extent of, significant 
contribution to nonattainment in other states by evaluating impacts as 
of an appropriate year (such as 2010) and in light of the cost of 
control to mitigate emissions that resulted in interstate transport. 
EPA itself in the context of the CAIR rule evaluated whether there 
would be such impacts in 2010. This year was a reasonable choice, 
because it correlated with the presumptive attainment dates for states 
with nonattainment areas. For example, in the case of the 1997 
PM2.5 NAAQS, the applicable attainment date is as 
expeditiously as practicable, but not later than five years from the 
effective date of the designation, i.e., by 2010. Because 2010 is a 
reasonable date for this analysis, given the purpose of section 
110(a)(2)(D), and is consistent with EPA's recommendations in the 2006 
Guidance, EPA concludes that the selection of this date for the 
analysis supporting the New Mexico submission was appropriate. The 
commenter did not suggest another date that would be more appropriate 
nor did they explain the basis for requiring a different year for this 
analysis.
    Comment No. 11--The commenter also asserted that EPA was wrong in 
stating that the Denver area had not experienced a 4th highest 8-hour 
ozone reading of 92 ppb in the last 15 years. The commenter claimed 
that the Denver metro area experienced a 4th highest

[[Page 33182]]

max of 95 ppb at the Roxborough Park monitor in Douglas County in 2005 
and of 95 ppb at the Applewood monitor in Jefferson County in 1998 and 
in 2003.
    EPA Response--In response to this comment, EPA rechecked the data 
in the EPA's Air Quality System (AQS) and believes the commenter was in 
error that a fourth highest maximum of 95 ppb occurred at the 
Roxborough Park (also know as the Chatfield monitor) monitor in 2005. 
EPA's AQS indicates a value of 84 ppb in 2005. However, EPA's AQS does 
indicate that a 95 ppb 4th high occurred in 2003 at the Roxborough Park 
monitor and this may be the date that the commenter intended. In any 
event, upon closer examination, EPA concludes that the commenter is 
correct that values above 92 ppb have occurred in the Denver area in 
the last 15 years.
    EPA also notes that the current DVs (2007-2009) for these two 
monitors (Roxborough Park and Applewood) are 77 ppb and 76 ppb, which 
is well below the 1997 8-hour ozone NAAQS. Furthermore, these monitors 
would have to have fourth high daily maximum 8-hour monitored values of 
104 and 111 ppb respectively in 2010 to have a 2008-2010 DV violating 
the 1997 8-hour ozone NAAQS. The fourth high daily maximum value 
monitored the last 15 years in the Denver area was 95 ppb which is 
significantly lower than the 104 or 111 ppb values that would have to 
be monitored for either of these two monitors to be violating the 1997 
8-hour ozone NAAQS.
    Therefore, EPA believes that the commenter's correction that there 
have been higher values (maximum of 95 ppb in the last 15 years) at 
monitors in the Denver area does not fundamentally affect EPA's 
evaluation in this case. The higher values were not at the monitor that 
was the basis for the Denver area design value in the last several 
years. The monitor that has been the basis for the Denver area DV has 
been the Rocky Flats North monitor. Even though the commenter is 
correct that the area has monitored higher values at certain monitors 
in the past, these monitors are not the monitors that have in recent 
years determined whether the area will continue to monitor attainment 
because they have not recorded the highest design value in the area. 
The Rocky Flats North monitor has the highest 2007-2009 Denver area DV 
of 82 ppb and is based upon fourth high values of 90 ppb in 2007, 79 
ppb in 2008, and 79 ppb in 2009. This monitor would have to have a 
fourth high daily maximum of 97 ppb in 2010 to result in a violation of 
the 1997 8-hour ozone NAAQS. Therefore, it does not change EPA's 
conclusion that the Denver area continues to monitor attainment and 
therefore emissions from sources in New Mexico cannot be contributing 
significantly to violations of the 1997 8-hour ozone NAAQS in this 
area.
    Comment No. 12--The commenter also pointed to modeling data used by 
New Mexico that appears to contradict the conclusion that emissions 
from New Mexico do not contribute significantly to violations of the 
1997 8-hour ozone NAAQS in Denver. The commenter argued that data 
available in New Mexico's own technical support document that was part 
of EPA's record (Docket No. EPA-R06-OAR-2007-0993) establish that 
emissions from New Mexico sources ``often contributes greater than 2 
parts per billion in ozone on days when exceedances of the 1997 ozone 
NAAQS are recorded in Denver'' and can contribute ``more than 5% to 
Denver's total ozone concentrations.'' Finally, the commenter argued 
that New Mexico wrongly assumed that this amount of contribution was 
not relevant ``under the assumption that the region was not in 
nonattainment'' when the area is currently designated nonattainment.
    EPA Response--EPA disagrees with the commenter's conclusions drawn 
from the modeling. The modeling was conducted using an emissions 
inventory from 2002. Because emissions in the year 2010 are expected to 
be lower, EPA considers this modeling to be a conservative estimate of 
ozone levels in the future and of the impact of New Mexico's emissions 
on other states. EPA believes that the modeling shows higher impacts 
than are actually occurring. The modeling utilized existing CENRAP 
modeling databases available at the time and the source apportionment 
evaluation was conducted using the 2002 emission inventory databases. 
Because the available databases were for 2002 and not 2010, EPA 
considers the results of the modeling conservative because significant 
emission reductions are expected to occur throughout the modeled area 
between 2002 and 2010 (as a result of both federal and state measures, 
including fleet turnover impacts) that would result in lower ambient 
ozone levels and fewer exceedances of the 1997 8-hour ozone NAAQS 
throughout the modeling domain.
    Specifically, there are three elements in this analysis that EPA 
concludes lead to overestimation of the impacts of New Mexico sources 
and therefore mak