Document ID: EPA-R10-OAR-2010-0669-0021
Agency: epa
Document Type: Rule
Title: Approvals and Promulgations of Implementation Plans: Idaho State Implementation Plan
Posted Date: 2010-11-26T05:00Z

[Federal Register Volume 75, Number 227 (Friday, November 26, 2010)]
[Rules and Regulations]
[Pages 72705-72719]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-29626]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R10-OAR-2010-0669; FRL-9231-2]

Approval and Promulgation of Implementation Plans; Idaho

AGENCY: Environmental Protection Agency.

ACTION: Final rule.

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SUMMARY: EPA is approving a State Implementation Plan (SIP) revision 
submitted by the State for Idaho for the purpose of addressing the 
``good neighbor'' provisions of the Clean Air Act (the Act or CAA) 
section 110(a)(2)(D)(i) for the 1997 8-hour ozone National Ambient Air 
Quality Standards (NAAQS or standards) and the 1997 PM2.5 
NAAQS. This SIP revision addresses the requirement that the State of 
Idaho's SIP have adequate provisions to prohibit air emissions from 
adversely affecting another state's air quality through interstate 
transport. In this action, EPA is approving the Idaho Interstate 
Transport SIP provisions that address the requirement of section 
110(a)(2)(D)(i) that emissions from Idaho sources do not significantly 
contribute to nonattainment of the 1997 8-hour ozone NAAQS and the 1997 
PM2.5 NAAQS in any other state, interfere with maintenance 
of the 1997 8-hour ozone NAAQS and the 1997 PM2.5 NAAQS in 
any other state, and interfere with measures required in the SIP of any 
other state under part C of subchapter I of the CAA to prevent 
significant deterioration of air quality. This action is being taken 
under section 110 and part C of subchapter I of the CAA.

DATES: This action is effective on December 27, 2010.

ADDRESSES: Copies of the State's SIP revision and other information 
supporting this action are available for inspection at EPA Region 10, 
Office of Air, Waste, and Toxics (AWT-107), 1200 Sixth Avenue, Suite 
900, Seattle, Washington 98101.

FOR FURTHER INFORMATION CONTACT: Donna Deneen, EPA Region 10, Office of 
Air, Waste, and Toxics (AWT-107), 1200 Sixth Avenue, Seattle, 
Washington 98101, or at (206) 553-6706.

SUPPLEMENTARY INFORMATION: Throughout this document wherever ``we'', 
``us'' or ``our'' are used, we mean EPA. Information is organized as 
follows:

Table of Contents

I. What action is EPA taking?
II. What is the background for this action?
III. Response to Comments
    A. Comments Relating to the ``Significant Contribution to 
Nonattainment'' Element
    B. Comments Relating to the ``Interfere With Maintenance'' 
Element
    C. Comment Relating to Section 110(l)
IV. Final Action
V. Scope of Action

I. What action is EPA taking?

    EPA is approving a portion of Idaho's Interstate Transport State 
Implementation Plan (SIP) revision for the 1997 8-hour ozone and 1997 
PM2.5 NAAQS submitted by the Idaho Department of Quality 
(IDEQ) on June 28, 2010. Specifically, we are approving the portion of 
the plan that addresses

[[Page 72706]]

the following elements of CAA section 110(a)(2)(D)(i): (1) Significant 
contribution to nonattainment of these NAAQS in any other state, (2) 
interference with maintenance of these NAAQS by any other state, and 
(3) interference with any other state's required measures to prevent 
significant deterioration (PSD) of its air quality with respect to 
these NAAQS. IDEQ addressed element (4), interference with any other 
state's required measures to protect visibility, by referring to its 
Regional Haze SIP, which will be submitted separately. EPA will take 
action on the visibility element in a separate action. None of the 
findings and conclusions in this notice, accordingly, relate to EPA's 
analysis of interference with another state's required measures to 
protect visibility. EPA will also take action on the portion of Idaho's 
SIP that addresses the 2006 PM2.5 NAAQS \1\ in a separate 
action.
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    \1\ The PM2.5 standard was revised in 2006. See 
``National Ambient Air Quality Standards for Particulate Matter,'' 
at 71 FR 61144 (October 17, 2006).
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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 promulgation of the 1997 8-hour ozone NAAQS 
and 1997 PM2.5 NAAQS. This action does not address the 
requirements of the 2006 24-hour PM2.5 NAAQS or the 2008 8-
hour ozone NAAQS; those standards will be addressed in a future action.
    Section 110(a)(1) of the CAA requires states to submit SIPs to 
address a new or revised NAAQS within three 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) 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'' (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 standards and 1997 PM2.5 standards.
    On June 28, 2010, we received a SIP revision from the State of 
Idaho 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) identifies four distinct elements related to 
the evaluation of impacts of interstate transport of air pollutants. In 
this rulemaking EPA is addressing the first three elements: (1) 
Significant contribution to nonattainment of these NAAQS in any other 
state, (2) interference with maintenance of these NAAQS by any other 
state, and (3) interference with any other state's required measures to 
prevent significant deterioration (PSD) of its air quality with respect 
to these NAAQS. Idaho asserted in its SIP submission that its current 
SIP is adequate to prevent such contribution and interference, and thus 
no additional controls or revisions are needed with respect to the 1997 
8-hour ozone NAAQS and 1997 PM2.5 NAAQS.
    On September 13, 2010, EPA published a proposal to approve the 
portion of Idaho's SIP submission that addresses the three elements of 
CAA section 110(a)(2)(D) for both the 1997 8-hour ozone NAAQS and 1997 
PM2.5 NAAQS: (1) Significant contribution to nonattainment 
of these NAAQS in any other state, (2) interference with maintenance of 
these NAAQS by any other state, and (3) interference with any other 
state's required measures to prevent significant deterioration (PSD) of 
its air quality with respect to these NAAQS (75 FR 55494). EPA finds 
that Idaho's Interstate Transport SIP provisions addressing elements 
(1), (2), and (3) of section 110(a)(2)(D)(i) are consistent with the 
requirements of the CAA.

III. Response to Comments

    EPA received one letter from WildEarth Guardians (WG) commenting on 
several aspects of EPA's proposed approval of the Idaho Interstate 
Transport SIP. These comments addressed the ``significant contribution 
to nonattainment,'' and ``interfere with maintenance,'' elements of the 
SIP for the 1997 8-hour ozone and 1997 PM2.5 NAAQS. WG also 
alleged in its comments that EPA failed to comply with the requirements 
of CAA Section 110(l) with respect to the attainment and maintenance of 
the current NAAQS. No comments were received that specifically 
addressed EPA's proposed approval of the ``interfere with any other 
state's required measures to prevent significant deterioration'' 
elements of the SIP for the 1997 8-hour ozone and 1997 PM2.5 
NAAQS. In this section EPA summarizes and responds to the significant 
adverse comments submitted by the commenter.

A. Comments Relating to the ``Significant Contribution to 
Nonattainment'' Element

    Comment No. 1--WG argued that Idaho and EPA did not appropriately 
assess impacts to nonattainment in downwind states. According to WG, 
Idaho failed to assess significance of downwind impacts in accordance 
with EPA guidance and precedent. The commenter identified statements by 
EPA in the context of the 1998 NOX SIP Call as the 
applicable guidance for this purpose. 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 the upwind state's emissions are linked; (c) the 
ambient impact of the emissions from the upwind state's sources on the 
downwind nonattainment problems; and (d) the availability of highly 
cost-effective control measures for upwind emissions. 63 FR 57356, 
57376 (October 27, 1998).
    EPA Response--EPA disagrees with the commenter's conclusions 
regarding the relevant guidance and standards necessary to determine 
whether or not a state's emissions contribute significantly to 
nonattainment in another state. 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 such 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 
and its application to factual situations before the Agency.
    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

[[Page 72707]]

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 used in 
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.
    The commenter failed to acknowledge that 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 (``2006 Guidance'').\2\ The 2006 
Guidance 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. In EPA's proposal, this Guidance was 
identified by the Agency as applicable to the analysis before it.
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    \2\ 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-R10-OAR-2010-0669-0005.
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    In the 2006 Guidance, EPA 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.'' \3\ 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.'' \4\ To that end, EPA specifically recommended that states 
located within the geographic region covered by the ``Clean Air 
Interstate Rule'' (CAIR) \5\ comply with section 110(a)(2)(D) for the 
1997 8-hour 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.
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    \3\ 2006 Guidance at 3.
    \4\ Id.
    \5\ In this action, ``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.'' \6\ 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 and 
in light of the cost of control to mitigate emissions that resulted in 
significant contribution.\7\
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    \6\ 2006 Guidance at 5.
    \7\ Id.
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    WG did not acknowledge or discuss EPA's 2006 Guidance for section 
110(a)(2)(D) SIP submissions for the 1997 8-hour ozone and 
PM2.5 NAAQS, even though it was specifically identified and 
applied in EPA's proposal. EPA believes that the Idaho submission and 
EPA's evaluation of it were consistent with EPA's 2006 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 Idaho 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 under the circumstances of this action. Thus, EPA 
has concluded that the state's submission meets the requirements of 
section 110(a)(2)(D) and that EPA's evaluation of the state's SIP is 
consistent with the applicable 2006 Guidance and the Act.
    Finally, EPA notes that the considerations in the 2006 Guidance are 
consistent with the concepts that WG identified as applicable from the 
NOX SIP Call: (a) The overall nature of the problem; (b) the 
extent of the downwind nonattainment problems to which the upwind 
state's emissions are linked; (c) the ambient impact of the emissions 
from the upwind state's sources on the downwind nonattainment problems; 
and (d) the availability of highly cost-effective control measures for 
upwind emissions. These factors were taken into account in EPA's 
analysis of the Idaho SIP with the exception of consideration of the 
costs of controls for sources. EPA did not evaluate those costs because 
the available evidence indicated that there is very little contribution 
from emissions from Idaho sources to nonattainment in other states.
    Comment No. 2 --WG objected to EPA's proposed approval on the 
grounds that Idaho and EPA failed to adequately analyze and assess the 
contribution from Idaho's emissions to downwind states, and did not 
conduct an actual assessment of the significance of any such 
contribution or impacts.
    EPA Response--EPA disagrees with WG's characterization of Idaho's 
and EPA's demonstration and analysis. WG again assumes that section 
110(a)(2)(D) explicitly demands the type of modeling analysis that the 
commenter advocates throughout its comments. WG contends that any 
analytical approach that is not identical to the approach used in the 
NOX SIP Call is impermissible. In addition, WG failed to 
acknowledge that in other actions under section 110(a)(2)(D), EPA has 
used a variety of analytical approaches, short of modeling, to evaluate 
whether a specific state is 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).
    EPA's analysis took into account meteorological conditions, 
monitoring data, distance, topography and other quantitative and 
qualitative forms of available information to evaluate and identify a 
potentially significant contribution from Idaho's emissions to 
nonattainment of the 1997 8-hour ozone and 1997 PM2.5 NAAQS 
in other states. As noted in EPA's proposal, no single piece of 
information informing this analysis is, by itself, dispositive of the 
issue. Instead, the total weight of all the evidence taken together was 
used to evaluate significant contributions to violations of the 1997 8-
hour ozone or 1997 PM2.5 NAAQS in another state. Based on 
the available information,

[[Page 72708]]

using a combination of quantitative data and qualitative analyses, we 
concluded emissions from Idaho do not contribute significantly to 
downwind ozone nonattainment. Thus, contrary to WG's assertion, EPA did 
perform an analysis and assessment that formed a reasonable basis for 
the conclusion that emissions from Idaho do not contribute 
significantly to downwind ozone and PM2.5 nonattainment, 
using a combination of quantitative data and qualitative analyses. EPA 
does not agree that the type of analysis advocated by WG is required by 
the statute and is necessary to support a rational determination in 
this instance.
    Comment No. 3--WG objected to EPA's proposed approval because EPA's 
assessment of impacts on downwind states was based upon monitoring data 
in those states, and WG alleges that this is not an adequate means of 
evaluating significant contribution to nonattainment. WG is concerned 
that the impacts of Idaho's emissions in areas without monitors were 
not assessed and that EPA only assessed ``impacts to areas that are 
designated as nonattainment or with monitors that have recorded 
violations of the ozone and PM2.5 NAAQS.'' WG argued that 
this reliance on monitoring data is inconsistent with both section 
110(a)(2)(D) and with EPA's guidance provided in the NOX SIP 
Call. In support of its objections, WG quoted statements from the 
NOX SIP Call proposal in which EPA discussed its proposed 
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 and in the matter at hand.
    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.\8\
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    \8\ Michigan v. U.S. EPA, 213 F.3d 663, 674-681 (DC 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).
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    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 2006 Guidance support WG's 
position, as neither refers to any requirement or recommendation to 
assess air quality in non-monitored areas.\9\ 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.\10\ 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. Reliance on monitoring data 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 concludes that by considering data from 
monitored areas, its assessment of whether emissions from Idaho 
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.
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    \9\ 2006 Guidance, p. 5.
    \10\ ``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.
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    Comment No. 4--In support of its comments that EPA should assess 
significant contribution to nonattainment in nonmonitored areas,

[[Page 72709]]

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 in areas 
throughout Utah, Wyoming, Colorado, and Nevada will exceed and/or 
violate the 1997 ozone NAAQS. * * *'' 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 in these western 
states.
    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 surrounding states.
    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 an 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.\11\ 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.
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    \11\ 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.
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    Comment No. 5--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.\12\
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    \12\ 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 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.\13\ The study 
deviates in at least two significant ways from EPA's 2007 guidance on 
SIP modeling.\14\ 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).\15\ 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

[[Page 72710]]

ppb, UBAQS modeling uses RRFs based on one or more days of ozone 
concentrations above 70 ppb.\16\ 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.
---------------------------------------------------------------------------

    \13\ See ``UBAQS,'' pages 4-27 to 4-29.
    \14\ 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 (http://www.epa.gov/scram001/guidance/guide/final-03-pm-rh-guidance.pdf).
    \15\ DVC x RRF = DVF.
    \16\ See UBAQS, p. 4-28.
---------------------------------------------------------------------------

    Comment No. 6--In support of its arguments that EPA should not 
limit assessment of significant contribution to nonattainment through 
evaluation of impacts at monitors, but include, through a modeling 
analysis, impacts where there are no such monitors, the commenter cited 
a past statement by EPA to the effect that the monitor 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 34,525 (July 16, 2009). From this statement, 
the commenter argues that it is not appropriate for EPA to limit the 
evaluation of significant contribution to nonattainment in other states 
to a consideration of monitor data instead of modeling ambient 
pollutant levels because there are states with few or no non-urban 
monitors surrounding Idaho.
    EPA Response--EPA acknowledges that WG's observation that there are 
relatively few monitors in the western states, and that relatively few 
monitors are currently located in non-urban areas of western states, is 
factually correct. 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 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 that is the subject of this rulemaking, but 
rather the 2008 ozone NAAQS for which there are concerns that 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 the newer ozone NAAQS does not 
automatically mean that the existing ozone monitoring networks are 
insufficient for the 1997 8-hour ozone NAAQS, as the commenter implies. 
Indeed, states submit annual monitoring network plans to EPA and EPA 
evaluates these to insure that they meet the applicable requirements. 
For example, Idaho itself submits just such a report on an annual 
basis, and EPA reviews it for adequacy.\17\ All other states submit 
comparable reports.
---------------------------------------------------------------------------

    \17\ EPA most recently reviewed the adequacy of the Idaho 
monitoring network on October 14, 2010. See letter dated October 14, 
2010 from Debra Suzuki, EPA Region 10, to Dave Broker, IDEQ.
---------------------------------------------------------------------------

    Comment No. 7--WG objected to EPA's proposed approval of the Idaho 
SIP submission because neither Idaho nor EPA performed a specific 
modeling analysis to assure that emissions from Idaho sources do not 
significantly contribute to nonattainment in downwind states. According 
to the commenter, EPA's decision to use a qualitative approach to 
determine whether emissions from Idaho contribute significantly to 
downwind nonattainment is not consistent with its own preparation of a 
regional model to evaluate such impacts from other states as part of 
CAIR.
    EPA Response--EPA disagrees with WG's proposition that only 
modeling can establish whether or not there is significant contribution 
from one state to the nonattainment of another. First, as noted above, 
EPA does not believe that section 110(a)(2)(D) requires a modeling 
analysis in all instances. 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 recommended other forms of information that 
states may rely upon as part of their section 110(a)(2)(D) submissions 
for the 1997 8-hour ozone and 1997 PM2.5 NAAQS. EPA has 
concluded that its qualitative approach to the assessment of 
significant contribution to downwind ozone and PM2.5 
nonattainment is consistent with EPA's 2006 Guidance.
    Second, EPA notes that WG's comment also reflects a 
misunderstanding of the approach EPA used in the remanded CAIR. In 
CAIR, EPA determined that several factors provided a reasonable basis 
to exclude certain western states from the ambit of that rulemaking: 
``[i]n analyzing significant contribution to nonattainment, we 
determined it was reasonable to exclude the Western U.S., including the 
states of Washington, Idaho, Oregon, California, Nevada, Utah, and 
Arizona from further analysis due to geography, meteorology, and 
topography. Based on these factors we concluded that the 
PM2.5 and 8-hour ozone nonattainment problems are not likely 
to be affected significantly by pollution transported across these 
States' boundaries. * * *'' 69 FR 4581 (January 30, 2004).
    EPA has taken a similar approach to assess whether Idaho 
contributes significantly to violations of the 1997 8-hour ozone and 
PM2.5 NAAQS in downwind states. In the proposed action, EPA 
explained several forms of substantive and technically valid evidence 
that led to the conclusion that emissions from Idaho sources do not 
contribute significantly to nonattainment, in accordance with the 
requirement of Section 110(a)(2)(D).
    Comment No. 8--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), WG noted that EPA itself asks 
other agencies to perform such modeling in other contexts. As examples, 
the commenter cited four instances in which EPA commented on actions by 
other agencies and recommended the use of a 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.\18\ WG 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 Idaho 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).
---------------------------------------------------------------------------

    \18\ WG's October 13, 2010, comment letter, pp. 9-10. The 
referenced letters have been included in the docket for this action.
---------------------------------------------------------------------------

    EPA Response--As explained above, EPA disagrees with WG's 
fundamental argument that modeling is required 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 can satisfy the 
interstate transport requirements for significant contribution to 
nonattainment in other states. Even EPA's own CAIR analysis relied on a 
combination of qualitative and quantitative analyses, as explained 
above. As indicated in our response to

[[Page 72711]]

Comment No. 7, the CAIR analysis excluded the western states based on a 
qualitative assessment of the regions topography, geography and 
meteorology.\19\
---------------------------------------------------------------------------

    \19\ 69 FR 4581, January 30, 2004.
---------------------------------------------------------------------------

    EPA believes that the commenter's references to EPA statements 
commenting on the actions of other agencies are inapposite. As WG is 
aware, those comments were made in the context of the evaluation of the 
impacts of various federal actions pursuant to the National 
Environmental Policy Act (NEPA), not the Clean Air Act. As explained 
above, section 110(a)(2)(D) governs this particular decision-making 
process, and EPA does not agree that modeling is always required to 
support the evaluation. EPA itself has relied on qualitative evidence 
for this purpose when the relevant record provides evidence sufficient 
to reach a reasoned determination.
    Comment No. 9--In further support of its argument that EPA should 
always require modeling to evaluate significant contribution to 
nonattainment, WG referred to EPA regulations governing nonattainment 
SIPs. The commenter referenced 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 argued that this regulation supports its 
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 
addresses the control strategy requirements when the necessity of 
controls has already been established. The cited provision requires a 
modeling analysis 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 Idaho do not contribute significantly to nonattainment 
for the 1997 8-hour ozone standard in any other states eliminates the 
need for a control strategy aimed at satisfying the section 
110(a)(2)(D) requirements. The provision cited by the commenter, 
therefore, is inapplicable in this context. 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 
subchapter I, 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). Thus, the commenter's cited regulation is not relevant 
to EPA's technical analysis assessing whether emissions from Idaho 
contribute significantly to nonattainment in any other states under 
section 110(a)(2)(D).
    Comment No. 10--WG referenced several modeling analyses of 
emissions in the western United States which it contends renders EPA's 
analysis inadequate. The commenter ``challenged'' EPA to prove the 
modeling results it presented are insufficient by presenting a contrary 
modeling analysis, and argued that EPA has an obligation to do so.
    Response: EPA disagrees with WG's contention that EPA is obligated 
to evaluate and disprove the modeling analyses it has submitted with a 
competing modeling analysis when other available information is 
available to dispute the modeling analysis. EPA's interpretation of 
section 110(a)(2)(D) is that the statute does not explicitly require 
modeling, and while modeling can be useful in certain circumstances, 
there is no obligation to use it to evaluate whether or not there is 
significant contribution to nonattainment. Section 110(a)(2)(D)(i) does 
not specify the forms of evidence to be used for meeting the 
requirements, and the 2006 Guidance specifically recommends other forms 
of information that states might wish to evaluate as part of their 
section 110(a)(2)(D) submissions. We evaluated whether Idaho's SIP met 
the requirement of section 110(a)(2)(D)(i) based on EPA's 2006 Guidance 
and have a reasonable basis, as discussed in the proposed approval, for 
concluding that Idaho has met the requirement of 110(a)(2)(D)(i) for 
the 1997 8-hour ozone and 1997 PM2.5 NAAQS in the absence of 
a modeling analysis.
    Comment No. 11--WG also objected to EPA's proposed approval of the 
Idaho submission on the grounds that it was based upon a ``weight-of-
evidence analysis,'' and that no such weight of evidence test appears 
in the CAA generally, or in section 110(a)(2)(D) in particular. 
According to the commenter, there is no regulatory support for using a 
``weight-of-evidence'' approach to assessing air quality impacts. The 
commenter asserted that EPA neither cited nor quoted regulations or 
policy that provides for this, and failed to lend any specific meaning 
to the phrase through its proposed approval. Finally, the commenter 
asserted, without explaining, its belief that EPA failed to address 
``several relevant factors related to the determination of whether 
Idaho contributes significantly to nonattainment undermines the 
agency's reliance on any `weight-of-evidence' approach.''
    EPA Response--EPA agrees with WG that neither the CAA generally, 
nor section 110(a)(2)(D) specifically, include the explicit phrase 
``weight of evidence.'' It simply does not follow, however, that it is 
inappropriate for EPA to use such an approach in this context. As 
explained above, section 110(a)(2)(D) does not explicitly stipulate how 
EPA may assess whether there is a significant contribution to 
nonattainment in other states. Through past actions such as CAIR, EPA 
has used a weight of evidence approach to exclude some states from 
further consideration.\20\ As described above, in EPA's 2006 Guidance 
the Agency specifically recommended types of information that states 
might wish to rely upon to evaluate the presence of, and extent of, 
interstate transport for this purpose. EPA believes that a weight of 
evidence approach that properly considers appropriate evidence is 
sufficient to make a valid determination, as in this case.
---------------------------------------------------------------------------

    \20\ See: 69 FR 4581, January 30, 2004.
---------------------------------------------------------------------------

    Specifically, EPA's technical analysis in the September 13, 2010 
proposed action underscores its reliance on implementation policies set 
in the EPA 2006 Guidance: ``EPA's August 15, 2006, guidance to states 
concerning section 110(a)(2)(D)(i) recommended various methods by which 
states might evaluate whether or not its emissions significantly 
contribute to violations of the 1997 ozone standards in another state. 
Among other methods, EPA recommended consideration of available EPA 
modeling conducted in conjunction with CAIR, 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 [our emphasis].'' \21\ On the basis of this 
Guidance, Idaho and EPA chose to assess the impacts of emissions from 
Idaho sources on nonattainment areas for the 1997 ozone NAAQS and 1997 
PM2.5 NAAQS in surrounding states through a weight of 
evidence approach

[[Page 72712]]

using quantitative and qualitative information such as monitoring data 
for those other states, Idaho's distance from areas with monitors 
showing violation of the NAAQS, meteorological conditions, and other 
characteristics for those areas. EPA's use of a weight of evidence 
analysis is by no means unusual for the assessment of ozone impacts 
through long range transport. The same analytical framework was used in 
the 1998 NOX SIP Call, as indicated under Section II.C., 
entitled ``Weight-of-Evidence Determination of Covered States.'' \22\ 
The differences between the specific types of evidence used in the 
NOX SIP Call and in our analysis do not invalidate the use 
of the weight of evidence approach.
---------------------------------------------------------------------------

    \21\ 75 FR 55494, September 13, 2010.
    \22\ ``As discussed above, EPA applied a multi-factor approach 
to identify the amounts of NOX emissions that contribute 
significantly to nonattainment.* * *'' 1998 SIP Call, 63 FR 57381, 
October 27, 1998.
---------------------------------------------------------------------------

    As for the commenter's argument that EPA ``fails to lend any 
specific meaning to the phrase through its proposed approval,'' the 
Agency's technical analysis described in the proposal did specify the 
characteristics, including limitations, of a weight of evidence 
analysis: ``[f]urthermore * * * EPA notes that no single piece of 
information is by itself dispositive of the issue. Instead, the total 
weight of all the evidence taken together is used to evaluate 
significant contributions to violations of the 1997 8-hour ozone or 
1997 PM2.5 NAAQS in another state.'' (75 FR 55496).
    Finally, as to the commenter's assertion that EPA failed to 
consider ``several relevant factors'' and thus failed to conduct an 
appropriate weight of evidence evaluation, EPA cannot weigh the 
validity of this comment in the absence of an explanation of what these 
factors might be.
    Comment No. 12--WG questioned whether a regulatory provision from 
Idaho's SIP, IDAPA 58.01.013.203.02, that was identified in the 
proposed action constitutes a ``prohibition on emissions that 
significantly interfere with nonattainment.'' \23\ WG argued that this 
provision does not appear to ensure compliance with section 
110(a)(2)(D)(i)(I) because, the commenter explains, the provision 
applies only to stationary sources (actually point sources) and not to 
mobile or field burning emissions, and that all sources must be 
considered in order to meet the requirements of the statute. The 
commenter alleged that 110(a)(2)(D)(i)(II) applies to any source or 
other type of emission activity and, therefore, Idaho's SIP provision 
is inadequate if it is limited in its application to stationary 
sources. WG went on to identify emission inventory information to 
support its argument that mobile source emissions and agricultural 
burning emissions are significant sources of emissions in Idaho. The 
commenter questioned the assertion that the abovementioned regulatory 
provision provides authority to limit a source's emissions to ensure 
attainment in other states. WG also questioned how the provision would 
apply in attainment areas. Finally, the commenter concluded that the 
Idaho SIP does not appear to contain provisions that effectively 
prohibit emissions from any source from significantly contributing to 
nonattainment in any other state.
---------------------------------------------------------------------------

    \23\ EPA notes that WG appears to have incorrectly stated and 
conflated the two different standards presented in CAA section 
110(a)(2)(D)(i)(I) in this comment. EPA assumes that, due to the 
placement of this comment in a section that WG entitled ``Measures 
in the SIP do not Appear to Ensure that Idaho will not Significantly 
Contribute to Nonattainment'' and statements made later in the 
comment, that the comment applies only to EPA's proposed approval of 
the nonattainment prong of 110(a)(2)(D)(i)(I) and was not provided 
in reference to the maintenance prong.
---------------------------------------------------------------------------

    EPA Response--EPA agrees with the commenter's assertion that the 
requirements of section 110(a)(2)(D)(i)(I) are applicable to all source 
categories and not only to stationary sources. The commenter seems to 
have read EPA's proposed action to imply that the provisions cited by 
Idaho are the only consideration in evaluating whether Idaho has met 
the requirement regarding whether or not a state's emissions 
significantly contribute to violations of 1997 ozone and 1997 
PM2.5 standards in another state. In fact, these provisions, 
which provide IDEQ with the authority to require a permit if emission 
rate reductions are necessary to attain any ambient air quality 
standard, were identified by EPA in the proposed action as ``additional 
support for [EPA's] conclusion that emissions from Idaho sources do not 
significantly contribute to nonattainment in any other state * * *.'' 
As noted in EPA's proposed action, no single piece of information was 
by itself dispositive in evaluating Idaho's potential contribution to 
nonattainment in another state. EPA has taken into account the Idaho 
SIP as a whole, which includes but is not limited to the cited 
permitting provisions, and the actual contribution of emissions from 
Idaho to nonattainment receptors in other states to evaluate whether 
the significant contribution element has been met.
    EPA disagrees with the commenter's apparent view that under section 
110(a)(2)(D) SIPs must contain literal provisions prohibiting 
significant contribution to nonattainment in any other state, or, for 
that matter, to contain any particular words or generic prohibitions. 
Instead, EPA believes that the statute requires a state's SIP to 
contain substantive emission limits or other provisions that in fact 
ensure that sources located within the state will not produce emissions 
that have such an effect in other states. In conducting its analysis of 
whether or not the state's SIP is adequate, EPA evaluates the actual 
contribution of a state's emissions to nonattainment in another state 
and does not base its analysis on the written provisions of the SIP 
alone. Therefore, EPA believes that satisfaction of the ``significant 
contribution'' requirement is not to be demonstrated through a literal 
requirement for a prohibition of the type advocated by the commenter.
    EPA's past application of section 110(a)(2)(D) did not require the 
literal prohibition advocated by the commenter. For example, in 1998 
NOX SIP call (63 FR 57356, October 27, 1998) EPA indicated 
that ``the term `prohibit' means that SIPs must eliminate those amounts 
of emissions determined to contribute significantly to nonattainment * 
* *.'' As a result, the first step of the process to determine whether 
this statutory requirement is satisfied is the factual determination of 
whether a state's emissions contribute significantly to nonattainment 
in downwind areas. See 2005 CAIR Rule (70 FR 25162) and 1998 
NOX SIP Call (63 FR 57356). If this factual finding is in 
the negative, as is the case for EPA's assessment of the contribution 
from emissions from Idaho, then section 110(a)(2)(D)(i)(I) does not 
require any changes to a state's provisions. If, however, the 
evaluation reveals that there is such a significant contribution to 
nonattainment in other states, then EPA requires the state to adopt 
substantive provisions to eliminate those emissions. The state could 
achieve these reductions through traditional command and control 
programs, or at its own election, through participation in a cap and 
trade program. Thus, EPA's approach in this action is consistent with 
the Agency's interpretation of 110(a)(2)(D)(i) in the 2006 guidance, 
the CAIR Rule, and the NOX SIP call, none of which required 
the pro forma literal ``prohibition'' of the type advocated by the 
commenter.

B. Comments Relating to the ``Interfere With Maintenance'' Element

    Comment No. 1--The commenter stated that EPA inappropriately 
defined the term ``interfere with maintenance.'' It argued that EPA's 
definition appeared to be ``inappropriately conflated with the

[[Page 72713]]

definition of nonattainment.'' It argued that the definition of 
maintenance appeared to be tied to nonattainment, asserting that 
``unless an area has violated or is in violation of the NAAQS, the 
agency will not consider whether Idaho is interfering with that area's 
ability to maintain compliance with the NAAQS.'' For this reason, it 
argued EPA did not give independent meaning to the ``interfere with 
maintenance'' prong of section 110(a)(2)(D)(i)(I).
    The commenter also maintains that EPA's analysis did not consider 
Idaho's impacts on neighboring states that have not previously 
violated, but that ``may be barely attaining the NAAQS.'' To illustrate 
its contention that EPA has inappropriately defined ``interference with 
maintenance,'' the commenter pointed to information regarding Cache 
Valley, Utah, which it describes as an example of an area that has not 
violated the 1997 24-hour PM2.5 NAAQS, but that may be 
barely attaining the NAAQS and should, therefore, be classified as a 
maintenance receptor. The commenter did not provide any other concrete 
examples of areas that EPA should have identified as maintenance 
receptors.
    Response--The definition of maintenance used by EPA is consistent 
with the direction given to EPA by the Court of Appeals for the DC 
Circuit in North Carolina v. EPA, 531 F.3d 896 (DC Cir. 2008).\24\ In 
that case, the court analyzed the definition of ``interfere with 
maintenance'' used in the CAIR rule. The court found that the 
definition EPA used ``gave no independent significance to the 
`interfere with maintenance' prong of section 110(a)(2)(D)(i)(I) to 
separately identify upwind sources interfering with downwind 
maintenance.'' North Carolina at 910. It further reasoned that 
``[u]nder EPA's reading of the statute, a state can never ``interfere 
with maintenance'' unless EPA determines that at one point it 
``contribute[d] significantly to nonattainment.'' Id. Based on this 
analysis, the court found the definition unlawful holding that 
``[b]ecause EPA describes CAIR as a complete remedy to a section 
110(a)(2)(D)(i)(I) violation and does not give independent significance 
to the 'interfere with maintenance' language to identify upwind states 
that interfere with downwind maintenance, EPA unlawfully nullifies that 
aspect of the statute and provides no protection for downwind areas 
that, despite EPA's predictions, still find themselves struggling to 
meet NAAQS due to upwind interference in 2010.'' Id. at 910-911.
---------------------------------------------------------------------------

    \24\ As EPA noted in the proposal, the term ``interfere with 
maintenance'' is not defined in the CAA. As such, the term is 
ambiguous and EPA's interpretation of that term in this action is 
both reasonable and consistent with the overall goals of the CAA. By 
this approach, EPA is giving independent meaning to the term and 
supporting that interpretation with technical analysis to apply it 
to the facts of this action.
---------------------------------------------------------------------------

    The approach used by EPA to evaluate Idaho's SIP submission and to 
determine whether emissions from sources in Idaho interfere with 
maintenance in any other state directly addresses these flaws. It gives 
significant independent meaning to the term ``interfere with 
maintenance.'' It establishes a process to identify any specific 
receptors in downwind states that, even though they are projected to be 
in attainment and thus would not be nonattainment receptors, may have 
difficulty maintaining the NAAQS in question. These receptors are 
referred to as maintenance receptors.
    The methodology EPA used to identify maintenance receptors gives 
independent meaning to the term ``interfere with maintenance'' and 
establishes a process to identify projected attainment receptors that, 
based on the historic variability of air quality at that site (which 
may be due to variability in emissions and/or meteorology), may have 
difficulty maintaining the standard. As explained in greater detail 
below, the commenter's objection to EPA's approach appears to be based 
on the misconception that the methodology EPA used to identify 
maintenance sites was dependent on base year NAAQS violations.
    The commenter's statement that EPA's designation of maintenance 
receptors is ``firmly hitched to a finding that the maximum design 
value based on a single three-year period between 2003 and 2007 is in 
excess of the NAAQS'' appears to be based on a misunderstanding of the 
methodology used by EPA to identify maintenance receptors. EPA's 
methodology did not, as the commenter appears to assume, require a site 
to have a design value above the NAAQS for one of the three base 
periods (2003-2005, 2004-2006, 2005-2007) to be considered a 
maintenance site. The methodology is based on an analysis of the future 
year average and future year maximum design values. It does not depend 
on whether the base year design values exceed the NAAQS. In the 
proposal, EPA explained that ``EPA identified those sites that are 
projected to be attainment based on the 5-year weighted average design 
value, but that have a maximum design value (based on a single three-
year period) that exceeds the NAAQS, as maintenance sites.'' (75 FR 
52697). The maximum design value referenced in this sentence is the 
maximum future design value calculated using each of the three base 
design value periods separately. Whether or not one of the three base 
period design values exceeded the NAAQS was not a factor considered in 
determining whether a site was a maintenance receptor.
    To better understand this concept, it is useful to compare the 
methodologies used in the Transport Rule (TR) proposal (75 FR 45210, 
Aug. 2, 2010) to identify nonattainment and maintenance receptors. In 
the TR proposal, base period (2003-2007) ambient data were projected to 
the future (using model outputs), to identify both nonattainment and 
maintenance receptors. In both cases, receptors were identified by 
projected future design values; however, because more conservative data 
were used for the maintenance analysis, this analysis could identify 
receptors that were projected by the nonattainment analysis to be in 
attainment, yet might have difficulty attaining the standard due to 
historic variability of air quality at that site. To identify future 
nonattainment sites EPA calculated the future year design values by 
projecting the 5-year weighted average design value for each site. Only 
if this future year design value exceeded the NAAQS was the site 
considered to be a nonattainment receptor. However, to identify 
projected maintenance sites we used a different methodology that took 
into account historic variability in air quality at each receptor. For 
this approach EPA calculated the maximum future year design value by 
processing each of the three base design value periods (2003-2005, 
2004-2006, and 2005-2007) separately. The highest of the three future 
values is the maximum design value, which is used to determine 
maintenance receptors.
    In this way, EPA's analysis identifies those areas that are 
projected to be attainment, but may have difficulty maintaining 
attainment of the standard, for example in a year with particularly 
severe meteorology (weather that is conducive to ozone and/or 
particulate formation). In other words, this analysis does exactly what 
the DC Circuit directed EPA to do in North Carolina, 531 F.3d 896. It 
gave independent meaning to the ``interfere with maintenance'' prong of 
110(a)(2)(D)(i) and is providing protection to any areas that, although 
they are predicted to attain the standard (and thus upwind sources 
could not be found to significantly contribute to nonattainment in that 
area) may have

[[Page 72714]]

difficulty maintaining the standard. North Carolina. at 911.
    EPA used this same approach to identify any potential maintenance 
receptors for purposes of evaluating Idaho's SIP submission. For the 
reasons explained above, this approach is both reasonable and 
consistent with the direction given to EPA by the DC Circuit in North 
Carolina.
    As explained above, EPA established a methodology to identify sites 
that may have difficulty maintaining the 1997 8-hour ozone or 1997 
PM2.5 NAAQS. This process identifies any specific receptors 
in downwind states that, even though they are projected to be in 
attainment and thus would not be nonattainment receptors, may have 
difficulty maintaining the NAAQS in question. Based on this 
methodology, EPA projected that the Cache Valley in Utah will not have 
difficulty meeting the 1997 8-hour ozone NAAQS or the 1997 
PM2.5 NAAQS because none of the future year design values 
exceeded the NAAQS and Cache Valley is not a maintenance receptor.
    EPA notes that, except for Cache Valley, Utah, the commenter 
provides no specific examples or facts to support its arguments that 
there are areas in neighboring states which are ``barely attaining the 
NAAQS.'' In the absence of any specific comments regarding the location 
of monitoring receptors, monitoring concentrations, or time periods 
during which these areas were purportedly ``barely attaining'' the 
NAAQS, EPA cannot respond to the commenter's generic concerns about 
interference with maintenance in the neighboring states of Montana, 
Nevada, Oregon, Montana, Wyoming, and other areas of Utah. EPA's 
analysis shows that there are no sites in any states adjacent to Idaho 
with design values exceeding the 65 ug/m\3\ which should accordingly be 
identified as maintenance receptors.
    WG provided only the example of Cache Valley, Utah, as an area that 
EPA should have identified as a maintenance receptor. The commenter 
appears to implicitly argue that EPA has inappropriately established an 
interference with maintenance threshold, although it did not identify 
specific criteria that should warrant designating an area as a 
maintenance receptor. Even if EPA did not rely on the methodology 
discussed above to give meaning to the ``interfere with maintenance'' 
prong of section 110(a)(2)(D), the commenter's argument that Cache 
County is ``barely attaining'' the NAAQS is not persuasive. The data 
pointed to by the commenter is not sufficient to support a reasonable 
conclusion that the area warrants evaluation as a maintenance receptor. 
The commenter identified the four highest monitored values for 
PM2.5 at the Cache County monitor for each year from 2005 
through 2010. However, EPA's regulations establish that attainment of 
the PM2.5 NAAQS is determined when the three-year average of 
the 98th percentile value at each monitoring site is less than or equal 
to 65 [mu]g/m\3\. The 98th percentile value for Cache County cannot be 
evaluated by considering only the four highest monitored readings 
during each of the years cited by the commenter. In fact, all of the 
values cited by the commenter would be eliminated from consideration in 
an attainment analysis. EPA concludes that this data is not 
sufficiently persuasive to warrant identifying Cache County as a 
maintenance receptor.
    Although the commenter did not provide a full data set in its 
comments, EPA has analyzed a complete data set for the Cache County 
monitor and determined that the highest three year-average of the 98th 
percentile for the monitor is only 66% of the standard. EPA computed 
the highest 3-year average of the 98th percentile values for each of 
the three-year periods covered by the 2005-2010 period that the 
commenter references. The highest value for any complete three-year 
periods was 42 [mu]g/m\3\, well below 65 [mu]g/m\3\. EPA disagrees with 
the commenter's conclusion that there is a reasonable basis for 
characterizing this area as ``barely attaining'' the NAAQS or one that 
warrants additional evaluation as a maintenance receptor.
    Comment No. 2--The commenter cited a variety of information 
suggesting that receptors in the Denver/North Front Range (Denver/NFR) 
area should also be considered for maintenance purposes under 
110(a)(2)(D)(i) in this action. The commenter points out that as EPA 
itself has stated that ``Data for 2005-2007 and 2006-2008 reflect 
violations of the 8-hour ozone NAAQS at the Rocky Flats North monitor 
(values of {0.085{time}  and 0.086 ppm, respectively).'' The commenter 
also argued that modeling prepared in conjunction with Colorado's 
Denver/NFR attainment demonstration shows that by 2010, the three-year 
design value is only projected to be lowered to 0.084 parts per 
million, barely in compliance with the NAAQS, and that certain portions 
of the Denver/NFR area of Colorado would violate the 1997 ozone NAAQS 
in 2010 at grid cells west of Fort Collins. The commenter referenced 
several documents that are part of the Colorado's Denver/NFR 8-hour 
Ozone Attainment Demonstration in support of its arguments. The 
commenter cited the report's language that indicated that the modeling 
projection of a value above the 1997 8-hour standard to the west of 
Fort Collins is not ``implausible'' explaining, ``[i]n the case of the 
Denver ozone modeling, higher ozone concentrations are estimated west 
of Fort Collins than at the locations of the two monitors in Fort 
Collins on some days and this does not appear to be an error in the 
modeling system''.\25\
---------------------------------------------------------------------------

    \25\ Commenter referenced the Colorado Department of Public 
Health and Environment's ``2010 Ozone Attainment Demonstration 
Modeling for the Denver 8-hour Ozone State Implementation Plan 
Control Strategy'' and the Environ modeling report ``Final 2010 
Ozone Attainment Demonstration Modeling for the Denver 8-hour Ozone 
State Implementation Plan''
---------------------------------------------------------------------------

    The commenter argued that EPA's failure to consider the Denver/NFR 
area as a receptor for evaluating interference with maintenance in this 
action reflects the very problem that the DC Circuit warned could 
result without giving independent meaning to the term ``interfere with 
maintenance.''
    Response--EPA disagrees with the commenter's argument that EPA has 
inappropriately identified the correct monitors for maintenance 
receptors. As discussed in greater detail in the previous response to 
comment, EPA has selected a method that identifies maintenance 
receptors separately from nonattainment receptors and gives an 
independent meaning to the interfere with maintenance prong of section 
110(a)(2)(D)(i). EPA has consistently applied this method to all 
potential receptors in states potentially impacted by Idaho's emissions 
including those in the Denver/NFR area.
    The commenter's argument that EPA did not consistently identify 
maintenance receptors is premised on the same fundamental 
misunderstanding (discussed in the previous response to comment 
addressing the ``interfere with maintenance'' prong) that EPA's 
identification of nonattainment receptors was based on current or past 
NAAQS violations. As explained above, this is not correct. EPA did not 
base its identification of maintenance receptors on an analysis of 
whether air quality at those receptors exceeded the NAAQS in the base 
years. The methodology EPA used to identify maintenance areas takes 
into account historic variability of emissions at specific monitoring 
sites to analyze whether or not monitoring sites projected to be in 
attainment in 2012 will nonetheless remain at risk of slipping into 
nonattainment in that year. The commenter provided a number of modeling 
or monitoring analyses for

[[Page 72715]]

2010 or earlier. As we have addressed in responses elsewhere in this 
notice, EPA continues to believe 2012 is the appropriate year for this 
analysis. Thus, modeling or monitoring data for other years is not 
directly relevant to this rulemaking. Nonetheless, below we address the 
commenter's specific assertions about the modeling.
    The commenter asserts that monitoring data for 2005-07 and 2006-08 
for the Rocky Flats North monitor reflect violations of the 8-hour 
NAAQS and therefore EPA should consider this Rocky Flats North monitor 
as a ``maintenance receptor.'' The commenter further cites to modeling 
prepared in conjunction with Colorado's Denver/NFR attainment 
demonstration to support its assertion that EPA has applied 
inconsistently its definition of interference with maintenance. The 
modeling data referenced by the commenter, however, only identifies 
monitors that, in the commenter's view, are at risk of being in 
nonattainment or having maintenance problems in 2010. The monitoring 
data cited indicates high ozone levels in the past. The underlying 
issue raised is thus substantively the same as that raised in Comment 
No. 3 below which argues that EPA's analysis is faulty because it 
identifies receptors likely to have difficulty maintaining the standard 
in 2012 and not at the present or in the past. EPA's response to 
Comment No. 3 below, illustrates how its approach, based on modeling 
analyses that identify receptors at risk for maintenance in the year 
2012, is appropriate and consistent with the D.C. Circuit decision in 
North Carolina v. EPA.
    EPA's method is based on model projection values that take into 
account multi-year variability in ozone data at specific monitors. For 
identification of maintenance receptors, EPA utilized the monitoring 
data from the 2003-2007 period to calculate 2012 future year modeling 
design value projections. The 2003-07 period includes three Design 
Value (DV) periods (2003-2005, 2004-2006, and 2005-2007). The 2012 
future year DVs were calculated by multiplying a 3-year DV (base year) 
by the ratio of the Future Year average of the daily 8-hour ozone 
maximums around a monitor over the Base Year average of the daily 8-
hour ozone maximums around a monitor. This calculation was performed 
for each of the three 3-year DVs (2003-2005, 2004-2006, and 2005-2007). 
This approach yielded three different projected 2012 design values and 
thus, tests for variability in meteorology. If any of the three 2012 
projections was above the 1997 ozone standard, then the receptor would 
be considered a maintenance receptor. None of the 2012 projections for 
the Denver/NFR area was above the standard so the area was not 
considered a maintenance area. This approach was the same as the 
approach used for every potential receptor evaluated. It is worth 
noting that EPA's analysis included the 2005-2007 data for the Rocky 
Flats monitor (which is one of the highest monitored DVs in recent 
years for this monitor) that the commenter raised as a concern and 
pursuant to its methodology as previously described EPA's analysis 
determined that the Rocky Flats monitor would not be a maintenance 
receptor in 2012.
    Further, EPA disagrees with commenter's conclusion that the 
modeling performed for the Denver/NFR attainment demonstration with the 
2010 model projections establishes that any of the areas identified 
will have maintenance problems for the 1997 8-hour ozone NAAQS. We 
disagree with the commenter's conclusion that the Denver/NFR area 
monitors should be identified as ``maintenance receptors'' in large 
part because he bases his conclusion on projections for 2010 instead of 
2012. This modeling used projections for 2010 not 2012, which as 
explained above and in response to Comment No. 3 below is not the 
correct year for comparison, given the approach EPA has developed for 
determining maintenance receptors. EPA's analysis of maintenance 
receptors, which is based on the approach developed in the Transport 
Rule Proposal to be consistent with the DC Circuit's opinion in North 
Carolina v. EPA and uses projections for 2012, did not identify any 
maintenance receptors in the Denver/NFR area. This conclusion is 
consistent with evidence suggesting emissions are likely to trend 
downward (for example, with two more years of fleet turnover, this 
modeling would likely have projected lower levels of ozone in 2012) and 
preliminary monitoring data for 2010, which indicates that the Denver/
NFR area is meeting the 1997 ozone standard. Further, EPA has reviewed 
Colorado's attainment demonstration for the Denver/NFR area and 
proposed that the combination of the modeling and weight of evidence 
analyses demonstrates that Denver will be in attainment in 
2010.26 27
---------------------------------------------------------------------------

    \26\ EPA's ``Guidance on the Use of Models and Other Analyses 
for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, 
and Regional Haze,'' EPA-454/B-07-002, April 2007.
    \27\ 75 Federal Register 40 CFR part 52 [EPA-R08-OAR-2010-0285; 
FRL-9177-2], Proposed Rule, ``Approval and Promulgation of Air 
Quality Implementation Plans; Colorado; Attainment Demonstration for 
the 1997 8-Hour Ozone Standard, and Approval of Related Revisions''; 
pages 42346-42361.
---------------------------------------------------------------------------

    In addition, the commenter's concern that an area west of Fort 
Collins, might exceed 84 ppb in 2010 is based on exceedance values in 
the Colorado modeling analysis from a special analysis, called the 
Unmonitored Area Analysis (UAA), that is recommended for model grid 
cells that are not analyzed in the monitor based attainment 
demonstration because they are not located near a monitor. EPA does not 
believe that the UAA establishes that this area should be considered a 
maintenance receptor area for the purposes of 110(a)(2)(D)(i).
    First, the UAA analysis is for 2010, which as noted above is not 
the correct analysis year. Second, EPA guidance indicates that NAAQS 
violations in the UAA should be handled on a case by case basis.\28\ 
The guidance stresses that due to the lack of measured data, the 
examination of ozone concentrations as part of the unmonitored area 
analysis is more uncertain than the monitor based attainment test. This 
is true even in situations such as this where, as the commenter points 
out, no known errors were identified by the contractor in the modeling 
analysis. As a result, the UAA results are recommended to be treated as 
a separate test from the monitor based attainment test with less weight 
put on the conclusions of the UAA analysis. EPA's attainment 
demonstration guidance indicates ``[w]hile it is expected that States 
will implement additional emission controls to eliminate predicted 
violations of the monitor based test, the same requirements may not be 
appropriate in unmonitored areas.'' \29\ The guidance recommends that 
it may be appropriate to deploy additional monitors in an area where 
the unmonitored analysis indicates a potential future year violation.
---------------------------------------------------------------------------

    \28\ Id.
    \29\ Id., page 32.
---------------------------------------------------------------------------

    To address the concerns raised by the UAA, Colorado installed an 
additional ozone monitor in the area West of Fort Collins to determine 
whether the model predicted ozone concentrations are, in fact, valid. 
The special purpose monitor, located in Rist Canyon, began operation on 
May 14, 2009. The Rist Canyon monitoring station has collected data for 
two ozone seasons (approximately 16 months) since it began operating 
and the fourth highest daily maximum 8-hour average ozone concentration 
reading is 69 ppb for May through December of

[[Page 72716]]

2009 and 72 ppb for January through August 2010.\30\
---------------------------------------------------------------------------

    \30\ The Rist Canyon monitoring station uses a Federal 
Equivalent Method (FEM) and follows the quality assurance 
requirements of 40 CFR part 58 appendix A. Ozone data collected at 
this monitoring station is eligible for comparison to the ozone 
NAAQS after the monitor has operated for more than 24 months per 40 
CFR 58.30(c). Design values, however, are based on the 3-year 
average of the annual fourth highest daily maximum 8-hour average 
ozone concentration (see 40 CFR part 50, appendix D).
---------------------------------------------------------------------------

    Therefore, EPA does not believe the modeling performed for the 
State of Colorado's Denver/NFR area SIP can support the conclusion that 
this area should be considered a maintenance receptor area for the 
purposes of 110(a)(2)(D)(i). The methodology developed to identify 
maintenance receptors for the purpose of analyzing interference with 
maintenance with respect to the 1997 ozone and PM 2.5 NAAQS 
relies on base period monitoring data to identify monitor locations 
that are projected to have maintenance problems in 2012. The 
methodology does not identify receptors based on modeling data alone. 
While the monitor has not operated long enough to account for 
variability in ozone levels, the newly installed monitor in the 
relevant area is reading well below the standard and this fact further 
confirms that the modeling results and the UAA results do not support 
the conclusion that receptors in the Denver/NFR area should be 
considered maintenance receptors for the purpose of CAA section 
110(2)(D)(i).
    In conclusion, EPA disagrees with the commenter. We have used a 
fully consistent approach in identifying areas that may have difficulty 
in maintaining attainment of the NAAQS. It is these areas that we have 
further evaluated to see if Idaho's emissions would interfere with 
maintenance of the NAAQS.
    Comment No. 3--The commenter also argued that EPA's analysis 
ignores whether emissions from Idaho sources are at present interfering 
with maintenance in other states. The commenter argued that EPA erred 
by considering only whether Idaho emissions will interfere with 
maintenance of the NAAQS in 2012 at monitors that would then be 
considered ``maintenance receptors.'' It argues that this approach is 
inconsistent with the approach taken to determine whether Idaho 
significantly contributes to nonattainment in other states. The 
commenter agreed that ``EPA should ensure that Idaho does not interfere 
with maintenance or contribute significantly to nonattainment in other 
states in the future,'' but argued that ``the agency's duties under 
Section 110(a)(2)(D)(i) apply both in the present and the future.'' In 
short, the commenter argued that EPA's approach is flawed simply 
because EPA evaluated whether or not there is significant contribution 
to nonattainment in other states looking at current data, whereas EPA 
evaluated whether there is interference with maintenance looking at 
future projected data.
    Response: EPA disagrees with the commenter concerning the 
evaluation of significant contribution versus interference with 
maintenance. Section 110(a)(2)(D)(I)(i) of the Clean Air Act requires 
states to submit SIPs within 3 years of promulgation or revision of a 
NAAQS that:

    (D) contain adequate provisions--
    (i) prohibiting * * * any source or other type of emissions 
activity within the state from emitting any air pollutant in amounts 
which will--
    (I) contribute significantly to nonattainment or, interfere with 
maintenance by, any other State with respect to any such national 
primary or secondary ambient air quality standard, or
    (II) interfere with measures required to be included in the 
applicable implementation plan for any other State under part C of 
this subchapter to prevent significant deterioration of air quality 
or to protect visibility.

    In determining the appropriate year to analyze in determining 
whether emissions from Idaho will interfere with maintenance by any 
other State, EPA used an approach upheld by the DC Circuit in North 
Carolina v. EPA. In that case, the court examined EPA's definition of 
``will'' in ``will contribute significantly.'' The placement of the 
word ``will'' at the end of section 110(a)(2)(D)(i) clarifies that it 
applies to all of the provisions that follow--both those in 
110(a)(2)(D)(i)(I) and those in 110(a)(2)(D)(i)(II). Thus the DC 
Circuit's discussion of the meaning of the word ``will'' in ``will 
significantly contribute'' also applies to the meaning of the word 
``will'' in ``will * * * interfere with maintenance.''
    In North Carolina v. EPA, the DC Circuit rejected North Carolina's 
argument that EPA erred in limiting its analysis of downwind areas by 
excluding areas that were currently monitored nonattainment but 
projected to be in attainment at a future date. Like the commenter 
argues here, North Carolina had argued that EPA was obligated to 
analyze the significant contribution of states that were contributing 
to areas of North Carolina that were in nonattainment at the time the 
rule was promulgated, even though those areas were projected to come 
into attainment by the year selected for the future base case analysis. 
In rejecting this argument, the DC Circuit explained that the approach 
used by EPA was identical to the one used previously in the 
NOX SIP Call and that ``because `will' can mean either 
certainty or indicate the future tense,'' EPA's approach was 
reasonable. In other words, the court approved EPA's approach that 
entailed the evaluation of interstate transport impacts at a future 
date in time.
    Contrary to the assertions of the commenter, EPA believes that 
evaluation of interference with maintenance using a future date is the 
most appropriate approach for that requirement. As explained in the 
proposed action, the court decision affecting the CAIR rule required 
EPA to reevaluate its approach to the interfere with maintenance 
requirement of section 110(a)(2)(D) and to develop a new approach to 
give that requirement separate meaning. In doing so, EPA has developed 
an approach that necessarily requires a number of years of data, and an 
analysis that evaluates where there may be difficulties with 
maintaining attainment at a specific point in time, in this instance 
2012. It is reasonable and appropriate for EPA to use, in this 
rulemaking, the current approach to identifying maintenance receptors 
for purposes of section 110(a)(2)(D) that EPA developed to be 
consistent with the direction given to EPA in North Carolina v. EPA.
    Finally, EPA notes that the text of section 110(a)(2)(D)(i) does 
not explicitly specify how to evaluate the existence of, or extent of, 
interstate transport and whether that interstate transport is of 
sufficient magnitude to significantly contribute to nonattainment or 
interfere with maintenance 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's 2006 Guidance explicitly stated our 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.'' 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.'' As discussed above in response to comments regarding the 
``significant contribution to nonattainment'' element, the state's 
submittal and EPA's evaluation of that submittal were consistent with 
the 2006

[[Page 72717]]

Guidance and considered the type of information (such as monitoring 
data in Idaho and downwind states, geographical and meteorological 
information, and technical studies of the nature and sources of 
nonattainment problems in various downwind states) that EPA recommended 
as relevant for evaluating that element. EPA's approach to evaluating 
whether Idaho's emissions significantly contribute to nonattainment in 
another state is consistent with the 2006 Guidance and is a reasonable 
interpretation of section 110(a)(2)(D)(i).
    Just as EPA has used the best available information to make its 
determination regarding Idaho's potential interference with maintenance 
in another state, it has developed and applied a methodology to 
evaluate whether Idaho's emissions potentially contribute significantly 
to nonattainment of the NAAQS in another state that is based upon 
consideration of information that is consistent with the 2006 Guidance, 
past EPA analyses of significant contribution, and reasonably 
appropriate for that purpose. As was explained in the proposed action 
and in this final action's response to comments pertaining to the 
``significant contribution to nonattainment'' analysis above, section 
110(a)(2)(D) is ambiguous with regard to the methods and standards 
applicable to a significant contribution to nonattainment 
determination. Therefore, EPA must interpret those provisions, and the 
Agency's interpretation is subject to judicial deference so long as it 
is a reasonable construction of the statute. Chevron, U.S.A., Inc. v. 
NRDC, Inc., 467 U.S. 837. EPA does not agree with the commenter's 
contention that EPA's approach to the ``interference with maintenance'' 
and ``significant contribution to nonattainment'' prongs of section 
110(a)(2)(D) are flawed. Rather, each analysis is based upon the best 
available information and is a reasonable interpretation and 
application of the statute's requirements.

C. Comment Relating to Section 110(l)

    Comment No. 1--The commenter argued that EPA cannot approve the 
section 110(a)(2)(D) submission from Idaho because the state and EPA 
did not comply with section 110(l). The commenter argues that a section 
110(l) analysis must consider all NAAQS once they are promulgated, and 
that EPA's analysis under section 110(l) was inadequate.
    EPA Response--EPA agrees that a required section 110(l) analysis 
must consider the potential impact of a proposed SIP revision on 
attainment and maintenance of all NAAQS that are in effect and impacted 
by a given SIP revision. However, EPA disagrees that it failed to 
comply with the requirements of section 110(l) or that section 110(l) 
requires disapproval of the SIP submission at issue here.
    Section 110(l) provides in part that: ``[t]he Administrator shall 
not approve a revision of a plan if the revision would interfere with 
any applicable requirement concerning attainment and reasonable further 
progress * * *, or any other applicable requirement of this chapter.'' 
EPA has consistently interpreted Section 110(l) as not requiring a new 
attainment demonstration for every SIP submission. EPA has further 
concluded that preservation of the status quo air quality during the 
time new attainment demonstrations are being prepared will prevent 
interference with the states' obligations to develop timely attainment 
demonstrations. 70 FR 58134, 58199 (October 5, 2005); 70 FR 17029, 
17033 (April 4, 2005); 70 FR 53, 57 (January 3, 2005); 70 FR 28429, 
28431 (May 18, 2005).
    Idaho's submission is the initial submission by the state to 
address for the 1997 8-hour ozone and PM2.5 NAAQS the first 
three elements of section 110(a)(2)(D)(i): (1) Significant contribution 
to nonattainment in any other state, (2) interference with maintenance 
by any other state, and (3) interference with any other state's 
required measures to prevent significant deterioration (PSD) of its air 
quality. This submission does not revise or remove any existing 
emissions limit for any NAAQS, or any other existing substantive SIP 
provisions relevant to the 1997 8-hour ozone and 1997 PM2.5 
NAAQS. Simply put, it does not make any substantive revision that could 
result in any change in emissions. As a result, the submission does not 
relax any existing requirements or alter the status quo air quality. 
Therefore, approval of the Idaho interstate transport SIP will not 
interfere with attainment or maintenance of any NAAQS.
    The commenter did not provide any specific basis for concluding 
that approval of this SIP submission would interfere with attainment or 
maintenance of a NAAQS, or with any other applicable requirement of the 
Clean Air Act. EPA concludes that approval of the submission will not 
make the status quo air quality worse, and is in fact consistent with 
the development of an overall plan capable of meeting the Act's 
attainment requirements. Accordingly, EPA finds that approval of the 
submission is consistent with the requirements of section 110(l).

IV. Final Action

    EPA is approving revisions to the Idaho SIP, submitted on June 28, 
2010, which adequately demonstrate that for the 1997 8-hour ozone and 
1997 PM2.5 NAAQS, air pollutant emissions from sources 
within Idaho do not (1) significantly contribute to nonattainment of 
the NAAQS in any other state or (2) interfere with maintenance of the 
NAAQS by any other state. EPA is also approving the provisions in the 
Idaho SIP relating to interference with any other state's required 
measures to prevent significant deterioration. In its September 13, 
2010, proposal (75 FR 55494), EPA proposed to approve Idaho's SIP as 
adequate for purposes of meeting the requirements of section 
110(a)(2)(D)(i)(II) contingent upon EPA taking final action to approve 
revisions to Idaho's PSD requirements that were consistent with our 
proposed action on these PSD requirements on March 18, 2010. 75 FR 
13058. We received no comments on this proposed contingent approval. 
EPA's Region 10 Regional Administrator signed the final approval of the 
PSD program revisions on November 10, 2010. These approved provisions 
ensure that there will be no interference with any other state's 
required PSD measures because Idaho's SIP meets current CAA 
requirements for PSD.
    In conclusion, EPA is approving revisions to the Idaho SIP, 
submitted on June 28, 2010, because they adequately demonstrate that 
for the 1997 8-hour ozone and 1997 PM2.5 NAAQS, air 
pollutant emissions from sources within Idaho do not (1) significantly 
contribute to nonattainment of the NAAQS in any other state, (2) 
interfere with maintenance of the NAAQS by any other state, and (3) 
interfere with any other state's required measures to prevent 
significant deterioration of its air quality, as required by section 
110(a)(2)(D)(i).
    As noted previously, EPA will address element (4), interference 
with any other state's required measures to protect visibility, in a 
separate action. EPA will also take action on the portion of Idaho's 
SIP that addresses the 2006 PM2.5 NAAQS in a separate 
action.

V. Scope of Action

    Idaho has not demonstrated authority to implement and enforce IDAPA 
Chapter 58 within ``Indian Country'' as

[[Page 72718]]

defined in 18 U.S.C. 1151.\31\ Therefore, EPA proposes that this SIP 
approval not extend to ``Indian Country'' in Idaho. See CAA sections 
110(a)(2)(A) (SIP shall include enforceable emission limits), 
110(a)(2)(E)(i) (State must have adequate authority under State law to 
carry out SIP), and 172(c)(6) (nonattainment SIPs shall include 
enforceable emission limits). This is consistent with EPA's previous 
approval of Idaho's PSD program, in which EPA specifically disapproved 
the program for sources within Indian Reservations in Idaho because the 
State had not shown it had authority to regulate such sources. See 40 
CFR 52.683(b). It is also consistent with EPA's approval of Idaho's 
title V air operating permits program. See 61 FR 64622, 64623 (December 
6, 1996) (interim approval does not extend to Indian Country); 66 FR 
50574, 50575 (October 4, 2001) (full approval does not extend to Indian 
Country).
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    \31\ ``Indian country'' is defined under 18 U.S.C. 1151 as: (1) 
All land within the limits of any Indian reservation under the 
jurisdiction of the United States Government, notwithstanding the 
issuance of any patent, and including rights-of-way running through 
the reservation, (2) all dependent Indian communities within the 
borders of the United States, whether within the original or 
subsequently acquired territory thereof, and whether within or 
without the limits of a State, and (3) all Indian allotments, the 
Indian titles to which have not been extinguished, including rights-
of-way running through the same. Under this definition, EPA treats 
as reservations trust lands validly set aside for the use of a Tribe 
even if the trust lands have not been formally designated as a 
reservation. In Idaho, Indian country includes, but is not limited 
to, the Coeur d'Alene Reservation, the Duck Valley Reservation, the 
Reservation of the Kootenai Tribe, the Fort Hall Indian Reservation, 
and the Nez Perce Reservation as described in the 1863 Nez Perce 
Treaty.
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VI. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a 
SIP submission that complies with the provisions of the Act and 
applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). 
Thus, in reviewing SIP submissions, EPA's role is to approve state 
choices, provided that they meet the criteria of the Clean Air Act. 
Accordingly, this action merely approves state law as meeting Federal 
requirements and does not impose additional requirements beyond those 
imposed by state law. For that reason, this action:
     Is not a ``significant regulatory action'' subject to 
review by the Office of Management and Budget under Executive Order 
12866 (58 FR 51735, October 4, 1993);
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have Federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of Section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the Clean Air Act; and
     Does not provide EPA with the discretionary authority to 
address, as appropriate, disproportionate human health or environmental 
effects, using practicable and legally permissible methods, under 
Executive Order 12898 (59 FR 7629, February 16, 1994).

In addition, this rule does not have tribal implications as specified 
by Executive Order 13175 (65 FR 67249, November 9, 2000), because the 
SIP is not approved to apply in Indian country located in the state, 
and EPA notes that it will not impose substantial direct costs on 
tribal governments or preempt tribal law.
    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the 
Small Business Regulatory Enforcement Fairness Act of 1996, generally 
provides that before a rule may take effect, the agency promulgating 
the rule must submit a rule report, which includes a copy of the rule, 
to each House of the Congress and to the Comptroller General of the 
United States. EPA will submit a report containing this action and 
other required information to the U.S. Senate, the U.S. House of 
Representatives, and the Comptroller General of the United States prior 
to publication of the rule in the Federal Register. A major rule cannot 
take effect until 60 days after it is published in the Federal 
Register. This action is not a ``major rule'' as defined by 5 U.S.C. 
804(2).
    Under section 307(b)(1) of the Clean Air Act, petitions for 
judicial review of this action must be filed in the United States Court 
of Appeals for the appropriate circuit by January 25, 2011. Filing a 
petition for reconsideration by the Administrator of this final rule 
does not affect the finality of this action for the purposes of 
judicial review nor does it extend the time within which a petition for 
judicial review may be filed, and shall not postpone the effectiveness 
of such rule or action. This action may not be challenged later in 
proceedings to enforce its requirements. (See section 307(b)(2).)

List of Subjects in 40 CFR Part 52

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

    Dated: November 10, 2010.
Dennis J. McLerran,
Regional Administrator, Region 10.

0
40 CFR part 52 is amended as follows:

PART 52--[AMENDED]

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

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

Subpart N--Idaho

0
2. The table in Sec.  52.670(e) entitled ``EPA-Approved Nonregulatory 
Provisions and Quasi-Regulatory Measures'' is amended by adding an 
entry to the end to read as follows:

Sec.  52.670  Identification of plan.

* * * * *
    (e) * * *

[[Page 72719]]

                    EPA-Approved Idaho Nonregulatory Provisions and Quasi-Regulatory Measures
----------------------------------------------------------------------------------------------------------------
                                     Applicable         State
     Name of SIP provision          geographic or     submittal       EPA  approval  date          Comments
                                 nonattainment area      date
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
Interstate Transport State       State-wide........   06/28/2010  11/26/2010 [Insert page     For the 1997 8-
 Implementation Plan, May 11,                                      number where the document   hour ozone NAAQS
 2010 (see comments).                                              begins]                     and the 1997
                                                                                               PM[ihel2].[ihel5]
                                                                                               NAAQS. See docket
                                                                                               EPA-R10-OAR-2010-
                                                                                               0669.
----------------------------------------------------------------------------------------------------------------

[FR Doc. 2010-29626 Filed 11-24-10; 8:45 am]
BILLING CODE 6560-50-P